基于虚拟试验场技术的汽车侧面碰撞仿真分析

以显式动态有限元理论为基础,基于虚拟试验场(VPG)技术,对汽车侧面碰撞进行计算机仿真研究.在VPG环境下,对整车CAD模型划分了单元网格,定义了单元类型和材料参数,创建了焊点、接触和约束.参照ECE R95安全法规,加载移动壁障车模型,并设置碰撞初始条件.调用显示动态有限元软件LS-DYNA对仿真模型进行计算求解,得到汽车碰撞过程中应力分布和车身变形云图,以及碰撞能量和加速度曲线.通过仿真可预测出汽车碰撞的安全性能,从而为汽车质量的评价提供了依据.     

基于耐撞性拓扑优化的汽车关键安全件设计

将耐撞性拓扑优化方法应用到车辆实际开发过程中,阐述了基于LS-DYNA显式有限元算法的耐撞性拓扑优化方法,并给出其迭代求解的数学模型。结合该方法,对某车辆的门槛梁进行40%偏置碰撞和侧面碰撞的并行拓扑优化,根据优化结果的材料分布情况进行了工程诠释。在整车碰撞有限元模型中对工程诠释结果进行了验证,结果表明：耐撞性拓扑优化方法行之有效,且拓扑优化结果使得车辆的碰撞性能有一定的提高。     

汽车安全气囊ECU共振分析

安全气囊ECU的主要功能是用于检测碰撞加速度信号,控制安全气囊的起爆时间。为保证ECU安装位置的共振性能,防止由于共振而产生误起爆,在整车开发过程中要求安全气囊ECU安装支架必须满足一定的动刚度设计要求。文中利用Altair/HyperMesh软件进行有限元建模,通过RADIOSS求解器对某车型ECU安装支架进行动刚度分析计算,并结合试验结果进行验证使其达到设计要求。     

正面40%碰撞模拟技术在汽车设计中的应用

以某车型为载体,针对C-NCAP及国家法规的ODB工况要求,利用虚拟样车分析技术,建立完成整车碰撞仿真分析有限元模型,求解计算并将仿真分析结果与偏置碰撞试验进行对比验证,确认了仿真分析方法的可行性和准确性。通过虚拟仿真设计与试验设计相结合,在虚拟仿真阶段对车辆的结构安全性能进行改进优化,大大减少了实车碰撞次数,缩短了开发周期,提高了车辆结构安全性能,并降低了汽车的设计成本。     

轿车结构耐撞性分析与改进

根据汽车碰撞模型,在整车仿真平台上,提出改善汽车正面撞击耐撞性汽车吸能结构改进方案,并对改进后结构进行碰撞仿真分析,通过与原结构仿真结果及实车碰撞试验结果对比,验证结构改进对改善汽车碰撞安全性能有效性,探索出一条能够改善汽车正面撞击的结构耐撞性有效途径.     

基于ABAQUS的显式动力学分析方法研究

显式动力学(The Explicit Dynamic)是针对隐式求解器的一个补充,其分析方法对于求解广泛、各类非线性结构力学问题是一个非常有效的工具,显式方法中的单个增量步取决于模型的最高固有频率,与持续时间、载荷类型无关。ABAQUS/Explicit主要用于碰撞、接触以及失效分析。探讨了ABAQUS显式动力学的基本理论、求解的问题,对显示动力学分析方法中的求解算法、稳定时间极限和能量平衡问题进行研究,给出了显示动力学分析的一般性分析方法。通过案例验证了该方法的可行性,应用该方法可有效解决实际工业生产中的碰撞问题、复杂的接触问题以及复杂的后屈曲问题,可为显式动力学分析方法应用于工程实践奠定理论与方法基础。     

基于正面耐撞性仿真的轿车车身材料轻量化研究

以某轿车为研究对象,运用显式有限元理论,建立整车有限元模型,基于“汽车正面碰撞乘员保护设计规则(CMVDR294)”的耐撞安全性仿真,从满足整车正面耐撞安全性能的角度,分别采用高强钢和铝合金对车身主要覆盖件进行轻量化研究,使车身减质量分别达9.31 kg和53.10 kg,减质量效果达到11.30%和64.50%。对整车变形、整车与刚性墙的碰撞力、运动速度和加速度、主要零部件吸能等方面进行分析、评价,数值仿真验证了轻量化方案的可行性。     

基于SolidWorks和LS-DYNA的汽车保险杠低速碰撞仿真研究

以显式动态有限元理论为基础,对汽车保险杠的碰撞进行了计算机模拟研究。用Solidworks建立了汽车保险杠与刚性墙低速碰撞的仿真模型,用ansys对模型进行前处理,调用LS-DYNA求解器进行求解,最后用LS-PROPOSTD做了后处理,得到了保险杠的位移、动能、内能和应力等变化情况,分析结果显示保险杠能吸收大部分能量,对前围件起到了较好的保护作用。     

基于仿真分析的汽车B柱侧面碰撞性能设计

汽车车身B柱是侧面碰撞过程中最重要的载荷承载部件,其变形模式和能量吸收对其入侵速度和入侵量有重要影响,并最终影响乘员损伤。针对某车型B柱的侧面碰撞性能设计,首先建立了整车侧面碰撞仿真模型,然后采用从整车模型中提取B柱子系统模型的方法,从而大大提高计算效率,并对子系统模型进行了验证,基于该子系统模型完成了车身B柱的侧面碰撞性能优化设计。工程算例表明,该方法在B柱的性能优化设计方面具有较强的工程实用性。     

汽车碰撞计算机仿真中的子循环法分析

显式有限元分析中采用子循环法能够显著的提高计算效率。在对几种常用子循环法的稳定性和精度进行验证分析的基础上,提出了新的可应用于汽车碰撞过程仿真的子循环算法,该方法通过对汽车碰撞仿真模型中大量存在的刚性连接进行特殊处理以保证子循环方法的稳定性,其计算误差通过引入阻尼进行消除。自行开发了汽车碰撞子循环法分析程序,算例证明该方法在保证计算精度的前提下可大大提高计算效率。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

交通荷载作用下桥梁结构参数识别方法

应用动力节点加载法,将作用在桥梁上的交通荷载转化为等效节点荷载,再用两步构造法识别结构物理参数.第1步,用Newmark-β方法变换结构运动方程,并用结构的加速度响应求得变换空间内的位移、速度和加速度响应;第2步,基于最小二乘原理,构造出变换空间内求解结构参数的递推式,进行结构物理参数识别.数值模拟结果表明,在交通荷载作用下,该方法能够快速、准确地进行桥梁结构参数识别.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

RLS and LMS blind adaptive multi-user detection method and comparison in acoustic communication

RLS and LMS blind adaptive multi-user detection algorithm and multi-user detector was proposed to solve the problem of multi-user signal detection problem encountered in underwater acoustic communication networks.In simulation analysis,RLS and the LMS blind adaptive multi-user detector were designed and tested for synchronous and asynchronous multi-user communication process.The results of SIR comparison and MMSE comparison show that,both of the two methods can realize blind adaptive detection when any user change in multi-user communication,during this process,the training communication sequences are not needed.The RLS algorithm has about 5 dB higher in SIR compared with LMS algorithm,and the convergence velocity of RLS algorithm is also higher than LMS algorithm when the communication users change.RLS algorithm has better ability in multi-user detection than that of LMS algorithm,and it has great attraction and guiding significance for solving the problem of multiple access interference(MAI) in multi-user communication.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...