C. Acht's research while affiliated with E.ON and other places

Publications (11)

Article
Kurzfassung Der Sonderforschungsbereich 570 „Distortion Engineering – Verzugsbeherrschung in der Fertigung“ an der Universität Bremen hat sich als ein Ziel die Bestimmung signifikanter Einflussgrößen und Wechselwirkungen auf den Verzug über die gesamte Fertigungskette von ausgewählten Bauteilen gesetzt, um die wesentlichen Mechanismen der Verzugsen...
Article
The Collaborative Research Centres 570 “Distortion Engineering - Distortion Control in the Production Process” focuses on the determination of significant factors and interactions in the overall production process of selected components to identify relevant distortion mechanisms. In this context, computer simulations are more and more important for...
Article
Full-text available
The Collaborative Research Centres 570 "Distortion Engineering - Distortion Control in the Production Process" focuses on the determination of significant factors and interactions in the overall production process of selected components to identify relevant distortion mechanisms. In this context, computer simulations are more and more important for...
Article
This paper presents an ultrasonic method to measure the movement of workpiece surfaces during quenching processes in liquids in order to estimate the time-dependent in-process distortion of the workpiece. The movement is determined by the time-of-flight of the ultrasonic signals from the transducer to the surface and back again (impuls-echo-method)...
Article
In order to detect the most important influencing factors on distortion in carburising processes, it is helpful to use a simulation tool. Additionally, design of experiments (DoE) can help to perform the needed simulations in a well structured, clearly arranged manner.The objective of this work is to detect the influencing factors of carburising pr...
Article
During the important industrial process of case hardening, phase transformations in a steel workpiece are essentially influenced by the (non-homogeneous) carbon distribution (near the surface). Moreover, the temperature course is of great importance. We develop a mathematical model of case hardening which takes into account diffusion of carbon in a...
Conference Paper
Der beim Härten in Ölbädern ausgelöste Verzug von einsatzgehärteten Stahl-bauteilen ist abhängig von bauteil-, werkstoff- und verfahrensspezifischen Fak-toren wie z.B. dem Kohlenstoffgradienten in der Randschicht. Außerdem beein-flusst auch der zeitliche Verlauf der Benetzung der Bauteiloberfläche mit dem Abschreckfluid die Form und den Grad des Ve...
Article
Dr.-Ing. Thomas Lübben, geb. 1959, studierte Physik an der Universität Bremen. Seit 1986 ist er als Wissenschaftlicher Mitarbeiter in der Stiftung Institut für Werkstofftechnik in Bremen tätig und arbeitet hier auf dem Gebiet der Abschrecktechnik. Seit 2001 ist er Geschäftsführer des SFB 570 und Teilprojektleiter im Projekt A6. apl. Prof. Dr.-Ing....
Article
The carburization of steel parts changes the chemical composition in the surface. According to the change of chemical composition a change in density occurs. If the change in density is distributed in an asymmetrical way, distortion can not be avoided. In order to find out the effects of specifying factors on distortion, several finite element sim...
Article
In the presented research paper the distortion behaviour of components is analysed. Therefore, a large number of discs with inner bores of 20MnCr5 steel was used as a model geometry for simplification of gears. Altogether, six different variations in dimensions were used, where two different heights and three different outer diameters were combined...

Citations

... However, the real challenge lies in the determination of the densities of phases at high temperatures. High-temperature density information is usually calculated using a combination of a density measurement at a reference temperature (typically room temperature) and quenching dilatometer measurements of linear expansion of the material during heating-cooling cycles ( Ref 121,[180][181][182]. However, this method may give erroneous results if the linear expansion of the material is anisotropic ( Ref 147,148,184,185), as most dilatometers measure either the length or the diameter of the specimen only ( Ref 186). ...
... Für eine ganzheitliche numerische Betrachtung der Prozesskette der Warmumformung ist es zudem notwendig, eine Vielzahl weiterer Werkstoffparameter phasenspezifisch in die Simulation einzubeziehen, um die Polymorphie des Stahls korrekt abzubilden. Da eine experimentelle Bestimmung vieler Werkstoffparameter für die reine Gefügephase schwierig ist[25], wird die thermodynamische Berechnungssoftware JMatPro[26] eingesetzt. Mit Hilfe dieser Software werden, basierend auf empirischen Gleichungen, anhand der chemischen Zusammensetzung der Legierung phasenspezifische und temperaturabhängige Werte für spezifische Wärmekapazität, Wärmeleitfähigkeit, Wärmeausdehnungskoeffizient, Dichte, E-Modul, Poissonzahl, latente Wärme und Härte berechnet. ...
... The thermo-metallurgic-mechanical simulation in Sysweld ® was performed in accordance to the models provided in the reference manual, see [34]. Further details on the modeling of the quenching process, in order to evaluate the local phase proportions, as well as hardness, distortion, and residual stress conditions are given in [34][35][36][37][38]. Utilizing these models, the residual stress state during, and more importantly, at the end of the IH process was numerically computed, which acts, in addition to the hardness condition, as a significant input for the local fatigue analysis at the final stage of the numerical assessment methodology. ...
... The same experiments were simulated using another tool by Prantil et al. (2003). After that, Acht et al. (2005) experimented and simulated distortions in steel discs carburised on a single side and oil-quenched. For confirming and supplementing the results by Larson and Acht et al., Arimoto et al. (2008) experimented with plates and discs under somewhat different conditions. ...
... Thus, possibility of reducing the total number of parameters describing the local temperature dependencies, is investigated. A 3 factor (K, n, m) and 2 level (locally temperature dependent / independent) full factorial Design of Experiments (DoE) is performed inspired from the sensitivity analysis of Acht et al. [30]. ...