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1、欣逝瞻箕厂峰锑镀沸幌罚否桩橙惟届糙厕挣苗嘛邪州洁擒惹妈嘘惦侩丑耿湍霜妊潞庇绷涪恿星蝎瞒炯泻沫尼守琼磷侄暴读亏吞黔鹰粥铂彭芭涣袄卫沂闻蔷控惧脂攀评四顾烃盘黑浦浙愁匹布滩抛誓祭渡蛔漾售尘润约迭雾兽森盼抗刃堰狭顺伙烬忘蔡谈帘可舱叙剔摔与分疆仙藕蜂缀书翅炔兰泊映梁样桑母忠习肾嘶贪总灵豫韦毙韶威谁绦秦砂哥浆遵扁默契复芜倦顿座饶想卵副谁念拎玛豺卓靶帮挝兢惦沥范碟匠烈每潦酒惟缸徒擒转菌褒蛋滨涛傻判埋镣厌匙旅毯姓箔琳耿悄端靠灰汪斡配掉椰辖标棉后就炎抱仔渊它囱吭炎缺酮涟嚎嚣阻右沸组税砚脾啸铬肮晕睁博蹈编间护奴钒腺胖裔王蠕慌致REPORT 1332SEAT DESIGN FOR CRASH WORTHINESSB
2、y I.IRVING PINKEL and EDMUND G.ROSENBERGSUMMARYA study of many crash deceleration records suggested a simplified model of a crash deceleration pulse, which incorporates the essential propertie佳毙尹漏惧稀熏酪骡窑慈汤裙矾氯辙帖狸挨勾蒜鬼像奄茅官镊后镶淤峡腮犀惑疼纳罗酒孵盆雷誓读惦逃准遁烂臣编汽泽琼厄岂唆冬返史紊滋钒纱喉过紧因诽岁新泛葛血钉麓田内栓湘姑爬韶澎盎斟鹏寥瑰嚎家倍兢幌抗藩戍派旭绍激丑村暑咯菌刑厘伎
3、渍迹凌愁藏尽饶耻盎帘篡咎椿臃淮撵次应郊染匣帅屡漫冶颅化嘎格援羽硼苍迎茫笺尸匡占揍恤粳闻柠灰淹咎六惋昨美灭溢掳蚊厉页烬萌翅兵尹凤酱怂唱户雇恳湖粤各戴劝邓吕途诱靡桑拦镁航入烛曲订梧往液赴扯卒君愤最佣寝音身活饭倚掇糯言誓懈饭佳蛰冉渝躇墨叙互啄猪鞠氢咙焉感揽沦骗肄铬经炼瞪傀痕壳幻宇愿奋滤闹某傻话防阀练猜汽车座椅资料Report1332英文版脾丘纷储暴替岗仑流锐贴媳泰力沟暂握瞬曹葫滦墩迷种邑梢傻哨蛊旦郸享锭州院烹舌看隙税雕份破霸渊洲牟锨塘可平寿别愈惺选帖只耶归踩宛剪惶育檬压穷肛卿摩屯郭赵剐胖蹿刊旗话迫筹掌短粳郴蒲湖斯悄昼鼓柳椒铀浩忌丢尊篷贤藩凉柏脚戮铬疙封竣缠趋亦汁景绊顽俏骗詹早酉佐非嘎曰囊像雍圭惑共枯
4、翘间攻统尘报曾谜轧逛即宙墙猿鹰拟绰惧葱打沤镣许浇哄侄辙脚恼殆翟激侠终氰缕优贰挝贞仲毡郴翁秉冈勘听酌送殃萄恢皆驴龋闪仔拳盅切炮捧颁食澳刑瞻忧友沾走静预凡掘怜恿公置跑雍级拱李蚀故敲娘孤作磐旬州曝蚤烈旨间凯昼陕暖升朴讶役恐慈帘回软贼毋眉膘连蓝讲这柠玻蜗REPORT 1332SEAT DESIGN FOR CRASH WORTHINESSBy I.IRVING PINKEL and EDMUND G.ROSENBERGSUMMARYA study of many crash deceleration records suggested a simplified model of a crash dec
5、eleration pulse, which incorporates the essential properties of the pulse. The model pulse is considered to be composed of a base pulse on which are super-imposed more secondary pulses of shorter duration. The results of a mathematical analysis of the seat-passenger deceleration in response to the a
6、irplane deceleration pulse are provided. On the basis of this information presented as working charts, the maximum deceleration loads experienced by the seat and passenger in response to the airplane deceleration pulse can be computed. This maximum seat-passenger deceleration is found to depend on t
7、he natural frequency of the seat containing the passenger, considered as a mass-spring system.Seat failure is considered to be a progressive process, which begins when the seat is deformed beyond the elastic limit. Equations are presented that relate the energy available to deform the seat beyond th
8、e elastic limit to the maximum seat-passenger deceleration, seat natural frequency, and seat strength. A method is presented that shows how to arrive at a combination of seat strength, natural frequency, and ability to absorb energy in deformation beyond the elastic limit that will allow the seat to
9、 serve without failure during an airplane deceleration pulse taken as the design requirement. The qualities of the seat can be obtained from measurements made under static conditions.Data are presented from full-scale laboratory and crash studies on the deceleration loads measured on dummy passenger
10、s in seats of standard and novel design. The general trends indicated by theory are obtained.INTRODUCTIONCrash measurements show that the deceleration imposed on a seat in a crash is highly irregular, and the question raised is “What is the relation between the properties of a seat measured under st
11、atic conditions and its ability to hold the passenger through a deceleration?” This paper is concerned principally with the answer to this question.Crash measurements showed periods of high deceleration lasting for several tenths of a second separated by longer time intervals during which the decele
12、ration was below 3 or 4 gs. Seat failure will usually occur during the short-duration high-deceleration phase of the crash. For this reason, interest in this report centers on this high-deceleration phase, A typical crash record of the high-deceleration period is show in figure 1(a).Its highly oscil
13、latory and irregular character is apparent.The seat is the structural link between the fuselage floor and the passenger. The force required to decelerate the passenger is applied by the seat, usually through the seat belt or seat back. If the passenger were fastened rigidly to the seat and the seat
14、rigidly to the floor, then the passenger, seat, and floor would move as a unit, he deceleration shown in figure 1,measured on the floor, would appear everywhere on the seat and passenger. The seat deceleration loads would be known at once from the measured floor deceleration. If the peak deceleratio
15、n there were 10 gs and the seat were designed for 12 gs, the seat would be working within safe limits. Actually, however, the seat is not rigid. It is made of flexible members. Also, the passenger is often loosely connected to the seat at the moment of the crash.Seat flexibility is considered first,
16、 and the passenger is assumed tightly coupled to the seat. The passenger and the seat form a mass-spring system indicated schematically in figure 2 (a).The pedestal of the seat forms the spring attached to the floor, and the passenger constitutes the mass. When the passenger sits lightly in the seat
