李响 外文文献翻译(OK)

科毕业设计外文文献及译文文献、资料题目：Research on the Theory and Parameters of 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 Cutting Based on High Speed and Restrained State Bar 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 andmethods 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 die2. Upper clipping die3. Delivered material4. Fixed cutting die5. Lower clipping die6. 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:=μ22cos 21(2sin 2EII)1(θθπν+++k r k (1) )22sin 21(2sin 2II)1(θθπνν++-+=k r E k (2) Where ν- Poisson ratio of materialE -the shearing modulus of elasticityK -stress strength factor of II typed cracklesA-the angle between cracking direction and the crack surfacek- coefficients of calculationr-crackle tip radius in the plastic areaFor 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 as(43π=r )sII δk 2 (3) Where -the yield stress of materialIt 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 parametersThe 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 speedWith 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 stateQuality 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 differentlength-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:D kk 1=δWhere: k-coefficient related with length-diameter ratiok 1- coefficient related material propertiesD-diameter of the materialsAs 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:))(2(gs mw e +=ην Where: W e -the expansion work of the airm- the mass of moving systemg- acceleration of gravityS-the stroke of moving systemη- 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 ConclusionsThe 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.AcknowledgmentsThis 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。