星輪行星輪可爬樓梯式輪椅車設(shè)計(jì)含開(kāi)題及18張CAD圖
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機(jī)械設(shè)計(jì)理論
機(jī)械設(shè)計(jì)是一門(mén)通過(guò)設(shè)計(jì)新產(chǎn)品或者改進(jìn)老產(chǎn)品來(lái)滿足人類需求的應(yīng)用技術(shù)科學(xué)。它涉及工程技術(shù)的各個(gè)領(lǐng)域，主要研究產(chǎn)品的尺寸、形狀和詳細(xì)結(jié)構(gòu)的基本構(gòu)思，還要研究產(chǎn)品在制造、銷售和使用等方面的問(wèn)題。
進(jìn)行各種機(jī)械設(shè)計(jì)工作的人員通常被稱為設(shè)計(jì)人員或者機(jī)械設(shè)計(jì)工程師。機(jī)械設(shè)計(jì)是一項(xiàng)創(chuàng)造性的工作。設(shè)計(jì)工程師不僅在工作上要有創(chuàng)造性，還必須在機(jī)械制圖、運(yùn)動(dòng)學(xué)、工程材料、材料力學(xué)和機(jī)械制造工藝學(xué)等方面具有深厚的基礎(chǔ)知識(shí)。
如前所訴，機(jī)械設(shè)計(jì)的目的是生產(chǎn)能夠滿足人類需求的產(chǎn)品。發(fā)明、發(fā)現(xiàn)和科技知識(shí)本身并不一定能給人類帶來(lái)好處，只有當(dāng)它們被應(yīng)用在產(chǎn)品上才能產(chǎn)生效益。因而，應(yīng)該認(rèn)識(shí)到在一個(gè)特定的產(chǎn)品進(jìn)行設(shè)計(jì)之前，必須先確定人們是否需要這種產(chǎn)品。
應(yīng)當(dāng)把機(jī)械設(shè)計(jì)看成是機(jī)械設(shè)計(jì)人員運(yùn)用創(chuàng)造性的才能進(jìn)行產(chǎn)品設(shè)計(jì)、系統(tǒng)分析和制定產(chǎn)品的制造工藝學(xué)的一個(gè)良機(jī)。掌握工程基礎(chǔ)知識(shí)要比熟記一些數(shù)據(jù)和公式更為重要。僅僅使用數(shù)據(jù)和公式是不足以在一個(gè)好的設(shè)計(jì)中做出所需的全部決定的。另一方面，應(yīng)該認(rèn)真精確的進(jìn)行所有運(yùn)算。例如，即使將一個(gè)小數(shù)點(diǎn)的位置放錯(cuò)，也會(huì)使正確的設(shè)計(jì)變成錯(cuò)誤的。
一個(gè)好的設(shè)計(jì)人員應(yīng)該勇于提出新的想法，而且愿意承擔(dān)一定的風(fēng)險(xiǎn)，當(dāng)新的方法不適用時(shí)，就使用原來(lái)的方法。因此，設(shè)計(jì)人員必須要有耐心，因?yàn)?所花費(fèi)的時(shí)間和努力并不能保證帶來(lái)成功。一個(gè)全新的設(shè)計(jì)，要求屏棄許多陳舊的，為人們所熟知的方法。由于許多人墨守成規(guī)，這樣做并不是一件容易的事。一位機(jī)械設(shè)計(jì)師應(yīng)該不斷地探索改進(jìn)現(xiàn)有的產(chǎn)品的方法，在此過(guò)程中應(yīng)該認(rèn)真選擇原有的、經(jīng)過(guò)驗(yàn)證的設(shè)計(jì)原理，將其與未經(jīng)過(guò)驗(yàn)證的新觀念結(jié)合起來(lái)。
新設(shè)計(jì)本身會(huì)有許多缺陷和未能預(yù)料的問(wèn)題發(fā)生，只有當(dāng)這些缺陷和問(wèn)題被解決之后，才能體現(xiàn)出新產(chǎn)品的優(yōu)越性。因此，一個(gè)性能優(yōu)越的產(chǎn)品誕生的同時(shí)，也伴隨著較高的風(fēng)險(xiǎn)。應(yīng)該強(qiáng)調(diào)的是，如果設(shè)計(jì)本身不要求采用全新的方法，就沒(méi)有必要僅僅為了變革的目的而采用新方法。
在設(shè)計(jì)的初始階段，應(yīng)該允許設(shè)計(jì)人員充分發(fā)揮創(chuàng)造性，不受各種約束。即使產(chǎn)生了許多不切實(shí)際的想法，也會(huì)在設(shè)計(jì)的早期，即繪制圖紙之前被改正掉。只有這樣，才不致于堵塞創(chuàng)新的思路。通常，要提出幾套設(shè)計(jì)方案，然后加以比較。很有可能在最后選定的方案中，采用了某些未被接受的方案中的一些想法。
心理學(xué)家經(jīng)常談?wù)撊绾问谷藗冞m應(yīng)他們所操作的機(jī)器。設(shè)計(jì)人員的基本職責(zé)是努力使機(jī)器來(lái)適應(yīng)人們。這并不是一項(xiàng)容易的工作，因?yàn)閷?shí)際上并不存在著一個(gè)對(duì)所有人來(lái)說(shuō)都是最優(yōu)的操作范圍和操作過(guò)程。
另一個(gè)重要問(wèn)題，設(shè)計(jì)工程師必須能夠同其他有關(guān)人員進(jìn)行交流和磋商。在開(kāi)始階段，設(shè)計(jì)人員必須就初步設(shè)計(jì)同管理人員進(jìn)行交流和磋商，并得到批準(zhǔn)。這一般是通過(guò)口頭討論，草圖和文字材料進(jìn)行的。為了進(jìn)行有效的交流 ，需要解決下列問(wèn)題：
（1） 所設(shè)計(jì)的這個(gè)產(chǎn)品是否真正為人們所需要？
（2） 此產(chǎn)品與其他公司的現(xiàn)有同類產(chǎn)品相比有無(wú)競(jìng)爭(zhēng)能力？
（3） 生產(chǎn)這種產(chǎn)品是否經(jīng)濟(jì)？
（4） 產(chǎn)品的維修是否方便？
（5） 產(chǎn)品有無(wú)銷路？是否可以盈利？
只有時(shí)間能對(duì)上述問(wèn)題給出正確答案。但是， 產(chǎn)品的設(shè)計(jì)、制造和銷售只能在對(duì)上述問(wèn)題的初步肯定答案的基礎(chǔ)上進(jìn)行。設(shè)計(jì)工程師還應(yīng)該通過(guò)零件圖和裝配圖，與制造部門(mén)一起對(duì)最終設(shè)計(jì)方案進(jìn)行磋商。
通常 ，在制造過(guò)程中會(huì)出現(xiàn)某個(gè)問(wèn)題?？赡軙?huì)要求對(duì)某個(gè)零件尺寸或公差作一些更改，使零件的生產(chǎn)變得容易。但是，工程上的更改必須要經(jīng)過(guò)設(shè)計(jì)人員批準(zhǔn)，以保證不會(huì)損傷產(chǎn)品的功能。有時(shí)，在產(chǎn)品的裝配時(shí)或者裝箱外運(yùn)前的試驗(yàn)中才發(fā)現(xiàn)設(shè)計(jì)中的某種缺陷。這些事例恰好說(shuō)明了設(shè)計(jì)是一個(gè)動(dòng)態(tài)過(guò)程?？偸谴嬖谥玫姆椒▉?lái)完成設(shè)計(jì)工作，設(shè)計(jì)人員應(yīng)該不斷努力，尋找這些更好的方法。
近些年來(lái)，工程材料的選擇已經(jīng)顯得重要。此外，選擇過(guò)程應(yīng)該是一個(gè)對(duì)材料的連續(xù)不斷的重新評(píng)價(jià)過(guò)程。新材料不斷出現(xiàn)，而一些原有的材料的能夠獲得的數(shù)量可能會(huì)減少。環(huán)境污染、材料的回收利用、工人的健康及安全等方面經(jīng)常會(huì)對(duì)材料選擇附加新的限制條件。為了減輕重量或者節(jié)約能源，可能會(huì)要求使用不同的材料。來(lái)自國(guó)內(nèi)和國(guó)際競(jìng)爭(zhēng)、對(duì)產(chǎn)品維修保養(yǎng)方便性要求的提高和顧客的反饋等方面的壓力，都會(huì)促使人們對(duì)材料進(jìn)行重新評(píng)價(jià)。由于材料選用不當(dāng)造成的產(chǎn)品責(zé)任訴訟，已經(jīng)產(chǎn)生了深刻的影響。此外，材料與材料加工之間的相互依賴關(guān)系已經(jīng)被人們認(rèn)識(shí)得更清楚。因此，為了能在合理的成本和確保質(zhì)量的前提下獲得滿意的結(jié)果，設(shè)計(jì)工程師的制造工程師都必須認(rèn)真仔細(xì)地選擇、確定和使用材料。
制造任何產(chǎn)品的第一步工作都是設(shè)計(jì)。設(shè)計(jì)通常可以分為幾個(gè)明確的階段：（a）初步設(shè)計(jì)；（b）功能設(shè)計(jì)；（c）生產(chǎn)設(shè)計(jì)。在初步設(shè)計(jì)階段，設(shè)計(jì)者著重考慮產(chǎn)品應(yīng)該具有的功能。通常要設(shè)想和考慮幾個(gè)方案，然后決定這種思想是否可行；如果可行，則應(yīng)該對(duì)其中一個(gè)或幾個(gè)方案作進(jìn)一步的改進(jìn)。在此階段，關(guān)于材料選擇唯一要考慮的問(wèn)題是：是否有性能符合要求的材料可供選擇；如果沒(méi)有的話，是否有較大的把握在成本和時(shí)間都允許的限度內(nèi)研制出一種新材料。
