Manufacturing process II. Sándor Pálinkás Ph. D Manufacturing process II. Sándor Pálinkás Ph.D. assistant lecturer University of Debrecen, Faculty of Engineering, Department of Mechanical Engineering 3. Lecture 2015/2016 Semester II.

Tensile test

Upsetting test Engineering stress: Engineering strain:

Upsetting test

Upsetting test Barreling phenomenon:

Types of Stress-Strain Relationships In uniaxial tension tests of most metals (and many other materials), the following phenomena can be observed. If the stress in the specimen is below the yield stress of the material, the material behaves elastically and the stress in the specimen is proportional to the strain. If the stress in the specimen is greater than the yield stress, the material no longer exhibits elastic behavior, and the stress-strain relationship becomes nonlinear.

Types of Stress-Strain Relationships Perfectly elastic: Brittle materials such as glass, ceramics, cast irons etc show only perfectly elastic behavior. There is very negligible yielding. Hooke’s law governs the stress-strain relation. Stiffness of such material is indicated by E. Rigid plastic, has infinite value of E, Once stress level reaches yielding Y, it continues to deform at same stress level. Elastic, perfectly plastic is combination of perfectly elastic and rigid plastic. This material will undergo elastic recovery upon unloading. Metals heated to high temperature behave this way. Lead has elastic, perfectly plastic at room temperature. Elastic, linearly strain hardening material, It approximates many of engineering materials. Such material has linear elastic behavior and linear plastic behavior. Due to strain hardening, the flow stress increases with increasing strain.

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