An annealed 65 - 45- 12 cast iron structural member is non-destructively hardness tested. In the hardness test, a 10 mm diameter tungsten carbide sphere created a 4.48 mm diameter impression under a 3000 kg load. What is the yield strength (to 2 significant figures) of the structural member

The required yield strength YS is 350 MPa

Explanation:  

Given that;

for an annealed 65 - 45- 12 cast iron structural member,

indenter used : WC ball

Diameter of the indenter D = 10 mm  

Diameter of impression d = 4.48  

Load = 3000 kg  

Now, the Brinell Hardness Number BHN can be determined by using the following formula;

BHN = 2P / (πD[ D - √( D² - d²))

we substitute

BHN = 2(3000) / (π×10[ 10 - √( 10² - 4.48²))

BHN = 6000 / 10π[ 10 -  8.9403]  

BHN = 6000 / 33.2914      

BHN = 180.22 ≈ 180

Corresponding values to BHN = 180

Yield Strength Y.S = 350 MPa

Tensile Strength T.S = 490 Mpa

do you have any options?