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密 級
分類號
編 號
成 績
本科生畢業(yè)設(shè)計(jì) (論文)
外 文 翻 譯
原 文 標(biāo) 題
Mechanical Design and Manufacturing Processes
譯 文 標(biāo) 題
機(jī)械設(shè)計(jì)及加工工藝
作者所在系別
機(jī)電工程學(xué)院
作者所在專業(yè)
作者所在班級
作 者 姓 名
作 者 學(xué) 號
指導(dǎo)教師姓名
指導(dǎo)教師職稱
完 成 時(shí) 間
2017
年
2
月
譯文標(biāo)題
機(jī)械設(shè)計(jì)及加工工藝
原文標(biāo)題
Mechanical Design and Manufacturing Processes
作 者
Alex Elias
譯 名
艾力克斯
國 籍
美國
原文出處
Journal of Composite Materials
摘要:機(jī)械設(shè)計(jì)是一門通過改進(jìn)老產(chǎn)品或設(shè)計(jì)新產(chǎn)品,為了滿足人類需求而有的應(yīng)用學(xué)科。它涉及到了工程技術(shù)的許多領(lǐng)域,主要研究產(chǎn)品的尺寸和形狀以及具體結(jié)構(gòu)的詳細(xì)構(gòu)思,同時(shí)還要研究產(chǎn)品在制造、銷售及使用中面臨的各種問題。
關(guān)鍵詞:機(jī)械;設(shè)計(jì);加工工藝
進(jìn)行各種機(jī)械設(shè)計(jì)的工作人員一般被稱為設(shè)計(jì)工程師或者設(shè)計(jì)人員。機(jī)械設(shè)計(jì)一個(gè)具有創(chuàng)造性的工作。設(shè)計(jì)工程師要求在工作上具有創(chuàng)新思維,還得在工程材料、機(jī)械制圖、動力學(xué)、運(yùn)動學(xué)和機(jī)械制造工藝學(xué)等學(xué)科具有強(qiáng)大的知識儲備。
像之前所說,機(jī)械設(shè)計(jì)的目的是生產(chǎn)人類所需要的產(chǎn)品。發(fā)現(xiàn)、發(fā)明和科學(xué)知識并不一定能給人類帶來好處,只有當(dāng)它們被使用在產(chǎn)品上它們才能產(chǎn)生效益。所以,我們應(yīng)該在對一個(gè)產(chǎn)品進(jìn)行設(shè)計(jì)之前,了解人們是否需要這種產(chǎn)品。
我們應(yīng)該把機(jī)械設(shè)計(jì)看成是設(shè)計(jì)人員運(yùn)用創(chuàng)造性的思維進(jìn)行產(chǎn)品的設(shè)計(jì)、系統(tǒng)的分析以及制訂產(chǎn)品的加工工藝的一個(gè)機(jī)會。掌握機(jī)械設(shè)計(jì)的基礎(chǔ)知識比熟記一些公式和數(shù)據(jù)更重要。只用數(shù)據(jù)和公式并不能完整的做出一個(gè)好的設(shè)計(jì)。同時(shí),設(shè)計(jì)者應(yīng)該精確定的進(jìn)行運(yùn)算。比如,即使將一個(gè)小數(shù)點(diǎn)的位置弄錯(cuò),正確的設(shè)計(jì)也會變成錯(cuò)誤的。
