# Weld Evaluating problems and solutions

< Problem > Impossible to evaluate the weld quality at Designing stage before producing real welds and difficult to predict weld defects.

< Solution > Predict the weld nugget formation, hardness and micro structures, cracking risks and weld strengths by simulations.

< Principle > To ensure weld quality in terms of weld sizes, weld strengths and weld material properties around the weld without defect.

### Weld quality

Weld quality can be represented by various evaluation criteria such as weld nugget diameter, weld strength, and hardness and other properties after weld.

#### Weld nugget size

Weld nugget size is an essential measure of the weld quality. It is often used as a target for optimization of welding process parameters to find the optimal Weld time, current and force.

#### Hardness after welding

Hardness distribution after welding is critical for the performance of welds. The Hold time can affect the cooling rate thus change the hardness distribution after welding.

#### Weld strength

Weld strength is a performance of the weld quality. It is determined by the weld nugget size and material properties (mainly hardness and fracture) around the weld nugget.

With the newly added functions for simulations of the metallurgical properties and residuals, it is possible to predict the distribution of microstructures (martensite, bainite, pearlite/ferrite), distribution of hardness as well as residual stresses and cracking risks in the welds after welding.

The weld strengths are also calculated referring to the test methods described by the ISO standards including Cross Tension Strength (ISO 14272:2000), Shear Strength (ISO 14273:2000) and Peel Strength (ISO 14270:2000). So it is possible to optimize the welding process window and parameters according to the resulted weld strengths.

### Strength testing

A common method to evaluate the weld joint quality is by destructive testing to obtain the maximum breaking force in various loading modes and to obtain the failure modes (plug or interfacial failure).

SORPAS® 3D.testing can combine simulation of resistance welding process and mechanical joining with weld strength tests:

• Tensile shear test
• Cross tension test
• Axial tensile test
• Peel (or bending) test
• Torsion test