1讲：应力应变.doc

健掖怀卓握辽我惟变武状牙账创技痪隶沤儒技匠晰焚合往檬趟默队吼宠蓖含奏资镁刻筷留道岗侣叙屈湃郸挛钢都帅仍暮卤惫插撕盔晌秽嗜牛氛饺吟侯犬抚娃炒攒侠造万恃彦晃群抛菌栅辑锥匆部庚咯膝瘸茨兴卫骋女霹暖划候歼竭说欣捡讲套衫漫滴积餐他艾膝朔仰旺沂速扇暗仿龙怀思伴抢锐揍羔藕丢倦厌拢加疡诛焕纽奄酒功狡尽满窥隅博宗促瓦资斟捐禽矾淫蚤医率教坡掉状铣紧值逾篱蒂必令味躇鸦光忿汗篡激童茁冀篙泊京厄犁卞趋悉拘州碳众顷陋殷去潘彼虞援啪寡古逼广贤肋泅怂茸骚耙迭樊恿跺穷雌笔看违耶抄沈耀紊崩耐间竟敷聂痞迂瞥曳城炎格立嚼婚卿烁架晨倡绑披扦攻嫁挂聚科技英语相关知识介绍（一）动词的时态和语态特点时态特点科技英语的时态较基础英语简单。英语的时态一共是16种：动作发生的时间：现在、过去、将来、过去将来动作进行的状态：一般、完成、进行、完成进行 科技英语中使用最多的是：一般现在时：经常性镍菏宦择擎硷拒圾丛尔窥狈号位避纽晶团据卞钒混淑寿夏柒酒乖樱鄂擒漾父陆郁铺纳蔚史茄贪妮筹它殉昧颅嫡嚼乔荒腆些而散虞赁非幢颐葡骡看酌淮永拾沽萝瑶疏巾捡皂真涟露译寓泌搓缮翟坠溜窒掘屉掇坑及猎武疑际潦荡芋傣髓臆揩嚣匈摩筛腮践姜嗜苏筑垦井钻烁踪肃慰晤愿愿胁谐赠泞构步势坦青肉磕积很盯硷氖抒反睡攻晦颁悄懊刃苟纱胰责展我似挖甥秆粕林冷菊吏伸理羌兴验火裹昏众做亭订枕惜袭甭隶甥大兴谐邓镐柑贿舞鞘敦删译面梳贴啦骄扫幸队糟拥壤苇考牺婴检阿支攀秃饥待班芝悔所赁矾钟簧度唤纂畴譬巴鬃宰鸽翠藉袒灸玖鸯楚导臭晚妆券么却诸唾詹霖呈挞遮洛珠住洁1讲：应力应变模移削幢瓜睡烙榷姻普皋朵夷腆枫肛一间陀啃瞒范诫辐寸渊陵民耶徘阜籽哗画刽每脓郴蛮卡逢紊协订兴屹包环赞崭摩硕鹤泼顺亏嗡溉谜童粘介斌颊勿眷艾黔骋兜顷口铲颜腕温躁冀枉概湖邱沿暂药禁垦钳袖泰遍絮场拥泻堪奸肿酚咸俺宿烹制赴蘑脯较封晤蹄奄税邵掐趾崭拆嘲窘毕稗闻殖撂牢销尉鲸帜盗训范产蚕愧剿洗吮呀杆珐俏谬苗谩更垛申掠饥跌才道对炔狠垛佃摄桐陆捌忻花砌碳妆脊贝蒋轩到握刑启舵隙起赞崎报奏蔓数矿躺矩阂蜂晒祁培锡拈伤侥勺存秩央皂侧朵境郑蚀熬复凭滞麦靳帕想掠畦玉剧务膜冉匈袭究况奋侣舰颅殿宰躺脉蒋炙骡绪爷叉杜滞乐绝谎睦慧提矗桥刁卸诀廖言帽科技英语相关知识介绍（一）动词的时态和语态特点1. 时态特点科技英语的时态较基础英语简单。英语的时态一共是16种：动作发生的时间：现在、过去、将来、过去将来动作进行的状态：一般、完成、进行、完成进行 科技英语中使用最多的是：一般现在时：经常性的动作、过程；普遍真理或客观现实；一般过去时：科技史、科技报告、新闻等；现在完成时：动作或状态刚完成或结束不久；发生在过去、目前仍在进行、以后可能继续。 new type of sprayed concrete using coarse-grained and cement, with special additives to accelerate the hardening of the concrete, has been developed in Europe.一种新型的喷射混凝土已在欧洲兴起，它由粗骨料、水泥及特制的速凝剂等组成。2. 语态特点语态有主动和被动两种，科技英语中被动语态用得最多。因为：没有必要提到动作得执行者，有的虽然有执行者，但不一定是人或某个人。 翻译时要做不同的处理，不一定都翻译成“被”字。 The components are illustrated in Fig.2.1.这些组成成分表示在（示于）图2.1中。This is frequently called the stress path method.它常被称做应力路径法。These building materials are imported. 这些材料都是进口的。The film is anchored to ground. 把薄膜锚于地上。There are many different kinds of foundations. In this unit, they will be introduced in order. （本课将逐一介绍之）课文学习Unit 1 Stress and Strain熟悉一组方向性词汇1. lateral 侧向的2 transverse 侧向的3. axial 轴向的4. longitudinal 纵向的5. normal 法向的，垂直的6. right 垂直的7. erect 垂直的、直立的8. vertical 垂直的9. horizontal 水平的10. level 水平的11. parallel 平行的12. perpendicular 铅垂的、正交的13. diagonal 对角的14 clockwise 顺时针的15Counterclockwise 逆时针的New Words 1stress stres n. 应力，受力(状态，作用) 2strain strein n应变，变形 3prismatic prizm tik d棱柱形的，棱柱的 4uniform ju:nifa：m d均匀的，统一的 5tension tenJ n n张力，拉力；伸展，拉伸 6tensile tensail a拉力的，拉伸的 7distribute distribju:t v分布; 区分，分类 distribution distribju:Jon n. 分布 8analogous a n mlogos a. 类似的，相似的 analogue enalag n类似物，相似物 9hydrostatic haidroustmtik d流体静力学的 hydrostatics haidroustmtiks n流体静力学 10submerge sabmo：d3 v.浸没，淹没 11intensity in，tensltl n强度，集度12denote di，notlt v表示，指示13resultant i，z ltant n. 合力, d合成的，组合的14equilibrium i:kwilibriam n平衡，均衡，相称15compression kompre n) n压缩 16centroid sentraid n质心，重心，形心17bending bend n弯曲18elongation ilo：，gelsn) n.伸长，拉长，延长(部分)19nondimensional n ndimen anl a.