Deformability of Contact Layers: Scientific Study

Machine and structural components have volume and surfaces. The last does not have an ideal
shape, and they are rough. When two components have mechanical contact (like one foot of a desk
and the floor), this contact has a common contact surface. It is well known that real contact surface is
much smaller than the nominal cross-section of the smaller component. Furthermore, the volume that
is near the contact surface is not dense. It contains asperities and empty space between them. In this
chapter is analysed the question “What happens with this contact volume and could we measure its
size, depending on the load?” The theory starts with an acceptance that this volume (contact layer) is
filled non-homogeneously with solid material and therefore its mechanical behaviour is non-linear. It is
explained a semi-empiric model for this phenomenon and also a method for interpretation and
presentation of nonlinear force-displacement diagrams. This semi-empiric relationship is
, where P is the load, is the uniaxial deformation of the system with base length L, containing
one contact layer and both a, b are regression coefficients. Results for deformability of the contact
layer between a specimen, made of light silicate concrete and the steel support are shown.