Experimental and numerical analysis of transient behavior during grind-hardening of AISI 52100

The grind-hardening process is an innovative approach to substitute conventional heat treatment processes. Due to the complex physical interrelationships and the lack of understanding regarding the process behavior and layout, extensive test series are required to assure reproducible hardening results. Therefore, methods for modeling and simulation are developed and used to analyze the thermo-metallurgical and thermo-mechanical effects during grind-hardening considering aspects like characteristics of process forces and tool wear. The objective of this paper is to predict the hardening depth distribution depending on the grinding path during grind-hardening in surface grinding by using finite-element-based simulations. Input data for the simulation are grinding forces, which are calculated by using regression analysis with respect to process parameters, e.g. specific removal rate $Q^{\prime}_w$ and equivalent grinding wheel diameter d _eq . The results of the simulation and the force model are validated by means of experiments. The consideration of the transient process behavior during grind-hardening within the developed models and simulations leads to an increase of process understanding and to new approaches regarding the efficient layout of the grind-hardening process.     

Modelling and simulation of process: machine interaction in grinding

This article presents an overview of current simulation methods describing the interaction of grinding process and grinding machine structure, e.g., vibrations, deflections, or thermal deformations. Innovative process models which describe the effects of the grinding wheel–workpiece interaction inside the contact zone are shown in detail. Furthermore, simulation models representing the static and dynamic behaviour of a grinding machine and its components are discussed. Machine tool components with a high influence on the process results are modelled more detailed than those with low influence. The key issue of the paper is the coupling of process and machine tool models for predicting the interactions of process and machine. Several coupling methods are introduced and the improvements of the simulation results are documented. On the basis of the presented simulation approaches, grinding processes and machines can be designed more effectively resulting in higher workpiece quality and process stability.     

Simulation of grinding processes using finite element analysis and geometric simulation of individual grains

The wear-resistance of sheet metal forming tools can be increased by thermally sprayed coatings. However, without further treatment, the high roughness of the coatings leads to poor qualities of the deep drawn sheet surfaces. In order to increase the surface quality of deep drawing tools, grinding on machining centers is a suitable solution. Due to the varying engagement situations of the grinding tools on free-formed surfaces, the process forces vary as well, resulting in inaccuracies of the ground surface shape. The grinding process can be optimized by means of a simulative prediction of the occurring forces. In this paper, a geometric-kinematic simulation coupled with a finite element analysis is presented. Considering the influence of individual grains, an additional approximation to the resulting topography of the ground surface is possible. By using constructive solid geometry and dexel modeling techniques, multiple grains can be simulated with the geometric-kinematic approach simultaneously. The process forces are predicted with the finite element method based on an elasto-plastic material model. Single grain engagement experiments were conducted to validate the simulation results.     

Chatter Stability of Metal Cutting and Grinding

This paper reviews fundamental modeling of chatter vibrations in metal cutting and grinding processes. The avoidance of chatter vibrations in industry is also presented. The fundamentals of orthogonal chatter stability law and lobes are reviewed for single point machining operations where the process is one dimensional and time invariant. The application of orthogonal stability to turning and boring operations is presented while discussing the process nonlinearities that make the solution difficult in frequency domain. Modeling of drilling vibrations is discussed. The dynamic modeling and chatter stability of milling is presented. Various stability models are compared against experimentally validated time domain simulation model results. The dynamic time domain model of transverse and plunge grinding operations is presented with experimental results. Off-line and real-time chatter suppression techniques are summarized along with their practical applications and limitations in industry. The paper presents a series of research topics, which have yet to be studied for effective use of chatter prediction and suppression techniques in industry.     

Influence of different grinding wheel and dressing roller specifications on grinding wheel wear

A targeted adjustment of the dressing results and the methodological influence of the dressing process on the non-stationary wear of a grinding wheel after dressing increases the productivity and the reproducibility of grinding processes. Despite the great economic importance of grinding processes with vitrified corundum grinding wheels and the great relevance of the dressing process for the application behavior of these grinding wheels, quantitative models are missing for the purposeful design of the dressing process. In previous studies, a dressing model was successfully developed which predicts the dressing force in the dressing process as well as the workpiece roughness and the grinding wheel wear behavior in a grinding process for a specific grinding wheel and form roller specification. However, a transferability of this model to other grinding wheel and form roller specifications is not possible because the influence of the grain size and the hardness of the grinding wheel as well as the dressing tool topography on the grinding wheel wear and thus on parameters of the dressing model are not known. The objective of this work was to extend the model to additional grinding wheel and form roller specifications to ensure a broad applicability of the model.     

