Material Properties and Testing

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What is a stress-strain curve?

A stress-strain curve is a graph that shows the relationship between stress and strain for a material, depicting how it reacts to external forces.

Describe the process of tensile testing.

Tensile testing involves applying a controlled axial load to a material specimen until it fails to determine the material's mechanical properties such as tensile strength, yield strength, and elongation.

What does a material's toughness indicate?

Toughness is the ability of a material to absorb energy and plastically deform without fracturing. It is a measure of how much energy a material can absorb before breaking.

How is hardness measured?

Hardness is often measured by indentation tests, where a hard indenter is pressed into the surface of a material to determine resistance to deformation (e.g., Brinell, Vickers, Rockwell tests).

What is fatigue in materials?

Fatigue is the weakening or failure of a material caused by cyclic loading, leading to the formation of cracks and eventual breakage over time.

Define the term 'creep' in material science.

Creep is the slow, progressive deformation of a material under constant stress over time, typically at high temperature.

What is 'fracture toughness'?

Fracture toughness is a property that describes a material's ability to resist crack propagation. It quantifies the fracture resistance of a material in the presence of flaws.

Explain what an impact test measures.

An impact test determines a material's ability to absorb energy at high deformation rates, indicating its toughness and notch sensitivity (e.g., Charpy, Izod tests).

Why is the microstructure of a material important?

The microstructure of a material, which includes elements such as grain size and phase distribution, greatly affects its mechanical properties and suitability for various applications.

Describe the term 'anisotropy' in materials.

Anisotropy refers to the direction dependency of a material's properties, meaning properties vary based on the direction of measurement.

What is the significance of the elastic modulus?

The elastic modulus quantifies a material's elasticity or stiffness, indicating how much it will stretch or compress under a given stress within its elastic limit.

How does work hardening occur?

Work hardening, or strain hardening, occurs when a metal is deformed plastically, increasing dislocation density that strengthens the material by impeding further dislocation motion.

What is thermal expansion in materials?

Thermal expansion is the tendency of a material to change shape, area, or volume in response to a change in temperature.

Define ‘isotropy’ as it pertains to materials.

Isotropy refers to the uniformity of material properties in all directions, meaning the properties do not depend on the direction of measurement.

What role do defects play in the properties of materials?

Defects, like vacancies, dislocations, and impurities, can significantly affect the mechanical and physical properties of a material, often serving as stress concentrators or altering conductivity and strength.