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外文翻译-----冲压成形与板材冲压-其他专业.doc

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外文翻译-----冲压成形与板材冲压-其他专业.doc

Characteristics and Sheet Metal Forming 1.The article overview Stamping is a kind of plastic forming process in which a part is produced by means of the plastic forming the material under the action of a die. Stamping is usually carried out under cold state, so it is also called stamping. Heat stamping is used only when the blank thickness is greater than 8100mm. The blank material for stamping is usually in the form of sheet or strip, and therefore it is also called sheet metal forming. Some non-metal sheets such as plywood, mica sheet, asbestos, leathercan also be formed by stamping. Stamping is widely used in various fields of the metalworking industry, and it plays a crucial role in the industries for manufacturing automobiles, instruments, military parts and household electrical appliances, etc. The process, equipment and die are the three foundational problems that needed to be studied in stamping. The characteristics of the sheet metal forming are as follows 1 High material utilization 2 Capacity to produce thin-walled parts of complex shape. 3 Good interchangeability between stamping parts due to precision in shape and dimension. 4 Parts with lightweight, high-strength and fine rigidity can be obtained. 5 High productivity, easy to operate and to realize mechanization and automatization. The manufacture of the stamping die is costly, and therefore it only fits to mass production. For the manufacture of products in small batch and rich variety, the simple stamping die and the new equipment such as a stamping machining center, are usually adopted to meet the market demands. The materials for sheet metal stamping include mild steel, copper, aluminum, magnesium alloy and high-plasticity alloy-steel, etc. Stamping equipment includes plate shear punching press. The former shears plate into strips with a definite width, which would be pressed later. The later can be used both in shearing and forming. 2.Characteristics of stamping forming There are various processes of stamping forming with different working patterns and names. But these processes are similar to each other in plastic deformation. There are following conspicuous characteristics in stamping (1).The force per unit area perpendicular to the blank surface is not large but is enough to cause the material plastic deformation. It is much less than the inner stresses on the plate plane directions. In most cases stamping forming can be treated approximately as that of the plane stress state to simplify vastly the theoretical analysis and the calculation of the process parameters. (2).Due to the small relative thickness, the anti-instability capability of the blank is weak under compressive stress. As a result, the stamping process is difficult to proceed successfully without using the anti-instability device such as blank holder. Therefore the varieties of the stamping processes dominated by tensile stress are more than dominated by compressive stress. (3).During stamping forming, the inner stress of the blank is equal to or sometimes less than the yield stress of the material. In this point, the stamping is different from the bulk forming. During stamping forming, the influence of the hydrostatic pressure of the stress state in the deformation zone to the forming limit and the deformation resistance is not so important as to the bulk forming. In some circumstances, such influence may be neglected. Even in the case when this influence should be considered, the treating method is also different from that of bulk forming. (4).In stamping forming, the restrain action of the die to the blank is not severs as in the case of the bulk forming such as die forging. In bulk forming, the