汽車安全氣囊碰撞有限元分析外文翻譯

1、FINITE ELEMENT ANALYSIS OF AUTOMOBILECRASH SENSORS FOR AIRBAG SYSTEMSABSTRACTAutomobile spring bias crash sensor design time can be significantly reduced by using finiteelement analysis as a predictive engineering tool.The sensors consist of a ball and springscased in a plastic housing.Two important

2、 factors in the design of crash sensors are theforce-displacement response of the sensor and stresses in the sensor springs. In the past,sensors were designed by building and testing prototype hardware until the force-displacementrequirements were met. Prototype springs need to be designed well belo

3、w the elastic limit ofthe material.Using finite element analysis, sensors can be designed to meet forcedisplacementrequirements with acceptable stress levels. The analysis procedure discussed inthis paper has demonstrated the ability to eliminate months of prototyping effort.MSC/ABAQUS has been used

4、 to analyze and design airbag crash sensors.The analysis wasgeometrically nonlinear due to the large deflections of the springs and the contact between theball and springs. Bezier 3-D rigid surface elements along with rigid surface interface (IRS)elements were used to model ball-to-spring contact.Sl

5、ideline elements were used withparallel slideline interface (ISL) elements for spring-to-spring contact.Finite element analysisresults for the force-displacement response of the sensor were in excellent agreement withexperimental results.INTRODUCTIONAn important component of an automotive airbag sys

6、tem is the crash sensor. Various typesof crash sensors are used in airbag systems including mechanical, electro-mechanical, andelectronic sensors. An electro-mechanical sensor (see Figure 1) consisting of a ball and twosprings cased in a plastic housing is discussed in this paper. When the sensor ex

7、periences asevere crash pulse, the ball pushes two springs into contact completing the electric circuitallowing the airbag to fire. The force-displacement response of the two springs is critical indesigning the sensor to meet various acceleration input requirements. Stresses in the sensorsprings mus

8、t be kept below the yield strength of the spring material to prevent plasticdeformation in the springs. Finite element analysis can be used as a predictive engineeringtool to optimize the springs for thedesired force-displacement response while keeping stressesin the springs at acceptable levels.In

9、the past, sensors were designed by building and testing prototype hardware until the forcedisplacementrequirements were met. Using finite element analysis, the number of prototypesbuilt and tested can be significantly reduced, ideally to one, which substantially reduces thetime required to design a

10、sensor. The analysis procedure discussed in this paper hasdemonstrated the ability to eliminate months of prototyping effort.MSC/ABAQUS 1 has been used to analyze and design airbag crash sensors. The analysiswas geometrically nonlinear due to the large deflections of the springs and the contactbetwe

11、en the ball and springs. Various contact elements were used in this analysis includingrigid surface interface (IRS) elements, Bezier 3-D rigid surface elements, parallel slide lineinterface (ISL) elements, and slide line elements. The finite element analysis results were inexcellent agreement with e

12、xperimental results for various electro-mechanical sensors studiedin this paper.PROBLEM DEFINITIONThe key components of the electro-mechanical sensor analyzed are two thin metallic springs(referred to as spring1 and spring2) which are cantilevered from a rigid plastic housing and asolid metallic bal

13、l as shown in Figure 1. The plastic housing contains a hollow tube closed atone end which guides the ball in the desired direction. The ball is held in place by spring1 atthe open end of the tube. When the sensor is assembled, spring1 is initially displaced by theball which creates a preload on spri

14、ng1. The ball is able to travel in one direction only inthis sensor and this direction will be referred to as the x-direction (see the global coordinatesystem shown in Figure 2) in this paper. Once enough acceleration in the x-direction isapplied to overcome the preload on spring1, the ball displace

15、s the spring. As the accelerationapplied continues to increase, spring1 is displaced until it is in contact with spring2. OnceFigure 1. Electro-mechanical automobile crash sensor.contact is made between spring1 and spring2, an electric circuit is completed allowing thesensor to perform its function

16、within the airbag system.FINITE ELEMENT ANALYSIS METHODOLOGYWhen creating a finite element representation of the sensor, the following simplifications canbe made. The two springs can be fully restrained at their bases implying a perfectly rigidplastic housing. This is a good assumption when comparin

17、g the flexibility of the thin springsto the stiff plastic housing. The ball can be represented by a rigid surface since it too is verystiff as compared to the springs. Rather than modeling the contact between the plastichousing and the ball, all rotations and translations are fully restrained except

18、 for the xdirectionon the rigid surface representing the ball. These restraints imply that the housingFigure 2. Electro-mechanical sensor finite element mesh.will have no significant deformation due to contact with the ball. These restraints also ignoreany gaps due to tolerances between the ball and

19、 the housing. The effect of friction betweenthe ball and plastic is negligible in this analysis.The sensor can be analyzed by applying an enforced displacement in the x-direction to therigid surface representing the ball to simulate the full displacement of the ball. Contactbetween the ball and spri

