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The aim of this paper is to improve surface and subsurface workpiece properties in steel grinding by using nearly spherical ceramic grains in an elastic bond system. To characterize and evaluate the potential of this rather new tool concept, the resulting workpiece microtopography and the subsurface characteristics are analysed and cover residual stresses, micrographic cross sections, and EBSD images. The results include the effect of the different process parameters on increased mechanical process loads resulting in favorable surface properties characterized by mechanically induced plastic deformation and compressive residual stresses. With regard to the metallographic analyses, an increased grain refinement was identified in micrographs and EBSD images, which results from the changed chip generation mechanisms. The sum of the above effects shows an increase in the residual compressive stresses introduced into the workpiece. This reveals the potential of spherical ceramic grains in an elastic bonding system. [ABSTRACT FROM AUTHOR]

The outcome of this paper allows calculating the fraction of heat generated in the primary shear zone that is transferred to the workpiece in face milling. The proposed approach is based on a sequentially coupled analysis of the heat partitioning in the cutting edge normal plane and in the reference plane. The latter, for the first time, allows to systematically take into account the removal of heated workpiece material by subsequent cutting tool engagements. The generated heat is related to the uncut chip thickness. Utilizing Weiner's approach, the heat flux density distribution is determined which serves as input for a three-dimensional thermal finite element simulation that is validated experimentally by temperature measurements. [ABSTRACT FROM AUTHOR]

The focus of this work is the analysis of the thermal impact and its depth effect in different grinding processes. The investigated processes cover different kinematics and thus broad ranges of the relative speeds and the intensities of the moving heat source regarding the ground surface. A uniform lower process limit characterizing the onset of grinding burn for the different kinematics is identified by means of the specific grinding power and the contact time. The experimental results together with the theoretical considerations of peak temperatures lead to the conclusion that the process specific range of the contact time is mainly responsible for the thermal depth effect. The results enable the targeted exceeding of the critical process limit in roughing and the subsequent correction by finishing. [ABSTRACT FROM AUTHOR]

This paper reviews the physical and chemical interactions between the rotating tool and the supplied fluid in grinding. The mechanisms of this tool-fluid interaction are the key for high performance grinding processes due to an efficient fluid supply resulting in a minimal thermomechanical impact on workpiece and tool. Reduced wear, increased surface finish, suitable subsurface properties of the machined material, increased material removal rates, and also energy efficiency can be achieved. In this context, the fluid supply towards the contact zone between tool and workpiece, the tool cleaning with high pressure cleaning nozzles as well as (tribo)-chemical phenomena between the abrasive layer and the supplied fluid are analysed and discussed. Finally, knowledge gaps are revealed which are indicating future research needs. [ABSTRACT FROM AUTHOR]

An approach is presented to evaluate the energy efficiency of grinding processes by the total specific energy in relation to the process limits, e.g. starting thermal damage at a certain specific removal rate. The paper deals with grinding experiments on hardened steel workpieces covering a broad range of different types of fluid supply nozzles, fluid flowrates, and removal rates with and without high pressure tool cleaning. In the investigations, process configurations were identified leading to high energy efficiency in combination with highest achievable removal rates. Furthermore, the results confirm that the process limit is significantly influenced by specifically adapted fluid supply conditions e.g. flowrate and jet speed. [ABSTRACT FROM AUTHOR]

We present an infrared sensor array integrated in a steel workpiece to measure the local temperature distribution during a grinding process. The sensor is mounted in the workpiece in a way that the field of vision is 1mm next to grinding surface. We measure with 64 pixels over a 16x4mm surface on the level of the grinding surface. During grinding temperature in the field of vision is recorded. Grinding was performed with different grinding parameters to analyze the temperature distribution in the steel. The measurements show relatively low temperatures within the chosen parameters. The chosen approach is used to characterize the thermal material load which is expected to correlate with material modifications for higher temperature at high removal rate. [ABSTRACT FROM AUTHOR]

The generation of desired surface layer properties by a certain manufacturing process requires a comprehensive knowledge of the physical loads during the process and their influences on the workpiece material. This paper presents the setup and results of two in-process measurement systems, which are specifically designed to locally determine temperature and strain in several processes (in this case: grinding and deep rolling). One measuring system is based on speckle interference effects (speckle photography) detecting the deformation distribution of the workpiece surface and the other applies resistance deviation measurements of integrated thin films inside the near-surface layer to determine temperature and strain variations. [ABSTRACT FROM AUTHOR]

