注塑機(jī)尾板機(jī)械加工工藝規(guī)程及夾具設(shè)計(jì)【含CAD圖紙、PROE三維】

資源目錄里展示的全都有，所見即所得。下載后全都有,請(qǐng)放心下載。原稿可自行編輯修改=【QQ：401339828 或11970985 有疑問可加】 畢業(yè)設(shè)計(jì)(論文)工作中期檢查表 題目 注塑機(jī)尾板機(jī)械加工工藝規(guī)程及夾具設(shè)計(jì) 學(xué)生姓名 專業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 指 導(dǎo) 教 師 填 寫 學(xué)生開題情況 學(xué)生調(diào)研及查閱文獻(xiàn)情況 畢業(yè)設(shè)計(jì)（論文）原計(jì)劃有無調(diào)整 學(xué)生是否按計(jì)劃執(zhí)行工作進(jìn)度 學(xué)生是否能獨(dú)立完成工作任務(wù) 學(xué)生的英文翻譯情況 學(xué)生每周接受指導(dǎo)的次數(shù)及時(shí)間 畢業(yè)設(shè)計(jì)（論文）過程檢查記錄情況 學(xué)生的工作態(tài)度在相應(yīng)選項(xiàng)劃“√” □認(rèn)真 □一般 □較差 尚存在的問題及采取的措施： 指導(dǎo)教師簽字： 年 月 日 系部意見： 負(fù)責(zé)人簽字： 年 月 日 畢業(yè)設(shè)計(jì)（論文）課題任務(wù)書 系： 機(jī)械工程系 專業(yè)： 機(jī)械制造與自動(dòng)化 指導(dǎo)教師 學(xué)生姓名 課題名稱 注塑機(jī)尾板機(jī)械加工工藝規(guī)程及夾具設(shè)計(jì) 內(nèi)容及任務(wù) 一、設(shè)計(jì)依據(jù)及主要技術(shù)指標(biāo) 1．注塑機(jī)尾板零件工作圖 2．生產(chǎn)綱領(lǐng)：中批生產(chǎn)（年產(chǎn)量為1000件） 3．工作制：?jiǎn)伟嘀乒ぷ? 二、設(shè)計(jì)內(nèi)容 1．分析零件工作圖樣，畫零件三維圖 2．確定毛坯種類、余量、形狀、并繪制毛坯-零件合圖 3．編制機(jī)械加工工藝規(guī)程一套（工序卡、工藝過程卡） 4．指定一主要工序設(shè)計(jì)專用夾具 5．研究設(shè)計(jì)要求，制定夾具定位夾緊方案 6．夾具總裝圖設(shè)計(jì)，畫三維及二維總裝圖 7．夾具精度校核 8．繪制夾具主要零件圖 9．編制設(shè)計(jì)說明書 三、設(shè)計(jì)任務(wù)： 1．工藝規(guī)程（包括工藝過程卡及主要工序工序卡）一套 2．零件--毛坯合圖，零件三維圖 3．三維及二維夾具裝配總圖 4．主要零件零件圖 5．設(shè)計(jì)說明書一份 擬達(dá)到的要求或技術(shù)指標(biāo) 1．零件機(jī)加工工藝路線應(yīng)設(shè)計(jì)多方案（至少２個(gè)），比較后選最佳方案； 2．應(yīng)保證重要表面的加工質(zhì)量與精度； 3．機(jī)床設(shè)備等選用，應(yīng)考慮其經(jīng)濟(jì)性，宜采用通用機(jī)床和專用工夾具； 4．設(shè)計(jì)應(yīng)以獨(dú)立完成為主，圖紙表達(dá)要正確清晰，計(jì)算正確，能借助各種工具書和技術(shù)資料獲得所需的正確數(shù)據(jù)； 5．同一課題組的專用夾具不得一樣； 6．材料牌號(hào)，形位公差，粗糙度，圖紙的標(biāo)題欄及明細(xì)表都要采用新國(guó)標(biāo)； 7．說明書應(yīng)內(nèi)容完整，字跡工整，語言簡(jiǎn)練，文字通順。說明書中應(yīng)重點(diǎn)包括設(shè)計(jì)方案的分析與論證，考慮問題的出發(fā)點(diǎn)和最后選擇的依據(jù)，必要的計(jì)算過程，其他說明等 進(jìn)度安排 起止日期 工作內(nèi)容 備注 畢業(yè)設(shè)計(jì)調(diào)研 畢業(yè)實(shí)習(xí) 畢業(yè)設(shè)計(jì) 答辯時(shí)間 主要參考資料 ［１］ 王先逵.機(jī)械制造工藝學(xué)[M].第二版.北京：機(jī)械工業(yè)出版社 2010.1 ［２］ 聯(lián)合編寫組.機(jī)械設(shè)計(jì)手冊(cè) ［M］. 北京：化學(xué)工業(yè)出版社　1987.12 ［３］ 肖繼德，陳寧平.機(jī)床夾具設(shè)計(jì)［M］. 北京：機(jī)械工業(yè)出版社2005.3 ［４］ 李益民.機(jī)械制造工藝設(shè)計(jì)簡(jiǎn)明手冊(cè)［M］北京：機(jī)械工業(yè)出版社.2005.7 ［５］ 王之櫟.機(jī)械設(shè)計(jì)綜合課程設(shè)計(jì)[M].第二版.北京：機(jī)械工業(yè)出版社 2009.7 ［６］ 孫麗媛.機(jī)械制造工藝及用夾具設(shè)計(jì)指導(dǎo)［M］. 北京：冶金工業(yè)出版社 2002.5 ［７］ 章躍.機(jī)械制造專業(yè)英語［M］. 北京：機(jī)械工業(yè)出版社2002.4 ［８］ 徐灝.機(jī)械設(shè)計(jì)手冊(cè)［M］. 北京：機(jī)械工業(yè)出版社　1991.9 ［９］ 楊叔子.機(jī)械加工工藝師手冊(cè)［M］. 北京：機(jī)械工業(yè)出版社2002.1 ［10］ 朱龍根.機(jī)械零件設(shè)計(jì)手冊(cè)［M］. 北京：機(jī)械工業(yè)出版社2005.8 ［11］ 四川大學(xué)研究所.機(jī)床夾具設(shè)計(jì)圖冊(cè)［M］. 北京：機(jī)械工業(yè)出版社2003.10 ［12］ 艾興、肖詩綱.切削用量簡(jiǎn)明手冊(cè) ［M］.北京：機(jī)械工業(yè)出版社 2004.1 ［16］ 上Internet網(wǎng)查找相關(guān)的設(shè)計(jì)資料，獲得的最新信息與權(quán)威資料 教研室 意見 年 月 日 院(系)主管領(lǐng)導(dǎo)意見 年 月 日 畢業(yè)設(shè)計(jì)(論文)開題報(bào)告 題　　目 注塑機(jī)尾板機(jī)械加工工藝規(guī)程及夾具設(shè)計(jì) 學(xué)生姓名 班級(jí)學(xué)號(hào) 專業(yè) 機(jī)械設(shè)計(jì)及其自動(dòng)化 一、 題目 注塑機(jī)尾板機(jī)械加工工藝規(guī)程及夾具設(shè)計(jì) 二、 意義與目的 注塑機(jī)具有能一次成型外型復(fù)雜、尺寸精確或帶有金屬嵌件的質(zhì)地密致的塑料制品，被廣泛應(yīng)用于國(guó)防、機(jī)電、汽車、交通運(yùn)輸、建材、包裝、農(nóng)業(yè)、文教衛(wèi)生及人們?nèi)粘Ｉ罡鱾€(gè)領(lǐng)域。題目所給的零件是注塑機(jī)尾板，是注塑機(jī)的一個(gè)重要零部件，本次設(shè)計(jì)就是對(duì)注塑機(jī)尾板的加工工藝進(jìn)行設(shè)計(jì)，并至少設(shè)計(jì)出一組專用夾具，用于本零件在加工時(shí)的夾裝。 三、 對(duì)零件的概述 本零件的是與注塑機(jī)的四根拉桿配合，使其沿拉桿方向滑動(dòng)。其主要作用一是安裝液壓缸，二是連接拉桿，形成合模力。零件的四個(gè)角上各有一個(gè)Ф65mm的孔，連接拉桿；在零件的中部水平線上有兩個(gè)Ф40mm的沉頭孔，用來連接液壓缸，中間Ф55mm的孔與活塞桿配合，在底部高30mm的底座安裝在注塑機(jī)的床身上。由于是中批量生產(chǎn)，毛坯采用鑄件，主要有8個(gè)面要進(jìn)行加工，加工后要去除毛刺。 