A special notched tensile specimen to determine the flow stress-strain curve of hardening materials without applying the Bridgman correction

2017 ◽  
Vol 179 ◽  
pp. 225-239 ◽  
Author(s):  
Shengwen Tu ◽  
Xiaobo Ren ◽  
Bård Nyhus ◽  
Odd Magne Akselsen ◽  
Jianying He ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Curve ◽  
Tensile Specimen ◽  
Stress Strain Curve ◽  
Stress Strain

Fracture Assessment of Pipes Having Multiple Flaws Based on Ramberg–Osgood-Type Stress–Strain Relationships

2011 ◽  
Author(s):  
Hideo Machida ◽  
Tetsuya Hamanaka ◽  
Yoshiaki Takahashi ◽  
Katsumasa Miyazaki ◽  
Fuminori Iwamatsu ◽  
...  
Keyword(s):  
Flow Stress ◽  
Stress Concentration ◽  
Fracture Strength ◽  
Strain Curve ◽  
Assessment Method ◽  
Experimental Results ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Strain Relationship ◽  
Fracture Assessment

This paper describes a fracture assessment method for a pipe having multiple circumferential flaws. According to Fitness-for-Service (FFS) codes for nuclear facilities published by the Japanese Society of Mechanical Engineers (JSME), the fracture strength of a high-ductility pipe having a circumferential flaw is evaluated using the limit load assessment method assuming the elastic–perfectly-plastic stress–strain relationship. In this assessment, flow stress is used as a proportional stress. However, previous experimental results [1, 2, 3] show that a crack penetrates before the entire flawed pipe section reaches the flow stress. Therefore, stress concentration at a flaw was evaluated on the basis of the Dugdale model [4], and the fracture strength of the crack-ligament was evaluated. This model can predict test results with high accuracy when the ligament fracture strength is assumed to be tensile strength. Based on this examination, a fracture assessment method for pipes having multiple flaws was developed considering the stress concentration in the crack-ligament by using the realistic stress–strain relationship (Ramberg–Osgood-type stress–strain curve). The fracture strength of a multiple-flawed pipe estimated by the developed method was compared with previous experimental results. When the stress concentration in the crack-ligament was taken into consideration, the fracture strength estimated using the Ramberg–Osgood-type stress–strain curve was in good agreement with experimental results, confirming the validity of the proposed method.

Mechanical Behavior of Materials under Tensile Loads

2004 ◽  
pp. 13-31
Keyword(s):  
Tensile Test ◽  
Mechanical Behavior ◽  
Tensile Deformation ◽  
True Strain ◽  
Strain Curve ◽  
Tensile Specimen ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Mathematical Expressions ◽  
Reduction In Area

Abstract This chapter focuses on mechanical behavior under conditions of uniaxial tension during tensile testing. It begins with a discussion on the parameters that are used to describe the engineering stress-strain curve of a metal, namely, tensile strength, yield strength or yield point, percent elongation, and reduction in area. This is followed by a section describing the parameters determined from the true stress-true strain curve. The chapter then presents the mathematical expressions for the flow curve. Next, it reviews the effect of strain rate and temperature on the stress-strain curve. The chapter then describes the instability in tensile deformation and stress distribution at the neck in the tensile specimen. It discusses the processes involved in ductility measurement and notch tensile test in tensile specimens. The parameter that is commonly used to characterize the anisotropy of sheet metal is covered. Finally, the chapter covers the characterization of fractures in tensile test specimens.

scholarly journals Constitutive Model of 30CrMoA Steel with Strain Correction

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1214
Author(s):  
Song Zhang ◽  
Xuedao Shu ◽  
Jitai Wang ◽  
Yingxiang Xia
Keyword(s):  
Flow Stress ◽  
Constitutive Model ◽  
High Speed ◽  
Strain Curve ◽  
Material Constant ◽  
Test Machine ◽  
Experimental Stress ◽  
High Speed Train ◽  
Stress Strain Curve ◽  
Stress Strain

It is necessary to establish a constitutive model of 30CrMoA steel to optimize the forming shape and mechanical properties of high-speed train axles. The experimental stress–strain curve of 30CrMoA steel was obtained by an isothermal compression test on a Gleeble-3500 thermal simulation test machine under temperature of 1273~1423 K and strain rate of 0.01~10 s−1. Considering the effect of strain on the material constant, an empirical constitutive model was proposed with strain correction for 30CrMoA steel. In addition, the material constant in the constitutive model is determined by linear regression analysis of the experimental stress–strain curve. Comparing the theoretical value and experimental value of flow stress, the correlation R is 0.9828 and the average relative error (ARRE) is 4.652%. The constitutive model of 30CrMoA steel with strain correction can reasonably predict the flow stress under various conditions. The results provide an effective numerical tool for further study on accurate near-net forming of high-speed train axles.

A Tensile Characterization Study of Metal Sheet in Large-Strain

2006 ◽  
Author(s):  
W. J. Dan ◽  
W. G. Zhang ◽  
S. H. Li ◽  
Z. Q. Lin
Keyword(s):  
Large Strain ◽  
True Strain ◽  
Digital Camera ◽  
Strain Curve ◽  
Plastic Instability ◽  
Tensile Specimen ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Tension Tests ◽  
Tensile Experiment

A method for determining the strain-stress curve of larger-strain is proposed when plastic instability occurs in standard tension tests. Thin tested steel sheet is subjected to tension loading until fracture occurs. The deformation process is captured with a digital camera. Displacement and strain field of material deformation can be calculated by a mesh-free PIM method. A tensile experiment is simulated to verify that local measuring stress-strain curve by PIM method near the center of the specimen can describe a full stress-strain curve clearly. Numerical simulation results, at different location along the specimen axial, present that different parts of specimen have different deformation distribution in tensile and the center fracture part of tensile specimen is the only region which can experience full strain. The true stress- true strain curves, based on the estimated parameters, are validated in all strain regions by comparison with curves from standard tension tests. The measured curves by PIM method are very stabilization. Compared with several material constitutive equations, The Swift’s equation is very close to experiment curve at plastic deformation.

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.

Multi-Phase-Field Analysis of Stress–Strain Curve and Ferrite Grain Formation during Dynamic Strain-Induced Ferrite Transformation

2014 ◽  
Vol 626 ◽  
pp. 81-84
Author(s):  
Akinori Yamanaka ◽  
Tomohiro Takaki
Keyword(s):  
Flow Stress ◽  
Phase Field ◽  
Volume Fraction ◽  
Strain Curve ◽  
Dynamic Strain ◽  
Stress Strain Curve ◽  
Stress Strain ◽  
Ferrite Transformation ◽  
Multi Phase ◽  
Strain Induced Ferrite Transformation

A numerical model of dynamic strain-induced ferrite transformation (DSFT) was developed by combining the multi-phase field model with the Kocks–Mecking model. Using the developed model, a three-dimensional simulation of the DSFT in a Fe-C alloy was performed to study the correlation between the variation in flow stress and the microstructure evolution during the DSFT. The simulation results indicated that the developed model successfully simulated the characteristic DSFT behavior, i.e., both the stress–strain curve with a single peak and the formation of an ultrafine-grained ferrite microstructure. The variation in the flow stress during the DSFT was characterized by the volume fraction of the ferrite phase.

Sign in / Sign up

Export Citation Format

Share Document