| 1. |
- Asnafi, Nader, 1960-
(författare)
-
On springback of double-curved autobody panels
- 2001
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 43:1, s. 5-37
-
Tidskriftsartikel (refereegranskat)abstract
- The springback of double curved autobody panels is studied theoretically and experimentally. Both steel and aluminum sheets are included in this investigation. The obtained results show that the springback is decreased with increasing binder force, increasing curvature, increasing sheet thickness and decreasing yield strength. This paper comprises also a discussion on the plastic strains and their influence on the springback.
|
|
| 2. |
- Carlsson, S., et al.
(författare)
-
On frictional effects at inelastic contact between spherical bodies
- 2000
-
Ingår i: International Journal of Mechanical Sciences. - 0020-7403 .- 1879-2162. ; 42:1, s. 107-128
-
Tidskriftsartikel (refereegranskat)abstract
- Normal inelastic contact between spherical bodies is examined theoretically and numerically. The analysis is focused on viscoplastic material behaviour. In particular the effect of Coulomb friction is analysed in some detail, both regarding global and field variables. It is shown that the solution to the problem of contact between two deformable spherical bodies is provided by the solution of the fundamental problem of indentation of a viscoplastic half-space by a rigid sphere. The indentation analysis is based on self-similarity and cumulative superposition of intermediate flat die solutions as outlined in detail in a previous study by Storakers et al. (International Journal of Solids and Structures 1997;34:3061-83). The results show that frictional effects, when global properties such as the contact area and the mean contact pressure are at issue, will only be of importance at close to perfectly plastic material behaviour. Even in such circumstances the difference between values given by the solutions for frictionless and for full adhesive contact is no more than approximately 10%. Accordingly, it can be concluded that frictional effects are essentially negligible, when, for example, material characterization of viscoplastic solids by Brinell indentation is of interest. The situation is, however, quite different when field variables are at issue. In this case, stress and strain fields can be substantially influenced by friction with possible implications for features such as crack initiation and crack growth,
|
|
| 3. |
- Green, Jeff, et al.
(författare)
-
A Non-linear Integrated Aeroelasticity Method for the Prediction of Turbine Forced Response with Friction Dampers
- 2001
-
Ingår i: International journal of mechanical sciences. - 0020-7403. ; 43:12, s. 2715-2736
-
Tidskriftsartikel (refereegranskat)abstract
- An integrated aeroelasticity model was described for turbine blade forced response predictions. An iterative procedure was developed to determine the resonance shift under the effects of both unsteady dynamic loading and non-linear friction dampers. The forced response computations were conducted using a multi-bladerow approach to avoid errors associated with linking single bladerow computations since the spacing between the bladerows was relatively small. For the 40 engine-order resonances in torsion and blending modes, frequency shifts of 3.2% and 20.0% were predicted. The predicted frequency shifts and the dynamic behavior of the friction dampers were found to be within the measured range.
|
|
| 4. |
- Grenestedt, Joachim L., et al.
(författare)
-
Influence of cell wall thickness variations on elastic stiffness of closed-cell cellular solids
- 2000
-
Ingår i: International Journal of Mechanical Sciences. - 0020-7403 .- 1879-2162. ; 42:7, s. 1327-1338
-
Tidskriftsartikel (refereegranskat)abstract
- The stiffness of closed-cell low-density cellular solids, or solid foams, is affected by "imperfections" such as non-uniform cell shape and size, wavy distortions of cell walls, variations in cell wall thickness, etc. The present paper focuses on the influence of non-uniform cell wall thickness on stiffness. Calculations are performed on one model with different degrees of thickness variations. The model used is the flat-faced Kelvin structure, which consists of 14-sided polyhedra in a bcc arrangement. The results indicate that the stiffness of closed-cell cellular solids is not very sensitive to thickness variations. (C) 2000 Elsevier Science Ltd. All rights reserved.
|
|
| 5. |
- Larsson, Per-Lennart
(författare)
-
Investigation of sharp contact at rigid-plastic conditions
- 2001
-
Ingår i: International Journal of Mechanical Sciences. - 0020-7403 .- 1879-2162. ; 43:4, s. 895-920
-
Tidskriftsartikel (refereegranskat)abstract
- Sharp contact problems are examined theoretically and numerically. The analysis is focused on elastic-plastic material behaviour and in particular the case when the local plastic zone arising at contact is so large that elastic effects on the mean contact pressure will be small or negligible. It is shown that, save for the particular case of a rigid-plastic power-law material, at such conditions, there is no single representative value on the uniaxial stress-strain curve that can be used in order to evaluate the global parameters at contact. However, the present numerical results indicate that good accuracy predictions for the mean contact pressure can be achieved when this variable is described by two parameters corresponding to the stress levels at, approximately, 2 and 35% plastic strain. Regarding the size of the contact area, it is shown that this quantity is very sensitive to elastic effects and any general correlation with material properties is complicated at best. The numerical analysis is performed by using the finite element method and the theoretical as well as the numerical results are compared with relevant experimental ones taken from the literature. From a practical point of view, the presented results are directly applicable to material characterization or measurements of residual mechanical fields by sharp indentation tests, but also for situations such as contact in gears or in electronic devices.
|
|
| 6. |
- Tan, Z., et al.
(författare)
-
On analysis and measurement of residual stresses in the bending of sheet metals
- 1994
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 36:5, s. 483-491
-
Tidskriftsartikel (refereegranskat)abstract
- A new method for evaluating distribution of residual stresses in bent sheet metals is presented. Due to the non-uniform distribution of strain and stress across thickness, springback on unloading induces residual stress in a bent specimen. The authors have formulated the problem and shown that the springback and residual stresses can be expressed as a function of geometric parameters and material properties of sheet metals, e.g. bending curvature, thickness, Young's modulus, work-hardening index, etc. The layer-removing method was used to determine the residual stresses in the study. By simulating the layer-removing process, analytical measurement of the residual stress was made. The analytical results were compared with the experimental data measured, and a good agreement was found.
|
|
| 7. |
- Bagheri, R., et al.
(författare)
-
Analysis of cracked piezoelectric layer with imperfect non-homogeneous orthotropic coating
- 2015
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 93, s. 93-101
-
Tidskriftsartikel (refereegranskat)abstract
- Abstract The fracture problem for a medium composed of a cracked piezoelectric strip with functionally graded orthotropic coating is studied. The layer is subjected to anti-plane mechanical and in-plane electrical loading. In this paper, we first address, the problem of a screw dislocation located in a substrate which is imperfectly bonded to the coating. Then, in order to model the cracked piezoelectric layer, by means of the dislocation solution, we construct integral equations for the layer, in which the unknown variables are dislocation densities. These unknowns are determined through satisfaction of the boundary conditions on the crack faces. By use of the dislocation densities, the field intensity factors are determined. Several examples are presented to demonstrate the applicability of the proposed solution. ", keywords = Piezoelectric strip; Functionally graded layer; Imperfect bonding; Multiple cracks; Stress intensity factors, isbn = 0020-7403, doi=https://doi.org/10.1016/j.ijmecsci.2014.11.025
|
|
| 8. |
- Afzal, Mohammad, 1987-, et al.