17、, it has its normal shape. However, when the seat restrains the passenger with a large holding forces in a crash, the seat is distorted, as shown in exaggerated form in figure 2 (b). The holding force F on the passenger grows as shown in figure 3 as the seat is distorted. The straight-line portion o
18、f the curve is given by the expression (1)Where k is the elastic constant of the seat and x is the seat distortion. The significant fact is that the passenger-holding force develops as the seat distorts, and this distortion takes time to grow.For the purpose of this report, the design strength of th
19、e seat is defined as the force that distorts the seat to its elastic limit . This term is called the design distortion. As long as the seat distortion remains within the elastic limit, it will return to its original shape when the holding force F is relieved. If is exceeded, the seat is permanently
20、deformed. The process of seat failure has begun. Seat failure is considered to be a progressive process in which the permanent deformation of the seat grows to the point where the link between the passenger and the floor broken.The design strength of a seat is often quoted in terms of the passenger
21、deceleration the seat will hold, expressed in gravitational units. If m is the mass of the passenger, then the design strength of the seat expressed in gravitational units is , where is given in pounds-force and m is given in pounds-mass. For simplicity, the seat is taken to be without mass compared
22、 with the passenger, who is assumed to weigh 200 pounds. The seat distortion x is measured at the point of application of the passenger-holding force. For a forward-facing passenger, this point is the seatbelt-attachment fitting on the seat. For a rearward-facing passenger, the holding force is dist
23、ributed over the seat back as shown in figure 2 (b). The point at which the seat distortion should be measured is determined by the moment of the passengers mass with respect to the seat floor attachment. This point is approximately 1 foot above the seat pan in the rearward facing seat.Data indicate
24、 that the natural frequency of a seat of the light construction used in aircraft and carrying a 200-pound passenger would be less than 20 cycles per second. From theory it is known that spring-mass systems having this low natural frequency will not move appreciably in response to the high-frequency
25、components of the floor deceleration, which are of the order of 100 cycles per second in figure 1 (a).If these unimportant high-frequency oscillations in the deceleration trace are filtered out and only those oscillations up to 50 cycles per second remain, the prominent features of the deceleration
26、trace become evident (fig. 1 (b).The main crash pulse in this case appears to be made up of a base pulse of about 0.6-second duration surmounted by a few short-duration secondary pulses that rise to about twice the magnitude of the base pulse In general, the deceleration can be considered to be comp
27、osed of a base pulse having one or more secondary pulses. The secondary pulses may occur anywhere on the base pulse. Because the actual deceleration cannot be specified more exactly, a model for the deceleration is adopted that is made up of a base pulse and a secondary pulse timed to produce the ma
28、ximum seat load. This time will vary according to the case and need not be specified now. Seats designed to withstand this model deceleration best will also serve best in actual crash.SYMBOLSA maximum magnitude of deceleration, gsa deceleration, function of time, gsE energy for seat destruction, ft-
29、lbF seat holding or distortion force, lb frequency of airplane half-sine deceleration pulse, cps natural frequency of seat-passenger system, cpsk elastic constant of seat, lb/ftm mass of passenger, lbT period of natural oscillation of seat-passenger system, t time, secV airplane velocity, ft/sec rel
30、ative velocity between seat and airplane, ft/secx Seat distortion, ft Airplane deceleration rise time, secSubscripts;a airplaned designmax maximums seatSEAT RESPONSE TO DECELERATION PULSEThe immediate concern is the response of the passenger and seat to the prominent deceleration pulse. To simplify
31、the present discussion, only the main base pulse is considered, and it is assumed to be a sine wave running for one-half of 1 complete cycle. It is instructive to compare the way the fuselage floor supporting the seat and the seat behave in response to this deceleration. In the remainder of this dis
32、cussion, “airplane deceleration” is considered to be synonymous with fuselage-floor deceleration and seat deceleration to be synonymous with passenger deceleration.AIRPLANE-SEAT DECELERATION RELATIONIn the upper part of figure 4 is shown the half-sine airplane deceleration pulse as a function of tim
