車床尾座體機(jī)械加工工藝與工裝設(shè)計
車床尾座體機(jī)械加工工藝與工裝設(shè)計,車床,尾座體,機(jī)械,加工,工藝,工裝,設(shè)計
車床尾座體機(jī)加工工藝及工裝設(shè)計
學(xué)生姓名: 曾羅軍 班級:0781051
指導(dǎo)老師:賀紅林
摘要:尾座體是車床上的重要的部件之一,是車床上用以支撐軸類零件車削加工和實施鉆孔的主要車床附件。本文針對某類給定的尾座體進(jìn)行了加工工藝與工裝的設(shè)計,完成了以下工作:
(1) 概述了尾座體的技術(shù)和現(xiàn)狀發(fā)展;
(2) 對尾座體進(jìn)行了工藝分析,并提出了兩種方案進(jìn)行比較;
(3) 編制了尾座體的工藝規(guī)程,完成了其工序卡的設(shè)計;
(4) 針對工藝中的某重要工序,設(shè)計完成了一套銑槽夾具和鏜孔夾具,包括定位元件,夾緊機(jī)構(gòu)、對刀塊、夾具體的設(shè)計并分析了定位誤差。
關(guān)鍵詞:尾座體 工藝 工裝 設(shè)計
指導(dǎo)老師簽名:
Lather tail the craft work of the body
pack a design
Student: ZengLuoJun Grade:0781051
Supervisor: He Honglin
Abstract: stalk spare parts, the car pares to process the main lather enclosure that drills a hole with implementation.
This text aims at a certain the tail body giving certainly carried on to process the design that craft and work pack and completed once work:
(1)All said a tail the technique and present condition development of the body;
(2)Carried on craft analysis to the tail body, and put forward two kinds of projects to carry on a comparison;
(3)Drew up a tail body of craft regulations, completed the design of its work preface card;
(4)Aim at a craft in of some important work preface, designed to complete a set of Xian slot tongs, including fixed position component, clipped tight organization, to the knife piece, clip a concrete design and analyzed a fixed position error margin.
Keywords: tailstock craft clamping design
Signature of supervisor:
畢業(yè)設(shè)計(論文)任務(wù)書
I、畢業(yè)設(shè)計(論文)題目:
車床尾座體機(jī)械加工工藝與工裝設(shè)計
II、畢 業(yè)設(shè)計(論文)使用的原始資料(數(shù)據(jù))及設(shè)計技術(shù)要求:
原始數(shù)據(jù):
(1)機(jī)床尾座體零件工作圖;
(2)生產(chǎn)綱領(lǐng):年產(chǎn)約500件;
(3)零件材料:HT200。
設(shè)計要求:
(1)繪制機(jī)床尾座體零件工作圖;
(2)編制尾座體加工工藝過程卡和工序卡;
(3)針對工藝過程中某重要工序進(jìn)行夾具設(shè)計,繪制夾具裝配圖;
(4)設(shè)計尾座體夾具主要零件圖(至少2張);
(5)撰寫畢業(yè)設(shè)計論文。
III、畢 業(yè)設(shè)計(論文)工作內(nèi)容及完成時間:
1. 查閱文獻(xiàn)資料,撰寫開題報告 1周
2. 相關(guān)外文文獻(xiàn)閱讀與翻譯(6000字符以上) 1周
3. 繪制尾座體的零件工作圖 2周
4. 尾座體工藝規(guī)程設(shè)計 1周
5. 尾座體工序卡的編制 1周
6 工裝夾具設(shè)計 2周
7. 撰寫畢業(yè)論文 2周
8. 畢業(yè)答辯 1周
Ⅳ 、主 要參考資料:
[1]倪森壽.機(jī)械制造工藝與裝備習(xí)題集和課程設(shè)計指導(dǎo)書. 北京:化學(xué)工業(yè)出版社,2003
[2]杜可可.機(jī)械制造技術(shù)基礎(chǔ)課程設(shè)計指導(dǎo). 北京:人民郵電出版社,2007
[3]吳拓. 機(jī)械制造技術(shù)基礎(chǔ). 北京:清華大學(xué)出版社,2007
[4]孫麗媛,雒運強(qiáng),張嘉鈺. 機(jī)械制造工藝及專用夾具.北京:冶金工業(yè)出版社,2002
[5]蘭建設(shè). 機(jī)械制造工藝與夾具. 北京:機(jī)械工業(yè)出版社,2004
[6]鄒青. 機(jī)械制造技術(shù)基礎(chǔ)課程設(shè)計指導(dǎo)教程. 北京機(jī)械工業(yè)出版社,2004
[7]馬賢智. 實用機(jī)械加工手冊. 沈陽:遼寧科技出版禧,2002
[ 8 ] Machine Tools N.chernor 1984.