(författare)
-
Numerical analysis of multiple friction contacts in bladed disks
-
Ingår i: International Journal of Mechanical Sciences. - 0020-7403 .- 1879-2162.
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The damping potential of multiple friction contacts in a bladed disk, tip shroud and strip damper is investigated, showing that friction damping effectiveness can be potentially increased by using multiple friction contact interfaces. Friction damping depends on many parameters such as rotational speed, engine excitation order and mode family and therefore it is not possible to damp all the critical resonances using a single friction contact interface. For example, a strip damper is more effective for the low nodal diameters, where blade/disk coupling is strong. The equations of motion of the bladed disk with multiple friction contacts are derived in the frequency domain for a cyclic structure with rotating excitations and a highly accurate method is used to generate the frequency response function (FRF) matrix. Furthermore, a finite element contact analysis is performed to compute the normal contact load and the contact area of the shroud interface at operating rotational speed. The multiharmonic balance method is employed in combination with the alternate frequency time domain method to find the approximate steady state periodic solution. A low-pressure turbine bladed disk is considered and the effect of the engine excitation level, strip mass, thickness and the accuracy of FRF matrix on the nonlinear response curve are investigated in detail.
|
|
| 9. |
- Afzal, Mohammad, et al.
(författare)
-
Numerical analysis of multiple friction contacts in bladed disks
- 2018
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 137, s. 224-237
-
Tidskriftsartikel (refereegranskat)abstract
- The damping potential of multiple friction contacts in a bladed disk is investigated. Friction contacts at tip shrouds and strip dampers are considered. It is shown that friction damping effectiveness can be potentially increased by using multiple friction contact interfaces. Friction damping depends on many parameters such as rotational speed, engine excitation order and mode family and therefore it is not possible to damp all the critical resonances using a single kind of friction contact interface. For example, a strip damper is more effective for the low nodal diameters, where blade/disk coupling is strong. The equations of motion of the bladed disk with multiple friction contacts are derived in the frequency domain for a cyclic structure with rotating excitations. A highly accurate method is used to generate the frequency response function (FRF) matrix. Furthermore, a finite element contact analysis is performed to compute the normal contact load and the contact area of the shroud interface at operating rotational speed. The multiharmonic balance method is employed in combination with the alternate frequency time domain method to find the steady state periodic solution. A low-pressure turbine bladed disk is considered and the effect of the engine excitation level, strip mass, thickness and the accuracy of FRF matrix on the nonlinear response curve are investigated in detail.
|
|
| 10. |
- Ashwear, Nasseradeen, et al.
(författare)
-
Influence of Temperature on the Vibration Properties of Tensegrity Structures
- 2015
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 99, s. 237-250
-
Tidskriftsartikel (refereegranskat)abstract
- Vibration health monitoring methods use the sensitivity of the natural frequencies to structural damage. Natural frequencies are sensitive to damage, but are also affected by environmental conditions like temperature changes. It is important to be able to distinguish between the effects of these different factors when using the vibration properties as a monitoring tool. This paper discusses the impact of damage and environment temperature changes on the natural frequencies of tensegrity ("tensile-integrity") structures, in particular noting that component bending is a prominent vibration mode, which motivates a use of non-linear beam elements with axial-bending coupling. The model considers not only thermal expansion effects, but also the change of the elastic modulus with temperature. Changes in natural frequencies produced by environment temperature changes are shown to be similar to the ones produced by damage. The geometry of tensegrity structures, the support conditions and the materials are found to be important factors. The sensitivity of the natural frequency to temperature changes is found to be dependent on pre-stress level.
|
|
| 11. |
- Baghous, Nareg, et al.
(författare)
-
Generalized yield surface for sheet-based triply periodic minimal surface lattices
- 2023
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 252, s. 108370-
-
Tidskriftsartikel (refereegranskat)abstract
- Triply periodic minimal surfaces (TPMS), which are a class of architected cellular materials, have attracted significant attention lately, due to their prevailing mechanical, electrical and chemical properties, to name a few, and due to the advancements in additive manufacturing technologies that make it possible to print such mate-rials. However, simulating the elastic-plastic mechanical behavior of structural systems (e.g., beams, plates, cores of sandwich panels, structural systems with various levels of geometric complexity) that are latticed with thousands of TPMS lattices are computationally expensive to model explicitly, and hence the need to develop accurate yield surfaces in order to capture their plastic behavior in a homogenized approach. In this work, a generalized initial yield criterion is proposed for sheet-based TPMS lattices, which incorporates the Lode parameter L. The initial yielding of five different sheet-based TPMS lattices are investigated in five different loading conditions. These lattices are Schoen's I-WP (IWP-s), Gyroid (GYR-s), Diamond (DIA-s), F-RD (FRD-s) and Primitive (PRIM-s). The proposed yield criterion accurately predicts the initial yielding of all these lattices in all the loading conditions considered, outperforming other yield criteria currently proposed in literature.
|
|
| 12. |
|
|
| 13. |
- Baravdish, George, 1964-, et al.
(författare)
-
An iterative method for the Cauchy problem for second-order elliptic equations
- 2018
-
Ingår i: International Journal of Mechanical Sciences. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0020-7403 .- 1879-2162. ; 142, s. 216-223
-
Tidskriftsartikel (refereegranskat)abstract
- The problem of reconstructing the solution to a second-order elliptic equation in a doubly-connected domain from knowledge of the solution and its normal derivative on the outer part of the boundary of the solution domain, that is from Cauchy data, is considered. An iterative method is given to generate a stable numerical approximation to this inverse ill-posed problem. The procedure is physically feasible in that boundary data is updated with data of the same type in the iterations, meaning that Dirichlet values is updated with Dirichlet values from the previous step and Neumann values by Neumann data. Proof of convergence and stability are given by showing that the proposed method is an extension of the Landweber method for an operator equation reformulation of the Cauchy problem. Connection with the alternating method is discussed. Numerical examples are included confirming the feasibility of the suggested approach.
|
|
| 14. |
- Barsoum, I., et al.
(författare)
-
The effect of stress state on ductility in the moderate stress triaxiality regime of medium and high strength steels
- 2012
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 65:1, s. 203-212
-
Tidskriftsartikel (refereegranskat)abstract
- Experiments on double notched tube specimens subjected to tension and torsion were conducted by Barsoum and Faleskog (2007) [8,9]. In this study a complementary experimental investigation was conducted on tensile round circumferentially notched bar specimens. The results from the current study were compared with the results from the double circumferentially notched tube specimens with stress triaxiality larger than 0.7 in order to asses the influence of the Lode parameter on ductility in the moderate stress triaxiality regime. The effective plastic strain, the stress triaxiality T and the Lode parameter L were determined at the center of the notch up to the point of onset of failure by means of finite element. The influence of the Lode parameter on the failure strain was significant for the high strength and low hardening material, whereas for the medium strength and high hardening material the influence of the Lode parameter was less distinguished. The experimental results were then analyzed with the micromechanical model proposed by Barsoum and Faleskog (2011) [15], which is based on the assumption that ductile failure is a consequence of that plastic deformation localizes into a band. The band consists of a square array of equally sized cells, with a spherical void located in the center of each cell, which allows for studying a single 3D unit cell with fully periodic boundary conditions. The unit cell is subjected to a proportional loading such that it resembles the stress state, in terms of T and L, from the experiments. The micromechanical model captures the experimental trend and the influence of L on ductility very well. It is found that the Lode parameter sensitivity increases by the combination of increase in the yield strength and decrease in strain hardening. The fractographical analysis reveals that this Lode parameter sensitivity is associated with the failure characteristics of the material.
|
|
| 15. |
- Blom, Peter, et al.
