| 1. |
- Aoki, S., et al.
(författare)
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Identification of elastic/visco-plastic material constants under impact loading
- 2000
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Ingår i: IUTAM Symposium on Field Analysis for Determination of Material Parameters - Experimental and Numerical Aspects. - Dordrecht : Encyclopedia of Global Archaeology/Springer Verlag. - 1402012837
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Konferensbidrag (refereegranskat)abstract
- A method for identifying the material constants of an elastic/visco-plastic meterial under tensile impact loading is proposed. In this method, the Kalman filter and the finite element method are used together with a few test data. To obtain data for high strain rates, notched specimens are employed, because arbitrarily shaped specimens are available in this method. To increase the accuracy of identification, a test under a relatively low strain rate is needed in addition to a test under a high strain rate. The optimum strain rate is determined in such a way that the largest eigen value of the covariance matrix of the estimated parameters becomes minimum. A numerical simulation in performed to demonstrate the validity and usefulness of this method
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| 2. |
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| 3. |
- Carlsson, J., et al.
(författare)
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Method for determination of in-hole dynamic force-penetration data from two-point strain measurement on a percussive drill rod
- 1990
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Ingår i: International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts. - 0148-9062 .- 1879-2073. ; 27:6, s. 553-558
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Tidskriftsartikel (refereegranskat)abstract
- The aim of the present investigation is to establish a testing method suited for determination of in-hole dynamic force-penetration data for non-uniform standard percussive drill rod-bit configurations. The method is based on a version of the method of two-point strain measurement, which permits non-uniform rods, i.e. rods with variable characteristic impedance. This version allows normal force and particle velocity to be evaluated at an arbitrary cross-section of a homogenous non-uniform elastic rod from strain measurements performed at two different cross-sections of the same rod. The main problem of this investigation is to assess whether the influence of threads can be considered insignificant. As a part of the study force-penetration relationships have been determined for the penetration of a standard Sandvik Rock Tools button bit into Swedish Bohus granite.
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| 4. |
- Eman, Jesper, et al.
(författare)
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Fracture strains at holes in high-strength steel : a comparison of techniques for hole-cutting
- 2007
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Ingår i: Experimental analysis of nano and engineering materials and structures. - Dordrecht : Springer. - 9781402062384 - 9781402062391 ; , s. 195-196
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Konferensbidrag (refereegranskat)abstract
- Sheet metal is often used as a raw-material from which structural parts are fabricated through pressing operations. This is the case for example in the vehicle industry where the entire structure of a car is made from sheet material, In many modern cars, crash-protecting parts are made from ultra-high strength steel and such parts are often press-hardened to a tensile strength of 1500 MPa or more in a process with simultaneous forming and quenching. Holes in these parts are sometimes necessary for practical reasons and the fracture criteria used in the design process must be relevant also for such cases.
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| 5. |
- Eman, Jesper, et al.
(författare)
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Spatially resolved observations of strain fields at necking and fracture of anisotropic hardened steel sheet material
- 2009
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 46:13, s. 2750-2756
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Tidskriftsartikel (refereegranskat)abstract
- In this work plastic strain localization, also referred to as necking, of press-hardened ultra-high strength steel is observed using digital speckle correlation. The region of the neck is studied during tensile tests of specimens specially designed to facilitate strain localization at an inner point of the material, thus avoiding edge effects on localization and fracture. By using measurements with a length scale small enough to properly resolve the neck, its growth and shape can be studied. Furthermore, the anisotropy of the material is investigated by examining specimens cut out at different angles to the rolling direction. It is seen that the local fracture strain of specimens cut out along the rolling direction is approximately twice as high as it is for specimens cut out perpendicular to the rolling direction.
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| 6. |
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| 7. |
- Hernandez, Sinuhe, et al.
(författare)
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High temperature three-body abrasive wear of 0.25C 1.42Si steel with carbide free bainitic (CFB) and martensitic microstructures
- 2016
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Ingår i: Wear. - : Elsevier BV. - 0043-1648 .- 1873-2577. ; 360-361, s. 21-28
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Tidskriftsartikel (refereegranskat)abstract
- In the present work, the wear behaviour of different steels has been investigated under a three body abrasive environment at room and elevated temperatures. High-silicon steel (0.25C-1.42Si) was austempered at 300 and 320 ˚C in order to obtain two carbide-free bainitic steels with different mechanical properties. The same steel subjected to two different quench and temper heat treatments was used as a reference material for mechanical and wear testing. The steels were subjected to three-body abrasive wear by means of a high temperature continuous abrasion tester (HT-CAT). The tests were done at 25, 300 and 500 °C respectively. All samples showed similar wear rates at room temperature. At 500 °C, the material austempered at 320 ˚C showed the highest toughness and the lowest wear rate. High temperature hardness and impact toughness tests showed that abrasive wear is not only influenced by hardness but also by the toughness of the material. Owing to their good strength/toughness combination CFB steels could prove to be an important material for abrasive wear applications
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| 8. |
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| 9. |
- Isaksson, Erik, et al.
(författare)
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Correlation of vehicle crash model parameters to car properties in low-speed collisions : a design of experiments approach
- 2010
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Ingår i: International Journal of Crashworthiness. - : Informa UK Limited. - 1358-8265 .- 1754-2111. ; 15:3, s. 241-249
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Tidskriftsartikel (refereegranskat)abstract
- In the current study, a methodology for relating model parameters in a one dimensional Mass Spring Damper (MSD) model to global properties of a car, e.g. axial stiffness, bending stiffness and mass, is presented. It is shown that these three vehicle properties affect the vehicle's crash performance in low-speed collision tests used for industrial verification of bumper system performance. Based on information of the properties for a vehicle under development, parameters in the MSD model can be adjusted to give the correct boundary conditions for a finite element (FE) crash simulation with a candidate bumper design. In the FE simulations, the MSD model is then coupled to the FE mesh of candidate bumper design to find a bumper that meets the crash performance requirements of a car under development. The methodology is based on Design of Experiments (DOE) and FE simulations on a public domain model of a Ford Taurus. The knowledge gained from this study gives a valuable tool to use in design and development of bumper systems for the automotive industry.
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| 10. |
- Jonsén, Pär, et al.
(författare)
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Identification of lumped parameter automotive crash models for bumper system development
- 2009
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Ingår i: International Journal of Crashworthiness. - : Informa UK Limited. - 1358-8265 .- 1754-2111. ; 14:6, s. 533-541
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Tidskriftsartikel (refereegranskat)abstract
- During the design and development process of bumper systems for the automotive industry, information about the future car model is limited. Normally, iterative finite element (FE) analyses of different crash loading tests are used to find an appropriate bumper system to the coming car model. Because of the lack of information, only a rough model of the car is normally utilised in the FE simulations. This leads to uncertainties in the bumper design since the dynamic response of the car is dependent on the load case and the properties of the actual bumper system. This paper presents a method for identification of lumped parameter models based on results from crash tests of a Volvo S40. The ability to predict the measured results for models with different number of degrees of freedom (DOF) is investigated. Also, a validation of the model together with an FE mesh of the bumper system is presented. The results clearly show that a linear mass spring damper model with 2 DOF can be used to predict the response from the measurements in case of symmetric loading. Further increase of the number of DOF only causes small or no improvements of the agreement between the predicted and measured crash response.
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