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1.
根据输电线路张力放线施工中牵引走板与放线滑车的实际接触运动关系,构建了由钢丝绳、牵引走板、导线及双滑车等部件组成的多体运动系统,提出了符合实际情况的钢丝绳、导线、牵引走板等与双滑车的接触判断方法.基于有限质点法理论,结合部件间的空间位置关系,给出了单元节点的作用力表达式,并通过罚函数法给出了不同接触状态下牵引走板对滑车的接触力,形成了可分析牵引走板与双滑车结构接触碰撞的动力计算方法.根据张力放线施工实际情况,计算分析了牵引走板与双滑车结构接触过程中的滑车载荷、摆动角度的变化,并针对悬挂长度、走板厚度等施工因素,总结了牵引力、最大接触力、滑车载荷、摆动幅度等参数对系统安全的影响.本文提出的计算方法可指导工程中牵引走板与滑车的结构设计及施工安装,为输电线路放线施工提供技术参考.  相似文献   

2.
李剑锋  张玉茹  张启先 《机器人》1999,21(6):407-414
与灵巧抓持相比,Power抓持可承受较大的外部载荷 ,能够更稳定地抓持物体.但由于抓持机构与物体间的约束较多,且接触点可出现在抓持机 构中活动度有限的构件上,因此不能采用已有的适用于灵巧抓持的接触力分解方法对其接触 力进行分解.本文在对一类Power抓持机构的结构特征进行分析的基础上,适当地建立了接 触坐标系和物体坐标系.通过对接触力空间进行分解,给出了抓持接触力分解的一般表达式 .并根据该表达式,建立了此类Power抓持的外部载荷与关节力矩及接触力之间的显函数关 系.  相似文献   

3.
为研究轮轨滚动接触疲劳(Rolling Contact Fatigue,RCF)载荷对铁轨表面裂纹应力强度系数的影响,以UIC60铁轨轮廓尺寸为依据建立轮轨接触的三维有限元模型,通过改变RCF载荷大小、轮轨表面摩擦因数和接触中心位置等轮轨接触的输入参数,计算铁轨表面接触裂纹尖端的应力强度系数,分析RCF载荷对铁轨表面接触疲劳裂纹的影响.结果表明RCF载荷作为控制铁轨表面接触裂纹的重要因素,其变化直接导致裂纹尖端应力强度系数的变化,从而改变裂纹的扩展状况.为减缓铁轨表面裂纹的扩展,可以针对载荷采取均匀分布载重量、使用润滑剂降低轮轨摩擦因数等相应措施.  相似文献   

4.
飞行机械臂系统的接触力控制   总被引:1,自引:0,他引:1  
针对飞行机械臂系统的接触力控制问题,本文首先从理论上证明了闭环无人机系统具有与弹簧-质量-阻尼系统一致的动态特性.基于飞行机械臂接触状态下力的分析,得到了无人机水平前向接触力与系统重力和俯仰角之间的动态关系,进而分析出接触力控制可以不使用力传感器来实现.根据阻抗控制思想,提出了飞行机械臂系统接触力控制方法,即通过同时控制位置偏差和对应姿态角度来实现接触力的控制.给出了单自由度飞行机械臂系统动力学模型,对应分析出系统的稳定性.开发了基于四旋翼飞行器的单自由度飞行机械臂系统,并进行了实际的飞行实验,验证了所提出接触力控制方法的有效性,同时也证实了所开发系统的可靠性.  相似文献   

5.
基于GL规范,采用有限元法对某兆瓦级风力发电机组轮毂进行极限强度分析.对轮毂S N曲线进行修正,分析疲劳计算需要考虑的载荷工况,使用GH Bladed软件仿真得到疲劳计算所需的载荷时间序列.使用ANSYS/nCode软件对轮毂进行疲劳寿命分析,结果表明轮毂的极限强度和疲劳强度均满足设计规范的要求.分析结果可以为兆瓦级风力发电机组轮毂的结构设计提供参考.  相似文献   

