This presentation was made at the 2019 NAFEMS World Congress in Quebec Canada
Contact is a highly nonlinear boundary condition in Finite Element Analysis (FEA), which is used in many applications. Each assembly model has joints where contact is present. An accurate representation of the actual contact has a great influence on displacements and stresses. In fact, even very small changes in the contact geometry can change the FE results drastically.
Although contact is omnipresent in FEA applications, the standing of contact analysis is still rather poor due to high computational effort, sometimes serious convergence and accuracy problems. Such problems can also limit the possible model sizes due to increasing computing times. Users often replace true contact by other couplings and hope that the results will be acceptable. When model sizes increase due to needs for predicting durability, the situation becomes even worse.
Although contact is a nonlinear effect, the other structural behaviour is linear in many cases, i.e. no material nonlinearity and no geometrical nonlinearity is involved. But FE solvers mainly use nonlinear solution methods, where the stiffness matrix is updated iteratively to represent the contact stiffness in a suitable manner. Beside penalty methods, Lagrange methods are available, which amend the structural degrees of freedom by additional contact degrees of freedom leading to very accurate results, but the computational effort becomes hardly affordable.
In recent years, optimization methods became more popular. One important prerequisite for using optimization is that the basic analysis is running short enough to justify an optimization overnight or within one or two days. This imposes another demand on contact analysis to provide short run times. In many cases, larger contact analyses do not run fast enough to apply optimization.
When simulations with contact should earn more confidence, then alternative approaches to contact analysis have to be investigated. It is the purpose of this paper to explain an alternative FE contact analysis method and to present a number of examples to show the broad application field and its benefits.
|Date||18th June 2019|