儀表指針沖壓成形工藝與模具設(shè)計(jì)

喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請(qǐng)放心下載，，有疑問(wèn)咨詢(xún)QQ:414951605或者1304139763 ======================== 喜歡就充值下載吧。。資源目錄里展示的文件全都有，，請(qǐng)放心下載，，有疑問(wèn)咨詢(xún)QQ:414951605或者1304139763 ======================== 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(lèi)。 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(duì)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(lèi)，可以把成形性質(zhì)相同的成形方法概括成同一個(gè)類(lèi)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(lái)表示。也就是說(shuō)，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(duì)值最大的應(yīng)力都是拉應(yīng)力。以下對(duì)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(xiě)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(duì)稱(chēng)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(duì)稱(chēng)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(duì)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(zhǎng)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(duì)于兩向拉應(yīng)力的平面應(yīng)力狀態(tài)，當(dāng)?shù)慕^對(duì)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(zhǎng)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(zhǎng)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(shuō)，在受單向拉應(yīng)力狀態(tài)下其變形性質(zhì)與一般的簡(jiǎn)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(jiàn)圖 11） ；而在沖壓應(yīng)力圖中則處于 AOH 范圍內(nèi)（見(jiàn)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(duì)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(duì)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(jiàn)圖 11） ；而在沖壓應(yīng)力圖中則處于 COD 范圍內(nèi)（見(jiàn)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(duì)于兩向壓應(yīng)力的平面應(yīng)力狀態(tài)，如果絕對(duì)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(jiàn)圖 11） ；而在沖壓應(yīng)力圖中則處于 DOE 范圍內(nèi)（見(jiàn)圖 12） 。 (1)沖壓毛坯變形區(qū)受兩個(gè)異號(hào)應(yīng)力的作用，而且拉應(yīng)力的絕對(duì)值大于壓應(yīng)力的絕對(duì) 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(hào)的平面應(yīng)力狀態(tài)時(shí)，如果絕對(duì)值最大應(yīng)力是拉應(yīng)力，則在這個(gè)絕對(duì)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(zhǎng)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(hào)應(yīng)力作用的平面應(yīng)力狀態(tài)下，如果絕對(duì)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(zhǎng)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(zhǎng)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(zhǎng)類(lèi) AOC AOH + + 伸長(zhǎng)類(lèi) 雙向受壓 0,0 EOG COD 壓縮類(lèi) 0,| MON FOG + + 伸長(zhǎng)類(lèi) | LOM EOF 壓縮類(lèi) 異號(hào)應(yīng)力 0,| COD AOB + + 伸長(zhǎng)類(lèi) | | DOE BOC 壓縮類(lèi) 7 變形區(qū)質(zhì)量問(wèn)題的表現(xiàn)形式 變形程度過(guò)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(wú)關(guān) 2可用伸長(zhǎng)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(zhǎng) 類(lèi) 成 形脹 形拉 深翻 邊壓 縮 類(lèi) 成 形壓 縮 類(lèi) 成 形擴(kuò) 口拉 深脹 形伸 長(zhǎng) 類(lèi) 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(dòng)區(qū)的成形極限伸長(zhǎng)類(lèi)變 形壓縮類(lèi)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(duì)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