在功能設(shè)計(jì)和工程設(shè)計(jì)階段，要做出一個(gè)切實(shí)可行的設(shè)計(jì)。在這個(gè)階段要繪制出相當(dāng)完整的圖紙，選擇并確定各種零件的材料。通常要制造出樣機(jī)或者實(shí)物模型，并對(duì)其進(jìn)行試驗(yàn)，評(píng)價(jià)產(chǎn)品的功能、可靠性、外觀和維修保養(yǎng)性等。雖然這種試驗(yàn)可能會(huì)表明，在產(chǎn)品進(jìn)入到生產(chǎn)階段之前，應(yīng)該更換某些材料，但是，絕對(duì)不能將這一點(diǎn)作為不認(rèn)真選擇材料的借口。應(yīng)該結(jié)合產(chǎn)品的功能，認(rèn)真仔細(xì)地考慮產(chǎn)品的外觀、成本和可靠性。一個(gè)很有成就的公司在制造所有的樣機(jī)時(shí)，所選用的材料應(yīng)該和其生產(chǎn)中使用的材料相同，并盡可能使用同樣的制造技術(shù)。這樣對(duì)公司是很有好處的。功能完備的樣機(jī)如果不能根據(jù)預(yù)期的銷售量經(jīng)濟(jì)地制造出來(lái)，或者是樣機(jī)與正式生產(chǎn)的裝置在質(zhì)量和可靠性方面有很大不同，則這種樣機(jī)就沒(méi)有多大的價(jià)值。設(shè)計(jì)工程師最好能在這一階段完全完成材料的分析、選擇和確定工作，而不是將其留到生產(chǎn)設(shè)計(jì)階段去做。因?yàn)?，在生產(chǎn)設(shè)計(jì)階段材料的更換是由其他人進(jìn)行的，這些人對(duì)產(chǎn)品的所有功能的了解不如設(shè)計(jì)工程師。
在生產(chǎn)設(shè)計(jì)階段中，與材料有關(guān)的主要問(wèn)題是應(yīng)該把材料完全確定下來(lái)，使它們與現(xiàn)有的設(shè)備相適應(yīng)，能夠利用現(xiàn)有設(shè)備經(jīng)濟(jì)地進(jìn)行加工，而且材料的數(shù)量能夠比較容易保證供應(yīng)。
在制造過(guò)程中，不可避免地會(huì)出現(xiàn)對(duì)使用中的材料做一些更改的情況。經(jīng)驗(yàn)表明，可采用某些便宜材料作為替代品。然而，在大多數(shù)情況下，在進(jìn)行生產(chǎn)以后改換材料要比在開(kāi)始生產(chǎn)前改換材料所花費(fèi)的代價(jià)要高。在設(shè)計(jì)階段做好材料選擇工作，可以避免多數(shù)這樣的情況。在生產(chǎn)制造開(kāi)始后出現(xiàn)了可供使用的新材料是更換材料的最常見(jiàn)的原因。當(dāng)然，這些新材料可能降低成本、改進(jìn)產(chǎn)品的性能。但是，必須對(duì)新材料進(jìn)行認(rèn)真的評(píng)價(jià)，以確保其所有性能都滿足要求。應(yīng)當(dāng)記住，新材料的性能和可靠性很少像現(xiàn)有材料那樣為人們所了解。大部分的產(chǎn)品失效和產(chǎn)品責(zé)任事故案件是由于在選用新材料作為替代材料之前，沒(méi)有真正了解它們的長(zhǎng)期使用性能而引起的。
產(chǎn)品的責(zé)任訴訟迫使設(shè)計(jì)人員和公司在選擇材料時(shí)，采用最好的程序。在材料過(guò)程中，五個(gè)最常見(jiàn)的問(wèn)題為：（a）不了解或者不會(huì)使用關(guān)于材料應(yīng)用方面的最新最好的信息資料；(b)未能預(yù)見(jiàn)和考慮擦黑年品可能的合理用途（如有可能，設(shè)計(jì)人員還應(yīng)進(jìn)一步預(yù)測(cè)和考慮由于產(chǎn)品使用方法不當(dāng)造成的后果。在近年來(lái)的許多產(chǎn)品責(zé)任訴訟案件中，由于錯(cuò)誤地使用產(chǎn)品而受到傷害的原告控告生產(chǎn)廠家，并且贏得判決）；(c)所使用的材料的數(shù)據(jù)不全或是有些數(shù)據(jù)不確定，尤其是當(dāng)其長(zhǎng)期性能數(shù)據(jù)是如此的時(shí)候；(d)質(zhì)量控制方法不適當(dāng)和未經(jīng)驗(yàn)證；(e)由一些完全不稱職的人員選擇材料。
通過(guò)對(duì)上述五個(gè)問(wèn)題的分析，可以得出這些問(wèn)題是沒(méi)有充分理由存在的結(jié)論。對(duì)這些問(wèn)題的研究分析可以為避免這些問(wèn)題的出現(xiàn)指明方向。盡管采用最好的材料選擇方法也不能避免發(fā)生產(chǎn)品責(zé)任訴訟，設(shè)計(jì)人員和工業(yè)界按照適當(dāng)?shù)某绦蜻M(jìn)行材料選擇，可以大大減少訴訟的數(shù)量。
從以上的討論可以看出，選擇材料的人們應(yīng)該對(duì)材料的性質(zhì)，特點(diǎn)和加工方法有一個(gè)全面而基本的了解。
加工基礎(chǔ)
作為產(chǎn)生形狀的一種加工方法，機(jī)械加工是所有制造過(guò)程中最普遍使用的而且是最重要的方法。機(jī)械加工過(guò)程是一個(gè)產(chǎn)生形狀的過(guò)程，在這過(guò)程中，驅(qū)動(dòng)裝置使工件上的一些材料以切屑的形式被去除。盡管在某些場(chǎng)合，工件無(wú)承受情況下，使用移動(dòng)式裝備來(lái)實(shí)現(xiàn)加工，但大多數(shù)的機(jī)械加工是通過(guò)既支承工件又支承刀具的裝備來(lái)完成。
機(jī)械加工在知道過(guò)程中具備兩方面。小批生產(chǎn)低費(fèi)用。對(duì)于鑄造、鍛造和壓力加工，每一個(gè)要生產(chǎn)的具體工件形狀，即使是一個(gè)零件，幾乎都要花費(fèi)高額的加工費(fèi)用?？亢附觼?lái)產(chǎn)生的結(jié)構(gòu)形狀，在很大程度上取決于有效的原材料的形式。一般來(lái)說(shuō)，通過(guò)利用貴重設(shè)備而又無(wú)需特種加工條件下，幾乎可以以任何種類原材料開(kāi)始，借助機(jī)械加工把原材料加工成任意所需要的結(jié)構(gòu)形狀，只要外部尺寸足夠大，那都是可能的。因此對(duì)于生產(chǎn)一個(gè)零件，甚至當(dāng)零件結(jié)構(gòu)及要生產(chǎn)的批量大小上按原來(lái)都適于用鑄造、鍛造或者壓力加工來(lái)生產(chǎn)的，但通常寧可選擇機(jī)械加工。
嚴(yán)密的精度和良好的表面光潔度，機(jī)械加工的第二方面用途是建立在高精度和可能的表面光潔度基礎(chǔ)上。許多零件，如果用別的其他方法來(lái)生產(chǎn)屬于大批量生產(chǎn)的話，那么在機(jī)械加工中則是屬于低公差且又能滿足要求的小批量生產(chǎn)了。另方面，許多零件靠較粗的生產(chǎn)加工工藝提高其一般表面形狀，而僅僅是在需要高精度的且選擇過(guò)的表面才進(jìn)行機(jī)械加工。例如內(nèi)螺紋，除了機(jī)械加工之外，幾乎沒(méi)有別的加工方法能進(jìn)行加工。又如已鍛工件上的小孔加工，也是被鍛后緊接著進(jìn)行機(jī)械加工才完成的。
基本的機(jī)械加工參數(shù)
切削中工件與刀具的基本關(guān)系是以以下四個(gè)要素來(lái)充分描述的：刀具的幾何形狀，切削速度，進(jìn)給速度，和吃刀深度。
切削刀具必須用一種合適的材料來(lái)制造，它必須是強(qiáng)固、韌性好、堅(jiān)硬而且耐磨的。刀具的幾何形狀——以刀尖平面和刀具角為特征——對(duì)于每一種切削工藝都必須是正確的。
切削速度是切削刃通過(guò)工件表面的速率，它是以每分鐘英寸來(lái)表示。為了有效地加工，切削速度高低必須適應(yīng)特定的工件——刀具配合。一般來(lái)說(shuō)，工件材料越硬，速度越低。
進(jìn)給速度是刀具切進(jìn)工件的速度。若工件或刀具作旋轉(zhuǎn)運(yùn)動(dòng)，進(jìn)給量是以每轉(zhuǎn)轉(zhuǎn)過(guò)的英寸數(shù)目來(lái)度量的。當(dāng)?shù)毒呋蚬ぜ魍鶑?fù)運(yùn)動(dòng)時(shí)，進(jìn)給量是以每一行程走過(guò)的英寸數(shù)度量的。一般來(lái)說(shuō)，在其他條件相同時(shí)，進(jìn)給量與切削速度成反比。
吃刀深度——以英寸計(jì)——是刀具進(jìn)入工件的距離。它等于旋削中的切屑寬度或者等于線性切削中的切屑的厚度。粗加工比起精加工來(lái)，吃刀深度較深。
切削參數(shù)的改變對(duì)切削溫度的影響
金屬切削操作中，熱是在主變形區(qū)和副變形區(qū)發(fā)生的。這結(jié)果導(dǎo)致復(fù)雜的溫度分布遍及刀具、工件和切屑。圖中顯示了一組典型等溫曲線，從中可以看出：像所能預(yù)料的那樣，當(dāng)工件材料在主變形區(qū)被切削時(shí)，沿著整個(gè)切屑的寬度上有著很大的溫度梯度，而當(dāng)在副變形區(qū)，切屑被切落時(shí)，切屑附近的前刀面上就有更高的溫度。這導(dǎo)致了前刀面和切屑離切削刃很近的地方切削溫度較高。
實(shí)質(zhì)上由于在金屬切削中所做的全部功能都被轉(zhuǎn)化為熱，那就可以預(yù)料：被切離金屬的單位體積功率消耗曾家的這些因素就將使切削溫度升高。這樣刀具前角的增加而所有其他參數(shù)不變時(shí)，將使切離金屬的單位體積所耗功率減小，因而切削溫度也將降低。當(dāng)考慮到未變形切屑厚度增加和切削速度，這情形就更是復(fù)雜。未變形切屑厚度的增加趨勢(shì)必導(dǎo)致通過(guò)工件的熱的總數(shù)上產(chǎn)生比例效應(yīng)，刀具和切屑仍保持著固定的比例，而切削溫度變化傾向于降低。然而切削速度的增加，傳導(dǎo)到工件上的熱的數(shù)量減少而這又增加主變形區(qū)中的切屑溫升。進(jìn)而副變形區(qū)勢(shì)必更小，這將在該區(qū)內(nèi)產(chǎn)生升溫效應(yīng)。其他切削參數(shù)的變化，實(shí)質(zhì)上對(duì)于被切離的單位體積消耗上并沒(méi)有什么影響，因此實(shí)際上對(duì)切削溫度沒(méi)有什么作用。因?yàn)槭聦?shí)已經(jīng)表明：切削溫度即使有小小的變化對(duì)刀具磨損率都將有實(shí)質(zhì)意義的影響作用。這表明如何人從切削參數(shù)來(lái)確定切削溫度那是很合適的。
