Effects of the stress state on plastic deformation and ductile failure: Experiment and numerical simulation using a newly designed tension‐shear specimen

2019 ◽  
Vol 42 (9) ◽  
pp. 2079-2092 ◽  
Author(s):  
Xue‐Wei Zhang ◽  
Jian‐Feng Wen ◽  
Xian‐Cheng Zhang ◽  
Xiao‐Gang Wang ◽  
Shan‐Tung Tu
Keyword(s):  
Numerical Simulation ◽  
Plastic Deformation ◽  
Stress State ◽  
Ductile Failure ◽  
Shear Specimen

Failure Strain Criterion Accounting for the Effect of Material Strength

2021 ◽  
Author(s):  
N. Baghous ◽  
I. Barsoum
Keyword(s):  
Stress State ◽  
Ultimate Strength ◽  
Failure Criterion ◽  
Stress Triaxiality ◽  
Ductile Failure ◽  
High Strength Steels ◽  
Local Failure ◽  
Material Strength ◽  
Lode Parameter ◽  
Steel Grades

Abstract The objective of this study is to investigate the effect of the Lode parameter on different material strengths. Recent work has shown that ductile failure highly depends on the stress state characterized by both the stress triaxiality T and the Lode parameter L, which is related to the third deviatoric stress invariant. Thus, for six different steel grades, two different specimen geometries were manufactured to account for two different Lode parameters (L = −1 and L = 0), whereas T is controlled by introducing different sized notches at the center of the specimens. By performing tensile experiments and running finite element simulations, the ductile failure loci of the six materials showed variations between the two specimen geometries, indicating that the failure highly depends on the stress state characterized by both T and L. This indicates the need to reassess the ductile local failure criterion in the ASME codes that only accounts for T as a stress state measure. A Lode sensitivity parameter LS is defined based on the experimental results and revealed that the steel grades with ultimate strength higher than a certain threshold value (450 MPa) exhibit sensitivity to the Lode parameter, and the results showed that the LS increases with increase in the ultimate strength of the steel grade. The results were incorporated to enhance the original ASME local failure criterion by accounting for T, L, and LS to accurately assess ductile failure in high-strength steels.

Ring Specimen Geometry for Determining the Ductility of Tubulars

2016 ◽  
Author(s):  
M. A. Al Khaled ◽  
I. Barsoum
Keyword(s):  
Stress State ◽  
Plane Strain ◽  
Stress Triaxiality ◽  
Ductile Failure ◽  
Pressure Vessels ◽  
Ring Specimen ◽  
Lode Parameter ◽  
Wide Range ◽  
Failure Locus

Pressure vessels designed in accordance with the ASME BPVC code are protected against local ductile failure. Recent work has shown that local ductile failure highly depends on the stress state characterized by both stress triaxiality (T) and the Lode parameter (L). In this paper, the effect of stress state on the ductility of a tubular steel is studied. Two ring specimen configurations were optimized to allow the determination of the ductile failure locus of both tensile and plane strain loadings. The geometry of both ring specimen configurations was optimized to achieve a plane strain (L = 0) condition and a generalized tension (L = −1) condition. Notches with different radii were machined on both types to achieve a wide range of stress triaxiality. Specimens were manufactured from SA-106 carbon tubular steel and were tested to determine the ductile failure loci as a function of T and L. Failure locus of SA-106 steel was constructed based on the failure instants and was found to be independent of the variation in the Lode parameter. The ASME-BPVC local failure criterion showed close agreement with experimental results.

Deformation, Fracture, and Friction Processes

2020 ◽  
pp. 14-24
Author(s):  
Francois Louchet
Keyword(s):  
Plastic Deformation ◽  
Ductile Failure ◽  
Scientific Validity ◽  
Coulomb’S Friction ◽  
Dynamic Loadings ◽  
Triggering Mechanisms ◽  
The Difference ◽  
Elastic And Plastic Deformation ◽  
Physical Quantities ◽  
Rupture Criterion

The main mechanical and physical quantities and concepts ruling deformation, fracture, and friction processes are recalled, with particular attention paid to the simplicity of the analysis, but without betraying the scientific validity of the arguments. We particularly discuss the difference between between elastic and plastic deformation, and quasistatic and dynamic loadings, essential in avalanche triggering mechanisms. The physical origin of Griffith’s rupture criterion that rules both fracture nucleation and propagation, and the transition between brittle and ductile failure processes, is thoroughly discussed. We also explain the physical meaning of the classical Coulomb’s friction law, showing why it can hardly apply to a non-conventional porous, brittle, and healable solid like snow.

An Elastic-Plastic Solver of the Wheel-Rail Contact

2010 ◽  
Author(s):  
Constantin I. Ba˘rbiˆnt¸a˘ ◽  
Sulleyman Yaldiz ◽  
Alina Dragomir ◽  
Spiridon S. Cret¸u
Keyword(s):  
Plastic Deformation ◽  
Stress State ◽  
Plastic Material ◽  
Computer Code ◽  
Load Level ◽  
Analysis Model ◽  
Elastic Plastic ◽  
Circular Arcs ◽  
Plastic Analysis ◽  
Perfect Plastic

Wheel and rail in service undergo continual wear and plastic deformation at the surface, so that in time all wheel profiles will be different. The optimization by grinding a worn rail profile to minimize contact stresses requires the development of a software to reconstruct a rail profile using circular arcs. A working algorithm, able to be incorporated into a computer code, has been developed to solve the stress state in the general case of non-Hertzian contacts. To limit the pressure, an elastic-perfect plastic material has been incorporated into the computer code. The pressure distribution and the corresponding stresses states have been investigated for pure normal loadings, as well as for the combined, normal and tangential loadings. The elastic-plastic analysis model allows fast investigations regarding the influence of different parameters such as load level, contact geometry including the geometry of the worn profiles.

Numerical simulation of plastic deformation in polymer crystals

1999 ◽  
Author(s):  
A. I. Moussienko ◽  
Nikolay K. Balabaev ◽  
L. I. Manevitch
Keyword(s):  
Numerical Simulation ◽  
Plastic Deformation ◽  
Polymer Crystals
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