6.
为研究轮轨滚动接触疲劳(Rolling Contact Fatigue,RCF)载荷对铁轨表面裂纹应力强度因子的影响,以UIC60铁轨轮廓尺寸为依据建立轮轨接触的三维有限元模型,通过改变RCF载荷大小、轮轨表面摩擦因数和接触中心位置等轮轨接触的输入参数,计算铁轨表面接触裂纹尖端的应力强度因子,分析RCF载荷对铁轨表面接触疲劳裂纹的影响. 结果表明RCF载荷作为控制铁轨表面接触裂纹的重要因素,其变化直接导致裂纹尖端应力强度因子的变化,从而改变裂纹的扩展状况;为减缓铁轨表面裂纹的扩展,可以针对载荷采取均匀分布载重量、使用润滑剂降低轮轨摩擦因数等相应措施.  相似文献   

7.
刘存 《计算机仿真》2022,39(1):34-39
作为飞机结构的基本元素,加筋短板有较为宽广的非线性后屈曲区间.通常采用工程计算方法作为加筋板的设计依据,未充分利用结构的后屈曲强度.为研究加筋短板的后屈曲特性,求解加筋短板的后屈曲路径以及极限载荷,采用GMNIA(Geometrically and material nonlinear analysis with imperfections)仿真分析方法预测了加筋短板的极限载荷,得到了反映后屈曲路径的载荷—应变曲线,并与试验进行对比分析.研究结果表明,加筋短板初始屈曲发生在蒙皮的自由边,长桁是后屈曲的主要承载部位;有限元仿真的极限载荷与试验破坏载荷的相对误差为0.46%,有限元仿真的后屈曲平衡路径与试验吻合较好.因此,采用GMNIA仿真分析方法能够准确的分析加筋短板的后屈曲特性,达到减轻结构重量、提高结构效率的目的.  相似文献   

8.
高速旋转的磁悬浮转子跌落时会对保护轴承产生较大的冲击及振动,针对这一工况下保护轴承的应力变化及可承受能力,采用有限元仿真及三球法实验的方法分析了不同型号保护轴承滚动体的接触应力变化及承载极限,结果显示两种方法具有较高的一致性,接触应力与作用载荷呈1/3次方关系,且氮化硅材料的表面接触极限强度可达25580 MPa,极大地提高了保护轴承的可靠性。  相似文献   

9.
针对某型地铁车辆转向架在被吊起时起保护一系悬挂系统作用的轴箱吊耳在车辆运营中多次发生断裂的问题,用HyperWorks建立吊耳的有限元模型,以试验数据作为输入分析模态频率响应,通过仿真结果与试验结果的对比调整模型,保证模型仿真的准确性.综合分析仿真结果和试验结果,找出引起吊耳模态频率响应过大的原因,利用OptiStruct进行结构拓扑优化,根据优化结果提出4种新方案,并分别对比各方案的静强度、模态频率、模态频率响应和体积等,确定最佳设计方案.  相似文献   

10.
为探究火灾下超高性能混凝土(ultra high performance concrete,UHPC)梁斜截面承载性能的退化与损伤演化规律,采用Abaqus建立16个UHPC梁的热-力耦合分析模型,选择剪跨比、载荷水平、配箍率、箍筋配置方式、纵筋配筋率等作为考察参数,通过与试验结果对比验证模型的正确性.火灾下UHPC梁斜截面承载性能削减严重,其破坏延性优于普通混凝土梁.载荷水平和箍筋配置方式是影响UHPC梁耐火极限的主要因素:随着载荷水平增大,耐火极限降低;配置箍筋可以提高试验梁在火灾下的延性,但降低其耐火极限.  相似文献   

11.
为了研究航空发动机结构叶片丢失后整机响应与连接结构安全性,在瞬态显式动力学软件ANSYS/LS-DYNA中建立了真实大涵道比涡扇发动机的全三维有限元模型,并开展了一个转动周期的仿真计算。结果表明:丢失叶片与包容机匣及追随叶片的撞击过程中,撞击力分别在叶尖首次撞击机匣、叶片根部受追随叶片撞击、叶根撞击包容机匣时出现峰值;风扇机匣与承力结构的位移和应力最大值区域随着丢失叶片运动而变化,且始终发生在丢失叶片同一方向上。前轴承和中轴承所受载荷较大,后轴承载荷较小,且随着发动机转动近似正弦曲线。前安装吊耳处位移最大,其次为推力杆前端,后吊耳处位移较小。  相似文献   