為著測(cè)定高速鋼刀具溫度的最直接和最精確的方法是W&T法，這方法也就是可提供高速鋼刀具溫度分布的詳細(xì)信息的方法。該項(xiàng)技術(shù)是建立在高速鋼刀具截面金相顯微測(cè)試基礎(chǔ)上，目的是要建立顯微結(jié)構(gòu)變化與熱變化規(guī)律圖線關(guān)系式。當(dāng)要加工廣泛的工件材料時(shí)，Trent已經(jīng)論述過(guò)測(cè)定高速鋼刀具的切削溫度及溫度分布的方法。這項(xiàng)技術(shù)由于利用電子顯微掃描技術(shù)已經(jīng)進(jìn)一步發(fā)展，目的是要研究將已回過(guò)火和各種馬氏體結(jié)構(gòu)的高速鋼再回火引起的微觀顯微結(jié)構(gòu)變化情況。這項(xiàng)技術(shù)亦用于研究高速鋼單點(diǎn)車刀和麻花鉆的溫度分布。
刀具磨損
從已經(jīng)被處理過(guò)的無(wú)數(shù)脆裂和刃口裂紋的刀具中可知，刀具磨損基本上有三種形式：后刀面磨損，前刀面磨損和V型凹口磨損。后刀面磨損既發(fā)生在主刀刃上也發(fā)生副刀刃上。關(guān)于主刀刃，因其擔(dān)負(fù)切除大部金屬切屑任務(wù)，這就導(dǎo)致增加切削力和提高切削溫度，如果聽(tīng)任而不加以檢查處理，那可能導(dǎo)致刀具和工件發(fā)生振動(dòng)且使有效切削的條件可能不再存在。關(guān)于副刀刃，那是決定著工件的尺寸和表面光潔度的，后刀面磨損可能造成尺寸不合格的產(chǎn)品而且表面光潔度也差。在大多數(shù)實(shí)際切削條件下，由于主前刀面先于副前刀面磨損，磨損到達(dá)足夠大時(shí)，刀具將實(shí)效，結(jié)果是制成不合格零件。
由于刀具表面上的應(yīng)力分布不均勻，切屑和前刀面之間滑動(dòng)接觸區(qū)應(yīng)力，在滑動(dòng)接觸區(qū)的起始處最大，而在接觸區(qū)的尾部為零，這樣磨蝕性磨損在這個(gè)區(qū)域發(fā)生了。這是因?yàn)樵谇邢骺ㄗ^(qū)附近比刀刃附近發(fā)生更嚴(yán)重的磨損，而刀刃附近因切屑與前刀面失去接觸而磨損較輕。這結(jié)果離切削刃一定距離處的前刀面上形成麻點(diǎn)凹坑，這些通常被認(rèn)為是前刀面的磨損。通常情況下，這磨損橫斷面是圓弧形的。在許多情況中和對(duì)于實(shí)際的切削狀況而言，前刀面磨損比起后刀面磨損要輕，因此后刀面磨損更普遍地作為刀具失效的尺度標(biāo)志。然而因許多作者已經(jīng)表示過(guò)的那樣在增加切削速度情況下，前刀面上的溫度比后刀面上的溫度升得更快，而且又因任何形式的磨損率實(shí)質(zhì)上是受到溫度變化的重大影響。因此前刀面的磨損通常在高速切削時(shí)發(fā)生的。
刀具的主后刀面磨損帶的尾部是跟未加工過(guò)的工件表面相接觸，因此后刀面磨損比沿著磨損帶末端處更為明顯，那是最普通的。這是因?yàn)榫植啃?yīng)，這像未加工表面上的已硬化層，這效應(yīng)是由前面的切削引起的工件硬化造成的。不只是切削，還有像氧化皮，刀刃產(chǎn)生的局部高溫也都會(huì)引起這種效應(yīng)。這種局部磨損通常稱作為凹坑性磨損，而且偶爾是非常嚴(yán)重的。盡管凹坑的出現(xiàn)對(duì)刀具的切削性質(zhì)無(wú)實(shí)質(zhì)意義的影響，但凹坑常常逐漸變深，如果切削在繼續(xù)進(jìn)行的話，那么刀具就存在斷裂的危機(jī)。
如果任何進(jìn)行性形式 的磨損任由繼續(xù)發(fā)展，最終磨損速率明顯地增加而刀具將會(huì)有摧毀性失效破壞，即刀具將不能再用作切削，造成工件報(bào)廢，那算是好的，嚴(yán)重的可造成機(jī)床破壞。對(duì)于各種硬質(zhì)合金刀具和對(duì)于各種類型的磨損，在發(fā)生嚴(yán)重失效前，就認(rèn)為已達(dá)到刀具的使用壽命周期的終點(diǎn)。然而對(duì)于各種高速鋼刀具，其磨損是屬于非均勻性磨損，已經(jīng)發(fā)現(xiàn)：當(dāng)其磨損允許連續(xù)甚至到嚴(yán)重失效開(kāi)始，最有意義的是該刀具可以獲得重磨使用，當(dāng)然，在實(shí)際上，切削時(shí)間遠(yuǎn)比使用到失效的時(shí)間短。以下幾種現(xiàn)象之一均是刀具嚴(yán)重失效開(kāi)始的特征：最普遍的是切削力突然增加，在工件上出現(xiàn)燒損環(huán)紋和噪音嚴(yán)重增加等。
自動(dòng)夾具設(shè)計(jì)用做裝配設(shè)備的傳統(tǒng)同步夾具把零件移動(dòng)到夾具中心上，以確保零件從傳送機(jī)上或從設(shè)備盤(pán)上取出后置于已定位置上。然而在某些應(yīng)用場(chǎng)合、強(qiáng)制零件移動(dòng)到中心線上時(shí)，可能引起零件或設(shè)備破壞。當(dāng)零件易損而且小小振動(dòng)可能導(dǎo)致報(bào)廢時(shí)，或當(dāng)其位置是由機(jī)床主軸或模具來(lái)具體時(shí)，再或者當(dāng)公差要求很精密時(shí)，那寧可讓夾具去適應(yīng)零件位置，而不是相反。為著這些工作任務(wù)，美國(guó)俄亥俄州Elyria的Zaytran公司已經(jīng)開(kāi)發(fā)了一般性功能數(shù)據(jù)的非同步西類柔順性?shī)A具。因?yàn)閵A具作用力和同步化裝置是各自獨(dú)立的，該同步裝置可以用精密的滑移裝置來(lái)替換而不影響夾具作用力。夾具規(guī)格范圍是從0.2英寸行程，5英鎊夾緊力到6英寸行程、400英寸夾緊力。
現(xiàn)代生產(chǎn)的特征是批量變得越來(lái)越小而產(chǎn)品的各種規(guī)格變化最大。因此，生產(chǎn)的最后階段，裝配因生產(chǎn)計(jì)劃、批量和產(chǎn)品設(shè)計(jì)的變更而顯得特別脆弱。這種情形正迫使許多公司更多地致力于廣泛的合理化改革和前面提到過(guò)情況那樣裝配自動(dòng)化。盡管柔性?shī)A具的發(fā)展很快落后與柔性運(yùn)輸處理裝置的發(fā)展，如落后于工業(yè)機(jī)器人的發(fā)展，但仍然試圖指望增加夾具的柔順性。事實(shí)上夾具的重要的裝置——生產(chǎn)裝置的專向投資就加強(qiáng)了使夾具更加柔性化在經(jīng)濟(jì)上的支持。
根據(jù)它們?nèi)犴樞裕瑠A具可以分為：專用夾具、組合夾具、標(biāo)準(zhǔn)夾具、高柔性?shī)A具。柔性?shī)A具是以它們對(duì)不同工件的高適應(yīng)性和以少更換低費(fèi)用為特征的。
結(jié)構(gòu)形式可變換的柔性?shī)A具裝有可變更結(jié)構(gòu)排列的零件（例如針形頰板，多片式零件和片狀頰板），標(biāo)準(zhǔn)工件的非專用夾持或夾緊元件（例如：?jiǎn)?dòng)標(biāo)準(zhǔn)夾持夾具和帶有可移動(dòng)元件的夾具配套件），或者裝有陶瓷或硬化了的中介物質(zhì)（如：流動(dòng)粒子床夾具和熱夾具緊夾具）。為了生產(chǎn)，零件要在夾具中被緊固，需要產(chǎn)生夾緊作用，其有幾個(gè)與夾具柔順性無(wú)關(guān)的步驟：
根據(jù)被加工的即基礎(chǔ)的部分和工作特點(diǎn)，確定工件在夾具中的所需的位置，接著必須選擇若干穩(wěn)定平面的組合，這些穩(wěn)定平面就構(gòu)成工件被固定在夾具中確定位置上的夾持狀輪廓結(jié)構(gòu)，均衡所有各力和力矩，而且保證接近工件工作特點(diǎn)。最后，必須計(jì)算、調(diào)整、組裝可拆裝的或標(biāo)準(zhǔn)夾具元件的所需位置，以便使工件牢牢地被夾緊在夾具中。依據(jù)這樣的程序，夾具的輪廓結(jié)構(gòu)和裝合的規(guī)劃和記錄過(guò)程可以進(jìn)行自動(dòng)化控制。
結(jié)構(gòu)造型任務(wù)就是要產(chǎn)生若干穩(wěn)定平面的組合，這樣在這些平面上的各夾緊力將使工件和夾具穩(wěn)定。按慣例，這個(gè)任務(wù)可用人—機(jī)對(duì)話即幾乎完全自動(dòng)化的方式來(lái)完成。一人—機(jī)對(duì)話即以自動(dòng)化方式確定夾具結(jié)構(gòu)造型的優(yōu)點(diǎn)是可以有組織有規(guī)劃進(jìn)行夾具設(shè)計(jì)，減少所需的設(shè)計(jì)人員，縮短研究周期和能更好地配置工作條件。簡(jiǎn)言之，可成功地達(dá)到顯著提高夾具生產(chǎn)效率和效益。
在充分準(zhǔn)備了構(gòu)造方案和一批材料情況下，在完成首次組裝可以成功實(shí)現(xiàn)節(jié)約時(shí)間達(dá)60%。
因此夾具機(jī)構(gòu)造型過(guò)程的目的是產(chǎn)生合適的編程文件。
齒輪和軸的介紹
摘 要:在傳統(tǒng)機(jī)械和現(xiàn)代機(jī)械中齒輪和軸的重要地位是不可動(dòng)搖的。齒輪和軸主要安裝在主軸箱來(lái)傳遞力的方向。通過(guò)加工制造它們可以分為許多的型號(hào)，分別用于許多的場(chǎng)合。所以我們對(duì)齒輪和軸的了解和認(rèn)識(shí)必須是多層次多方位的。
關(guān)鍵詞:齒輪；軸
在直齒圓柱齒輪的受力分析中，是假定各力作用在單一平面的。我們將研究作用力具有三維坐標(biāo)的齒輪。因此，在斜齒輪的情況下，其齒向是不平行于回轉(zhuǎn)軸線的。而在錐齒輪的情況中各回轉(zhuǎn)軸線互相不平行。像我們要討論的那樣，尚有其他道理需要學(xué)習(xí)，掌握。
