B8 - Grinding Strategies

Grinding Strategies for Local and Stress Orientated Subsurface-modification of Sheet-Bulk Metal Forming Tools

Project Status: finished

Last Update: 19.10.2020

Members

Proposer

• Prof. Dr.-Ing. Berend Denkena

Head of Project

• Prof. Dr.-Ing. Berend Denkena

Researcher

• M. Sc. Michael Keitel
• Dipl.-Ing. Henning Lucas (until 31.07.2019)

During the sheet-bulk metal forming (SBMF) process, the forming tool is under locally varying tensile and compressive loads. In superposition with these load stresses, the residual stresses in the subsurface of the tool caused by manufacturing can promote or delay fatigue of functionalized parts of the tool. Especially for the SBMF a local optimization of the residual stresses in the subsurface is essential to endure the high loads and therefore the design of a reliable SBMF-process. The grinding process is one of the last and quality determining manufacturing steps and can be used to achieve a specific residual stresses state tailored to endure the stress conditions in the metal forming process. The target of this subproject is a significant increase of durability of the sheet-bulk metal forming tool through locally optimized residual stresses and thus guarantee the reliability of the sheet-bulk metal forming process.

The basic correlations between the grinding process and the residual stresses in the subsurface were the focus of the research at the first phase of the project (second application phase of the TCRC). The three main parameters influencing the residual stresses were found and an empirical model was derived. This can be used to induce a desired residual stress profile through the grinding process. The main target of the third funding period is to develop all necessary scientific data to ensure process reliability of the manufacturing and regeneration of the sheet-bulk metal forming tool with optimized subsurface properties.

Therefore, the following insights have to be acquired: As first sub-target the influence of the contact zone between the grinding tool and the workpiece has to be clarified. The contact zone varies depending on path distance, feed and angle of attack of the toric tool and has to be considered for the manufacturing of the workpiece. The second sub-target is to research the formation of subsurface transition zones between two differently processed workpiece parts. The loads of the metal forming process do not change abruptly from one tool part to another. Because of that it is necessary to produce a continuous, locally load adjusted residual stress profile everywhere on the forming tool. Thirdly the process reliability of the grinding process has to be guaranteed. To achieve this, production related variability and the wear behavior of the grinding tools will be investigated to develop appropriated dressing strategies to compensate this behavior. The fourth sub-target is an adjustment of the manufacturing process taking the effect of reinforcements of the SBMF-tools into consideration. The preload of the reinforcement changes the subsurface stress state, which will result in interactions with the manufacturing process. These interactions will be analyzed and the manufacturing strategies correspondingly adjusted. After reaching all these four sub-targets all findings will be combined in the fifth sub-target and used for a computer-aided path planning for locally adjusted subsurface optimization. For the manufacturing of complex geometries, like in SBMF, a computer-aided path planning is absolutely essential. The path planning has to consider the required local residual stress state and adjust process parameters accordingly. The last sub-target is the adjustment of the grinding strategies as a regeneration measure for worn and coated tool components. The hard coating has to be removed and optimized subsurface properties have to be reestablished in the substrate before it can be recoated. To minimize the amount of material removal, the grinding strategy has to be based on the load history of the tool.

Working Groups

• Materials
• Tools

Publications