四、 設(shè)計(jì)任務(wù)及要解決的相關(guān)問題 1) 本次設(shè)計(jì)是針對(duì)注塑機(jī)尾板的加工工藝規(guī)程及相對(duì)應(yīng)的專用夾具進(jìn)行設(shè)計(jì)，首先要分析注塑機(jī)尾板的結(jié)構(gòu)，然后進(jìn)行工藝方案設(shè)計(jì)，編寫加工工藝路線，設(shè)計(jì)其中一道工序所使用的專用夾具，最后撰寫設(shè)計(jì)說明書。 2) 設(shè)計(jì)中擬解決的關(guān)鍵問題 ① 本次任務(wù)首要難題是要為零件的加工選好一個(gè)定位基準(zhǔn)。 定位基準(zhǔn)通常應(yīng)優(yōu)先考慮產(chǎn)品設(shè)計(jì)時(shí)的設(shè)計(jì)基準(zhǔn)，并盡可能的選擇加工面作基準(zhǔn)，不采用過多的毛坯面定位。 ② 為零件的加工設(shè)計(jì)一條合適的工藝路線 在初始規(guī)劃時(shí)，應(yīng)當(dāng)設(shè)計(jì)兩個(gè)以上的工藝方案，然后從各個(gè)方面對(duì)這多種方案進(jìn)行比較，并從中選出最好的一個(gè)工藝方案。 ③ 關(guān)于專用夾具的幾個(gè)基本要求 一是要保證工件的加工精度、二是要能提高生產(chǎn)效率、三是其工藝性要好、四是其使用性要好、最后經(jīng)濟(jì)性要好。 五、 設(shè)計(jì)的進(jìn)度安排 根據(jù)自己的實(shí)習(xí)時(shí)間及設(shè)計(jì)任務(wù)的各階段的工作難度，現(xiàn)對(duì)整個(gè)的設(shè)計(jì)計(jì)劃做出如下的進(jìn)度安排。 第2～5周 畢業(yè)調(diào)研及實(shí)習(xí)、搜集設(shè)計(jì)的相關(guān)資料 第6周 設(shè)計(jì)方案的確定 第7～9周 工藝規(guī)程的設(shè)計(jì) 第10～12周 夾具的設(shè)計(jì) 第13～15周 編寫設(shè)計(jì)計(jì)算說明書, 通過指導(dǎo)老師驗(yàn)收，準(zhǔn)備答辯 第16周 畢業(yè)答辯 六、 參考文獻(xiàn) ［１］ 王先逵.機(jī)械制造工藝學(xué)[M].第二版.北京：機(jī)械工業(yè)出版社 2010.1 ［２］ 聯(lián)合編寫組.機(jī)械設(shè)計(jì)手冊(cè) ［M］. 北京：化學(xué)工業(yè)出版社　1987.12 ［３］ 肖繼德，陳寧平.機(jī)床夾具設(shè)計(jì)［M］. 北京：機(jī)械工業(yè)出版社2005.3 ［４］ 李益民.機(jī)械制造工藝設(shè)計(jì)簡(jiǎn)明手冊(cè)［M］北京：機(jī)械工業(yè)出版社.2005.7 ［５］ 王之櫟.機(jī)械設(shè)計(jì)綜合課程設(shè)計(jì)[M].第二版.北京：機(jī)械工業(yè)出版社 2009.7 ［６］ 孫麗媛.機(jī)械制造工藝及用夾具設(shè)計(jì)指導(dǎo)［M］. 北京：冶金工業(yè)出版社 2002.5 ［７］ 章躍.機(jī)械制造專業(yè)英語［M］. 北京：機(jī)械工業(yè)出版社2002.4 ［８］ 徐灝.機(jī)械設(shè)計(jì)手冊(cè)［M］. 北京：機(jī)械工業(yè)出版社　1991.9 ［９］ 楊叔子.機(jī)械加工工藝師手冊(cè)［M］. 北京：機(jī)械工業(yè)出版社2002.1 ［10］ 朱龍根.機(jī)械零件設(shè)計(jì)手冊(cè)［M］. 北京：機(jī)械工業(yè)出版社2005.8 ［11］ 四川大學(xué)研究所.機(jī)床夾具設(shè)計(jì)圖冊(cè)［M］. 北京：機(jī)械工業(yè)出版社2003.10 ［12］ 艾興、肖詩綱.切削用量簡(jiǎn)明手冊(cè) ［M］.北京：機(jī)械工業(yè)出版社 2004.1 ［12］ 上Internet網(wǎng)查找相關(guān)的設(shè)計(jì)資料，獲得的最新信息與權(quán)威資料 指導(dǎo)教師批閱意見 指導(dǎo)教師(簽名)： 年 月 日 注：可另附A4紙 畢業(yè)設(shè)計(jì)（論文）指導(dǎo)教師審閱表 系： 機(jī)械工程系 專業(yè)：機(jī)械設(shè)計(jì)制造及其自動(dòng)化 學(xué)生姓名 學(xué) 號(hào) 班 級(jí) 專 業(yè) 機(jī)械設(shè)計(jì)制造及其自動(dòng)化 指導(dǎo)教師姓名 楊益梅 課題名稱 注塑機(jī)尾板機(jī)械加工工藝規(guī)程及夾具設(shè)計(jì) 評(píng)語：（包括以下方面，①學(xué)習(xí)態(tài)度、工作量完成情況、材料的完整性和規(guī)范性；②檢索和利用文獻(xiàn)能力、計(jì)算機(jī)應(yīng)用能力；③學(xué)術(shù)水平或設(shè)計(jì)水平、綜合運(yùn)用知識(shí)能力和創(chuàng)新能力；） 是否同意參加答辯： 是□ 否□ 指導(dǎo)教師評(píng)定成績(jī) 分值： 指導(dǎo)教師簽字： 年 月 日 機(jī)械加工工藝過程卡片 產(chǎn)品型號(hào) 零件圖號(hào) 產(chǎn)品名稱 注塑機(jī) 零件名稱 注塑機(jī)尾板 共 2 頁 第 1 頁 材 料 牌 號(hào) QT500-7(A) 毛 坯 種 類 鑄件 毛坯外形尺寸 每毛坯件數(shù) 1 每 臺(tái) 件 數(shù) 1 備 注 工 序 號(hào) 工 名 序 稱 工 序 內(nèi) 容 車 間 工 段 設(shè) 備 工 藝 裝 備 工 時(shí) 準(zhǔn)終 單件 1 鑄造 鑄 2 熱處理 退火處 熱 3 劃線 定位 金工 4 銑 粗銑A面 金工 X52K 專用夾具、游標(biāo)卡尺 5 鉆 鉆、鉸孔?55的中心孔 金工 Z37 專用夾具、游標(biāo)卡尺 6 銑 粗銑B面 金工 X63 專用夾具、游標(biāo)卡尺 7 銑 粗銑C面 金工 X63 專用夾具、游標(biāo)卡尺 8 銑 粗銑F面 金工 X52K 專用夾具、游標(biāo)卡尺 9 銑 精銑A面 金工 X52K 專用夾具、游標(biāo)卡尺 10 銑 半精銑B面 金工 X63 專用夾具、游標(biāo)卡尺 11 銑 半精銑C面 金工 X63 專用夾具、游標(biāo)卡尺 12 銑 精銑F面 金工 X52K 專用夾具、游標(biāo)卡尺 13 銑 粗鏜、半精鏜、精鏜（?65、?90）孔口側(cè)角 金工 T612 專用夾具、檢具、游標(biāo)卡尺 14 銑 粗銑D、E面（兩支耳外側(cè)面） 金工 X63 專用夾具、檢具、游標(biāo)卡尺 15 銑 粗銑G、H面（兩支耳內(nèi)側(cè)面） 金工 X63 專用夾具、檢具、游標(biāo)卡尺 16 銑 半精銑D、E面 金工 X63 專用夾具、檢具、游標(biāo)卡尺 17 銑 半精銑G、H面 金工 X63 專用夾具、檢具、游標(biāo)卡尺 設(shè) 計(jì)（日 期） 校 對(duì)（日期） 審 核（日期） 標(biāo)準(zhǔn)化（日期） 會(huì) 簽（日期） 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 湖南工學(xué)院 機(jī)械加工工藝過程卡片 產(chǎn)品型號(hào) 零件圖號(hào) 產(chǎn)品名稱 注塑機(jī) 零件名稱 注塑機(jī)尾板 共 2 頁 第 2 頁 材 料 牌 號(hào) QT500-7(A) 毛 坯 種 類 鑄件 毛坯外形尺寸 每毛坯件數(shù) 1 每 臺(tái) 件 數(shù) 1 備 注 工 序 號(hào) 工 名 序 稱 工 序 內(nèi) 容 車 間 工 段 設(shè) 備 工 藝 裝 備 工 時(shí) 準(zhǔn)終 單件 18 鏜 粗鏜支耳孔4-?60 金工 T612 專用夾具、檢具、游標(biāo)卡尺 19 鉆 鉆、擴(kuò)底板孔（12-M16深35、4-M12深25、2-?13.5深40）， 金工 Z3025 專用夾具、檢具、游標(biāo)卡尺 