Material properties

Question 1

What is strain rate and how does it affect a material?

Answer 1

Strain rate is the rate of applied load
1. At slow rates, material is more ductile
2. At fast rates, material is more brittle

Question 2

How does temperature affect a material?

Answer 2

At high temperature, a material is more ductile.
At low temperature, a material is more brittle.

Question 3

What is degree of triaxiality and how does it affect a material?

Answer 3

Degree of triaxiality is the amount of axes of an applied load.

1. When you have a higher degree of triaxiality = the Poisson effect is negated = material has less room to expand in perpendicular axis to applied load = material is more brittle
2. When you have a lower degree of triaxiality = the Poisson effect allows the material to expand in perpendicular axis to applied load = material is more ductile

Question 4

What is stress?

Answer 4

Stress = Force / Area

Question 5

What is strain?

Answer 5

Strain = Deformation (delta L) / Original length

Question 6

What are the Engineering terms on a stress-strain graph?

Answer 6

1. Elastic region
2. Modulus of elasticity
3. Yielding stress
4. Strain-hardening region
5. Ultimate stress
6. Necking region
7. Failure stress

Question 7

What is the difference between engineering stress and true stress?

Answer 7

1. Stress = Force / Area
2. Engineering stress takes the original cross-sectional area of the specimen
3. In reality, the cross-sectional area reduces when necking occurs
4. Atrue < Aeng
5. Stresstrue > Stresseng

Question 8

Why is yield stress more important to engineers?

Answer 8

1. Yield stress is when material is permanently deformed
2. Permanent deformation is considered a failure in the real world
3. Engineers want to operate underneath that yielding stress to prevent accidents
4. For example, when a concrete structure is at yielding stress, people have time to evacuate before the building collapses at ultimate stress

Question 8

Why is yield stress more important to engineers?

Answer 8

1. Yield stress is when material is permanently deformed
2. Permanent deformation is considered a failure in the real world
3. Engineers want to operate underneath that yielding stress to prevent accidents
4. For example, when a concrete structure is at yielding stress, people have time to evacuate before the building collapses at ultimate stress

Question 9

What happens to the ductility of steel in the following
conditions:
1. Increasing the rate of applied strain
2. Increase the material temperature
3. Increasing the degree of triaxiality

Answer 9

1. Ductility decreases, material becomes more brittle
2. Ductility increases
3. Ductility decreases, material becomes more brittle

Question 10

What is the difference between deformation and strain?

Answer 10

1.Deformation is the physical length change of the material (delta L)
2. Strain is the proportion between the length change tp the original length