Virtual Welding

Virtual Welding (VW) is an Expert Application of CASoft that covers the full thermo mechanical cycle of computations for welding processes. The development of VW was backed by numerical and experimental measures on welded coupons (see project WAM).
The final objectives of VW are to predict:
the process parameters that produce welded joints of Quality;
the ultimate strength of the welded joints.

The computed weld parameters are assembled into a Protocol for Quality that:
set the procedures for correct manufacturing;
set the parameters for the welding source;
The ultimate strength of the welded joints is of prime relevance for Structural Design as:
assigns the safety factors for the plates welded in the joint;
produces the least weight of the assembled structure, when cast into a Design by Analysis procedure.
VW is computationally very efficient:
the thermo mechanical models run within 1 min;
the ultimate strength models runs in real time.
Virtual Welding can be defined ; a 'digital welding technology'.
At times an interaction with simply instrumented experimental tests is required.The scalability of the VW models, though, reduces the interaction to new types of welding.

Here are some highlights on the Algorithms used.
Scaled Thermal Model
The Thermal Model cannot cover the full geometry of the plates : too big to compute.
Here the Model is scaled to 13% of the plate by applying two Algorithms:
- 2.5D Recursive Temperature (2.5T) : reduces the length on the axis of weld.
- Semi Infinite Boundary (SIB) : reduces the depth transverse to the axis;

Heat source
The heat source cannot be modeled by moving a point source : too rough a computation.
The melted zone needs a ‘footprint’ where to cumulate the heat of the source, to distribute back into the plate when cooling down into solid state.
The balance of heat must be accurate for the model to match the experimental data.
In CASoft such balance is accomplished with two Algorithms:
Footprint of Source (FOS): the user sets the area of the source in planar view;
OverMelt in the Plate (OMP): the melted area is remelted with new heat.
See the graphic rendering of the melted area at the peak Temperature (Fig. 2).

Bending Model
A joint welded with Quality parameters rotates under ultimate load forming a plastic hinge.
Such ductility is exploited in Design to reduce the local safety factor.
The ultimate load on the joint is computed with a solid mechanical model,
applying a nonlinear Moment (rotation) curve produced by the Algorithm: Post Weld Material (PWM):
(PWM) derives the Mom (rot) curve through an 'expert' modification of the plastic stress vs. plastic strain curve of the original material.