李响 外文文献翻译(OK).doc

山东建筑大学毕业设计外文文献及译文科毕业设计外文文献及译文文献、资料题目：Research on the Theory and Parametersof Bar Cutting Based on High Speed and Restrained State文献、资料来源：机械工程与力学国际会议文献、资料发表（出版）日期：2005.10.26院 （部）： 机电工程学院专 业： 机械工程及自动化班 级： 机械114姓 名： 李响学 号： 2011071225指导教师： 靳同红翻译日期： 2015.3.19外文文献：Research on the Theory and Parameters of Bar CuttingBased on High Speed and Restrained StateBar cutting process has a direct influence on the productivity and quality of products as well as the economic benefits in the field of manufacturing. Bar cutting theory and technology has been paid more and more attentions by scholars all over the world and has become a hot spot of research and exploration in the resent years. But up to now, there is still no effective bar cutting methodologies. Based on the high speed and restrained state, a kind of advanced bar cutting theory and technology is put forward and studied. The theory of fracture mechanics is utilized to analyze the cutting fracture process. The mechanism of high speed cutting and the characteristics of deformation are researched. Cutting parameters such as material temperature, cutting speed and die clearance are also analyzed. Theoretical analysis and experiments shows that better quality bar cutting can be obtained with this novel precision cutting technology.1. IntroductionBar cutting is the first and important procedure in the manufacturing process of products. The quality of bar cutting has a great influence on the productivity, the quality of products and the economic results. With the development of precise forming and precise processing, the demand for cutting quality of materials has become higher and higher. For the commonly used bar cutting method, because the cutting speed is low and there is no clipping apparatus, the quality of the cutting surface and the weight error can not meet the production demands. For a long period of time, scholars from different countries have done a lot of theoretical analysis and experimental research works on bar cutting technology and many achievements have been made. Because the cutting deformation process is a very complicated process and quality of the cutting surface is affected by many factors, up to now, there is still no effective theory and efficient cutting method can be used in production.The authors have been dedicated to the researches of precise cutting theory and methods for several years. By synthesizing and referring to available research results, a new kind of bar cutting method and precise cutting machine has been put forward for the first time. In this paper, a kind of advanced bar cutting theory and method based on high speed and restrained state is put forward and researched. Theory of fracture mechanics is applied on the analysis of cutting crack process, and high-speed cutting mechanism and deformation characteristics are also researched. By means of analysis of the cutting deformation and stress state in the cutting area, a proper loading method is proposed. The influence of every cutting factors or parameters such as cutting speed, cutting temperature, restrained state and dies clearance on the quality of the cutting surface is analyzed and optimized cutting parameters have been obtained. Principle of the high speed cutting machine is put forward. Bar cutting experiments in the high speed cutting machine has been carried out and the experiment results have also been analyzed.2 .Analysis of the bar cutting processThe precise cutting of bar materials based on high speed and restrained state is performed between the high speed moving cutting die and a fixed cutting die. When the moving cutting die driven by the slide moves down at a high speed and cuts the material the lower clipping die follows down and produces a clipping force F in the up direction, by which the materials can be clipped. At the same time the upper clipping die produces another clipping force FZ and the delivered materials can be clipped between the upper clipping die and the fixed cutting die, shown in Figure 1Figure 1 Cutting process and the deformation of materials1. Moving cutting die 2. Upper clipping die3. Delivered material 4. Fixed cutting die5. Lower clipping die 6. Cut materialAs shown in Figure 1, in the cutting process the bar material can be divided into three deformation areas, the violent deforming area I，the participating deforming area II and non-participating deforming area III .Among which the violent deforming area I is the most important. The stress state of the materials and the deforming process in this area has a direct influence on the quality of the cutting surface. In high speed cutting and restrained state, materials in area I is in a three-dimensional pressed stress state. After proper simplifying of the mechanical model, the stress state of materials in area I is shown in Figure 2.Figure 2 Stress state