constraint forming is proceeded by the die with exactly the same shape of the part. Whereas in stamping, in most cases, the blank has a certain degree of freedom, only one surface of the blank contacts with the die. In some extra cases, such as the forming of the blank on the deforming zone contact with the die. The deformation in these regions are caused and controlled by the die applying an external force to its adjacent area. Due to the characteristics of stamping deformation and mechanics mentioned above, the stamping technique is different form the bulk metal forming (1).The importance or the strength and rigidity of the die in stamping forming is less than that in bulk forming because the blank can be formed without applying large pressure per unit area on its surface. Instead, the techniques of the simple die and the pneumatic and hydraulic forming are developed. (2).Due to the plane stress or simple strain state in comparison with bulk forming, more research on deformation or force and power parameters has been done. Stamping forming can be performed by more reasonable scientific methods. Based on the real time measurement and analysis on the sheet metal properties and stamping parameters, by means of computer and some modern testing apparatus, research on the intellectualized control of stamping process is also in proceeding. (3).It is shown that there is a close relationship between stamping forming and raw material. The research on the properties of the stamping forming, that is, forming ability and shape stability, has become a key point in stamping technology development, but also enhances the manufacturing technique of iron and steel industry, and provides a reliable foundation for increasing sheet metal quality. 3.Categories of stamping forming Many deformation processes can be done by stamping, the basic processes of the stamping can be divided into two kinds cutting and forming. Cutting is a shearing process that one part of the blank is cut from the other. It mainly includes blanking, punching, trimming, parting and shaving, where punching and blanking are the most widely used. Forming is a process that one part of the blank has some displacement from the other. It mainly includes deep drawing, bending, local forming, bulging, flanging, necking, sizing and spinning. In substance, stamping forming is such that the plastic deformation occurs in the deformation zone of the stamping blank caused by the external force. The stress state and deformation characteristic of the deformation zone are the basic factors to decide the properties of the stamping forming. Based on the stress state and deformation characteristics of the deformation zone, the forming methods can be divided into several categories with the same forming properties and be studied systematically. The deformation zone in almost all types of stamping forming is in the plane stress state. Usually there is no force or only small force applied on the blank surface. When is assumed that the stress perpendicular to the blank surface equals to zero, two principal stresses perpendicular to each other and act on the blank surface produce the plastic deformation of the material. Due to the small thickness of the blank, it is assumed approximately the two principal stresses distribute uniformly along the thickness direction. Based on this analysis, the stress state and the deformation characteristics of the deformation zone in all kinds of stamping forming can be denoted by the points in the coordinates of the plane principal stresses and the coordinates of the corresponding plane principal strains. 