航空工程系 學(xué)院 機(jī)械設(shè)計制造及其自動化 專業(yè) 0781051 班
學(xué)生(簽名): 曾羅軍
日期: 自 2011 年 3月 1 日至 2011 年 6 月 2 日
指導(dǎo)教師(簽名):
助理指導(dǎo)教師(并指出所負(fù)責(zé)的部分):
機(jī)械設(shè)計 系(室) 主任(簽名):
1 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類型并進(jìn)行系統(tǒng)化的研究。 絕大多數(shù)沖壓成形時毛坯變形區(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 直的兩個主應(yīng)力。由于板厚較小,通常都近似地認(rèn)為這兩個主應(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,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 (1)沖壓毛坯變形區(qū)受兩向拉應(yīng)力作用時,可以分為兩種情況:即 σ γ >σ >0σ t=0 和 σ θ >σ γ >0, σ 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) σ γ >σ θ >0且 σ t=0時,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) ε γ /( σ γ -σ m) =ε θ /( σ θ -σ m) =ε t/( σ t -σ m) =k 式中 ε γ , ε θ , ε t—— 分 別 是 軸對稱沖壓 成 形時 的 徑向 主 應(yīng)變 、切向主 應(yīng) 變 和厚度方向上的主 應(yīng)變 ; σ γ , σ θ , σ t—— 分 別 是 軸對稱沖壓 成 形時 的 徑向 主 應(yīng) 力、切向主 應(yīng) 力和厚度 方向上的主 應(yīng) 力; σ m—— 平均 應(yīng) 力, σ m=( σ γ +σ θ +σ t) /3; k—— 常數(shù) 。在平面 應(yīng) 力 狀態(tài) ,式( 1— 1)具有如下形式: 3ε γ /( 2σ γ -σ θ ) =3ε θ /( 2σ θ -σ t) =3ε t/[-( σ t+σ θ ) ]=k ( 1— 2) 因為 σ γ >σ θ >0,所以必定有 2σ γ -σ θ >0 與 ε θ >0。 這個結(jié) 果表明:在 兩向 2 拉應(yīng) 力的平面 應(yīng) 力 狀態(tài)時 ,如果 絕對 值 最大 拉應(yīng) 力是 σ γ ,則在這個方向上的主 應(yīng)變一定是正應(yīng)變,即是伸長變形。 又因為 σ γ >σ θ >0,所以必定有 -( σ t+σ θ ) <0 與 ε t2 σ θ 時, ε θ <0;當(dāng) σ γ 0。 σ θ 的變化范圍是 σ γ >=σ θ >=0 。在雙向等拉力狀態(tài)時, σ γ =σ θ ,有 式( 1— 2)得 ε γ =ε θ >0 及 ε t σ γ >0 且 σ t=0 時,有式( 1— 2)可知:因為 σ θ >σ γ >0,所以 1) 定有 2σ θ >σ γ >0 與 ε θ >0。這個結(jié)果表明:對于兩向拉應(yīng)力的平面應(yīng)力狀 態(tài),當(dāng) σ θ 的絕對值最大時,則在這個方向上的應(yīng)變一定時正的,即一定是 伸長變形。 又因為 σ γ >σ θ >0,所以必定有 -( σ t+σ θ ) <0 與 ε t σ γ , ε γ <0;當(dāng) σ θ 0。 σ γ 的變化范圍是 σ θ >= σ γ >=0 。當(dāng) σ γ =σ θ 時, ε γ =ε θ >0, 也就是 在 雙向等拉 力 狀態(tài)下 ,在 兩個拉應(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 , 當(dāng) σ γ =0 時, ε γ =-ε θ /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 1— 1);而 在沖壓應(yīng)力圖中則處于 AOH 范圍內(nèi)(見圖 1— 2)。 上述兩種沖壓情況,僅在最大應(yīng)力的方向上不同,而兩個應(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 σ γ <σ θ < σ t=0 和 σ θ <σ γ <0, σ t=0。 1)當(dāng) σ γ <σ θ <0 且 σ t=0 時,有式( 1— 2)可知:因 為 σ γ <σ θ <0,一定有 2σ γ -σ θ <0 與 ε γ <0。 這個結(jié) 果表明:在 兩向壓應(yīng) 力的平面 應(yīng) 力 狀態(tài)時 ,如果 3 絕對 值最大 拉應(yīng) 力是 σ γ <0,則在這個方向上的主應(yīng)變一定是負(fù)應(yīng)變,即是壓 縮變形。 又因為 σ γ <σ θ 0 與 ε t>0,即在板料厚度方 向上的 應(yīng)變 是正的,板料增厚。 在 σ θ 方向上的變形取決于 σ γ 與 σ θ 的數(shù)值:當(dāng) σ γ =2σ θ 時, ε θ =0;當(dāng) σ γ >2 σ θ 時, ε θ <0;當(dāng) σ γ 0。 這時 σ θ 的變化范圍是 σ γ 與 0 之間 。當(dāng) σ γ =σ θ 時,是雙向等 壓 力狀態(tài) 時,故有 ε γ =ε θ <0;當(dāng) σ θ =0 時 ,是受 單 向 壓應(yīng) 力 狀態(tài) ,所以 ε θ =-ε γ /2。 這種變形情況處于沖壓應(yīng)變圖中的 EOG 范圍內(nèi)(見圖 1— 1);而在沖壓應(yīng)力圖 中則處于 COD 范圍內(nèi)(見圖 1— 2)。 2) 當(dāng) σ θ <σ γ <0 且 σ t=0 時,有式( 1— 2)可知:因為 σ θ <σ γ <0,所以 一定有 2σ θ σ γ <0 與 ε θ <0。