of material in cutting deforming area(a) The stress state of material in the moving cutting edge(b) The stress state of material in the fixed cutting edgeThe cutting process can be divided into three steps: elastic and plastic deforming, crackles producing and fracturing steps. Applying the fracture mechanics theory, the displacement field in the fracture of the materials can be expressed as follows: (1)(2) Where - Poisson ratio of material E -the shearing modulus of elasticity K -stress strength factor of II typed crackles A-the angle between cracking direction and the crack surface k- coefficients of calculation r-crackle tip radius in the plastic area For the precision cutting in high speed and restrained state, materials in the deforming area is in three-dimensional restrained states. The crackle tip radius in the plastic area can be expressed as2 (3)Where -the yield stress of material It can be shown in formula (3) that the radius of the plastic area in high speed and restrained state is 50% less than that in common cutting process. Therefore the crackle of the materials in high speed and restrained state cracks smoothly and better quality of the cracking surface can be obtained3 Cutting parameters The quality of cutting surface is affected by many factors such as cutting speed, materials temperature, the restrained state and clearance of dies. In order to get the best cutting parameters and design high speed cutting machine it is necessary to analyze these cutting factors and parameters.3.1 Cutting speed With the increase of the cutting speed, the plasticity and the cracking toughness will become lower. Thus the deformation of cutting surface will decrease and brittle cracking of the metals is easy to produce. The cutting surface is smooth and there are fewer burrs, and the quality of the cutting surface is much better. On the other hand, if the cutting speed is over high, with the increase of material temperatures caused by high speed, plasticity of the materials will increase and the quality of the cutting surface will be affected. According to the theory and calculating formulas proper range of the cutting speed can be obtained. Together with the experiment research in the high speed cutting machine and the analysis of the cutting quality, the better range of cutting speed for high-speed cutting is 5-10m/s3.2 Cutting temperatureCutting temperature is the temperature of material during cutting process. It is one of the most important cutting parameters affecting the cutting quality. According to the characteristic of materials and the theory of fracture mechanics, the temperature increases during high speed cutting process. The proper range of temperature should be in the range of brittle fracture temperature intervals. Through the experiments of high speed cutting in high speed cutting machine and analysis of the cutting surface, the unevenness relation curves of cutting surface with cutting temperature and cutting speed have been obtained for different materials. As for lower carbon steel, the proper range of cutting temperature is 350-380 C3.3 Restrained state Quality of the cutting surface is directly affected by the stress state during the cutting process. The stress state can be changed by the restrained state of materials. As for commonly used cutting technology, there are no restrained measures to materials and bending deformation of the cutting materials can be produced, which will result to worse quality of the cutting surface. In the condition of precise cutting with restrained state (as shown in Figure 1), because of the squeezed action, the materials are in a three-dimensional pressed stress state, and the quality of cutting surface is much better.3.4 Clearances of diesThe clearance of dies during cutting varies with different materials and different length-diameter ratios. There are some theoretical formulas and experiential formulas can be referred. According to the calculation of the cracking angle of cracking surface, the clearance of dies for different length-diameter ratios can be determined as follows:Where: k-coefficient related with length-diameter ratiok1- coefficient related material propertiesD-diameter of the materials As for the precise cutting in high speed and restrained state, the clearance of dies is less than that of the commonly used cutting methods. The more the clipping force the less the clearance is.4 Loading ways and analysis of the experiment resultIn order to realize the high speed cutting with restrained state, a new kind of high speed hydraulic-pneumatic bar cutting machine has been developed and manufactured. In this machine the power is generated from a hydraulic system. Before working, the compressed air or nitrogen is filled into the air cylinder. When the piston together with the slider and moving cutting die driven by pressed fluid