支板的沖壓復(fù)合模具設(shè)計(jì)【底端長度32】【15張CAD圖紙+PDF圖】
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河南機(jī)電高等?？茖W(xué)校畢業(yè)設(shè)計(jì)說明書/論文
參考文獻(xiàn)
【1】 楊占堯.沖壓模具圖冊.北京：高等教育出版社，2004.
【2】 歐陽波儀.現(xiàn)代冷沖壓模設(shè)計(jì).北京：化學(xué)工業(yè)出版社，2006.
【3】 寇世瑤.機(jī)械制圖.北京：高等教育出版社，2004.
【4】 原紅玲.沖壓工藝與模具設(shè)計(jì).北京：機(jī)械工業(yè)出版社，2008.
【5】 翁其金.冷沖壓技術(shù). 北京：機(jī)械工業(yè)出版社，2000.
【6】 翟德梅，段維峰.模具制造技術(shù). 北京：化學(xué)工業(yè)出版社，2005.
【7】 趙偉閣.模具設(shè)計(jì).西安:西安電子科技大學(xué)出版社,2006.
【8】 李學(xué)峰.模具設(shè)計(jì)與制造實(shí)訓(xùn)教程.北京：化學(xué)工業(yè)出版社，2004.
外文資料與中文翻譯
外文資料：
Analysis on The Factors of Impacting on The Life of Stamping Die
REN Hai-dong．YU Ling
Abstract：Stamping is a wide range of material processing methods，stamping die is equipment to achieve the important parts of theprocessing，whose life directly afects quality an d cost ofthe product．This article analyzes to its influencing factors，finding a method tosolveproblems，andimprovethelifeof stamping die．
Keywords：Samping die；life；Infl uencing facto
Is the use of stamping presses installed in the die pressure on the material to produce plastic deformation or separation in order to obtain the parts needed for a pressure processing method. In industrial production, especially in household appliances, automotive, aerospace and engineering fields such as instrumentation is widely available. The die is the realization of this important technology components and equipment for processing. Die as a result of a long cycle of production and processing, the use of the high cost of materials, manufacturing costs in product cost of production occupies a significant proportion, therefore, to improve the life of stamping dies is very important. Through the use of molds, for various reasons can not be a reproduction of the red pieces of qualified, could no longer be repaired, which is commonly referred to as die failure. Die life by various forms of limitations expired, common are: wear failure, failure deformation, fracture failure and failure, such as bite wounds. Stamping processes, as well as due to different working conditions of the different effects of stamping die failure are many factors, but the same factors may also bring some form of failure. In this paper, an analysis of its influencing factors, possible solutions to the problem in order to achieve the purpose of die life.
1 Mold Design
Mold design, including structural design and parts design. The structure of mold not only affects the quality of parts produced to determine the productivity of enterprises and processing methods, but also to improve the life of mold also has a key role. Therefore, before designers to make full preparations to meet the production tooling to optimize the structure at the same time.
1.1 Parts of Product Design
Reasonable product design will help improve the life of mold. If the product has a cusp, or fillet radius is too small, the design of the edge will die due to stress concentration and cracking. Without prejudice to the structure and function of products, we can change the design of some of its unreasonable.
1.2 Die Structure Design
Reasonable structure can improve the die life. For example, in Die, the direction to improve the convex and concave stamping die in the course of the relative stability, thus ensuring the mold space at a reasonable framework of blanking blanking. And the reasonableness of blanking clearance and stability to improve die life is an important measure. Accurate reduced-oriented relationship between the relative movement of the wear and tear of parts and components to avoid the convex, concave die as a result of unreasonable gap a "bite injuries" and other forms of failure. Particularly in the Fine Blanking Die, the high-precision mold-oriented institutions is to ensure that the structural design of an important guarantee for success. Therefore in order to improve the life of mold, the form must be the right choice and guide precision-oriented. The choice of orientation should be higher than the accuracy of convex and concave mold with precision. For more blanking punch, punch in a number of large difference in diameter, there is a difference and close the case that if a small and a long punch, then easily lead to instability or break. We can punch arranged in Figure 1 (a) ladder-style in order to increase its stiffness. Punching holes for the need to increase the punch guide in order to enhance the strength of punch, which is to ensure the normal work of stamping dies to the premise. Which can increase many-oriented approach, to be used in Figure 1 (b) shown in the front and the entire process-oriented and other-oriented.
Figure 1 (a) ladder layout punch 1 (b) punch-oriented
Accurate calculation of the process can also increase mold life. Such as discharge power and the calculation of stroke. If we are not allowed to easily spring fatigue fracture or failure. Die on a high degree of calculation, as well as the choice of press and reasonable manner and location-oriented institutions can effectively improve the die life. Modulus of continuity for the design and layout of the ride side of the calculation of size is also crucial.
