不同尖锐度纹理形状的摩擦触觉感知与表征研究

通过开展触觉感知不同尖锐度纹理形状的接触摩擦特性、主观认知行为和功能核磁共振试验,从皮肤的“感”、大脑的“知”和主观的“评”全面系统地对不同纹理形状的摩擦触觉感知进行了量化表征研究. 研究表明:接触摩擦力、主观评价、激活脑区面积和强度是表征摩擦触觉感知的有效参数. 触摸不同纹理表面的摩擦力中黏着摩擦力比形变摩擦力占比大,触摸平角纹理的摩擦力最大,尖角纹理的摩擦力最小. 黏着感主要受接触面积和黏着摩擦力的影响;尖锐感主要受触觉感受体所受应力和形变摩擦的影响;而舒适感受到表面摩擦机制和触觉感受体所受应力综合影响. 触觉感知纹理形状激发的大脑功能区以躯体感觉皮层为主,激活脑区主要位于中央前回和后回. 触摸过程的舒适感与激活脑区大小和强度成反比,舒适感差的纹理激发的脑区范围和强度大,且存在负激活现象.      

不同法向力和纹理间距下的手指皮肤感知能力研究

手指与物体表面接触摩擦过程中会产生压缩、拉伸等机械变形,这一过程中包含丰富的触觉信息,对人体感知外界环境具有重要意义.针对当前研究中难以将摩擦信号与人体主观感受相结合的问题,采用UMT-II多功能摩擦磨损试验机对受试者食指部位施加不同的恒定法向载荷来模拟触摸力,通过改变触摸样品的纹理间距、接触介质及直径,对木棒数目做出判断.结果表明:指尖滑过试验样品时所受周期性压力变化曲线可以反映受试者的摩擦感知状况;随着法向力及样品纹理间距的增大,受试者判断的准确性逐步提高,摩擦感知能力增强;指尖与样品之间的润滑介质减小了手指皮肤与样品间的摩擦力,从而降低了受试者感知判断的准确性;直径较大的一组样品引起指尖皮肤的变形较大,受试者摩擦感知灵敏性增强.     

粗糙表面的摩擦触觉感知研究

本文中研究了手指触摸粗糙表面的摩擦振动特性、脑电生理反应和主观评价,为产品触感舒适性和抓握可靠性设计以及产品触感量化表征提供理论依据. 研究结果显示:随着表面轮廓算术平均偏差和轮廓单元平均宽度的降低,摩擦系数和功率谱重心逐渐增大,垂直偏差逐渐降低;垂直偏差、功率谱重心和摩擦系数特征参数能够反应粗糙表面的形貌特征变化,并且与人的主观感知评价一致,可以用来定量表征人对材料表面粗糙度、细致度和黏着度的感知. ERP曲线的P200成分峰值与接触表面的粗糙特征相关,粗糙度大的表面诱发的P200峰值高;P300成分与人的主观认知判断有关,粗糙感强、细致感差及黏着感低的表面诱发的P300峰值高且潜伏期短. 研究表明,材料表面的粗糙特性通过影响皮肤的接触摩擦行为,进而影响人脑的触觉感知和主观评价. 表面摩擦振动特性、人脑电生理反应和触感主观评价具有相关性,三者结合是系统研究粗糙表面摩擦触觉感知的有效手段.      

曲面物理和力学

回顾了平坦空间中的经典物理和力学, 综述了卷曲空间中物理和力学的三个典型案例, 即生物膜力学、扁壳力学和曲面扩散动力学, 揭示了平坦空间与卷曲空间物理和力学的根本差异. 论文阐明了, 平坦空间的物理和力学只有一个基本微分算子------经典梯度, 而曲面物理和力学必然存在两个基本微分算子------经典梯度和形状梯度.     

织物力学研究的新进展

简要地回顾了织物力学的发展历史,重点介绍近10几年来,在服装CAD核心------"试衣系统"的技术需求的刺激下,在织物悬垂、屈曲方面研究的进展.特别是关于织物屈曲研究的开展,涉及到了织物本构理论这个织物力学中最基础的问题,织物细观本构理论的建立和对织物一系列屈曲现象的成功的解析分析是织物力学研究的最新进展,构成了近代织物力学的主要内容.最后,对今后织物力学研究的方向进行了展望.      

