| 1. |
- Khurshid, Mansoor, et al.
(författare)
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Root fatigue strength assessment of fillet welded tube-to-plate joints subjected to multi-axial stress state using stress based local methods
- 2017
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Ingår i: International Journal of Fatigue. - : ELSEVIER SCI LTD. - 0142-1123 .- 1879-3452. ; 101, s. 209-223
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Tidskriftsartikel (refereegranskat)abstract
- In this study the fatigue strength of fillet welded tube-to-plate joints failing at the weld root and subjected to multi-axial stress states is investigated. The fatigue test data is collected from the literature and it is assessed together with the experimental data generated in this study. Finite element analysis is used to analyze the stress state at the weld root. The fatigue strength estimation capabilities of local stress based methods such as the Principal Stress Hypothesis (PSH), von Mises Stress Hypothesis (vMH), Modified Wohler Curve Method (MWCM), and Effective Equivalent Stress Hypothesis (EESH) are compared. The applicability of modified Gough Pollard Equation (GPE) in local stress system is also assessed. It is observed that most of the proposed local stress assessment methods can estimate the fatigue strength of fillet welds subjected to multiaxial stress states with constant principal stress direction, e.g. proportional loading. In case of load histories which produce varying principal stress directions with respect to time, e.g. non-proportional loading, better estimation capability is shown by MWCM and EESH. In most of the cases of varying principal stress direction load histories, vMH and PSH fail to estimate the fatigue strength. The fatigue strength of specimens tested with combined loading is reduced in comparison to the fatigue strength of specimens tested with only internal pressure and only bending loading. Out-of-phase loading does not affect the fatigue strength significantly for the specimens in this study. However; a decrease in fatigue strength is observed for the test data for out-of-phase loading collected from the literature.
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| 2. |
- Lundkvist, Axel, et al.
(författare)
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Geometric and Material Modelling Aspects for Strength Prediction of Riveted Joints
- 2023
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 13:3, s. 500-
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study is to develop a methodology for static strength and failure mode simulation of hot-driven riveted joints. The purpose is to be able to accurately estimate a rivet joint's static strength behaviour and its failure mode without relying on experiments, to save both time and resources during the design of joints. The non-linear finite element analysis modelling framework considered the rivet joint configurations and geometry, the material properties of the plate and rivet as well as the clamping force of the hot-driven rivet. A ductile damage model was also implemented to capture the stress softening of the materials and the failure modes of the joints. Using experimental data from literature, the modelling framework is validated, and it is shown that it is able to capture the strength behaviour and failure modes of different configurations of rivet joints markedly well. The effect of the rivet pre-load on the mechanical response of the joint is also studied and it is shown that the strength of the joint increased with the increase in rivet pre-load. The modelling framework is then applied to an industrial component. The modelling framework is used to compare welding and riveting as joining methods in a component built in two grades of high-strength steel. It is found that the welded joint possessed greater strength compared to the proposed riveted joint. However, using the proposed simulation methodology developed, a riveted joint with matching strength to the welded joint could be designed.
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| 3. |
- Zhu, Jinchao, et al.
(författare)
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Computational weld-mechanics assessment of welding distortions in a large beam structure
- 2021
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Ingår i: Engineering structures. - : Elsevier BV. - 0141-0296 .- 1873-7323. ; 236
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Tidskriftsartikel (refereegranskat)abstract
- Unwanted distortions are typically observed in components after the welding process. Physical trial tests and extra post-treatments are being widely utilized in industries to minimize and correct the out of tolerance distortions. These methods are time-consuming and costly. There has been growing interest in digital tools which have great potential to minimize the physical test loops and corrections. In this study welding distortions analysis has been carried out on a large beam structure experimentally and numerically using computational welding mechanics (CWM) techniques such as the inherent strain (local?global) method and the shrinkage method, together with the lumping approach. The estimated distortions from the shrinkage together with lumping approaches were in good agreement with the experimental measurements and the computational time affordable. The inherent strain (local?global) method captured the trend of distortion with an underestimation of distortions. The accuracy of the estimated residuals stresses from the inherent strain (local?global) approach is higher than the one from shrinkage together with lumping approaches. Moreover, the effects of various welding process parameters (i.e. welding sequence, fixture, and weld pool size) on welding distortions were investigated. It is found that following the proper welding sequence could minimize the welding distortion of the beam structure. Increasing the constraints of fixtures can prevent welding distortion effectively and reducing weld pool size results in less welding distortions of the beam structure.
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| 4. |
- Zhu, Jinchao, et al.
(författare)
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Evaluation of local stress-based fatigue strength assessment methods for cover plates and T-joints subjected to axial and bending loading
- 2022
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Ingår i: Fatigue & Fracture of Engineering Materials & Structures. - : Wiley. - 8756-758X .- 1460-2695. ; 45:9, s. 2531-2548
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Tidskriftsartikel (refereegranskat)abstract
- This study aims to find suitable fatigue assessment methods for welded structures (cover plates and T-joints) subjected to axial and bending loading. The Hot Spot Stress (HSS), 1-mm stress (OM), Theory of Critical Distances (TCD), Stress Averaging (SA), and Effective Notch Stress (ENS) methods are evaluated in terms of accuracy and reliability. The evaluation is based on fatigue test data extracted from the literature and carried out in this study. It is found that the SA method can be used to assess the fatigue strength of cover plate joints under axial loading with relatively good accuracy and low scatter, followed by the ENS method. The HSS, TCD, SA, and ENS methods are conservative estimation methods for T-joints under bending, while the accuracy is low. Furthermore, fatigue design curves applicable for T-joints under bending are discussed, which can be used in the TCD method and SA method.
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| 5. |
- Barsoum, Imad, 1978-
(författare)
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The effect of stress state in ductile failure
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The industrial application of high strength steels in structural components has increased the demand on understanding the ductile failure behavior of this type of materials. In practical situations the loading experienced on components made out of these materials can be very complex, which may affect the failure behavior.The objective of this work is to study the effect of stress state on ductile failure and the mechanisms leading to rupture in high strength steels. The stress state is characterized by the stress triaxiality T and the Lode parameter L, which is a deviatoric stress state parameter that discriminates between axisymmetric or shear dominated stress states. For this purpose experiments on two different specimen configurations are performed; a double notched tube (DNT) specimen tested in combined tension and shear and a round notched bar (RNB) specimen tested in uniaxial tension. The two specimens give rise to different stress states at failure in terms of T and L. The failure loci for the DNT specimen show an abrupt change in ductility, indicating a transition between the rupture mechanisms necking of intervoid ligaments and shearing of intervoid ligaments. A clear difference in ductility between the two specimen configurations is also observed, which is closely associated with the difference in stress state at failure.A micromechanical model is developed, which assumes that ductile material failure occurs when the deformation becomes highly non-linear and localizes into a band. The model, which is applied to analyze the experiments, consists of a band with a square array of equally sized cells, with a spherical void located in the center of each cell. The model, extended with a shear criterion, captures the experimental trend rather well. The model also shows that the effect of the deviatoric stress state (L) on void growth, void shape evolution and coalescence is significant, especially at low levels of T and shear dominated stress state.
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