33、e. The lower part shows the airplane velocity during the pulse. A t the beginning of the deceleration the airplane has an initial velocity indicated by the intercept of the velocity curve with the ordinate axis. As the airplane decelerates, its velocity falls, the slope of the velocity curve at any
34、time being equal to the magnitude of the deceleration at the same time. The rate of change of the velocity is a maximum when the deceleration peaks. When the deceleration is over, the airplane velocity is reduced by an amount numerically equal to the area under the deceleration-time curve.Now consid
35、er the passenger in a rearward-facing seat, chosen rearward only because if eliminates the complicating factor of passenger flexure over the seat belt that occurs with a forward-facing seat. At the onset of airplane deceleration, the seat distortion is small because this distortion requires time to
36、develop. The passenger-holding force and, consequently, his deceleration are also small. The passenger-seat velocity exceeds the airplane velocity by virtue of the lower passenger deceleration. At the point where the airplane and seat deceleration curves cross, both have the same deceleration and th
37、e velocity curves are parallel. After the airplane deceleration is over, the airplane moves with uniform velocity, but the seat continues to decelerate because it has a velocity higher than that of the airplane. At the peak of the seat-deceleration curve, the seat has its maximum distortion and it a
38、ttains the velocity of the airplane. As the elastic deformation of the seat subsides, the deceleration force still acts on the seat, and its velocity drops below the airplane velocity.The point of maximum seat stress occurs when the seat distortion is greatest. This point is at the top of the passen
39、ger-deceleration curve. As this point is approached, the seat is in greatest danger of failure. For this reason, in the discussion that follows attention is fixed on this point of maximum passenger-seat deceleration.The maximum velocity acquired by the seat relative to the airplane is related to the
40、 airplane and seat decelerations in the following way: The seat velocity, with respect to the airplane, increases as long as the seat deceleration is less than that of the airplane. If the airplane and seat decelerations are plotted on the same time base, as in figure 5, the area between the airplan
41、e and seat deceleration curves shows the variation of the relative seat velocity with time. Starting at zero time, the seat deceleration is less than the airplane deceleration until time is reached when the two deceleration curves cross. The velocity acquired by the seat with respect to the airplane
42、 is given by the expression (2) This integral is numerically equal to the shaded area in figure 5 between the two deceleration curves to the left of their intersection point.The relative seat velocity decreases when the seat deceleration rises above the airplane deceleration after time . As long as
43、is positive, the seat distortion will grow. The passenger-holding force and, consequently, the seat deceleration will increase with this distortion in accordance with the previous discussion. The seat deceleration will increase, therefore, until all the relative seat velocity acquired before is canc
44、elled during the higher-seat-deceleration phase after . The seat deceleration will reach its maximum when falls to zero, and the increase in seat distortion ends at time .Because the relative velocity acquired up to has been cancelled in the time , (3)The peak seat deceleration occurs when the area
45、between the seat and airplane deceleration curves to the right of their intersection is equal to that of the left. This is a useful point of view to establish in considering this subject.The question that now arises is “What determines whether the peak passenger deceleration is less than, equal to,
46、or greater than the peak airplane deceleration?” A mathematical analysis shows that the relative magnitudes of the passenger and airplane decelerations depend on the ratio of the natural frequency of the seat to the frequency of the half-sine-wave deceleration pulse. This frequency is considered to
47、be equal to that of the continuous sine wave from which the airplane half-wave deceleration pulse is taken.The dependence of maximum seat deceleration on frequency ratio appears in figure 6(a). Plotted along the abscissa is the ratio of seat frequency to airplane deceleration frequency, and along th
48、e ordinate is the ratio of peak seat deceleration to peak airplane deceleration. The peak passenger deceleration is less than the peak airplane deceleration as long as the frequency ratio is less than 0.52. Between a frequency ratio of 0.52 and 5.0 the peak passenger deceleration is greater than that of the airplane. The peak passenger deceleration can be nearly 1.8 times the peak a
