Strain Rate and Temperature Sensitivity of the Crack Initiation Force in Intact Japanese Quail Eggs

Abstract

Egg shells of Japanese quail (Coturnix coturnix japonica) were subjected to controlled compression tests. The compression velocity and temperature of test were varied. The shell material was found to be both strain rate and temperature sensitive. Increasing the strain rate caused an increase in fracture force, though there appeared to be a force plateau at high strain rates. Increasing the test temperature above ambient caused a marked decline in strength of the shells. The effects were thought to be due to thermally assisted deformation in the protein matrix of the shell. Small force decrements (low force perturbations) were detected in the lower half of the elastic slope of some force-deformation curves. The perturbations were found to be due to premature crack formation, and their incidence was found to be temperature sensitive but not strain rate sensitive. The perturbations were considered to be caused by local weak areas in the shell. The results demonstrate the need for close experimental control, and the need for a standard test method was discussed.