CQUAD4-Element

The CQUAD4-element is the recommended element type to use for a weld evaluation with WeldFEM. The thickness of the element is given as a property information.
The normal stress components σx and σy as well as the shear stress component τxy are values that result from a FE-analysis. Both, normal and shear stress components are defined in the local coordinate system of the element. The creation of the CQUAD4-element local coordinate system is shown below.



For the assessment of welds stresses are to be evaluated in components in the local weld coordinate system. In order to calculate the weld stress components for the assessment a transformation of the extracted stress components is required. This calculation step is done by WeldFEM automatically, thus the engineer does not bother to transform the stresses manually neither to orient the element coordinate system of every element in the evaluation range according to the local weld coordinate system.


SPRING/DAMPER-Element

The SPRING/DAMPER-element can be used in different ways, depending on what its purpose is supposed to be. In case of a weld evaluation with WeldFEM SPRING/DAMPER-element are used as dummy-elements to define welds. In addition to that they are used to save weld specific information in the FE-model to be evaluated. That information is stored in the element properties name, which is structured according to a specified notation. An example is shown below.


Example:        T|a|17.5|25.0-25.0|F3.E4|H-|S235J|st
A fillet weld at a corner joint with an effective cross-section value of 17,5 mm. Both of the welded plates have a thickness of 25 mm. F3 has been chosen for the perpendicular normal stress MKJ-σ, E4 for the parallel normal stress MKJ-σ and H- for shear stress MKJ-τ. The weld is made out of S235J, which is a steel based alloy.


Note:        The same notation is used in the tables of WeldFEM.


Note:        The SPRING/DAMPER-element as generated by WeldFEM posses a small torsional damping, see picture below.
With this setting further static analysis with the FE-model modified by WeldFEM may be performed without having issues. Although the SPRING/DAMPER-elements do not affect a static calculation it is recommended to follow the steps mentioned in  General Procedure For Weld Assessment.
When re-running dynamic analyses the torsional damping value should be revised as it will have an effect on the results of the FE-calculation.



RBE2-Element

The RBE2-element (Rigid Body Element, Type 2) is not typical element. It uses constraint equations to couple the motion of two or more nodes.
RBE2-elements are often used to simulate weld-like connections. Therefore WeldFEM will detect connections created with those types of elements.

Examples of welds being modelled with RBE2-elements are shown in Weld Detection Considerations.


Note:        So called "spider" rigid elements which couple an independent centre node to a set of dependent nodes are recognised by WeldFEM skipped in the weld detection process.