ANALYSIS OF COMPRESSION, TENSION AND TORSION FOR TESTING FOOD GEL FRACTURE PROPERTIES*

Abstract

ABSTRACT Three fracture test methods: uniaxial compression, uniaxial tension and torsion were examined by interpreting results using theories upon which the methods were based. In each of these tests, the fracture of gels can occur as a result of shear, compression or tension. The fracture properties determined from uniaxial compression and tension were compared with torsion testing, a suitable reference technique. Shear stress and strain in uniaxial compression were comparable with shear stress and strain in torsion. However, the tensile stress in compression is not in agreement with that in torsion. Tensile stress or shear stress values in uniaxial tension were generally comparable with tensile or shear stress values in torsion, while the strain levels in uniaxial tension were typically much lower than those in uniaxial compression or torsion. This result could be related to the fracture strain being a function of elongation necessary to reduce the specimen cross section to an area producing the critical fracture stress. The comparison among different methods revealed shear stress and strain can be the fracture criteria for uniaxial compression, and tensile stress can be the fracture criterion for uniaxial tension, whereas the fracture strain criterion in uniaxial tension cannot be specified. Possible mechanisms for differences among methods are discussed in the manuscript.