(författare)
-
The frequency, amplitude and magnetic field dependent torsional stiffness of a magneto-sensitive rubber bushing
- 2011
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 60:1, s. 54-58
-
Tidskriftsartikel (refereegranskat)abstract
- A dynamic torsional stiffness model of a magneto-sensitive circular annular rubber bushing is presented where influences of frequency, amplitude and magnetic field dependence are included. This is achieved by employing a newly developed non-linear magneto-sensitive audio frequency constitutive equation in an engineering formula for the torsional stiffness of a rubber bushing. The engineering stiffness formula predicts the frequency and amplitude dependent stiffness in a simple way, based on geometric dimensions and the shear modulus. The shear modulus is provided by the rubber model. The results from these calculations predict and clearly display the possibility of controlling over a large frequency range, through the application of a magnetic field, the magneto-sensitive rubber bushing stiffness.
|
|
| 16. |
- Ceccato, Chiara, Professor, et al.
(författare)
-
Investigation of rolling contact between metal and rubber-covered cylinders governing the paper compaction process
- 2019
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 163
-
Tidskriftsartikel (refereegranskat)abstract
- With the goal of partial or complete replacement of plastic components with paper-based products, 3D paper structures have seen a growing interest in industrial applications: from packaging to more complex daily life objects. However, the extensibility of paper has become a key issue within this context and is the main factor determining the formability of these products and determining the depth of the achievable shapes. The most effective way to increase paper's stretch potential is by subjecting the moist paper web to a compaction process, which can be achieved through an extensible unit that is located in the drying section of a paper machine, where the network experiences in-plane compression in the machine direction (MD), under out-of-plane lateral constraints. The objective of this work is to clarify the mechanisms governing the compression process and to evaluate the influence of various parameters on the final material properties to optimize the industrial production of extensible paper. The system operation has been simulated realistically and shows that paper experiences a compressive state passing through the nip, with plastic strains in MD direction being of the same order of the applied speed difference, which was expected experimentally in optimal conditions of compaction. Starting from an initial reference case, a sensitivity study has been performed to identify and address the following factors that may affect the compression state: (a) friction coefficients; (b) indentation level; (c) speed difference; and (d) rubber properties. The analysis of the numerical results gives an insight into the mechanisms governing the compaction operations and allows a better comprehension of the features controlling the process outcome.
|
|
| 17. |
- Chen, Jian, et al.
(författare)
-
A coupled DEM-SPH model for moisture migration in unsaturated granular material under oscillation
- 2020
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 169
-
Tidskriftsartikel (refereegranskat)abstract
- Granular materials, such as mineral products, soil and chemical fertilizer, normally contain unsaturated free moisture. This unsaturated moisture could migrate in the granular material and its processing, resulting in handling and safety concerns due to a change in the material properties. In this work, a method of coupling the Discrete Element Method (DEM) and the Smoothed Particle Hydrodynamics (SPH) was proposed to investigate moisture migration in unsaturated granular materials under oscillation. The particles and water were simulated through DEM and SPH, respectively and a python coupling framework was programmed to perform the exchange of particle-fluid interaction forces. Subsequently, experiments with plastic pellets and a coal sample were used to calibrate the models, with DEM calibrated by an angle of repose experiment and draining experiments calibrating the coupled model. Finally, the coupled model was validated by comparing the results to those of experiments involving moisture migration under oscillation. It was found that, compared to measurements, the coupled SPH-DEM model predicted the same moisture migration trend and also provided good agreement for the prediction of the mass of drained water.
|
|
| 18. |
- Dou, W., et al.
(författare)
-
A boundary-condition-transfer method for shell-to-solid submodeling and its application in high-speed trains
- 2020
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 177
-
Tidskriftsartikel (refereegranskat)abstract
- The boundary-condition-transfer method for a shell-to-solid submodeling is fundamental for analyzing local or weak regions of a complex structure accurately. In this paper, a novel method is presented for transferring displacement boundaries based on hypothetical nodes. By considering the invariable volume of an element as a constraint, the interpolation through conventional methods using 6-degrees-of-freedom (DOFs) nodal translations and rotations is converted into a 3-DOF translational interpolation at the cut boundary of a submodel. To demonstrate this method, a radial basis function (RBF) was employed for interpolation. For validating the accuracy of the proposed method, a square plate with a hole under tensile and bending load were designed as examples. By considering global and local errors, three typical kernel functions with respect to mesh density ratios were analyzed to fix the optimal parameter in RBF. The examples showed that the proposed method significantly improves the accuracy in shell-to-solid submodeling problems compared to conventional solutions such as ANSYS. For structural analysis of a high-speed train car body under combined mechanical and aerodynamic loads, the submodeling method was implemented on the solid-element-based local model with a welding seam, with which a more detailed stress state was obtained compared with that computed by shell elements. The accurate and reliable results illustrate that the proposed method is the core for the global–local analysis of large complex structures, which also is used for the design and evaluation of the mechanical properties.
|
|
| 19. |
- Dou, Weiyuan, et al.
(författare)
-
A feature points-based method for data transfer in fluid-structure interactions
- 2022
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 234
-
Tidskriftsartikel (refereegranskat)abstract
- For numerical simulations of fluid-structure interaction (FSI) problems, discretized meshes of different compu-tational domains do not have to match at the common interface. Data transfer via the interface is therefore significantly affecting the accuracy of FSI. Implementing data transfer between such pairwise non-matching meshes is challenging, as it is highly desirable to yield numerical accuracy using methods such as interpola-tion or projection. To further improve the data transfer accuracy for mesh-based approaches, this study proposes a feature points-based combined interpolation method by means of Simpson's rule, with which an appropriate weighting coefficient is determined. Moreover, radial basis function (RBF) is employed to perform the inter-polation of scattered data points. The proposed method is validated by a series of examples involving various non-matching mesh configurations in FSI problems. The numerical findings indicate that this method can further improve data transfer accuracy. Even for a critical case with large mesh ratio at the interface it can provide satisfying results.
|
|
| 20. |
- Eggertsen, Per-Anders, 1981, et al.
