CONTACTGENERATE

Automated Surface Contact Generation

Description: Automated Surface Contact Generation (ASCG) and Automated Edge Contact Generation (AECG). Automatically generates surface contact/weld elements between solid or shell elements near or in contact with other solid or shell elements.

Format:

CONTACTGENERATE, ptype, esid, sfact, fstif, mu, maxad, w0, tmax, eid

Example:

CONTACTGENERATE, 1, , , , 0.1

Option	Definition	Type	Default
ptype	Penetration type. See Remark 1. 1 = Symmetric general contact 2 = Symmetric welded contact 3 = Symmetric bi-directional sliding contact 4 = Symmetric rough contact 5 = Offset welded contact	1 ≤ Integer ≤ 5	2
esid	Element set identification number. Set identification of previously appearing SET command. Only elements whose identification numbers appear on this SET command will be used.	Integer > 0	All
sfact	Stiffness scaling factor used to scale the penalty values determined automatically. See Remark 2.	Real ≥ 0.0	1.0
fstif	Frictional stiffness for stick. See Remark 3.	Real ≥ 0.0	Model dependent
mu	Coefficient of static friction.	Real ≥ 0.0	0.0
maxad	Maximum normal and radial activation distance. See Remark 4.	Real ≥ 0.0	See Remark 4
w0	Penetration surface offset. See Remark 5.	Real	0.0
tmax	Maximum allowable penetration used in the adjustment of penalty values normal to the contact plane. A positive value activates the penalty value adjustment. See Remark 6.	Real ≥ 0.0	0.0
eid	Element identification number.	Integer > 0 or blank	See Remark 8

Remarks:

1. Welded contact behavior is accomplished by selecting the welded contact setting (2). With this setting the element will behave the same in tension as in compression and will not slide. Note that for linear solutions with the LINEARCONTACT model parameter set to OFF, general contact will default to welded behavior (see Section 5, Parameters, for more information on LINEARCONTACT). Bi-directional sliding contact behavior is accomplished by selecting the bi-directional contact setting (3). With this setting the element will act similar to a welded contact element in tension and compression, but will slide in-plane. Bi-directional sliding contact is intended for use on planar surfaces and is available in all solutions. Rough contact behavior is accomplished by selecting the rough contact setting (4). With this setting the element will act similar to a general contact element in tension and compression, but will not permit sliding in-plane. The offset weld setting (5) is intended for welded connections with significant separation between contact surfaces. Welded contact with a separation less than the value defined by the SLINEOFFSETTOL model parameter is automatically converted to an offset weld (see Section 5, Parameters, for more information on SLINEOFFSETTOL).
2. sfact may be used to scale the penalty values that are determined automatically based on adjacent diagonal stiffness matrix coefficients. Additionally, penalty values calculated may be further scaled by the SLINEKSFACT model parameter (see Section 5, Parameters, for more information on SLINEKSFACT). The penalty value is then equal to , where k is a value selected for each secondary node based on the diagonal stiffness matrix coefficient and sfact is specified in the sfact field above. Note that the SLINEKSFACT value applies to all contact regions in the model. The use of a scale factor (sfact or SLINEKSFACT) less than one is recommended when convergence problems arise, and a value greater than one when excessive penetration occurs. Penalty values are normally recalculated every time there is a change in stiffness. However, if SLINEKSFACT is negative, penalty values are not recalculated. This setting is generally not recommended. Note that for heat transfer solutions with the SLINEKSFACT2TC model parameter set to ON, sfact will be interpreted as contact capacitance (see Section 5, Parameters, for more information on SLINEKSFACT2TC).
3. The value of frictional stiffness should be chosen carefully. A method of choosing a value is to divide the expected frictional strength (mu * expected normal force) by reasonable value of the relative displacement before slip occurs. A large stiffness value may cause poor convergence, while too small a value may result in reduced accuracy.
4. maxad is the contact surface normal and radial tolerance for generating a contact element. A recommended value is a distance approximately 10% larger than the largest gap to be recognized as contact (or welded). If maxad is not specified, it will be internally calculated by multiplying the model reference dimension by 1.0E-04. Note that when maxad is specified, the SLINEOFFSETTOL model parameter will be set to this value. (See Section 5, Parameters, for more information on SLINEOFFSETTOL.)
5. The contact plane is defaulted to the xy-plane of the primary nodes. A positive value of w0 offsets the contact plane in the element z-direction and results in a contact condition occurring when a secondary node penetrates the offset plane.
6. There are two methods for adaptive stiffness updates normal to the contact plane: proximity stiffness based and displacement based. If tmax ≠ 0.0, the displacement based update method is selected. When tmax = 0.0 (default), the proximity stiffness based update method is selected. The recommended allowable penetration tmax is between 1% and 10% of the element thickness for plates or the equivalent thickness for other elements that are connected to the contact element.
7. The CONTACTGEN and CONTACTTOL model parameters provide the same functionality as this command. See Section 5, Parameters, for more information on CONTACTGEN and CONTACTTOL.
8. The default element identification number is one plus the maximum element identification number in the model.