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标题: 从业超过50年的以色列机械工程师：在工程计算上，别信学校那套！ [打印本页]
作者: 小师妹_c937B 时间: 2016-9-26 13:56
标题: 从业超过50年的以色列机械工程师：在工程计算上，别信学校那套！
标题党了一把，其实这是个机械英语教学帖，当然，里面干货也不少。
今天这篇文章的主题是 engineering calculation。是一个资深以色列工程师对于刚入行的年轻人在工程计算上的意见和建议。
老规矩，我先把原文贴出来，大家自由翻译文章，并把译文贴在回复中，可以是文章中的一句，一段，有空的同学翻译全文也是极好的，参与学习的社友都能得到威望奖励。
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以下是作者简介。作者出生在以色列，毕业于以色列理工学院（传说中的中东MIT）机械工程专业，专注于机械设计超过50年，目前在以色列本古里安大学教授机械光学设计。
Adam Rubinstein
Born in Israel, studied Mechanical engineering in the Technion, specialized in mechanical design and particularly mechano-optics. Over 50 years experience as a design engineer, and about 24 of them as an independent consultant. lately, partially retired and teaching mechano-optical design at BGU in Beer-Sheva, Israel.
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) o% C; T5 N: h2 p下面是正文分隔线
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1、Don't believe everything they teach you at school, real life is very different!
2、You should immediately dismiss from your head the idea that there is only one right answer to any design question. Keep your mind open to all options.
3、Design failures can have many different forms and all should be considered.
4、What came first, the chicken or the egg? The analysis of a hypothetical design will always start with a range of assumptions which can be adjusted.
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6 p' a9 x: `2 l. s+ b, MThe difference between school and “real life” problem solving
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When we pass from high school to university we bring with us the idea that answers are obtained by engineering calculations. We use analytical formulas and we are educated to believe that the results are either right or wrong – there is no in between and no grey areas. We are used to having all of the relevant data associated with a problem. I even remember checking my answers by verifying that if I used all the data given in a problem – do we always need to use all of the data to get the answer?
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This is not real life. Data is never “given”, it is usually incomplete, and there is not necessarily a single “right” formula. I have seen many students ask me which of two different formulas (teeth strength and surface fatigue) to use for calculating gear wheels. It was very difficult to make them understand that both were “right” and that they should use the worst case. Always err on the side of caution.
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There are many ways to fail (but it only takes one)
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While teaching strength of bolts I once calculated a bolt for a number of different possible failure modes. I calculated for the “standard”, the pull strength of the core for the less common shaving of the threads and also for shearing of the head and a few more bizarre possible modes. I showed that, although all are possible, the standard bolts will nearly always fail at the core first. However, under certain conditions (too few mating threads, a weak mating material, etc) the threads might shave first. Confused? Let me explain….
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Forgetting the other possible failure modes may be very dangerous. As the designers of the first British jet airliner, the Comet, discovered at the high cost of lost planes and lives in the early 1950’s.
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The risks of designing for the real world
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It is always risky to design something new. High flying jets and the use of aluminium were pretty new in those days. British engineers also failed to realise the effects of repeating decompression loads and stress concentrations on the fatigue strength of the aluminium airframe. Calculating for static loads was just not enough.
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How did they calculate their airframe then? Computers were still in their infancy and FEA programs were not written yet. They had to use stress formulas and manual structural analysis tools. Even today, with our powerful computers and programs, it is not easy to analyse a structure as complex as an airframe. We have better research tools but the old problems and challenges are still there.
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Skill, common sense and patience
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What they must have done was to make simplifications, calculating parts of the structure one at a time and performing tests for real parts and assemblies. This was in fact a combination of some calculations with experimental testing to prove the design. We must admit that in spite of the crude tools they had they did a good job after all.
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We would like to think that today we do much better in our design work. Indeed our tools are far better than theirs but in principle what we do is very much the same. We build our models and test them by applying FEA programs. The fact that we can run the test on a computer model rather than on a hardware model is only a difference of time and cost. We must still have a finished design before we can test or analyse it.