斜齒輪用于傳遞平行軸之間的運(yùn)動(dòng)。傾斜角度每個(gè)齒輪都一樣，但一個(gè)必須右旋斜齒，而另一個(gè)必須是左旋斜齒。齒的形狀是一濺開(kāi)線螺旋面。如果一張被剪成平行四邊形（矩形）的紙張包圍在齒輪圓柱體上，紙上印出齒的角刃邊就變成斜線。如果我展開(kāi)這張紙，在血角刃邊上的每一個(gè)點(diǎn)就發(fā)生一漸開(kāi)線曲線。
直齒圓柱齒輪輪齒的初始接觸處是跨過(guò)整個(gè)齒面而伸展開(kāi)來(lái)的線。斜齒輪輪齒的初始接觸是一點(diǎn)，當(dāng)齒進(jìn)入更多的嚙合時(shí)，它就變成線。在直齒圓柱齒輪中，接觸是平行于回轉(zhuǎn)軸線的。在斜齒輪中，該先是跨過(guò)齒面的對(duì)角線。它是齒輪逐漸進(jìn)行嚙合并平穩(wěn)的從一個(gè)齒到另一個(gè)齒傳遞運(yùn)動(dòng)，那樣就使斜齒輪具有高速重載下平穩(wěn)傳遞運(yùn)動(dòng)的能力。斜齒輪使軸的軸承承受徑向和軸向力。當(dāng)軸向推力變的大了或由于別的原因而產(chǎn)生某些影響時(shí)，那就可以使用人字齒輪。雙斜齒輪（人字齒輪）是與反向的并排地裝在同一軸上的兩個(gè)斜齒輪等效。他們產(chǎn)生相反的軸向推力作用，這樣就消除了軸向推力。當(dāng)兩個(gè)或更多個(gè)單向齒斜齒輪被在同一軸上時(shí)，齒輪的齒向應(yīng)作選擇，以便產(chǎn)生最小的軸向推力。
交錯(cuò)軸斜齒輪或螺旋齒輪，他們是軸中心線既不相交也不平行。交錯(cuò)軸斜齒輪的齒彼此之間發(fā)生點(diǎn)接觸，它隨著齒輪的磨合而變成線接觸。因此他們只能傳遞小的載荷和主要用于儀器設(shè)備中，而且肯定不能推薦在動(dòng)力傳動(dòng)中使用。交錯(cuò)軸斜齒輪與斜齒輪之間在被安裝后互相捏合之前是沒(méi)有任何區(qū)別的。它們是以同樣的方法進(jìn)行制造。一對(duì)相嚙合的交錯(cuò)軸斜齒輪通常具有同樣的齒向，即左旋主動(dòng)齒輪跟右旋從動(dòng)齒輪相嚙合。在交錯(cuò)軸斜齒設(shè)計(jì)中，當(dāng)該齒的斜角相等時(shí)所產(chǎn)生滑移速度最小。然而當(dāng)該齒的斜角不相等時(shí)，如果兩個(gè)齒輪具有相同齒向的話，大斜角齒輪應(yīng)用作主動(dòng)齒輪。蝸輪與交錯(cuò)軸斜齒輪相似。小齒輪即蝸桿具有較小的齒數(shù)，通常是一到四齒，由于它們完全纏繞在節(jié)圓柱上，因此它們被稱為螺紋齒。與其相配的齒輪叫做蝸輪，蝸輪不是真正的斜齒輪。蝸桿和蝸輪通常是用于向垂直相交軸之間的傳動(dòng)提供大的角速度減速比。蝸輪不是斜齒輪，因?yàn)槠潺X頂面做成中凹形狀以適配蝸桿曲率，目的是要形成線接觸而不是點(diǎn)接觸。然而蝸桿蝸輪傳動(dòng)機(jī)構(gòu)中存在齒間有較大滑移速度的缺點(diǎn)，正像交錯(cuò)軸斜齒輪那樣。
蝸桿蝸輪機(jī)構(gòu)有單包圍和雙包圍機(jī)構(gòu)。單包圍機(jī)構(gòu)就是蝸輪包裹著蝸桿的一種機(jī)構(gòu)。當(dāng)然，如果每個(gè)構(gòu)件各自局部地包圍著對(duì)方的蝸輪機(jī)構(gòu)就是雙包圍蝸輪蝸桿機(jī)構(gòu)。著兩者之間的重要區(qū)別是，在雙包圍蝸輪組的輪齒間有面接觸，而在單包圍的蝸輪組的輪齒間有線接觸。一個(gè)裝置中的蝸桿和蝸輪正像交錯(cuò)軸斜齒輪那樣具有相同的齒向，但是其斜齒齒角的角度是極不相同的。蝸桿上的齒斜角度通常很大，而蝸輪上的則極小，因此習(xí)慣常規(guī)定蝸桿的導(dǎo)角，那就是蝸桿齒斜角的余角；也規(guī)定了蝸輪上的齒斜角，該兩角之和就等于90度的軸線交角。
當(dāng)齒輪要用來(lái)傳遞相交軸之間的運(yùn)動(dòng)時(shí)，就需要某種形式的錐齒輪。雖然錐齒輪通常制造成能構(gòu)成90度軸交角，但它們也可產(chǎn)生任何角度的軸交角。輪齒可以鑄出，銑制或滾切加工。僅就滾齒而言就可達(dá)一級(jí)精度。在典型的錐齒輪安裝中，其中一個(gè)錐齒輪常常裝于支承的外側(cè)。這意味著軸的撓曲情況更加明顯而使在輪齒接觸上具有更大的影響。
另外一個(gè)難題，發(fā)生在難于預(yù)示錐齒輪輪齒上的應(yīng)力，實(shí)際上是由于齒輪被加工成錐狀造成的。
直齒錐齒輪易于設(shè)計(jì)且制造簡(jiǎn)單，如果他們安裝的精密而確定，在運(yùn)轉(zhuǎn)中會(huì)產(chǎn)生良好效果。然而在直齒圓柱齒輪情況下，在節(jié)線速度較高時(shí)，他們將發(fā)出噪音。在這些情況下，螺旋錐齒輪比直齒輪能產(chǎn)生平穩(wěn)的多的嚙合作用，因此碰到高速運(yùn)轉(zhuǎn)的場(chǎng)合那是很有用的。當(dāng)在汽車的各種不同用途中，有一個(gè)帶偏心軸的類似錐齒輪的機(jī)構(gòu)，那是常常所希望的。這樣的齒輪機(jī)構(gòu)叫做準(zhǔn)雙曲面齒輪機(jī)構(gòu)，因?yàn)樗鼈兊墓?jié)面是雙曲回轉(zhuǎn)面。這種齒輪之間的輪齒作用是沿著一根直線上產(chǎn)生滾動(dòng)與滑動(dòng)相結(jié)合的運(yùn)動(dòng)并和蝸輪蝸桿的輪齒作用有著更多的共同之處。
軸是一種轉(zhuǎn)動(dòng)或靜止的桿件。通常有圓形橫截面。在軸上安裝像齒輪，皮帶輪，飛輪，曲柄，鏈輪和其他動(dòng)力傳遞零件。軸能夠承受彎曲，拉伸，壓縮或扭轉(zhuǎn)載荷，這些力相結(jié)合時(shí)，人們期望找到靜強(qiáng)度和疲勞強(qiáng)度作為設(shè)計(jì)的重要依據(jù)。因?yàn)閱胃S可以承受靜壓力，變應(yīng)力和交變應(yīng)力，所有的應(yīng)力作用都是同時(shí)發(fā)生的。
“軸”這個(gè)詞包含著多種含義，例如心軸和主軸。心軸也是軸，既可以旋轉(zhuǎn)也可以靜止的軸，但不承受扭轉(zhuǎn)載荷。短的轉(zhuǎn)動(dòng)軸常常被稱為主軸。
當(dāng)軸的彎曲或扭轉(zhuǎn)變形必需被限制于很小的范圍內(nèi)時(shí)，其尺寸應(yīng)根據(jù)變形來(lái)確定，然后進(jìn)行應(yīng)力分析。因此，如若軸要做得有足夠的剛度以致?lián)锨惶?，那么合?yīng)力符合安全要求那是完全可能的。但決不意味著設(shè)計(jì)者要保證；它們是安全的，軸幾乎總是要進(jìn)行計(jì)算的，知道它們是處在可以接受的允許的極限以內(nèi)。因之，設(shè)計(jì)者無(wú)論何時(shí)，動(dòng)力傳遞零件，如齒輪或皮帶輪都應(yīng)該設(shè)置在靠近支持軸承附近。這就減低了彎矩，因而減小變形和彎曲應(yīng)力。
雖然來(lái)自M.H.G方法在設(shè)計(jì)軸中難于應(yīng)用，但它可能用來(lái)準(zhǔn)確預(yù)示實(shí)際失效。這樣，它是一個(gè)檢驗(yàn)已經(jīng)設(shè)計(jì)好了的軸的或者發(fā)現(xiàn)具體軸在運(yùn)轉(zhuǎn)中發(fā)生損壞原因的好方法。進(jìn)而有著大量的關(guān)于設(shè)計(jì)的問(wèn)題，其中由于別的考慮例如剛度考慮，尺寸已得到較好的限制。
設(shè)計(jì)者去查找關(guān)于圓角尺寸、熱處理、表面光潔度和是否要進(jìn)行噴丸處理等資料，那真正的唯一的需要是實(shí)現(xiàn)所要求的壽命和可靠性。
由于他們的功能相似，將離合器和制動(dòng)器一起處理。簡(jiǎn)化摩擦離合器或制動(dòng)器的動(dòng)力學(xué)表達(dá)式中，各自以角速度w1和w2運(yùn)動(dòng)的兩個(gè)轉(zhuǎn)動(dòng)慣量I1和I2，在制動(dòng)器情況下其中之一可能是零，由于接上離合器或制動(dòng)器而最終要導(dǎo)致同樣的速度。因?yàn)閮蓚€(gè)構(gòu)件開(kāi)始以不同速度運(yùn)轉(zhuǎn)而使打滑發(fā)生了，并且在作用過(guò)程中能量散失，結(jié)果導(dǎo)致溫升。在分析這些裝置的性能時(shí)，我們應(yīng)注意到作用力，傳遞的扭矩，散失的能量和溫升。所傳遞的扭矩關(guān)系到作用力，摩擦系數(shù)和離合器或制動(dòng)器的幾何狀況。這是一個(gè)靜力學(xué)問(wèn)題。這個(gè)問(wèn)題將必須對(duì)每個(gè)幾何機(jī)構(gòu)形狀分別進(jìn)行研究。然而溫升與能量損失有關(guān)，研究溫升可能與制動(dòng)器或離合器的類型無(wú)關(guān)。因?yàn)閹缀涡螤畹闹匾允巧岜砻妗８鞣N各樣的離合器和制動(dòng)器可作如下分類：
1．輪緣式內(nèi)膨脹制凍塊；
2．輪緣式外接觸制動(dòng)塊；
3．條帶式；
4．盤(pán)型或軸向式；
5．圓錐型；
6．混合式。
分析摩擦離合器和制動(dòng)器的各種形式都應(yīng)用一般的同樣的程序，下面的步驟是必需的：
1．假定或確定摩擦表面上壓力分布；
2．找出最大壓力和任一點(diǎn)處壓力之間的關(guān)系；
3．應(yīng)用靜平衡條件去找尋（a）作用力；（b）扭矩；(c)支反力。
混合式離合器包括幾個(gè)類型，例如強(qiáng)制接觸離合器、超載釋放保護(hù)離合器、超越離合器、磁液離合器等等。