一個(gè)好的設(shè)計(jì)工程師應(yīng)當(dāng)敢于提出新的想法,并且敢于承擔(dān)一定的風(fēng)險(xiǎn),當(dāng)方法不適合時(shí),就立即采用以前的方法。所以,設(shè)計(jì)工程師必須要有耐心,因?yàn)榛ㄙM(fèi)許多時(shí)間努力可能并不會成功。一個(gè)創(chuàng)新的設(shè)計(jì),要求設(shè)計(jì)者拋棄許多舊的、人們都知道的方法。因?yàn)樵S多人都容易墨守成規(guī),所以這樣做不是一件簡單的事情。一個(gè)設(shè)計(jì)者應(yīng)當(dāng)不斷地努力探索改良舊產(chǎn)品的方法,在這個(gè)過程中,應(yīng)該選擇原有的設(shè)計(jì)原理,并把它同新觀念相結(jié)合起來。
新設(shè)計(jì)的本身可能會有很多的缺陷和問題,只有在這些問題和缺陷解決之后,新產(chǎn)品的優(yōu)越性才能體現(xiàn)出來。所以,一個(gè)好的產(chǎn)品產(chǎn)生的同時(shí),也有著巨大的風(fēng)險(xiǎn)。應(yīng)當(dāng)強(qiáng)調(diào)的是,如果設(shè)計(jì)不要求采用完全新的方法,那就沒有必要為了改變而采用全新的辦法。
在設(shè)計(jì)的開始階段,應(yīng)當(dāng)讓設(shè)計(jì)工程師充分發(fā)揮自己的創(chuàng)造性,擺脫各種約束?;蛟S在這之中可能會產(chǎn)生許多不適用的想法,但是這可以在設(shè)計(jì)的開始階段,在生產(chǎn)圖紙繪制之前進(jìn)行改正。只有這樣,才不會阻擋創(chuàng)新的思維。一般需要提出幾種設(shè)計(jì)方案,并進(jìn)行比較??赡茉谧詈筮x擇的方案中,采用了一些未被接受的方案中的一些想法。
心理學(xué)家經(jīng)常探討怎樣讓人們適應(yīng)所操作的機(jī)器。設(shè)計(jì)工程師的基本職責(zé)是讓機(jī)器來適應(yīng)人們。這并不是一個(gè)簡單的工作,因?yàn)橐粋€(gè)對所有人都做好的操作范圍和操作過程是并不存在的。
另外一個(gè)應(yīng)當(dāng)被知道的重要問題,設(shè)計(jì)者必須能夠和其他相關(guān)人員進(jìn)行溝通和交流。與別人進(jìn)行設(shè)計(jì)方案的交流和溝通是設(shè)計(jì)的關(guān)鍵階段也是最后階段。有很多偉大的發(fā)明設(shè)計(jì)和創(chuàng)造并沒有被人們所利用,因?yàn)閯?chuàng)造者不愿意或者不善于向他人介紹自己的成果。提出方案是一個(gè)說服別人的事情。當(dāng)一個(gè)設(shè)計(jì)工程師向經(jīng)營、管理部門或者領(lǐng)導(dǎo)提出自己的新方案時(shí),就是希望說明或證明自己的方案很好。只有很好的完成這個(gè)工作,為了這個(gè)方案耗費(fèi)的大量時(shí)間和精力才會有意義。
人們只有三種表達(dá)自己思想的方式,分別是文字說明、口頭闡述和繪圖說明。所以,一個(gè)優(yōu)秀的設(shè)計(jì)師不到要掌握大量的技術(shù),還應(yīng)該掌握這幾種表達(dá)方式。如果一個(gè)技術(shù)很強(qiáng)的人,但是表達(dá)能力較差,他就會面臨巨大的困難。如果以上三種表達(dá)能力都很差,那么永遠(yuǎn)都沒有人知道他的才能。
一個(gè)真正有能力的設(shè)計(jì)工程師不該漢派自己提出的方案可能不可行。實(shí)際上,失敗是肯定會發(fā)生的,因?yàn)槊總€(gè)每個(gè)真正有創(chuàng)造性的想法總是有批評或者失敗伴隨著它。從一次失敗中可以學(xué)到很多的東西,只有不怕失敗的人才能取到巨大的收獲。
總之,決定不把方案提交出來,才是真正的失敗。?
為了進(jìn)行有效的交流,需要解決下列問題:
(1)所要設(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)品相比有無競爭能力??