1.3 Die gap
Stamping dies when space is the convex, concave die size difference between the horizontal edge. Gap on the impact of a large die life is a stamping process and die design of an extremely important issue. Convex, concave die gap size of a direct impact on product quality and mold the life space is too large or too small will cause the edge passivation or wear and tear (as shown in Figure 2). Die materials drop to die later, punch to punch prevail, and these two dimensions has been the impact of space. The experimental results show that the thickness of the gap below 2 percent, prone punch damage, space for more than 6%, there had been errors in parts size. Gap in the thickness of 4% ~ 5%, the effect of blanking good stability. Die gap, therefore the correct choice is to ensure that an important way to die life. At present, the choice of space data in addition to investigations, the most by the actual experience.
(a) gap is too small (b) a reasonable gap (c) gap is too large
Figure 2 gap on the impact of stampings
2 Die Manufacturing
Mold manufacturing process design is reasonable, to ensure that mold is an important way of life. Most of mold manufacturing parts of the process can be carried out in accordance with the normal, but there are special requirements for spare parts or spare parts for local processing, will need to have some special methods.
2.1 Mechanical Rough
Material machining accuracy of the assembly of the mold affects accuracy, it will directly affect the mold of parallelism, perpendicularity and coaxiality. In addition, the marks left rough, worn, are prone to stress concentration sites, but also occurred in the early fatigue cracks and the local.
2.2 Heat Treatment
Heat Treatment in the manufacture of stamping die plays a very important role, in spite of different types and different structure of mold, the use of different steel products, or using different machining and processing of shape, but they need to use heat treatment process to obtain a higher hardness and wear resistance, as well as other mechanical properties required. In general, the die service life and quality of products produced to a large extent depends on the quality of heat treatment processing. Thus, in die manufacturing, and continuously improve the skill level of heat treatment, a reasonable template to improve the performance of internal organization and working methods, it is particularly important. Heat treatment time and temperature is an important factor, because of the time in different temperatures, heat treatment may constitute a different form, the main annealing, normalizing, quenching and tempering, and carburizing, nitriding, carbonitriding, etc.. For example, in the blanking die, because people punch wedge material is the work of more serious wear and tear parts, so the hardness should be greater in general for the HRC 60 ~ 63, die for the HRC 57 ~ 60, this kind of hardness than the two , or die punch hardness is higher than the longer die life.
3 Die Assembly and Debugging
Assembly is the key to mold production process. A direct impact on the quality of the die assembly of the quality of parts, dies and the life of the state of the technology. Die assembly includes two aspects:
(1) good parts of each machining process in accordance with requirements of drawings assembled into a general assembly and assembly;
(2) in the assembly process as part of the processing work. Die in the assembly as an example, the technical requirements is to ensure consistency blanking gap and ensure the accuracy of direction-oriented institutions, as well as the movement to ensure that all relevant pieces of die design in accordance with strict technical parameters. This is a debugging tool to ensure a successful and smooth conduct of the production protection, but also to ensure that an important factor in mold life. In recent years, with the development of the production, users are vulnerable to damage parts of the swap request, so that users die at the scene of the rapid replacement of damaged parts. Die before the test mode, it should also be designed in strict accordance with the technical parameters of the model to select press. It is closely related to the length of die life. Press the stiffness, precision, crucial parameters such as tonnage. Press one of the stiffness of stiffness by the bed, transmission stiffness and rigidity of three parts-oriented, if less stiffness, load and unloading end, the die gap, great changes will happen, it will affect the accuracy of stamping parts and mold life. Die after assembly, must be red and adjust the test can be used for production. In order to protect the mold, the first time in debugging, it is necessary to pay attention to the use of paper or aluminum, as well as cold-rolled plate red test. To ensure that edge punch die edge into the depth of the scope of a reasonable (usually for a material thickness). Stamping die so red when the level of stress and wear and tear will be minimal, and fully protect the convex and concave mold, increased die life. The purpose of debugging and the task is: to die out not only qualified stampings, security and stability but also put into production use. Should be based on examination of stamping defects, analysis of its causes and try to solve them. Some bending, deep drawing and flanging, etc. so that the deformation of sheet metal dies, stamping parts, when the shape of complex or high accuracy, it is difficult to accurately calculate the deformation of the former size and shape of the rough. For this type of stamping parts, although the relevant references are rough calculation methods and formulas, but the impact of plastic deformation as a result of many factors, calculated from the size and needs of different size. In the actual production in order to obtain more accurate size, often determined through experiments. Red in the test set to adjust the size of blank.
4 Conclusion
Stamping die life impact of a number of factors, from the above analysis we can see from the mold design to the use of the entire process can improve the die life. Practice has proved that the rational design of die structure and the shape of the die using the appropriate manufacturing processes, heat treatment process, so that die in the normal conditions, can increase the mold life.
References:
[1] Weng its gold. Cold stamping technology [M]. Beijing: Mechanical Industry Press, 2007.
[2] Liu, ZHANG Bao-zhong. Stamping die design and manufacture of [M]. Beijing: Higher Education Publishing
Agency. 2006.
[3]Xiaopei.wang. Stamping Manual [M]. Beijing: Mechanical Industry Press, 2006.