锪孔2-?40，攻絲 金工 專用夾具、檢具、游標(biāo)卡尺 20 鉆 鉆、擴(kuò)左側(cè)面孔2-M10深10、2-M8深20，攻絲 金工 Z3025 專用夾具、檢具、游標(biāo)卡尺 21 鉆 鉆、擴(kuò)右側(cè)面孔2-M10深10，攻絲 金工 Z3025 專用夾具、檢具、游標(biāo)卡尺 22 鉆 鉆、擴(kuò)后側(cè)面孔M20深50，攻絲 金工 Z3025 專用夾具、檢具、游標(biāo)卡尺 23 銑 粗銑油槽 金工 T612 專用夾具、游標(biāo)卡尺 24 鉆 鉆孔?5深18 金工 Z3025 專用夾具、檢具、游標(biāo)卡尺 25 鉗工 去毛刺 金工 26 送檢 設(shè) 計(jì)（日 期） 校 對(duì)（日期） 審 核（日期） 標(biāo)準(zhǔn)化（日期） 會(huì) 簽（日期） 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 標(biāo)記 處數(shù) 更改文件號(hào) 簽 字 日 期 外 文 翻 譯 故障的分析、尺寸的決定以及凸輪的分析和應(yīng)用 系 部： 機(jī)械工程系 學(xué)生姓名： 指導(dǎo)教師： 職 稱： 專 業(yè)： 班 級(jí)： 學(xué) 號(hào)： Failure Analysis，Dimensional Determination And Analysis，Applications Of Cams Abstract：It is absolutely essential that a design engineer know how and why parts fail so that reliable machines that require minimum maintenance can be designed；Cams are among the most versatile mechanisms available．A cam is a simple two-member device．The input member is the cam itself，while the output member is called the follower．Through the use of cams，a simple input motion can be modified into almost any conceivable output motion that is desired． Key words: failure high-speed cams design properties INTRODUCTION It is absolutely essential that a design engineer know how and why parts fail so that reliable machines that require minimum maintenance can be designed．Sometimes a failure can be serious，such as when a tire blows out on an automobile traveling at high speed．On the other hand，a failure may be no more than a nuisance．An example is the loosening of the radiator hose in an automobile cooling system．The consequence of this latter failure is usually the loss of some radiator coolant，a condition that is readily detected and corrected． The type of load a part absorbs is just as significant as the magnitude．Generally speaking，dynamic loads with direction reversals cause greater difficulty than static loads，and therefore，fatigue strength must be considered．Another concern is whether the material is ductile or brittle．For example，brittle materials are considered to be unacceptable where fatigue is involved． Many people mistakingly interpret the word failure to mean the actual breakage of a part．However，a design engineer must consider a broader understanding of what appreciable deformation occurs．A ductile material，however will deform a large amount prior to rupture．Excessive deformation，without fracture，may cause a machine to fail because the deformed part interferes with a moving second part．Therefore，a part fails(even if it has not physically broken)whenever it no longer fulfills its required function．Sometimes failure may be due to abnormal friction or vibration between two mating parts．Failure also may be due to a phenomenon called creep，which is the plastic flow of a material under load at elevated temperatures．In addition，the actual shape of a part may be responsible for failure．For example，stress concentrations due to sudden changes in contour must be taken into account．Evaluation of stress considerations is especially important when there are dynamic loads with direction reversals and the material is not very ductile． In general，the design engineer must consider all possible modes of failure，which include the following． ——Stress ——Deformation ——Wear ——Corrosion ——Vibration ——Environmental damage ——Loosening of fastening devices The part sizes and shapes selected also must take into account many dimensional factors that produce external load effects，such as geometric discontinuities，residual stresses due to forming of desired contours，and the application of interference fit joints． Cams are among the most versatile mechanisms available．