scholarly journals Correcting the Stress-Strain Curve in Hot Compression Process to High Strain Level

2009 ◽  
Vol 40 (4) ◽  
pp. 982-990 ◽  
Author(s):  
Y. P. Li ◽  
E. Onodera ◽  
H. Matsumoto ◽  
A. Chiba
Keyword(s):  
High Strain ◽  
Strain Curve ◽  
Hot Compression ◽  
Strain Level ◽  
Stress Strain Curve ◽  
Compression Process ◽  
Stress Strain

High Strain Rate Test of a Steel Plate under Blast Loading from High Explosive

2013 ◽  
Vol 767 ◽  
pp. 144-149 ◽  
Author(s):  
Tei Saburi ◽  
Shiro Kubota ◽  
Yuji Wada ◽  
Tatsuya Kumaki ◽  
Masatake Yoshida
Keyword(s):  
Strain Rate ◽  
Dynamic Stress ◽  
Steel Plate ◽  
High Strain ◽  
Strain Curve ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Time Deformation ◽  
Rate Test ◽  
High Strain Rate Test

In this study, a high strain rate test method of a steel plate under blast loading from high explosive was designed and was conducted by a combined experimental/numerical approach to facilitate the estimation process for the dynamic stress-strain curve under practical strain rate conditions. The steel plate was subjected to a blast load, which was generated by Composition C4 explosive and the dynamic deformation of the plate was observed with a high-speed video camera. Time-deformation relations were acquired by image analysis. A numerical simulation for the dynamic behaviors of the plate identical to the experimental condition was conducted using a coupling analysis of finite element method (FEM) and discrete particle method (DPM). Explosives were modeled by discrete particles and the steel plate and other materials were modeled by finite element. The blast load on the plate was described fluid-structure interaction (FSI) between DPM and FEM. As inverse analysis scheme to estimate dynamic stress-strain curve, an evaluation using a quasistatic data was conducted. In addition, two types of approximations for stress-strain curve were assumed and optimized by least square method. One is a 2-piece approximation, and was optimized by least squares method using a yield stress and a tangent modulus as parameters. The other is a continuous piecewise linear approximation, in which a stress-strain curve was divided into some segments based on experimental time-deformation relation, and was sequentially optimized using youngs modulus or yield stress as parameter. The results showed that the piecewise approximation can gives reasonably agreement with SS curve obtained from the experiment.

Evaluation of Anisotropic Pipe Steel Stress-Strain Relationships Influence on Strain Demand

2012 ◽  
Author(s):  
James D. Hart ◽  
Nasir Zulfiqar ◽  
Joe Zhou
Keyword(s):  
Strain Hardening ◽  
Pipe Steel ◽  
High Strain ◽  
Strain Curve ◽  
High Strength ◽  
Strain Response ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Hardening Modulus ◽  
Strain Relationship

Buried pipelines can be exposed to displacement-controlled environmental loadings (such as landslides, earthquake fault movements, etc.) which impose deformation demands on the pipeline. When analyzing pipelines for these load scenarios, the deformation demands are typically characterized based on the curvature and/or the longitudinal tension and compression strain response of the pipe. The term “strain demand” is used herein to characterize the calculated longitudinal strain response of a pipeline subject to environmentally-induced deformation demands. The shape of the pipe steel stress-strain relationship can have a significant effect on the pipe strain demands computed using pipeline deformation analyses for displacement-controlled loading conditions. In general, with sufficient levels of imposed deformation demand, a pipe steel stress-strain curve with a relatively abrupt or “sharp” elastic-to-plastic transition will tend to lead to larger strain demands than a stress-strain curve with a relatively rounded elastic-to-plastic transition. Similarly, a stress-strain curve with relatively low strain hardening modulus characteristics will tend to lead to larger strain demands than a stress-strain curve with relatively high strain hardening modulus characteristics. High strength UOE pipe can exhibit significant levels of anisotropy (i.e., the shapes of the stress-strain relationships in the longitudinal tension/compression and hoop tension/compression directions can be significantly different). To the extent that the stress-strain curves in the different directions can have unfavorable shape characteristics, it follows that anisotropy can also play an important role in pipeline strain demand evaluations. This paper summarizes a pipeline industry research project aimed at evaluation of the effects of anisotropy and the shape of pipe steel stress-strain relationships on pipeline strain demand for X80 and X100 UOE pipe. The research included: a review of pipeline industry literature on the subject matter; a discussion of pipe steel plasticity concepts for UOE pipe; characterization of the anisotropy and stress-strain curve shapes for both conventional and high strain pipe steels; development of representative analytical X80 and X100 stress-strain relationships; and evaluation of a large matrix of ground-movement induced pipeline deformation scenarios to evaluate key pipe stress-strain relationship shape and anisotropy parameters. The main conclusion from this work is that pipe steel specifications for high strength UOE pipe for strain-based design applications should be supplemented to consider shape-characterizing parameters such as the plastic complementary energy.