纤维增强树脂基复合材料的疲劳剩余刚度研究进展

回顾了过去二十年来公开发表的复合材料刚度退化的主要模型,对这些模型做了分类和讨论.按照模型的理论基础及研究方法将它们分为了理论模型、半经验模型和经验模型三类.理论模型是指那些完全依赖于力学分析而得到的模型,这类模型建立了材料的微观损伤机理与宏观刚度退化之间的关系.经验模型通常不需要过多的力学分析,仅对大量实验数据进行经验性拟合,一般具有简单易用的形式.半经验模型是理论与经验模型的结合------在力学分析基础上的经验处理.      

高气液比垂直管流连续携液实验

在可视化管流实验架上, 采用压缩空气和雾化液体作为实验介质, 模拟连续携液过程并测试 实验参数; 采用高速摄像仪捕捉到气流中液滴实际形状------椭球体. 实验发现: 圆球体模型、 椭球体模型计算结果与实验值分别偏差10{\%}, 58.3{\%}. 分析椭球体受力状态并结合实验数据导出了新的椭球体数学模型, 按照新模型计算的结 果与7口产水气井生产情况一致.     

基于θ1方法的多体动力学数值算法研究

将结构动力学领域的\theta_1方法拓展到数值求解多体系统运动方程------微分--代数方 程(DAEs), 分别求解指标-3 DAEs形式的运动方程和指标-2超定DAEs (ODAEs)形式的运动方程. 通过数值算例验证了方法的有效性, 并得到\theta _1 方法中参数\theta _1的选取与数值耗散量之间的关系. 数值算例还说明对于同 一个多体系统, 采用指标-3的DAEs 描述时存在速度违约, 用指标-2的ODAEs描述时, 从计算机精度上讲, 位置和速度约束方程 同时满足, 并且\theta_1方法在求解非保守系统DAEs和ODAEs形式的运动方程时 都具有2阶精度. 最后\theta_1 方法与其他直接积分法求解DAEs和ODAEs形式运 动方程的CPU时间进行了比较.     

骨生物力学中某些基本概念的历史

<正> 1.引言 一般认为,生物力学可以理解为力学规律对生物系统的应用,因此,我们目前关于骨生物力学的知识自然也在很大程度上依赖于力学的各个领域。但力学规律是通过模型与抽象而导出与表达的,而大多数模型与抽象并不那么容易转换到生物体情形。例如,刚体的力学概念,连同刚体的性质(体积,形状,惯性,惯性矩)很容易用来定量描述有生命或无生命物体      

人体肌骨的多柔体系统动力学研究进展

人体肌肉骨骼系统简称肌骨系统, 包括骨骼、骨骼肌与关节连接, 其力学模型是典型的多柔体系统. 从多体动力学角度研究肌骨系统, 主要关注其在运动过程中的肌肉内力、关节力矩及产生的动力学影响, 属于动力学与生物力学的交叉融合. 肌骨系统的多体动力学模型已被广泛地应用于临床医学、竞技体育、军事训练、人机工程等诸多领域, 其仿真结果可为提高人体运动能力、降低关节载荷与能耗、避免运动损伤、加快康复进程等提供重要计算参考数据. 与此同时, 上述研究亦对肌骨动力学研究提出了许多新挑战. 本文综述了人体肌骨多柔体系统动力学相关研究进展, 包括骨骼肌功能解剖与生物力学建模、神经与肌肉控制理论、肌骨系统动力学问题与求解方法, 以及近年来肌骨多体动力学在步态分析、飞行员抗荷动作、口颌手术规划等领域的典型应用. 与工程领域的机械多体系统相比, 人体肌骨多体系统具有肌肉内力主动性与肌肉控制冗余性两大特征. 现有骨骼肌模型难以同时考虑肌肉的解剖结构、三维几何与肌力产生的生物化学机制. 已有大多数肌骨模型采用静态优化假设消除肌肉冗余性, 忽略了肌肉与肌腱内力平衡及兴奋收缩耦联机制. 此外, 目前仍缺乏实现肌骨模型个性化的无创在体测试手段. 未来, 人体肌骨多体动力学研究将会向更精确、智能、个性化的方向发展, 成为动力学与生物力学交叉的热点研究领域.      