4.Raw materials for stamping forming There are a lot of raw materials used in stamping forming, and the properties of these materials may have large difference. The stamping forming can be succeeded only by determining the stamping method, the forming parameters and the die structures according to the properties and characteristics of the raw materials. The deformation of the blank during stamping forming has been investigated quite thoroughly. The relationships between the material properties decided by the chemistry component and structure of the material and the stamping forming has been established clearly. Not only the proper material can be selected based on the working condition and usage demand, but also the new material can be developed according to the demands of the blank properties during processing the stamping part. This is an important domain in stamping forming research. The research on the material properties for stamping forming is as follows (1).Definition of the stamping property of the material. (2).Method to judge the stamping property of the material, find parameters to express the definitely material property of the stamping forming, establish the relationship between the property parameters and the practical stamping forming, and investigate the testing methods of the property parameters. (3).Establish the relationship among the chemical component, structure, manufacturing process and stamping property. The raw materials for stamping forming mainly include various metals and nonmetal plate. Sheet metal includes both ferrous and nonferrous metals. Although a lot of sheet metals are used in stamping forming, the most widely used materials are steel, stainless steel, aluminum alloy and various composite metal plates. 5.Stamping forming property of sheet metal and its assessing method The stamping forming property of the sheet metal is the adaptation capability of the sheet metal to stamping forming. It has crucial meaning to the investigation of the stamping forming property of the sheet metal. In order to produce stamping forming parts with most scientific, economic and rational stamping forming process and forming parameters, it is necessary to understand clearly the properties of the sheet metal, so as to utilize the potential of the sheet metal fully in the production. On the other hand, to select plate material accurately and rationally in accordance with the characteristics of the shape and dimension of the stamping forming part and its forming technique is also necessary so that a scientific understanding and accurate judgment to the stamping forming properties of the sheet metal may be achieved. There are direct and indirect testing methods to assess the stamping property of the sheet metal. Practicality stamping test is the most direct method to assess stamping forming property of the sheet metal. This test is done exactly in the same condition as actual production by using the practical equipment and dies. Surely, this test result is most reliable. But this kind of assessing method is not comprehensively applicable, and cannot be shared as a commonly used standard between factories. The simulation test is a kind of assessing method that after simplifying and summing up actual stamping forming methods, as well as eliminating many trivial factors, the stamping properties of the sheet metal are assessed, based on simplified axial-symmetric forming method under the same deformation and stress states between the testing plate and the actual forming states. In order to guarantee the reliability and generality of simulation results, a lot of factors are regulated in detail, such as the shape and dimension of tools for test, blank dimension and testing conditionsstamping velocity, lubrication method and blank holding force, etc. Indirect testing method is also called basic testing method its characteristic is to connect analysis and research on fundamental property and principle of the sheet metal during plastic deformation, and with the plastic deformation parameters of the sheet metal in actual stamping