A cam is a simple two-member device．The input member is the cam itself，while the output member is called the follower．Through the use of cams，a simple input motion can be modified into almost any conceivable output motion that is desired．Some of the common applications of cams are ——Camshaft and distributor shaft of automotive engine ——Production machine tools ——Automatic record players ——Printing machines ——Automatic washing machines ——Automatic dishwashers The contour of high-speed cams (cam speed in excess of 1000 rpm) must be determined mathematically．However，the vast majority of cams operate at low speeds(less than 500 rpm) or medium-speed cams can be determined graphically using a large-scale layout．In general，the greater the cam speed and output load，the greater must be the precision with which the cam contour is machined． DESIGN PROPERTIES OF MATERIALS The following design properties of materials are defined as they relate to the tensile test． Static Strength． The strength of a part is the maximum stress that the part can sustain without losing its ability to perform its required function．Thus the static strength may be considered to be approximately equal to the proportional limit，since no plastic deformation takes place and no damage theoretically is done to the material． Stiffness． Stiffness is the deformation-resisting property of a material．The slope of the modulus line and，hence，the modulus of elasticity are measures of the stiffness of a material． Resilience． Resilience is the property of a material that permits it to absorb energy without permanent deformation．The amount of energy absorbed is represented by the area underneath the stress-strain diagram within the elastic region． Toughness． Resilience and toughness are similar properties．However，toughness is the ability to absorb energy without rupture．Thus toughness is represented by the total area underneath the stress-strain diagram， as depicted in Figure 2．8b．Obviously，the toughness and resilience of brittle materials are very low and are approximately equal． Brittleness． A brittle material is one that ruptures before any appreciable plastic deformation takes place．Brittle materials are generally considered undesirable for machine components because they are unable to yield locally at locations of high stress because of geometric stress raisers such as shoulders，holes，notches，or keyways． Ductility． A ductility material exhibits a large amount of plastic deformation prior to rupture．Ductility is measured by the percent of area and percent elongation of a part loaded to rupture．A 5%elongation at rupture is considered to be the dividing line between ductile and brittle materials． Malleability． Malleability is essentially a measure of the compressive ductility of a material and，as such，is an important characteristic of metals that are to be rolled into sheets． Hardness． The hardness of a material is its ability to resist indentation or scratching．Generally speaking，the harder a material，the more brittle it is and，hence，the less resilient．Also，the ultimate strength of a material is roughly proportional to its hardness． Machinability． Machinability is a measure of the relative ease with which a material can be machined．