Effects of particle softness on the rheology and yielding of colloidal glasses

We studied the linear and nonlinear rheology of colloidal glasses consisting of hard spheres and soft core-shell particles at several volume fractions to explore the effects of particle softness on the mechanical properties and yielding. Creep and recovery and oscillatory shear measurements were used to determine the shear elastic modulus and the yield strain. Both hard and soft sphere glasses exhibited ‘entropic cage elasticity’ below random close packing, whereas for compressed soft spheres at higher effective volume fractions, the yield strain was determined by shell elasticity. The shear modulus followed a strong increase with volume fraction for hard spheres and a much weaker one for soft particles reflecting their interparticle potential. Nonlinear effects, revealed as strong distortions of the stress signal during yielding, were analyzed via Fourier transform rheology and Lissajous plots. The significant contribution of the nonlinearities was analyzed in terms of strain softening and hardening mechanisms within a cycle of oscillation and discussed in relation to particle softness.     

确定在体皮肤能量耗散数的方法

本文描述了激励、检测在体皮肤谐振频率的方法。根据幅频曲线计算出皮肤的能量耗散数。获得了不同年龄的皮肤耗散数。对皮肤受乳膏和酒精处理后,利用该法对能量耗散数的影响也进行了评价。     

ф900带软硬环的土平面波加载器研制

介绍了用于抗爆试验研究的900带软硬环的土平面波加载器的研制过程、静力与动力验证试验。由于采用了软硬环试验箱体以保证箱体的轴向柔性及径向刚性技术，验证性试验比较好地模拟了介质的一维平面应变运动。验证性试验结果表明该试验装置得到了预期的设计要求。     

含损伤材料的热粘塑性本构关系和柱壳破裂研究

以含内变量的本构关系理论为基础 ,结合材料损伤演化方程 ,并考虑了温度和损伤对材料参数的影响 ,得到了增量形式的热粘塑性本构关系的普适显式表达式。然后使用Bodner幂函数型粘塑性模型 ,具体推导了其增量形式的热粘塑性本构方程。接着结合在实践中有重要意义的内部爆炸载荷作用下的柱壳破裂问题 ,建立了含损伤热粘塑性柱壳破裂问题的完备方程组 ,使用有限差分方法 ,完成了对问题的数值模拟 ,并对结果进行了分析。计算结果与实验结果符合良好。     

Mesh update and projection techniques for 3D aerodynamic simulations

The target is to develop computational techniques for studying aerodynamic interactions between multiple objects with emphasis on studying the fluid mechanics and dynamics of an object exiting and separating from an aircraft. In these cases, the computational challenge is to predict the dynamic behaviour and path of the object, so that the separation process is safe and effective. This is a very complex problem because it has an unsteady, three-dimensional nature and requires the solution of complex equations that govern the fluid dynamics of the object and the aircraft together, with their relative positions changing in time. The gravitational and aerodynamic forces acting on the object determine its dynamics and path. The computational tools developed are based on the simultaneous solution of the time-dependent Navier–Stokes equations governing the airflow around the aircraft and the separating object, as well as the equations governing the motion of that object. These computational methods must include suitable mesh update techniques. In the research presented, focus is given to development of mesh update methods to increase the numerical accuracy and efficiency of the computations. These methods range from update tactics, reducing distortion and methods reducing the error introduced through projection.     

强激光水下爆炸推进的物理机制

对激光水下聚焦爆炸推进的作用机理开展了实验测量和数值模拟研究. 实验观察到激光水下聚焦爆炸推进分为两个物理过程: (1) 强激光与铝膜相互作用诱导等离子体演化, 产生短脉冲、高幅值的等离子体压力, 并对航行体做功; (2) 激光爆炸产物气泡脉动, 对航行体继续提供推力. 另外, 实验还对不同介质中的激光推进效率以及气泡与约束壁面/自由水面相互作用的物理机制进行了研究. 发现在高阻抗环境介质、气泡受约束脉动以及近自由水面条件下, 激光爆炸推进的效率更高. 在实验的基础上, 建立了激光水下聚焦爆炸推进的物理模型, 发展了相应的耦合数值计算方法. 计算得到的气泡脉动规律及航行体运动规律与实验测量结果一致, 验证了计算的模型和方法, 为强激光水下聚焦爆炸推进机理的研究提供了一种有效的方法.      

