Matthias Brockmann

Analytical Modelling of Temperature Distribution Using Potential Theory by Reference to Broaching of Nickel-Based Alloys

Knowledge of temperature fields and heat flow evolving during metal cutting processes is of significant importance for ensuring and predicting the product`s quality. Furthermore, this knowledge enables an improved usage of resources, such as machine tools and tool deployment. The strength of the heat sources as a result of the process and the distribution of the temperature in the material directly influence the tool wear mechanisms, wear rate, thermo-elastic deflection of the tool centre point and the amount of heat flowing into the newly generated work piece surface. Especially the latter effect is of crucial importance when it comes to safety critical components as they are employed in aero-engines. In aviation industry, the surface integrity is used as a complex quality measure summarising several aspects at the machined surface and sub-surface out of which many issues are predominantly thermal issues (e.g. temperature driven hardening of the work piece material, re-cast and white etching layers as well as residual stress profiles).

Introduction to integrative production technology

Production technology is a highly interdisciplinary field of research. It comprises different production domains (cutting, welding, forming, assembly, etc.), industry-sectors, materials and scales. Moreover, production has strong interdependencies with other scientific disciplines such as product development, materials engineering, business economics, information and communication technology, social science and natural science. Integrative Production Technology aims to develop a deep technology spanning perception to offer products matching customer and societal demands at competitive prices and to quickly adapt to market and societal changes while assuring constant and predictable product properties. The Cluster of Excellence (CoE) “Integrative Production Technology for High-Wage Countries” has initiated this special issue to present some of the newest results in the field. For a wider summary of results, the reader may refer to the recently published book of the CoE (Brecher and Özdemir, Integrative production technology: theory and applications. Springer, Cham, 1).

Modelling of transient thermal conditions in cutting

The thermal conditions like the temperature distribution and the heat fluxes during metal cutting have a major influence on the machinability, the tool lifetime, the metallurgical structure and thus the functionality of the work piece. This in particular applies for manufacturing processes like milling, drilling and turning for high-value turbomachinery components like impellers, combustion engines and compressors of the aerospace and automotive industry as well as energy generation, which play a major role in modern societies. However, numerous analytical and experimental efforts have been conducted in order to understand the thermal conditions in metal cutting, yet many questions still prevail. Most models are based on a stationary point of view and do not include time dependent effects like in intensity and distribution varying heat sources, varying engagement conditions and progressive tool wear. In order to cover such transient physics an analytical approach based on Green’s functions for the solution of the partial differential equations of unsteady heat conduction in solids is used to model entire transient temperature fields. The validation of the model is carried out in orthogonal cutting experiments not only punctually but also for entire temperature fields. For these experiments an integrated measurement of prevailing cutting force and temperature fields in the tool and the chip by means of high-speed thermography were applied. The thermal images were analyzed with regard to thermodynamic energy balancing in order to derive the heat partition between tool, chips and workpiece. The thus calculated heat flow into the tool was subsequently used in order to analytically model the transient volumetric temperature fields in the tool. The described methodology enables the modeling of the transient thermal state in the cutting zone and particular in the tool, which is directly linked to phenomena like tool wear and workpiece surface modifications.

Model and Method for the Determination and Distribution of Converted Energies in Milling Processes

This paper summarises the current state of project research focussing on the energy model for milling processes. The general methodology of heat flux determination is described in detail. An analytical temperature distribution model that has been engineered in a subproject is presented as an initial result. The potential theory provides complex solutions for the differential equation of thermal conduction that make available temperature field and heat flux field at the same time. The models were validated by means of the temperature fields measured. An online calibration method combining an infrared camera with a two-colour pyrometer was developed to ensure the quality of the captured data. Finally, the principal paradigm of determining heat fluxes from the temperature models is briefly introduced.

Process Monitoring for Manufacturing of Critical Aero Engine Components: An Overview

Modern production systems stand out due to an increasing degree of capacity utilization of the efficiency available through the production process. As working on a technological threshold as well as on a complex task comes along with an increase of susceptibility to failure, process monitoring is an important means to avoid damage to machines, tools, and component parts and a consequent machine downtime. In order to bring about detection of tool breakage, overload and tool wear, we use different sensor and monitoring systems which are adjusted to the process in the best possible way. This paper gives an overview of existing process monitoring solutions, especially in the field of aero engine manufacturing.© 2014 ASME