UN R129侧碰数值模拟的3岁儿童损伤风险研究

根据联合国欧洲经济委员会制定的UN R129法规儿童约束系统（CRS）台车侧面碰撞条件,提出了2种台车侧面碰撞仿真试验方法,并验证了其可行性。基于该试验方法,采用Q3儿童假人,建立3种不同CRS（五点式-成人安全带固定（三点式CRS）,五点式-ISOFIX固定,前护板型-成人安全带固定）的侧面碰撞数值分析模型。分析了儿童乘员的运动学响应和头、颈部及胸部的损伤物理参数。结果显示：儿童乘员在不同类型的CRS中的运动学响应不同。ISOFIX固定条件下儿童头部损伤风险较大,除三点式CRS约束条件下的儿童乘员损伤物理参数接近耐受极限值外,其他2种工况下的儿童乘员的胸部合成加速度（3ms）和上颈部弯矩值均超过儿童乘员耐受极限值,可见在侧面碰撞中儿童乘员的胸部和颈部损伤风险较大。     

基于MADYMO的3岁儿童汽车安全座椅的安全性影响参数研究

儿童汽车安全座椅的安全性至关重要,必须通过相关的标准碰撞测试。基于MADYMO软件的虚拟碰撞技术,可以帮助设计师在产品设计阶段就清晰了解影响座椅主要设计参数对安全性的影响,从而提高设计的成功率。基于MADYMO,分别进行了不同座椅摩擦系数、安全带肩位位置、安全带的刚度以及座椅刚度等情况下的虚拟碰撞,并对测试结果进行了详细的分析。     

KEY TECHNIQUES OF MULTI-BODY MODELING OF OCCUPANT RESTRAINT SYSTEM OF VEHICLE SIDE IMPACT

Based on multi-body dynamics, the simulation models of auto-side structures and occupant's dynamic responses are set up, using the occupant injury simulation software MADYMO3D. These models include auto-body structure, impact barrier, seat and dummy. Definitions of multi-body and joints and dynamics properties of joints based on FE combination models, of model setup are introduced. Kelvin element of MADYMO is introduced to show the force action between non-adjoining rigid bodies, too. Then all examples of the methods mentioned are given. By the comparison of simulation and real test, the contract curves between simulation and real test for main structures and biology mechanics properties of dummy are obtained. The result shows the accuracy and validity of the models.     

汽车碰撞仿真与设计的最新进展和发展趋势

介绍了汽车碰撞仿真与设计的最新进展和发展趋势。内容包括作为模拟手段的计算程序的最新进展,新的缓冲材料的应用和模拟,大规模并行程序的编制和性能的增加,侧撞障碍物模拟,乘客模型（假人）,生物人体部件模型,碰撞仿真技术扩展应用到设备跌落试验和火星着陆舱的缓冲等。通过实例和试验,介绍了１０年来碰撞仿真技术的进展情况。     

An investigation in crashworthiness evaluation of aircraft seat cushions at extreme ranges of temperature

This paper obtains a Mathematical Dynamic Model (MADYMO) for occupant lumbar load evaluation under CFR Part 23 and 25 at extreme ranges of temperature. The validation of results is performed by full scale sled test results. Aircraft industries are using viscoelastic polyurethane foams as seat cushion. Visco-elastic foams bring not only more comfort to the passengers in long term sitting but it also maintains more safety during unpredicted crashes and hard landings. Aircraft seat cushions are exposed to varying temperature ranges during their life time. This fact has motivated aircraft industries to evaluate the seat cushion dynamic behavior at extreme ranges of temperatures in addition to what is mentioned in Federal Aviation Administration (FAA) Regulations at room temperature. This research provides a methodology based on simulation and modeling to eliminate, or at least, minimize the number of full scale dynamic sled tests defined by regulations for aircraft seats at extreme ranges of temperature.     