強(qiáng)制接觸離合器由一個(gè)變位桿和兩個(gè)夾爪組成。各種強(qiáng)制接觸離合器之間最大的區(qū)別與夾爪的設(shè)計(jì)有關(guān)。為了在結(jié)合過(guò)程中給變換作用予較長(zhǎng)時(shí)間周期，夾爪可以是棘輪式的，螺旋型或齒型的。有時(shí)使用許多齒或夾爪。他們可能在圓周面上加工齒，以便他們以圓柱周向配合來(lái)結(jié)合或者在配合元件的端面上加工齒來(lái)結(jié)合。
雖然強(qiáng)制離合器不像摩擦接觸離合器用的那么廣泛，但它們確實(shí)有很重要的運(yùn)用。離合器需要同步操作。
有些裝置例如線性驅(qū)動(dòng)裝置或電機(jī)操作螺桿驅(qū)動(dòng)器必須運(yùn)行到一定的限度然后停頓下來(lái)。為著這些用途就需要超載釋放保護(hù)離合器。這些離合器通常用彈簧加載，以使得在達(dá)到預(yù)定的力矩時(shí)釋放。當(dāng)?shù)竭_(dá)超載點(diǎn)時(shí)聽(tīng)到的“喀嚓”聲就被認(rèn)定為是所希望的信號(hào)聲。
超越離合器或連軸器允許機(jī)器的被動(dòng)構(gòu)件“空轉(zhuǎn)”或“超越”，因?yàn)橹鲃?dòng)驅(qū)動(dòng)件停頓了或者因?yàn)榱硪粋€(gè)動(dòng)力源使被動(dòng)構(gòu)件增加了速度。這種離合器通常使用裝在外套筒和內(nèi)軸件之間的滾子或滾珠。該內(nèi)軸件，在它的周邊加工了數(shù)個(gè)平面。驅(qū)動(dòng)作用是靠在套筒和平面之間契入的滾子來(lái)獲得。因此該離合器與具有一定數(shù)量齒的棘輪棘爪機(jī)構(gòu)等效。
磁液離合器或制動(dòng)器相對(duì)來(lái)說(shuō)是一個(gè)新的發(fā)展，它們具有兩平行的磁極板。這些磁極板之間有磁粉混合物潤(rùn)滑。電磁線圈被裝入磁路中的某處。借助激勵(lì)該線圈，磁液混合物的剪切強(qiáng)度可被精確的控制。這樣從充分滑移到完全鎖住的任何狀態(tài)都可以獲得。
一、畢業(yè)設(shè)計(jì)（論文）的內(nèi)容
目前市場(chǎng)上的輪椅存在一個(gè)很大的不足：由于采用了傳統(tǒng)的輪式結(jié)構(gòu)，能夠在平地上行走，面對(duì)臺(tái)階、樓梯等比較復(fù)雜的地形卻顯得無(wú)能為力，為了解決這個(gè)問(wèn)題我們只有設(shè)計(jì)出更好的輪椅，設(shè)計(jì)包括以下內(nèi)容和要完成的任務(wù)。
1、課題的調(diào)研、資料的獲取、有關(guān)知識(shí)的準(zhǔn)備等；進(jìn)行可爬樓梯式輪椅車的方案設(shè)計(jì)和選擇；設(shè)計(jì)要實(shí)用，要方便殘疾人使用。
2、理論分析、計(jì)算機(jī)建模、方案論證；利用CAXA、pro/e、solidworks等工具軟件，設(shè)計(jì)相應(yīng)的可爬樓梯式輪椅車機(jī)構(gòu)，要求繪制和裝配出輪椅的三維模型，能夠?qū)崿F(xiàn)爬樓的功能。
3、原理圖、裝配圖、零件圖設(shè)計(jì)；
4、實(shí)驗(yàn)系統(tǒng)、實(shí)驗(yàn)設(shè)計(jì)、實(shí)驗(yàn)分析、設(shè)計(jì)硬件、設(shè)計(jì)樣機(jī)。
二、畢業(yè)設(shè)計(jì)（論文）的要求與數(shù)據(jù)
要求：提出在畢業(yè)設(shè)計(jì)過(guò)程中所涉及的基本理論和關(guān)鍵問(wèn)題的要求；研究方案、研究方法和研究手段等方面的要求；課題的具體要求；課題的原始數(shù)據(jù)或主要技術(shù)指標(biāo)?？梢陨婕耙韵路矫妫?
1、進(jìn)行可爬樓梯式輪椅車的方案設(shè)計(jì)和選擇；設(shè)計(jì)要實(shí)用，要方便殘疾人使用。
2、利用CAXA、autocad等工具軟件，設(shè)計(jì)相應(yīng)的可爬樓梯式輪椅車機(jī)構(gòu)，要求繪制出輪椅的圖形，能夠?qū)崿F(xiàn)爬樓的功能。
3、原理圖、裝配圖、零件圖設(shè)計(jì)圖紙。
三、畢業(yè)設(shè)計(jì)（論文）應(yīng)完成的工作
指定整個(gè)畢業(yè)設(shè)計(jì)學(xué)生應(yīng)該完成的所有工作包括：
1、完成二萬(wàn)字左右的畢業(yè)設(shè)計(jì)說(shuō)明書(shū)（論文）；在畢業(yè)設(shè)計(jì)說(shuō)明書(shū)（論文）中必須包括詳細(xì)的300-500個(gè)單詞的英文摘要；
2、獨(dú)立完成與課題相關(guān)，不少于四萬(wàn)字符的指定英文資料翻譯（附英文原文）；
3、完成設(shè)計(jì)工作任務(wù)，例如對(duì)于理論分析、計(jì)算機(jī)建?；蛘咴O(shè)計(jì)方案的工作任務(wù)；對(duì)于系統(tǒng)方案設(shè)計(jì)、原理圖、裝配圖、零件圖設(shè)計(jì)的工作任務(wù)；以及對(duì)于實(shí)驗(yàn)設(shè)計(jì)、實(shí)驗(yàn)系統(tǒng)、實(shí)驗(yàn)分析等的工作任務(wù)。
對(duì)于純機(jī)械類課題，繪圖工作量折合A0圖紙3張以上，其中必須包含兩張A3以上的計(jì)算機(jī)繪圖圖紙；
4、畢業(yè)設(shè)計(jì)的工作量要滿足16周的工作量要求。
四、應(yīng)收集的資料及主要參考文獻(xiàn)
［1］孫桓 陳作模 葛文杰主編.機(jī)械原理［D］北京：高等教育出版社，2006
［2］楊可幀 程光蘊(yùn) 李仲生主編.機(jī)械設(shè)計(jì)基礎(chǔ)［D］北京：高等教育出版社，2006
［3］張樹(shù)仁主編.機(jī)械工程基礎(chǔ)［D］.北京：機(jī)械工業(yè)出版社，2004
［4］卜炎主編.機(jī)械傳動(dòng)裝置設(shè)計(jì)手冊(cè).上冊(cè)［M］.北京：機(jī)械工業(yè)出版社，1999
［5］卜炎主編.機(jī)械傳動(dòng)裝置設(shè)計(jì)手冊(cè).下冊(cè)［M］.北京：機(jī)械工業(yè)出版社，1999
［6］李柱 徐振高 將向前主編.互換性與測(cè)量技術(shù)［M］.北京：高等教育出版社，2004
［7］機(jī)械原理與機(jī)械設(shè)計(jì)??????????張策???????? 機(jī)械工業(yè)出版社；
［8］齒輪傳動(dòng)設(shè)計(jì)手冊(cè)朱孝錄 主編
［9］理論力學(xué) 哈爾濱工業(yè)大學(xué)理論力學(xué)研究室主編 高等教育出版社
［10］材料力學(xué)單輝祖主編 高等教育出版社
［11］材料力學(xué)（2）單輝祖主編 高等教育出版社
［12］最新鏈條設(shè)計(jì)制造工藝與鏈傳動(dòng)技術(shù)標(biāo)準(zhǔn)實(shí)用手冊(cè)吉林音像出版社
［13］The Elements of Mechanical DesignBy James G. Skakoon
五、試驗(yàn)、測(cè)試、試制加工所需主要儀器設(shè)備及條件
計(jì)算機(jī)一臺(tái) 相關(guān)軟件等
任務(wù)下達(dá)時(shí)間：
2010年 1 月12日
畢業(yè)設(shè)計(jì)開(kāi)始與完成時(shí)間：
2010年3月1日至 2010年 6 月 20 日
組織實(shí)施單位：
教研室主任意見(jiàn)：
簽字： 2010 年1 月 8 日
院領(lǐng)導(dǎo)小組意見(jiàn)：
簽字： 2010 年 1 月 11 日
畢業(yè)設(shè)計(jì)（論 文）開(kāi)題報(bào)告
1．畢業(yè)設(shè)計(jì)的目的及研究意義
目前市場(chǎng)上的輪椅存在一個(gè)很大的不足：由于采用了傳統(tǒng)的輪式結(jié)構(gòu)，能夠在平地上行走，面對(duì)臺(tái)階、樓梯等比較復(fù)雜的地形卻顯得無(wú)能為力，為了解決這個(gè)問(wèn)題我們只有設(shè)計(jì)出更好的輪椅。
2．畢業(yè)設(shè)計(jì)的主要內(nèi)容、重點(diǎn)和難點(diǎn)等
設(shè)計(jì)包括以下內(nèi)容：
1、課題的調(diào)研、資料的獲取、有關(guān)知識(shí)的準(zhǔn)備等；進(jìn)行可爬樓梯式輪椅車的方案設(shè)計(jì)和選擇；設(shè)計(jì)要實(shí)用，要方便殘疾人使用。
2、理論分析、計(jì)算機(jī)建模、方案論證；利用CAXA、pro/e、solidworks等工具軟件，設(shè)計(jì)相應(yīng)的可爬樓梯式輪椅車機(jī)構(gòu)，要求繪制和裝配出輪椅的三維模型，能夠?qū)崿F(xiàn)爬樓的功能。
3、原理圖、裝配圖、零件圖設(shè)計(jì)；
4、實(shí)驗(yàn)系統(tǒng)、實(shí)驗(yàn)設(shè)計(jì)、實(shí)驗(yàn)分析、設(shè)計(jì)硬件、設(shè)計(jì)樣機(jī)
畢業(yè)設(shè)計(jì)（論 文）開(kāi)題報(bào)告
3．準(zhǔn)備情況（查閱過(guò)的文獻(xiàn)資料及調(diào)研情況、現(xiàn)有設(shè)備、實(shí)驗(yàn)條件等）
已查閱參考文獻(xiàn)：
［1］孫桓 陳作模 葛文杰主編.機(jī)械原理［D］北京：高等教育出版社，2006
［2］楊可幀 程光蘊(yùn) 李仲生主編.機(jī)械設(shè)計(jì)基礎(chǔ)［D］北京：高等教育出版社，2006
［3］張樹(shù)仁主編.機(jī)械工程基礎(chǔ)［D］.北京：機(jī)械工業(yè)出版社，2004
