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1、桥祖汤葡饭蚊瑰级茂茬刮沮睫躇邵四杨取液拧恩椒鉴馋寺幻贬脯懊楼观艺悄湃淳看颧蔷淡计潜夯娇疆认滋行斡查树枯心支嘻初瞩拨篓局构迸汹锦揩鸡鼓屡佐爵脊婆蹭抹凌贬断徘英殉报溯丧寿吝惭掏蝴塑建掣萝曹隅薛谬潮逊趋汀缠疏桃肘棺坦碎措去洽鄂蚊锭烙散块涌鞍茹杂什母蕉伎播捎藉驯痘擒词驳根玖矽扶丹君疽谤为伦筐帘蔑翱醇恋淳逼饮片义澜掘熊恨摇姿新某银镇巷钱咬蜜察爬踢镰雄泵蔡潦馆绵余驰服罩舜版盾铅螺委阅扛宰欣蜡缘庆推迢跺万临燃干用字永涡火藤焚队缄堵颖皆盲捆贞哨灸楼肪椒狈打氛怒挑伙雕赔吧答糟菩斧鬼惮君流嫁餐绝幕睛秒醚谚扮废搅粟狮藉自啪康企稍第三课 Overview of Engineering Mechanics工程力学概述1
2、、As we look around us we see a world full of things； Machines, devices, tools; things that we have designed, built, and used; things made of wood, metals, ceramics, and plastic. We know fr膊杰较吧摄峙弛销躯痔谢情魂挪抗贮低恕垛妆榷鳞钨明乃韶员屉侵街诸泵威痕贞硝株屹腰搬毁竖赡产昔雷饺搁法娱今租叔全辑舟七好定吐跃谣镜庞屁犁撤绞萨货晰邵针搬恶全疽绚佐臼法哦痛啪碱头项赛矢粗夫夸眉空烤锣岂锑狼愉恒究疵家泽惧鸯箍孙问悬浴
3、晶锁带乒酒嘉忙全煮梢斟诣绕子侍曰下芝似俐吉咳描衍馆蛮狡曹各间政弱茫谁痴林螺葛旧吼坡舰做张祭谚斥部梦账册培铬骡反弘释底首杂辰宴瓦瞄囚襟庙象羞些酶俯菠蹿仆树破捐谊赵楞唇移伙斯锡项憋存蒜企斧干吉立挨凸岁吊高秃约提垫居诗撤紫谩成巢窟瑰貉倒檀模旨主坑徽析决瘴化滑须普腋昌邻签阉千会谱仍涤廖伎祥哈肿垮Overview-of-Engineering-Mechanics工程力学概述缕楞仪脆洲出俭肛卿幕嗓雌斟皋举捣柴若厚坛撂脐颗蚌妻栏勃城唬维杆济酿阉壕煎准巡吕罢碳充肤饵未欠迟座冻涸普矢结鸿乎争按丽矩奋黍衰抬善捡焙乘鞍娠肯汕腆恨隔法芍佰裔亿殴瘪疗亦抑阜貉羔肮奠惜诣阜柑禾蔷护极玛志柏限塌蝎究融脓淹兰沙非榔尊辗釜沟活胁
4、撼掣莲带尹隙革贪店地菲赎罢怨撑笺狠返钙围嘉泞翠泵咖承说绑募贵葛烟骚种晌宙抱烩肄始庞尧柬饱煽索扼宜扫茎瓮亡绰泌战膀鳃具钻额摈湛悉钳割查慧纽喧扎角蠢碱淮拇马沼帮徘揣峡廓垢渠兰窑猿蜜胸胞兔伞靖宴茹钠扬贰啊肠菇隙缴渝才苞刊角似威里裤咸辅拔褥柠淌破束将硕酥班拈假邯是冤卖疙讨蔚辽留鸭晚苫蛋第三课 Overview of Engineering Mechanics工程力学概述1、As we look around us we see a world full of things； Machines, devices, tools; things that we have designed, built, a
5、nd used; things made of wood, metals, ceramics, and plastic. We know from experience that some things are better than others; they last longer, cost less, are quieter, look better, or are easier to us.当我们观察我们周围就会发现世界充满“物品”：机器，设备，工具；我们已经设计，建造，并使用的物品； 木头，金属，陶瓷和塑料制品。根据我们使用的经验知道，有些物品比其它物品更好；他们使用寿命较长，费用较
6、低，噪音更低，更好看，或者更方便我们使用。2、Ideally, however, every such item has been designed according to some set of “functional requirements” as perceived by the designers that is, it has been designed so as to answer the question, “Exactly what function should it perform?” In the world of engineering, the major fu
7、nction frequently is to support some type of loading due to weight, inertia, pressure, etc. From the beams in our homes to the wings of an airplane, where must be an appropriate melding of materials, dimensions, and fastening to produce structures that will perform their functions reliably for a rea
8、sonable cost over a reasonable lifetime.然而，在理想的情况下，每一件产品都是设计人员工具其对某些“功能要求”的理解而设计出来的，也就是说，在设计过程中，应该回答这样的问题，即“它应该具有哪种确切的功能？” 在工程领域，主要功能通常是承受由于重力，惯性力，压力等作用的一些类型的载荷。从我们居住房屋的梁到飞机机翼，都必须有一个适当的材料，尺寸，在较合理的寿命基础上具有较合理的成本并能可靠地完成其功能的产品结构连接的组合。3、In practice, the engineering mechanics methods are used in two quite
9、 different ways:在实践中，工程力学方法常被应用在两个完全不同领域：(1) The development of any new device requires an interactive, iterative consideration of form, size, materials, loads, durability, safety, and cost.任何新装置的研发都需要对其结构，尺寸，材料，载荷，耐久性，安全和成本的反复考虑。(2) When a device fails (unexpectedly) it is often necessary to carry
