5 Written Questions
5 Matching Questions
- Shear stress
- Units of Modulus of elasticity
- diametral compression test
- Why do prostheses sometimes fail under a very small force, even though the strength of the prosthetic material is relatively high?
- fatigue failure
Repeated stresses resulting in fractures. the fracture due to fatigue occurs at stress levels well below tensile strength.
a test for tensile strength that is only used for materials that exhibit predominantly elastic deformation and little or no plastic deformation (brittle).
- c Ratio of force to the original cross-sectional area parallel to the direction of the force applied to a test specimen.
- d Flaws (could be microscopic)
- e Giganewtons per square meter (GN/m²), or gigapascals (<b>GPa</b>)
5 Multiple Choice Questions
- Plastic deformation occurs when the <b>elastic stress limit (proportional limit)</b> within the prosthesis is exceeded.
- 1. <b>strain rate</b>
2. the shape of the test speciment
3. the surface finish (control flaws)
4. the environment in which material is tested
- Compressive <b>stress</b> within a compression test specimen at the point of fracture.
note: compressive stress -Ratio of compressive force to cross-sectional area perpendicular to the axis of applied force.
- The area bounded by the elastic region is a measure of <b>resilience</b>, and the total area under the stress-strain curve is a measure of<b> toughness</b>.
- Force per unit area of a material subjected to flexural loading.
5 True/False Questions
A value of 0.3 for Poisson's ratio is typical. Thus, the shear modulus is usually about ___% of the elastic modulus. → composites followed by porcelain, PMMA, amalgam and alumina.
Stress → Force per unit area within a structure subjected to an external force or pressure (See Pressure).
Shear stress is calculated by dividing the force by the area ________ to the force direction.
b. parallel → b. parallel
brackets for braces is a good example
As the interatomic spacing increases, the internal energy increases. As long as the stress is <b>not greater than the proportional limit</b>, this <u>energy</u> is known as__________. → Toughness increases with increases in strength and ductility.
which of the dental restorative materials have the highest resilience? → composites followed by porcelain, PMMA, amalgam and alumina.