5.1.14 Mesh-independent spot welds

Products: ABAQUS/Standard  ABAQUS/Explicit  

Features tested

This section provides basic verification tests for the *FASTENER and *FASTENER PROPERTY options.

I. Spot-welded plates subject to pressure and shear loading

Elements tested

S4    S4R   

Problem description

Rigid spot welds are defined between combinations of two or more plates comprised of three-dimensional shell elements. The spot weld options are used to test the various ways in which the user can define mesh-independent spot welds. The three ways in which the user can define the spot-welded surfaces are verified: the user does not specify any surface, the user specifies a single surface, or the user specifically lists the surfaces to be spot welded. The use of the SEARCH RADIUS parameter to limit the surface facets considered for spot welding is verified, along with the use of the RADIUS OF INFLUENCE, UNSORTED, and WEIGHTING METHOD parameters to control the distributing coupling definitions generated by the spot welds. In addition, user-specified projection directions are tested. Each combination is subjected to the same loading conditions. In the ABAQUS/Standard analyses the top plate is loaded with a uniform pressure. In the ABAQUS/Explicit analyses the top and bottom plates in each combination are subjected to displacements of =.1 and =–.1, respectively, along the plate edges parallel to the -axis.

Results and discussion

The results for each combination indicate that the surfaces are spot welded appropriately.

Input files

ABAQUS/Standard input files

fastener_projdir_s4.inp

Tests user-specified projection directions for spot welds with a single user-specified surface.

fastener_search_s4.inp

Tests the RADIUS OF INFLUENCE, SEARCH RADIUS, and NUMBER OF LAYERS parameters for spot welds with no user-specified surface.

fastener_unsort_weight_s4.inp

Tests the UNSORTED and WEIGHTING METHOD parameters with multiple user-specified surfaces.

ABAQUS/Explicit input files

xfastener_xpl_beammpcs.inp

Tests the various methods for defining mesh-independent spot welds using BEAM-type MPCs.

xfastener_xpl_connectors.inp

Tests the various methods for defining mesh-independent spot welds using both user-defined and internally generated connector elements.

II. Multi-layer spot welds between surfaces defined on various element types

Elements tested

S3    S4    S8R    STRI65   

Problem description

Various combinations of plates are spot welded to the faces of a bi-unit cube. These tests verify the ability of ABAQUS to accurately spot weld meshes of different element types. These tests also verify several features of the *FASTENER and *FASTENER PROPERTY options including: user-specified and free surface options, default and user-specified orientations and projection directions, multiple interactions, fastener property and reference node options, and fully constrained and released rotation constraints. These tests also verify the *INTERACTION OUTPUT and *INTERACTION PRINT options using various default and user-specified orientations.

Results and discussion

The results indicate that the fastener options tested are modeled correctly.

Input files

fastener_multilay_lin_std.inp

Plates spot welded to a cube with user-specified surfaces and orientations; static linear perturbation tests including multiple load cases.

fastener_multilay_lin_conn_std.inp

Plates spot welded to a cube with user-specified surfaces and orientations; static linear perturbation tests including multiple load cases. BEAM connector elements are used instead of BEAM-type MPCs.

fastener_multilay_lin_r1_std.inp

Plates spot welded to a cube with user-specified surfaces and orientations; rotation constraint in spot welds released in the local 3-direction; static linear perturbation tests including multiple load cases.

fastener_multilay_lin_r3_std.inp

Plates spot welded to a cube with user-specified surfaces and orientations; all rotation constraints in spot welds released; static linear perturbation tests including multiple load cases.

fastener_multilay_free_lin_std.inp

Plates spot welded to a cube with free and user-specified surfaces and orientations and user-specified projection directions; static linear perturbation tests including multiple load cases.

fastener_s4_multilay_std.inp

Plates spot welded to a cube with user-specified surfaces and orientations; static linear perturbation and geometrically nonlinear tests; S4 elements.

III. Single-layer spot welds between surfaces defined on various element types with varying mesh densities

Elements tested

S3    S4    S4R    S8R   

C3D4    C3D8R    C3D10M    C3D20R   

R3D3    R3D4   

Problem description

Individual plates are spot welded to the faces of a cube. These tests verify the *FASTENER, *INTERACTION OUTPUT, and *INTERACTION PRINT options in both perturbation and geometrically nonlinear analyses, including restart. These tests also verify fasteners on meshes of varying density.

Results and discussion

The results indicate that the fastener options tested are modeled correctly.

Input files

ABAQUS/Standard input files

fastener_s4_std.inp

Plates spot welded to a cube with user-specified surfaces and orientations; static linear perturbation, frequency extraction, direct and mode-based steady-state dynamic, and geometrically nonlinear tests; S4 elements.

fastener_s4_std_res.inp

Restart analysis of fastener_s4_std.inp; S4 elements.

fastener_s8r_std.inp

Plates spot welded to a cube with user-specified surfaces and orientations; static linear perturbation, frequency extraction, direct and mode-based steady-state dynamic, and geometrically nonlinear tests; S4 elements.

fastener_s3_c3d4_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S3 and C3D4 elements with varying mesh density.

fastener_s3_c3d8r_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S3 and C3D8R elements with varying mesh density.

fastener_s3_c3d10m_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S3 and C3D10M elements with varying mesh density.

fastener_s3_c3d20r_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S3 and C3D20R elements with varying mesh density.

fastener_s4r_c3d4_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S4R and C3D4 elements with varying mesh density.

fastener_s4r_c3d8r_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S4R and C3D8R elements with varying mesh density.

fastener_s4r_c3d10m_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S4R and C3D10M elements with varying mesh density.

fastener_s4r_c3d20r_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S4R and C3D20R elements with varying mesh density.

fastener_s8r_c3d4_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S8R and C3D4 elements with varying mesh density.

fastener_s8r_c3d8r_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S8R and C3D8R elements with varying mesh density.

fastener_s8r_c3d10m_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S8R and C3D10M elements with varying mesh density.

fastener_s8r_c3d20r_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; S8R and C3D20R elements with varying mesh density.

fastener_r3d3_c3d4_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; R3D3 and C3D4 elements with varying mesh density.

fastener_r3d4_c3d10m_std.inp

Plate spot welded to a cube with user-specified surfaces; single static step; R3D4 and C3D10M elements with varying mesh density.