The effect of leg fracture level and vehicle front-end geometry on pedestrian knee injury and response

In this study a MADYMO (mathematical dynamic modelling) model has been used to identify the influence of leg fracture on the injuries sustained by the pedestrian during front end impact with a vehicle. A factorial study of a MADYMO pedestrian and vehicle model are used to investigate the effect of different leg fracture tolerances, geometry, and vehicle compliance on the criteria measured in the European Enhanced Vehicle-safety Committee (EEVC) pedestrian safety tests. These criteria include knee bending, knee shear response, and lower leg bone (tibia) acceleration. The main study examines the spread of typical values of lower limb tolerance based on reported literature and contrasts the response of weaker, low-strength bones, normal tolerance, and limbs which do not fracture. Results show that knee bending angles and therefore ligament strains are significantly increased when fracture does not occur, and are decreased in bones exhibiting a low-strength response. Bone fracture tolerance is shown to be a significant parameter influencing knee bending. The parameters are compared to show that knee shear is significantly influenced by vehicle bumper compliance and that both criteria are heavily influenced by bumper height. Vehicles with more aggressive geometry, higher bumpers, and larger bumper lead were considered for comparative purposes.     

航空座椅动态冲击仿真方法研究

以航空座椅和仿真假人为研究对象,建立座椅有限元模型和HybridⅡ型假人多刚体系统模型,采用动态大变形非线性有限元分析技术和多刚体动力学方法,模拟了航空座椅和假人在冲击中的响应过程,评估了航空座椅结构的动态冲击性能,并与试验结果进行了对比分析,验证所建立的有限元模型的正确性.这种方法可降低产品研发过程中的试验费用,缩短设计周期,具有很重要的工程意义.     

轿车乘员约束系统的试验验证及参数优化

应用MADYMO模型进行虚拟试验或数值仿真是乘员约束系统开发流程中重要的方式。为得到可靠的计算结果,必需遵循规范的验证流程。详细介绍了MADYMO正面碰撞约束系统的建立和试验验证的流程。基于验证模型,进行了试验设计、参数灵敏度分析、响应面模型分析以及优化设计。优化设计结果使乘员受重伤的概率下降4.2%。在实际的工程应用中,利用MADYMO模拟可有效匹配约束系统的设计参数,达到稳健可靠的乘员保护效果。     

汽车前部与行人下肢的冲击实验评价方法研究

利用MADYMO软件数据库中的下肢冲击器模型进行了汽车碰撞计算机仿真，并利用一个生物逼真度较好的行人模型进行了汽车与行人碰撞计算机仿真。将仿真结果除以相应的技术要求值得到各自的风险系数。依照风险系数的综合评价，可对不同汽车前部结构对行人下肢的碰撞性能进行排序。排序结果表明，由下肢冲击器实验仿真得到的结果和由汽车与行人碰撞仿真得到的结果基本相符。将EEVC制订的下肢冲击器实验评价方法得到的实验结果按损伤风险系数进行排序的方法，可用来进行汽车前部结构对行人下肢碰撞安全性能好坏的评价，但下肢冲击器实验依然存在一些不足需要进行政进．     

汽车低速追尾碰撞中乘员动力学响应和颈部损伤的仿真研究

利用MADYMO仿真分析软件建立了包括BioRIDⅡ假人、座椅和安全带在内的追尾碰撞模型，研究了在追尾碰撞中，座椅特性和乘员位置对乘员动力学响应和颈部损伤的影响。仿真分析结果表明，头枕位置、靠背刚度、靠背倾角调节器特性和乘员乘坐姿势对乘员头颈部的动力学响应有很大影响，通过合理的座椅设计可以显著降低颈部损伤风险。     

A study on the influence of the seat and head restraint foam stiffnesses on neck injury in low speed offset rear impacts

Soft tissue neck injury (STNI) is thought to be related to automotive seat characteristics, and it is important to know how the stiffness of the seatback and head restraint foam affect the occupant’s motions in low speed rear impacts. The combined MADYMO(MAthematical DYnamic MOdel, TNO) 50th percentile facet male human body model with a detailed neck model was selected for this analysis. In order to determine the relationship between the occupant’s motions and seatback and head restraint foam stiffnesses, 40% offset rear impact simulations were performed by changing the stiffness of seatback and head restraint. Simulated results show that the maximum acceleration of head and trunk would tend to increase with those stiffnesses. Increased stiffness of the seatback and head restraint resulted in increased ligament and disc forces. On the other hand a proper combination of seatback and head restraint stiffness can reduce a possible neck injury. It is clear that an appropriate combination of stiffnesses between seatback and head restraint allows to minimize a neck injury.     

