5 Written questions
5 Matching questions
- Why is the ultimate tensile strength sometimes less than the maximum stress?
- (T/F) Stiffness of a dental prosthesis can increase by increasing its thickness.
- A value of 0.3 for Poisson's ratio is typical. Thus, the shear modulus is usually about ___% of the elastic modulus.
- Poisson's ratio
- which tooth structure has the hgiher <b>propotional limit</b> and <b>modulus of elasticity</b>?
- a the ratio of horizontal extension to vertical compression.
Most engineering materials have values of approximately <b>0.3</b>
- b 38%
- c True
however, the <b>elastic modulus</b> is always a constant. never changes! it describes material's <b>relative</b> stiffness.
- e Because of the reduction in area, the force required to increase deformation actually decreases.
5 Multiple choice questions
- The relative amount of elastic energy per unit volume released on unloading of a test specimen.
- b. parallel
brackets for braces is a good example
the term resilience is associated with 'springiness'
- Maximum shear stress at the point of fracture of a test specimen.
maximum elastic stress (proportional limit)
5 True/False questions
Compressive strength → Ratio of compressive force to cross-sectional area prependicular to the axis of applied force.
in most cases fracture occurs because of the _____ stress component.
c. shear → b. tensile
Strength depends on what factors: (4) → 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
Why do prostheses sometimes fail under a very small force, even though the strength of the prosthetic material is relatively high? → flexible
The <b>maximum flexibility</b> is defined as the flexural strain that occurs when the material is stressed to its proportional limit.
a different property, __________, is used in such cases when the proportional limit cannot be determined with sufficient accuracy. →
is a property that represents the stress value at which a small amount (0.1% or 0.2%) of plastic strain <b>has occurred</b>.
Does not exist for very brittle materials