Experimental Design and Validation Framework for Resistance Spot Welding of DP780 and DP980 Steels

A numerical process optimum becomes an engineering recommendation only after its material identity, measurement basis and physical performance have been established. This paper proposes an experimental and validation framework for resistance spot welding of DP780 and DP980 dual-phase steel sheets. It is a methods protocol derived from an AHSS welding thesis, not a report of completed experiments. The framework separates material qualification, pilot-domain selection, model-building experiments, destructive response measurement and independent confirmation. A three-factor Box–Behnken layout is proposed for current, weld time and electrode force, subject to machine-specific pilot qualification. The preferred common sheet thickness is 1.2 mm, but procurement and coating compatibility must be verified before the design is fixed. Separate specimens are allocated to tensile-shear, cross-tension and metallographic routes so that destructive tests are not misrepresented as repeated measurements on one weld. The protocol defines traceable specimen identifiers, randomization within feasible blocks, centre-point monitoring, data-exclusion rules and model-diagnostic gates. An illustrative workload calculation shows that three specimens for each of two mechanical routes at seventeen design rows across two grades requires 204 welded coupons before pilot, microscopy and confirmation allocations. Numerical results in the source thesis remain explicitly synthetic and are used only to identify candidate questions. The principal output is an auditable chain of evidence through which future measurements could support or reject a model-selected schedule. No actual optimum, material superiority or qualification outcome is claimed.