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What came first, the chicken or the egg?
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It is a vicious circle: we need a complete design in order to test it, yet we cannot complete the design without calculating it. How do we break this vicious circle? By guessing our way to the design! By experience, by rules of the thumb and by rough calculations based on preliminary design ideas and sketches!
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Don’t forget that these early assumptions can be revisited and recalculated but at least they allow us to begin the process.
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作者: www.zdscj.com 时间: 2016-9-26 14:10
抱歉，看不懂里面的内容啊~~我回去好好学学英文
作者: 青wings 时间: 2016-9-26 14:19
1.不要全部相信你在学校学到的东西，现实生活是完全不同的
- e5 U" E" v9 l9 r4 B2.你应该完全的摒弃大脑里对于一个设计只有一种正确方案这样的想法，保持你的思路找到所有的方案
- a3 f7 v! z1 O3.设计的不当之处会表现在许多方面，每个方面都应被考虑
% r% D0 }' p. T4.先有鸡还是先有蛋，许多创新设计的研究分析开始于一系列的初步构思( t# U) o' _- I9 C2 H% l1 A+ h* c
7 e1 d Y( q1 X; v渣渣水平只有翻译些简单的，估计还有许多的错误，哈哈来个英语牛逼的大侠多译点
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作者: 左次无咎 时间: 2016-9-26 15:13
楼主，我爱你，谢谢喽，努力中
作者: 挂726面 时间: 2016-9-26 15:14
When we pass from high school to university we bring with us the idea that answers are obtained by engineering calculations. We use analytical formulas and we are educated to believe that the results are either right or wrong – there is no in between and no grey areas.
( }6 ]3 L; ~( _' R- I" v* v$ i7 H当我们从高中进入大学 我们带着我们自己的想法用工程计算得到答案。我们教育让我们相信我们使用公式分析的结果要么是对的要么是错的-在它们之间没有 灰色地带（我的理解就是模棱两可）.
作者: UGAIHAOWY 时间: 2016-9-26 16:17
What came first, the chicken or the egg? 先有鸡、还是先有蛋？; t; H& q& p. l5 q" p; l: r
+ i7 U+ d" g+ NIt is a vicious circle: we need a complete design in order to test it, yet we cannot complete the design without calculating it. How do we break this vicious circle? By guessing our way to the design! By experience, by rules of the thumb and by rough calculations based on preliminary design ideas and sketches!5 u& a- @7 q9 B
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这是个死循环： 我们需要完成一个完整的演算过程来验证它，然而这个是永远算不完的！ 那我们如何打破这个循环呢？只能有理有据的猜了！ 根据经验得，这个猜想只能靠经验法则和模糊计算来验证了！, g& J& u* \( `; `
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Don’t forget that these early assumptions can be revisited and recalculated but at least they allow us to begin the process.
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我们得牢记这些先人的猜想，因为先有猜想才能有验证，即使它需要反复验和算！; z& R0 u: Y/ C' ? l
; J! t8 Y, c- [2 V& \感觉愧对老师和她的80分！
作者: 宋仲龙 时间: 2016-9-26 16:19
当我们从高中步入大学之后，我们便形成了这样一种概念，即结果都是经过工程计算得来的。学习中通过方程分析计算得出的结果非对即错，答案是唯一的，这使得我们认为实际亦是如此。学生在处理问题时惯于把相关因素都考虑进去，我甚至记得自己判断答案正确与否是根据有没有把题目给定的相关数据都利用上了没有。然而我们真的需要把方方面面都考虑到才能得出结果吗？
$ B( u5 M R: }' o0 j7 d 现实问题并非如此。通常来说，我们掌握的资料并不完善，计算过程也不是一成不变的。学生们曾经不止一次得问我，设计齿轮时应以齿的强度为准还是以齿面的疲劳强度为准。实际上两个都可以作为齿轮设计的准则，而优先选用最可能导致齿轮最先失效的强度作为设计的准则。作为学生去理解它还是非常困难的，还需谨慎区别！
作者: 淡然 时间: 2016-9-26 16:31
What came first, the chicken or the egg?
