Multi-objective optimization of sheet hydroforming parameters for AISI 1008 low carbon steel using Taguchi-based grey relational analysis

Production Engineering & Metallurgy College, University of Technology-Iraq, Baghdad 10066, Iraq

Published online: 24 June 2026

Abstract

Sheet hydroforming is a flexible and cost-effective forming process capable of producing complex sheet metal components with high dimensional accuracy and improved mechanical performance. In this study, the influence of key process parameters on the multi-objective performance of AISI 1008 low carbon steel sheet was investigated using a combined Taguchi design and Grey Relational Analysis (GRA) approach. Three controllable parameters—sheet thickness (0.48, 0.68, and 0.88 mm), punch stroke speed (2, 5, and 10 mm/min), and hydraulic fluid viscosity (20W–50, 50 SAE, and 70 SAE)—were examined at three levels each using an L27 experimental matrix. The output responses considered were maximum dome height, thickness at the pole region, and micro-hardness (HV0.2). The experimental results revealed that dome height varied from 25.68 mm to 37.16 mm, pole thickness ranged between 0.299 mm and 0.637 mm, and micro-hardness values increased from 152.9 HV0.2 to 193.3 HV0.2 depending on the parameter combination. Grey relational analysis identified Experiment 27 as the best-performing condition with a Grey Relational Grade (GRG) of 0.806. Analysis of variance (ANOVA) indicated that sheet thickness was the most significant factor, contributing 89.6% to the overall performance variation, followed by stroke speed (4.1%) and viscosity (3.2%). The optimal parameter combination was determined as 70 SAE viscosity, 0.88 mm thickness, and 10 mm/min speed. Under these conditions, superior multi-performance characteristics were achieved, confirming the effectiveness of the integrated Taguchi-GRA optimization methodology for sheet hydroforming applications.