?(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)品有無銷路?是否可以盈利??
只有時(shí)間才能對上述問題給出正確的答案。但是,產(chǎn)品的設(shè)計(jì)、制造和銷售只能在對上述問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)該通過零件圖和裝配圖,與制造部門一起對最終設(shè)計(jì)方案進(jìn)行溝通。通常,在制造過程中會出現(xiàn)某個(gè)問題。可能要求對某個(gè)零件尺寸或公差做一些更改,使零件的生產(chǎn)變得容易。但是,工程上的更改必須經(jīng)過設(shè)計(jì)人員批準(zhǔn),以保證不會損傷產(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。這些事例恰好說明了設(shè)計(jì)是一個(gè)動態(tài)過程??偸谴嬖谥玫姆椒▉硗瓿稍O(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。
不能采用解析法計(jì)算的情況下,可以在基本公式內(nèi)引入系數(shù)。例如,對于薄壁鋼管,考慮到腐蝕性,可將根據(jù)壓力求得的厚度增加一些。當(dāng)必須應(yīng)用一個(gè)基本公式來確定形狀、材料和使用條件,而這些被確定的量僅僅與在公式推導(dǎo)中的假設(shè)比較接近時(shí),要采取措施使結(jié)果“偏于安全”。當(dāng)數(shù)據(jù)不完全時(shí),可以應(yīng)用理論公式作為尺寸的指南,在擴(kuò)展后的范圍內(nèi)獲得令人滿意的設(shè)計(jì)結(jié)果。
4.根據(jù)性能組合選擇材料。選擇材料時(shí)需要考慮有關(guān)的性能組合,不僅考慮強(qiáng)度,硬度和重量,而且有時(shí)還要考慮抗沖擊性,抗腐蝕性和耐高溫或低溫的能力。成本和制造性能都是應(yīng)該考慮的因素,這些因素包括可焊接性,機(jī)械加工性能,對熱處理溫度變化的敏感性和所需要的涂層等。
5.在現(xiàn)有零件和整體零件之間進(jìn)行認(rèn)真的選擇。若一個(gè)以前研制的零件能夠滿足性能要求和可靠性要求,并適用于所設(shè)計(jì)的那臺機(jī)器而無須附加的研制費(fèi)用,那么設(shè)計(jì)人員及其公司通常會從零件制造廠的現(xiàn)貨中選取該零件。但是,只有充分了解其性能,才能進(jìn)行認(rèn)真的選擇工作,因?yàn)槿魏我粋€(gè)機(jī)器零件的失效都會影響公司的信譽(yù),并使公司承擔(dān)相應(yīng)的責(zé)任。在其他情況下,若機(jī)器設(shè)計(jì)人員自己來設(shè)計(jì)零件,則零件的強(qiáng)度,可靠性和成本等方面的要求就可以更好地得到滿足。可將某個(gè)零件與其他零件設(shè)計(jì)成一個(gè)整體零件,例如將幾個(gè)齒輪設(shè)計(jì)為一個(gè)鍛件或者將齒輪與軸設(shè)計(jì)為一體,這種方法的主要優(yōu)點(diǎn)是緊湊。
6.保證零件在裝配中準(zhǔn)確定位和不發(fā)生干涉。一個(gè)良好的設(shè)計(jì)能夠保證零件定位準(zhǔn)確,裝配和修理方便容易。軸肩和導(dǎo)向表面在裝配過程中不需要測量就能提供準(zhǔn)確定位。零件的形狀應(yīng)該被設(shè)計(jì)得保證這個(gè)零件不會被裝反或裝錯(cuò)位置。必須能夠預(yù)見和防止諸如不同的螺紋孔中的螺釘之間的干涉和不同的連桿機(jī)構(gòu)之間的干涉。必須避免部件之間的找正對中誤差和定位誤差,或者必須采用措施,減小任何由此引起的不利的位移和應(yīng)力。人類通過使用工具和智能,制造使其生活變得更容易和更舒適的物品這種方法,把他們自己與其他種類的生命區(qū)別開來。許多世紀(jì)以來,工具和為工具提供動力能源的種類都在不斷地發(fā)展,以滿足人類日益完善和越來越復(fù)雜的想法。
在最早的時(shí)期,工具主要是由石器構(gòu)成的。考慮到所制造的物品相對簡單的形狀和被加工的材料,石頭作為工具是適用的。當(dāng)鐵制工具被發(fā)明出來以后,耐
用的金屬和更精致的物品能夠被制造出來。在20世紀(jì)中,已經(jīng)有了一些由有史以來最耐用,同時(shí)也是最難加工的材料制造的產(chǎn)品。為了迎接這些材料給制造業(yè)帶來的挑戰(zhàn),工具材料已經(jīng)發(fā)展到包括合金鋼、硬質(zhì)合金、金剛石和陶瓷。給我們的工具提供動力的方法也發(fā)生了類似的進(jìn)步。最初,是由人或動物的肌肉為工具提供動力;隨后,水力、風(fēng)力、蒸汽和電力得到了利用,人類通過采用新型機(jī)器、更高的精度和更快的加工速度來進(jìn)一步提高制造能力。
附錄:
Mechanical Design and Manufacturing Processes
