Effect of sample dimensions, lubrication and deformation rate on uniaxial compression of gelatin gels

Abstract

The response of 10% gelatin gels to uniaxial compression is determined in part by frictional effects at the gel-platen interface. By using teflon-coated plates, lubricated with paraffin or silicone oil, these frictional effects are effectively eliminated. The stress-strain response can then be described by the two-constant Mooney-Rivlin relation, the sum of the two parameters (C 1 + C2) being about 25% lower in lubricated compression than the value obtained in simple shear and torsion. Cross-head speed (for total testing times of 0.2-3 rain) had no effect on material response, but long-term stress relaxation does occur over periods of about 30 rain and longer. Sample radius did not affect the response in lubricated compression but had a major effect under unlubricated conditions. No systematic change in response was seen with sample diameter to height (aspect) ratios between 9.6 and 3.1 in lubricated compression, but data scatter for a given sample diameter was worst at the lowest heights (highest aspect ratio). Agreement of all true stress versus strain data was within about _+ 7% regardless of sample height or deformation rate.

Applicability of the modified Mooney-Rivlin equation on rheological analysis of fish-meat gel

“…Bagley et al . exhibited the compression properties of gelatin and starch gels using the Mooney–Rivlin equation 8,9 . In the previous paper, 10,11 the theoretical values obtained by substituting volume change of the gel with the strain agreed more exactly with the experimental values and gave a more meaningful explanation than those using the original Mooney–Rivlin equation.…”

Squeeze flow theory and applications to rheometry: A review

“…graphite) [90,91,139,166,176,[184][185][186][187][188][189][190][191]. When a lubricating fluid is used, the balance between drag and squeezing out of this fluid must be carefully considered [87,89,90,120,192] as discussed in Section 3.3.2, since thinning of the lubricating layer means an increase in shear stress if the radial velocity at of the interface is to remain constant.…”

The Viscoelastic Properties of Wheat Flour Doughs

“…This phenomenon, determined to be due to the existence of frictional effecb between the compressing surfaces and the material undergoing compression, could be mini-mized by utilizing Teflon®-coated platens and lubricating the platen/sample interface with paraffin oil (Bagley et al, 1985a(Bagley et al, , 1985b. Bagley and Christianson (1986) used this technique (lubricated uniaxial compression) in a series of experiments designed to measure the apparent biaxial elongational viscosity of commercial, chemically leavened wheat flour doughs.…”