Stress-Strain Flashcards
What are three characteristics of mechanical properties?
-Intrinsic to the material
-Independent of the testing conditions
-Define the material’s response to mechanical loading
What happens during strain-hardening?
Plastic deformation and dislocations in the material occur
Define stresses
Internal forces generated by external loads applied to a component
-Coordinate system dependent
-Not uniform within a solid
Define strains
Internal deformations due to applied load
Measure of elongation, compression, and shear deformations
What is the proper name for the relationship between stresses and strains?
A constitutive law
What is the formula for uniaxial stress?
Uniaxial stress = applied load/initial cross-section perpendicular to the applied load
What does a positive/negative normal stress indicate?
Positive normal stress = tension, negative normal stress = compression
Define traction vector
The force exerted by one component formed during a virtual cut onto an infinitesimally small area on the other component
Traction vectors depend on how the cut was made
What is the traction vector definition of stresses?
Tractions exerted on the plane of a small cube within the material with faces perpendicular to the Cartesian axes
What notation is used for stresses and strains?
A tensor
What stresses are present in a lap shear test using glue?
Shear stress in the xy direction which is not uniform in this case
What stresses are present in pure bending?
One principle stress which is equal to -My/I where I is the second moment of inertia
How do stresses affect bone development?
Bone architecture follows the directions of principal stresses
Bone is densest where bending stresses are highest
What is the constitutive law for linear elasticity?
Isotropic Hooke’s law - can compute stresses from strains or vice versa
What are two examples of material properties?
Poisson’s ratio and Young’s modulus