An experimental study on the axial collapse characteristics of hat and double hat shaped section members at various velocities

In this study, the axial collapse tests were performed under either static (or quasi-static) or impact loads with several collapse velocities based on the expectation that para-closed sections of the front-end side members (spot welded hat and double hat shaped section members) would show quite different collapse characteristics from those for seamless section. The test results showed that both of the hat and double hat shaped section members failed in the stable sequential collapse mode in the static or quasi-static collapse tests, while the double hat shaped section members underwent the unstable collapse mode especially when the impact velocity is high. The mean collapse loads in the hat shaped section members increase with collapse velocity for all the cases of the static, quasi-static, and impact collapse tests. In the double hat shaped section members, however, the mean collapse loads decrease with increase in collapse velocity in the impact tests.     

基于C-IASI规程下台车侧面碰撞模拟试验方法研究

为了节约开发成本,减少实车碰撞试验次数,基于中国保险汽车安全指数(China Insurance Automotive Safety Index,C-IASI)中侧面碰撞试验规程,使用带有副台车的加速台车设备,通过主台车复现整车试验假人胸部中间肋骨位置对应车门内钣金Y方向加速度,副台车通过蜂窝铝调节复现车辆非被撞侧B柱Y方向加速度,以此实现台车侧碰模拟试验,并在某车型上进行验证。结果表明:SID-IIs假人躯干伤害与碰撞结果的接近度在90%以上,且仅一次即满足对标要求;基于加速台车和蜂窝铝调节开发的侧面台车试验方法,能够更好代替实车进行侧面约束系统开发试验。     

Monitoring mechanical impedance of the thorax with compression and decompression cardiopulmonary resuscitation device

To reduce the complications of cardiopulmonary resuscitation (CPR) and increase its effectiveness, the quality of CPR must be measured and feedback provided to the CPR practitioner. Although CPR ancillary devices that attach sensors to measure the compression frequency and depth have been used, these devices did not previously capture the parameters necessary to determine whether the compression position was appropriate, or whether the thorax was deformed by fracture or other causes. In this study, we proposed a system for measuring the mechanical impedance of a patient’s thorax using a load cell and an accelerometer, incorporated into a CPR ancillary device; the mechanical impedance measurements enabled monitoring of the characteristics and deformations of the thorax during in vitro experiments using dummies, and in an animal experiment using two pigs. When CPR was performed, sensors attached to the CPR assist device measured the compression force and movement, and then the single frequency elements of force and velocity at chest compression frequency were calculated. The mechanical impedance can be determined by calculating the ratio of the obtained force to the velocity. Dummies with different elastic moduli show differences in mechanical impedance. In the animal experiment using pigs, the mechanical impedance of the pig’s thorax steadily decreased in response to successive chest compressions. The mechanical impedance system proposed in this study may be useful in the development of new methods to rapidly measure the mechanical properties of the human body or other complex structures.

     

某低配轿车驾驶员头部保护方案优化设计

对未配备气囊,采用普通三点式安全带的某低配轿车驾驶员头部的保护方案进行了研究。通过MADYMO仿真计算与DOE试验设计相结合的方法,对低配轿车驾驶员头部保护进行优化设计,通过调整织物延伸率、调节安全带限力等级,得到理想的安全带优化参数,物理滑台试验验证结果显示该优化方案有效降低了驾驶员头部伤害,满足了法规要求。该项目优化方案切实可行,为其他类似车型乘员约束系统优化提供了有效借鉴。     

基于仿真的车身侧面碰撞关键区域变形反求

侧面碰撞中,汽车与假人接触的关键区域的变形历程对于研究侧面碰撞中假人的保护很重要但基本上难以通过测量得到。提出用仿真验证的方法反求侧面碰撞关键区域的变形时间历程。根据中国新车星级评价规程(CNCAP)侧面碰撞试验测量得到假人各部位的响应、侧面碰撞关键区域最终的变形以及碰撞动画,通过调整建立的侧面碰撞仿真模型中关键区域的变形时间历程,最终使仿真计算结果与试验结果接近一致。     

Concurrent validation of magnetic and inertial measurement units in estimating upper body posture during gait