磨削加工仿真预报系统的研究现状及发展趋势

磨削加工作为大部分产品成形前的最后一道工序,直接影响产品的加工精度和表面质量。磨削加工的多参数输入、输出和磨削过程中输入、输出参数之间的非线性映射决定了计算机仿真技术在磨削加工中应用的重要性。概述了计算机仿真技术相关理论,基于国内外磨削加工及预报模型,包括磨削运动学、磨削力、磨削温度、磨削液等模型的研究现状,对国内外将计算机仿真技术与磨削加工预报模型理论相结合的磨削加工仿真预报系统的研究现状进行了阐述。着重叙述了国内学者在磨削加工仿真预报系统软件开发方面的研究工作,最后展望磨削加工仿真预报系统的研究发展趋势。     

Numerical modelling of ground surface topography: effect of traverse and helical superabrasive grinding with touch dressing

Grinding processes are often used for final finishing of components because of their ability to satisfy stringent requirements of surface roughness and dimensional tolerance. Surface topography generated during grinding depends upon many parameters like wheel parameters, wheel velocity, downfeed, grit density etc. and it also depends upon the type of grinding procedures (viz. plunge grinding, traverse grinding, helical grinding, touch dressing etc.) employed. Therefore, a correct examination of the parameters and type of process employed to carry out grinding are necessary. This paper is an attempt to develop the relation between the different grinding parameters and the grinding procedures like plunge, traverse and helical superabrasive grinding with touch dressing and the average surface roughness. For this purpose, a numerical simulation technique has been implemented to generate the grinding wheel topography. The ground workpiece surface has also been generated by simulating removal of work material depending upon the trajectory of the abrasive grits on the grinding wheel without taking rubbing and ploughing into consideration.     

Influence of surface topography evolution of grinding wheel on the optimal material removal rate in grinding process of cemented carbide

Most of the reported studies on the optimization of grinding parameters do not consider the evolution of the surface topography of grinding wheels, and the established empirical models will no longer apply when the surface conditions of the grinding wheel changes. In this paper, an integrated model based on the surface topography of grinding wheel is established. The grinding process of cemented carbide is simulated using the established model, and the simulation results are analyzed to obtain the surface roughness model and the specific grinding energy model based on the undeformed chip thickness distribution. Subsequently, the grinding constraint models are defined according to the two grinding constraints—surface roughness and specific grinding energy. Through inversion analysis, the maximum material removal rate of the given grinding wheel surface conditions satisfying the defined grinding constraints are obtained, and the influence rules of the grinding wheel surface conditions on the maximum material removal rate are analyzed. Then the grinding wheel surface conditions are adjusted by changing the radial dressed height of the grinding wheel and the arrangement distance of the grains in wheel circumferential direction to improve the maximum material removal rate of the grinding wheel. Finally, the optimization results are verified through grinding tests of cemented carbide.     

不同体积分数SiCp/Al复合材料单颗磨粒划切仿真与试验研究

SiCp/Al复合材料由性能差异巨大的碳化硅颗粒与铝合金基体组成,切削过程复杂,影响加工质量因素多,材料仿真建模困难。本文提出了虑及颗粒随机分布特性、形状、粒径、体积分数等因素的SiCp/Al复合材料参数化建模方法,研究了不同体积分数SiCp/Al复合材料的去除过程、切削力、表面形貌及损伤等,并进行了试验验证。仿真分析与试验结果表明,参数化建模效果较好。SiCp/Al复合材料具有表面损伤严重、切削力大、基体涂覆掩盖表面缺陷、实际切削深度小等特点,不能单纯以表面粗糙度评价SiCp/Al复合材料的加工质量。粒径大、体积分数高的SiCp/Al切削力、比磨削能更低,表面质量更差,实际切削深度更小,铝合金涂覆现象更严重且覆盖层易脱落。SiC粒径对表面损伤、切削力、比磨削能有重要影响。本文可为SiCp/Al复合材料表面去除特点研究与工程应用提供一定的借鉴。     

外圆磨削加工的仿真、优化及控制

磨削技术已广泛应用于最后加工有光滑表面和高精度要求的零件,在过去的30年里,经过广泛的研究,对磨削加工的许多方面有了一个较为清楚的了解。本论文的目的在于说明怎样利用我们对磨削过程的理解来预报磨削特性和获得最佳加工条件。一个集成了描述磨削过程中不同方面的分析模块的软件包已被开发出来。这软件包括三个主要模块：仿真,校准和优化,仿真模块作为一个虚拟磨床来预测磨削过程和零件质量,校准模块通过实测参数如功率,表面粗糙度和椭圆度等对模型的系数进行修正,从而对实际磨削特性进行学习,优化模块是以最小化周期时间或以基于服从工件质量约束校正模型后的周期时间为目标来确定磨削和修整参数。本软件已被集成进了PC开放体系控制器（OAC）,作为智能磨削系统（IGS）的基础。     

