Contact Laws

Introduction

NairnMPM and OSParticulas implement contact physics on crack surfaces and between materials in multimaterial mode by using contact laws. Each contact law can define frictional contact or describe an imperfect interface. Contact laws are assigned to crack or material surfaces by using the ContactCracks or ContactMM commands, by using the Contact material property, or by choosing a custom contact law when defining a new crack. This section explains the possible contact laws.

You create contact law using a Material command block. Within that block all contact law properties are set using property commands. Refer to each contact law type to learn about its possible properties.

Frictional Contact Laws

Frictional contact laws give the sliding shear traction, S_slide, as a function of the normal traction, N, the contact area, A_c, the relative sliding velocity, Δv,and possible other parameters, or:

      <math>S_{slide} = f(N,A_c,\Delta v,\dots)</math

Given any frictional law, the shear traction applied at any node is given by:

      <math>S_{resultant} = \minmin(S_{slide},S_{stick})</math

where S_stick is the shear traction needed for tangential motion of the two surface to move together (i.e., to stick). In other words, if the shear traction calculated for frictional sliding is greater than the traction required for surfaces to stick together, then the surface will stick. Once that sticking shear traction exceeds S_slide, the surfaces will slide with the given sliding traction.