20、ngs is modeled with various contact elements as discussed in thefollowing section. A nonlinear static analysis is sufficient to capture the force-displacementresponse of the sensor versus using a more expensive and time consuming nonlinear transient analysis. Although the sensor is designed with a b

21、all mass and spring stiffness that gives thedesired response to a given acceleration, there is no mass associated with the ball in this staticanalysis. The mass of the ball can be determined by dividing the force required to deflect thesprings by the acceleration input into the sensor.MeshThe finite

22、 element mesh for the sensor was constructed using MSC/PATRAN 2. The solverused to analyze the sensor was MSC/ABAQUS. The finite element mesh including thecontact elements is shown in Figure 2. The plastic housing was assumed to be rigid in thisanalysis and was not modeled. Both springs were modeled

23、 with linear quadrilateral shellelements with thin shell physical properties. The ball was assumed to be rigid and wasmodeled with linear triangular shell elements with Bezier 3-D rigid surface properties.To model contact between the ball and spring1, rigid surface interface (IRS) elements wereused

24、in conjunction with the Bezier 3-D rigid surface elements making up the ball. Linearquadrilateral shell elements with IRS physical properties were placed on spring1 and hadcoincident nodes with the quadrilateral shell elements making up spring1. The IRS elementswere used only in the region of ball c

25、ontact.To model contact between spring1 and spring2, parallel slide line interface (ISL) elementswere used in conjunction with slide line elements. Linear bar elements with ISL physicalproperties were placed on spring1 and had coincident nodes with the shell elements onspring1. Linear bar elements w

26、ith slide line physical properties were placed on spring2 andhad coincident nodes with the shell elements making up spring2.MaterialBoth spring1 and spring2 were thin metallic springs modeled with a linear elastic materialmodel. No material properties were required for the contact or rigid surface e

27、lements.Boundary ConditionsBoth springs were assumed to be fully restrained at their base to simulate a rigid plastichousing. An enforced displacement in the x-direction was applied to the ball. The ball wasfully restrained in all rotational and translational directions with the exception of the xdi

28、rectiontranslation. Boundary conditions for the springs and ball are shown in Figure 2.DISCUSSIONTypical results of interest for an electro-mechanical sensor would be the deflected shape ofthe springs, the force-displacement response of the sensor, and the stress levels in the springs.Results from a

29、n analysis of the electro-mechanical sensor shown in Figure 2 will be used asFigure 3. Electro-mechanical sensor deflected shape.an example for this paper. The deflected shape of this sensor is shown in Figure 3 for fullball travel. Looking at the deflected shape of the springs can provide insight i

30、nto theperformance of the sensor as well as aid in the design of the sensor housing. Stresses in thesprings are important results in this analysis to ensure stress levels in the springs are atacceptable levels. Desired components of stress can be examined through various meansincluding color contour

31、 plots. One of the most important results from the analysis is theforce-displacement response for the sensor shown in Figure 4. From this force-displacementresponse, the force required to push spring1 into contact with spring2 can readily bedetermined. This force requirement can be used with a given

32、 acceleration to determine themass required for the ball. Based on these results, one or more variations of several variablessuch as spring width, spring thickness, ball diameter, and ball material can be updated untilthe force-displacement requirements are achieved within a desired accuracy.A proto

33、type of the sensor shown in Figure 2 was constructed and tested to determine itsactual force-displacement response. Figure 4 shows the MSC/ABAQUS results along withthe experimental results for the force-displacement response of the sensor. There was anexcellent correlation between finite element and

34、 experimental results for this sensor as well asFigure 4. Electro-mechanical sensor force-displacementresponse.for several other sensors examined. Table 1 shows the difference in percent between finiteelement and experimental results including force at preload on spring1, force at spring1-tospring2c

35、ontact, and force at full ball travel for two sensor configurations. Sensor A in Table1 is shown in Figure 1. Sensor B in Table 1 is based on the sensor shown in Figure 2.The sensor model analyzed in this paper was also analyzed with parabolic quadrilateral andbar elements to ensure convergence of t

36、he solution. Force-displacement results converged toless than 1% using linear elements. The stresses in the springs for this sensor converged towithin 10% for the linear elements. The parabolic elements increased solve time by morethan an order of magnitude over the linear elements. With more comple

37、x spring shapes, adenser linear mesh or parabolic elements used locally in areas of stress concentrations wouldbe necessary to obtain more accurate stresses in the springs.%Difference Between FEA and Experimental ResultsSensor 1Force at PreloadForce at spring1-to-spring2contactForce at full balltrav

38、elA+2.0+1.0- 2B+1.6-0.5+1.0Table 1. Comparison of FEA versus Experimental Force-Displacement Responses.Notes: 1. Sensor A results are based on 1 prototype manufactured and tested. Sensor Bexperimental results are based on the average of 20 prototypes manufacturedand tested.2. No experimental data fo

39、r force at full ball travel for Sensor A.3. %Difference=(FEA Result - Experimental Result)/Experimental ResultCONCLUSIONSMSC/ABAQUS has been used to analyze and design airbag crash sensors. The finite elementanalysis results were in excellent agreement with experimental results for several electrome

