3、接触检测点位置

   接触检测点为集成点，位于接触单元节点上或高斯点上。接触单元通过集成点被限制以避免向目标单元渗透。然而，目标单元原则上可向接触单元渗透。

CONTA174 is surface-to-surface contact element. The contact detection points are the integration point and are located either at nodal points or Gauss points. The contact elements is constrained against penetration into target surface at its integration points. However, the target surface can, in principle, penetrate through into the contact surface. See Figure 14.58: "Contact Detection Point Location at Gauss Point". CONTA174 uses Gauss integration points as a default (Cescotto and Charlier(213), Cescotto and Zhu(214)), which generally provides more accurate results than those using the nodes themselves as the integration points. A disadvantage with the use of nodal contact points is that: when for a uniform pressure, the kinematically equivalent forces at the nodes are unrepresentative and indicate release at corners.

4、接触检测点渗透距离如何计算？

  接触检测点位于接触单元上，原则上，接触单元向目标单元渗透的距离不能太大，该渗透距离不能大于程序的渗透容许值。

The penetration distance is measured along the normal direction of contact surface located at integration points to the target surface (Cescotto and Charlier(214)). See Figure 14.59: "Penetration Distance". It is uniquely defined even the geometry of the target surface is not smooth. Such discontinuities may be due to physical corners on the target surface, or may be introduced by a numerical discretization process (e.g. finite elements). Based on the present way of calculating penetration distance there is no restriction on the shape of the rigid target surface. Smoothing is not always necessary typically for the concave corner. For the convex corner, it is still recommended to smooth out the region of abrupt curvature changes (see Figure 14.60: "Smoothing Convex Corner").

5、Pinball Algorithm

 The position and the motion of a contact element relative to its associated target surface determine the contact element status. The program monitors each contact element and assigns a status:

 6、R1 R2实常数什么时候使用？  

 R1 R2仅用于定义目标单元几何体积的。R1 and R2 define the target element geometry.

 而且只有在特殊情况下，才用到R1 R2。例如：当目标单元TARGE169的形状为圆时，才用到半径 R1。R2在超单元设置时才用到。

• For CONTA171 and CONTA172:

  • R1 is the radius if the target shape (TARGE169) is a circle.

  • R2 is the element thickness if the underlying element is a superelement set as plane stress with thickness (KEYOPT(3) = 3). The default value is 1.

•  7、slip sliding 区别

    The amount of slip in sticking contact depends on the tangential stiffness. 处于粘结状态的接触也会产生剪应变及剪切位移，该剪切位移称为slip，在接触单元TARGE169实常数中还可定义elastic slip大小。而sliding：

     ANSYS provides one extension of classical Coulomb friction: real constant TAUMAX is maximum contact friction with units of stress. This maximum contact friction stress can be introduced so that, regardless of the magnitude of normal contact pressure, sliding will occur if the friction stress reaches this value.