中文翻譯：
影響沖壓模具壽命的因素分析
任海東，于玲
摘要：沖壓成形是一種應(yīng)用廣泛的材料加工方法，沖壓模具是實(shí)現(xiàn)零件加工的重要工藝裝備，它的使用壽命直接影響到產(chǎn)品的質(zhì)量和成本。對模具壽命的影響因素加以分析，找出解決問題的方法，從而達(dá)到提高模具壽命的目的。
關(guān)鍵詞：沖壓模具：壽命；影響因素
沖壓是利用安裝在壓力機(jī)上的沖模對材料施加壓力，使其產(chǎn)生分離或塑性變形，從而獲得所需要的零件的一種壓力加工方法。它在工業(yè)生產(chǎn)中，尤其是在家用電器、汽車、航空以及儀器儀表等工程領(lǐng)域獲得廣泛應(yīng)用。而沖模就是實(shí)現(xiàn)這一零件加工的重要工藝裝備。由于模具的生產(chǎn)加工周期長，使用的材料費(fèi)用高，制造成本在產(chǎn)品生產(chǎn)成本中占有相當(dāng)大的比例，因此，提高沖壓模具的壽命是非常重要的。模具經(jīng)過使用，由于種種原因不能再生產(chǎn)出合格的沖件，也不能再修復(fù)，這種情況一般稱為模具失效。模具壽命受各種失效形式的限制，常見的有：磨損失效、變形失效、斷裂失效及啃傷失效等。由于沖壓工序不同以及工作條件的不同，影響沖壓模具失效的因素很多，而同一種因素也可能帶來幾種失效形式。本文對其影響因素進(jìn)行分析，找出解決問題的方法，從而達(dá)到提高模具壽命的目的。
1 模具設(shè)計(jì)
模具設(shè)計(jì)包括結(jié)構(gòu)設(shè)計(jì)和零部件設(shè)計(jì)。模具的結(jié)構(gòu)不僅能影響到所生產(chǎn)零件的質(zhì)量，決定企業(yè)的生產(chǎn)效率和加工方式，而且對提高模具的使用壽命也具有關(guān)鍵的作用。因此設(shè)計(jì)者在設(shè)計(jì)之前，要做好充分的準(zhǔn)備工作，在滿足生產(chǎn)的同時(shí)盡可能優(yōu)化模具結(jié)構(gòu)。
1．1 零件產(chǎn)品設(shè)計(jì)
合理的產(chǎn)品設(shè)計(jì)有利于提高模具的壽命。如果產(chǎn)品具有尖角，或圓角半徑太小，所設(shè)計(jì)的凹模刃口就會因應(yīng)力集中而開裂。在不影響產(chǎn)品結(jié)構(gòu)和功能的前提下，我們可以改變其一些不合理的設(shè)計(jì)。
1．2 模具結(jié)構(gòu)設(shè)計(jì)
合理的結(jié)構(gòu)可以提高模具的壽命。例如在沖裁模中，導(dǎo)向機(jī)構(gòu)提高了凸、凹模在沖壓過程中的相對穩(wěn)定性，從而保證模具在合理的沖裁間隙范圍內(nèi)進(jìn)行沖裁。而沖裁間隙的合理性及穩(wěn)定性正是提高模具壽命的重要措施。精確的導(dǎo)向減少了有相對運(yùn)動關(guān)系的零部件的磨損，避免了凸、凹模由于間隙不合理出現(xiàn)“啃傷”等失效形式。尤其在精密沖裁模中，高精度的
導(dǎo)向機(jī)構(gòu)是確保模具結(jié)構(gòu)設(shè)計(jì)成功的重要保障。因而為了提高模具的壽命，必須正確選擇導(dǎo)向形式和導(dǎo)向精度。導(dǎo)向精度的選擇應(yīng)高于凸、凹模的配合精度。對于多凸模沖裁，在幾個(gè)凸模直徑相差較大，相距又很近的情況下，如果小凸模細(xì)小而又較長，則容易造成失穩(wěn)或折斷。我們可以把凸模布置成如圖1(a)階梯式的，以增加其剛度。對于小孔沖裁，必須增加對凸模的導(dǎo)向，以提高凸模的強(qiáng)度，這是保證沖壓模具能正常工作的前提。其中能增加導(dǎo)向的方法很多，可采用如圖1(b)所示的前端導(dǎo)向和全程導(dǎo)向等。
準(zhǔn)確的工藝計(jì)算也可以提高模具的壽命。如卸料力及行程的計(jì)算。若計(jì)算不準(zhǔn)，容易造成彈簧的疲勞斷裂或失效。對合模高度的計(jì)算以及壓力機(jī)的選擇，合理的定位方式及導(dǎo)向機(jī)構(gòu)等，都可以有效地提高模具的使用壽命。對于連續(xù)模排樣的設(shè)計(jì)和搭邊尺寸的計(jì)算也至關(guān)重要。
1．3 模具間隙
模具間隙是指沖壓時(shí)凸、凹模刃口橫向尺寸之差。間隙對模具壽命的影響很大，是沖壓工藝與模具設(shè)計(jì)中的一個(gè)極其重要的問題。凸、凹模間隙的大小直接影響產(chǎn)品的質(zhì)量和模具的使用壽命，間隙過大或過小都會使刃口鈍化或磨損(如圖2所示)。沖裁模中落料一般以凹模為準(zhǔn)，沖孔以凸模為準(zhǔn)，而這兩個(gè)尺寸又受到間隙的影響。實(shí)驗(yàn)表明，間隙在板厚的2％以下時(shí)，凸模容易發(fā)生損壞，間隙在6％以上時(shí)，制件尺寸出現(xiàn)誤差。間隙在板厚4％ ～5％時(shí)，沖裁穩(wěn)定效果好。因此正確選擇模具間隙，是保證模具壽命的重要途徑。目前，間隙的選擇除了查資料以外，大部分靠實(shí)際經(jīng)驗(yàn)獲得。
2 模具制造
模具制造工藝設(shè)計(jì)的合理性，也是保證模具壽命的重要途徑。大部分模具零件的制造可以按正常的工藝進(jìn)行，但對有特別要求的零件或零件局部加工，就需要有一定特殊的方法。
2．1 機(jī)械粗加工
材料的加工精度對模具的裝配精度有很大的影響，將直接影響模具的平行度、垂直度和同軸度。另外，粗加工留下的刀痕、磨痕，都是容易產(chǎn)生應(yīng)力集中的部位，也是早期產(chǎn)生裂紋和發(fā)生疲勞的地方。
2．2 熱處理
熱處理在沖壓模具的制造中起著很重要的作用，盡管不同類型及不同的結(jié)構(gòu)模具，使用不同的鋼材，或采用不同的機(jī)械加工及加工成形，但都需要用熱處理的加工方法，使其獲得較高的硬度和耐磨性，以及其他所要求的力學(xué)性能。一般來說，沖模的使用壽命及生產(chǎn)出來的產(chǎn)品質(zhì)量，在很大程度上取決于熱處理加工質(zhì)量．因此，在沖模制造中，不斷提高熱處理的技術(shù)水平，合理的改進(jìn)模板內(nèi)部組織和性能的工作方法，就顯得格外的重要。時(shí)間和溫度是熱處理的重要因素，由于時(shí)間溫度的不同，可構(gòu)成不同的熱處理形式，其主要有退火、正火、淬火、回火和滲碳、滲氮、碳氮共滲等。比如在沖裁模中，由于凸模楔人材料，是磨損比較嚴(yán)重的工作零件，所以其硬度應(yīng)大些，一般為HRC 60～63，凹模為HRC 57～60，這樣比兩者硬度樣，或凹模硬度高于凸模的模具壽命更長一些。