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It is a vicious circle: we need a complete design in order to test it, yet we cannot complete the design without calculating it. How do we break this vicious circle? By guessing our way to the design! By experience, by rules of the thumb and by rough calculations based on preliminary design ideas and sketches!
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Don’t forget that these early assumptions can be revisited and recalculated but at least they allow us to begin the process.
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先有鸡还是先有蛋？. V4 _9 O% k C0 i! Q, i2 k
这是一个恶性循环，我们需要一个完整的设计来检验我们的理论。但没有计算之前，我们又无法完成这个设计。怎样才能打破这种恶性循环呢? 只能靠假设，靠经验以及”拇指法则“和建立在初步设计思路和草图上的粗略的计算。
% R+ c+ p* p b1 Y) K1 U5 l% l 虽然，这些早期的假设还需要后来的重新验证和计算，但至少凭借这些资料，我们可以开始进行设计。' \) o* I! m1 q* w( m
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对英语比较有兴趣，但基础不好，算积极参与吧。0 F3 Z6 K' k6 W* H/ Y) H
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作者: 左次无咎 时间: 2016-9-26 16:48
u6 i5 |* ?9 z) D9 H* \我要好好学英语，挣钱，养你) O7 z" l/ c( e4 H9 I
作者: 水秀天蓝 时间: 2016-9-26 17:26
淡然 发表于 2016-9-26 16:31
1 U. U% G2 V5 K/ B- |& wWhat came first, the chicken or the egg?+ F1 w3 t# U$ l- `3 s' m# [
8 a) y# p$ L2 b+ q7 QIt is a vicious circle: we need ...
据说是先有鸡，然后才有蛋。
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作者: 贝XB2016 时间: 2016-9-26 18:34
么么么么么么么么哒
作者: 燃溪 时间: 2016-9-26 21:00
There are many ways to fail (but it only takes one)1 O8 v6 t$ ^; M- _# _. _
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While teaching strength of bolts I once calculated a bolt for a number of different possible failure modes. I calculated for the “standard”, the pull strength of the core for the less common shaving of the threads and also for shearing of the head and a few more bizarre possible modes. I showed that, although all are possible, the standard bolts will nearly always fail at the core first. However, under certain conditions (too few mating threads, a weak mating material, etc) the threads might shave first. Confused? Let me explain….
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* y }( q2 M5 z5 b7 W" R失效的形式有许多种（但总归发生其中一种）
' c/ B& U% ^/ z7 x# [( n 当我讲解螺栓的受力的时候，曾经对一个工作中的螺栓，从不同的失效形式上计算过。标准失效形式——螺栓杆的极限拉力拉力，螺纹的剪力（这个不太常见），螺栓头的所受的切向力和其他一些不寻常的失效形式。我这么做，是为了让学生了解到，虽然螺栓失效的形式多种多样，但是大部分情况下，它总是在螺栓杆处首先出现问题。然而，在某种特殊的条件下（旋入螺纹太少，被连接件强度太低，等等），螺纹会首先被剪短。觉得困惑了吗？我们可以这样来解释：……
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作者: 挂726面 时间: 2016-9-27 16:08
挂726面 发表于 2016-9-26 15:14
0 P* f- z8 t) F, q/ WWhen we pass from high school to university we bring with us the idea that answers are obtained by e ...
