汽車(chē)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 finite element analysis as a predictive engineering tool.The sensors consist of a ball and springs cased in a plastic housing.Two importa

2、nt factors in the design of crash sensors are the force-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-displacement requirements were met. Prototype springs need to be designed well

3、below the elastic limit of the material.Using finite element analysis, sensors can be designed to meet forcedisplacement requirements with acceptable stress levels. The analysis procedure discussed in this paper has demonstrated the ability to eliminate months of prototyping effort.MSC/ABAQUS has be

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

5、contact.Slideline elements were used with parallel slideline interface (ISL) elements for spring-to-spring contact.Finite element analysis results for the force-displacement response of the sensor were in excellent agreement with experimental results.INTRODUCTIONAn important component of an automoti

6、ve airbag system is the crash sensor. Various types of crash sensors are used in airbag systems including mechanical, electro-mechanical, and electronic sensors. An electro-mechanical sensor (see Figure 1) consisting of a ball and two springs cased in a plastic housing is discussed in this paper. Wh

7、en the sensor experiences a severe crash pulse, the ball pushes two springs into contact completing the electric circuit allowing the airbag to fire. The force-displacement response of the two springs is critical in designing the sensor to meet various acceleration input requirements. Stresses in th

8、e sensor springs must be kept below the yield strength of the spring material to prevent plastic deformation in the springs. Finite element analysis can be used as a predictive engineering tool to optimize the springs for the desired force-displacement response while keeping stresses in the springs

9、at acceptable levels.In the past, sensors were designed by building and testing prototype hardware until the forcedisplacement requirements were met. Using finite element analysis, the number of prototypes built and tested can be significantly reduced, ideally to one, which substantially reduces the

10、 time required to design a sensor. The analysis procedure discussed in this paper has demonstrated the ability to eliminate months of prototyping effort. MSC/ABAQUS 1 has been used to analyze and design airbag crash sensors. The analysis was geometrically nonlinear due to the large deflections of th

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

12、were in excellent agreement with experimental results for various electro-mechanical sensors studied in 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 pla

13、stic housing and a solid metallic ball as shown in Figure 1. The plastic housing contains a hollow tube closed at one end which guides the ball in the desired direction. The ball is held in place by spring1 at the open end of the tube. When the sensor is assembled, spring1 is initially displaced by

14、the ball which creates a preload on spring1. The ball is able to travel in one direction only in this sensor and this direction will be referred to as the x-direction (see the global coordinate system shown in Figure 2) in this paper. Once enough acceleration in the x-direction is applied to overcom

15、e the preload on spring1, the ball displaces the spring. As the acceleration applied 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

16、 allowing the sensor to perform its function within the airbag system.FINITE ELEMENT ANALYSIS METHODOLOGYWhen creating a finite element representation of the sensor, the following simplifications can be made. The two springs can be fully restrained at their bases implying a perfectly rigid plastic h

17、ousing. This is a good assumption when comparing the flexibility of the thin springs to the stiff plastic housing. The ball can be represented by a rigid surface since it too is very stiff as compared to the springs. Rather than modeling the contact between the plastic housing and the ball, all rota

18、tions and translations are fully restrained except for the xdirection on 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 ig

19、nore any gaps due to tolerances between the ball and the housing. The effect of friction between the ball and plastic is negligible in this analysis.The sensor can be analyzed by applying an enforced displacement in the x-direction to the rigid surface representing the ball to simulate the full disp

20、lacement of the ball. Contact between the ball and springs is modeled with various contact elements as discussed in the following section. A nonlinear static analysis is sufficient to capture the force-displacement response of the sensor versus using a more expensive and time consuming nonlinear tra

21、nsient analysis. Although the sensor is designed with a ball mass and spring stiffness that gives the desired response to a given acceleration, there is no mass associated with the ball in this static analysis. The mass of the ball can be determined by dividing the force required to deflect the spri

22、ngs by the acceleration input into the sensor.MeshThe finite element mesh for the sensor was constructed using MSC/PATRAN 2. The solver used to analyze the sensor was MSC/ABAQUS. The finite element mesh including the contact elements is shown in Figure 2. The plastic housing was assumed to be rigid

23、in this analysis and was not modeled. Both springs were modeled with linear quadrilateral shell elements with thin shell physical properties. The ball was assumed to be rigid and was modeled with linear triangular shell elements with Bezier 3-D rigid surface properties.To model contact between the b

