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CIRP Journal of Manufacturing Science and Technology
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Item-typ:Veröffentlichung, Analysis of internal material loads and Process Signature Components in deep rollingThe high mechanical loads in deep rolling lead to a beneficial surface topography, hardness alterations, and compressive residual stresses. The generation of defined residual stress values has been achieved in a mainly iterative way, as the relevant internal material loads occurring during the process could not be considered. They are difficult to determine experimentally and well-validated models are required to deduce them e.g. from finite element (FE) simulations. In this study, a 3D FE model has been developed to analyze the strains in the workpiece material as a measure for the internal material load during the process. The residual stress profiles were measured by x-ray-diffraction and are presented in a way that allows for deriving the internal material loads required to induce a desired residual stress state.Wissenschaftlicher ArtikelBand:35255 155 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, In-process measurement of Barkhausen noise and resulting productivity increase potential in grinding of case hardened steelThe micromagnetic Barkhausen Noise (BN) measurements bear the capability of providing non-destructively information about the condition of the surface integrity of ground workpieces. No unambiguous statements about the surface and subsurface area state can be made by evaluating single measured micromagnetic values if a superposition of different effects in the microstructure as a consequence of high thermomechanical loads occur. Especially for highly stressed components in automotive industry or in wind energy systems, case hardenend steels are deployed. These steels are often finished at the end of their process chain by a grinding process. At this point, the workpieces to be ground have already achieved enormous created added value. For productivity reasons, grinding should be carried out close to the process limit. To avoid undesirable phase transformations in the microstructure, process models such as the process model from Malkin can be used. If a grinding process consists of several process steps it must be ensured that the final process step leads to the intended surface and subsurface properties. In order to make the process design as productive as possible, an in-process measurement signal which correlates to the current state of the surface and subsurface area can help to achieve this result. Ideally this signal is applicable to generate an adaptive grinding process. Such a signal is investigated in this paper by application of BN as an in-process measurement technology. The paper shows the reliability of BN measurements as well as that there are different maximum BN amplitudes for different material removal rates. It is expected that these BN values correlate particularly to the residual stresses in the surface and subsurface area since Malkin's grinding burning limit was used to exclude (strong) phase transformations. Considering a micromagnetic parameter measured in-process a reduction of process time of 37% and thus a significant process improvement was achieved.Wissenschaftlicher ArtikelBand:3293 111 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Influence of gear hobbing feed marks on the resulting gear quality after discontinuous profile grindingGear hobbing is one of the most common soft-machining processes for pre-toothing. The process kinematics result in a characteristic tooth-flank topography, which is mainly determined by so-called feed marks. For an economical finishing process by gear grinding in automotive applications, the feed-mark depths should not exceed a maximum value of 35 mm. In the present study the validity of this limit has been investigated in view of the development of increasingly powerful grinding machines and grinding wheels. For this purpose, gears with feed-mark depths dx below and above 35 mm were machined and ground by means of discontinuous profile gear grinding afterwards. The influence of the feed marks on the grinding process with roughing parameters was systematically evaluated on the basis of various process variables such as the increase in spindle power Ps or the degree of grinding-wheel clogging Zs, while the resulting gear quality was mainly analyzed by various parameters to describe macro- and micro-geometry deviations of the ground tooth flanks. With increasing feed-mark depth, an increase in spindle power was found due to the additional machined volume. An influence of increasing feed-mark depths on the clogging degree, the grinding-wheel wear and the gear quality could not be proven. Therefore, economical finishing of gears by gear grinding is also possible with feed-mark depths of more than 35 mm. A new definition of this limit should be sought.Wissenschaftlicher ArtikelBand:31119 126 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Influence of the workpiece material on the cutting performance in low frequency vibration assisted drillingFundamental problems in drilling processes are associated with the unfavorable machining conditions in the tool center and the difficult chip removal. Low frequency vibration assisted drilling (LFVAD), in which the linear tool feed is superimposed with a vibratory motion in feed direction, is a promising process to overcome these problems. Aiming at a systematic analysis of the influence of workpiece material properties, results from LFVAD experiments with Ti6Al4V, AlMgSi0.5 and 42CrMo4 in different heat treatment states are presented. Specifically the dependence of optimal oscillation amplitudes on the workpiece material behavior is analyzed.Wissenschaftlicher ArtikelBand:3199 87 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Grinding burn limits: Generation of surface layer modification charts for discontinuous profile grinding with analogy trialsBy means of surface layer modification charts, the occurrence of thermal impact and thus the risk of grinding burn can be detected. With the present work it was shown that surface layer modification charts for discontinuous profile grinding can be generated using analogy trials carried out on a surface grinding machine for investigation of different grinding conditions and varied tilt angles in profile grinding. The experimental and the analysis effort for the analogy trials prove to be significantly more time and cost saving. The results also suggest that system parameters such as the grinding wheel specification or the cooling strategy are taken into account by the specific grinding power. Thus, the experimental results of this work allow the assumption that the determined process limit is not or just to a low extent depending on the system parameters. This assumption is supported by the thermal process limit determined by Malkin and converted in surface layer modification charts. Malkin's limit, identified for different ground steels with surface and cylindrical grinding processes and thus different system and process parameters, corresponds to the results generated in this work at workpieces ground with a kinematically more complex process. The results reveal that there is at least a group of steel materials which seems to share a similar thermal process limit.Wissenschaftlicher ArtikelBand:31731 98 - Some of the metrics are blocked by yourconsent settings
Item-typ:Veröffentlichung, Development and application of a test rig for tribological investigations under impact loadsThe investigation and the understanding of frictional mechanisms occurring between forming dies and work pieces in tribological contact is the prerequisite for the development of novel, dry bulk metal forming processes such as dry rotary swaging. The capability to conduct tribological investigations within the actual forming processes, however, is strongly limited, e.g. due to the limited accessibility of force measurement equipment. This work presents the development and application of a tribological test rig mimicking typical contact geometries and high impact loads associated with infeed rotary swaging for process-independent tribological investigations. The development comprises the designing process based on rotary swaging process simulations, setup assembly, and calibration procedure. Subsequently, the functionality of the test rig was demonstrated successfully, determining the distinct frictional properties under lubricated and dry conditions of various samples with structured surfaces representative for rotary swaging dies.Wissenschaftlicher ArtikelBand:19118 89