(författare)
-
On constitutive modeling for springback analysis
- 2010
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 52:6, s. 804-818
-
Tidskriftsartikel (refereegranskat)abstract
- The springback phenomenon that occurs in thin metal sheets after forming is mainly a stress driven problem, and the magnitude is roughly proportional to the ratio between residual stresses and Young's modulus. An accurate prediction of residual stresses puts, in turn, high demands on the material modeling during the forming simulation. A phenomenological plasticity model is made up of several ingredients, such as a yield condition, a plastic hardening curve, a hardening law, and a model for the degradation of elastic stiffness due to plastic straining. The authors of this paper have recently, [1], showed the importance of a correct modeling of a cyclic stress-strain behavior via a phenomenological hardening law, in order to obtain an accurate stress prediction. The main purposes of the present study are to study the influence of two other constitutive ingredients: the yield criterion and the material behavior during unloading. Three different yield criteria of different complexity are evaluated in the present investigation: the Hill'48 criterion, the Barlat-Lian Y1d89 criterion, and the 8-parameter criterion by Banabic/Aretz/Barlat. The material behavior during unloading is evaluated by loading/unloading tension tests, where the material is unloaded/reloaded at specified plastic strain levels. The slope of the unloading curve is measured and a relation between the "unloading modulus" and the plastic stain is established. In the current study, results for four different materials are accounted for. The springback of a simple U-bend is calculated for all the materials in the rolling-, transverse- and diagonal directions. From the results of these simulations, some conclusions regarding constitutive modeling for springback simulations are drawn. (C) 2010 Elsevier Ltd. All rights reserved.
|
|
| 21. |
|
|
| 22. |
- Ejeh, Chukwugozie J., et al.
(författare)
-
Flexural properties of functionally graded additively manufactured AlSi10Mg TPMS latticed-beams
- 2022
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 223, s. 107293-
-
Tidskriftsartikel (refereegranskat)abstract
- Due to the recent boom in digital design for additive manufacturing and 3D printing, there has been a significantly growing interest in latticed structures for light design and improved mechanical properties. However, the focus in the literature has mostly been on compressive mechanical properties of uniformly latticed structures with little emphasis on flexural properties of latticed-beams that are functionally graded and hybridized with different lattice topologies. Therefore, this paper aims to explore the effect of lattice relative density gradation and hybridization on the specific flexural properties of prominent sheet-based triply periodic minimal surfaces (TPMS) cellular four-point loaded beams. First, the effective elastic properties of the cubic porous topologies are evaluated computationally to converge to certain sheet-based TPMS cellular structures capable of providing high flexural properties. Schwartz primitive (P) revealed high stiffness to shear loading, meanwhile, the F-Rhombic Dodecahedron (FRD) showed better resistance to uniaxial loading, and the Diamond (D) showed well-combined uniaxial and shear moduli. The selected four-point bend (4 PB) latticed-beams are functionally graded following a bilinear pattern and hybridized through the span of their length inspired by the shearing force and bending moment diagrams arising in the 4 PB beam, in view of the effective elastic properties of the TPMS topologies. The additively manufactured AlSi10Mg uniform, functionally-graded, and hybridized latticed-beams are tested in four-point bending and the results are compared with the finite element results. Both the experimental and numerical outcomes show good agreement within the elastic-plastic regime. From experimental results, it is found that functional grading and hybridization can considerably enhance the specific flexural modulus of sheetbased TPMS latticed-beams. Also, relative density gradation within the four-point bend specimens proved very essential in deflecting crack growth thereby retarding the final failure, meanwhile hybridization is conveyed to mitigate shear-band failure. Combination of functional gradation and hybridization on the latticed-beams resulted in a significant increase in the specific flexural stiffness. Therefore, this study provides guidelines on how to enhance the flexural properties of lightweight beams through lattice functional grading and hybridization.
|
|
| 23. |
- Ejeh, Chukwugozie J., et al.
(författare)
-
Impact behavior of periodic, stochastic, and anisotropic minimal surface-lattice sandwich structures
- 2024
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier Ltd. - 0020-7403 .- 1879-2162. ; 276
-
Tidskriftsartikel (refereegranskat)abstract
- Recent advancements in 3D printing technologies have made it possible to fabricate intricate lattice architectures with high precision. These lattices can now be utilized to design lightweight sandwich structures that serve multiple functions. To enhance the impact loading performance of these structures, it is crucial to understand how the lattice's topological properties, particularly those with minimal surface attributes like periodic or stochastic Primitive and Gyroid triply periodic minimal surfaces (TPMS) and spinodal-like stochastic cellular materials, associate with the mechanical properties of sandwich structures while keeping the skin thickness fixed. Thus, this paper explores the low-velocity impact behavior of various sheet/shell-based minimal surface-latticed cores of sandwich structures with woven composite skins. The elasto-plastic-damage numerical simulations consider lattice core periodicity, randomness, and anisotropy while keeping the relative density constant. Core lattice randomness and anisotropy are designed using the Gaussian Random Field (GRF) method for spinodal-based stochastic cellular materials and stochastic TPMS. The simulation results showed that the periodic Primitive-lattice core exhibits high out-of-plane shearing strength, enabling the sandwich structure to demonstrate the highest perforation limit. GRF spinodal-based core achieved the highest peak load due to its anisotropic mechanical properties. However, the post-yielding bending of the lattice sheet limited its ability to resist perforation, and absorb and dissipated energy. Interestingly, the stochastic Gyroid TPMS topology, with its inherent densely-distributed microstructure, showed high sensitivity to loading rate, resulting in enhanced energy absorption and dissipation of the sandwich structure. These findings offer valuable insights for optimizing multifunctional sandwich structures with superior impact performance and their design for additive manufacturing.
|
|
| 24. |
- Fadaee, M., et al.
(författare)
-
Free vibration analysis of Lévy-type functionally graded spherical shell panel using a new exact closed-form solution
- 2013
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 77, s. 227-238
-
Tidskriftsartikel (refereegranskat)abstract
- An exact closed-form analysis for describing the natural vibrations of a FG moderately thick spherical shell panel is developed. The strain-displacement relations of Donnell and Sanders theories are used to obtain the exact solutions. The shell has two opposite edges simply supported (i.e., Lévy-type). The material properties change continuously through the thickness of the shell, which can vary according to a power-law distribution of the volume fraction of the constituents. The new auxiliary and potential functions are employed to exactly decouple the governing equations of the vibrated spherical shell panel, leading to the exact closed-form frequency equation in the form of determinant. The accuracy and validity of the solutions are established with the aid of a 3D finite element analysis as well as by comparing the results with the data reported in the literature. The effects of various stretching-bending couplings on the frequency parameters are discussed.
|
|
| 25. |
- Ghassemali, Ehsan, et al.
(författare)
-
Optimization of axisymmetric open-die micro-forging/extrusion processes: An upper bound approach
- 2013
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 71, s. 58-67
-
Tidskriftsartikel (refereegranskat)abstract
- There is a trend towards component miniaturization and strong drive towards cost effective and sustainable metal forming techniques of miniaturized components. This paper presents an upper bound solution for the optimization of open-die forging/extrusion processes in the forming of micro-pins from a sheet metal. Using such an analytical modeling approach, the critical blank thickness, the resulting final part geometry, together with the required forming load were predicted based on the location of the neutral plane under the punch during the process. Based on the phenomenological findings of the process, the geometry size factor, x, was introduced explaining its relative importance to the model. Experimental results obtained from C11000 copper samples using a progressive microforming process was found to agree well with the results predicted by the model. The results were also validated with other results reported before from a similar process.