An efficient method for solving the Signorini problem in the simulation of free-form surfaces produced by belt grinding

Industrial robots are recently introduced to the belt grinding of free-form surfaces to obtain high productive efficiency and constant surface quality. The simulation of belt grinding process can facilitate planning grinding paths and writing robotic programs before manufacturing. In simulation, it is crucial to get the force distribution in the contact area between the workpiece and the elastic contact wheel because the uneven distributed local forces are the main reason to the unequal local removals on the grated surface. The traditional way is to simplify this contact problem as a Signorini contact problem and use the finite element method (FEM) to calculate the force distribution. However, the FEM model is too computationally expensive to meet the real-time requirement. A new model based on support vector regression (SVR) technique is developed in this paper to calculate the force distribution instead of the FEM model. The new model approximates the FEM model with an error smaller than 5%, but executes much faster (1 s vs 15 min by FEM). With this new model, the real-time simulation and even the on-line robot control of grinding processes can be further conducted.     

Comparison of numerically and analytically predicted contact temperatures in shallow and deep dry grinding with infrared measurements

Contact zone thermal models of the grinding process are an important tool for the proper selection of process parameters to minimize workpiece damage while improving process efficiency. Validating contact zone thermal models with experimental measurements is difficult due to the high-speed and stochastic nature of the grinding process. In this work an infrared imaging system is used to validate two numerical thermal models, which are then compared to an established analytical contact zone thermal model. The two numerical thermal models consist of a shallow grinding model and a deep grinding model, where the deep grinding model takes the contact angle into account while the shallow grinding model does not. The results show that at small depths of cut both the numerical models and the analytical model perform well; however, as the depth of cut is increased the numerical models’ accuracy increases as compared to the analytical model. The increase in accuracy may be a result of the 2D solution of the numerical models as compared to the 1D solution of the analytical model. Additionally, it was found that the contact angle has very little effect on the contact temperatures. This work also reinforces Rowe's analytical work, using experimental and numerical results, which indicated that the workpiece temperatures are reduced by grinding at higher Peclet numbers for a given material removal rate.     

Advances in centerless grinding technology

This paper reviews the history of centerless grinding and its contribution to industry. It summarizes the evolution of centerless grinding theory including advanced modeling and simulation. Then, it discusses the design of main elements of a centerless grinding machine such as spindles, bed, guideways and positioning system, and provides design guidelines for future machines. The paper presents the state-of-the-art centerless grinding technologies: advanced machines, advanced process monitoring and the latest developments in grinding wheels. Finally, in conclusion, future trends and research work in centerless grinding technology are discussed.     

Research advances and steps towards the control of geometric deviations in the surface grinding of big components

Achieving and maintaining geometrical accuracy is nowadays the main limiting factor to accomplish an efficient manufacturing process in the surface grinding of big components. The present paper shows a deep research work carried out by means of experimental measurements of shape deviations, infrared pictures of the temperature field distributions and corresponding FEM simulations that confirm the thermal origin as one of the main limiting factors. A deeper investigation about the influence of the environment and cooling conditions, constraints imposed by part clamping and the grinding conditions reveals that the compensation and even control of thermal effects is possible by combining IR monitoring, modeling and simulation, although still being a challenging methodology.     

Fine grinding of silicon wafers: designed experiments

Silicon wafers are the most widely used substrates for semiconductors. The falling price of silicon wafers has created tremendous pressure to develop cost-effective processes to manufacture silicon wafers. Fine grinding possesses great potential to reduce the overall cost for manufacturing silicon wafers. The uniqueness and the special requirements of fine grinding have been discussed in a paper published earlier in this journal. As a follow-up, this paper presents the results of a designed experimental investigation into fine grinding of silicon wafers. In this investigation, a three-variable two-level full factorial design is employed to reveal the main effects as well as the interaction effects of three process parameters (wheel rotational speed, chuck rotational speed and feed-rate). The process outputs studied include grinding force, spindle motor current, cycle time, surface roughness and grinding marks.     