12.
飞机平尾升降舵接头耳片承载能力分析与试验   总被引:2,自引:0,他引:2  
为给飞机平尾升降舵接头耳片极限承载能力试验提供参考依据,指导试验方案设计,采用非线性有限元法,将运动约束和节点力作为边界条件直接施加在产生接触的节点上,将加载棒作为刚体,将耳片作为变形体,运用MSC Patran和MSC Marc分析某飞机平尾升降舵铰链接头耳片在轴向0°,斜向45°和横向90° 3个方向的承载能力,并给出对应的极限承载能力和应力分布情况,用于指导试验加载方案和应变片布置. 通过接头耳片有限元计算得到的载荷-位移曲线与试验曲线大致吻合,预测出的试件破坏最大应力值和最易破坏部位与试验结果也相符合.  相似文献   

13.
M J?ger  A Luttmann 《Ergonomics》1989,32(1):93-112
A dynamic biomechanical human model is presented which allows the quantification of mechanical parameters such as torque, compressive and shear forces, and pressure at the lumbar intervertebral discs. The human model comprises a total of 19 body segments. Various trunk flexions can be analysed due to the provision of 5 joints at the level of the 5 lumbar intervertebral discs. The influence of intraabdominal pressure on spinal load is considered. The inclusion of the influences of gravity and inertia permits the analysis of both static body postures and dynamic body movements. Since the model is 3-dimensional, the lumbar stress can be calculated during both symmetrical tasks in the median sagittal plane as well as during non-symmetrical ones. The influences on spinal stress of trunk inclination and the position of an external load relative to the body are quantified for various load weights up to 50 kg. The torque at the lumbo-sacral joint L5-S1 lies, dependent on posture and load lever-arm, within the range between 0 and 500 Nm; the compressive force on L5-S1 lies within the range between 0.4 and 10 kN, and the shear force at L5-S1 between 0.2 and 0.9 kN. The influences of lift velocity and jerky movement on lumbar stress are quantified. Simulated humpback and hollow-back postures are studied. The compressive forces at the 5 lumbar intervertebral discs are compared. The validity of the model is examined by comparing the model calculations with the intradiscal pressure measurements taken from the literature. Strength tests on lumbar intervertebral discs and vertebrae are collated from the literature in order to assess the lumbar stress during load lifting. The lumbar ultimate compression strength varies within a wide range. The mean value for a total of 307 lumbar segments amounts to 4.4 kN, the standard deviation to 1.9 kN. In conclusion, lumbar compressive force values during lifting fall within the same range as the strength values for the human lumbar spine.  相似文献   

14.
针对机械臂末端安装串联弹性执行器(Series Elastic Actuator,SEA)与环境或工件接触作业工况,考虑SEA端部负载对接触面压力随机械臂运动姿态变化的问题,研究一种具有重力补偿的SEA接触力控制方法。首先分析了一种基于滚珠丝杆模组的SEA与Staubli TX90 组合的力控制实验装置结构,建立了SEA与工件接触过程的动力学模型,提出了一种具有输入重力补偿的PD型SEA弹簧力控制方法,该方法在没有接触力传感器的情况下,依据机械臂关节角对SEA端部负载进行重力输入补偿,通过检测弹簧压缩变形量,计算并反馈弹簧力实现对接触力的控制。最后通过SEA与正弦面工件接触力控制实验,并对力传感器采集的接触力信号进行频谱分析,验证了所提出控制方法的有效性。  相似文献   

15.
《Ergonomics》2012,55(9):928-939
Co-ordination of various components of the human body during the course of lifting are very complex and difficult to control. This study hypothesized that strategies used to control the motion patterns of the external load may be applied to control co-ordination and also to control the level of compressive force on the lumbosacral joint. A simulation of lifting based on the optimization approach was introduced to generate three classes of unique dynamic motion patterns of the external load directed by three different objective functions. The first objective function was to maximize the smoothness of the motion pattern of the external load. The second objective function was to minimize the sudden change of the centre of gravity of the body-load system. The third objective was to minimize the integration over time of the sum of the square of the ratio of the predicted joint moments to the corresponding joint strength during the course of lifting. Eight subjects were recruited to perform 40 lifts using each of the three optimal motion patterns of the load. Compressive forces on the lumbosacral joint were computed and compared. The data showed with statistical significance that subjects using the motion patterns of the external load suggested by the first objective function had the lowest compressive force peaks. Thus, this study satisfied two goals: (1) it indexed and synthesized three motion patterns of the external load by three biomechanically unique objective functions, and (2) it established the association between the spinal loading and the control of the motion patterns of the external load during lifting.  相似文献   