這個結(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 σ θ ,則在這個方向上的應(yīng)變一定時負(fù)的,即一定是壓 縮變形。 又因為 σ γ <σ θ 0 與 ε t>0,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 σ θ 方向上的變形取決于 σ γ 與 σ θ 的數(shù)值:當(dāng) σ θ =2σ γ 時, ε γ =0;當(dāng) σ θ >2 σ γ , ε γ <0;當(dāng) σ θ 0。 這時, σ γ 的數(shù)值只能在 σ θ <= σ γ <=0 之間變化。當(dāng) σ γ =σ θ 時, 是 雙向 等壓力狀態(tài) ,所以 ε γ =ε θ 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 1 — 1);而在沖壓應(yīng)力圖中則處于 DOE 范圍內(nèi)(見圖 1— 2)。 (1)沖壓毛坯變形區(qū)受兩個異號應(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) σ γ >0, σ θ |σ θ |時,由式( 1— 2)可知:因 為 σ γ >0, σ θ |σ θ |,所以一定 有 2σ γ -σ θ >0 及 ε γ >0。 這個結(jié) 果表明:在異 號 的 平面 應(yīng) 力 狀態(tài)時 ,如果 絕對 值最大 應(yīng) 力是 拉應(yīng) 力 ,則在這個絕對值最大的拉應(yīng) 力方向上應(yīng)變一定是正應(yīng)變,即是伸長變形。 又因為 σ γ >0, σ θ |σ θ |,所以必定有 ε θ 0ε θ 0, ε θ 0, σ γ |σ γ |時,由式( 1— 2)可知: 用與前 項相同的方法分析可得 ε θ >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 σ θ ,則在這個方向上的應(yīng)變是正的,是伸長變形;而在 壓應(yīng)力 σ γ 方向上的應(yīng)變是負(fù)的( ε γ 0, ε γ 0, ε γ 0, σ θ |σ γ |時,由式( 1— 2)可知:因 為 σ γ >0, σ θ |σ γ |,所以一定有 2σ θ - σ γ <0 及 ε θ 0, σ θ <0,必定有 2σ γ - σ θ 0, 即在 拉應(yīng) 力方向上 的 應(yīng)變 是正的, 是伸長變形。 這時 σ γ 的變化范圍只能在 σ γ =-σ θ 與 σ γ =0 的范圍內(nèi) 。當(dāng) σ γ =-σ θ 時, ε γ >0ε θ 0, ε θ 0, σ γ |σ θ |時,由式( 1— 2)可知: 用與前 項相同的方法分析可得 ε γ 0, ε γ 0, ε γ 0,σ γ >0 σ γ > σ θ AON GOH + + 伸長類 σ θ >σ γ AOC AOH + + 伸長類 雙向受壓 σ θ <0,σ γ <0 σ γ < σ θ EOG COD — — 壓縮類 σ θ 0,σ θ |σ θ | MON FOG + + 伸長 類 |σ θ |>|σ γ | LOM EOF — — 壓縮類 異號應(yīng)力 σ θ >0,σ γ |σ γ | COD AOB + + 伸長類 |σ γ |> |σ θ | 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 + ε γ - ε γ - ε θ + ε θ π /4 π /4 翻 邊 - σ γ + σ θ + σ γ - σ θ 圖 1— 3 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 1— 3 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 princ ipal 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 σγ>σθ>0,σt=0andσθ>σγ >0,σt=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 σγ>σθ>0andσt=0, according to the integral theory, the relationships between stresses and strains are: εγ/( σγ-σm) =εθ/( σθ-σm) =εt/( σt -σm) =k 1.1 where, εγ, εθ, εt are the principal strains of the radial, tangential and thickness directions of the axial symmetrical stamping forming; σγ, σθand σtare the principal stresses of the radial, tangential and thickness directions of the axial symmetrical stamping forming;σm is the average stress,σm=( σγ+σθ+σt) /3; k is a constant. In plane stress state, Equation 1.1 3εγ/( 2σγ-σθ) =3εθ/( 2σθ-σt) =3εt/[-( σt+σθ) ]=k 1.2 Since σγ>σθ>0,so 2σγ-σθ>0 and εθ>0.It indicates that in plane stress state with two axial tensile stresses, if the tensile stress with the maximum absolute value is σγ, the principal strain in this direction must be positive, that is, the deformation belongs 11 to tensile forming. In addition, because