4.154 SURF154 3-D Structural Surface Effect

Figure 4.154-1 SURF154 3-D Structural Surface Effect Element

4.154.1 Input Data

The mass and volume calculations use the element thicknesses (real constants TKI, TKJ, TKK, TKL). Thicknesses TKJ, TKK, and TKL default to TKI, which defaults to 1.0. The mass calculation uses the density (material property DENS, mass per unit volume) and the real constant ADMSUA, the added mass per unit area. The stiffness matrix calculation uses the in-plane force per unit length (input as real constant SURT) and the elastic foundation stiffness (input as real constant EFS). The foundation stiffness can be damped, either by using the material property DAMP as a multiplier on the stiffness or by directly using the material property VISC.

See Section 2.7 for a description of element loads. Pressures may be input as surface loads on the element faces as shown by the circled numbers on Figure 4.154-1. The pressure load vector calculation uses the pressure value. For the first four faces, positive values of pressure act in the positive element coordinate directions (except for the normal pressure which acts in the negative z direction). For faces 1 and 4, positive or negative values may be removed as requested with KEYOPT(6) to simulate the discontinuity at the free surface of a contained fluid. For face 4, the magnitude of the pressure at each integration point is P_I + XP_J + YP_K + ZP_L, where P_I through P_L are input as VAL1 through VAL4 on the SFE command, and X,Y,Z are the global Cartesian coordinates at the current location of the point. For face 5, the magnitude of the pressure is P_I, and the direction is . The load may be adjusted with KEYOPTs(11) and (12).

Temperatures may be input as element body loads at the nodes. Element body load temperatures are not applied to other elements connected at the same nodes. The node I temperature T(I) defaults to TUNIF. If all other temperatures are unspecified, they default to T(I). If all corner node temperatures are specified, each midside node temperature defaults to the average temperature of its adjacent corner nodes. For any other input temperature pattern, unspecified temperatures default to TUNIF. Temperatures are used for material property evaluation only.

KEYOPT(5) is used when a pressure load is specified for the element and when asymmetry of load correction terms in nonlinear problems is important.

When KEYOPT(4)=0, an edge with a removed midside node implies that the displacement varies linearly, rather than parabolically, along that edge. See Section 2.4.2 of the ANSYS Modeling and Meshing Guide for more information about the use of midside nodes.

A summary of the element input is given in Table 4.154-1. A general description of element input is given in Section 2.1.

Table 4.154-1 SURF154 Input Summary

Element Name	SURF154
Nodes	I, J, K, L if KEYOPT (4) = 1 I, J, K, L, M, N, O, P if KEYOPT (4) = 0
Degrees of Freedom	UX, UY, UZ
Real Constants	(Blank), (Blank), (Blank), EFS, SURT, ADMSUA, TKI, TKJ, TKK, TKL
Material Properties	DENS, VISC, DAMP
Surface Loads	Pressures: face 1 (I-J-K-L) (in -z normal direction), face 2 (I-J-K-L) (tangential (+x)) face 3 (I-J-K-L) (tangential (+y)) face 4 (I-J-K-L) (in -z normal direction, global taper) face 5 (I-J-K-L) (oriented by input vector)
Body Loads	Temperatures: T (I), T ( J ), T ( K ), T( L ), and, if KEYOPT (4) = 0, T( M ), T( N ), T( O ), T(P)
Special Features	Stress stiffening, Large deflection, Birth and death
KEYOPT(4)	0 - Has midside nodes (that match the adjacent solid element) 1 - Does not have midside nodes
KEYOPT(5)	0 - Symmetric stiffness (default) 1 - Unsymmetric stiffness
KEYOPT(6)	Applicable only to normal direction pressure (faces 1 and 4): 0 - Use pressures as calculated (positive and negative) 1 - Use positive pressures only (negative set to zero) 2 - Use negative pressures only (positive set to zero)
KEYOPT(11)	Pressure applied by vector orientation (face 5): 0 - On projected area and includes tangential component 1 - On projected area and does not include tangential component 2 - On full area and includes the tangential component
KEYOPT(12)	Effect of the direction of the element normal (element z-axis) on vector oriented (face 5) pressure: 0 - Pressure load is applied regardless of the element normal orientation 1 - Pressure load is not used if the element normal is oriented in the same general direction as the pressure vector.