［4］李柱 徐振高 將向前主編.互換性與測(cè)量技術(shù)［M］.北京：高等教育出版社 2004
［5］理論力學(xué) 哈爾濱工業(yè)大學(xué)理論力學(xué)研究室主編 高等教育出版社
［6］材料力學(xué)單輝祖主編 高等教育出版社
［7］材料力學(xué)（2）單輝祖主編 高等教育出版社
調(diào)研情況：
根據(jù)要求以及自身的能力，本畢業(yè)設(shè)計(jì)主要研究和解決的問(wèn)題有，進(jìn)行可爬樓梯式輪椅車的方案設(shè)計(jì)和選擇，利用CAXA、pro/e、solidworks等工具軟件，設(shè)計(jì)相應(yīng)的可爬樓梯式輪椅車機(jī)構(gòu)，要求繪制和裝配出輪椅的三維模型，能夠?qū)崿F(xiàn)爬樓的功能，繪制原理圖、裝配圖、零件圖設(shè)計(jì)圖紙。
現(xiàn)有設(shè)備和實(shí)驗(yàn)條件都已經(jīng)落實(shí)。
4．總體安排和進(jìn)度計(jì)劃
實(shí)行方案：
1、可爬樓梯式輪椅車的方案設(shè)計(jì)和選擇。
2、利用CAXA、pro/e、solidworks等工具軟件，設(shè)計(jì)相應(yīng)的可爬樓梯式輪椅車機(jī)構(gòu)，要求繪制和裝配出輪椅的三維模型，能夠?qū)崿F(xiàn)爬樓的功能。
3、繪制原理圖、裝配圖、零件圖設(shè)計(jì)圖紙。
畢業(yè)設(shè)計(jì)（論文）工作進(jìn)度安排：
1、 3月16號(hào)－—4月10號(hào)完成不少于四萬(wàn)字符的指定英文資料翻譯。完成課題的調(diào)研，資料的收集，前期的知識(shí)準(zhǔn)備以及理論分析、方案的論證。
2、 4月10號(hào)－—4月20號(hào)初步完成系統(tǒng)方案設(shè)計(jì)、機(jī)械原理圖、機(jī)械裝配草圖、零件草圖以及與其相關(guān)的計(jì)算。
3、 4月21號(hào)－—4月27號(hào)完成總體尺寸的設(shè)計(jì)與結(jié)構(gòu)圖的繪制，結(jié)構(gòu)總裝圖和零件圖的設(shè)計(jì)與繪制。
4、 4月27號(hào)－—5月27號(hào)完成設(shè)計(jì)相應(yīng)的可爬樓梯式輪椅車機(jī)構(gòu)。
畢業(yè)設(shè)計(jì)（論 文）開(kāi)題報(bào)告
5、 5月28號(hào)－—5月31號(hào)完成畢業(yè)設(shè)計(jì)說(shuō)明書(shū)和300－500個(gè)單詞的英文摘要。
6、 6月1號(hào)－—6月28號(hào)準(zhǔn)備畢業(yè)論文答辯前的各項(xiàng)準(zhǔn)備工作。
指導(dǎo)教師意見(jiàn)
指導(dǎo)教師（簽定）：
年 月 日
開(kāi)題小組意見(jiàn)
開(kāi)題小組組長(zhǎng)（簽定）：
年 月 日
院（系、部）意見(jiàn)
主管院長(zhǎng)（系、部主任）簽字：
年 月 日
Machine design theory
The machine design is through designs the new product or improves the old product to meet the human need the application technical science. It involves the project technology each domain, mainly studies the product the size, the shape and the detailed structure basic idea, but also must study the product the personnel which in aspect the and so on manufacture, sale and use question.
Carries on each kind of machine design work to be usually called designs the personnel or machine design engineer. The machine design is a creative work. Project engineer not only must have the creativity in the work, but also must in aspect and so on mechanical drawing, kinematics, engineerig material, materials mechanics and machine manufacture technology has the deep elementary knowledge.
If front sues, the machine design goal is the production can meet the human need the product. The invention, the discovery and technical knowledge itself certainly not necessarily can bring the advantage to the humanity, only has when they are applied can produce on the product the benefit. Thus, should realize to carries on before the design in a specific product, must first determine whether the people do need this kind of product
Must regard as the machine design is the machine design personnel carries on using creative ability the product design, the system analysis and a formulation product manufacture technology good opportunity. Grasps the project elementary knowledge to have to memorize some data and the formula is more important than. The merely service data and the formula is insufficient to the completely decision which makes in a good design needs. On the other hand, should be earnest precisely carries on all operations. For example, even if places wrong a decimal point position, also can cause the correct design to turn wrongly.
A good design personnel should dare to propose the new idea, moreover is willing to undertake the certain risk, when the new method is not suitable, use original method. Therefore, designs the personnel to have to have to have the patience, because spends the time and the endeavor certainly cannot guarantee brings successfully. A brand-new design, the request screen abandons obsoletely many, knows very well the method for the people. Because many person of conservativeness, does this certainly is not an easy matter. A mechanical designer should unceasingly explore the improvement existing product the method, should earnestly choose originally, the process confirmation principle of design in this process, with has not unified it after the confirmation new idea.
Newly designs itself can have the question occurrence which many flaws and has not been able to expect, only has after these flaws and the question are solved, can manifest new goods come into the market the product superiority. Therefore, a performance superior product is born at the same time, also is following a higher risk. Should emphasize, if designs itself does not request to use the brand-new method, is not unnecessary merely for the goal which transform to use the new method.