40、chanicalsensors for which prototypes were built and tested. Using finite element analysis,sensors can be designed to meet force-displacement requirements with acceptable stresslevels. The analysis procedure discussed in this paper has demonstrated the ability toeliminate months of prototyping effort

41、. This paper has demonstrated the power of finiteelement analysis as a predictive engineering tool even with the use of multiple contactelement types.汽車安全氣囊系統(tǒng)撞擊傳感器的有限單元分析摘要：汽車彈簧碰撞傳感器可以利用有限單元分析軟件進行設計，這樣可以大大減少設計時間。該傳感器包括一個球和一個有彈簧在內的塑料套管的外殼。傳感器設計的重要因素是碰撞中的兩個傳感器的力位移響應和傳感器的彈簧壓力。以前傳感器的設計、制作和測試需要滿足力位移原型硬件的

42、要求。彈簧必須遠低于材料的彈性極限而設計。利用有限元分析，傳感器可以被設計為滿足力位移的水平壓力。本文的討論說明利用有限單元分析進行設計可以節(jié)省很多時間。MSC/ABAQUS已經被用于分析和設計安全氣囊碰撞傳感器。彈簧的大撓度和球與彈簧之間的接觸用幾何非線性分析。貝塞爾三維剛性球表面元素和慣性基準系統(tǒng)剛性表面界面元素被用于塑料球與彈簧接觸面的分析?；瑒榆壍婪治霰挥糜趶椈膳c彈簧接觸的平行界面間。有限元傳感器的力位移響應分析結果與實驗結果非常一致。引言汽車安全氣囊系統(tǒng)的重要組成部分是碰撞傳感器。包括機械、電子傳感器在內的碰撞傳感器主要用于各類安全氣囊系統(tǒng)。 本文研究的是由一個球和一個塑料套管和兩個

43、彈簧組成的機電傳感器（見圖1）。當傳感器遇到嚴重的撞擊脈沖，球被推入完成電路連接然后兩個彈簧接觸到消防安全氣囊。這兩個彈簧的力位移設計關鍵是要滿足不同的加速度對傳感器的輸入要求。傳感器的彈簧強度必須保持低于彈簧材料屈服強度，防止彈簧塑性變形。有限元分析，可以作為預測工具，以優(yōu)化工程所需的力和位移反應，同時保持在彈簧壓力可接受的水平。過去傳感器的設計需要不斷地進行制作和測試，直到力位移原型硬件得到滿足需要的條件。利用有限元分析，制作和測試原型的數量大大減少，這大大降低了傳感器設計的時間。本文討論的內容可以表明有限單元分析軟件能夠節(jié)省原型制作時間的能力。MSC/ABAQUS 1已經用于分析和設計安

44、全氣囊碰撞傳感器。對于大撓度的彈簧與球接觸的有限單元分析應是幾何非線性的。各種接觸單元中使用了這個包括硬表面界面分析，例如貝塞爾曲線的三維剛性表面元素，平行線界面元素，以及滑線元素。有限元分析結果與各種機械文獻研究傳感器的實驗結果非常一致。問題的定義機電傳感器的關鍵部件是由兩個以懸臂式存在于硬性塑料外殼和剛性球之間的兩個金屬彈簧組成的。在塑料外殼中包含一個能指導球運動方向的一端封閉的真空管。球在真空管中被彈簧頂在管子的一端。傳感器組裝時彈簧被球頂著產生最初的預緊力。球在傳感器中只能沿著一個方向運動，這個方向被稱為X方向。一旦在X方向的加速度足夠用來克服spring1的預緊力，球就能是彈簧彈開。

45、如果加速度繼續(xù)增加，彈簧1就能直接與彈簧2接觸。一旦彈簧1與彈簧2接觸上，一個電路接通然后啟動安全氣囊的體統(tǒng)。圖1機電汽車碰撞傳感器。有限元分析方法當創(chuàng)建一個傳感器的有限元描述時，剩下的可以被簡化。這兩個彈簧完全的被固定在剛性的塑料外殼中。當一個剛性外殼和薄的彈簧作比較時這是一個很好的假設。當球和彈簧接觸時球可以被表示為一個剛性表面。球和外殼接觸的建模系統(tǒng)中，除了球在X軸移動外殼中的所有的轉動和移動都受到限制。圖2機電傳感器的有限元網格。這些限制意味著如果空間沒有強烈的損壞將不會與球接觸。這些限制忽視了球與外殼之間的公差。在有限元分析中球和塑料外殼的摩擦可以忽略不計。傳感器在X軸的分析，可以用一個剛性表面的的移動表示球的所有移動。下面討論的是球與彈簧間的接觸，和各種不同的接觸原理。一個非線性靜態(tài)分析，足以捕獲耗費大量時間的非線性瞬態(tài)傳感器的力位移響應。雖然該傳感器的設計是由球質量和給定一個加速度回應的彈簧剛度組成的，但是在靜態(tài)分析中沒有球的質量。單元網格球的質量可以被把球擠進傳感器的偏轉力所確定。利用MSC / Patran的2構建傳感