In general，the harder the material，the more difficult it is to machine． COMPRESSION AND SHEAR STATIC STRENGTH In addition to the tensile tests，there are other types of static load testing that provide valuable information． Compression Testing． Most ductile materials have approximately the same properties in compression as in tension．The ultimate strength，however，can not be evaluated for compression．As a ductile specimen flows plastically in compression，the material bulges out，but there is no physical rupture as is the case in tension．Therefore，a ductile material fails in compression as a result of deformation，not stress． Shear Testing． Shafts，bolts，rivets，and welds are located in such a way that shear stresses are produced．A plot of the tensile test．The ultimate shearing strength is defined as the stress at which failure occurs．The ultimate strength in shear，however，does not equal the ultimate strength in tension．For example，in the case of steel，the ultimate shear strength is approximately 75% of the ultimate strength in tension．This difference must be taken into account when shear stresses are encountered in machine components． DYNAMIC LOADS An applied force that does not vary in any manner is called a static or steady load．It is also common practice to consider applied forces that seldom vary to be static loads．The force that is gradually applied during a tensile test is therefore a static load． On the other hand，forces that vary frequently in magnitude and direction are called dynamic loads．Dynamic loads can be subdivided to the following three categories． Varying Load． With varying loads，the magnitude changes，but the direction does not．For example，the load may produce high and low tensile stresses but no compressive stresses． Reversing Load． In this case，both the magnitude and direction change．These load reversals produce alternately varying tensile and compressive stresses that are commonly referred to as stress reversals． Shock Load． This type of load is due to impact．One example is an elevator dropping on a nest of springs at the bottom of a chute．The resulting maximum spring force can be many times greater than the weight of the elevator，The same type of shock load occurs in automobile springs when a tire hits a bump or hole in the road． FATIGUE FAILURE-THE ENDURANCE LIMIT DIAGRAM The test specimen in Figure 2.10a．，after a given number of stress reversals will experience a crack at the outer surface where the stress is greatest．The initial crack starts where the stress exceeds the strength of the grain on which it acts．This is usually where there is a small surface defect，such as a material flaw or a tiny scratch．As the number of cycles increases，the initial crack begins to propagate into a continuous series of cracks all around the periphery of the shaft．The conception of the initial crack is itself a stress concentration that accelerates the crack propagation phenomenon．Once the entire periphery becomes cracked，the cracks start to move toward the center of the shaft．Finally，when the remaining solid inner area becomes small enough，the stress exceeds the ultimate strength and the shaft suddenly breaks．Inspection of the break reveals a very interesting pattern，as shown in Figure 2.13．The outer annular area is relatively smooth because mating cracked surfaces had rubbed against each other．However，the center portion is rough，indicating a sudden rupture similar to that experienced with the fracture of brittle materials． This brings out an interesting fact．When actual machine parts fail as a result of static loads，they normally deform appreciably because of the ductility of the material. Thus many static failures can be avoided by making frequent visual observations and replacing all deformed parts．