Abstract: Mechanical?design?is?the?application?of?science?and?technology?to devise?new? or?improved?products?for?the?purpose of?satisfying?human?needs.It?is?a?vast?field?of?engine technology?which?not?only?concerns?itself?with?the?original?conception?of?the?product?in ?terms?of its?size,?shape?and?construction?details but?also?considers?the?various?factors?involved?in?the?manufacture,?marketing?and?use?of?the?product.
Keywords: Mechanical,design,manufacturing process
People?who?perform?the?various?functions?of?mechanical?design?are?typically?called?desi-gners,?or?design?engineers.?Mechanical?design?is?basically?a?creative?activity.?However,?in?addition?to?being?innovative,?a?design?engineer?must?also?have?a?solid?background?in?the? a-reas?of?mechanical?drawing,?kinematics,?dynamics,?materials?engineering,?strength?of materials?and?manufacturing?processes.
As?stated?previously,?the?purpose?of?mechanical?design?is?to?produce?a?product?which will?serve?a?need?for?man.?Inventions,?discoveries?and?scientific?knowledge?by?themselve-s?do?not?necessarily?benefit?people;?only? if ?they? are ?incorporated? into? a?designed? product? will? a? benefit?be? derived.?It?should?be?recognized,?therefore,?that?a?human?nee-d?must?be?identified?before?a?particular?product?is?designed.
Mechanical?design?should?be?considered?to?be?an?opportunity?to?use?innovative?talents?t-o?envision?a?design?of?a?product,?to?analyze?the?system?and?then?make?sound?judgments?o-n?how?the?product?is?to?be?manufactured.?It?is?important?to?understand?the?fundamentals?o-f?engineering?rather? than?memorize?mere?facts? and?equations.?There?are?no? facts?or?equ-ations?which?alone?can?be?used?to?provide?all?the?correct?decisions?required?to?produce?a?go-od?design.?
On?the?other?hand,?any?calculations?made?must?be?done?with?the?utmost?care?and?precisi-on.?For?example,?if?a?decimal?point?is?misplaced,?an?otherwise?acceptable?design?may?not?f-unction.
Good?designs?require?trying?new?ideas?and?being?willing?to?take?a certain?amount?of?ris-k,?knowing?that?if?the?new?idea?does?not?work?the?existing?method?can?be?reinstated.?Thu-s?a?designer?must?have?patience,?since?there?is?no?assurance?of?success?for?the?time?and?effo-rt?expended.?Creating?a?completely?new?design?generally?requires?that?many?old?and?well-established?methods?be?thrust?aside.?This?is?not?easy?since?many?people?cling?to?familiar?id-eas,?techniques?and?attitudes.?A?design?engineer?should?constantly?search?for?ways?to?impr-ove?an?existing?product?and?must?decide?what?old,?proven?concepts?should?be?used?and?what?new,?untried?ideas?should?be?incorporated.?
