Mechanical property most desirable for tools and machine members in service For materials used in tools and machine components, which fundamental property is most desirable so that parts return to original shape after load removal?

Introduction / Context:
Tools and machine elements operate under repeated and sometimes fluctuating loads. The first requirement is that the component should recover its original dimensions after these loads are removed. This question targets the key mechanical property that ensures such recoverable deformation in service.

Given Data / Assumptions:

• Service involves elastic loading without permanent set.
• Standard property definitions from mechanics of materials are used.

Concept / Approach:
Elasticity is the ability of a material to deform under load and completely recover its original shape upon unloading, provided stresses remain within the elastic limit. While other properties are important for specific manufacturing routes (plasticity and malleability) or applications (ductility, creep resistance), the universal in-service requirement for dimensionally stable tools and machine members is elasticity.

Step-by-Step Solution:
Define elasticity: reversible strain up to the elastic limit.Relate to service: machine parts must function without permanent deformation during normal operation.Hence, among the listed options, elasticity is the most generally desirable property for in-service performance.

Verification / Alternative check:
Design calculations for shafts, beams, springs, and frames rely on elastic theory (Young’s modulus, shear modulus), emphasizing elastic recovery under load.

Why Other Options Are Wrong:

• Plasticity and malleability: desirable for forming operations, not for in-service shape retention.
• Ductility: valuable for toughness and forming, but not the primary criterion for shape recovery.
• Creep resistance: crucial at high temperatures; not the general baseline requirement for room-temperature service.

Common Pitfalls:
Confusing manufacturability properties (plasticity, malleability) with service properties (elasticity). A component may need both, but elasticity governs in-use dimensional stability.

Final Answer:
Elasticity