·
CNOF Automated adjustment (KEYOPT(5))· Contact stiffness variation range (KEYOPT(6))
·
Time step control (KEYOPT(7))·
Asymmetric contact selection (KEYOPT(8))·
Effect of initial penetration or gap (KEYOPT(9))·
Contact stiffness update (KEYOPT(10))·
Shell thickness effect (KEYOPT(11)) (not applicable toCONTA176)·
Behavior of contact surface (rough, bonded, etc.)(KEYOPT(12))1、KEYOPT(1)
Selects DOF
2、KEYOPT(2)
Selecting a Contact Algorithm
· Penalty method (KEYOPT(2) = 1)
· Augmented Lagrangian (default) (KEYOPT(2) = 0)
· Lagrange multiplier on contact normal and penalty on tangent(KEYOPT(2) = 3)
· Pure Lagrange multiplier on contact normal and tangent (KEYOPT(2)= 4)
· Internal multipoint constraint (MPC) (KEYOPT(2) = 2)
Compared to the penalty method, the augmented Lagrangian methodusually leads to better conditioning and is less sensitive to themagnitude of the contact stiffness.
相对罚函数法，扩大拉格朗日法不易引起病态条件，对接触刚度数值敏感性更小。
Chattering Control Parameters（跳跃控制参数）
The Lagrange multiplier methods (KEYOPT(2) = 3, 4) do not requirecontact stiffness, FKN and FKT. Instead they require chatteringcontrol parameters, FTOLN and TNOP, by which ANSYS assumes that thecontact status remains unchanged. FTOLN is the maximum allowablepenetration and TNOP is the maximum allowable tensile contactpressure.
The behavior can be described as follows:
· If the contact status from the previous iteration is open and thecurrent calculated penetration is smaller than FTOLN, then contactremains open. Otherwise the contact status switches to closed andanother iteration is processed.
· If the contact status from the previous iteration is closed andthe current calculated contact pressure is positive but smallerthan TNOP, then contact remains closed. If the tensile contactpressure is larger than TNOP, then the contact status changes fromclosed to open and ANSYS continues to the next iteration.
The objective of FTOLN and TNOP is to provide stability to modelswhich exhibit contact chattering due to changing contact status. Ifthe values you use for these tolerances are too small, the solutionwill require more iterations. However, if the values are too large,the accuracy of the solution will be affected since a certainamount of penetration or tensile contact force is allowed.
参数FTOLN和TNOP 主要为结构提供稳定性，该类结构一般会因接触状态的改变而呈现出接触跳跃。
4、KEYOPT(4)
Location of contact detection pointThe nodal detection algorithms require the smoothing of the contactsurface (KEYOPT(4) = 1) or the smoothing of the target surface(KEYOPT(4) = 2), which is quite time consuming. You should use thisoption only to deal with corner, point-surface, or edge-surfacecontact (see
Figure 3.13: 'Contact Detection Point Location at NodalPoint'). KEYOPT(4) = 1 specifies that the contact normal beperpendicular to the contact surface. KEYOPT(4) = 2 specifies thatthe contact normal be perpendicular to the target surface. Use thisoption (KEYOPT(4) = 2) when the target surface is smoother than thecontact surface.
节点检测算法要求接触面光滑(KEYOPT(4) = 1)或目标面光滑(KEYOPT(4) =2)，上述要求均造成计算耗时较大。一般用户仅在处理角点、点-面、边-面接触问题时才用到该选项。KEYOPT(4) =1表明，接触单元方向垂直于接触面表面。KEYOPT(4) =2表明，接触单元方向垂直于目标面表面。当目标面较接触面光滑时，使用KEYOPT(4) = 2。
5、
KEYOPT(5)CNOF/ICONT Automated adjustment:
0 -- No automated adjustment 1 -- Close gap with auto CNOF 2 --Reduce penetration with auto CNOF 3 -- Close gap/reduce penetrationwith auto CNOF 4 -- Auto ICONT Use real constant CNOF to specify acontact surface offset.
CNOF specifies the positive or negative offset value applied tothe contact surface.
Specify a positive value to offset the entire contact surfacetowards the target surface. Use a negative value to offset thecontact surface away from the target surface.ANSYS canautomatically provide the CNOF value to either just close the gapor reduce initial penetration Set KEYOPT(5) =1/2/3.
ICONT defines an initial closure factor (or adjustmentband).
SetKEYOPT(5) =4.Use the real constant ICONT to specify a smallinitial contact closure. This is the depth of an 'adjustment band'around the target surface. Any contact detection points that fallwithin this adjustment band are internally shifted to be on thetarget surface .Only a very small correction is suggested;otherwise, severe discontinuity may occur (see Figure (b)).
The difference between CNOF and ICONT is that the former shifts theentire contact surface with the distance value CNOF, the lattermoves all initially open contact points which are inside ofadjustment band ICONT onto the target surface.
6、KEYOPT(6)
Contact stiffness variation range
The default method of updating normal contact stiffness is suitablefor most applications. However, the variational range of thecontact stiffness may not be wide enough to handle certain contactsituations. In the case of a very small penetration tolerance(FTOLN), a larger normal contact stiffness is often needed.Furthermore, to stabilize the initial contact condition and toprevent rigid body motion, a smaller normal contact stiffness isrequired.
默认的法向接触刚度更新方式对于大多数应用来说是合适的。然而，接触刚度的变化范围并不是足够大到处理某些特定问题。在穿透容差非常小的情况下，需要较大的法向接触刚度；而且，为了稳定初始接触状态，并阻止刚体运动，需要较小的法向刚度。
The allowed contact stiffness variation is intended to enhancestiffness updating when KEYOPT(10) > 0 by calculating an optimalallowable range in stiffness for use in the updating shceme. Toincrease the stiffness variational range, set KEYOPT(6) = 1 to makea nominal refinement to the allowable stiffness range, or KEYOPT(6)= 2 to make an aggressive refinement to the allowable stiffnessrange.
当KEYOPT(10) >0时，通过刚度更新程序，软件可计算最优容许刚度范围，用来提高刚度更新速度。为了增加刚度变化范围，取KEYOPT(6) =1可对容许刚度范围进行名义上的细化，取KEYOPT(6) = 2 可对容许刚度范围进行更积极改进。
7、KEYOPT(7)
Time step control is an automatic time stepping feature thatpredicts when the status of a contact element will change and cutsthe current time step back.
Use KEYOPT(7) to take one of four actions to control time stepping,where KEYOPT(7) = 0 provides no control (the default), andKEYOPT(7) = 3 provides the most control.
KEYOPT(7) = 0: No control. The time step size is unaffected by theprediction. This setting is appropriate for most analyses whenautomatic time stepping is activated and a small time step size isallowed.
KEYOPT(7) = 1: Time step size is bisected if too much penetrationoccurs during an iteration, or if the contact status changesdramatically.
KEYOPT(7) = 2: Predict a reasonable increment for the nextsubstep.
KEYOPT(7) = 3: Predict a minimal time increment for the nextsubstep.
8、KEYOPT(8)
Asymmetric contact is defined as having all contact elements on onesurface and all target elements on the other surface. This issometimes called 'one-pass contact.' This is usually the mostefficient way to model surface-to-surface contact. However, undersome circumstances asymmetric contact does not performsatisfactorily. In such cases, you can designate each surface to beboth a target and a contact surface. You can then generate two setsof contact pairs between the contacting surfaces (or just onecontact pair; for example, a
