Mechanical Properties of Matter Flashcards
Mechanical Properties
Changes in material that result when force is applied
Stress
Tendency to change the position of rest or motion of a mass
Strain
Deformation occurs if the position or motion of the mass cannot be changed
What are the 3 types of stresses?
tensile, compression, shear
Elastic Strain
Reversible strain
What is Hooks Law?
Elastic Strain which is reversible type of strain
Non-permanent deformation (ex:spring)
Plastic strain
Permanent deformation
Elastic modulus = Young Modulus
Slope of the stress/strain curve indicates rigidity or stiffness
(only within the elastic range)
Elastic Limit = Proportional Limit = Yield Strength
Where permanent deformation begins
Ultimate strength
Point of actual fracture
Resilience
Energy needed to deform a material to its elastic limit; resistance to permanent deformation;
area under elastic portion of stress-stain curve
Toughness
Energy needed for fracture; area under elastic an plastic portions of stress/strain curve
Hardness
Resistance to indentation and scratching
How is hardness tested?
Hardness is tested by the diameter of depression based on the stylus and force used (Brinell, Knoop, Vickers #’s)
Rheology
Flowability = relative viscosity
Abrasion Resistance
Can be experimentally tested with toothbrush abrasion lab machines to stimulate oral conditions.
May involve factors of resilience and toughness.
Wear is often related to surface hardness