3 模具裝配及調(diào)試
裝配是模具生產(chǎn)中的關(guān)鍵工序。沖模裝配質(zhì)量直接影響制件的質(zhì)量、沖模的技術(shù)狀態(tài)和使用壽命。沖模的裝配工作包括兩方面的內(nèi)容：
(1)將每個(gè)加工好的零件按圖紙工藝要求裝配成組合件及總體裝配；
(2)在裝配過程中進(jìn)行的一部分加工工作。以沖裁模的裝配為例，其技術(shù)要求是保證沖裁間隙一致性，保證導(dǎo)向機(jī)構(gòu)的導(dǎo)向精度，以及保證各相關(guān)運(yùn)動件能夠按照模具設(shè)計(jì)的技術(shù)參數(shù)嚴(yán)格進(jìn)行。這是保證模具調(diào)試成功及生產(chǎn)能夠順利進(jìn)行的保障，也是確保模具壽命的重要因素。近年來，隨著生產(chǎn)的發(fā)展，用戶對易損壞零件提出了互換要求，以便用戶在現(xiàn)場對模具損壞零件的迅速更換。模具在試模前，還應(yīng)該嚴(yán)格按照設(shè)計(jì)的技術(shù)參數(shù)來選擇壓力機(jī)的型號。它關(guān)系到模具使用壽命的長短。壓力機(jī)的剛度、精度、噸位等參數(shù)至關(guān)重要。其中壓力機(jī)的剛度是由床身剛度、傳動剛度和導(dǎo)向剛度三部分組成，如果剛度較差，負(fù)載終了和卸載時(shí)，模具間隙會發(fā)生很大變化，將會影響到?jīng)_壓件的精度和模具壽命。模具裝配完后，必須經(jīng)過試沖和調(diào)整，才能進(jìn)行生產(chǎn)使用。為了保護(hù)模具，在第一次調(diào)試時(shí)，要注意利用紙片或鋁片以及冷軋板進(jìn)行試沖。保證凸模刃口進(jìn)入到凹模刃口的深度在合理的范圍內(nèi)(一般為一個(gè)料厚)。這樣模具沖壓時(shí)的沖壓力及磨損程度會最小，充分保護(hù)了凸、凹模，提高了模具壽命。調(diào)試的目的和任務(wù)是：使沖模不僅能沖出合格的沖壓件，而且能安全穩(wěn)定的投入生產(chǎn)使用。應(yīng)根據(jù)試沖件中出現(xiàn)的缺陷，分析其產(chǎn)生的原因，設(shè)法加以解決。有些彎曲、拉深及翻邊等使板料變形的沖模，當(dāng)沖壓件的形狀復(fù)雜或精度較高時(shí)，很難精確計(jì)算出變形前的毛坯尺寸和形狀。對于這一類沖壓件，雖然相關(guān)參考資料都有計(jì)算毛坯的方法和公式，但由于影響塑性變形的因素非常多，計(jì)算出來的尺寸和實(shí)際的需要尺寸是有差別的。在實(shí)際的生產(chǎn)中為了得到較準(zhǔn)確的尺寸，往往通過試驗(yàn)來確定．即在試沖調(diào)整中確定毛坯的尺寸。
4 結(jié)論
影響沖壓模具壽命的因素很多，從以上分析可以看出從模具設(shè)計(jì)到使用的全過程中，均能提高模具壽命。實(shí)踐證明，合理設(shè)計(jì)模具結(jié)構(gòu)及形狀，采用恰當(dāng)?shù)臎_模制造工藝、熱處理工藝，使模具在正常的條件下工作，均能提高模具的壽命。
參考文獻(xiàn)：
[1]翁其金．冷沖壓技術(shù)[M]．北京：機(jī)械工業(yè)出版社，2007．
[2]劉建超，張寶忠．沖壓模具設(shè)計(jì)與制造[M]．北京：高等教育出版
社。2006．
[3]王孝培．沖壓手冊[M]．北京：機(jī)械工業(yè)出版社，2006．
1 沖壓變形沖壓變形 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。 分離工序是使坯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。其中有以沖孔、落料應(yīng)用最廣。變形工序是使坯料的一部分相對另一部分產(chǎn)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(zhì)上看，沖壓成形就是毛坯的變形區(qū)在外力的作用下產(chǎn)生相應(yīng)的塑性變形，所以變形區(qū)的應(yīng)力狀態(tài)和變形性質(zhì)是決定沖壓成形性質(zhì)的基本因素。因此，根據(jù)變形區(qū)應(yīng)力狀態(tài)和變形特點(diǎn)進(jìn)行的沖壓成形分類，可以把成形性質(zhì)相同的成形方法概括成同一個(gè)類型并進(jìn)行系統(tǒng)化的研究。 絕大多數(shù)沖壓成形時(shí)毛坯變形區(qū)均處于平面應(yīng)力狀態(tài)。通常認(rèn)為在板材表面上不受外力的作用，即使有外力作用，其數(shù)值也是較小的，所以可以認(rèn)為垂直于板面方向的應(yīng)力為零，使板材毛坯產(chǎn)生塑性變形的是作用于板面方向上相互垂直的兩個(gè)主應(yīng)力。由于板厚較小，通常都近似地認(rèn)為這兩個(gè)主應(yīng)力在厚度方向上是均勻分布的?；谶@樣的分析，可以把各種形式?jīng)_壓成形中的毛坯變形區(qū)的受力狀態(tài)與變形特點(diǎn)，在平面應(yīng)力的應(yīng)力坐標(biāo)系中(沖壓應(yīng)力圖)與相應(yīng)的兩向應(yīng)變坐標(biāo)系中(沖壓應(yīng)變圖)以應(yīng)力與應(yīng)變坐標(biāo)決定的位置來表示。也就是說，沖壓應(yīng)力圖與沖壓應(yīng)變圖中的不同位置都代表著不同的受力情況與變形特點(diǎn) (1)沖壓毛坯變形區(qū)受兩向拉應(yīng)力作用時(shí)， 可以分為兩種情況： 即 0t=0和 0，t=0。再這兩種情況下，絕對值最大的應(yīng)力都是拉應(yīng)力。以下對這兩種情況進(jìn)行分析。 1)當(dāng)0且t=0時(shí)， 安全量理論可以寫出如下應(yīng)力與應(yīng)變的關(guān)系式： (1-1) /（-m）=/（-m）=t/（t -m）=k 式中 ，t分別是軸對稱沖壓成形時(shí)的徑向主應(yīng)變、切向主應(yīng)變和厚度方向上的主應(yīng)變； ，t分別是軸對稱沖壓成形時(shí)的徑向主應(yīng)力、切向主應(yīng)力和厚度方向上的主應(yīng)力； m平均應(yīng)力，m=（+t）/3； k常數(shù)。在平面應(yīng)力狀態(tài)，式（11）具有如下形式： 3/（2-）=3/（2-t）=3t/-（t+）=k （12） 因?yàn)?，所以必定有 2-0 與0。