Materials Exam 1

Transition between linear and non-linear behaivor

Proportional Limit

Transition between elastic and plastic behavior- Max stress with full recovery

Elastic Limit (Yield Point)

Strain continues with little or no increase in stress (after elastic limit)

Yielding

Max stress on the curve (tensile or compressive strength)

Ultimate Stress

Force times distance

Work (or energy)

Energy required to reach yield point

Modulus of Resilience

Energy required to fracture

Toughness

Point where specimen fractures or ruptures

Rupture Stress

Has little plastic deformation before failure (glass, concrete)

Brittle Material

Has lots of plastic deformation before failure (structural steel, rubber)

Ductile Material

Resistance to flow (for linear materials

Viscosity

Has both elastic and viscous response and delayed response. Deformation depends on Duration of load, Rate of loading, A quick shock or pulse may cause little deformation, while a sustained load can cause much deformation, Temperature

Viscoelastic Materials

Long term deformation under constant load. (Intersections, Asphalt and Portland Cement over decades)

Creep

Mechanical behavior of all materials (High temp = ductile, Low temp = brittle)

Temperature affects what?

Toughness at different temperatures

Impact Fracture test measures?

A change of only a few degrees

Viscoelastic materials like asphalt and polymers are greatly influenced by?

A much greater temperature change but are similarly affected

Metals require?

All materials expand and contract with temperature. Alot of CTE = alot of expansion

Thermal Expansion

Failure stress / applied stress proportional to cost and is chosen by (Cost, material variability, accuracy in considering all loads, possible misuse accuracy in measuring material response

Factor of Safety

An alloy of iron and carbon

What is Steel?

Heating and then slowly cooling to room temp. Steel gets softer and more ductile, increasing toughness

What is Annealing?

Hotter and air cooled. Gives uniform, fine grained structure. Provides high fracture toughness, more corrective rather than strengthening or hardening.

What is Normalizing?

Hotter, rapid cooling by water/brine/oil. Steel is harder and more brittle.

What is Hardening?

Reheating. Increases ductility and toughness

What is Tempering?