Calculations Flashcards
What is the definition of loading in materials testing?
The act of applying a force to a material.
List the five forms of loading.
- Compression
- Tension
- Shear
- Torsion
- Bending
Who discovered Hooke’s law and in what year?
Robert Hooke in 1660.
What does Hooke’s law state?
The size or displacement of the deformation is directly proportional to the deforming force or load.
How can Hooke’s law be mathematically expressed?
F = -kX
What do the variables in Hooke’s law represent?
- F = force applied
- X = elongation of the spring
- k = spring constant
What is Young’s modulus?
A numerical constant that describes the elastic properties of a solid undergoing tension or compression.
Young’s modulus is equal to what ratio?
Longitudinal stress divided by strain.
What are the units of Young’s modulus in the English and metric systems?
- English: pounds per square inch (psi)
- Metric: newtons per square metre (N/m²)
What is the formula for stress?
σ = F/A
What does stress represent in materials?
The ratio of the applied force to the cross-sectional area of the material.
Define strain.
The ratio of the change in dimension to the initial dimension of the metal.
What are the three types of strain?
- Normal strain
- Volumetric strain
- Shear strain
What is the formula for calculating strain?
ε = (l - lo) / lo
What does the stress–strain curve show?
The deformation in a material when a load is applied gradually.
What are the three stages of a stress–strain curve for ductile materials?
- Linear elastic region
- Strain hardening region
- Necking region
What is the ultimate tensile strength (UTS)?
The maximum stress a specimen can sustain.
What happens to a material after reaching yield strength?
It loses elasticity and exhibits plasticity.
What does the area under the stress–strain curve represent?
The energy absorbed by the material during deformation.
What does a green stress–strain curve color indicate?
A brittle material that is strong with little strain for high stress.
What does a black stress–strain curve color indicate?
A strong material that is not ductile, like steel wires.
What does an orange stress–strain curve color indicate?
A ductile material that undergoes necking and permanent deformation.
What does a purple stress–strain curve color indicate?
A plastic material with a very small elastic region.