forming, and then to establish the relationship between the indirect testing resultsindirect testing value and the actual stamping forming property forming parameters. Because the shape and dimension of the specimen and the loading pattern of the indirect testing are different from the actual stamping forming, the deformation characteristics and stress states of the indirect test are different from those of the actual one. So, the results obtained form the indirect test are not the stamping forming parameters, but are the fundamental parameters that can be used to represent the stamping forming property of the sheet metal. 冲压成形与板材冲压 1.概述 通过模具使板材产生塑?#21592;?#24418;而获得成品零件的一次成形工艺方法叫做冲压。由于冲压通常在冷态下进行,因此也称为冷冲压。只有当板材厚度超过8100mm?#20445;?#25165;采用热冲压。冲压加工?#33041;?#26448;料一般为板材或带材,故也称板材冲压。某些非金属板材(如胶木板、云母片、石棉、皮革等)亦可采用冲压成形工艺进行加工。 冲压广泛应用于金属制品各行业中,尤其在汽车、仪表、军工、家用电器等工业中占有极其重要的地位。 冲压成形需研究工艺设备和模具三类基本问题。 板材冲压具有下列特点 (1).高的材料利用率。 (2).可加工薄壁、形状复杂的零件。 (3).冲压件在形状和尺寸方面的互换性好。 (4).能获得质量轻而强度高、刚性好的零件。 (5).生产率高,操作简单,容?#36164;迪只?#26800;化和自动化。 冲压模具制作成本高,因此适合大批?#21487;?#20135;。对于小批量、多?#20998;?#29983;产,常采用简易冲模,同时引进冲压加工中心等新型设备,以满足市场求新求变的需求。 板材冲压常用的金属材料有低碳钢、铜、铝、镁合金及高塑性的合金刚?#21462;?#22914;前所述,材料形状有板材和带材。 冲压生产设备有剪床和冲床。剪床是用来将板材剪切成具有?#27426;?#23485;度的条料,以供后续冲压工序使用,冲?#37096;?#29992;于剪切及成形。 2.冲压成形的特点 生产时间中所采用的冲压成形工艺方法有很多,具有多种形式饿名称,但塑?#21592;?#24418;本质是相同的。冲压成形具有如下几个非常突出的特点。 (1).垂直于板面方向的单位面积上的压力,其数值不大便足以在板面方向上使 板材产生塑?#21592;?#24418;。由于垂直于板面方向上的单位面积上压力的素?#35797;?#23567;于板面方向上的内应力,所?#28304;?#22810;数的冲压变形都可以近似地当作平面应力状态来处理,使其变形力学的分析和工艺?#38382;?#30340;计算大呢感工作都得到很大的简化。 (2).由于冲压成形用的板材毛胚的相对厚度很小,在压应力作用下?#30446;?#22833;稳能力也很差,所以在没有抗失稳装置(如压边圈等)的条件下,很难在自由状态下顺利地完成冲压成形过程。因此,以拉应力作用为主的伸长类冲压成形过程多于以压应力作用为主的压缩类成形过程。 (3).冲压成形?#20445;?#26495;材毛胚内应力的数?#26723;?#20110;或小于材料的屈服应力。在这一点上,冲压成形与体积成形的差别很大。因此,在冲压成形时变形区应力状态中的?#33756;?#21387;力成分对成形极限与变形抗力的影响,已失去其在体积成形时的重要程度,有些情况下,甚至可以完全不予考虑,即使有必要考虑?#20445;?#20854;处理方法也不相同。 (4).在冲压成形?#20445;?#27169;具对板材毛胚作用力所形成?#33041;?#26463;作用较轻,不像体积成形(如模锻)?#24378;?#19982;制件形状完全相同的型?#27426;?#27611;胚进行全面接触而实现的强制成形。在冲压成形中,大多数情况下,板材毛胚都有?#25345;?#31243;度的自由度,常常是只有一个表面与模具接触,甚至有时存在板材两侧表面都有于模具接触的变形部分。在这种情况下,这部分毛胚的变形?#24378;?#27169;具对其相邻部分施加的外力实现其控制作用的。例如,球面和锥面零件成形时的悬空部分和管胚端部的卷边成形都属这种情况。 由于冲压成形具有上述一些在变形与力学方面的特点,致使冲压技术也形成了一些与体积成形不同的特点。 由于不需要在板材毛的表面施加很大的单位压力即可使其成形,所以在冲压技术中关于模具强度与刚度的研究并不十分重要,相反却发展?#25628;?#22810;简易模具技术。由于相同原因,也促使靠气体或液体压力成形的工艺方法得以发展。 因冲压成形时的平面应力状态或更为单纯的应变状态(与体积成形相比),当前对冲压成形汇中毛胚的变形与 力能?#38382;?#26041;面的研究较为深入,有条件运用合理?#30446;?#23398;方法进行冲压加工。借助于电子计算机与先进的测试手段,在对板材性能与冲压变形?#38382;?#36827;行实时测量与分析基础上,实现冲压过程智能化控制的研究工作也在开展。 人们在对冲压成形过程有离开较为深入的?#31169;?#21518;,已经认识到冲压成型与原材料有十分密切的关系。所以,对板材冲压性能即成形性与形?#27425;?#23450;性的研究,目前已成为冲压技术的一个重要内容。对板材冲压性能的研究工作不仅是冲压技术发展的需要,而且也促进了钢铁工业生产技术的发展,为其提高板材的质量提供了一个可靠的基础与依据。 3.冲压变形的分类 冲压变形工艺可完成多种工序,其基本工序可分为分离工序和变形工序两大类。 分离工序是使胚料的一部分与另一部分相互分离的工艺方法,主要有落料、冲孔、切边、?#26159;小?#20462;整?#21462;?#20854;中又以冲孔、落料应用最广。变形工序是使胚料的一部分相对于另一部分产生位移而不破裂的工艺方法,主要有拉深、弯曲、局部成形、胀形、翻边、缩径、校形、旋压?#21462;?从本质上看,冲压成形就是毛胚的变形区在外力的作用下产生相应的塑?#21592;?#24418;,所?#21592;?#24418;区内的应力状态和变形特点景象的冲压成形分类,可以把成形性质相同的成形方法概括成同一个类型并进行体系化的研究。 绝大多数冲压成形时毛胚变形区均处于平面应力状态。通常认为在板材表面上不受外力的作用,即使有外力作用,其数值也是较小的,所以可以认为垂直于板面方向上的应力为零,使板材毛胚产生塑?#21592;?#24418;的是作用于板面方向上相互的两个主应力。由于板厚较小,通常都近似地认为这两个主应力在厚度方向上是均匀分布的。基于这样的分析,可以?#36805;?#31181;形式冲压成型中的毛陪变形区的受力状态与变形特点,在平面应力的应力坐标系中与相应的两向应变坐标系中以应力与应变坐标决定的位置来表示。 4.冲压用原材料 冲压加工用原材料有很多种,它们的性能也有很大的差别,所?#21592;?#39035;根据原材料的性能与特点,采用不同的冲压成形方法、工艺?#38382;?#21644;模具结构,才能达到冲压加工的目的。由于人们对冲压成形过程板材毛胚的变形?#24418;?#26377;?#31169;?#20026;深入的认识,已经相当清楚的建立了由原材料的化学成分、组织等因素所决定的材料性能与冲压成形之间的关系,这就使原材料生产部门不但按照冲压件的工作条件与使用要求进行原材料的设计工作,而且也根据冲压件加工过程对板材性能的要求进行新型材料?#30446;?#21457;工作,这是冲压技术在原材料研究方面的一个重要方向。对 冲压用原材料冲压性能方面的研究工作有 (1)原材料冲压性能的含义。 (2)判断原材料冲压性能?#30446;?#23398;方法,?#33539;?#21487;以?#38750;?#21453;映材料冲压性能的?#38382;?#24314;立冲压性能的?#38382;?#19982;?#23548;?#20914;压成形间的关系,以及冲压性能?#38382;?#30340;测试方法?#21462;?(3)建立原材料的化学成分、组织和制造过程与冲

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