Incommensurate vibro-acoustic performance due to in-process blank holder force variation during deep drawing process

Abstract

Single-stage forming is widely used in automobile industry due to less cycle times, cost-effectiveness and ease of implementation. The continuously adaptable blank holder force (BHF) systems help produce defect-free components during the deep drawing process. However, this manufacturing process induces a significant amount of variability both at geometry and functional performance of the component. A systematic investigation of the effect of small geometrical changes on the vibro-acoustic properties is carried out using a combination of simulations and experiments. The influence of BHF and friction coefficient on vibro-acoustic properties is investigated through forming simulations. The forming analysis results—geometry profile and thinning—are used as an input to predict the vibro-acoustic behaviour of the formed component. The small geometric profile and thickness variations are significant and affect radiated noise-directivity pattern and sound power levels by 1.4 dB. Two physical components are manufactured using a single-stage deep drawing process. The natural frequencies and mode shapes obtained in free-free boundary conditions vary between the two components up to 20% for the first six flexible modes. The sound power levels between the actual parts varied by 2 dB(A). Finally, it is shown that the vibro-acoustic variability is more pronounced at higher frequencies.