|
|
| 26. |
- Girhammar, Ulf Arne
(författare)
-
A simplified analysis method for composite beams with interlayer slip
- 2009
-
Ingår i: International Journal of Mechanical Sciences. - : Pergamon Press. - 0020-7403 .- 1879-2162. ; 51:7, s. 515-530
-
Tidskriftsartikel (refereegranskat)abstract
- A simplified static procedure is proposed for analysing and designing composite beams with interlayer slip. The method is parallel to the Eurocode 5 method, but it is general in nature and can be applied to arbitrary boundary and loading conditions. In contrast with Eurocode 5, a general and correct way of choosing the effective beam length of the problem is given by the present procedure, which is that the effective beam length equals the buckling length that is found in the corresponding column buckling problem. The procedure predicts the deflections and internal actions and stresses, in principle by replacing the fully composite bending stiffness (EI(infinity)) with the effective (partially) composite bending stiffness (EI(eff)) in the expressions for these quantities in the corresponding fully composite beam. This effective bending stiffness depends on two non-dimensional parameters: the composite action parameter (shear connection stiffness) and the relative bending stiffness parameter. The method is applied to a number of simple practical cases and the results obtained have been compared with the exact values. The applicability of the simplified analysis procedure was found to be very good, except for interlayer shear stresses. The error in the Eurocode 5 procedure, as compared with the method proposed in this paper, can in some cases be up to almost 30% depending on the boundary conditions.
|
|
| 27. |
- Girhammar, Ulf Arne
(författare)
-
Composite beam-columns with interlayer slip : approximate analysis
- 2008
-
Ingår i: International Journal of Mechanical Sciences. - Oxford : Pergamon Press. - 0020-7403 .- 1879-2162. ; 50:12, s. 1636-1649
-
Tidskriftsartikel (refereegranskat)abstract
- An approximate second order analysis procedure for composite beam-columns with interlayer slip subjected to transverse loading and axial compressive loads is developed. The magnification factors to be applied to the first order solutions in order to estimate the deflections and internal forces obtained by the second order analysis approach are presented. The method of applying magnification factors to internal axial forces is discussed. The approximate second order analysis procedure is developed for the four Euler cases with various transverse load conditions. The procedure is applied to and the accuracy is illustrated for simply supported partially beam-columns of steel and concrete, and timber and concrete with different bending stiffness and interlayer slip properties. The deflections and internal forces obtained by the approximate method compared extremely well, except for slip forces in case of very flexible shear connectors, with those obtained by the more rigorous second order analysis approach for different composite action (partial interaction) parameters (shear connector stiffness values). The study also shows that the magnification factor associated with the deflections can be utilized to estimate also the internal actions, except shear forces in case of very flexible shear connectors, in the second order case with minimal error for simply supported beam-columns. Thus. for members with shear connector stiffness of structural significance the proposed approximate method can be used in general for simply supported beam-columns. For other boundary and loading conditions, the approximate method needs to be re-evaluated. The approach of using one magnification factor greatly simplifies the analysis task for those components.
|
|
| 28. |
|
|
| 29. |
- Girhammar, Ulf Arne, et al.
(författare)
-
Exact static analysis of partially composite beams and beam-columns
- 2007
-
Ingår i: International Journal of Mechanical Sciences. - Oxford : Pergamon Press. - 0020-7403 .- 1879-2162. ; 49:2, s. 239-255
-
Tidskriftsartikel (refereegranskat)abstract
- The ordinary differential equations and general solutions for the deflection and internal actions and, especially, the pertaining consistent boundary conditions for partially composite Euler-Bernoulli beams and beam-columns are presented. Static loading conditions, including transverse and axial loading and first- and second-order analyses are considered. The theoretical procedure is applicable to general loading and boundary conditions for uniform composite beams and beam-columns with interlayer slip. Further, the exact closed form characteristic equations and their associated exact buckling length coefficients for composite Columns with interlayer slip are derived for the four Euler boundary conditions. It is shown that these coefficients are the same as those for ordinary fully composite (solid) columns, except for the Euler clamped-pinned case. For the clamped-pinned case, the difference between the exact buckling length coefficient and the corresponding value for solid Columns is less than 1.8%, depending oil the so-called composite action parameter and relative bending stiffness parameter. Correspondingly, the maximum deviation between the exact and approximate buckling load is at most 2.5%. These small differences can in most practical cases be neglected. Also, the maximum theoretical range for the relative bending stiffness for partially composite beams and beam-columns is derived. An effective bending stiffness, valuable in the determination of the critical buckling load for partially composite members, is derived. This effective bending stiffness is also Suitable for analysing approximate deflections and internal actions or stresses in composite beams with flexible shear connection. The beam-column analysis is applied to a specific case. The difference in the approaches to the first- and second-order analysis is illustrated and the results clearly show the magnification in the actions and displacements due to the second-order effect. The magnification of the internal axial forces is different from magnifications obtained for the other internal actions, since only that portion of an internal axial force that is induced by bending is magnified by the second-order effect.
|
|
| 30. |
- Gustavsson, Rolf K., et al.
(författare)
-
Evaluation of impact dynamics and contact forces in a hydropower rotor due to variations in damping and lateral fluid forces
- 2009
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 51:9-10, s. 653-661
-
Tidskriftsartikel (refereegranskat)abstract
- Damages due to contact between the runner and the discharge ring have been observed in several hydroelectric power units. The damage can cause high repair costs of the runner and the discharge ring as well as considerable production losses.In this paper a rotor model of a 45 MW hydropower unit is used for the analysis of the rotor dynamical phenomena occurring due to contact between the runner and the discharge ring for different grade of lateral force on the turbine and bearing damping. The rotor model consists of a generator rotor and a turbine, which is connected to an elastic shaft supported by three isotropic bearings. The discrete representation of rotor model consist of 32 degrees of freedom, to increase the speed of the analysis the size of the model has been reduced with the IRS method to a system with 8 degrees of freedom.Results are presented in bifurcation diagrams, maximum contact force, Poincaré map and phase portrait. Simulations indicate that the contact forces between the turbine and the discharge ring are large, with considerable risks for serious damage as a consequence. The analysis shows that the risk for contact and damage are large for relatively small lateral turbine loads when the gap between the turbine and discharge ring is small and the contact stiffness is high.
|
|
| 31. |
|
|
| 32. |
- Hallberg, Håkan
(författare)
-
Influence of process parameters on grain refinement in AA1050 aluminum during cold rolling
- 2013
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 1879-2162 .- 0020-7403. ; 66, s. 260-272
-
Tidskriftsartikel (refereegranskat)abstract
- The microstructure evolution during cold rolling of commercial purity AA1050 aluminum is investigated through numerical simulations. A finite strain elasto-viscoplastic constitutive model is employed, where the dislocation density and average grain size are taken as variables characterizing the deformed microstructure. Grain size evolution due to dynamic recrystallization is considered and the microstructure quantities are allowed to influence the macroscopic material behavior in terms of the flow stress and deformation-rate dependence. The effects of such process parameters as rolling friction, thickness reduction in each rolling pass and amount of rolling asymmetry are discussed. The results indicate that grain refinement due to dynamic recrystallization is most significantly affected by the amount of thickness reduction in each pass and the level of rolling friction and to a lesser extent by the asymmetry of the rolling process. An increasing degree of asymmetry will, however, reduce the variations in grain size through the sheet thickness and leave the material more homogeneously recrystallized.
|
|
| 33. |
- Hosseini-Hashemi, S., et al.
