Mechanical Behavior of Materials under Tensile Loads

2004 ◽  
pp. 13-31

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.

Author(s):  
W. J. Dan ◽  
W. G. Zhang ◽  
S. H. Li ◽  
Z. Q. Lin

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.


Author(s):  
C. F. Elam ◽  
Henry Cort Harold Carpenter

The following experiments were carried out with two principal objects in view: (1) to investigate the deformation of those metals, particularly iron and steel, in which the stress-strain curve does not immediately rise at the onset of plastic distortion; (2) to determine the effect of rate of deformation on the yield and subsequent stress-strain curve. It is impossible to give an adequate summary of the literature which deals with this subject, but a bibliography is included in an appendix and some of the most important results are referred to briefly below.


2009 ◽  
Vol 37 (2) ◽  
pp. 159-174
Author(s):  
O. Ifedi ◽  
Q. M. Li ◽  
Y. B. Lu

In plasticity theory, the effective stress–strain curve of a metal is independent of the loading path. The simplest loading path to obtain the effective stress–strain curve is a uniaxial tensile test. In order to demonstrate in a plasticity laboratory that the stress–strain curve is independent of the loading path, the hydrostatic bulge test has been used to provide a balanced biaxial tensile stress state. In our plasticity laboratory we compared several different theories for the hydrostatic bulge test for the determination of the effective stress–strain curve for two representative metals, brass and aluminium alloy. Finite element analysis (FEA) was performed based on the uniaxial tension test data. It was shown that the effective stress–strain curve obtained from the biaxial tensile test (hydrostatic bulge test) had a good correlation with that obtained in the uniaxial tensile test and agreed well with the analytical and FEA results. This paper may be used to support an experimental and numerical laboratory in teaching the concepts of effective stress and strain in plasticity theory.


2009 ◽  
Vol 417-418 ◽  
pp. 569-572
Author(s):  
D.A. Cendón ◽  
Jose M. Atienza ◽  
Manuel Elices Calafat

The stress-strain curve of a material is usually obtained from the load-displacement curve measured in a tensile test, assuming no strain localisation up to maximum load. However, strain localisation and fracture phenomena are far from being completely understood. Failure and strain localisation on plane tensile specimens has been studied in this work. A deeply instrumented experimental benchmark on steel specimens has been developed. Surface strain fields have been recorded throughout the tests, using an optical extensometer. This allowed characterisation of the strain localisation and failure processes. Tests have been numerically modelled for a more detailed analysis. Preliminary results show a substantial influence of geometrical specimen defects on the strain localisation phenomena that may be critical on the stress-strain curves obtained and in the failure mechanisms.


1982 ◽  
Vol 10 (6) ◽  
pp. 263 ◽  
Author(s):  
R Horstman ◽  
KA Peters ◽  
RL Meltzer ◽  
M Bruce Vieth ◽  
R Papirno

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