5 Written questions
5 Matching questions
- Percent elongation
- Two important aspects of microscopic flaws in brittle materials:
- When a metal had been stressed beyond its proportional limit, the hardness and strength of the metal ________ at the area of deformation.
- 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__________.
- a resilience
the term resilience is associated with 'springiness'
- b Force per unit area within a structure subjected to an external force or pressure (See Pressure).
- c Maximum amount of plastic strain a tensile test specimen can sustain before it fractures (See Ductility).
- d a. increases
although ductility of the metal ↓↓
- e 1. the stress intesntiy at these flaws increases with the length of the flaw, specially when it is oriented prependicular to the direction of tensile stress
2. flaws on the surface are associated with higher stresses than are flaws of the same size in interior regions.
5 Multiple choice questions
- 1. the <i>percent elongation</i> <b>after</b> fracture.
2. the <i>reduction in area </i>of the tensile test specimen
3. the max # of bends performed in a cold bend test.
- Ultimate strength
dentin → 50 MPa
enamel → 10 MPa
- a. low impact
• The <b>stress</b> at which a test specimen exhibits a specific amount of plastic strain (0.2%)
• The YS at 0.2% strain offset from the origin is 1536 MPa in this case.
5 True/False questions
Flexural stress (Bending stress) →
Force per unit area at the point of fracture of a test specimen subjected to flexural loading.
if stress/strain value is very small the materials are said to be: →
by comparing the <b>area</b> underneath the elastic region.
↑ the area = ↑ resilience
True stress → Ratio of applied force to the actual cross-sectional area; however, for convenience stress is often calculated as the ratio of applied force to the initial cross-sectional area.
average biting force → The relative amount of elastic energy per unit volume released on unloading of a test specimen.
___________represents the ability of a material to sustain a large permanent deformation under a <b>tensile</b> load before it fractures. → mealibility