接触笔记
1、中国第一大沙漠Defining contact pairs in ABAQUS/Standard
After the lection of contact pair surfaces, three key factors must be determined whencreating a contact formulation:
态度改变the contact discretization;
检查监督the tracking approach; and
芳华电影剧情介绍the assignment of “master” and “slave” roles to the respective surfaces.
1.1the contact discretization
ABAQUS/Standard offers two contact discretization options: a traditional “node-to-surface” discretization and a true “surface-to-surface” discretization.
Node-to-surface contact discretization
Traditional node-to-surface discretization has the following characteristics:
The slave nodes are constrained not to penetrate into the master surface; however, the nodes of the master surface can, in principle, penetrate into the slave surface
The contact direction is bad on the normal of the master surface.
The only information needed for the slave surface is the location and surface area associated with each node; The direction of the slave surface normal and slave surface curvature are not relevant.Thus, the slave surface can be defined as a group of nodes—a node-bad surface.
Node-to-surface discretization is available even if a node-bad surface is not ud in the contact pair definition
Fig.1 Node-to-surface contact discretization
Surface-to-surface contact discretization
To optimize stress accuracy, surface-to-surface discretization considers the shape of both the slave and master surfaces in the region of contact constraints.
Surface-to-surface discretization has the following key characteristics:
Contact conditions are enforced in an average n over the slave surface, rather than at discrete points (such as at slave nodes, as in the ca of node-to-surface discretization). Therefore, some penetration may be obrved at individual nodes; however, large, undetected penetrations of master nodes into the slave surface do not occur with this discretization.
Surface-to-surface discretization is not applicable if a node-bad surface is ud in the contact pair definition.
在某一个迭代步中,面对面的接触计算成本一般较点对面的接触的计算成本高,但多数情况下这个成本不会高很多,只有在下列情况下才会让计算成本急剧增大:
模型的绝大部分区域被包含于接触中;
当主动面比从属面网格划分还要精细时;
Multiple layers of shells are involved in contact, such that the master surface of one contact pair acts as the slave surface of another contact pair.
尽管如此,但点对面的接触需要花费更多的迭代步才能达到数值稳定,从某种意义上来说,在一个分析步中,无法判定到底是用点对面接触还是面对面接触计算成本低.
1.2Contact tracking approaches
In ABAQUS/Standard there are two tracking approaches to account for the relative motion of the two surfaces forming a contact pair in mechanical contact simulations:
The finite-sliding tracking approach
The small-sliding tracking approach西柏坡村
1.3Fundamental choices affecting the contact formulation内部晋升
Your choice of contact discretization and tracking approach have considerable impact on an analysis. In addition to the qualities already discusd, certain combinations of discretizations and tracking approaches have their own characteristics and limitations associated with them. The characteristics are summarized in Table 1. You should also consider the solution costs associated with the various contact formulations
Table 1Comparison of contact formulation characteristics
1.4 选择主动面和从属面的几个原则
Analytical rigid surfaces and rigid-element-bad surfaces must always be the master surface.
A node-bad surface can act only as a slave surface and always us node-to-surface contact.
Slave surfaces must always be attached to deformable bodies or deformable bodies defined as rigid.世界著名雕塑
Both surfaces in a contact pair cannot be rigid surfaces with the exception of deformable surfaces defined as rigid
一般来说,当定义两个基于单元的面作为解除对作用面时,当存在一个较小的面和一个较大的面时，一般将较小的面定义为从属面。当两个面大小接近时，选取较“硬”的面或单元划分笔记粗糙的面作为主动面。值得注意的是，“硬”的面不一定是材料弹性模量大的材料，比如当一个薄金属片和一个橡胶材料接触时，此时就应该将薄金属片所属的面定义为从属面。当两个面区域接近，“硬度”也接近时，此时往往需要反复尝试才能得到较好的结果。
与点对面接触相比，面对面接触中主动面和从属面的选取，对计算结果的影响并不是很大。但是，当错误的将网格粗糙的面定义为从属面时，此时也许会引起计算成本的急剧增加。
1.5定义接触对
为了定义一个接触对，必须指定一对接触面或者一个自接触的面，一个contact formulation。每一个接触对可以定义不同的作用面性质。
Defining contact between two parate surfaces
When a contact pair contains two surfaces, the master and slave surfaces are not allowed to include any of the same nodes and you must choo which surface will be the slave and which will be the master.
ABAQUS/Standard定义接触默认采用的是有限滑移、点对面接触苏州旅行。如果定义的是小滑移，默认的也吃采用点对面接触。
用对称的主从接触对提高接触模拟精度
对于点对面接触，主动面上的节点很容易penetrate到从属面上去，此时，提高从属面上单元的网格划分精度，有助于减少这样的刺入，提高运行速度。才外，让两个面都是基于单元定义时，可以用symmetric master-slave method。To u this method, define two contact pairs using the same two surfaces, but switch the roles of master and slave surface for the two contact pairs. This method caus ABAQUS/Standard to treat each surface as a master surface and, thus, involves additional computational expen becaus
e contact arches must be conducted twice for the same contact pair. The incread accuracy provided by this method must be compared to the additional computational cost.