New?designs?generally?have?"bugs"?or?unforeseen?problems?which?must?be?worked?out?b-efore?the?superior?characteristics?of?the?new?designs?can?be?enjoyed.?Thus?there?is?a?chanc-e?for?a?superior?product,?but?only?at?higher?risk.It?should?be?emphasized?that,if?a?design?do-es?not?warrant?radical?new?methods,?such?methods?should?not?be?applied?merely?for?the?sa-ke?of?change.?
During?the?beginning?stages?of?design,?creativity?should?be?allowed?to?flourish?withou-t?a?great?number?of?constraints.Even?though?many?impractical?ideas?may?arise,?it?is?usuall-y?easy?to?eliminate?them?in?the?early?stages?of?design?before?firm?details?are?required?by?ma-nufacturing.?In?this?way,?innovative ideas?are?not?inhibited.?Quite?often,?more?than?one?de-sign?is?developed,?up?to?the?point?where?they?can?be?compared?against?each?other.It?is?entir-ely?possible?that?the?design?which?is?ultimately?accepted?will?use?ideas?existing?in?one?of?t-he?rejected?designs?that?did?not?show?as?much?overall?promise.?
Psychologists?frequently?talk?about?trying?to?fit?people?to?the?machines?they?operate.?It?i-s?essentially?the?responsibility?of?the?design?engineer?to?strive?to?fit?machines?to?people.?Th-is?is?not?an?easy?task,?since?there?is?really?no?average?person?for?which?certain?operating??d-imensions?and?procedures?are?optimum.?
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Another?important?point?which?should?be?recognized?is?that?a?design?engineer?must?be?a-ble?to?communicate?ideas?to?other?people?if?they?are?to?be?incorporated.?Communicating?th-e?design?to?others?is?the?final,?vital?step?in?the?design?process.?Undoubtedly?many?great?desi-gns,?inventions,?and?creative?works?have?been?lost?to?mankind?simply?because?the?originat-ors?were?unable?or?unwilling?to?explain?their?accomplishments?to?others.?Presentation?i-s?a?selling?job.?The?engineer,?when?presenting?a?new?solution?to?administrative,?manageme-nt,?or?supervisory?persons,?is?attempting?to?sell?or?to?prove?to?them?that?this?solution?is?a?be-tter?one.?Unless?this?can?be?done?successfully,?the?time?and?effort?spent?on?obtaining?the?so-lution?have?been?largely?wasted.?
? Basically,?there?are?only?three?means?of?communication?available?to?us.?These?are?the?w-ritten,?the?oral,?and?the?graphical?forms.?Therefore?the?successful?engineer?will?be?technica-lly?competent?and?versatile?in?all?three?forms?of?communication.?A?technically?competen-t?person?who?lacks?ability?in?any?one?of?these?forms?is?severely?handicapped.If?ability?in?al-l?three?forms?is?lacking,?no?one?will?ever?know?how?competent?that?person?is!
The?competent?engineer?should?not?be?afraid?of?the?possibility?of?not?succeeding?in?a?pre-sentation.?In?fact,?occasional?failure?should?be?expected?because?failure?or?criticism?seem-s?to?accompany?every?really?creative?idea.?There?is?a?great?deal?to?be?learned?from?a?failure,and?the?greatest?gains?are?obtained?by?those?willing?to?risk?defeat.?In?the?final?analysis,?th-e?real?failure?would?lie?in?deciding?not?to?make?the?presentation?at?all.?
?To?communicate?effectively,?the?following?questions?must?be?answered:?
?(1)?Does?the?design?really?serve?a?human?need??
