Impact of the hen egg size on its fracture point measuring the eggshell deformation

Abstract

A digital holographic interferometer is used to measure surface deformation and fracture points in hen eggs under mechanical compression. All samples were subjected to a constant compression load until they fractured. Three different tests are performed to analyze the eggs’ mechanical response. In the first test, the egg is vertically oriented, and so the applied load; meanwhile, for the second test, the egg is horizontally oriented with the load applied vertically. The third test keeps the egg horizontal, but on this occasion, the applied load is also horizontal. As the mechanical load is applied, a camera records full-field holograms that retrieve the entire surface deformation of each egg. The influence of the egg’s orientation and the load direction modifies the eggshell surface deformation and fracture pattern. In general, fracture propagation is aligned with the load direction. From the results, samples compressed along the length of the egg show fractures, but remained in one piece. A different behavior is observed when the load is applied at the egg’s width, which separates the eggshell into two semispheres, allowing the egg’s content to drain out. A multivariate analysis was used to integrate the egg dimensions with the resulting optical data, showing a strong relationship between egg size and the fracture point. Larger eggs tend to exhibit more extensive fractures, while smaller and medium-sized eggs showed minor damage. Even though some of this information is empirically known, this is the first time it has been proven by a full imaging inspection showing eggshell deformation and cracks across eggs, independent of egg size. The latter is an advantage as there is no need to limit the study to particular dimensions to measure the exact moment of the fracture, its position, and distribution.