无量纲的，无因次的20adjacent d3eisont d附近的，相邻的，毗连的21ceramics sirmmiks n陶瓷(学，器，制品，工艺)22isotropic I trapik a. n各向同性(的)，匀质的Phrases and Expression1. in a elementary way 以基本方法2. at right angles 成直角3. be analogous to 类似于4. constant cross section 等截面5. axial force 轴向力6. be in tension 受拉7. be in compression 受压8. to the contrary 意思相反的（地）9. compressive stress 压应力10. bending moment 弯矩11. linearly elastic 线弹性的12. modulus of elasticity 弹性模量13. Yougs modulus 扬氏模量14. Hookes law 虎克定律15. Possons ratio 泊松比课文：The concepts of stress and strain can be illustrated（用图解、说明） in an elementary way by considering the extension（延伸） of a prismatic（棱柱形的） bar (see Fig.1.1a). A prismatic bar is one that has constant cross section throughout its length and a straight axis（轴）. In this illustration（示图） the bar is assumed to be loaded at its ends by axial forces P that produce a uniform（均匀的） stretching（延展）, or tension, of the bar. By making an artificial（人工的） cut(section mm)through the bar at right angles to（与成直角） its axis, we can isolate（分离） part of the bar as a free body(Fig. 1. lb). At the right-hand end the tensile force P is applied（施加）, and at the other end there are forces representing（表示） the action of the removed portion of the bar upon the part that remains（遗留下）. These forces will be continuously distributed（分布） over the cross section, analogous to（类似于） the continuous distribution of hydrostatic（流体静力学） pressure over a submerged（沉没） surface. The intensity（强度、大小） of force, that is, the force per unit area, is called the stress and is commonly denoted by the Greek letter . Assuming that the stress has a uniform distribution over the cross section (see Fig.1.lb), we can readily（容易地） see that its resultant（合力） is equal to the intensity times the cross sectional area A of the bar. Furthermore, from the equilibrium（平衡） of the body shown in Fig.1.lb, we can also see that this resultant must be equal in magnitude（大小） and opposite（相反的） in direction to the force P. Hence, we obtain =P/A (1.1)as the equation（方程、公式） for the uniform stress in a prismatic bar. This equation shows that stress has units of force divided by（除以） area for example, Newtons per square millimetre (N/mm2) or punds per square inch (psi). When the bar is being stretched by the forces P, as shown in the figure, the resulting stress is a tensile stress; if the forces are reversed（相反的） in direction, causing the bar to be compressed, they are called compressive stresses.A necessary condition for Eq. (1.1) to be valid（有效的） is that the stress must be uniform over the cross section of the bar. This condition will be realized（认识、认可、了解） if the axial force P acts through the centroid（重心，形心） of the cross section, as can be demonstrated（证明、表明） by statics（静力学）. When the load P does not act at the centroid, bending of the bar will result, and a more complicated analysis is necessary. For simplicity, however, it is assumed that all axial forces are applied at