Entwicklung eines multimodalen Prozessmodells zur Oberflächenkonditionierung beim Außenlängsdrehen von 42CrMo4

Ziel der Arbeit ist es, Prozessmodelle zur Vorhersage und Beeinflussung von Randschichtzuständen zu identifizieren, um die Regelung des Außenlängsdrehens von 42CrMo4 zu ermöglichen. Als Modelleingangsgrößen sollen die Schnittgeschwindigkeit, der Vorschub, die Schnitttiefe, die Trocken- und die Nasszerspanung, die Anlasstemperatur des Werkstücks sowie der Schneideckenradius und die Verschleißmarkenbreite des Werkzeugs berücksichtigt werden. Ziele der Prozessregelung sind die Einstellung einer gewünschten Oberflächenrauheit, die Einstellung einer vorwiegend durch Kornfeinung und Kaltverfestigung induzierten Randschichthärtung sowie die Einstellung von Druckeigenspannungen an und unter der Oberfläche. Für die Oberflächenrauheit soll ein quantitatives Modell der gemittelten Rautiefe identifiziert werden. Die Randschichtverfestigung soll durch Vickers Mikrohärtemessungen quantifiziert und ebenfalls modelliert werden. Die Tiefenverläufe der axialen und der tangentialen Normalspannungen werden durch geeignete Kennwerte charakterisiert und modelliert. Weiterhin soll ein recheneffizientes FE-Modell zur Simulation von Eigenspannungen entwickelt werden, das auf thermomechanischen Werkstücklasten beruht. Damit sollen Tendenzen des analytischen Eigenspannungsmodells mittels Mechanismenwissen erklärt und bestätigt werden

The present state of surface conditioning in cutting and grinding

All manufacturing processes have an impact on the surface layer state of a component, which in turn significantly determines the properties of parts in service. Although these effects should certainly be exploited, knowledge on the conditioning of the surfaces during the final cutting and abrasive process of metal components is still only extremely limited today. The key challenges in regard comprise the process-oriented acquisition of suitable measurement signals and their use in robust process control with regard to the surface layer conditions. By mastering these challenges, the present demands for sustainability in production on the one hand and the material requirements in terms of lightweight construction strength on the other hand can be successfully met. In this review article completely new surface conditioning approaches are presented, which originate from the Priority Program 2086 of the Deutsche Forschungsgemeinschaft (DFG)

Cryogenic orthogonal turning of Ti-6Al-4V – Analysis of nitrogen supply pressure variation and subcooler usage

Cooling of machining operations by liquid nitrogen is a promising approach for reducing cutting temperatures, increasing tool life and improving the workpiece surface integrity. Unfortunately, the cooling fluid tends to evaporate within the supply channel. This induces process variations and hinders the use of nitrogen cooling in commercial applications. In this work, the coolant is applied via the tool’s rake face during orthogonal turning of Ti-6Al-4V. The effect of a nitrogen supply pressure adjustment and a subcooler usage—proposed here for the first time for machining—is analyzed in terms of process forces, tool temperatures and wear patterns, taken dry cutting as a reference. Thereby, reliable cooling strategies are identified for cryogenic cutting

Material parameter optimization for orthogonal cutting simulations of AISI4140 at various tempering conditions

The mechanical parameters of quenched and tempered AISI4140 and the machining process characteristics are depending on the material’s tempering state. The process characteristics of practical relevance are not only the cutting forces and the tool wear, but also the surface layer states of the machined part. In order to predict and to improve these characteristics efficiently, chip forming simulation via finite element method (FEM) is commonly applied. However, an issue in machining simulation which is often addressed is choosing appropriate material parameters for the flow stress model. This especially accounts for AISI4140 with various tempering conditions, as in many cases the precise heat treatment is not supplied in detail, even in scientific literature. In this work, orthogonal cutting of AISI4140 with tempering temperatures of 300°C, 450°C and 600°C is investigated by experiments and FE simulations. The Johnson-Cook flow stress model is used in the FE simulation. The referring material parameters for the tempering conditions are iteratively adapted via numerical optimization to fit experimental cutting forces. The obtained parameters are compared to literature values in order to prepare a common ground for the cutting simulation of AISI4140. This contributes to an enhanced process modelling when machining AISI4140 with use-case adapted heat treatments

The Present State of Surface Conditioning in Cutting and Grinding

All manufacturing processes have an impact on the surface layer state of a component, which in turn significantly determines the properties of parts in service. Although these effects should certainly be exploited, knowledge on the conditioning of the surfaces during the final cutting and abrasive process of metal components is still only extremely limited today. The key challenges in regard comprise the process-oriented acquisition of suitable measurement signals and their use in robust process control with regard to the surface layer conditions. By mastering these challenges, the present demands for sustainability in production on the one hand and the material requirements in terms of lightweight construction strength on the other hand can be successfully met. In this review article completely new surface conditioning approaches are presented, which originate from the Priority Program 2086 of the Deutsche Forschungsgemeinschaft (DFG)