However，fatigue failures give to warning．Fatigue fail mated that over 90% of broken automobile parts have failed through fatigue． The fatigue strength of a material is its ability to resist the propagation of cracks under stress reversals．Endurance limit is a parameter used to measure the fatigue strength of a material．By definition，the endurance limit is the stress value below which an infinite number of cycles will not cause failure． Let us return our attention to the fatigue testing machine in Figure 2.9．The test is run as follows：A small weight is inserted and the motor is turned on．At failure of the test specimen，the counter registers the number of cycles N，and the corresponding maximum bending stress is calculated from Equation 2.5．The broken specimen is then replaced by an identical one，and an additional weight is inserted to increase the load．A new value of stress is calculated，and the procedure is repeated until failure requires only one complete cycle．A plot is then made of stress versus number of cycles to failure．Figure 2.14a shows the plot，which is called the endurance limit or S-N curve．Since it would take forever to achieve an infinite number of cycles，1 million cycles is used as a reference．Hence the endurance limit can be found from Figure 2.14a by noting that it is the stress level below which the material can sustain 1 million cycles without failure． The relationship depicted in Figure 2.14 is typical for steel，because the curve becomes horizontal as Napproaches a very large number．Thus the endurance limit equals the stress level where the curve approaches a horizontal tangent．Owing to the large number of cycles involved，N is usually plotted on a logarithmic scale，as shown in Figure 2.14b．When this is done，the endurance limit value can be readily detected by the horizontal straight line．For steel，the endurance limit equals approximately 50% of the ultimate strength．However，if the surface finish is not of polished equality，the value of the endurance limit will be lower．For example，for steel parts with a machined surface finish of 63 microinches ，the percentage drops to about 40%．For rough surfaces，the percentage may be as low as 25%． The most common type of fatigue is that due to bending．The next most frequent is torsion failure，whereas fatigue due to axial loads occurs very seldom．Spring materials are usually tested by applying variable shear stresses that alternate from zero to a maximum value，simulating the actual stress patterns． In the case of some nonferrous metals，the fatigue curve does not level off as the number of cycles becomes very large．This continuing toward zero stress means that a large number of stress reversals will cause failure regardless of how small the value of stress is．Such a material is said to have no endurance limit．For most nonferrous metals having an endurance limit，the value is about 25% of the ultimate strength． EFFECTS OF TEMPERATURE ON YIELD STRENGTH AND MODULUS OF ELASTICITY Generally speaking，when stating that a material possesses specified values of properties such as modulus of elasticity and yield strength，it is implied that these values exist at room temperature．At low or elevated temperatures，the properties of materials may be drastically different．For example，many metals are more brittle at low temperatures．In addition，the modulus of elasticity and yield strength deteriorate as the temperature increases．