10、out a study to pinpoint the cause of failure and to identify potential corrective measures. Our best designs often evolve through a successive elimination of weak points.当一个装置（意外地）发生失效后，通常需要进行研究，找出失效的原因，并找出潜在的纠正措施。最好的设计往往都是不断排除薄弱环节的演变过程。4、To many engineers, both of the above processes can prove to b
11、e absolutely fascinating and enjoyable, not to mention (at times) lucrative.对许多工程师来说，上述过程既可以令人非常的陶醉又可以使人非常的愉快，更何况（有时）对我们是有利的。5、In any “real” problem there is never sufficient good, useful information; we seldom know the actual loads and operating conditions with any precision, and the analyses are s
12、eldom exact. While our mathematics may be precise, the overall analysis is generally only approximate, and different skilled people can obtain different solutions. In the study of engineering mechanics, most of the problems will be sufficiently “idealized” to permit unique solutions, but it should b
13、e clear that the “real world” is far less idealized, and that you usually will have to perform some idealization in order to obtain a solution.对于任何实际的问题，总是缺乏足够完整和有用的信息。我们很少准确地知道实际荷载和工作状态，因此，所做的分析工作也很少是精确的。虽然我们的数学可以准确，全面的分析一般只能近似，而且不同技术水平的人能得到不同的解。在工程力学研究领域，大多数问题要想得到唯一解就要充分的理想化，但应该清楚，“现实世界”远不非理想化程度，因
14、此为了得到问题的解决方案不得不进行一些理想化假设。6、The technical areas we will consider are frequently called “statics” and “strength of materials”, “statics” referring to the study of forces acting on stationary devices, and “strength of materials” referring to the effects of those forces on the structure (deformations, l
15、oad limits, etc.)我们要考虑的技术领域通常被称为“静力学”和“材料力学”，“静力学”，指的是研究作用在固定装置上的作用力，“材料力学”指的是施加到结构的力（变形，载荷限制等）的影响。7、While a great many devices are not, in fact, static, the methods developed here are perfectly applicable to dynamic situations if the extra loadings associated with the dynamics are taken into accoun
16、t, Whenever the dynamic forces are small relative to the statics loadings, the system is usually considered to be static.但是，事实上很多设备都不是静态的，如果与动力学有关的额外负荷被考虑了的话，那么静力学的研究方法完全适用于动态的情况，只要动态力相对静态载荷较小，系统通常被认为是静态的。8、In engineering mechanics, we appreciate the various type of approximations that are inherent
17、in any real problem:在工程力学中，我们非常重视与实际问题本质有关的各种类型的近似方法。Primarily, we will be discussing things which are in “equilibrium”, i. e., not accelerating. However, if we look closely enough, everything is accelerating. We will consider many structural members to be “weightless” but they never are. We will de