16.
为提高接触问题并行计算的效率,分析内力计算和接触计算过程的并行性,提出基于边权约束法构造接触多约束图的方法,对比和分析多约束图剖分算法和双重区域剖分算法的负载平衡和通信性能.数值实验表明,在典型二维模型中多约束图剖分算法的负载平衡性能略低于双重区域剖分算法,但仍可将负载不平衡度控制在较好的范围内,简化并行计算的通信过程,减少总通信量并降低动态通信量比例.  相似文献   

17.
Studies were made of two different techniques of bi-manual lifting with bent legs (A and B) and a technique of lifting with the back bent and the Knees almost extended (C). With technique A, the trunk was almost vertical, while with B it was erect and more forward inclined and the heel of the front foot kept in contact with the support. Two healthy subject samples (n = 18 and n = 16 respectively) were studied, both employing a force platform; with the second sample the back muscles were also evaluated by electromyography. The distance Delta L between the lines of gravity of the body and the load at the start of the lifts was shortest with technique A and longest with C. This was true whether the position of the feet was chosen spontaneously or was identical for all three techniques. The distance of the load from the body during the lifting movement was directly related to the distance at the start of the lift: the further away the load was at initiation of the lift, the further away it remained throughout the rest of the lift. A request to lift as close to the load as possible had a positive effect in shortening Delta L , but the amount of previously received instruction in lifting technique did not correlate with the spontaneously chosen Delta L.  相似文献   

18.
The ultimate load carrying capacity of cellular structures is predicted by means of a simplified procedure based on the Finite Element Method. The local stiffnesses are divided into the following linear regions: pre-critical, post-critical pre-collapse and post-collapse. The method is demonstrated on two double bottom structures.  相似文献   

19.
《Ergonomics》2012,55(7-8):783-805
Previous biomechanical analyses of typical load manipulation tasks were mainly limited to sagittal-plane activities or to static cases. This paper includes the biomechanical determination and assessment of lumbar load during asymmetrical bi-manual materials handling tasks which involve lateral turning of the body, trunk inclination, and sagittal flexion and lateral bending of the spine. Diagonal lifting tasks were analysed for different values for load weight (0-40 kg) and task duration (0·75-1·5 s). Whereas a constant grasp height of 15 cm was assumed, the height for releasing the load differed (50, 100, 150 cm). A dynamic spatial human model (‘The Dortmunder’) was used for calculating the torque in the sagittal, frontal, and transversal planes through the lumbosacral joint and for determining the compressive and the sagittal and lateral shear force at the L5-S1 disc. The trajectories of body segments and load are computer-simulated on the basis of postures adopted during the movement. During diagonal lifting of loads, lumbosacral torque in the sagittal plane is considerably larger than the lateral bending and torsional torque components. Dynamic analyses result in higher maximum values in the lumbar-load time curves than static analyses. The shorter the time for task execution, the higher the resultant dynamic effects and, in consequence, the higher the lumbar load. Lumbosacral compression and shear increase with increasing load-release heights due to higher acceleration and retardation of body and load when the same grasp position and task duration are assumed. The maximum load-bearing capacity of the lumbar spine was determined on the basis of strength data for isolated lumbar segments provided in the literature. The compressive strength falls within the same range as the compressive forces calculated for asymmetrical lifting of loads up to 40 kg. On account of the wide scattering of the compressive strength values, the main influences were determined (age and gender). At an age of 40 years, strength is approx. 6·7 kN for males and 4·7 kN for females (decrease with age per decade: 1·0 kN males, 0·6 kN females). In order to avoid overestimating an individual's lumbar compressive strength, predicted values should be reduced, e.g., by the standard deviation in the male or female samples (2·6 kN or 1·5 kN). Although only a few maximum shear force values are available in the literature, comparison with the calculated values for diagonal lifting leads to the conclusion that sagittal and lateral shear should not be ignored in the assessment of lumbar load during asymmetrical handling tasks.  相似文献   

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