Figure 2.23 shows that the yield strength for mild steel is reduced by about 70% in going from room temperature to 1000oF． Figure 2.24 shows the reduction in the modulus of elasticity E for mild steel as the temperature increases．As can be seen from the graph，a 30% reduction in modulus of elasticity occurs in going from room temperature to 1000oF．In this figure，we also can see that a part loaded below the proportional limit at room temperature can be permanently deformed under the same load at elevated temperatures． CREEP: A PLASTIC PHENOMENON Temperature effects bring us to a phenomenon called creep，which is the increasing plastic deformation of a part under constant load as a function of time．Creep also occurs at room temperature，but the process is so slow that it rarely becomes significant during the expected life of the temperature is raised to 300oC or more，the increasing plastic deformation can become significant within a relatively short period of time．The creep strength of a material is its ability to resist creep，and creep strength data can be obtained by conducting long-time creep tests simulating actual part operating conditions．During the test，the plastic strain is monitored for given material at specified temperatures． Since creep is a plastic deformation phenomenon，the dimensions of a part experiencing creep are permanently altered．Thus，if a part operates with tight clearances，the design engineer must accurately predict the amount of creep that will occur during the life of the machine．Otherwise，problems such binding or interference can occur． Creep also can be a problem in the case where bolts are used to clamp tow parts together at elevated temperatures．The bolts，under tension，will creep as a function of time．Since the deformation is plastic，loss of clamping force will result in an undesirable loosening of the bolted joint．The extent of this particular phenomenon，called relaxation，can be determined by running appropriate creep strength tests． Figure 2.25 shows typical creep curves for three samples of a mild steel part under a constant tensile load．Notice that for the high-temperature case the creep tends to accelerate until the part fails．The time line in the graph (the x-axis) may represent a period of 10 years，the anticipated life of the product． SUMMARY The machine designer must understand the purpose of the static tensile strength test．This test determines a number of mechanical properties of metals that are used in design equations．Such terms as modulus of elasticity，proportional limit，yield strength，ultimate strength，resilience，and ductility define properties that can be determined from the tensile test． Dynamic loads are those which vary in magnitude and direction and may require an investigation of the machine part’s resistance to failure．Stress reversals may require that the allowable design stress be based on the endurance limit of the material rather than on the yield strength or ultimate strength． Stress concentration occurs at locations where a machine part changes size，such as a hole in a flat plate or a sudden change in width of a flat plate or a groove or fillet on a circular shaft．Note that for the case of a hole in a flat or bar，the value of the maximum stress becomes much larger in relation to the average stress as the size of the hole decreases．Methods of reducing the effect of stress concentration usually involve making the shape change more gradual． Machine parts are designed to operate at some allowable stress below the yield strength or ultimate strength．