這個(gè)結(jié)果表明：在兩向 2 拉應(yīng)力的平面應(yīng)力狀態(tài)時(shí)， 如果絕對值最大拉應(yīng)力是， 則在這個(gè)方向上的主應(yīng)變一定是正應(yīng)變，即是伸長變形。 又因?yàn)?，所以必定有-（t+）0 與t2時(shí)，0；當(dāng) 0。 的變化范圍是 =0 。在雙向等拉力狀態(tài)時(shí)，= ，有式（12）得 =0 及 t 0 且t=0 時(shí)，有式（12）可知：因?yàn)?0，所以 1）定有 2 0 與0。這個(gè)結(jié)果表明：對于兩向拉應(yīng)力的平面應(yīng)力狀態(tài)，當(dāng)?shù)慕^對值最大時(shí)，則在這個(gè)方向上的應(yīng)變一定時(shí)正的，即一定是伸長變形。 又因?yàn)?，所以必定有-（t+）0 與t，0；當(dāng) 0。 的變化范圍是 = =0 。當(dāng)= 時(shí)，=0，也就是在雙向等拉力狀態(tài)下，在兩個(gè)拉應(yīng)力方向上產(chǎn)生數(shù)值相同的伸長變形；在受單向拉應(yīng)力狀態(tài)時(shí)，當(dāng)=0 時(shí)，=- /2，也就是說，在受單向拉應(yīng)力狀態(tài)下其變形性質(zhì)與一般的簡單拉伸是完全一樣的。 這種變形與受力情況，處于沖壓應(yīng)變圖中的 AOC 范圍內(nèi)（見圖 11） ；而在沖壓應(yīng)力圖中則處于 AOH 范圍內(nèi)（見圖 12） 。 上述兩種沖壓情況，僅在最大應(yīng)力的方向上不同，而兩個(gè)應(yīng)力的性質(zhì)以及它們引起的變形都是一樣的。因此，對于各向同性的均質(zhì)材料，這兩種變形是完全相同的。 (1)沖壓毛坯變形區(qū)受兩向壓應(yīng)力的作用，這種變形也分兩種情況分析，即 t=0 和 0，t=0。 1）當(dāng)0 且t=0 時(shí)，有式（12）可知：因?yàn)?，一定有2-0 與0。這個(gè)結(jié)果表明：在兩向壓應(yīng)力的平面應(yīng)力狀態(tài)時(shí)，如果 3 絕對值最大拉應(yīng)力是0，則在這個(gè)方向上的主應(yīng)變一定是負(fù)應(yīng)變，即是壓縮變形。 又因?yàn)? 與t0，即在板料厚度方向上的應(yīng)變是正的，板料增厚。 在方向上的變形取決于與的數(shù)值： 當(dāng)=2時(shí)， =0； 當(dāng)2時(shí)，0；當(dāng) 0。 這時(shí) 的變化范圍是 與 0 之間 。當(dāng)=時(shí)，是雙向等壓力狀態(tài)時(shí)，故有 =0；當(dāng)=0 時(shí)，是受單向壓應(yīng)力狀態(tài)，所以=-/2。這種變形情況處于沖壓應(yīng)變圖中的 EOG 范圍內(nèi)（見圖 11） ；而在沖壓應(yīng)力圖中則處于 COD 范圍內(nèi)（見圖 12） 。 2) 當(dāng) 0 且t=0 時(shí)，有式（12）可知：因?yàn)?0，所以一定有 2 0 與0。這個(gè)結(jié)果表明：對于兩向壓應(yīng)力的平面應(yīng)力狀態(tài)，如果絕對值最大是，則在這個(gè)方向上的應(yīng)變一定時(shí)負(fù)的，即一定是壓縮變形。 又因?yàn)? 與t0，即在板料厚度方向上的應(yīng)變是正的，即為壓縮變形，板厚增大。 在方向上的變形取決于與的數(shù)值： 當(dāng)=2時(shí)， =0； 當(dāng)2，0；當(dāng) 0。 這時(shí)，的數(shù)值只能在= =0 之間變化。當(dāng)= 時(shí)，是雙向等壓力狀態(tài)，所以=0。這種變形與受力情況，處于沖壓應(yīng)變圖中的 GOL 范圍內(nèi)（見圖 11） ；而在沖壓應(yīng)力圖中則處于 DOE 范圍內(nèi)（見圖 12） 。 (1)沖壓毛坯變形區(qū)受兩個(gè)異號應(yīng)力的作用，而且拉應(yīng)力的絕對值大于壓應(yīng)力的絕對 值。這種變形共有兩種情況，分別作如下分析。 1）當(dāng)0，|時(shí)，由式（12）可知：因?yàn)?，|，所以一定有 2-0 及0。這個(gè)結(jié)果表明：在異號的平面應(yīng)力狀態(tài)時(shí)，如果絕對值最大應(yīng)力是拉應(yīng)力，則在這個(gè)絕對值最大的拉應(yīng)力方向上應(yīng)變一定是正應(yīng)變，即是伸長變形。 又因?yàn)?，|，所以必定有00，0， |時(shí)，由式（12）可知：用與前項(xiàng)相同的方法分析可得0。即在異號應(yīng)力作用的平面應(yīng)力狀態(tài)下，如果絕對值最大應(yīng)力是拉應(yīng)力，則在這個(gè)方向上的應(yīng)變是正的，是伸長變形；而在壓應(yīng)力方向上的應(yīng)變是負(fù)的（0， 0， 0，|時(shí)，由式（12）可知：因?yàn)?，|，所以一定有 2- 0 及0，0，必定有 2- 0，即在拉應(yīng)力方向上的應(yīng)變是正的，是伸長變形。 這時(shí)的變化范圍只能在=-與=0 的范圍內(nèi) 。當(dāng)=-時(shí)，00，0， |時(shí)，由式（12）可知：用與前項(xiàng)相同的方法分析可得0， 0， 0,0 AON GOH + + 伸長類 AOC AOH + + 伸長類 雙向受壓 0,0 EOG COD 壓縮類 0,| MON FOG + + 伸長類 | LOM EOF 壓縮類 異號應(yīng)力 0,| COD AOB + + 伸長類 | | DOE BOC 壓縮類 7 變形區(qū)質(zhì)量問題的表現(xiàn)形式 變形程度過大引起變形區(qū)產(chǎn)生破裂現(xiàn)象 壓力作用下失穩(wěn)起皺 成形極限 1主要取決于板材的塑性，與厚度無關(guān) 2可用伸長率及成形極限 DLF 判斷 1主要取決于傳力區(qū)的承載能力 2取決于抗失穩(wěn)能力 3與板厚有關(guān) 變形區(qū)板厚的變化 減薄 增厚 提高成形極限的方法 1改善板材塑性 2使變形均勻化， 降低局部變形程度 3工序間熱處理 1采用多道工序成形 2改變傳力區(qū)與變形區(qū)的力學(xué)關(guān)系 3采用防起皺措施 伸 長 類 成 形脹 形拉 深翻 邊壓 縮 類 成 形壓 縮 類 成 形擴(kuò) 口拉 深脹 形伸 長 類 成 形縮 口縮 口擴(kuò)口+-+ /4 /4翻 邊-+- 圖 