| 1. |
- Gozzi, Jonas, et al.
(author)
-
Experimental investigation of the behavior of extra high strength steel
- 2005
-
In: Experimental mechanics. - 0014-4851 .- 1741-2765. ; 45:6, s. 533-540
-
Journal article (peer-reviewed)abstract
- This paper comprises a study concerning the mechanical behavior of extra high strength steel. This is investigated by means of biaxial testing of flat cross-shaped specimens in the full σ1-σ2 plane, a concept developed earlier at Steel Structures, Luleå University of Technology. Furthermore, new specimen designs had to be developed to enable testing of a material with high yield strength and low ultimate over yield strength ratio, such as the extra high strength steel Weldox 1100. The tests are performed in two steps: one initial loading followed by unloading and a subsequent loading in a new direction. The test results, containing data from 15 biaxial tests, are characterized by a slightly anisotropic initial yield criterion where the proof stress in compression is consequently somewhat higher compared to the results in tension. In the subsequent loading the observed phenomena are a Bauschinger effect in the direction opposite the initial loading direction and that the transition from elastic to plastic state in subsequent loadings is gradual and direction-dependent.
|
|
| 2. |
- Gradin, Per, et al.
(author)
-
The Use of Acoustic Emission Monitoring to Rank Paper Materials With Respect to their Fracture Toughness
- 2008
-
In: Experimental mechanics. - : Springer Science and Business Media LLC. - 0014-4851 .- 1741-2765. ; 48:1, s. 133-137
-
Journal article (peer-reviewed)abstract
- In this study, simplified Acoustic Emission (AE) equipment, in essence an AE signal conditioner and a USB (Universal Serial Bus) data acquisition system, are used to study what happens in paper structures during mechanical loading. By the use of such equipment, some parameters that can be extracted are e.g. the stress and strain at onset of AE, the stress and strain at the onset of rapid AE (defined in some appropriate way), the emission rate at the first stage of loading and the stress and strain at final rupture. In this study however, the interest is focused on one particular parameter i.e. the elastic strain energy density Wc at onset of AE. This is a parameter with a clear physical meaning and in this study, the correlation between this parameter and a fracture toughness measure, is investigated. The conclusion is that when nine different paper materials (with a large span regarding properties) are considered, there is a correlation (however not linear) between these two parameters.
|
|
| 3. |
- Tarigopula, Venkapati, et al.
(author)
-
A study of large plastic deformations in dual phase steel using digital image correlation and FE analysis
- 2008
-
In: Experimental mechanics. - : Springer Science and Business Media LLC. - 0014-4851 .- 1741-2765. ; 48:2, s. 181-196
-
Journal article (peer-reviewed)abstract
- Large plastic deformation in sheets made of dual phase steel DP800 is studied experimentally and numerically. Shear testing is applied to obtain large plastic strains in sheet metals without strain localisation. In the experiments, full-field displacement measurements are carried out by means of digital image correlation, and based on these measurements the strain field of the deformed specimen is calculated. In the numerical analyses, an elastoplastic constitutive model with isotropic hardening and the Cockcroft - Latham fracture criterion is adopted to predict the observed behaviour. The strain hardening parameters are obtained from a standard uniaxial tensile test for small and moderate strains, while the shear test is used to determine the strain hardening for large strains and to calibrate the fracture criterion. Finite Element (FE) calculations with shell and brick elements are performed using the non-linear FE code LS - DYNA. The local strains in the shear zone and the nominal shear stress-elongation characteristics obtained by experiments and FE simulations are compared, and, in general, good agreement is obtained. It is demonstrated how the strain hardening at large strains and the Cockcroft - Latham fracture criterion can be calibrated from the in-plane shear test with the aid of non-linear FE analyses.
|
|
| 4. |
- Östlund, Magnus, et al.
(author)
-
Experimental determination of residual stresses in paperboard
- 2005
-
In: Experimental mechanics. - 0014-4851 .- 1741-2765. ; 45:6, s. 493-497
-
Journal article (peer-reviewed)abstract
- A method for the experimental determination of the through-thickness residual stress distribution in paper-board is presented.The successive removal of thin layers from strips of board through surface grinding changes the stress-state and the bending stiffness resulting in a changed curvature, which is measurable. From tests of strips in both in-plane directions, stress distributions can then be evaluated using the Treuting-Read method. Geometrically nonlinear effects at the large deformations taking place are avoided through a proper choice of strip dimensions. Typical results are presented and factors influencing the accuracy of the determination are thoroughly discussed.
|
|