24、all and spring1, rigid surface interface (IRS) elements were used in conjunction with the Bezier 3-D rigid surface elements making up the ball. Linear quadrilateral shell elements with IRS physical properties were placed on spring1 and had coincident nodes with the quadrilateral shell elements makin

25、g up spring1. The IRS elements were used only in the region of ball contact.To model contact between spring1 and spring2, parallel slide line interface (ISL) elements were used in conjunction with slide line elements. Linear bar elements with ISL physical properties were placed on spring1 and had co

26、incident nodes with the shell elements on spring1. Linear bar elements with slide line physical properties were placed on spring2 and had coincident nodes with the shell elements making up spring2.MaterialBoth spring1 and spring2 were thin metallic springs modeled with a linear elastic material mode

27、l. No material properties were required for the contact or rigid surface elements.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

28、 all rotational and translational directions with the exception of the xdirection translation. 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 of the springs, the force-displacement

29、 response of the sensor, and the stress levels in the springs. Results from an 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 full ba

30、ll travel. Looking at the deflected shape of the springs can provide insight into the performance of the sensor as well as aid in the design of the sensor housing. Stresses in the springs are important results in this analysis to ensure stress levels in the springs are at acceptable levels. Desired

31、components of stress can be examined through various means including color contour plots. One of the most important results from the analysis is the force-displacement response for the sensor shown in Figure 4. From this force-displacement response, the force required to push spring1 into contact wi

32、th spring2 can readily be determined. This force requirement can be used with a given acceleration to determine the mass required for the ball. Based on these results, one or more variations of several variables such as spring width, spring thickness, ball diameter, and ball material can be updated

33、until the force-displacement requirements are achieved within a desired accuracy.A prototype of the sensor shown in Figure 2 was constructed and tested to determine its actual force-displacement response. Figure 4 shows the MSC/ABAQUS results along with the experimental results for the force-displac

34、ement response of the sensor. There was an excellent correlation between finite element and 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 finite element

35、 and experimental results including force at preload on spring1, force at spring1-tospring2 contact, and force at full ball travel for two sensor configurations. Sensor A in Table 1 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

36、paper was also analyzed with parabolic quadrilateral and bar elements to ensure convergence of the solution. Force-displacement results converged to less than 1% using linear elements. The stresses in the springs for this sensor converged to within 10% for the linear elements. The parabolic elements

37、 increased solve time by more than an order of magnitude over the linear elements. With more complex spring shapes, a denser linear mesh or parabolic elements used locally in areas of stress concentrations would be necessary to obtain more accurate stresses in the springs.%Difference Between FEA and

38、 Experimental ResultsSensor 1Force at PreloadForce at spring1-to-spring2contactForce at full balltravelA+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 Bexperimenta

39、l results are based on the average of 20 prototypes manufacturedand tested.2. No experimental data for 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 finit

40、e element analysis results were in excellent agreement with experimental results for several electromechanical sensors for which prototypes were built and tested. Using finite element analysis, sensors can be designed to meet force-displacement requirements with acceptable stress levels. The analysi

41、s procedure discussed in this paper has demonstrated the ability to eliminate months of prototyping effort. This paper has demonstrated the power of finite element analysis as a predictive engineering tool even with the use of multiple contact element types.汽車(chē)安全氣囊系統(tǒng)撞擊傳感器的有限單元分析摘要：汽車(chē)彈簧碰撞傳感器可以利用有限單元分析

42、軟件進(jìn)行設(shè)計(jì)，這樣可以大大減少設(shè)計(jì)時(shí)間。該傳感器包括一個(gè)球和一個(gè)有彈簧在內(nèi)的塑料套管的外殼。傳感器設(shè)計(jì)的重要因素是碰撞中的兩個(gè)傳感器的力位移響應(yīng)和傳感器的彈簧壓力。以前傳感器的設(shè)計(jì)、制作和測(cè)試需要滿足力位移原型硬件的要求。彈簧必須遠(yuǎn)低于材料的彈性極限而設(shè)計(jì)。利用有限元分析，傳感器可以被設(shè)計(jì)為滿足力位移的水平壓力。本文的討論說(shuō)明利用有限單元分析進(jìn)行設(shè)計(jì)可以節(jié)省很多時(shí)間。MSC/ABAQUS已經(jīng)被用于分析和設(shè)計(jì)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(zhǔn)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?dòng)軌道分析被用于彈簧與彈簧接觸的