13 沖壓應(yīng)變圖 8 沖壓成形極限變形區(qū)的成形極限傳動區(qū)的成形極限伸長類變 形壓縮類變 形強(qiáng) 度抗拉與抗壓縮失衡能力塑 性抗縮頸能 力變形均化與擴(kuò)展能力塑 性抗起皺能 力變形力及其 變 化各向異性 值硬化性能變形抗力化學(xué)成分組 織變形條件硬化性能應(yīng)力狀態(tài)應(yīng)變梯度硬化性能模具狀態(tài)力學(xué)性能值與 值相對厚度化學(xué)成分組 織變形條件 圖 13 體系化研究方法舉例 9 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 form 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 form 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 to 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 it is assumed that the stress perpendicular to the blank surface equal 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 that the two principal stresses distribute uniformly along the thickness direction. Based on this analysis, the stress state and 10 the deformation characteristics of the deformation zone in all kind of stamping forming can be denoted by the point in the coordinates of the plane principal stress(diagram of the stamping stress) and the coordinates of the corresponding plane principal stains (diagram of the stamping strain). The different points in the figures of the stamping stress and strain possess different stress state and deformation characteristics. (1)When the deformation zone of the stamping blank is subjected toplanetensile stresses, it can be divided into two cases, that is 0,t=0and 0,t=0.In both cases, the stress with the maximum absolute value is always a tensile stress. These two cases are analyzed respectively as follows. 2)In the case that 0andt=0, according to the integral theory, the relationships between stresses and strains are: /（-m）=/（-m）=t/（t -m）=k 1.1 where, ，t are the principal strains of the radial, tangential and thickness directions of the axial symmetrical stamping forming; ，and tare the principal stresses of the radial, tangential and thickness directions of the axial symmetrical stamping forming;m is the average stress,m=（+t）/3; k is a constant. In plane stress state, Equation 1.1 3/（2-）=3/（2-t）=3t/-（t+）=k 1.2 Since 0,so 2-0 and 0.It indicates that in plane stress state with two axial tensile stresses, if the tensile stress with the maximum absolute value is , the principal strain in this direction must be positive, that is, the deformation belongs 11 to tensile forming. In addition, because 0，therefore -（t+）0 and t2,0；and when 0. The range of is =0 . In the equibiaxial tensile stress state = ，according to Equation 1.2,=0 and t 0 and t=0, according to Equation 1.2 , 2 0 and 0,This result shows that for the plane stress state with two tensile stresses, when the absoluste value of is the strain in this direction must be positive, that is, it must be in the state of tensile forming. Also because0，therefore -（t+）0 and t,0;and when 0. 