) {) Y+ V5 I- g7 z/ d! `英语大渣渣，受教了 谢谢8 z( j. b" \4 u6 G" O4 K$ @
作者: zhumao6011 时间: 2016-9-28 08:30
1.不要相信他们在学校教你的任何事，真正的生活是非常不同的0 h8 P5 f5 e7 v- W/ e
2.你应当马上抛弃认为设计问题只有一种正确解答的这种认识，让你的大脑对各种观点敞开大门。. E4 [$ `4 [$ X* @
3.设计失败会有很多不同的形式，所有这些都应当被考虑。) B8 g( p$ `/ x% o4 ?7 W; p4 l
4.什么先出现？先有鸡还是先有蛋？一个假想设计的分析总是从可以调节的假设范围开始的。8 a1 A- |: w( p: y7 c
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作者: 滚刀鱼 时间: 2016-9-28 15:40
这只是一篇文章？还是一本书？如果只是一篇文章，请问楼主帖子里面已经贴的完整了吗？9 q' T' F5 B) ^, r* ?8 Y K- u
如果是一本书，麻烦楼主能否告诉书名？
作者: 小师妹_c937B 时间: 2016-9-28 16:32
滚刀鱼 发表于 2016-9-28 15:40
- N! r4 d7 b4 p; q0 U这只是一篇文章？还是一本书？如果只是一篇文章，请问楼主帖子里面已经贴的完整了吗？
5 D4 o% |9 X$ j, J如果是一本书，麻烦 ...
s/ _5 z7 r3 i" f3 r6 u! Y一篇文章，完整的。4 `, x9 G; l0 P* A( m
作者: 所罗门_x 时间: 2016-9-29 10:54
公主稍等片刻，我这就打开有道。。。。
作者: tedwu 时间: 2016-9-29 11:41
1. 不要再对学校里教的那套深信不疑，现实生活往往大相径庭。
% W, j" S$ P0 \# W0 A7 {2. 立马摒弃任何设计问题只有一个正确答案的错误想法，对所有备选方案敞开心扉。
+ d8 S: r+ B* ~: s9 m$ M$ ?. `3. 设计失效多种多样，考虑上需面面俱到。
% f! O& M* U8 Q0 g G4. 无需纠结于鸡先还是蛋先的悖论，设计一定基于可修正的假设。
% |, ?1 g' y1 V7 C象牙塔中和现实生活问题解决的差异% F, @/ c& R9 x2 b3 ^6 C, D
从高中进入大学的时候，我们被灌输了这样一种思想—通过工程计算来获得答案。 我们使用分析公式并且被谆谆教诲以至于对结果只有好坏（没有含混和灰色地带）的观点深信不疑，我们对问题的相关数据完全齐备的情况习以为常。我甚至对通过验证是否使用问题的所有数据来检查我的答案记忆犹新-是否总是需要使用所有的数据来获得答案？! F! Q5 [( v/ f6 L* j
这绝对与世隔绝。数据从来不是“既定的”，而通常是不完整的，绝无仅有的“正确”公式也实在不必要。曾经有诸多学子问我采用两个不同的公式（轮齿强度和齿面疲劳）的哪一个来计算齿轮，实在难以让他们理解两个公式都是“正确的”并且应当以最坏情况来计算。
4 [; E3 }8 t( F7 H2 h1 Y5 P1 u失败若水有三千（但你只能取一瓢）
/ P U% }! N+ G$ T$ X我曾经在教授螺栓强度的时候计算过诸多不同的失效模式下的螺栓强度，我按照“标准”的方法，在螺牙剪切和螺栓头剪切很少发生并且各种可能的稀奇古怪的模式基本没有的情况下只计算在螺杆的强度。 我表明了虽然一切模式皆有可能，但标准的螺栓基本上都首先在螺杆处发生破坏。即便如此，在某些情况下（比如啮合螺牙太少，贴合面太弱等等）螺牙可能首先发生破坏。觉得又说越乱，待我分解如下：
" B, N2 u% s: d2 S. i对其他可能的失效模式置若罔闻是非常危险的，第一架英国喷气式飞机Comet的设计师们就于50年代早期付出飞机失事和生命消陨的巨大代价。. ?: B1 u3 X0 g# U2 y
基于现实生活设计的风险
$ D1 p q6 Q6 I- I4 f吃头啖汤总是有风险的，高飞的喷气式飞机和铝材的应用在当年都非常新颖。英国的工程师们也未意识到重复解压载荷和应力集中对铝材机身的疲劳强度的影响，只计算静载远远不够。
' G8 Z. F. E, ]那么当时他们是如何计算机身的？在当时计算机尚在襁褓之中，FEA程序也尚未开始书写。他们不得已使用应力公式和手工的结构设计工具。即便在当今，如无强大的计算机和程序，也难题分析复杂程度堪比机身的结构， 我们虽有更好的研究工具但旧问题和挑战依然挥之不去。
3 ~: @/ \$ A2 h9 D1 q技能、常识和耐心
) |0 G; e! _1 m1 x. ^他们必须要做的就是简化，每次计算结构上的构件然后对实际的零件和组件进行测试。这种方法实际上是采用计算和实验测试的组合来验证设计。我们必须承认虽然他们工具粗陋但活干的很漂亮。
