The thermomechanical interaction of the tool with the chip in the most loaded secondary cutting zone depends on the contact length of the tool rake face with the chip. Experimental studies of the dependency of the contact length on the cutting speed, the undeformed chip thickness, and the tool rake angle, performed by the optical method, are used for comparison with the contact length obtained by the FE modeling of the orthogonal cutting process. To determine the parameters of the constitutive Johnson–Cook equation, which serves as a material model of the FE cutting model that has a predominant influence on the contact length, a software-implemented algorithm was developed. This algorithm is based on determining the generalized parameters of the constitutive equation through finding the intersection of these parameter sets. The plurality intersection of the parameter sets of the constitutive equation is determined by means of the design of experiments and refined by subsequent multiple iterations. The comparison of the contact length values, obtained by simulating the cutting process using the generalized parameters of the constitutive equation as a material model with their experimental values, does not exceed 12% for a wide range of cutting speeds and depths of cut, as well as for the tool rake angle.
Wood materials are an important part of our daily life. Besides furniture, doors and window elements, parquet floors, veneering, ply wood, chip- and fibreboards, also structural elements for buildings are typical products. Due to the specific properties, variety and complexity of natural wood, wood materials and wood composites, the machining of parts made out of these materials exhibits specific challenges. In order to further improve productivity, quality and efficiency in wood machining, innovative solutions with respect to tool technology, process planning, machinery, process monitoring and intelligent control are necessary. This keynote paper reviews and summarizes scientific developments in wood machining in recent years. Furthermore, exemplary current an ongoing research activities are introduced. Finally, the paper presents and discusses future potentials regarding new approaches for intelligent process control in wood machining.
The simulation of machining processes holds the opportunity for process improvement on many levels. Possible benefits that can be derived from accurate representations of the real processes on the tool from simulations include a prediction of tool wear, the shape of the chips produced, the forces, frictions and temperatures that arise and the residual stresses in the workpiece. These predictions can be used to improve the process in terms of its economic and ecological behaviour: Increasing the service life of the tools used through an improved understanding of the tool-workpiece interaction. The finite element method (FEM), among others, has emerged as a common method for simulating these processes. When simulating machining processes using FEM, a major challenge is to avoid or compensate for the mesh distortions caused by the massive, fast-moving deformation processes, but at the same time to allow the mesh to be discretised in some way to ensure chip removal. To this end, various approaches will be presented in the course of this work and the mesh-based approaches will be explored in depth. Among other things, a remeshing approach for these investigations was developed. The machining of TI6AL4V is used to illustrate these approaches, as its tendency to form segmented chips is particularly challenging to model.
The contact length is one of the most important factors to evaluate the chip formation process and the mechanical loads in metal cutting. Over the years, several methods to identify the contact length were developed. However, especially for wet cutting processes the determination of the contact length is still challenging. In this paper, three methods to identify the contact length for dry and wet processes in cutting of Ti6Al4V and AISI4140 + QT are presented, discussed and analyzed. The first approach uses tools with a microtextured rake face. By evaluating the microstructures on the chip, a new method to identify the contact length is established. The second approach applies high speed recordings to identify the contact length. The challenge is thereby the application of high-speed recordings under wet conditions. In the third approach, tools with restricted contact length are used. It is shown that with all three methods the contact length is reduced using metal working fluid.
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