Advances in the application of the boundary element method to the thermal analysis of hot stamping tools considering solid-to-solid heat transfer

The boundary element method (BEM) has proven to be a useful method for the simulation of the time-averaged, quasi-stationary working temperature of hot stamping tools in early design phases [1] and for the optimization of the tempering duct positions [2]. In this context, the reduction of the volume model of a tool design to a surface model is an advantage in terms of model complexity, meshing effort and also file size.
In this work, the method has been enhanced for the thermal simulation of hot stamping tools including heated tool segments. This so called “soft-zone” tooling approach is a common method to produce components with tailored properties. Between the contacting segment faces, the heat transfer across the interfacial layer (e.g. air gap, direct contact, isolation) is modeled with a cou-pling condition based on a constant solid-to-solid heat transfer coefficient. Thus, the analysis of the temperature distribution at the contacting segment faces is now possible using the BEM.
A study on the influence of the interfacial layer on the working temperature of a soft-zone tool was performed. Selected temperature results were applied to the tool model of a full hot stamping simulation as boundary condition to demonstrate the applicability of the proposed solution in a CAE-driven tool design.

[1] Weiß, W.; Kolleck, R.; Schanz, M.; Messner M.: Application of the Boundary Element Method to the Thermal Analysis of Hot Forming Tools. IDDRG 2013 Conference Proceedings. Mumbai, 2013.
[2] Weiß, W.; Koplenig, M.; Alb, M.; Graf, J.: Virtual method for the determination of an optimum thermal design of hot stamping tools. IDDRG 2016 Conference Proceedings. Linz, 2013.