Question

The life of a machine component under heavy test load was 10 hrs. The life under combined loading was 18 hrs, out of which 9.8 hrs was at heavy load and 8.2 hrs was at the normal load. The expected life under the normal operating load is

• A. 6 hrs
• B. 54.5 hrs
• C. 410 hrs
• D. 490 hrs

Answer 1

The correct option is C 410 hrs

$\text{Heavy load =}{\sigma }_1$

$L_1=10hrs$

$\text{Normal load =}{\sigma }_2$

$L_2=?$

$n_1=9.8hrs$

$n_2=8.2hrs$

$\frac{n_1}{L_1}+\frac{n_2}{L_2}=1$

$\frac{9.8}{10}+\frac{8.2}{L_2}=1$

$\Rightarrow L_2=410hrs$