Answer Happy

b) Derive an expression for relating time to failure to applied stress and explain how it relates to a SPT (survival-Probability-Time diagram) 5 a a c) Figure 1 shows a SPT diagram for a dental porcelain. Explain the significance of the points marked 133 and 47MPa, and 98 and 35MPa in terms of failure probability and survival time. Comment on the implications for the use of this material in the oral environment. (Id=1 day, la = 1 year, 50a = 50 years) 5

Fracture strength (MPa) 21 65 90 2 245 99 SA (50a of 93.4 47/MPa 63.2 Inin( 1/(1-P) Failure probability 30.8 12.7 23 35 MPa 98 kPa 1.8 5.5 2.5 4 4.5 Frachse strength inca in NPB) Figure 1 SPT diagram of a dental porcelain