σγ>σθ>0, therefore -( σt+σθ) <0 and εt2σθ,εθ<0; and when σγ0. The range of σθ is σγ>=σθ>=0 . In the equibiaxial tensile stress state σγ=σθ , according to Equation 1.2,εγ=εθ>0 and εt σγ >0 and σt=0, according to Equation 1.2 , 2σθ>σγ >0 and εθ>0,This result shows that for the plane stress state with two tensile stresses, when the absoluste value of σθ is the strain in this direction must be positive, that is, it must be in the state of tensile forming. Also becauseσγ>σθ>0, therefore -( σt+σθ) <0 and εtσγ,εγ<0;and when σθ0. 12 The range of σγ is σθ>= σγ>=0 .When σγ=σθ,εγ=εθ>0, that is, in equibiaxial tensile stress state, the tensile deformation with the same values occurs in the two tensile stress directions; when σγ=0, εγ=-εθ /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 ofσθandσγ, 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 stressesσγandσθ(σt=0), it can also be divided into two cases, which are σγ<σθ<0,σt=0 and σθ<σγ <0,σt=0. 1) When σγ<σθ<0 and σt=0, according to Equation 1.2, 2σγ-σθ<0 與 εγ=0.This result shows that in the plane stress state with two compressive stresses, if the stress with the maximum absolute value is σγ<0, the strain in this direction must be negative, that is, in the state of compressive forming. Also because σγ<σθ0 and εt>0.The strain in the thickness direction of the blankεt is positive, and the thickness increases. The deformation condition in the tangential direction depends on the values 13 ofσγ and σθ.When σγ=2σθ,εθ=0;when σγ>2σθ,εθ<0;and when σγ0. The range of σθ is σγ<σθ<0.When σγ=σθ,it is in equibiaxial tensile stress state, henceεγ=εθ<0; when σθ=0,it is in uniaxial tensile stress state, hence εθ=-εγ/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 σθ<σγ <0and σt=0, according to Equation 1.2,2σθ-σγ <0 and εθ<0. This result shows that in the plane stress state with two compressive stresses, if the stress with the maximum absolute value is σθ, the strain in this direction must be negative, that is, in the state of compressive forming. Also becauseσθ<σγ 0 and εt>0.The strain in the thickness direction of the blankεt is positive, and the thickness increases. The deformation condition in the radial direction depends on the values ofσγ and σθ. When σθ=2σγ, εγ=0; when σθ>2σγ,εγ<0; and when σθ0. The range of σγ is σθ<= σγ<=0 . When σγ=σθ , it is in equibiaxial tensile stress state, hence εγ=εθ0.