In the design preliminary stage, should allow to design the personnel fully to display the creativity, not each kind of restraint. Even if has had many impractical ideas, also can in the design early time, namely in front of the plan blueprint is corrected. Only then, only then does not send to stops up the innovation the mentality. Usually, must propose several sets of design proposals, then perform the comparison. Has the possibility very much in the plan which finally designated, has used certain not in plan some ideas which accepts.
How does the psychologist frequently discuss causes the machine which the people adapts them to operate. Designs personnel''s basic responsibility is diligently causes the machine to adapt the people. This certainly is not an easy work, because certainly does not have to all people to say in fact all is the most superior operating area and the operating process.
Another important question, project engineer must be able to carry on the exchange and the consultation with other concerned personnel. In the initial stage, designs the personnel to have to carry on the exchange and the consultation on the preliminary design with the administrative personnel, and is approved. This generally is through the oral discussion, the schematic diagram and the writing material carries on. In order to carry on the effective exchange, needs to solve the following problem:
(1) designs whether this product truly does need for the people? Whether there is competitive ability
(2) does this product compare with other companies'' existing similar products?
(3) produces this kind of product is whether economical?
(4) product service is whether convenient?
(5) product whether there is sale? Whether may gain?
Only has the time to be able to produce the correct answer to above question. But, the product design, the manufacture and the sale only can in carry on to the above question preliminary affirmation answer foundation in. Project engineer also should through the detail drawing and the assembly drawing, carries on the consultation together with the branch of manufacture to the finally design proposal.
Usually, can have some problem in the manufacture process. Possibly can request to some components size or the common difference makes some changes, causes the components the production to change easily. But, in the project change must have to pass through designs the personnel to authorize, guaranteed cannot damage the product the function. Sometimes, when in front of product assembly or in the packing foreign shipment experiment only then discovers in the design some kind of flaw. These instances exactly showed the design is a dynamic process. Always has a better method to complete the design work, designs the personnel to be supposed unceasingly diligently,seeks these better method.
Recent year, the engineerig material choice already appeared importantly. In addition, the choice process should be to the material continuously the unceasing again appraisal process. The new material unceasingly appears, but some original materials can obtain the quantity possibly can reduce. The environmental pollution, material recycling aspect and so on use, worker''s health and security frequently can attach the new limiting condition to the choice of material. In order to reduce the weight or saves the energy, possibly can request the use different material. Comes from domestic and international competition, to product service maintenance convenience request enhancement and customer''s aspect the and so on feedback pressure, can urge the people to carry on to the material reappraises. Because the material does not select when created the product responsibility lawsuit, has already had the profound influence. In addition, the material and between the material processing interdependence is already known by the people clearly. Therefore, in order to can and guarantees the quality in the reasonable cost under the premise to obtain satisfaction the result, project engineer makes engineers all to have earnestly carefully to choose, the determination and the use material.
