HENS EGG - SHELL FORCES AT IMPACT AND QUASI-STATIC COMPRESSION

An equation is derived which relates the maximum force, Pm, exerted on an egg shell to the relative velocity, v0, of the egg and a body on which it impacts and to their masses, M1 and M2, and stiffnesses, S1 and S2; it is Pm = [(1/2)v02]1/2[M1M2/(M1 + M2)]1/2[S1S2/(S1 + S2)]1/2. Another equation is derived which relates the maximum force exerted by the egg to the reciprocals, Ra and Re, of its average and 1st principal curvatures at the point of impact, to the shell thickness, T.epsilon., that is effective in respect of tensile strength, and to the ultimate strength of shell material, Stu; it is Pm = kStuT.epsilon.Rax(Ra/Re)y in which k, x and y are constants. These equations are concordant with published data on egg shell fracture under both quasi-static and dynamic conditions when x and y have the values -1 and 0, respectively. The equations provide a theoretical structure that can be used to identify the factors likely to affect egg shell fracture under specific conditions.