% O" Q0 q2 S5 `( s8 i1 I: O3 r我们意欲相信我们在今天的设计上做得好得多，实际上是我们的工具比他们的好得多同时绝大多数原理近乎雷同。我们用FEA程序构建模型和进行测试。在计算模型而非硬件模型上进行测试仅仅是时间和成本的差别， 在测试和分析之前我们仍然必须提供完整的设计。1 t' q/ }8 Z- U% m. H
先有鸡还是先有蛋？
$ F* Y4 ] C6 j' ^7 c0 q我们陷入了一个恶性循环：为测试我们需要一个已经完成的设计，但不经过计算我们就没法完成设计。怎么打破这个恶性循环？猜测！通过经验、经验法则和基于初步设计与草图的粗略计算。3 Z" a& j! ?, L" k+ s/ A0 {% g7 R+ W
记住：早期的假设是可以回访和再计算的，但至少这些假设让我们可以开干了。
作者: amone 时间: 2016-9-29 12:55
The risks of designing for the real world
在现实世界中进行实战设计的风险
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It is always risky to design something new. High flying jets and the use of aluminium were pretty new in those days. British engineers also failed to realise the effects of repeating decompression loads and stress concentrations on the fatigue strength of the aluminium airframe. Calculating for static loads was just not enough.
设计新颖的产品总会伴随着风险。如今，（作者用were pretty，过去时，应该是在过去谈论当今）高速喷气式飞机和铝材的应用仍然十分前沿。英国的工程师（应该指罗罗航空发动机公司）对铝合金机体的疲劳强度和重复减压负荷以及应力集中的关系仍然是认识不足。对静载荷的计算仍然不充分。
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How did they calculate their airframe then? Computers were still in their infancy and FEA programs were not written yet. They had to use stress formulas and manual structural analysis tools. Even today, with our powerful computers and programs, it is not easy to analyse a structure as complex as an airframe. We have better research tools but the old problems and challenges are still there.
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那么他们是如何计算机体的强度？当时计算机还只是个雏形，有限元分析等计算工具尚未发明。他们只能手动进行受力分析计算。即便是今天，手握强大的计算工具和软件，对机体这样复杂结构进行（力学/结构）分析仍然是困难重重。研发使用的计算工具有了充足的进步但是那些老大难的问题依然没有解决 F% j% \1 N7 R
作者: 小师妹_c937B 时间: 2016-9-29 13:33
tedwu 发表于 2016-9-29 11:41- F, D1 _/ m% u- ?# w& g
1. 不要再对学校里教的那套深信不疑，现实生活往往大相径庭。" U) T1 r, B+ G+ _
2. 立马摒弃任何设计问题只有一个正确答案的 ...
大侠的翻译已经可以当参考答案了，文字功底很深厚
作者: jcj0512 时间: 2016-9-29 15:13
我正在努力的翻译呢，确被人抢先了，算了，不发了。呵呵
作者: 彷徨2014 时间: 2016-9-29 18:26
这就是在学英语了吧
作者: andyany 时间: 2016-9-30 09:21
楼主这篇文章很不错，是从哪看来的呢？. s5 w' [# h5 m l
我很想知道。谢谢！
作者: 小师妹_c937B 时间: 2016-9-30 09:27
( Z1 @8 ?6 i) @engineeringclicks.com
作者: 荷锄望月 时间: 2016-9-30 20:44
1、Don't believe everything they teach you at school, real life is very different!