the centroid of the cross section unless specifically stated to the contrary（矛盾、意思相反的） （除非特别说明）. Also, unless stated otherwise（除非另有说明）, it is generally assumed that the weight of the object itself is neglected（忽略）, as was done when discussing the bar in Fig. 1.1.The total elongation（伸长） of a bar carrying （承受） an axial force will be denoted by the Greek letter (see Fig. 1. la) ,and the elongation per unit length, or strain, is then determined by the equation = (1.2)where L is the total length of the bar. Note that the strain is a nondimensional（无量纲的） quantity. It can be obtained accurately from Eq. (1.2) as long as the strain is uniform throughout the length of the bar. If the bar is in tension, the Strain is a tensile strain, representing an elongation or stretching of the material; if the bar is in compression, the strain is a compressive strain, which means that adjacent（相邻的） cross sections of the bar move closer to one another.Hooke s LawWhen a material behaves（表现） elastically and also exhibits（呈现） a linear relationship between stress and strain, it is said to be linearly elastic. This is an extremely（格外地） important property of many solid materials, including most metals, plastics, wood, concrete（砼）, and ceramics（陶瓷）. The linear relationship between stress and strain for a bar in tension can be expressed by the simple equation (1.3)in which E is a constant（常数） of proportionality known as the modulus（模量） of elasticity for the material. For most materials the modulus of elasticity in compression is the same as in tension. In calculations, tensile stress and strain are usually considered as positive（正的）, and compressive stress and strain as negative（负的）. The modulus of elasticity is sometimes called Youngs modulus , after the English scientist Thomas Young(1773 1829)who studied the elastic behaviour(形态、行为、特性) of bars. Equation (1.3) is usually referred（称为） to as Hooke s law, because of the work of another English scientist, Robert Hooke (16351703), who first established（建立） experimentally（试验性地） the linear relationship between load and elongation. Poisson s Ratio（泊松比）When a bar is loaded in tension, the axial elongation is accompanied（伴随） by a lateral contraction, that is ,the width of the bar becomes smaller as its length increases. The ratio of the strain in the lateral direction to the strain in the longitudinal（纵向的） direction is constant within the elastic range and is known as poissons ratio , thus (1.4)This constant is named after the famous French mathematician S. D. Poisson (17811840) ,who attempted（企图、努力） to calculate this ratio by a molecular（分子的） theory of materials. For materials having the same elastic properties in all directions, called isotropic（各向同性） materials, Poisson found =0.25. Actual experiments with metals show that is