# Conditions for composite bar

Q.  In the diagram shown below, material A and B expand freely as shown in condition (2). If expansion is prevented for equilibrium condition(3) to reach, then
- Published on 21 Sep 15 a. tensile force exerted by material B on A is equal to tensile force exerted by A on B.
b. tensile force exerted by material B on A is equal to compressive force exerted by A on B.
c. compressive force exerted by material B on A is equal to tensile force exerted by A on B.
d. no force acts on the composite member in equilibrium conditions

ANSWER: tensile force exerted by material B on A is equal to compressive force exerted by A on B.

#### Discussion

• Sravanthi   -Posted on 24 Nov 15
- In equilibrium condition, tensile force exerted by material B on A is equal to compressive force exerted by A on B.

- Material B expands more, hence it has high coefficient of thermal expansion and material A has low coefficient of thermal expansion.

- Therefore to achieve equilibrium condition, the material A is exerted by tensile force and material B is exerted by compressive force.

- Hence, tensile force exerted by material B on A is equal to compressive force exerted by A on B.

- [αtL + (PL/AE)]material A = [αtL – (PL/AE)]material B

- [Elongation due to temperature + elongation due to tensile force]A = [Elongation due to temperature + elongation due to compressive force]B

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