Implementation of assembled surface normals and of a penalty contact formulation in the pinball model of EUROPLEXUS

The most popular contact algorithms available in finite element computer codes are probably the so-called slide line (in 2D) and slide surface (in 3D) algorithms proposed by Hallquist and Benson. They are based on the notion of penetration of slave nodes into master segments (in 2D) or into master surfaces (in 3D). These algorithms suffer from a number of geometrically pathological cases in which physical penetration is not detected. The pinball method proposed by Belytschko and co-workers from the late 80's for application in impact problems with penetration is much more robust as concerns penetration detection. The pinball contact-impact method has been implemented in EUROPLEXUS, initially based upon a strong, Lagrange-multiplier based solution strategy of the contact constraints. Recently, the so-called Assembled Surface Normal (ASN) algorithm of Belytschko and an alternative penalty-based solution of the contact constraints have also been introduced as an option in the code. They are described in the present report.