Fraunhofer Institute for Mechanics of Materials IWM
Fraunhofer Institute for Mechanics of Materials IWM

Cutting, Grinding, Wear

Energy-efficient and low-wear cutting, grinding and conveying

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Machining by chip removal

The optimization of machining processes with geometrically defined cutting edges is challenging. Are the cutting speed or the infeed more important? Or does the geometry play the decisive role? What effect does the coating of the cutting tool have? Can the heat generated not be dissipated quickly enough because the coolant is not flowing to the right places? Should the workpiece be preheated to improve its machinability? The simulation clarifies this.

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Optimized grinding processes

Grinding is energy-intensive and therefore has the potential to save costs. But how does the grinding energy requirement depend on the porosity of the bulk material to be ground? How do the particle size and shape of the materials influence the grinding process? What types of wear occur on the grinding tools and how can wear be minimized? We use simulations to find the optimum solution for your process. 

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Reduce erosive wear

Erosion causes economic damage. How does the hardness of the materials influence erosive wear? How does the wear depend on the shape and size of the impinging particles? What role does the surface finish play in erosive wear? How can materials and processes be optimized to minimize erosive wear? We have the right models to answer these questions. 

Examples of projects

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During the machining simulation, the tool removes a chip from the component. The color coding corresponds to the degree of damage in the material.

Increasing tool life during machining



The adjacent illustration shows a section of a cutting simulation. The cutting tool moves from right to left, lifting a chip from the workpiece. The workpiece consists of an aluminum alloy whose deformation is described with a plasticity model. The color coding in the workpiece indicates the degree of local material damage. By varying the rake angle and clearance angle as well as the cutting speed, cutting depth and feed rate of the cutting tool, both the chip formation and the surface quality of the workpiece as well as the tool life are influenced. A material-specific damage model is used to investigate these influencing variables and optimize them for specific applications. Fraunhofer IWM models make it possible to take all relevant phenomena into account: Plastic deformation and removal on the workpiece, flow dynamics of the cooling lubricant and wear in the cutting tool. The interaction between these mechanisms is also captured in the simulation. Information can be extracted from the simulations in order to reduce tool wear and thus increase cutting tool life. Do you want to test a new material for your cutting tool? We can test this using simulation. 

  • Mohseni-Mofidi, S.; Bierwisch C., Application of hourglass control to Eulerian smoothed particle hydrodynamics, Computational Particle Mechanics 8/1 (2021) 51-67 Link

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Simulation of magnet-assisted pressure flow lapping. The dark blue particles are used to smooth the rough surface on the underside. The color coding shows the local velocity field of the carrier liquid from slow (blue) to fast (red). A magnetic field acts during the process, accelerating the particles towards the surface to be smoothed.

Optimize pressure flow lapping with the right magnetic field



Magnetic Assisted Abrasive Flow Machining (MAAFM) was investigated in the BMBF project SmartStream. This process involves using a magnetic field to cause particles to collide with the wall, thereby reducing wall roughness. In the project, the effect of an external magnetic field on the removal efficiency of the magnetizable abrasive grains was of particular interest. The aim was to gain insights into the mechanism of material removal on the microscale and to use the knowledge gained to optimize the process parameters. The simulation includes modeling the hydrodynamics of the carrier fluid, the flow dynamics of the grains, as well as the plastic surface deformation and material removal. To address the multifaceted physics of the problem, all phases, i.e. the fluid, the grains and the workpiece surface, were modeled using the Smoothed Particle Hydrodynamics (SPH) method in the SimPARTIX software at Fraunhofer IWM. Since SPH is a Lagrangian particle method, it can easily handle large deformations, e.g. fluid flows, moving interfaces and grains suspended in a fluid. In addition, SPH is able to track topological changes due to surface ablation and thus easily obtain fluid-structure interactions throughout the process. In order to investigate the effects of magnetism in the MAAFM process, the dipolar forces caused by an external field or by the stray fields of the surrounding grains are also included in the calculations. The results clearly show the influence of a magnetic field gradient on the performance of the MAAFM process. Compared to the results of the simulation without an external magnetic field, an adequately selected magnetic field gradient enables a doubling of the rate of surface removal. 

  • Mohseni-Mofidi S.; Pastewka L.; Teschner, M.; Bierwisch, C., Magnetic-assisted soft abrasive flow machining studied with smoothed particle hydrodynamics, Applied Mathematical Modelling 191 (2022) 38-54 Link

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Wear simulation during pneumatic conveying within a pipe or a 90° bend. The simulation shows where the greatest depth of erosion is to be expected (red color coding).

Minimization of erosive wear in pneumatic conveyors



Wear in pipe systems can lead to system failures. As part of the Industrial Collective research project "Development and testing of a model framework for the predictive clarification of erosive wear in pneumatic conveying systems" (Industrial Collective Research project number 20815 N), wear was therefore investigated jointly with the Department of Mechanical Process Engineering and Processing at the Technical University of Berlin by means of numerical and experimental investigations both on the microscopic length scale of individual particle impact events and on the macroscopic scale of pipe bends. A total of four steel grades - three stainless steels and one structural steel - as well as one plastic were experimentally investigated with regard to their wear resistance in contact with round and angular bulk material particles in different wear situations. This made it possible to assess the materials in terms of their wear resistance in different applications and to work out the significant influence of the shape of the bulk material particles. The relevance of the particle shape for erosive wear was confirmed by detailed numerical simulations using SPH. Based on the simulation results, an established analytical erosion model, which quantifies the wear per impact, was successfully extended by two parameters that characterize the particle shape. This has created a model that is suitable both for rapid estimates of the wear behavior of a particular bulk material and for direct integration into CFD-DEM simulations for process analysis.

  • Mohseni-Mofidi, S.; Drescher, E.; Kruggel-Emden, H.; Teschner, M.; Bierwisch, C., Particle-based numerical simulation study of solid particle erosion of ductile materials leading to an erosion model, including the particle shape effect, Materials 15/1 (2022) Art. 286, 22 Seiten Link

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Grinding simulation of granulated blast furnace slag with visualization of the sand before the start (top) and during the grinding process (bottom). The color coding corresponds to the speed of the sand grains.

Evaluation of the grindability of porous granulated blast furnace slag

 

Granulated blast furnace slag is a largely glassy, solidified blast furnace slag granulate that is obtained from the liquid slag after the blast furnace tapping process by breaking it up and quenching it with a high excess of pressurized water in granulation plants. Blast furnace slag is ground to cement fineness and has been used worldwide for decades in the production of cement and concrete. The energy required for the grinding process is extremely high and increases exponentially with the fineness. Every year, around 1.4 billion kWh or 38% of the German cement industry's electricity requirements are used to grind the various components of cement. In order to reduce the grinding energy requirement, a more precise knowledge and improvement of the comminution-relevant properties of granulated blast furnace slag is necessary. In the joint Industrial Collective Research project no. 20187 N, Fraunhofer IWM and the FEhS - Institut für Baustoff-Research e.V. investigated the influence of the porosity of granulated blast furnace slag on its comminution behavior. The specific grinding energy requirement was calculated as a function of the specific surface area for a modeled vertical roller mill. The result essentially shows a decreasing specific grinding energy requirement with increasing porosity for a given specific surface area. Thus, from a grinding point of view, a high grain porosity should be set wherever possible when granulating liquid blast furnace slag into granulated blast furnace slag.