12 The range of is = =0 .When =,=0, that is, in equibiaxial tensile stress state, the tensile deformation with the same values occurs in the two tensile stress directions; when =0, =- /2, that is, in uniaxial tensile stress state, the deformation characteristic in this case is the same as that of the ordinary uniaxial tensile. This kind of deformation is in the region AON of the diagram of the stamping strain (see Fig.1.1), and in the region GOH of the diagram of the stamping stress (see Fig.1.2). Between above two cases of stamping deformation, the properties ofand, and the deformation caused by them are the same, only the direction of the maximum stress is different. These two deformations are same for isotropic homogeneous material. (1)When the deformation zone of stamping blank is subjected to two compressive stressesand(t=0), it can also be divided into two cases, which are 0,t=0 and 0,t=0. 1）When 0 and t=0, according to Equation 1.2, 2-0 與 =0.This result shows that in the plane stress state with two compressive stresses, if the stress with the maximum absolute value is 0, the strain in this direction must be negative, that is, in the state of compressive forming. Also because 0 and t0.The strain in the thickness direction of the blankt is positive, and the thickness increases. The deformation condition in the tangential direction depends on the values 13 of and .When =2,=0;when 2,0;and when 0. The range of is 0.When =,it is in equibiaxial tensile stress state, hence=0; when =0,it is in uniaxial tensile stress state, hence =-/2.This kind of deformation condition is in the region EOG of the diagram of the stamping strain (see Fig.1.1), and in the region COD of the diagram of the stamping stress (see Fig.1.2). 2）When 0and t=0, according to Equation 1.2,2- 0 and 0. This result shows that in the plane stress state with two compressive stresses, if the stress with the maximum absolute value is , the strain in this direction must be negative, that is, in the state of compressive forming. Also because 0 and t0.The strain in the thickness direction of the blankt is positive, and the thickness increases. The deformation condition in the radial direction depends on the values of and . When =2, =0; when 2,0; and when 0. The range of is = =0 . When = , it is in equibiaxial tensile stress state, hence =0.This kind of deformation is in the region GOL of the diagram of the stamping strain (see Fig.1.1), and in the region DOE of the diagram of the stamping stress (see Fig.1.2). (3) The deformation zone of the stamping blank is subjected to two stresses with opposite signs, and the absolute value of the tensile stress is larger than that of the compressive stress. There exist two cases to be analyzed as follow: 14 1)When 0, |, according to Equation 1.2, 2-0 and 0.This result shows that in the plane stress state with opposite signs, if the stress with the maximum absolute value is tensile, the strain in the maximum stress direction is positive, that is, in the state of tensile forming. Also because 0, |, therefore =-. When =-, then 0,0,0, |, according to Equation 1.2, by means of the same analysis mentioned above, 0, that is, the deformation zone is in the plane stress state with opposite signs. If the stress with the maximum absolute value is tensile stress , the strain in this direction is positive, that is, in the state of tensile forming. The strain in the radial direction is negative （=-. When =-, then 0, 0, 0,|, according to Equation 1.2, 2- 0 and 0 and 0, therefore 2- 0. The strain in the tensile stress direction is positive, or in the state of tensile forming. The range of is 0=-.When =-, then 0,0,0, |, according to Equation 1.2 and by means of the same analysis mentioned above,=-.When =-, then 0, 0, 0,0 AON GOH + + Tensile AOC AOH + + Tensile Biaxial compressive stress state 0,0 EOG COD Compressive 0,| MON FOG + + Tensile | LOM EOF Compressive State of stress with opposite signs 0,| COD AOB + + Tensile | | DOE BOC Compressive 20 Table 1.2 Comparison between tensile and compressive forming Item Tensile forming Compressive forming Representation of the quality problem in the deformation zone Fracture in the deformation zone due to excessive deformation Instability wrinkle caused by compressive stress Forming limit 3Mainly depends on the plasticity of the material, and is irrelevant to the thickness 4Can be estimated by extensibility or the forming limit DLF 4Mainly depends on the loading capability in the force transferring zone 5Depends on the anti-instability capability 6Has certain relationship to the blank thickness Variation of the blank thickness in the deformation zone Thinning Thickening Methods to improve forming limit 4Improve the plasticity of the material 5Decrease local 4Adopt multi-pass forming process 5Change the mechanics 21 deformation, and increase deformation uniformity 6Adopt an intermediate heat treatment process relationship between the force transferring and deformation zones 6Adopt anti-wrinkle measures Fig.1.1 Diagram of stamping straintensile formingbulgingdeepdrawingflangingcompressive formingcompressive formingexpandingdeep drawingbulgingtensile formingneckingneckingexpanding+-+ /4 /4flanging-+- Fig.1.2 Diagram of stamping stress 22 TensileformingCompressionformingStrengthCapability ofanti-wrinkleunder the tensileand compressivestressesPlasticityCapability ofanti-neckingDeformationuniformity andextension capabilityPlasticityCapability ofanti-wrinkleDeformationforce and itsAnisotropy value of rHardening characteristicsDeformation resistanceChemistry componentStructureDeformation conditionsHardening characteristicsState of stressGradient of strainHardening characteristicsDie shapeMechanical proertyThe value of the n and rRelative thicknessChemistry componentStructureDeformation conditions Fig.1.3 Examples for systematic research methods
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