from hydraulic system moves up, the compressed air in air cylinder will be further compressed. When the fluid in the lower cylinder is drained out, the slider and the moving cutting die accelerates down under the action of the compressed air and the weight. The velocity of the slider is expressed as follows: Where: We -the expansion work of the air m- the mass of moving system g- acceleration of gravity S-the stroke of moving system - mechanical efficiencyIn the cutting machine made by authors, the cutting speed is in the scope of 5-10m/s and is adjustable. When the moving cutting die cuts the materials, the lower clipping die produces a force in the up direction under the actions of springs and the materials are clipped. At the same time, the upper clipping dies produce another clipping force driven by the pressed fluid in the clipping cylinder and clips the materials. The working cylinder and the clipping cylinder are driven and controlled by the same hydraulic system.In this high-speed cutting machine, precise bar cutting experiments are performed under the condition of different speed and different temperature. According to the experiment results, the relation curves of unevenness of the cutting surface with different speeds and temperatures have been obtained. In order to observe the quality of the cutting surface, metallographic analysis of is performed with SEM. One of the comparisons of high speed cutting (5m/s) with common cutting method is shown in Figure 3.Figure 3 Metallographic analyses of high-speed cutting and common cuttingFigure 3 (a) is the test piece morphology of high speed cutting and b is the morphology of common cutting. It is obvious that there is no plastic deformation and tearing in the central area of high-speed cutting piece. The quality of the cutting surface of high speed cutting is much better than that of the commonly used cutting methods.5 Conclusions The quality of metal cutting has a direct influence on the quality, productivity and economic result of metal forming and mechanical manufacturing. Aiming at such problems as lower cutting quality, inefficient and waste of materials existed in commonly used cutting method, a new kind of precise cutting method and theory base on high speed and restrained state is put forward and researched by the authors for the first time. Through the analysis of the cutting process and the deformation of materials, the cutting mechanism and deformation characteristics for high speed and restrained state cutting are researched. Main factors and parameters affecting the cutting quality are analyzed and optimized values of the parameters are determined. The principle of the hydraulic-pneumatic high speed cutting machine is put forward and experiments of high speed cutting is carried out in this machine.Theoretical analysis, bar cutting experiments in high speed cutting machine and metallographic analysis of the cutting surface shows that with the new developed precise cutting theory and technology based on high speed and restrained state, better quality of the cutting materials and products can be obtained.Acknowledgments This study is supported by the National Natural Science Foundation of China (No.50475049).中文译文：基于高速和约束状态下的钢筋切割理论和参数的研究钢筋切割过程对生产效率,产品质量，以及制造业领域中的经济利益有直接的影响。钢筋切削技术理论受到了全世界各地学者们的关注，已成为近些年来研究和探索的热点。但到目前为止，仍没有有效的钢筋切削方法。近年来，提出研究一种高速状态下的先进钢筋切削技术和理论，并且用断裂力学理论知识来分析切割断裂的过程，同时对高速切削变形特性的机理进行了研究，以及对切削参数，如物料温度，切割速度和模具间隙等进行了分析。理论分析和实验证明，可以通过这种新颖的精密切割技术来获得质量更好精度更高的切割材料。1引言钢筋切断是在产品制造以及生产过程中的一项非常重要的过程。钢筋加工的质量对生产效率、产品质量以及经济效益有很大的影响。随着精密成形和精密加工技术的发展，对材料切割质量的需求已经变得越来越高。常用的钢筋切割的方法，因为切割速度较低，而且还有没有剪切装置，误差及切削表面质量不能满足生产的要求。长期以来，来自不同国家的学者们做了大量的理论分析和实验研究，终于在钢筋切割技术领域取得了许多成就。由于切削变形过程是非常复杂的过程，而且对切削表面质量的影响因素很多，到目前为止，仍然是没有有效的理论及高效切割方法用于生产 作者多年来一直致力于精确切削理论和方法的研究。通过查阅和参考现有的研究成果，首次提出了一种新型的精确切割方法。在本文中，提出并研究一种立足于高速约束状态下的先进切削理论。在切割裂纹的过程分析中，用到了断裂力学理论分析方法，同时也对高速切割机以及材料的变形特性进行研究。通过对切割区域内的变形和应力状态的分析，提出了一个适当的加载方法。同时也对每一个切削因素或切削参数进行分析，如切削速度、切削温度，以及约束状态和模具间隙对切割表面质量的影响进行分析，最终获得了最佳的切削参数。与此同时提出了高速切割机的原理。2 切削过程的分析这种在约束状态下进行的钢筋切割是在高速移动的动刀片和固定刀片之间完成操作的，当动刀片由高速驱动并向下移动切割材料时，下夹持刀具跟着产生一个方向向上的力F，这样该材料便可被剪切。与此同时剪切刀具产生另一个剪裁力FZ使得输送材料可以在上部剪切模和固定刀具之间完成剪切，在图1所示图1 剪切过程以及材料的变形1.动刀具 2.上部剪切模3.输送材料 4.固定的刀具5.下部剪切模 6.切割材料如图1所示，在切割过程中的材料可以划分为三个变形区域，即剧烈变形区域I，参与变形区域II和非参与变形区III, 其中所述剧烈变形区域I是最为重要的。材料的在这个区域内的应力状态和变形过程对切割表面的质量有直接影响。在约束状态下进行高速切削，材料在区域I内处在三维的压应力状态下。机械模型在适当的简化后，材料在区域I的应力状态显示于图2。图2 材料在变形区域的应力状态(a) 材料在移动刀刃的应力状态(b) 材料在固定刀刃的应力状态 切削过程可以分为三个步骤：弹性和塑性变形阶段，裂纹产生阶段，和断裂阶段，依据断裂力学理论的知识，材料在断裂过程时的位移区域可表示如下 (1)(2)其中： - 材料的泊松比 E 弹性剪切模量 K 应力强度因数 A-开裂方向和裂纹面之间的夹角 k-系数的计算 r-裂纹尖端塑性区的半径在高速精密切削过程中，变形区域内的材料是处在在三维约束状态下的。在塑性区，裂纹尖端半径可以表示为2 (3)其中为材料的屈服应力如公式（3）所示，高速约束状态下的切削过程产生的塑形裂纹半径要比普通切削过程产生的裂纹半径小50%还多，因此材料在裂纹区域产生的裂纹更加光滑，与此同时裂纹表面的质量会更好。3. 切削参数切削表面的质量受到切削速度、材料温度、约束的状态和模具间隙等诸多因素的影响。通过分析这些切削因素和切削参数，对研究最佳的切削参数提供巨大帮助，分析这些参数同样也为设计高速切割机提供重要依据。3.1切削速度随着切削速度的增加,材料的塑性和断裂韧性将会变得更低。因此切削表面的变形将会减小，同时金属切屑也更容易形成。切割表面光