Need Answer to these questions: 1)Elastic modulus is related to____ (a) Interato

Question

Need Answer to these questions:

1)Elastic modulus is related to____ (a) Interatomic bond forces (b) Stiffness (c) A and B

2). On an engineering stress-strain curve, the onset of plastic instability occurs at (yield stress, tensile strength, fracture strength).

3)During a tensile test, (necking, yield, fracture) begins at the ultimate tensile strength

4)Polymers and rubbers do not show the strain hardening in the stress-strain curve. (true, false)

5)Environmentally Induced Fracture is a time independent stress-strain behavior. (a) True (b) False

Explanation / Answer

Answers:

1) (b) Stiffness

Explanation: Elastic modulus is called Young's modulus. You have to consider geometrical parameters to calculate the young's modulus. In fact, the young's modulus is related to the intrinsic mechanical properties of the material (independantly of its geometry) while the stiffness is commonly associated to the properties of a structure.
Stiffness classicaly corresponds to a ratio between force and length change while young's modulus is calculated with stress (Force/Area) and strain (Elongation/initial length)

2). On an engineering stress-strain curve, the onset of plastic instability occurs at tensile strength

Explanation:The tensile strength is important from both design and scientific viewpoints. It is related to the maximum nominal stress (UTS) that a material can sustain in tension, it occurs at the point where necking begins, and it has a number of interesting and useful empirical relationships to other properties. If a true stress-true strain curve could be obtained directly from a tensile test, instead of an engineering stress-strain curve, one would find that there is no maximum stress prior to failure and therefore there would appear to be no UTS.

3)During a tensile test, necking begins at the ultimate tensile strength

Explanation: Tensile test  is related to the maximum nominal stress (UTS) that a material can sustain in tension, it occurs at the point where necking begins, and it has a number of interesting and useful empirical relationships to other properties.

4)Polymers and rubbers do not show the strain hardening in the stress-strain curve. FALSE

Explanation: Only Polymers shows the strain hardening in the stress-strain curve

5)Environmentally Induced Fracture is a time independent stress-strain behavior. (a) True

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