(författare)
-
A new exact analytical approach for free vibration of ReissnerMindlin functionally graded rectangular plates
- 2011
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 53:1, s. 11-22
-
Tidskriftsartikel (refereegranskat)abstract
- An exact closed-form procedure is presented for free vibration analysis of moderately thick rectangular plates having two opposite edges simply supported (i.e. Lvy-type rectangular plates) based on the ReissnerMindlin plate theory. The material properties change continuously through the thickness of the plate, which can vary according to a power law distribution of the volume fraction of the constituents. By introducing some new potential and auxiliary functions, the displacement fields are analytically obtained for this plate configuration. Several comparison studies with analytical and numerical techniques reported in literature are carried out to establish the high accuracy and reliability of the solutions. Comprehensive benchmark results for natural frequencies of the functionally graded (FG) rectangular plates with six different combinations of boundary conditions (i.e. SSSSSSSCSCSCSCSFSSSFSFSF) are tabulated in dimensionless form for various values of aspect ratios, thickness to length ratios and the power law index. Due to the inherent features of the present exact closed-form solution, the present results will be a useful benchmark for evaluating the accuracy of other analytical and numerical methods, which will be developed by researchers in the future.
|
|
| 34. |
- Khurshid, Mansoor, 1986-, et al.
(författare)
-
Residual stress state induced by high frequency mechanical impact treatment in different steel grades – Numerical and experimental study
- 2017
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 123, s. 34-42
-
Tidskriftsartikel (refereegranskat)abstract
- High frequency mechanical impact treatment is observed to increase the fatigue strength of welded joints. This technique induces compressive residual stresses, increases the local hardness, and reduces the stress concentration by modifying the weld toe radius. The goal of this study was to investigate residual stresses induced by ultrasonic impact treatment in S355, S700MC, and S960 grades steel experimentally and numerically. Plate specimens were manufactured and treated with different treatment intensities i.e. vibration amplitudes of the Sonotrode. The indentation depths were measured by the aid of a laser scanner and residual stresses using X-ray diffraction technique. The effect of steel grade and treatment intensity on the induced compressive residual stress state was firstly studied experimentally. In addition, displacement controlled simulations were carried out to estimate the local residual stress condition considering the effect of different material models. Both the numerically estimated and experimentally measured residual stresses were qualitatively in good agreement. Residual stress state in S355 and S700MC can be estimated well using combined strain rate dependent material model. No significant effect of the treatment intensity is observed on the indentation depth and residual stress state for S355 grade steel. The indentation depth decreases with the increase in the yield strength of the steel.
|
|
| 35. |
- Kim, Jinjae, et al.
(författare)
-
Constitutive modeling of commercial pure titanium sheet based on non-associated flow rule and differential hardening
- 2022
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 230
-
Tidskriftsartikel (refereegranskat)abstract
- The commercial-pure titanium (CP-Ti) sheet has attracted a great interest from biomedical and aerospace industries because of its strong mechanical advantages such as lightweight, high strength, good formability, and corrosion-resistance. However, strong anisotropic features, such as evolutionary yield surface and strength difference in tension and compression, of the CP-Ti require advanced constitutive modeling compared to standard advanced high strength steel sheets. This study took into account the differential hardening behavior and the changing R-value of CP-Ti sheet observed during the uniaxial tensile and bulge tests in developing a material model. The observed behaviors are modeled by Hill48 quadratic function based on non-associated flow rule with equivalent plastic work dependent evolutionary parameters. The developed material model was then implemented into a user material subroutine (VUMAT) for ABAQUS/EXPLICIT and used to simulate a circular deep drawing to verify the developed model. Simulation results are compared with those of a material model coupling Yld2000–2d yield function with associated flow rule. The comparison shows that the developed material model provides not only a good agreement with the experiment for yield and potential surfaces but also accurate predictions in forming simulations.
|
|
| 36. |
- Kunwar, Anil, et al.
(författare)
-
Combining multi-phase field simulation with neural network analysis to unravel thermomigration accelerated growth behavior of Cu6Sn5 IMC at cold side Cu–Sn interface
- 2020
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 184
-
Tidskriftsartikel (refereegranskat)abstract
- In Pb-free solder alloys used in solder balls of diameter of 50 µm or smaller, larger proportion of Cu6Sn5 intermetallics formation is a major reliability concern, and this is aggravated in presence of external thermal gradient. A complete understanding of the mechanism for intermetallics compound (IMC) growth under thermomigration is essential for devising solder materials resistant to degradation under thermal gradient. This work integrates neural network analysis with multi-phase field method to quantify the mechanism of thermomigration at the cold side of a solder-substrate system. At hot side temperature of 523.15 K, 1D multi-phase field model is built for a combined driving force of bulk diffusion and thermomigration, and is solved using finite element method (FEM). The free energy density function for the thermomigration driving force is introduced, and coupled with the functions for bulk and interfacial free energy density of each phase. Data of heats of transport, temperature difference and growth rate constant of IMC are obtained from multiple FEM simulations, and the FEM-generated dataset is employed in the neural network. The machine learning predicted growth rate constant is tallied with experimental value, and heat of transport of Cu in IMC phase (QCuimc) is determined from the inverse method. The obtained value of optimized QCuimc is +35.10 kJ/mol. 2D IMC grain growth simulations are performed with hot-side at 523.15 K and the cold side lowered to 523.0817 K and 522.0 K respectively, thereby revealing that the accelerated grain growth for larger temperature difference is noticed within the first 20 s of the simulations.
|
|
| 37. |
- Linares Arregui, Irene, et al.
(författare)
-
Elastic-plastic characterization of a high strength bainitic roller bearing steel-experiments and modelling
- 2010
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 52:10, s. 1254-1268
-
Tidskriftsartikel (refereegranskat)abstract
- Monotonic and cyclic deformations were studied for a high strength bainitic roller bearing steel. The temperature of 75 °C corresponded to normal roller bearing conditions. The materials showed hydrostatic influence on yielding, but no or marginal influence of plastic deformation on density change. Therefore, a linear elastic constitutive model with pressure dependent yielding, non-associated flow rule, combined non-linear kinematic and isotropic hardening was necessary to characterize the cyclic behaviour. A stepwise process is detailed for determining the material parameters of the pressure dependent model, where particular attention was placed on the hardening parameters. One set of parameters was sufficient to describe all tested load ranges including compressive ratchetting. Some comparative tests were performed at room temperature, 150 °C and on martensitic specimens at 75 °C. The temperature influence was limited to the isotropic hardening parameters.
|
|
| 38. |
- Linares Arregui, Irene, et al.
(författare)
-
Non-linear elastic characterisation of a high strength bainitic roller bearing steel
- 2013
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 68, s. 1-15
-
Tidskriftsartikel (refereegranskat)abstract
- A small but not negligible non-linear elastic behaviour was detected when investigating cyclic uniaxial push-pull experiments on a high strength bainitic steel. Cyclic torsion experiments led to the conclusion that the shear modulus was relatively constant. A non-linear elastic model was implemented where the bulk modulus was extended with a second order term related to the elastic dilatation and where the shear modulus was constant. The material presented a strength differential effect (SDE), with larger yield stress in compression than in tension. Consequently, the non-linear elastic model was combined with a plasticity model that incorporated a Drucker-Prager yield surface, non-associated flow rule and combined non-linear hardening. Expressions that include non-linear elasticity were derived for the elastic-plastic hardening and the compliance tensors. The extended material model predicted the elastic-plastic results from cyclic push-pull experiments. Also, a phenomenological analysis of the cyclic elastic response showed isotropic damage in the elastic moduli. The steady-state damage increased linearly with the cyclic plastic strain range.
|
|
| 39. |
- Liu, Zibo, 1989-, et al.