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 σγ>0, σθ|σθ|, according to Equation 1.2, 2σγ-σθ>0 and εγ>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 σγ>0, σθ|σθ|, therefore εθ=σθ>=-σγ. When σθ=-σγ, then εγ>0,εθ0,εθ0, σγ |σγ|, according to Equation 1.2, by means of the same analysis mentioned above, εθ>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 σθ, the strain in this direction is positive, that is, in the state of tensile forming. The strain in the radial direction is negative ( εγ=σγ>=-σθ. When σγ=-σθ, then εθ>0,εγ 0,εγ 0,σθ|σγ|, according to Equation 1.2, 2σθ- σγ<0 and εθ0 and σθ<0, therefore 2σγ- σθ0. The strain in the tensile stress direction is positive, or in the state of tensile forming. The range of σγis 0>=σγ>=-σθ.When σγ=-σθ, then εγ>0,εθ0,εθ0, σγ |σθ|, according to Equation 1.2 and by means of the same analysis mentioned above,εγ=σθ>=-σγ.When σθ=-σγ, then εθ>0,εγ 0,εγ 0,σγ>0 σγ> σθ AON GOH + + Tensile σθ>σγ AOC AOH + + Tensile Biaxial compressive stress state σθ<0,σγ<0 σγ< σθ EOG COD — — Compress ive σθ0,σθ|σθ| MON FOG + + Tensile |σθ|>|σγ| LOM EOF — — Compress ive State of stress with opposite signs σθ>0,σγ|σγ| COD AOB + + Tensile |σγ|> |σθ| DOE BOC — — Compress ive 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 3. Mainly depends on the plasticity of the material, and is irrelevant to the thickness 4. Can be estimated by extensibility or the forming limit DLF 4. Mainly depends on the loading capability in the force transferring zone 5. Depends on the anti-instability capability 6. Has certain relationship to the blank thickness Variation of the blank thickness in the deformation zone Thinning Thickening Methods to improve forming limit 4. Improve the plasticity of the material 5. Decrease local 4. Adopt multi-pass forming process 5. Change the mechanics 21 deformation, and increase deformation uniformity 6. Adopt an intermediate heat treatment process relationship between the force transferring and deformation zones 6. Adopt anti-wrinkle measures Fig.1.1 Diagram of stamping strain tensile forming bulging deep drawing flanging compressive forming compressive forming expanding deep drawing bulging tensile forming necking necking expanding + ε γ - ε γ - ε θ + ε θ π /4 π /4 flanging - σ γ + σ θ + σ γ - σ θ Fig.1.2 Diagram of stamping stress 22 Ten sile for ming Com pres sion for ming St re ngth Cap abil ity of an ti -w rinkle und er t he t ensi le and com pres sive st re sses Plasticity Cap abil ity of an ti -n ecking Def orma tion uniformit y an d ex te nsion ca pa bility Pl as ticity Cap abil ity of an ti -w rinkle Def orma tion for ce a nd i ts Ani sotr opy valu e of r Har deni ng c hara cter isti cs Deformation r es is ta nc e Che mist ry c ompo nent Str uctu re Deformation c on di ti on s Har deni ng c hara cter isti cs Sta te o f st ress Gradient of s tr ai n Har deni ng c hara cter isti cs Die sha pe Mechanical pr oe rt y The value of t he n a nd r Relative th ic kn es s Che mist ry c ompo nent Str uctu re Deformation c on di ti on s Fig.1.3 Examples for systematic research methods
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