Materials Science Flashcards

Young's modulus (modulus of elasticity) is defined as:

Answer: Stress divided by strain in the elastic region

Young's modulus E = σ/ε applies only in the linear elastic region where Hooke's Law holds.

What is the approximate Young's modulus for structural steel?

Answer: 200 GPa

Steel has a Young's modulus of approximately 200 GPa (207 GPa), a standard value used in structural engineering calculations.

In a Brinell hardness test, hardness is determined by:

Answer: Measuring the diameter of a spherical indentation from a hardened ball

Brinell hardness (BHN) is calculated from the applied load and the area of the indentation left by a hardened steel or tungsten carbide ball.

What does a standard Charpy impact test measure?

Answer: Energy absorbed during fracture of a notched specimen

The Charpy test measures the energy absorbed when a notched bar is struck by a swinging pendulum, assessing toughness and ductile-to-brittle transition.

The endurance limit in fatigue testing is best described as:

Answer: The stress amplitude below which a material can theoretically endure infinite cycles

For ferrous alloys, the endurance limit is the stress amplitude below which fatigue failure will not occur regardless of the number of cycles, seen as the horizontal asymptote on an S-N curve.

A material that undergoes significant plastic deformation before fracture is classified as:

Answer: Ductile

Ductile materials exhibit large plastic deformation (necking, high percent elongation) prior to fracture, absorbing significant energy.

Percent elongation in a tensile test is used to quantify:

Answer: Ductility of the material

Percent elongation = [(Lf - L0)/L0] × 100% measures how much a specimen permanently stretches before fracture, quantifying ductility.