·
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 to
CONTA176)
·
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 method
usually leads to better conditioning and is less sensitive to the
magnitude 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 require
contact stiffness, FKN and FKT. Instead they require chattering
control parameters, FTOLN and TNOP, by which ANSYS assumes that the
contact status remains unchanged. FTOLN is the maximum allowable
penetration and TNOP is the maximum allowable tensile contact
pressure.
The behavior can be described as follows:
· If the contact status from the previous iteration is open and the
current calculated penetration is smaller than FTOLN, then contact
remains open. Otherwise the contact status switches to closed and
another iteration is processed.
· If the contact status from the previous iteration is closed and
the current calculated contact pressure is positive but smaller
than TNOP, then contact remains closed. If the tensile contact
pressure is larger than TNOP, then the contact status changes from
closed to open and ANSYS continues to the next iteration.
The objective of FTOLN and TNOP is to provide stability to models
which exhibit contact chattering due to changing contact status. If
the values you use for these tolerances are too small, the solution
will require more iterations. However, if the values are too large,
the accuracy of the solution will be affected since a certain
amount 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 point
The nodal detection algorithms require the smoothing of the contact
surface (KEYOPT(4) = 1) or the smoothing of the target surface
(KEYOPT(4) = 2), which is quite time consuming. You should use this
option only to deal with corner, point-surface, or edge-surface
contact (see
Figure 3.13: 'Contact Detection Point Location at Nodal
Point'). KEYOPT(4) = 1 specifies that the contact normal be
perpendicular to the contact surface. KEYOPT(4) = 2 specifies that
the contact normal be perpendicular to the target surface. Use this
option (KEYOPT(4) = 2) when the target surface is smoother than the
contact 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 penetration
with auto CNOF 4 -- Auto ICONT Use real constant CNOF to specify a
contact surface offset.
CNOF specifies the positive or negative offset value applied to
the contact surface.
Specify a positive value to offset the entire contact surface
towards the target surface. Use a negative value to offset the
contact surface away from the target surface.ANSYS can
automatically provide the CNOF value to either just close the gap
or reduce initial penetration Set KEYOPT(5) =1/2/3.
ICONT defines an initial closure factor (or adjustment
band).
SetKEYOPT(5) =4.Use the real constant ICONT to specify a small
initial contact closure. This is the depth of an 'adjustment band'
around the target surface. Any contact detection points that fall
within this adjustment band are internally shifted to be on the
target 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 the
entire contact surface with the distance value CNOF, the latter
moves all initially open contact points which are inside of
adjustment band ICONT onto the target surface.
6、KEYOPT(6)
Contact stiffness variation range
The default method of updating normal contact stiffness is suitable
for most applications. However, the variational range of the
contact stiffness may not be wide enough to handle certain contact
situations. 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 to
prevent rigid body motion, a smaller normal contact stiffness is
required.
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 enhance
stiffness updating when KEYOPT(10) > 0 by calculating an optimal
allowable range in stiffness for use in the updating shceme. To
increase the stiffness variational range, set KEYOPT(6) = 1 to make
a nominal refinement to the allowable stiffness range, or KEYOPT(6)
= 2 to make an aggressive refinement to the allowable stiffness
range.
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 that
predicts when the status of a contact element will change and cuts
the 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), and
KEYOPT(7) = 3 provides the most control.
KEYOPT(7) = 0: No control. The time step size is unaffected by the
prediction. This setting is appropriate for most analyses when
automatic time stepping is activated and a small time step size is
allowed.
KEYOPT(7) = 1: Time step size is bisected if too much penetration
occurs during an iteration, or if the contact status changes
dramatically.
KEYOPT(7) = 2: Predict a reasonable increment for the next
substep.
KEYOPT(7) = 3: Predict a minimal time increment for the next
substep.
8、KEYOPT(8)
Asymmetric contact is defined as having all contact elements on one
surface and all target elements on the other surface. This is
sometimes called 'one-pass contact.' This is usually the most
efficient way to model surface-to-surface contact. However, under
some circumstances asymmetric contact does not perform
satisfactorily. In such cases, you can designate each surface to be
both a target and a contact surface. You can then generate two sets
of contact pairs between the contacting surfaces (or just one
contact pair; for example, a