4.154.2 Output Data

• nodal degree of freedom results included in the overall nodal solution
• additional element output as shown in Table 4.154-2

The following notation is used in Table 4.154-2:

A colon (:) in the Name column indicates the item can be accessed by the Component Name method [ETABLE, ESOL] (see Section 2.2.2). The O and R columns indicate the availability of the items in the file Jobname.OUT (O) or in the results file (R), a Y indicates that the item is always available, a number refers to a table footnote which describes when the item is conditionally available, and a - indicates that the item is not available.

Table 4.154-2 SURF154 Element Output Definitions

Name	Definition	O	R
EL	Element number	Y	Y
SURFACE NODES	Nodes - I, J, K, L	Y	Y
EXTRA NODE	Extra node (if present)	Y	Y
MAT	Material number	Y	Y
AREA	Surface area	Y	Y
VOLU:	Volume	Y	Y
CENT: X, Y, Z	Center location XC, YC, ZC	-	Y
VN(X,Y,Z)	Components of unit vector normal to center of element	-	Y
PRES	Pressures P1, P2, P3, P4, P5 at nodes I, J, K, L	1	-
PZ, PX, PY	Pressures at nodes in element coordinate system (P5 uses an average element coordinate system)	-	1
DVX, DVY, DVZ	Direction vector of pressure P5	1	1
AVG. FACE PRESSURE	Average normal pressure (P1AVG), Average tangential-X pressure (P2AVG), Average tangential-Y pressure (P3AVG), Average tapered normal pressure (P4AVG), Effective value of vector oriented pressure (P5EFF)	1	1
TEMP	Surface temperatures T(I), T(J), T(K), T(L), T(M), T(N), T(O), T(P)	2	2
DENSITY	Density	3	3
MASS	Mass of element	3	3
FOUNDATION STIFFNESS	Foundation Stiffness (input as EFS)	4	4
FOUNDATION PRESSURE	Foundation Pressure	4	4
SURFACE TENSION	Surface Tension (input as SURT)	5	5

1. If pressure load

2. If temperature load

3. If dens>0

4. If EFS>0

5. If SURT>0

Table 4.154-3 lists output available through the ETABLE command using the Sequence Number method. See Chapter 5 of the ANSYS Basic Analysis Procedures Guide and Section 2.2.2.2 of this manual for more information. The following notation is used in Table 4.154-3:

Name - output quantity as defined in the Table 4.154-2

Item - predetermined Item label for ETABLE command

E - sequence number for single-valued or constant element data

I,J,K,L - sequence number for data at nodes I,J,K,L

Name	Item	E	I	J	K	L
PZ	SMISC	-	1	2	3	4
PX	SMISC	-	5	6	7	8
PY	SMISC	-	9	10	11	12
P1AVG	SMISC	13	-	-	-	-
P2AVG	SMISC	14	-	-	-	-
P3AVG	SMISC	15	-	-	-	-
P4AVG	SMISC	16	-	-	-	-
P5EFF	SMISC	17	-	-	-	-
FOUNPR	SMISC	21	-	-	-	-
AREA	NMISC	1	-	-	-	-
VNX	NMISC	2	-	-	-	-
VNY	NMISC	3	-	-	-	-
VNZ	NMISC	4	-	-	-	-
EFS	NMISC	5	-	-	-	-
SURT	NMISC	6	-	-	-	-
DENS	NMISC	7	-	-	-	-
MASS	NMISC	8	-	-	-	-
DVX	NMISC	9	-	-	-	-
DVY	NMISC	10	-	-	-	-
DVZ	NMISC	11	-	-	-	-

4.154.3 Assumptions and Restrictions

• The element must not have a zero area.
• The surface tension load vector acts in the plane of the element as a constant force applied to the nodes seeking to minimize the area of the surface.
• For structural large deflection analyses, the loads are applied to the current size of the element, not the initial size.
• Surface printout and foundation stiffness are not valid for elements deactivated [EKILL] and then reactivated [EALIVE]. Surface printout does not include large strain effects.

4.154.4 Product Restrictions

ANSYS/Structural

The only allowable material property is DENS.