?(2)?Will?it?be?competitive?with?existing?products?of?rival?companies??
?(3)?Is?it?economical?to?produce??
?(4)?Can?it?be?readily?maintained??
?(5)?Will?it?sell?and?make?a?profit?
Only?time?will?provide?the?true?answers?to?the?preceding?questions,?but?the?product?shou-ld?be?designed,?manufactured?and?marketed?only?with?initial?affirmative?answers.?The?desi-gn?engineer?also?must?communicate?the?finalized?design?to?manufacturing?through?the?us-e?of?detail?and?assembly?drawings.?
? Quite?often,?a?problem?will?occur?during?the?manufacturing?cycle[3].?It?may?be?that?a?ch-ange?is?required?in?the?dimensioning?or?tolerancing?of?a?part?so?that?it?can?be?more?readil-y?produced.?This?fails?in?the?category?of?engineering?changes?which?must?be?approved?by?t-he?design?engineer?so?that?the?product?function?will?not?be?adversely?affected.?
In?other?cases,?a?deficiency?in?the?design?may?appear?during?assembly?or?testing?just?prio-r?to?shipping.?These?realities?simply?bear?out?the?fact?that?design?is?a?living?process.?Ther-e?is?always?a?better?way?to?do?it?and?the?designer?should?constantly?strive?towards?finding?t-hat?better?way.?
Designing?starts?with?a?need,real?or?imagined.Existing?apparatus?may?need?improvement-s?in?durability,?efficiently,?weight,?speed,?or?cost.?New?apparatus?may?be?needed?to?perfor-m?a?function?previously?done?by?men,?such?as?computation,?assembly,?or?servicing.?With?th-e?objective?wholly?or?partly?defined,?the?next?step?in?design?is?the?conception?of?mechanis-ms?and?their?arrangements?that?will?perform?the?needed?functions.?For?this,?freehand?sketch-ing?is?of?great?value,?not?only?as?a?record?of?one's?thoughts?and?as?an?aid?in?discussion?wit-h?others,?but?particularly?for?communication?with?one's?own?mind,?as?a?stimulant?for?creati-ve?ideas.When?the?general?shape?and?a?few?dimensions?of?the?several?components?becom-e?apparent, analysis?can?begin?in?earnest.The?analysis?will?have?as?its?objective?satisfactor-y?or?superior?performance,?plus?safety?and?durability?with?minimum?weight,and?a?competit-ive?east.?
Optimum?proportions?and?dimensions?will?be?sought?for?each?critically?loaded?section,to-gether?with?a?balance?between?the?strength?of?the?several?components.?Materials?and?thei-r?treatment?will?be?chosen.?These?important?objectives?can?be?attained?only?by?analysis?bas-ed?upon?the?principles?of?mechanics,?such?as?those?of?statics?for?reaction?forces?and?for?th-e?optimum?utilization?of?friction;?of?dynamics?for?inertia,?acceleration,?and?energy;of?elasticity?and?strength?of?materials?for?stress?and?deflection;?and?of?fluid?mechanics?for?lubrication?and?hydrodynamic?drives.?
Finally,?a?design?based?upon?function?and?reliability?will?be?completed,?and?a?proto typ-e?may?be?built.?If?its?tests?are?satisfactory,?and?if?the?device?is?to?be?produced?in?quantity,?th-e?initial?design?will?undergo?certain?modifications?that?enable?it?to?be?manufactured?in?qua-ntity?at?a?lower?cost.?During?subsequent?years?of?manufacture?and?service,?the?design?is?lik-ely?to?undergo?changes?as?new?ideas?are?conceived?or?as?further?analysis?based?upon?test-s?and?experience?indicate?alterations.?Sales?appeal,?customer?satisfaction,?and?manufactur-e?cost?are?all?related?to?design,?and?ability?in?design?is?intimately?involved?in?the?success?o-f?an?engineering?venture.
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