Factors affecting the non‐destructive and destructive methods of measuring egg shell strength by the quasi‐static compression test1

Contribution No. 482 from Engineering Research Service and Contribution No. 567 from Animal Research Institute.

1. Precise measurements of shell deformation and fracture force were made to examine the destructive and non‐destructive quasi‐static compression tests of egg shell strength.

2. Prediction of shell strength from shell deformation (d) was not greatly improved by combining egg length, diameter and shell thickness with shell deformation. At the equator 54% of the variation in fracture force (F) was accounted for by an equation F = 8467 ‐ 115630i+584166d² compared with 57% when 13 measured and generated parameters were included (singly and in combination) in the analysis.

3. Cracks changed the deformation by an average of 8% providing the crack was not near the points where force was applied. Cracked eggs could be tested to reduce the bias introduced by eliminating such eggs from experiments. Empirical factors must, however, be established to correct such deformation readings.

4. Use of a hole or rubber on the lower compression surface to stabilise the egg increased the force required to fracture the shell at the upper flat surface Such surfaces are undesirable because the fracture site is biased towards the upper contact point when force is distributed at the lower surface. Shell deformation and its correlation with strength was also reduced.

5. The fracture force predicted by a non‐destructive deformation measurement was greatly affected by the force applied. The optimum test force was 1 kg at the equator.

Notes

Contribution No. 482 from Engineering Research Service and Contribution No. 567 from Animal Research Institute.