The productivity of grinding processes is often limited by the risk of thermal damage of the workpiece surface layer. Therefore, the control of thermal conditions in the grinding arc is of utmost importance for both, industrial practice and academia. In order to optimize the application of the metal working fluid in grinding, devices and methodologies are needed which can assure the measurement of temperatures in grinding or within set-up mode and the control of demand-oriented fluid supply parameters (nozzle angle, nozzle height, nozzle outlet area, fluid jet velocity). The systematic use of such devices and methodologies for fluid supply optimization is enabling reliable and economic grinding processes. [ABSTRACT FROM AUTHOR]

Abstract: Besides high demands on surface integrity machining of gears aims on very low surface roughness and high shape accuracy. These properties will have positive impacts on the lifetime of gears. In this context the challenges of profile grinding of cylindrical gears by using elastic bonded grinding wheels are addressed. For this new gear fine finishing approach, the very high potential of the process is revealed by analyzing the influence of the grinding wheel specification and the machining parameters on surface finish. Results show that gears with high shape accuracy and very good surface finish with almost optical quality can be achieved. [Copyright &y& Elsevier]

Abstract: This paper is dealing with the identification of efficient cleaning nozzle configuration to prevent the wheel from loading in creep feed grinding. The properties of different cleaning nozzles types were analyzed in terms of jet velocity and jet impact on the wheel surface using high speed imaging and pressure sensitive sheets. In grinding experiments the cleaning efficiency of each nozzle configuration was evaluated by optical measurement of wheel clogging inside the machine tool. With this newly developed procedure of tool cleaning optimization a significant reduction of grinding forces (up to 30%) and of the tool wear (up to 20%) was achieved. [Copyright &y& Elsevier]

Besides conventional heat treatment operations, an innovative approach for surface hardening is the grind-hardening process. During this process the dissipated heat from grinding is used for a martensitic phase transformation in the subsurface region of machined components. Additionally, compressive residual stresses are induced in the grindhardened surface layer. However, for the implementation of grind-hardening into industrial production extensive experimental tests are required to achieve iterative results of hardening depth. This paper focuses on the identification of parameter sets for a sufficient grind-hardening in outer-diameter grinding. On the one hand, grinding tests were conducted supported by metallographic investigations; on the other hand, a finite-element-based model was used to predict the surface integrity resulting from grind-hardening. [ABSTRACT FROM AUTHOR]

Abstract: This paper presents with a new grinding strategy for a surface superfinishing and a grind-strengthening of the surface layer of steels in a single grinding step. To grind-strengthen a surface layer both abrasive material removal and a plastic deformation are needed. This combination together with an appropriate grinding wheel design offers the possibility to ensure high precision surfaces with a consistent quality finish that meets the highest standards. This kind of grinding process could be applied to bearings, for example. During the run-in period, the initial contact surfaces change until they stabilize to a running-in condition and have a new surface topography. Grinding with the new process strategy leads to benefits because a grind-strengthened surface layer eliminates initial wear and abrasion within the system, reduces surface finish roughness, extends fatigue strength, and reduces risk of part failure during operation. [Copyright &y& Elsevier]

Abstract: This paper focuses on the evaluation of topographical parameters characterizing the influence on the behaviour and finally the process results by applying engineered diamond wheels in machining hard and brittle materials. Here, coarse-grained, single-layered diamond grinding wheels with electroplated abrasive layers and active-brazed, defined grain pattern have been dressed by a special conditioning process and used in precision grinding experiments on optical glass. The characterization of the abrasive layer topography was done by two topographical parameters, the specific total grain plateau area A′G,total and the average grain cutting edge width b G,a, determined by 3D-profilometry of replicated abrasive layers after each dressing step. [Copyright &y& Elsevier]

Abstract: This paper shows the possibility of using the size effect of the specific grinding energy for a targeted surface layer work-hardening of metal parts. The research includes the combination of abrasive material removal and plastic deformation in a single grinding step. Therefore high specific energy values are needed and thermal effects counteracting the work-hardening have to be minimised. This can be achieved by low cutting speeds in combination with low depths of cut. The new approach results in an in-process work-hardening of the surface layer, which was found to lead to higher hardness, a compressive residual stress state, and higher wear resistance. [Copyright &y& Elsevier]

Abstract: The objective of this paper is the modeling of kinematics of precision contour grinding and resulting workpiece topography. Changes within the contact zone of grinding wheel and workpiece as well as speed ratios are analyzed and evaluated. The generated surface patterns caused by the runout of the grinding wheel are simulated. In the kinematic-geometrical model single grains on the peripheral surface of a grinding wheel, which interact with the workpiece, are considered. After describing the kinematics of the contour grinding process, changes in feed speeds and rotational speed ratios are examined and their effects on generated surfaces are simulated and compared with ground surfaces. [Copyright &y& Elsevier]