ABAQUS/Explicit input files

xfastener_xpl_c3d10m_m3d4r.inp

Surface comprised of M3D4R membrane elements spot welded to surface comprised of C3D10M continuum elements.

xfastener_xpl_c3d4_r3d4.inp

Surface comprised of R3D4 rigid elements spot welded to surface comprised of C3D4 continuum elements.

xfastener_xpl_c3d8r_s3r.inp

Surface comprised of S3R shell elements spot welded to surface comprised of C3D8R continuum elements.

IV. Large deformation of a spot-welded beam

Element tested

S4   

Problem description

Two beams are spot welded together and subjected to various geometrically nonlinear deformations. These tests verify the *INTERACTION OUTPUT and *INTERACTION PRINT options in geometrically nonlinear analyses.

Results and discussion

The results indicate that the spot welds and output are modeled correctly.

Input files

fastenedbeam_s4_s4.inp

Spot-welded beams, S4 elements.

fastenedbeam_s4_s4_po.inp

Post output analysis of fastenedbeam_s4_s4.inp.

V. Spot welds used in various analysis techniques

Elements tested

C3D20R    S4R   

Problem description

The following examples verify that spot welds work with the following analysis techniques: mesh removal and activation (*MODEL CHANGE), submodeling, and substructures.

Results and discussion

The results of these tests indicate that spot welds and output are modeled correctly for these analysis techniques.

Input files

fastener_mdlc_s4r_c3d20r.inp

Geometrically nonlinear static and dynamic analyses (including element removal) of a spot-welded model consisting of S4 and C3D20R elements.

fastener_s4r_global.inp

Static analysis of a global model with spot welds, S4R elements.

fastener_s4r_submodel.inp

Static submodel analysis of fastener_s4r_global.inp with spot welds, S4R elements.

fastener_substr_gen.inp

Substructure generation file of a spot-welded model using S4R and C3D20R elements.

fastener_substr.inp

Substructure analysis of a spot-welded model using S4R and C3D8R elements; uses fastener_substr_gen.inp for substructure generation.

VI. Linear dynamics

Elements tested

C3D8    S4   

Problem description

A single shell element is spot welded to a single brick element. This model is analyzed using various linear dynamic procedures: steady-state dynamics (mode-based, direct, subspace), modal dynamics, random response, and spectrum response. The results of the spot-welded model are compared to similar models using connectors, beams, and distributing coupling elements. The MASS parameter on the *FASTENER PROPERTY option is also tested.

Results and discussion

Comparison of the spot weld model results to the results from a beam model indicates that the spot welds and output are modeled correctly.

Input files

fastener_lindyn.inp

Spot-welded model using S4 and C3D8 elements.

fastener_lindyn_connect.inp

Spot-welded model using S4 and C3D8 elements. BEAM connector elements are used instead of BEAM type MPCs.

fastener_lindyn_beam.inp

Spot-welded model using B31 and C3D8 elements.

fastener_lindyn_mass.inp

Spot-welded model using S4 and C3D8 elements and the MASS parameter.

VII. Compounded local coordinate systems

Elements tested

C3D8    S4   

Problem description

If a connector element is used to model a fastener, the local coordinate system defined on the connector section () operates on the local coordinate system for the fastener () to determine the final local coordinate system of the connector element (). In other words,

In the above equations and are assumed to be orthogonal rotation matrices with the local 1-, 2-, and 3-directions being the first, second and, third rows, respectively. The local coordinate system for a connector element modeling a fastener should be specified with respect to the local coordinate system of the fastener.

In the first example six flat shell structures are fastened independently to the six sides of a single brick element. HINGE connectors have been used with their local 1-directions set to be ; i.e., the local 3-direction of the fasteners. When compounded with the local coordinate system for the fasteners, the local 1-direction for the connector is normal to the surface. Thus, the shell structures are free to rotate about the surface normals.

In the second example six flat shell structures are again fastened independently to the six sides of a single brick element. TRANSLATOR connectors have been used. The local 1-directions (which are the slide direction for this type of connector: see Connector element library, Section 17.1.4 of the ABAQUS Analysis User's Manual) for the connectors have been set to the local 1-directions of the fasteners. For the four fasteners on the side, the local 1-directions coincide with the global 2-directions. For the two fasteners on the top and the bottom, the local 1-directions coincide with the global 3-directions. Thus, the fastened shell structures on the sides are free to translate in the global 2-directions, while the fastened shell structures on the top and bottom are free to translate in the global 3-direction.

Results and discussion

The results indicate that the local coordinate systems of the HINGE and TRANSLATOR connectors are modeled correctly.

Input files

fastener_connect_hinge.inp

Six flat shell structures fastened to a cube with user-specified surfaces; single static step; S4 and C3D8 elements. HINGE connector elements are used.

fastener_translator_hinge.inp

Six flat shell structures fastened to a cube with user-specified surfaces; single static step; S4 and C3D8 elements. TRANSLATOR connector elements are used.