Material Characterisation, Modelling, and Validation of a UHSS Warm-Forming Process for a Heavy-Duty Vehicle Chassis Component

The lightweighting of heavy-duty vehicles (HDVs) is an effective strategy to reduce fuel consumption and lower CO2 emissions in the transport sector. The widespread application of ultra-high-strength steels (UHSSs) in HDV construction offers a viable solution, particularly for thick-walled chassis components. This study aimed to support the lightweighting of heavy vehicles by developing a methodology capturing the entire warm-forming process in the range of 430–580 °C for thick-walled UHSSs—from material characterisation, including elastoplastic and fracture properties, to downstream forming process simulations. A novel 7 mm thick UHSS grade, WARMLIGHT-980 (ultimate tensile strength (UTS) of 980 MPa), intended for warm forming was investigated at 430, 505, and 580 °C using samples of reduced thickness. The results showed that thickness reduction had minimal influence on mechanical response at elevated temperatures, enabling flexible specimen design. The thermal uniformity improved in thinner samples, enhancing testing reliability. The calibrated hardening and fracture models demonstrated strong agreement with experimental data. Validated simulations of thick-walled components confirmed the accuracy of the modelling approach. The findings support the development of reliable, temperature-dependent models for warm-forming applications and contribute to the design of lighter, more sustainable HDV components without compromising structural integrity.