The hen's egg: Shell cracking at impact on a heavy, stiff body and factors that affect it

Anderson, G. B.; Carter, T. C.

doi:10.1080/00071667608416318

Cited by 18 publications

(10 citation statements)

References 14 publications

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“…If it is elliptical the stress may be maximal at two or more symmetrically located points, the locations of which must be dependent on the directions of the principal curvatures. That such maxima do occur is indicated by the fact that when an egg is compressed at the equator between parallel plates or impacts on a flat plate the crack almost always runs either towards a pole or round the equator, not in an intermediate direction (Hunt and Voisey, 1966;Anderson and Carter, 1976). However, there is no overwhelming tendency for the cracks to run towards a pole rather than round the equator, or vice-versa; this suggests that when the principal curvatures differ the critical annulus has four stress maxima, two in the direction of each principal curvature, and that they are approximately equal in magnitude.…”

Section: The Force Exerted On An Egg At Impactmentioning

confidence: 96%

“…If the values of x andj are -1 and 0, respectively, equation 16 predicts that v^R^M^Te will be proportional to T e and (T e IT e yiR a M 1 will be proportional to the drop height, h, corresponding with v 0 . These predictions were tested by data of Anderson and Carter (1976), who allowed five eggs from each of 30 hens to swing against a heavy, flat, steel plate. Each egg was tested repeatedly, with increasing velocity at impact, but it was rotated so that repeated blows at the same or closely neighbouring points were avoided.…”

Section: Casementioning

confidence: 99%

“…Anderson and Carter (1976). Abscissae, (TJT e )* [\ + Ae) n jM v R a (g-1 mm" 1 x 10 4 ); A e (d) is the age of the egg; n was estimated from the data to be 0-0514: E was estimated from the data for each of the 30 hens.…”

Section: Casementioning

confidence: 99%

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The hen's EGG: Shell forces at impact and quasi‐static compression

Carter

1976

British Poultry Science

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1. An equation is derived which relates the maximum force, P m , exerted on an egg shell to the relative velocity, v 0 , of the egg and a body on which it impacts and to their masses, M 1 and M 2 , and stiffnesses, S 1 and S 2 ; it is 2. Another equation is derived which relates the maximum force exerted by the egg to the reciprocals, R a and R e , of its average and first principal curvatures at the point of impact, to the shell thickness, T ε , that is effective in respect of tensile strength, and to the ultimate strength of shell material, St u ; it is P m = kStuT ε R χ α (Ra/Re)y in which k, χ and y are constants.3. These equations are shown to be 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. 4. The equations provide a theoretical structure that can be used to identify the factors likely to affect egg shell fracture under specified conditions.

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Section: The Force Exerted On An Egg At Impactmentioning

confidence: 96%

Section: Casementioning

confidence: 99%

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The hen's EGG: Shell forces at impact and quasi‐static compression

Carter

1976

British Poultry Science

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“…There have also been reports that the degree of glossiness of a shell has a small effect on its quasi-static shearing strength (Carter, 1970a) and that the presence of ridges on the shell has a small effect on its resistance to impact (Anderson and Carter, 1976). They may be mediated through changes in T and R a respectively.…”

Section: Introductionmentioning

confidence: 96%

“…Data from tests of the shearing and tensile strengths of normal egg shells (Carter, 1970a(Carter, , 1971) and of their resistance to impact (Anderson and Carter, 1976) have shown that s varies from hen to hen, the range of variation of hen-mean estimates being 83 to 147 fim. However, these estimates were obtained by backward linear extrapolation from observations made on shells in the normal thickness range, about EGG SHELL FRACTURE 251 280 to 420 /xm, and for this reason they should be treated with caution unless supported by more direct evidence.…”

Section: Introductionmentioning

confidence: 99%

The hen's egg: Shell fracture under quasi‐static and static loading

Carter

1978

British Poultry Science

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1. An equation fundamental to a recent theory of egg shell strength is P m R a = kSt u (T-ε) in which P m is the maximum force that an egg shell can exert on a body pressing against it, R a is the reciprocal of the average curvature of the shell at its point of contact with the other body, k is a constant of proportionality, St u is the ultimate tensile strength of egg-shell material in the plane of the shell, T is the overall thickness of the shell at the point of contact and ε is the thickness of its weak inner layer.2. Experiments that tested the equation are reported. 3. Shells developed rigidity when they were between 88 and 128 μm thick; this was taken to be the physical basis of ε.4. Measurement of equatorial shell curvatures and force at failure of 240 eggs with normal shells (10 from each of eight hens of each of three strains), loaded at the equator at a low and constant rate, showed that the relationship of P m R a to T was linear, that e varied somewhat from hen to hen but the slope of the line did not, and that P m R a was reduced slightly if the shell was ridged or glossy; regression accounted for 74% of the variance of P m R a .5. The absence of curvilinearity and of variation from hen to hen in the slope imply that the material constituting the palisade layer of the shell was homogeneous in respect of strength, both within and between hens, under the conditions of the experiment : kSt u was constant.6. Seventy-one additional eggs of the same hens were similarly loaded until the load reached a value close to the known hen-mean fracture load; of the 31 that survived loading, 25 showed delayed fracture, so under these experimental conditions kSt u was not constant but a function of time.7. Delays observed ranged from 1 to 62 803 s and showed a loose negative correlation with the quotient W app /W exp , where W app is the load applied to the egg and W exp is the load at fracture which would have been expected if loading had continued at the same low and constant rate. 249

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