We assessed the concurrent validity of commercially available magnetic and inertial measurement units (MIMUs) for estimating mean postural angles for head flexion, thorax flexion and shoulder girdle elevation during gait in seven healthy individuals. Postural angles estimated with the MIMUs were compared with angles calculated using marker data from a gold standard motion capture system. Coefficients of determination of mean postural angles between measurement systems were 0.82 for head flexion, 0.58 for thorax flexion, and 0.77 for shoulder girdle elevation. Bland–Altman analysis showed good agreement between measurement systems. Intraclass correlation coefficients were 0.9 for head flexion, 0.73 for thorax flexion, and 0.87 for shoulder girdle elevation. Root mean square errors were less than 3° between measurement systems for all body segments. The present findings suggest that the MIMUs tested in this study are valid for estimating head flexion, thorax flexion and shoulder girdle elevation during gait.     

Improved mathematical model of the wear of the cup articular surface in hip joint prostheses and comparison with retrieved components

This paper presents an analytical model of the cobalt-based alloy-ultra-high molecular weight polyethylene (UHMWPE) wear coupling. Based on a previous model in which the cup wear volume over a gait cycle (WG) was calculated under the simplifying assumption of an ideal rigid coupling, the current version proposes a more realistic wear simulation. All three components of the hip loading force were considered for the contact pressure calculation and all three components of the hip motion were taken into account for the sliding distance calculation. The contact pressure distribution was calculated on the basis of the Hertzian theory for the elastic contact of two bodies with non-conforming geometrical shapes. The wear factor was taken from hip simulator wear tests. The calculated WG is 67 x 10(-6) mm3 for a standard reference patient. The parametric model simulations show that WG increases linearly with the patient weight, femoral head diameter and surface roughness. It increases non-linearly to a maximum and decreases to an asymptotic value with increasing cup/head clearance and with cup isotropic elastic modulus. The cup orientation in the pelvis affects only slightly the total amount of WG whereas it is the dominant factor affecting the shape of the wear distribution. The iso-wear maps show paracentral patterns at low cup inclination angles and marginal patterns at higher inclination angles. The maximum wear depth is supero-posterior when the cup is in neutral alignment and supero-anterior at increasing anteversion angles. Complex patterns with a combination of paracentral and marginal wear were obtained at specific clearance values and cup orientations. The results of the simulations are discussed in relation to the wear distribution measured on the articular surface of 12 UHMWPE components retrieved from failed hip joint prostheses, after a period of in situ functioning.     

Nanotribometer: a new instrument for nano-scale to micron-scale friction and wear measurements

A nanotribometer has been developed for exploring friction and wear in nanometer to micrometer diameter sliding contacts. The nanotribometer is based on a scanning force microscope design developed at NIST. Interferometers and capacitance gages are used in a closed-loop digital control system to accurately determine and control the position and motion of the sample. The force head can measure continuous changes in both normal and lateral forces over three orders of magnitude within the range of nN to mN. This large dynamic range is achieved through the use of a PIN diode position-sensitive-detector. High-cycle wear tests on polycarbonate, friction measurements on mica, and continuous indentations on polyethylene illustrate the range of applications. This revised version was published online in June 2006 with corrections to the Cover Date.     

Lateral performance evaluation of laser micromachining by high precision optical metrology and image analysis

Today several techniques are available for micro-manufacturing. Yet, it is difficult to assess the precision and lateral X,Y accuracy of these techniques. The available accuracy information is usually based on specifications given by machine suppliers. This information is based on in-house laboratory tests performed by dedicated machine operators and within an adapted environment. In practice, the accuracy is likely to vary due to environmental conditions, materials and operator skills. In order to check the specifications in realistic environments the EUMINAfab infrastructure consortium initiated a set of independent high precision onsite verification tests on different laser micromachining installations. In addition to providing performance verification, it gave the participating partners real capability information of their equipment and possibilities to improve machining performance to a higher level. In this study a comprehensive verification test was designed and carried out by using a high precision metrology method for 2D measurements based on subpixel resolution image analysis. This methodology improved our knowledge of the capabilities of three laser micromachining installations, and showed that specifications at single micron levels are hard to obtain.