沖壓成形的特點與板材沖壓成形性能#中英文翻譯#外文翻譯匹配

1 Characteristics of Stamping and Properties of Sheet Metal Forming 1 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, leather)can 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 2 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 3 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 4 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. 5 （ 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. 6 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 conditions(stamping 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 results(indirect 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. 7 沖壓成形的特點與板材沖壓成形性能 1概述 沖壓是通過模具使板材產生塑性變形而獲得成品零件的一次成形工藝方法。由于沖壓通常在冷態(tài)下進行，因此也稱為冷沖壓。只有當板材厚度超過 8100mm 時，才采用熱沖壓。沖壓加工的原材料一般為板材或帶材，故也稱板材沖壓。某些非金屬板材（如膠木板、云母片、石棉、皮革等）亦可采用沖壓成形工藝進行加工。 沖壓廣泛應用于金屬制品各行業(yè)中，尤其在汽車、儀表、軍工、家用電器等工業(yè)中占有極其重要的地位。 沖壓成形需研究工藝設備和模具三類基本問題。 板材沖壓具有下列 特點： （ 1）材料利用率高。 （ 2）可加工薄壁、形狀復雜的零件。 （ 3）沖壓件在形狀和尺寸方面的互換性好。 （ 4）能獲得質量輕而強度高、剛性好的零件。 （ 5）生產率高，操作簡單，容易實現機械化和自動化。 沖壓模具制作成本高，因此適合大批量生產。對于小批量、多品種生產，常采用簡易沖模，同時引進沖壓加工中心等新型設備，以滿足市場求新求變的需求。 板材沖壓常用的金屬材料有低碳鋼、銅、鋁、鎂合金及高塑性的合金剛等。如前所述，材料形狀有板材和帶材。 沖壓生產設備有剪床和沖床。剪床是用來將板材剪切成具 有一定寬度的條料，以供后續(xù)沖壓工序使用，沖床可用于剪切及成形。 2沖壓成行的特點 生產時間中所采用的沖壓成形工藝方法有很多，具有多種形式餓名稱，但塑性變形本質是相同的。沖壓成形具有如下幾個非常突出的特點。 （ 1）垂直于板面方向的單位面積上的壓力，其數值不大便足以在板面方向上使 板材產生塑性變形。由于垂直于板面方向上的單位面積上壓力的素質遠小于板面方向上的內應力，所以大多數的沖壓變形都可以近似地當作平面應力狀態(tài)來處理，使其變8 形力學的分析和工藝參數的計算大呢感工作都得到很大的簡化。 （ 2）由于沖壓成形用 的板材毛胚的相對厚度很小，在壓應力作用下的抗失穩(wěn)能力也很差，所以在沒有抗失穩(wěn)裝置（如壓邊圈等）的條件下，很難在自由狀態(tài)下順利地完成沖壓成形過程。因此，以拉應力作用為主的伸長類沖壓成形過程多于以壓應力作用為主的壓縮類成形過程。 （ 3）沖壓成形時，板材毛胚內應力的數值等于或小于材料的屈服應力。在這一點上，沖壓成形與體積成形的差別很大。因此，在沖壓成形時變形區(qū)應力狀態(tài)中的靜水壓力成分對成形極限與變形抗力的影響，已失去其在體積成形時的重要程度，有些情況下，甚至可以完全不予考慮，即使有必要考慮時，其處理方法也不相同 。 （ 4）在沖壓成形時，模具對板材毛胚作用力所形成的約束作用較輕，不像體積成形（如模鍛）是靠與制件形狀完全相同的型腔對毛胚進行全面接觸而實現的強制成形。在沖壓成形中，大多數情況下，板材毛胚都有某種程度的自由度，常常是只有一個表面與模具接觸，甚至有時存在板材兩側表面都有于模具接觸的變形部分。在這種情況下，這部分毛胚的變形是靠模具對其相鄰部分施加的外力實現其控制作用的。例如，球面和錐面零件成形時的懸空部分和管胚端部的卷邊成形都屬這種情況。 由于沖壓成形具有上述一些在變形與力學方面的特點，致使沖壓技術也 形成了一些與體積成形不同的特點。 由于不需要在板材毛的表面施加很大的單位壓力即可使其成 形，所以在沖壓技術中關于模具強度與剛度的研究并不十分重要，相反卻發(fā)展了學多簡易模具技術。由于相同 原因，也促使靠氣體或液體壓力成形的工藝方法得以發(fā)展。 因沖壓成形時的平面應力狀態(tài)或更為單純的應變狀態(tài)（與體積成形相比），當前對沖壓成形匯中毛胚的變形與 力能參數方面的研究較為深入，有條件運用合理的科學方法進行沖壓加工。借助于電子計算機 與先進的測試手段，在對板材性能與沖壓變形參數進行實時測量與分析 基礎上，實現沖壓過程智能化控制的研 究工作也在開展。 人們在對沖壓成形過程有離開較為深入的了解后，已經認識到沖壓成型與原材料有十分密切的關系。所以，對板材沖壓性能即成形性與形狀穩(wěn)定性的研究，目前已成為沖壓技術的一個重要內容。對板材沖壓性能的研究工作不僅是沖壓技術發(fā)展的需要，而且也促進了鋼鐵工業(yè)生產技術的發(fā)展，為其提高板材的質量提供了一個可靠的基礎與依據。 9 3沖壓變形的分類 沖壓變形工藝可完成多種工序，其基本工序可分為分離工序和變形工序兩大類。 分離工序是使胚料的一部分與另一部分相互分離的工藝方法，主要有落料、沖孔、切邊、 剖切、修整等。其中又以沖孔、落料應用最廣。變形工序是使胚料的一部分相對于另一部分產生位移而不破裂的工藝方法，主要有拉深、彎曲、局部成形、脹形、翻邊、縮徑、校形、旋壓等。 從本質上看，沖壓成形就是毛胚的變形