Residual Stresses in Bimetallic Strips

It is concluded (1) that under the assumption mentioned on page 56 the residual initial stress at room temperature in the outer fiber of the invar side of the bimetallic strip ranges from 35,000 lb. per sq. in. tension to zero stress depending on the rolling hardness of the strip. The residual stress distribution over the entire cross section, was not determined. (2) With subjection of the bimetallic strip to a temperature of 600° F. for 504 hours the residual stress in the invar outer fiber is in general reduced. (3) When the bimetallic strip is considered as a homogeneous material, the proportional elastic limit in bending ranges from 39,000 to 126,000 pounds per square inch in the outer fiber if the strip is bent so as to put the steel side in tension, and ranges from 28,000 to 70,000 pounds _per square inch in the outer fiber if the strip is bent so as to put the invar in tension. The proportional elastic limit varies with the rolling hardness of the strip.