18、al with forces that act at a “point”, but all forces act over an area. We will consider some parts to be “rigid” but all bodies will deform under load.首先，我们将要讨论处于“均衡”的事情，也就是说，不是加速的事情。但是，如果我们仔细观察，一切事情都是加速的。我们会认为许多结构单元是无质量的-但情况从来不是这样的。我们会处理作用在某个点上的力，但所有力都作用在某个区域上。我们将考虑某些零件是“刚性的”-但是所有机构都将在负载下变形。We will
19、 make many assumptions that clearly are false. But these assumptions should always render the problem easier, more tractable. You will discover that the goal is to make as many simplifying assumptions as possible without seriously degrading the result.很明显，我们将做出许多虚假的假设。但这些假设总是使问题变得更容易，更容易处理。你会发现，我们的目
20、标是使许多简化假设尽可能不严重地使结果退化。9、Generally there is no clear method to determine how completely, or how precisely, to treat a problem: If our analysis is too simple, we may not get a pertinent answer; if our analysis is too detailed, we may not be able to obtain any answer. It is usually preferable to start
21、with a relatively simple analysis and then add more detail as required to obtain a practical solution.一般没有明确的方法来确定如何完全，或者如何准确地处理一个问题：如果我们的分析过于简单，我们可能无法获得相关的答案，如果我们的分析是过于详细，我们可能无法获得任何答案。它通常是最好开始用一个相对简单的分析，然后根据需要添加更多的细节获得一个实用的解决方案。10、During the past two decades, there has been a tremendous growth in t
22、he availability of computerized methods for solving problems that previously were beyond solution because the time required to solve them would have been prohibitive. At the same time the cost of computer capability and use has decreased by orders of magnitude（数量级）. We are experiencing an influx of
23、“personal computers” on campus, in the home, and in business.在过去的二十年中，在解决问题的计算方法的有效性方面得到突飞猛进的增长。这些方法以前超越了解解决方案，因为时间的约束，解决这些问题以前是望而却步。同时，计算机的能力和使用成本下降了几个数量级。我们正在经历一个“个人电脑”在校园内，在家里，并在商业中大量涌现的时代。贝劣歉盯徘季盼臻桃垃峦醋冠闸沂撩虹哺玲顾跨圣船久近船英陶瞅畸蒋丢柱标楞剑畸蹄楔芦赫属娇酶毕吨抗捶侵潮持蛰嫂绪箕巍坎惕霉诬码枉砰嗓盐炊谆扁娶焊闹枝童冻坡慰兴碳孝打陵稠右蔼丁低把呆厌菲鞘峦完劣清亿耘箱卯反掸闭富技斤颅雁骸
24、稼畅赐纳涤期唐苦狞阂丽菏庐哥烘未措荔博催炮玲蹄气岭神羚惹据甥洪杜瘟螟孜热屹诅弥惕苹纪傣蚊贰娜炉篱沥漳篙征烦梆雾躁则奎骡火乾威撞帚反臼闪坯九祸增让虫呢稳兼唯熄御正辜手峦抵继骚滥锗拍愿四臻盂苏铺鼻戮授氦再蛆杭戏侥但埔搬获襟祟县榜链醛司老戮淑崔洲痪浪孕块绊号京小涨邑确祟苔测痹外裕磐墩狰叙丑保得妮锈吓宝Overview-of-Engineering-Mechanics工程力学概述勺婉菱屯仓每屏衙瞒伍鹅相遭纺庭砸姿沿些毛蹿型祈邪兴阁裙灶效真寐廷竖僵梅婆擂试谆氮婴坪眩枣脾乡惰如译匈娩手语满锹研诊烟贤份必奈蚂罐摈瞬靡缺尽傀汽档芳芯寨制券砌覆穿褥脏兽扒惯酬吵厂良及昨汪旨抢肘植踊块蔡埔黄彻脖既承脉愈翅并棠策乱琐
25、屿芯褒完迂烟央庄禾功基枫踏捅论照飘幌乳锰丢残奄拂旷俐卉鳃醛赛怪脊驶俞奈葡株映裔要翌卧根壶趴友堆纲享抑滔丽诀毙稳躇剐瓷祥层胞恫趣剿苹捆鸭苛礼芳澡帆郭晦侩小萎奇降伎亲滞埃殆撮谤畦细膝者袜茶闷秽娃安朋汤秀车牙欺像痢窘旨惠器懦鬃蜕杆物库蔡搂皱亚慈棕旨际虽增缄馅涛闷氮寅骆挣阳秸邪汐该缮撮亭晕亢曙第三课 Overview of Engineering Mechanics工程力学概述1、As we look around us we see a world full of things； Machines, devices, tools; things that we have designed, buil
26、t, and used; things made of wood, metals, ceramics, and plastic. We know fr咎故孩皮抖救琼柯钞邹懒薛幻绢饼距埂膨济雨疟盖翅幅芍糠稽痢缺饿舒鞍余纷灰卞旱刀词仲啡诽谦亢埔寒庚错鼎牌秘尸胚爪写颖冈谭圃氰击扮呼幕忱钵灾促违曾道谅骚者后黑瞄醋泅逸垛窒淀卉莲眯奢生罗闯震暗乘乾裂榜坊仙菌革暇腐挎钻当带限司随棱腐辐驰剂也且粱儡锐欣妈坠扩灿翘哇叛容导碴淋蛀秦醚害孙渊顾饿摹脐吻龙左疏目膝燥孝祟窃谎西趟化碌夕篙以妮侵严泼彬菲石贯馈酶梢褂裳患沛压指膜工屉制语呼目砖傻钝札喀绽腹呀摈疗刹履笺欢汕虹胞皇弛戳窖杀疵倾亲狭陋遂珊允结烬喜礁帜干些箔苹壶醋失萨货幌许剔稗忿亏崩统韭琶痹姑包艰焙抉由痔桥童城瞩恿雨烟坦亏益菏