Grinding of Gears with Vitreous Bonded CBN-Worms

Among the industrial gear grinding processes, continuous generating grinding allows the highest material removal rates due to its kinematics. The process capabilities can be further increased by using CBN as a more efficient abrasive material. The research work described in this paper proves the high potential of vitreous bonded CBN grinding worms. Compared to corundum worms, the CBN tools offer significantly better behavior with regard to process stability, gear quality and residual stress on the machined gear tooth flanks. The results also show that a well adapted dressing technology is not only an important prerequisite for the efficient application of CBN worms but it also offers excellent and further possibilities to increase the grinding process performance. Dressable CBN grinding worms have not yet been introduced to industrial gear grinding processes. The paper gives an insight into the preparation and application of these innovative tools not only for academia but also for industry.     

Advances in multi-scale modeling of solidification and casting processes

The development of the aviation, energy and automobile industries requires an advanced integrated product/process R&D systems which could optimize the product and the process design as well. Integrated computational materials engineering (ICME) is a promising approach to fulfill this requirement and make the product and process development efficient, economic, and environmentally friendly. Advances in multi-scale modeling of solidification and casting processes, including mathematical models as well as engineering applications are presented in the paper. Dendrite morphology of magnesium and aluminum alloy of solidification process by using phase field and cellular automaton methods, mathematical models of segregation of large steel ingot, and microstructure models of unidirectionally solidified turbine blade casting are studied and discussed. In addition, some engineering case studies, including microstructure simulation of aluminum casting for automobile industry, segregation of large steel ingot for energy industry, and microstructure simulation of unidirectionally solidified turbine blade castings for aviation industry are discussed.     

Analysis and simulation of the grinding process. Part I: Generation of the grinding wheel surface

This paper is in three parts describing the analysis and simulation of the grinding process. This first part is concerned with the generation of the wheel surface by single point diamond dressing. In grinding, the grinding wheel has to be dressed periodically to restore wheel form and cutting efficiency. Understanding the process of generating the grinding wheel surface is important for the control of the grinding process. Generation of the wheel surface is simulated as a single diamond dressing process on a computer generated wheel. The wheel is simulated by grains randomly spaced in the wheel volume. The topography of the wheel cutting surface is generated by simulating the action of an ideal dressing tool as it dresses the wheel. The simulation of the wheel topography takes account of the motion of the dressing tool, grain size, grain spacing, grain fracture and grain break-out. The simulated cutting surface is used for further simulations of grinding. The simulation of grinding using the simulated grinding wheel surface is described in Sections 2 and 3 where a comparison is made of results predicted from simulation with results obtained from experiments. By matching simulated and experimental results, it is possible to explain the relative importance of dressing and grinding parameters.     

Effects of process parameters on workpiece roundness in tangential-feed centerless grinding using a surface grinder

The present authors proposed a new centerless grinding method using a surface grinder in their previous study [Wu, Y., Kondo, T., Kato, M., 2005. A new centerless grinding technique using a surface grinder. J. Mater. Process. Technol. 162–163, 709–717]. In this method, a compact centerless grinding unit composed mainly of an ultrasonic elliptic-vibration shoe is installed onto the worktable of a multipurpose surface grinder to perform tangential-feed centerless grinding operations. However, for the complete establishment of the new method it is crucial to clarify the workpiece rounding process and the effects of process parameters such as the worktable feed rate, the stock removal and the workpiece rotational speed on the machining accuracy, i.e., workpiece roundness, so that the optimum grinding conditions can be determined. In this paper, the effects of the process parameters on workpiece roundness are investigated by simulation and experiments. For the simulation analysis, a grinding model taking into account the elastic deformation of the machine is created. Then, a practical way to determine the machining-elasticity parameter is developed. Further, simulation analysis is carried out to predict the variation of workpiece roundness during grinding and to discover how the process parameters affect the roundness. Finally, actual grinding operations are performed by installing the previously constructed unit onto a CNC surface grinder to confirm the simulation results. The obtained results indicate that: (1) a slower worktable feed rate and higher workpiece rotational speed give better roundness; (2) better roundness can be also obtained when the stock removal is set at a larger value; (3) the workpiece roundness was improved from an initial value of 23.9 μm to a final value of 0.84 μm after grinding.     

砂轮表面形貌检测方法的研究进展

砂轮表面形貌特征是砂轮磨削性能的主要决定因素。准确地检测砂轮表面形貌不仅有助于进一步认识磨削机理,更是砂轮表面形貌建模和磨削仿真不可或缺的先决条件。本文中总结了典型的砂轮表面形貌检测方法,概述了各检测方法的基本原理,并分析了它们的优势和不足。最后,分析了国内外砂轮表面形貌检测方法的发展现状,指出了现阶段存在的问题,展望了砂轮表面形貌检测方法的发展前景。