(1) Material Properties Flashcards
What are intrinsic and extrinsic properties?
Intrinsic properties do not depend on the amount or shape of the material (e.g., Young’s modulus, electrical resistivity), while extrinsic properties do depend on these factors (e.g., bending stiffness, electrical resistance).
What is Young’s modulus, and how is it measured?
Young’s modulus (E) is a measure of stiffness, representing the ratio of stress to strain in elastic deformation. It is measured in Pascals (Pa), often in GPa.
What is the difference between engineering stress and true stress?
Engineering stress is based on the original cross-sectional area, while true stress accounts for changes in the cross-sectional area during deformation.
Define Poisson’s ratio and its significance.
Poisson’s ratio (ν) is the ratio of transverse strain to longitudinal strain, indicating how a material contracts in perpendicular directions when stretched. Its theoretical maximum is 0.5.
What are the key elastic moduli?
The key elastic moduli are Young’s modulus (E), shear modulus (G), and bulk modulus (K), which measure stiffness in tension, shear, and uniform compression, respectively.
How is the yield strength determined?
Yield strength is the stress at which a material begins plastic deformation. It can be determined by the offset method, drawing a line parallel to the elastic portion at a specified strain.
What does ductility measure?
Ductility measures the strain to failure, indicating how much a material can deform plastically before breaking.
What is toughness, and how is it related to the stress-strain curve?
Toughness is the ability of a material to absorb energy before fracturing. It is proportional to the area under the stress-strain curve.
What is the purpose of a tensile test?
A tensile test measures mechanical properties like Young’s modulus, yield strength, ultimate tensile strength (UTS), and ductility by stretching a material and recording stress-strain behaviour.
What is the ultimate tensile strength (UTS)?
UTS is the maximum stress a material can withstand, observed as the highest point on the stress-strain curve.
What does the stress-strain curve indicate about material behaviour?
The curve shows elastic deformation (straight-line region), the yield point (transition to plastic deformation), UTS, and ductility (strain to failure).
Why is standardisation important in material testing?
Standardisation ensures consistency and comparability of results across tests, using standard methods and material specifications (e.g., ISO, ASTM).