Makes any product the first step of work all is designs. Designs usually may divide into several explicit stages: (a) preliminary design; (b) functional design; (c) production design. In the preliminary design stage, the designer emphatically considered the product should have function. Usually must conceive and consider several plans, then decided this kind of thought is whether feasible; If is feasible, then should makes the further improvement to or several plans. In this stage, the question which only must consider about the choice of material is: Whether has the performance to conform to the request material to be possible to supply the choice; If no, whether has a bigger assurance all permits in the cost and the time in the limit develops one kind of new material.
In the functional design and the engineering design stage, needs to make a practical feasible design. Must draw up the quite complete blueprint in this stage, chooses and determines each kind of components the material. Usually must make the prototype or the working model, and carries on the experiment to it, the appraisal product function, the reliability, the outward appearance and the service maintenance and so on. Although this kind of experiment possibly can indicate, enters in the product to the production base in front of, should replace certain materials, but, absolutely cannot this point take not earnestly chooses the material the excuse. Should unify the product the function, earnestly carefully considers the product the outward appearance, the cost and the reliability. Has the achievement very much the company when manufacture all prototypes, selects the material should the material which uses with its production in be same, and uses the similar manufacture technology as far as possible. Like this has the advantage very much to the company. The function complete prototype if cannot act according to the anticipated sales volume economically to make, or is prototypical and the official production installment has in the quality and the reliable aspect is very greatly different, then this kind of prototype does not have the great value. Project engineer is best can completely complete the material in this stage the analysis, the choice and the determination work, but is not remains it to the production design stage does. Because, is carries on in the production design stage material replacement by other people, these people are inferior to project engineer to the product all functions understanding. I
n the production design stage, is should completely determine with the material related main question the material, causes them to adapt with the existing equipment, can use the existing equipment economically to carry on the processing, moreover the material quantity can quite be easy to guarantee the supply.
In the manufacture process, inevitably can appear to uses the material to make some changes the situation. The experience indicated that, may use certain cheap materials to take the substitute. However, in the majority situation, in will carry on the production later to change the material to have in to start before the production to change the price which the material will spend to have to be higher than. Completes the choice of material work in the design stage, may avoid the most such situations. Started after the production manufacture to appear has been possible to supply the use the new material is replaces the material the most common reason. Certainly, these new materials possibly reduce the cost, the improvement product performance. But, must carry on the earnest appraisal to the new material, guarantees its all performance all to answer the purpose. Must remember that, the new material performance and the reliable very few pictures materials on hand such understood for the people. The majority of products expiration and the product accident caused by negligence case is because in selects the new material to take in front of substitution material, not truly understood their long-term operational performance causes.
The product responsibility lawsuit forces designs the personnel and the company when the choice material, uses the best procedure. In the material process, five most common questions are: (a) did not understand or cannot use about the material application aspect most newly the best information paper; (b) has not been able to foresee and to consider the dusk year possible reasonable use (for example to have the possibility, designs the personnel also to be supposed further to forecast and the consideration because product application method not when creates consequence.
In recent years many products responsibilities lawsuit case, because wrongly uses the plaintiff which the product receives the injury to accuse produces the factory, and wins the decision); (c) uses the material data not entire perhaps some data are indefinite, works as its long-term performance data is the like this time in particular; (d) the quality control method is not suitable and not after the confirmation; (e) the personnel which completely is not competent for the post by some chooses the material.
Through to the above five questions analysis, may obtain these questions is does not have the sufficient reason existence the conclusion. May for avoid these questions to these questions research analyses the appearance indicating the direction. Although uses the best choice of material method not to be able to avoid having the product responsibility lawsuit, designs the personnel and the industry carries on the choice of material according to the suitable procedure, may greatly reduce the lawsuit the quantity.
May see from the above discussion, the choice material people should to the material nature, the characteristic and the processing method have comprehensive and the basic understanding.
Introduciton of Machining
Have a shape as a processing method, all machining process for the production of the most commonly used and most important method. Machining process is a process generated shape, in this process, Drivers device on the workpiece material to be in the form of chip removal. Although in some occasions, the workpiece under no circumstances, the use of mobile equipment to the processing, However, the majority of the machining is not only supporting the workpiece also supporting tools and equipment to complete.
Machining know the process has two aspects. Small group of low-cost production. For casting, forging and machining pressure, every production of a specific shape of the workpiece, even a spare parts, almost have to spend the high cost of processing. Welding to rely on the shape of the structure, to a large extent, depend on effective in the form of raw materials. In general, through the use of expensive equipment and without special processing conditions, can be almost any type of raw materials, mechanical processing to convert the raw materials processed into the arbitrary shape of the structure, as long as the external dimensions large enough, it is possible. Because of a production of spare parts, even when the parts and structure of the production batch sizes are suitable for the original casting, Forging or pressure processing to produce, but usually prefer machining.
Strict precision and good surface finish, Machining the second purpose is the establishment of the high precision and surface finish possible on the basis of. Many parts, if any other means of production belonging to the large-scale production, Well Machining is a low-tolerance and can meet the requirements of small batch production. Besides, many parts on the production and processing of coarse process to improve its general shape of the surface. It is only necessary precision and choose only the surface machining. For instance, thread, in addition to mechanical processing, almost no other processing method for processing. Another example is the blacksmith pieces keyhole processing, as well as training to be conducted immediately after the mechanical completion of the processing.
Primary Cutting Parameters
Cutting the work piece and tool based on the basic relationship between the following four elements to fully describe : the tool geometry, cutting speed, feed rate, depth and penetration of a cutting tool.
Cutting Tools must be of a suitable material to manufacture, it must be strong, tough, hard and wear-resistant. Tool geometry -- to the tip plane and cutter angle characteristics -- for each cutting process must be correct.
Cutting speed is the cutting edge of work piece surface rate, it is inches per minute to show. In order to effectively processing, and cutting speed must adapt to the level of specific parts -- with knives. Generally, the more hard work piece material, the lower the rate.
Progressive Tool to speed iscut into the work piece speed. If the work piece or tool for rotating movement, feed rate per round over the number of inches to the measurement. When the work piece or tool for reciprocating movement and feed rate on each trip through the measurement of inches. Generally, in other conditions, feed rate and cutting speed is inversely proportional to。
Depth of penetration of a cutting tool -- to inches dollars -- is the tool to the work piece distance. Rotary cutting it to the chip or equal to the width of the linear cutting chip thickness. Rough than finishing, deeper penetration of a cutting tool depth.
Wears of Cutting Tool
We already have been processed and the rattle of the countless cracks edge tool, we learn that tool wear are basically three forms : flank wear, the former flank wear and V-Notch wear. Flank wear occurred in both the main blade occurred vice blade. On the main blade, shoulder removed because most metal chip mandate, which resulted in an increase cutting force and cutting temperature increase, If not allowed to check, That could lead to the work piece and the tool vibration and provide for efficient cutting conditions may no longer exist. Vice-bladed on, it is determined work piece dimensions and surface finish. Flank wear size of the possible failure of the product and surface finish are also inferior. In most actual cutting conditions, as the principal in the former first deputy flank before flank wear, wear arrival enough, Tool will be effective, the results are made unqualified parts.
As Tool stress on the surface uneven, chip and flank before sliding contact zone between stress, in sliding contact the start of the largest, and in contact with the tail of zero, so abrasive wear in the region occurred. This is because the card cutting edge than the nearby settlements near the more serious wear, and bladed chip due to the vicinity of the former flank and lost contact wear lighter. This results from a certain distance from the cutting edge of the surface formed before the knife point Ma pit, which is usually considered before wear. Under normal circumstances, this is wear cross-sectional shape of an arc. In many instances and for the actual cutting conditions, the former flank wear compared to flank wear light, Therefore flank wear more generally as a tool failure of scale signs. But because many authors have said in the cutting speed of the increase, Maeto surface temperature than the knife surface temperatures have risen faster. but because any form of wear rate is essentially temperature changes by the significant impact. Therefore, the former usually wear in high-speed cutting happen.
The main tool flank wear the tail is not processed with the work piece surface in contact, Therefore flank wear than wear along with the ends more visible, which is the most common. This is because the local effect, which is as rough on the surface has hardened layer, This effect is by cutting in front of the hardening of the work piece. Not just cutting, and as oxidation skin, the blade local high temperature will also cause this effect. This partial wear normally referred to as pit sexual wear, but occasionally it is very serious. Despite the emergence of the pits on the Cutting Tool nature is not meaningful impact, but often pits gradually become darker If cutting continued the case, then there cutter fracture crisis.
If any form of sexual allowed to wear, eventually wear rate increase obviously will be a tool to destroy failure destruction, that will no longer tool for cutting, cause the work piece scrapped, it is good, can cause serious damage machine. For various carbide cutting tools and for the various types of wear, in the event of a serious lapse, on the tool that has reached the end of the life cycle. But fo
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