CHARACTERIZATION OF NONLINEAR ELASTIC PROPERTIES OF BEEF PRODUCTS UNDER LARGE-DEFORMATION

Knowledge of mechanical properties of beef is important for studying i ts tenderness and improving tenderness measurement techniques. This re search was initiated to develop a three-dimensional constitutive equat ion to describe the nonlinear stress-strain relationship of beef produ cts in large deformations, to determine the constitutive parameters, a nd to validate the model for multidimensional stress/strain states. Ba sed on experimental observations and the theory of finite elasticity a three-dimensional constitutive equation was proposed, which assumes t hat the materials are isotropic and incompressible. Uniaxial compressi on tests were performed on twenty samples each of bologna, salami, and smoked sausage to determine the two parameters in the constitutive eq uation. Confined two-dimensional compression tests were also conducted to validate the constitutive equation. Experimental results showed th at beef products exhibited a pronounced nonlinearity under uniaxial co mpression; the slope of the force-deformation curves increased monoton ically with the increasing deformation. The constitutive equation fitt ed the stress-strain curves well for the three products. The constitut ive equation predicted well the stress-strain responses of the beef pr oducts under confined two-dimensional loading; the differences between predicted and measured values were mostly not significant at the 0.05 level. This constitutive equation can be used to predict stress-strai n responses of beef products under different loading conditions.