Engineering stress-strain units are based on the starting dimensions of the tensile test sample: Engineering stress is the load divided by the starting cross-sectional area, and engineering strain is the change in length relative to the starting gauge length (2 inches, 50mm, or 80mm for ASTM [ISO I], JIS [ISO III], or DIN [ISO II] tensile test samples, respectively.)

Metals get stronger with deformation through a process known as strain hardening or work hardening. This is represented on the stress strain curve by the parabolic shaped section after yielding.

Concurrent with the strengthening as the tensile test sample elongates is the reduction in the width and thickness of the test sample. This reduction is necessary to maintain consistency of volume of the test sample.

Initially the positive influence of the strengthening from work hardening is greater than the negative influence of the reduced cross-section, so the stress-strain curve has a positive slope. As the influence of the cross-section reduction begins to overpower the strengthening increase, the stress-strain curve slope approaches zero.

When the slope is zero, the maximum is reached on the vertical axis of strength. This point is known as the ultimate tensile strength, or simply the tensile strength. The strain at which this occurs is known as uniform elongation.

Strain concentration after uniform elongation results in the formation of diffuse necks and local necks and ultimately fracture.

Figure 1: Tensile Strength is the Strength at the Apex of the Engineering Stress – Engineering Strain Curve

Figure 1: Tensile Strength is the Strength at the Apex of the Engineering Stress – Engineering Strain Curve.

Related Posts
Filter by
Post Page
Testing and Characterization homepage-featured-top main-blog Blog Steel Grades AHSS 1stGen AHSS Press Hardened Steels Forming Metallurgy Tailored Products Simulation Springback
Sort by

Tensile Testing

topofpage

18

Additive Manufacturing

Additive Manufacturing (AM) has been associated with the future of manufacturing since its inception. While it does

8

Vision for Industry 4.0 in Sheet Metal Forming

There is interest in the sheet metal industry on how to adopt Industry 4.0 into their legacy forming practices to

8

Press Hardened Steels Primer

PHS and PQS Overview A Brief Overview of Press Hardening Press hardening (also commonly

8

Defining Steels

There are different ways to classify automotive steels. One is a metallurgical designation providing some process

8