& F+ m; u1 @$ R& {; B' V勿信学校所授，现实大相径庭。! [+ D4 m- X4 x) M- B; R, b
2、You should immediately dismiss from your head the idea that there is only one right answer to any design question. Keep your mind open to all options.
]$ |" T- b: I P) c抛却心中执念，设计之旨，绝非唯一。包容并蓄，方得其趣。- D0 s. \ T: D" J
3、Design failures can have many different forms and all should be considered.
7 y8 C6 F0 }8 N1 s- }) ]) A6 L) U设计之过，成因繁多，宜细审视，不可偏废。2 W5 f1 \/ v; \
4、What came first, the chicken or the egg? The analysis of a hypothetical design will always start with a range of assumptions which can be adjusted z: n- i6 ~9 s! ~2 `$ L: @2 `
鸡生蛋乎？或否焉。假定设计分析常始于假想，亦可反矣。4 r* J2 @/ @4 C- M! _5 L1 P8 z8 M
2 |. j" O! {7 Q5 n7 y, L既然是从业五十余年，就翻得有些古味。刚看到文章，加班累了，权当换换脑子。只为戏言，权当一乐。
作者: menglingtao 时间: 2016-10-1 13:51
没学好，我回去好好学英文。
作者: 天天天蓝_ 时间: 2016-10-2 22:59
只能膜拜了
作者: 血刃x 时间: 2016-10-3 15:34
1.别信学校的那一套，现实是不一样的（学校是纸上谈兵，哈哈哈哈哈）
2 c8 S/ ?1 u9 t9 W+ H$ x" A2.你应该做的是思考更多的方案，摒弃答案唯一论( b3 _$ j* ?" A; C
作者: 血刃x 时间: 2016-10-3 15:41
荷锄望月 发表于 2016-9-30 20:44
% ~0 f+ X3 U5 d( z4 c9 e: q1、Don't believe everything they teach you at school, real life is very different! f' |9 W& N% W* E: A: i5 I
勿信学校所授，现 ...
鸡生蛋否，蛋生鸡否，能否告诉我是先有鸡还是先有蛋
- _4 e v# R$ P! m e* V5 ^
作者: jack03223 时间: 2016-10-3 18:35
进到英语吧了？
作者: liuchang-zhiyun 时间: 2016-10-5 09:19
10岁上班，从业50年，正好60岁。
作者: 屏风ing 时间: 2016-10-5 11:07
大概看了一遍，翻译不出来哟，看来四级的水平在这里就是菜鸟了
作者: 彷徨2014 时间: 2016-10-5 17:26
1、学校教的东西不要所有的都相信，现实生活中遇到的会有很大的不同。$ J! _, a0 n, I6 [& }
2、设计中遇到的问题并不仅仅只有一种正确答案，思维要开放。2 z4 q2 G6 {" N1 }4 |8 y
3、设计失败包含很多因素，考虑问题要全面。
4 ?' v, z/ r/ e4 |4、先有鸡还是先有蛋。分析所设想的设计方案时，往往是从调整设想范围开始的。
作者: 血刃x 时间: 2016-10-6 12:57
/ u& l8 A" w3 U9 } W8 w3 b Y
嗯，可能是从毛毛虫变来的/ U# K& e7 R1 F5 i. {
作者: andyany 时间: 2016-10-9 13:51
+ g$ F$ [( M" N/ O" E& ~: w3 D) ?这个网站怎么注册呢？
作者: tedwu 时间: 2016-10-20 11:56
' o- C* B. t% U! P s: q班门弄斧，谢谢鼓励。
2 m7 y2 T2 Y% \1 N- Q, R
作者: dick3848 时间: 2017-9-18 11:07
看不懂
作者: chnalzha 时间: 2017-11-28 12:26
技能，常识和耐心
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