Mats Lecture 11-12 Flashcards
Mechanical Properties of Materials
What is the formula for stress?
(Applied Force)/Area Supporting Force
What is the formula for strain?
(amount object stretches)/length of object
What is normal stress and normal strain?
-when an applied force, F is acting normal (perpendicular) to the area A
-Can be tensile or compressive
What is the definition of Elastic Strain?
fully recoverable strain resulting from an applied stress
What is Shear Stress and Shear Strain?
-When an applied force is acting parallel to the area
What is Hydrostatic Stress and Dilation?
-When there is a uniform pressure, P applied in all directions to a body of initial volume V
What happens to a material when it is stretched elastically in one direction?
-The material will contract in the transverse directions in order to maintain a constant volume
-This is measured by Poisson’s ratio
List the methods used to measure mechanical properties
-Tensile test
-Shear test
-Flexural test
What does the tensile test measure?
-The resistance of a material to a static or slowly applied force
Define what strain rate is
-The rate at which strain develops in a material
Define elastic deformation
-When a material deforms during loading, but returns to its original shape when load is released
What is elastic modulus also known as?
-Young Modulus
What does the elastic modulus measure?
-Measures a material’s resistance to elastic deformation
What is the formula for elastic modulus?
(stress)/strain
List examples of materials with high elastic modulus
-Metals
-Steel
-Titanium
-Nickel
-Diamonds
List examples of materials with low elastic modulus
-Rubber
-Polymers
-Nylon
Define what plastic deformation is
-When a material deforms during loading and undergoes permanent shape change (it does not return to its original shape upon unloading)
Define yield stress
-The stress at which a material yields is called yield stress (or strength)
List examples of materials with high yield stress
-Metals
-Steel
-titanium
-nickel
-diamond
List examples of materials with low yield stress
-Rubber
-Polymers
-Nylon
What happens when a material is deformed enough?
it fails (breaks)
What is the definition of Ultimate Tensile Strength?
-The maximum stress after which the material starts to fail
What is the definition of Ductility?
-Ability of a material to deform plastically
What is the definition of Toughness?
-The energy absorbed by a material before it breaks
What is toughness graphically?
-The area under the stress-strain curve
What is the definition of fracture toughness? What symbol is it denoted by?
-The resistance of materials to cracking and fracture
-KIC
What are materials with high KIC called?
Ductile
What are materials with low KIC called?
-Brittle