Plastic failure analysis of an auxetic foam or inverted strut lattice under longitudinal and shear loads

Auxetic materials possess negative Poisson's ratios. As such, they can be applied in situations where traditional materials perform poorly or cannot perform. We investigate the plastic failure of a 3D auxetic strut lattice under uniaxial and transverse loads in order to complement ongoing research in miniaturized strut-based sandwich cores. The chosen lattice is also representative of an auxetic foam. Plastic failure models derived with respect to two physical parameters (packing parameter and relative density) which control the negative Poisson's ratio compare well with numerical data. Microscopic failure modes differ depending on the loading state: shear failure is due to global plastic yielding while plastic localization occurs under uniaxial loads. This observation suggests among others that it is advisable to use auxetic cores when structural softness under normal loads and hardness under transverse loads are both critical design conditions.     

Persistence and coexistence of infinite attractors in a fractal Josephson junction resonator with unharmonic current phase relation considering feedback flux effect

Josephson junction resonators are the devices which exhibit complex behaviours as a consequence of their inductive properties. Even though the insulating medium between Josephson junctions (JJs) is normally considered homogeneous, the fact that lithography is used to form the layer, it has fractal substrates. Such JJs are identified as fractal Josephson junctions (FJJs). In this paper, a new chaotic oscillator based on memristor and FJJ has been investigated. Superconductor properties can dramatically change its operating points especially voltage and heat that are related to Josephson tunnelling. Some changes in the operating points can cause the Josephson tunnelling junctions to oscillate in different oscillation modes in very high frequencies. This can be achieved by considering the potential across the junction with its flux feedback. In order to model the magnetic flux effect, we use a memristor whose memductance function is considered as an exponential function. By varying the type of the bias current, we could observe the property of infinitely coexisting attractors in the memristor-fractal Josephson junction oscillator, which is considered as a rare phenomenon in physical circuits. The proposed Josephson-Memristor circuit model is developed, and its equilibrium points, bifurcation and Lyapunov exponents are computed. As an engineering application, modelling the trajectories of the moving object has been realized. First, the SURF algorithm, which is not affected by the scale and rotations of the object, is used in the images to identify an object that tracks the states of the proposed Josephson-Memristor circuit. In this way, the coordinates of the orbits on which the object moves were determined on the image. In order to reproduce the orbits of the specified object, the coordinate information of the object has been trained to the artificial neural network model and the orbits of the object have been reproduced.

     

多机械臂搬运同一物体的协调动态载荷分配

针对多机械臂共同搬运同一物体形成闭运动链的协调系统,研究了多机械臂协调动态载荷分配存在冗余情况下的实时性分配方法文中提出了“应集中惯性质量棒”的概念,进而根据各机械臂的承载能力,采用线性加权的方法发展了一种操作物体质心处零内力的载荷分配原则。最后给出了系统载荷分配的解析表达式,有效地解决了多机械臂搬运同一物体时其动态载荷分配的实时性问题。     

Fracture analysis of a functionally graded strip with arbitrary distributed material properties

In this paper, the plane elasticity problem for a crack in a functionally graded strip with material properties varying arbitrarily is studied. The governing equation in terms of Airy stress function is formulated and exact solutions are obtained for several special variations of material properties in Fourier transformation domain. A multi-layered model is employed to model arbitrary variations of material properties based on two linear-distributed material softness parameters. The mixed boundary problem is reduced to a system of singular integral equations that are solved numerically. Comparisons with other two existing multi-layered models have been made. Some numerical examples are given to demonstrate the accuracy, efficiency and versatility of the model. Numerical results show that fracture toughness of materials can be greatly improved by graded variation of elastic modulus and the influence of the specific form of elastic modulus on the fracture behavior of FGM is limited.