43、平行界面間。有限元傳感器的力位移響應(yīng)分析結(jié)果與實(shí)驗(yàn)結(jié)果非常一致。引言汽車(chē)安全氣囊系統(tǒng)的重要組成部分是碰撞傳感器。包括機(jī)械、電子傳感器在內(nèi)的碰撞傳感器主要用于各類(lèi)安全氣囊系統(tǒng)。 本文研究的是由一個(gè)球和一個(gè)塑料套管和兩個(gè)彈簧組成的機(jī)電傳感器（見(jiàn)圖1）。當(dāng)傳感器遇到嚴(yán)重的撞擊脈沖，球被推入完成電路連接然后兩個(gè)彈簧接觸到消防安全氣囊。這兩個(gè)彈簧的力位移設(shè)計(jì)關(guān)鍵是要滿足不同的加速度對(duì)傳感器的輸入要求。傳感器的彈簧強(qiáng)度必須保持低于彈簧材料屈服強(qiáng)度，防止彈簧塑性變形。有限元分析，可以作為預(yù)測(cè)工具，以優(yōu)化工程所需的力和位移反應(yīng)，同時(shí)保持在彈簧壓力可接受的水平。過(guò)去傳感器的設(shè)計(jì)需要不斷地進(jìn)行制作和測(cè)試，直到力位

44、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(cè)試原型的數(shù)量大大減少，這大大降低了傳感器設(shè)計(jì)的時(shí)間。本文討論的內(nèi)容可以表明有限單元分析軟件能夠節(jié)省原型制作時(shí)間的能力。MSC/ABAQUS 1已經(jīng)用于分析和設(shè)計(jì)安全氣囊碰撞傳感器。對(duì)于大撓度的彈簧與球接觸的有限單元分析應(yīng)是幾何非線性的。各種接觸單元中使用了這個(gè)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(jié)果與各種機(jī)械文獻(xiàn)研究傳感器的實(shí)驗(yàn)結(jié)果非常一致。問(wèn)題的定義機(jī)電傳感器的關(guān)鍵部件是由兩個(gè)以懸臂式存在于硬性塑料外殼和剛性球之間的兩個(gè)金屬?gòu)椈山M成的。在塑料外殼中包含一個(gè)能指導(dǎo)球運(yùn)動(dòng)方向的一端封閉

45、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(shí)彈簧被球頂著產(chǎn)生最初的預(yù)緊力。球在傳感器中只能沿著一個(gè)方向運(yùn)動(dòng)，這個(gè)方向被稱(chēng)為X方向。一旦在X方向的加速度足夠用來(lái)克服spring1的預(yù)緊力，球就能是彈簧彈開(kāi)。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(gè)電路接通然后啟動(dòng)安全氣囊的體統(tǒng)。圖1 機(jī)電汽車(chē)碰撞傳感器。有限元分析方法當(dāng)創(chuàng)建一個(gè)傳感器的有限元描述時(shí)，剩下的可以被簡(jiǎn)化。這兩個(gè)彈簧完全的被固定在剛性的塑料外殼中。當(dāng)一個(gè)剛性外殼和薄的彈簧作比較時(shí)這是一個(gè)很好的假設(shè)。當(dāng)球和彈簧接觸時(shí)球可以被表示為一個(gè)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(dòng)外殼中的所有的轉(zhuǎn)動(dòng)和移動(dòng)都受到限制。圖2 機(jī)電傳感器的有限元網(wǎng)格。這些限制意味著如果空間沒(méi)有強(qiáng)烈的損壞將不會(huì)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(jì)。傳感器在X軸的分析，可以用一個(gè)剛性表面的的移動(dòng)表示球的所有移動(dòng)。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(gè)非線性靜態(tài)分析，足以捕獲耗費(fèi)大量時(shí)間的非線性瞬態(tài)傳感器的力位移響應(yīng)。雖然該傳感器的設(shè)計(jì)是由球質(zhì)量和給定一個(gè)加速度回應(yīng)的彈簧剛度組成的，但是在靜態(tài)分析中沒(méi)有球的質(zhì)量。單元網(wǎng)格球的質(zhì)量可以被把球擠進(jìn)傳感器的偏轉(zhuǎn)力所確定。利用MSC / Patra