Applied Mechanics and Materials Vol. 794

Abstract: One research objective for generating gear grinding is to increase economic efficiency and productivity of the process. At the same time gear quality must be equal or higher. In addition to machining parameters, tool specification has a significant influence on process productivity, workpiece quality and the wear of the tool itself. Due to the variety of tool specifications process users have the problem of selecting the best fitting tool for their demands. Therefore, it is necessary to know how interactions of tool specification and machining parameters influence tool wear and workpiece quality. But basic experimental studies, which take different tool specifications into account, are missing today.This paper focuses on the influence of different tool specifications and machining parameters on the tool wear for generating gear grinding. With analogy trials the influence of different specifications and machining parameters on tool wear and the process is mapped. The results are analyzed, discussed and summarized in a model. Furthermore, the applicability of the findings based on analogy trials to generating gear grinding is validated.

Abstract: In order to obtain a better understanding of the effects of an internal broaching operation on the resulting component geometry, investigations were carried out. The investigations were carried out on sliding sleeves made of case hardening steel SAE 5115 (German grade 16MnCrS5). The cutting speed was varied. The results indicate that the arrangement of teeth on the scope of the tool has a significant influence on the resulting component geometry. Furthermore the results show that also the cutting speed has a significant influence on the resulting component geometry, in particular due to the resulting process temperatures.

Abstract: The internal combustion engine of the future has to cope with increasing high requirements. A large potential is seen in reducing friction in the piston group. For this purpose a coating technology for cylinder running surfaces, including mechanical machining processes was developed. By substituting the compact cast iron liners (4 mm wall thickness) for the thin coating layer (0.1 mm) the normal forces become more important in the honing process. Due to the different stiffness of the crankcase roundness deviations occur caused by the machining forces as a result of elastic deformation. Content of this paper is the calculation of the elastic deformations using the finite element method. Based on a honing tool model, the effective normal forces are calculated, which afterwards are used as input variables for the crankcase model.

Abstract: Chemical cleaning methods are under strict restrictions due to the legislator, as they are often harmful to environment and health. Therefore, environmentally neutral cleaning methods will gain importance in the future. Alternative cleaning processes like blasting with solid carbon dioxide can substitute such harmful chemicals without residues of blasting media. CO₂ snow blasting has a minor technical complexity with a possible high degree of automation, but is limited in its cleaning performance. Basic knowledge of CO₂ formation must be gained in order to increase the cleaning performance. The basic dependencies of ambient pressure and temperature as well as the possibility of their manipulation regarding the produced CO₂ particles were investigated. The investigations were conducted using design of experiments and lead to a model describing the CO₂ snow formation and its properties. The goal was to manipulate the properties of the generated CO₂ snow in order to optimise the technology regarding the cleaning task.

Abstract: Laser-chemical micro structuring offers a possibility to process particular metals nearly without any mechanical or thermal stress. The required electrolyte depends on the respective chemical composition of the specific metal. The presented results demonstrate the possibilities for laser-chemical machining of titanium, Stellite 21 and tool steel X110CrMoV82 for use in medical applications and micro tool manufacturing with respect to the engineering requirements. Furthermore, first results are shown depending on the identification of more environmentally friendly electrolytes to meet the everincreasing environmental and industrial standards.

Abstract: Brittle materials like ceramics or glass can be machined by cutting with negative rake angles and by abrasive machining processes. Especially grinding allows for low surface roughness and high shape accuracy. Conventional path-controlled grinding processes may damage functional surfaces if brittle fracture occurs and may thus lead to lateral, radial and axial cracks. High grinding forces can be a reason for brittle fracture when grinding ceramic materials. A solution for this effect may be the application of force controlled grinding processes. In this paper adapted control algorithms were implemented for force controlled grinding and verified in grinding experiments. As an example, cylindrical grooves were ground with an injection moulded spherical grinding tool in alumina and zirconia ceramics. After grinding surface roughness, shape accuracy and process forces are analysed and discussed.

Abstract: For manufacturing of micro holes ElectricalDischarge Machining (EDM) can be used, which is well-established due toits thermal working principle that allows almost force free machining independent of the material’s mechanical properties. The importance of this production technology is increasing, especially for the machining of ceramic materials, which are required in many applications within the field of microtechnology. However, the production of precise micro holes with complex geometries and high aspect ratios is associated with a many challenges. Hightool electrode wear, low material removal rate and small gap widths are observed in the process. This paper presents an optimized dry EDM technology for the manufacturing of micro holes in Si₃N₄-TiNceramic. The experiments were carried out with different energy influencing process parameters for the spark discharge and flushing pressure, which were systematically evaluated by methods of statistical Design of Experiments. Subsequently dry EDM and conventional EDM micro drilling processes were compared and the differences between both processes were evaluated. The influences of liquid and gaseous dielectric are analyzed in terms of process stability and axis movements.

Abstract: Many machining operations e.g. turning, milling or grinding are dependent on the application of water-based metalworking fluids (MWF) which contribute significantly to their high level of performance. MWF in-use are exposed to a microbial contamination, which leads to a deterioration of water-based MWF components and can cause a premature failure of the whole coolant system. Expensive monitoring and the addition of biocides are needed to maintain the MWF quality and to reduce the microbial load, regardless of the potential risk for health and environment. To overcome these limitations, the paradigm shift of using microorganisms as a replacement for conventional MWF is investigated in this paper. Microbial cell components and some microbial inclusions are comparable to conventional MWF components like e.g. fatty acids or sulfur compounds. Due to this fact, it is possible to create a regenerative system on a microbiological basis for the substitution of conventional MWF components. In preliminary tribological investigations the basic lubrication properties of microorganisms and their potential as a replacement for conventional MWF were shown. The presented approach intends to investigate the influence of microbial cell counts, cells size and extracellular polymeric substances (EPS) on the lubrication behavior respectively. The results of the tribological tests show that especially microorganisms with a big cell volume or a high EPS productivity exhibit superior Brugger-values (up to 174%) compared to a highly concentrated conventional MWF (emulsion 10%) and indicate the great potential of microorganisms as a replacement for conventional MWF.

Abstract: Roller clinching is a mechanical joining method, which combines conventional clinching with rotational tool movement. For that purpose, punches and dies are mounted on contrariwise rotating rolls, while the sheets are continuously fed forward. The rotation affects the joint formation and therefore the mechanical joint properties. In this paper, the ratio between the rolling radii of punch and die is varied. Shear tests are conducted for the material combination steel and aluminium with different sheet thicknesses. Because of the asymmetry of the resulting clinchpoints, the joint strengths are examined in different load directions. The joint formation is analysed using cross sections and the effects of different punch geometries are discussed. Finite element simulations are used to gain deeper process insight.

Abstract: Lightweight design and modern production technologies are key factors for the success of today’s car manufacturing industry. Resulting challenges, like the usage of new materials in the production chain and the joining of dissimilar material combinations for composite constructions, require the constant improvement and innovative development of production and joining processes. One promising joining technology which allows single stage joining of modern hot formed steels is shear-clinching. For ensuring process reliability and improving strength of shear-clinching joints fundamental studies are required. A possible approach is the numerical analysis of the material flow. To guarantee high quality simulation results it is important to develop a possibility to simulate the material separation during the shear-clinching process. This paper presents an evaluation of possible methods to simulate the indirectly induced cutting of the die-sided material. The numerically gained results are validated by experimental data.