Giuseppe Guzzetta

Abstract:

Resorting to the approximations currently accepted when dealing with deformations of a continuum in which displacements are assumed to be infinitesimal, it goes unnoticed that the observable (measurable) volume change implied by deformation is equal to the algebraic sum of two contributions to which a different physical meaning should be attributed. Without making use of the above approximations, one unveils that in a system undergoing deformation at least one of the above contributions is different from zero. A convenient description of the deformation allows both the definition of the conditions at which one of the contributions vanishes, and the mathematical determination of the common absolute value of the two contributions during isochoric deformations. A corresponding description of the internal reactions to forces and couples acting on the deforming continuum is strongly suggested by such a description of deformation. Needless to say, the recognition of the fact that one of the two contributions to volume change is related to entropy increase and the other one with entropy decrease is a not ignorable prerequisite for a reliable approach to the physics of deformation.