Material Testing and Properties Flashcards
(25 cards)
What does tensile testing avoid in order to perform an accurate test?
Avoids high or non uniform stress being generated.
What variables are measured during a tensile test?
Force and extension of test piece.
What is the formula and units for engineering stress?
Stress = Force/ Cross sectional area
Pascals
What is the formula for engineering strain?
Strain = Change in length/ Original length
What is the formula for young’s modulus? And what are the units?
Youngs modulus, E = Stress/ Strain
Pascals.
What affect does temperature have on youngs modulus?
Higher temp means lower youngs modulus.
What is the formula for poisson’s ratio?
Poissons ratio = Lateral strain/ longitudinal strain
Why is it difficult to tensile test ceramics?
They are very brittle.
What is the definition of hardness and what is it related to?
Ability to resist scratching/ surface indentation.
Related to a metals tensile and yield strength.
What type of hardness test leaves a circular indentation?
Brinell Test
What are the four hardness tests?
Brinell, Vickers, Knoop and rockwell.
What is the formula for brinell hardness?
Brinell hardness = applied load (kg) / surface area of impression
What is the definition of toughness?
The ability of a material to absorb energy.
High toughness generally means a material has high _____ and _____ ?
strength and ductility.
Low toughness usually means a material is ______ ?
Brittle.
What are 2 methods of testing toughness?
Izod and charpy impact tests.
Briefly describe the impact toughness test.
A pendulum swings and breaks a test sample. The height the pendulum reaches after it breaks the sample is measured.
Relationship between temp and E value?
high temp = low E value
Relationship between temp and yield/tensile strength?
high temp = reduced strength
Relationship between temp and hardness?
high temp = low hardness
Relationship between temp and ductility?
higher temp = higher ductility.
If a material is brittle will it fracture suddenly or slowly?
Suddenly.
If a fracture occurs within a ductile material, will the crack be sharp or blunt?
Blunt.
What manufacturing defects can cause fracture?
Porous casting, surface scratches.
