Zinc-based surface coatings are widely applied with high-strength steels in automotive industry. Some of these base materials show an increased brittle cracking risk during loading. It is necessary to examine electrogalvanized and uncoated samples of a high strength steel susceptible to liquid metal embrittlement during spot welding with applied external load. Therefore, a newly developed tensile test method with a simultaneously applied spot weld is conducted. A fully coupled 3D electrical, thermal, metallurgical and mechanical finite element model depicting the resistant spot welding process combined with the tensile test conducted is mandatory to correct geometric influences of the sample geometry and provides insights into the sample’s time dependent local loading. With increasing external loads, the morphology of the brittle cracks formed is affected more than the crack depth. The validated finite element model applies newly developed damage indicators to predict and explain the liquid metal embrittlement cracking onset and development as well as even ductile failure.

Thermal and mechanical loading, combined with zinc coating, are the primary factors influencing liquid metal embrittlement (LME) in the investigated advanced high-strength dual-phase steel, with a yield strength of 1200 MPa and high ductility during resistance spot welding. LME results in a ductility loss of up to 95% and is driven by an intergranular decohesion mechanism, leading to brittle failure in otherwise ductile steel. Validated numerical models provide deeper insights into the critical conditions during welding. The presented multi-physical model enables the optimisation of welding parameters, reducing experimental efforts and enhancing manufacturing efficiency. This study introduces new methods to reduce LME while improving overall weld quality. Surface-coated refractory electrodes significantly reduce embrittlement compared to standard copper electrodes. For copper electrodes, a newly developed shape minimises stresses and misalignment-induced stresses, further reducing embrittlement and enhancing weldability. Additionally, a mandatory holding time after welding effectively lowers embrittlement, while interrupted cooling creates critical conditions. Downward ramped current improves surface conditions, rendering the weld spot less susceptible to embrittlement.

This study examines the deformation behaviour of laser powder bed fusion-produced A20X aluminium alloy and its accurate representation using flow curve models that account for die–specimen friction. Tests across multiple strain rates at room temperature were conducted on a Gleeble 3800; force–displacement data were friction-corrected to derive constitutive flow curves. A mathematical model was developed to capture barrelling and its impact on the stress–strain response, yielding corrected stresses significantly lower than measured values and validating the correction. An equation linking key post-deformation geometric parameters to their mathematical representation correlated well with a calibrated 2D finite element model, which reliably predicted plastic strain and deformation. The model’s friction factors agreed with experimental data, enabling efficient determination of the friction coefficient. Microstructural analysis and micrographs supported the predicted plastic strain distributions. Together, the corrected experiments and validated simulations provide a robust description of A20X’s response and inform performance and application potential.

Compression testing combined with laser ultrasonics enables non-destructive, in situ material characterisation during thermo-mechanical loading, but the shortening and radial expansion of the specimen displace the laser focal points during deformation and therefore require active repositioning of the laser-ultrasonic optics. This work addresses this engineering problem by providing a modular positioning-control system that couples a Gleeble 3800 thermo-mechanical simulator and a laser-ultrasonic measurement unit. The Gleeble provides two analogue shaft-position signals, which are digitised and used as real-time reference signals for stage-position control. The excitation and detection optics are mounted on motorised Zaber linear stages; two stages translate the optics along the compression direction, while a third perpendicular stage adjusts the detection focus to compensate radial specimen expansion and the limited depth of field of the detection optics. The control software was implemented in Rust and computes the stage target positions from the digitised Gleeble voltages output using user-configurable mathematical expressions. It further provides process-data access through an embedded OPC UA server and a browser-based graphical user interface through an integrated HTTP server. A custom ADC-based acquisition chain was introduced because the built-in ADC inputs of the Zaber controllers showed a significant noise level when used for the Gleeble shaft-position signals. Profiling showed that the control-loop runtime was dominated by ADC read/write operations; by reorganising acquisition into a parallel setup, the mean control-loop time was reduced from approximately 130 ms to approximately 27 ms. The resulting system provides an active, configurable, and retrofit-capable link between Gleeble compression testing and laser-ultrasonic measurement. It improves the temporal response available for laser-focus tracking on deforming specimens and provides a foundation for future quantitative validation of tracking error, positioning uncertainty, and LUS signal quality during real compression experiments.

The apparent unloading modulus of sheet metals decreases with plastic pre-strain, and its directional dependence may affect springback prediction. This study investigates its directional evolution in CN4301-4307+2B, DOCOL780DP+AM, and WBS235JR using cyclic loading–unloading–loading tensile tests at 0°, 45°, and 90° to the rolling direction. The chord modulus is used as the primary definition and described using Yoshida relations. Two alternative unloading modulus definitions are evaluated to assess the robustness of the directional comparison. At ε_p = 0.08, the directional spread of relative modulus reduction is 14.56 percentage points for CN4301-4307+2B, 7.95 percentage points for WBS235JR, and 3.03 percentage points for DOCOL780DP+AM. The directional ranking is retained for all investigated definitions, although the spread magnitude depends on the definition. A controlled numerical roll forming sensitivity analysis shows a maximum difference of 0.58° in the mean F1–F3 opening angle relative to the constant modulus reference. The results indicate that a direction-independent unloading modulus relation may neglect relevant directional effects and affect predicted springback geometry. When a single uniaxial relation is used in roll forming simulations, the 90° response may provide a physically motivated basis for the predominantly transverse cross-sectional bending.

The apparent unloading modulus of sheet metals decreases with plastic pre-strain, and its directional dependence may affect springback prediction. This study investigates its directional evolution in CN4301-4307+2B, DOCOL780DP+AM, and WBS235JR using cyclic loading–unloading–loading tensile tests at 0°, 45°, and 90° to the rolling direction. The chord modulus is used as the primary definition and described using Yoshida relations. Two alternative unloading-modulus definitions are evaluated to assess the robustness of the directional comparison. At ε_p=0.08, the directional spread of relative modulus reduction is 14.56 percentage points for CN4301-4307+2B, 7.95 percentage points for WBS235JR, and 3.03 percentage points for DOCOL780DP+AM. The directional ranking is retained for all investigated definitions, although the spread magnitude depends on the definition. A controlled numerical roll-forming sensitivity analysis shows a maximum difference of 0.58° in the mean F1–F3 opening angle relative to the constant-modulus reference. The results indicate that a direction-independent unloading-modulus relation may neglect relevant directional effects and affect predicted springback geometry. When a single uniaxial relation is used in roll-forming simulations, the 90° response may provide a physically motivated basis for the predominantly transverse cross-sectional bending.