Question

plastic flow begins just after the proprtionality limut. true or false​

Answer 1

Answer:

false......is the answer mate..

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Answer 2

Explanation:

The proportional limit is the maximum stress that a dental material sustains without any deviation, or the magnitude of elastic stress above which plastic deformation occurs. Below the proportional limit, no permanent deformation occurs; and when the stress is removed, the structure returns to its original dimension. Proportional limit (PL) can be easily deciphered

In preceding figure, as the stress increases, the strain also increases. From O to A, a linear relation is established between stress and strain. As the stress doubles, the strain also doubles. After point A, no linear proportional relation is maintained between stress and strain. Here, the value “A” is identified as the proportional limit. So, the proportional limit is defined as the highest stress at which the stress-strain curve is a straight line. Below the proportional limit, there is no permanent deformation in a structure, that is, the object returns to its original position after the removal of applied force. Thus, the material is elastic in nature below the proportional limit, and the curve before the proportional limit is called the “elastic region,” and above the proportional limit, is called the “plastic limit.” The connectors of plastic dentures should have a high proportional limit. Materials such as cobalt/chromium (alloy) have high proportional limits; thus, they should be used to fabricate connectors, because they can withstand high stresses without permanent deformation.

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