Question

A set of ceramic parts are tested and the stress required for failure is measured; the results are as follows: 152 MPa, 260 MPa, 500 MPa, 1150 MPa, 700 MPa, 640 MPa, 370 MPa, 1020 MPa, and 1590 MPa. Calculate the Weibull modulus for the material. Discuss whether the material would be a good choice if we wished to design a reasonably reliable part.

Answer 1

Weibull modulus calculation:

I have done the calculations in EXCEL, Tables are shown below, if any doubt is there please comment,

Plot graph using Ln(Ln(1/S(x)))) as Y data and Ln(x) as X data:

Hence, Weibull modulus = slope of above graph = 1.3101,

The significance of the Weibull modulus is:

Sets with very high Weibull modulus have more distinct threshold of failure which is often preferred. Sets with low Weibull modulus have a more broad range of failures. Here the Weibull modulus is less, Hence it is not a good choice for designing