(författare)
-
Improving sound insulation near ring and coincidence frequencies of cylindrical sandwich shells
- 2022
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 235, s. 107661-
-
Tidskriftsartikel (refereegranskat)abstract
- This paper proposes an impedance-based design methodology for cylindrical sandwich shells, with the aim to improve the sound transmission loss properties near the ring and coincidence frequency regions. The approach enables to systematically address the poor acoustic performance, characteristic of these problematic frequency regions, while retaining the mechanical properties of these structures. This is done by seeking to suppress the mass-controlled region in the frequency spectrum, with properly tuned characteristic frequencies of the structure, completed by a degree of damping treatment. The impedance-based approach allowing this tuning is derived from the canonical wave equation with a view to sound transmission through cylindrical shells. In addition to offering fast, early design possibilities, the method provides physical insights into the vibroacoustic performance of the shell, for instance introduced to estimate the sound transmission loss of shallow curved sandwich panels in the low-frequency range. Oblique-and diffuse-field conditions are investigated, validating the analytical developments against finite element calculations.
|
|
| 40. |
- Mattiasson, Kjell, 1948, et al.
(författare)
-
An evaluation of some recent yield criteria for industrial simulations of sheet forming processes
- 2008
-
Ingår i: International Journal of Mechanical Sciences. - 0020-7403. ; 50, s. 774-787
-
Tidskriftsartikel (refereegranskat)abstract
- The present paper deals with material modeling in connection with sheet metal forming analyses. One purpose of the report is to discuss the special needs and demands of industrial analysts. With this in mind, in particular, the demands put on the yield condition are analyzed. Two recent yield criteria for anisotropic metal sheets, in the literature denoted Yld2000 and BBC2000, respectively, are found to be very well suited for industrial use. They do both belong to a group of yield criteria called the ‘‘Hosford family’’. Practical issues with regard to these yield criteria, such as procedures for determining the parameters being part of the models, implementation issues, and numerical efficiency, are thoroughly discussed. A version of the above criteria, using a reduced set of parameters, is proposed, and is shown to offer a significantly reduced computing time at the cost of some loss of accuracy.
|
|
| 41. |
- Mattiasson, Kjell, 1948, et al.
(författare)
-
On the prediction of failure in metal sheets with special reference to strain path dependence
- 2014
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 88, s. 175-191
-
Tidskriftsartikel (refereegranskat)abstract
- Prediction of failure in metal sheets is an important topic for the sheet forming community, as well as for the automotive crash community. The word 'failure' can have different meaning for different individuals within these communities. Methods for failure prediction within this area can either focus on the prediction of plastic instability (necking), or on the actual fracture phenomenon. The pros and cons of these approaches are discussed in this paper. The current authors have chosen to favour methods for necking prediction. The traditional method for necking prediction is to use a limit curve in the principal strain space (FLD). The great disadvantage of this approach is that it is only applicable for linear strain paths. In fact, the necking phenomenon can be shown to be strongly strain path dependent. In the current report, four different numerical methods for instability prediction are discussed, and compared in applications to some simple problems involving broken strain paths. It is shown that these methods can yield dramatically different results in some particular cases. Based on the findings of this study, the paper concludes with some recommendations for how the failure prediction problem best can be handled in industrial sheet forming and crash simulations.
|
|
| 42. |
- Mirkhalaf, S. Mohsen, 1982, et al.
(författare)
-
An FE-based orientation averaging model for elasto-plastic behavior of short fiber composites
- 2022
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 219
-
Tidskriftsartikel (refereegranskat)abstract
- A new micro-mechanical model for predicting the non-linear elasto-plastic behavior of short fiber reinforced composites is presented. The model is developed based on a two-step Orientation Averaging method, and is capable of accommodating a wide variety of micro-structural parameters. In the first step, Finite Element Analyses are performed on a unit cell (single fiber surrounded by matrix). Then, the unit cell response is up-scaled by calibrating its response to an elasto-plastic surrogate constitutive model. In a subsequent second homogenization step, a self-consistent interaction scheme is proposed. The predictive capability of the resulting two-step homogenization scheme is then evaluated, next to versions that adopt more traditional averaging schemes (Voigt and Reuss, providing upper and lower bounds, respectively), through comparisons to experiments and direct numerical simulations of realistic Representative Volume Elements. Results show that the model gives fairly good predictions. It is emphasized that the model is capable of accommodating any desired fiber orientation distribution, very large ranges of fiber aspect ratios and fiber volume fractions. Also, the model is computationally very efficient compared to the RVE computational homogenization approach, and thus, it could be conveniently used in applications possessing different fiber orientations at different points of a component.
|
|
| 43. |
- RAZANICA, SENAD, 1988, et al.
(författare)
-
FE modeling and simulation of machining Alloy 718 based on ductile continuum damage
- 2020
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 171
-
Tidskriftsartikel (refereegranskat)abstract
- A novel model for rigid visco-plastic flow and continuous damage evolution is proposed for the modeling and simulation of chip formation of the alloy 718. The model draws from a recent thermodynamically consistent damage coupled to elasto-visco-plasticity framework for ductile failure, which is advanced to purely dissipative flow stress problems in the DEFORM 2D\texttrademark platform. As opposed to standard models with direct damage-plasticity coupling, the present model describes this coupling through a visco-plastic damage driving energy. The effective material response is described by the Johnson-Cook model where onset of damage evolution is controlled by a modified Cockcroft-Latham failure criterion, facilitating a flexible modeling of serrated chip formation. By comparing the proposed continuous damage degradation model to the damage drop method in DEFORM 2D\texttrademark, the role of ductile failure on the chip formation is investigated. The model is calibrated and validated against experimental machining tests, where both continuous and serrated chip formation is observed for the alloy 718 depending on the cutting speed. From the experiment, cutting forces, chip shapes and tool-chip contact lengths were analyzed and compared to the model response. A good agreement between model and experimental results is obtained.
|
|
| 44. |
- Rentmeester, Rikard, et al.
(författare)
-
On mixed isotropic-distortional hardening
- 2015
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 92, s. 259-268
-
Tidskriftsartikel (refereegranskat)abstract
- Mixed isotropic-distortional hardening allows for individual stress-plastic strain relations in different straining directions. Such hardening can be obtained by allowing the parameters in the effective stress function depend on anisotropy functions of the equivalent plastic strain. A methodology to calibrate these anisotropy functions is proposed in this work, and is demonstrated on an austenitic strainless steel. A high exponent eight parameter effective stress function for plane stress states is utilised. The anisotropy functions are calibrated by the use of experimental data from uniaxial tensile test data in three material directions and a balanced biaxial test. The plastic anisotropy is evaluated at a finite number of plastic strains, and it is assumed to vary piecewise linearly with respect to the equivalent plastic strain. At each level of plastic strain, the anisotropy is correctly represented, even if rather large increments in plastic strain are used in the calibration. It was found that there are at least two sets of anisotropy functions which satisfy the conditions in the calibration procedure. The resulting uniaxial stress-strain relations from the two sets of anisotropy functions in four additional straining directions, not included in the calibration set, were compared to the corresponding experimental data. From this validation, one of the anisotropy function sets could be discarded, whereas the other one gave a good prediction of the stress-strain relations in all the four additional directions. (C) 2015 Elsevier Ltd. All rights reserved.
|
|
| 45. |
- Sedlak Mosesson, Michal, et al.