This approach is used to take care of such unknown factors as material property variations and residual stresses produced during manufacture and the fact that the equations used may be approximate rather that exact．The factor of safety is applied to the yield strength or the ultimate strength to determine the allowable stress． Temperature can affect the mechanical properties of metals．Increases in temperature may cause a metal to expand and creep and may reduce its yield strength and its modulus of elasticity．If most metals are not allowed to expand or contract with a change in temperature，then stresses are set up that may be added to the stresses from the load．This phenomenon is useful in assembling parts by means of interference fits．A hub or ring has an inside diameter slightly smaller than the mating shaft or post．The hub is then heated so that it expands enough to slip over the shaft．When it cools，it exerts a pressure on the shaft resulting in a strong frictional force that prevents loosening． 故障的分析、尺寸的決定以及凸輪的分析和應(yīng)用 摘要：作為一名設(shè)計(jì)工程師有必要知道零件如何發(fā)生和為什么會(huì)發(fā)生故障，以便通過進(jìn)行最低限度的維修以保證機(jī)器的可靠性；凸輪是被應(yīng)用的最廣泛的機(jī)械結(jié)構(gòu)之一，是一種僅僅有兩個(gè)組件構(gòu)成的設(shè)備。主動(dòng)件本身就是凸輪，而輸出件被稱為從動(dòng)件。通過使用凸輪，一個(gè)簡(jiǎn)單的輸入動(dòng)作可以被修改成幾乎可以想像得到的任何輸出運(yùn)動(dòng)。 關(guān)鍵詞：故障 高速凸輪 設(shè)計(jì)屬性 前言介紹： 作為一名設(shè)計(jì)工程師有必要知道零件如何發(fā)生和為什么會(huì)發(fā)生故障，以便通過進(jìn)行最低限度的維修以保證機(jī)器的可靠性。有時(shí)一次零件的故障或者失效可能是很嚴(yán)重的一件事情，比如，當(dāng)一輛汽車正在高速行駛的時(shí)候，突然汽車的輪胎發(fā)生爆炸等。另一方面，一個(gè)零件發(fā)生故障也可能只是一件微不足道的小事，只是給你造成了一點(diǎn)小麻煩。一個(gè)例子是在一個(gè)汽車?yán)鋮s系統(tǒng)里的暖氣裝置軟管的松動(dòng)。后者發(fā)生的這次故障造成的結(jié)果通常只不過是一些暖氣裝置里冷卻劑的損失，是一種很容易被發(fā)現(xiàn)并且被改正的情況。 能夠被零件進(jìn)行吸收的載荷是相當(dāng)重要的。一般說來，與靜載重相比較，有兩個(gè)相反方向的動(dòng)載荷將會(huì)引起更大的問題，因此，疲勞強(qiáng)度必須被考慮。另一個(gè)關(guān)鍵是材料是可延展性的還是脆性的。例如，脆的材料被認(rèn)為在存在疲勞的地方是不能夠被使用的。 很多人錯(cuò)誤的把一個(gè)零件發(fā)生故障或者失效理解成這樣就意味著一個(gè)零件遭到了實(shí)際的物理破損。無論如何，一名設(shè)計(jì)工程師必須從一個(gè)更廣泛的范圍來考慮和理解變形是究竟如何發(fā)生的。一種具有延展性的材料，在破裂之前必將發(fā)生很大程度的變形。發(fā)生了過度的變形，但并沒有產(chǎn)生裂縫，也可能會(huì)引起一臺(tái)機(jī)器出毛病，因?yàn)榘l(fā)生畸變的零件會(huì)干擾下一個(gè)零件的移動(dòng)。因此，每當(dāng)它不能夠再履行它要求達(dá)到的性能的時(shí)候，一個(gè)零件就都算是被毀壞了（即使它的表面沒有被損毀）。有時(shí)故障可能是由于兩個(gè)兩個(gè)相互搭配的零件之間的不正常的磨擦或者異常的振動(dòng)引起的。 故障也可能是由一種叫蠕變的現(xiàn)象引起的，這種現(xiàn)象是指金屬在高溫下時(shí)一種材料的塑性流動(dòng)。此外，一個(gè)零件的實(shí)際形狀可能會(huì)引起故障的發(fā)生。例如，應(yīng)力的集中可能就是由于輪廓的突然變化引起的，這一點(diǎn)也需要被考慮到。當(dāng)有用兩個(gè)相反方向的動(dòng)載荷，材料不具有很好的可延展性時(shí)，對(duì)應(yīng)力考慮的評(píng)估就特別重要。 一般說來，設(shè)計(jì)工程師必須考慮故障可能發(fā)生的全部方式，包括如下一些方面： ——壓力 ——變形 ——磨損 ——腐蝕 ——振動(dòng) ——環(huán)境破壞 ——固定設(shè)備松動(dòng) 在選擇零件的大小與形狀的時(shí)候，也必須考慮到一些可能會(huì)產(chǎn)生外部負(fù)載影響的空間因素，例如幾何學(xué)間斷性，為了達(dá)到要求的外形輪廓及使用相關(guān)的連接件，也會(huì)產(chǎn)生相應(yīng)的殘余應(yīng)力。 凸輪是被應(yīng)用的最廣泛的機(jī)械結(jié)構(gòu)之一，是一種僅僅有兩個(gè)組件構(gòu)成的設(shè)備。主動(dòng)件本身就是凸輪，而輸出件被稱為從動(dòng)件。通過使用凸輪，一個(gè)簡(jiǎn)單的輸入動(dòng)作可以被修改成幾乎可以想象得到的任何輸出運(yùn)動(dòng)。常見的一些關(guān)于凸輪應(yīng)用的例子有： ——凸輪軸和汽車發(fā)動(dòng)機(jī)工程的裝配 ——專用機(jī)床 ——自動(dòng)電唱機(jī) ——印刷機(jī) ——自動(dòng)的洗衣機(jī) ——自動(dòng)的洗碗機(jī) 高速凸輪(凸輪超過1000 rpm的速度)的輪廓必須從數(shù)學(xué)意義上來定義。無論如何，大多數(shù)凸輪以低速(少于500 rpm)運(yùn)行而中速的凸輪可以通過一個(gè)大比例的圖形表示出來。一般說來，凸輪的速度和輸出負(fù)載越大，凸輪的輪廓在被床上被加工時(shí)就一定要更加精密。 材料的設(shè)計(jì)屬性 當(dāng)他們與抗拉的試驗(yàn)有關(guān)時(shí)，材料的下列設(shè)計(jì)特性被定義如下。 靜強(qiáng)度：一個(gè)零件的強(qiáng)度是指零件在不會(huì)失去它被要求的能力的前提下能夠承受的最大應(yīng)力。因此靜強(qiáng)度可以被認(rèn)為是大約等于比例極限，從理論上來說，我們可以認(rèn)為在這種情況下，材料沒有發(fā)生塑性變形和物理破壞。 剛度：剛度是指材料抵抗變形的一種屬性。這條斜的模數(shù)線以及彈性模數(shù)是一種衡量材料的剛度的一種方法。 彈性：彈性是指零件能夠吸收能量但并沒有發(fā)生永久變形的一種材料的屬性。吸收的能量的多少可以通過下面彈性區(qū)域內(nèi)的