The primary goal of this study was to investigate the formability of Nimonic 90 sheet which performs well at high temperatures and pressures, making it ideal for applications in the aerospace, processing, and manufacturing industries. In this present study, finite element analysis (FEA) and optimization of process parameters for formability of Nimonic 90 in sheet hydroforming were investigated. The material’s mechanical properties were obtained by uniaxial tensile tests as per the standard ASTM E8/E8M. The sheet hydroforming process was first simulated to obtain maximum pressure (53.46 MPa) using the FEA and was then validated using an experiment. The maximum pressure obtained was 50.5 MPa in experimentation. Since fully experimental or simulation designs are impractical, the Box–Behnken design (BBD) was used to investigate various process parameters. Formability was measured by the forming limit diagram (FLD) and maximum deformation achieved without failure. Analysis of variance (ANOVA) results also revealed that pressure and thickness were the most effective parameters for achieving maximum deformation without failure. Response surface methodology (RSM) optimizer was used to predict optimized process parameter to achieve maximized response (deformation) without failure. Experimental validation was carried out for the optimized parameters. The percentage of error between experimental and simulation results for maximum deformation was less than 5%. The findings revealed that all the aspects in the presented regression model and FEM simulation were effective on response values.

Crack widths are important considerations in both serviceability and durability design of concrete structures and should be evaluated to ensure compliance with design limits. However, existing empirical formulas for maximum crack width prediction are discrepant with each other, and they cannot reveal key information such as crack number and crack spacing. To obtain such information, finite element analysis has to be adopted. However, conventional finite element analysis has its limits in carrying out crack analysis. Particularly, the common smeared crack models, which do not realistically reflect bond-slip of reinforcing bars, would not give correct crack widths. In contrast, the discrete crack models are difficult to apply because of the need to adaptively generate discrete crack elements according to the cracks formed during the loading process. In this paper, a pseudo-discrete crack model is developed for finite element implementation. The conventional smeared crack model is transformed and reformulated, and a novel crack queuing algorithm is introduced for crack analysis. The method has been applied to analyse concrete beams in the literature. It is demonstrated that the computational results of crack number, spacing and widths agree closely with the measured results. KEYWORDSCrack width, crack queuing algorithm, pseudo-discrete crack model, finite element analysis.