(författare)
-
A duplex oxide cohesive zone model to simulate intergranular stress corrosion cracking
- 2021
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 197
-
Tidskriftsartikel (refereegranskat)abstract
- A finite element model with slip-oxidation is proposed for solving intergranular stress corrosion cracking (IGSCC) with duplex oxides replicating the cyclic physics of the slip oxidation. The purpose is to investigate the crack growth effect due to different rate, compositions and kinetics of the duplex oxide. The finite element model is based on a coupling between cohesive zone formulation, slip-oxidation model and a diffusion model. The cohesive zone formulation includes a degradation formulation which is linked to the slip-oxidation formulation. The environmental properties in the slip-oxidation were obtained from the diffusion modeled with Fick?s second law in one-dimension. This was then coupled to the structural model by a segregated solution scheme. The mesh of the cohesive zone adapts to the oxide thickness of the duplex oxide during the crack growth. The duplex oxide has the mathematical form of a power law or a logarithmic form. The model showed matching results for all duplex oxide combinations in varying stress, but the inner logarithmical oxide gave higher crack growth rates than the power law. The power law with the thicker inner oxide showed good results for the change of stress intensity factor and gave the best results when the yield stress was varied. Grain misorientation effect was higher for the duplex oxides with thicker outer oxides.
|
|
| 46. |
- Song, Yubao, et al.
(författare)
-
Suppression of the vibration and sound radiation of a sandwich plate via periodic design
- 2019
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier. - 0020-7403 .- 1879-2162. ; 150, s. 744-754
-
Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the suppression of vibration and sound radiation of a sandwich plate through the use of periodic design. A periodic sandwich plate is constructed and its dispersion relation is calculated. The vibration and sound radiation properties of the periodic sandwich plate are studied. Via the comparison of the periodic and bare sandwich plate, the effects of the periodic design on the vibration and sound radiation are analysed. Further, to know the sound radiation properties better, sound radiation efficiency of the periodic and bare sandwich plates is compared. In addition, the effects of the boundary conditions on the properties of the periodic sandwich plate are analysed. The numerical results demonstrate that the vibration and sound radiation are greatly suppressed over the stop band of the periodic sandwich plate. The suppression can also be obtained in part of pass bands. It is also shown that the periodic design can be an effective method for the reduction of the sound radiation efficiency. The suppression for the vibration and sound is greater than that caused by only increasing the mass of the plate in the designing frequency range.
|
|
| 47. |
- Spagnoli, A., et al.
(författare)
-
The fracture mechanics in cutting : A comparative study on hard and soft polymeric materials
- 2018
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 148, s. 554-564
-
Tidskriftsartikel (refereegranskat)abstract
- An experimental campaign has been carried out with the aim of providing an insight into the fracture processes occurring during the cutting of different types of polymers, with features ranging from typically brittle to soft hyperelastic behaviour. The steady state of cutting is investigated using a sharp thin blade, and tracking the insertion force versus the penetration displacement. For soft, highly-deformable polymers, the influence of large deformations at the crack tip is also taken into account, through full-field finite strain maps obtained by means of digital image correlation. In brittle polymers, the influence of the cutting tool sharpness is discussed with respect to the onset of crack propagation, through a comparison with a simplified analytical model, and numerical finite element analyses. The results suggest that the propagation of the cut clearly depends on the tool sharpness, and for a class of brittle polymers it appears that this may happen as a stable fracture process, with the distance between the blade and the crack tip remaining constant during propagation. On the contrary, soft polymers appear to be much less sensible to the tool profile, and it is the large deformation that ultimately determines the fracture behaviour when the crack tip is reached by the blade.
|
|
| 48. |
- Staaf, Henrik, 1976, et al.
(författare)
-
Effective piezoelectric energy harvesting with bandwidth enhancement by assymetry augmented self-tuning of conjoined cantilevers
- 2019
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403. ; 150, s. 1-11
-
Tidskriftsartikel (refereegranskat)abstract
- Vibrational energy harvesting offers a potential power supply for future intelligent wireless sensors. In order to make vibrational energy harvesters more useful, a broad bandwidth is desirable since many vibrations are stochastic in nature. In this paper we use a piezoelectric self-tuning energy harvester to demonstrate the importance of designing for asymmetry in a system of conjoined cantilevers. Asymmetry is achieved by varying the piezoelectric cantilever lengths as well as the proof mass weights. In addition to bandwidth broadening, a self-tuning effect is experimentally demonstrated by a sliding mass. The measurement results confirm previous model predictions.
|
|
| 49. |
- Starman, Bojan, et al.
(författare)
-
Differences in phase transformation in laser peened and shot peened 304 austenitic steel
- 2020
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 1879-2162 .- 0020-7403. ; 176
-
Tidskriftsartikel (refereegranskat)abstract
- Laser Shock Peening (LSP) and Shot Peening (SP) are processes used to mechanically alter the surface properties of metals by inducing a transient high-pressure wave by a laser pulse or by a high-velocity impact of a peening particle. Both processes aim to induce compressive residual stresses near the surface and the level of residual stresses obtained from SP or LSP is similar. When austenitic steel is peened, martensitic phase transformation takes place. It has been observed in experiments that the amount of martensite in shot-peened surfaces is significantly higher than in laser peened surfaces. The cause of these differences is, however, not yet fully explained and the available explanations are often conflicting. In this study, both SP and LSP are modelled using an elasto-viscoplastic model that also account for martensitic phase transformation. The analyses show that LSP and SP are fundamentally different from a mechanical point of view. By tracing the stress trajectories in the principal stress space, it is shown that martensite formation and plastic straining are highly dependent on the intensity of the individual components of hydrostatic and deviatoric stress, which evolve differently in the two processes.
|
|
| 50. |
- Sun, Fengzhen, et al.
(författare)
-
Experimental and numerical investigation on shear banding during nanomachining of an amorphous glassy polymer
- 2019
-
Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 151, s. 13-21
-
Tidskriftsartikel (refereegranskat)abstract
- This paper discusses the shear banding phenomenon which took place during nanomachining of an amorphous glassy polymer. The nanomachining were carried out with varying machining conditions (depth of cut, machining speed), and the morphologies of the machined surfaces were characterized using atomic force microscopy. The experiments reveal the occurrence of shear band as the critical machining condition is reached. The shear banding was rationalized by the effect of adiabatic heating during machining. Finite element modelling of nanomachining was conducted using an existing elastic-viscoplastic model for this polymer, which accounts for the adiabatic heating due to plastic dissipation. The simulation was then compared with the experiment. It shows that the simulation can capture the main features of shear banding in nanomachining, indicating that the machining is controlled by a localized deformation mechanism. This work can be helpful in optimizing the processing parameters to improve the surface quality of optical products.
|
|