Determination of the Constants of Zerilli-Armstrong Constitutive Relation Using Genetic Algorithm

2011 ◽  
Vol 264-265 ◽  
pp. 862-870
Author(s):  
G.H. Majzoobi ◽  
S. Faraj Zadeh Khosroshahi ◽  
H. Beik Mohammadloo
Keyword(s):  
Genetic Algorithm ◽  
High Strain ◽  
Optimization Technique ◽  
Strain Curve ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Material Models ◽  
The Difference

Identification of the constants of material models is always a concern. In the present work, a combined experimental, numerical and optimization technique is employed to determine the constants of Zerilli-Armstrong model. The experiments are conducted on a compressive Hopkinson bar, the simulations are performed using finite element method and optimization is carried out using genetic algorithm. In the method adopted here, there is no need for experimental stress-strain curve which is always accompanied by restricting phenomenon such as necking in tension and bulging in compression. Instead of stress-strain curve, the difference between the post-deformation profiles of specimens obtained from experiment and the numerical simulations is adopted as the objective function for optimization purposes. The results suggest that the approach introduced in this work can substitute costly instrumentations normally needed for obtaining stress-strain curves at high strain rates and elevated temperature.

Dynamic Constitutive Equations and Behaviour of Brass at High Strain Rates

1995 ◽  
Vol 209 (4) ◽  
pp. 287-293 ◽  
Author(s):  
L-Y Li ◽  
T C K Molyneaux
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Yield Stress ◽  
Constitutive Equations ◽  
High Strain ◽  
Strain Curve ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
High Strain Rates ◽  
Stress Strain

This paper presents an experimental study of the mechanical properties of brass at high strain rates. The brass tested is the copperzinc alpha-beta and beta two-phase alloy in the cold-worked state. Experiments were conducted using an extended tension split Hopkinson bar apparatus. It is found that, at lower strain rates, the stress-strain curve is smooth, exhibiting no well-defined yield stress, but at higher strain rates the stress-strain curve not only shows a well-defined yield stress but also displays a very pronounced drop in stress at yield. The flow stress is found to increase with increasing strain rate, but the increase is more significant for the yield stress than for the flow stress, showing that the yield stress is more sensitive to the strain rate than the flow stress away from the yield point. Based on the experimental results, empirical strain-rate-dependent constitutive equations are recommended. The suggested constitutive equations provide a reasonable estimate of the strain-rate-sensitive behaviour of materials.

Simulation study of the effect of strain rate on the mechanical properties and tensile deformation of gold nanowire

2017 ◽  
Vol 31 (27) ◽  
pp. 1750247 ◽  
Author(s):  
Guo-Jie Shi ◽  
Jin-Guo Wang ◽  
Zhao-Yang Hou ◽  
Zhen Wang ◽  
Rang-Su Liu
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
High Strain ◽  
Strain Curve ◽  
Deformation Mechanisms ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Au Nanowire ◽  
Plastic Process

The mechanical properties and deformation mechanisms of Au nanowire during the tensile processes at different strain rates are revealed by the molecular dynamics method. It is found that the Au nanowire displays three distinct types of mechanical behaviors when tensioning at low, medium and high strain rates, respectively. At the low strain rate, the stress–strain curve displays a periodic zigzag increase–decrease feature, and the plastic deformation is resulted from the slide of dislocation. The dislocations nucleate, propagate, and finally annihilate in every decreasing stages of stress, and the nanowire always can recover to FCC-ordered structure. At the medium strain rate, the stress–strain curve gently decreases during the plastic process, and the deformation is contributed from sliding and twinning. The dislocations formed in the yield stage do not fully propagate and further escape from the nanowire. At the high strain rate, the stress-strain curve wave-like oscillates during the plastic process, and the deformation is resulted from amorphization. The FCC atoms quickly transform into disordered amorphous structure in the yield stage. The relative magnitude between the loading velocity of strain and the propagation velocity of phonons determines the different deformation mechanisms. The mechanical behavior of Au nanowire is similar to Ni, Cu and Pt nanowires, but their deformation mechanisms are not completely identical with each other.

scholarly journals The High Strain Rate Dynamic Stress-Strain Curve for OFHC Copper

2003 ◽  
Vol 52 (9Appendix) ◽  
pp. 187-195
Author(s):  
Michael. E. STEVENSON ◽  
Stanley. E. JONES ◽  
Richard. C. BRADT
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Dynamic Stress ◽  
High Strain ◽  
Strain Curve ◽  
Ofhc Copper ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Rate Dynamic
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