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1.
We analyze the problem of an elastic sphere impacting against another elastic body for the case when adhesive forces act between
the bodies. Depending on the parameter describing the (relative) influence of the adhesive forces, the bodies will either
separate or continue to be in contact and perform an oscillatory motion after the rebound. The value of the adhesive forces
parameter defining separation and capture is calculated.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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利用现场足迹特征,分析罪犯的性别、年龄、身高、体态、行走姿势等个人形体特点,常称为给罪犯“画像”。这一技术在侦破案件中起了一定作用。(1)研究人在常态下行走时留在地面上的平面足迹反映出压力的分布和变化规律,分析压力与年龄的相关性,从中研究出分析年龄的科学方法,提高分析年龄的准确率。(2)研究平面足迹压力与人的性别、身高、体态、行走姿势的相关性找出各自的科学分析方法。(3)从分析理论上全面加以提高, 相似文献
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盘-销摩擦系统摩擦接触力测试与特性分析 总被引:1,自引:1,他引:0
测量分析动态摩擦接触力是研究摩擦振动与噪声发生机理的关键.本文中建立了盘-销系统摩擦尖叫试验台架,成功再现了摩擦尖叫.采用三向力传感器对有无摩擦尖叫条件下的动态摩擦接触力进行了测量,并利用小波信号分解、概率密度函数、功率谱密度函数、时频分析等方法进行了分析和讨论.研究发现:在发生摩擦尖叫时,动态摩擦力和法向力发生高频波动,是系统噪声的激励源;无摩擦尖叫时的摩擦力和法向力的动态分量为典型的白噪声随机过程,呈非高斯分布;有摩擦尖叫时的摩擦力和法向力为窄带高频类谐波信号,摩擦力呈非高斯分布,而法向力近似为高斯分布;模态耦合是导致盘-销系统发生动态接触力高频波动以及摩擦尖叫的原因. 相似文献
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混凝土动态冲击问题的一种欧拉数值方法 总被引:10,自引:0,他引:10
针对混凝土的动态冲击问题给出了混凝土的Holmquist Johnson Cook本构关系 ,本构关系中的等效强度作为压力、应变率和损伤的函数 ;压力表示为体积应变的函数 ,并考虑了永久破碎的效应 ;积累损伤作为等效塑性应变、塑性体积应变和压力的函数。结合三维弹塑性流体力学欧拉数值方法 ,提出了混凝土的Holmquist Johnson Cook本构关系与欧拉程序相结合的计算方法。介绍了带混凝土Holmquist Johnson Cook本构关系的三维弹塑性流体力学欧拉程序。 相似文献
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冲击载荷下混凝土材料的动态本构关系 总被引:64,自引:5,他引:59
利用改装的杆径为 74mm的直锥变截面式大尺寸Hopkinson压杆对混凝土材料进行冲击压缩实验 ,系统研究了混凝土的应变率硬化效应 ,采用一种新的方法损伤冻结法对混凝土材料在冲击载荷下的损伤软化效应进行了系统研究 ,给出了冲击载荷下混凝土的损伤演化方程 ;在对数据进行合理分析的基础上 ,结合粘弹性本构理论 ,得到混凝土材料的损伤型线性粘弹性本构关系。 相似文献
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骨料对混凝土材料冲击压缩行为的影响 总被引:14,自引:1,他引:14
利用大尺寸Hopkinson压杆,以实验数据为依据,研究了四种不同骨料尺寸的普通混凝土材料和两种不同配比的钢纤维增强混凝土材料在冲击载荷下的压缩强度,从唯象的角度分析了骨料性质及其粒径对混凝土材料动态压缩性能的影响及可能的力学机理,为在工程上更好地利用混凝土材料提供一定的理论和实验的支持。 相似文献
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The motion of a system of bodies along a plane in a viscous fluid in the presence of flow shear is considered. It is demonstrated
that a main torque, linearly proportional to the velocities of the bodies, is exerted by the fluid on the system of the bodies
and the plane.
Moscow. Translated from Izvestiya Rossiiskoi Akademii Nauk, Mekhanika Zhidkosti i Gaza, No. 1, pp. 89–96, January–February,
1997. 相似文献
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In this paper a basic, easily to multi-contact problems extendable, non-smooth approach is applied to analyze a bar striking an inelastic half-space. Coulomb contact is assumed and modeled by using set-valued Newtonian impact laws in normal as well as in tangential direction. The resulting linear complementarity problem contains all possible impact states and provides an instantaneous collision operator that respects all inequality constraints. This operator depends on the orientation of the bar and determines uniquely the post-impact velocities as functions of the pre-impact state. Different types of solutions may occur, including “stick’’ and “slip’’. In this context, stick and slip have to be understood as the two cases characterized by the tangential impulsive force as an element of either the set-valued or of the single-valued domain of the friction law. Depending on the choice of parameters, sign reversal of the tangential contact velocity is possible. For certain inertia properties and initial conditions, the collision operator yields an impact, even for initially vanishing normal contact velocity. This phenomenon is well known as the Painlevé paradox. The results obtained by this fully non-smooth rigid body approach are compared with those of other impact models, such as a lumped mass model with compliance elements, and a collision operator used for particle interactions in flows.AMR: 160A, 160B, 160Y, 292B, 292Y 相似文献
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Yu. P. Lebedev L. N. Maurin E. D. Potapov 《Journal of Applied Mechanics and Technical Physics》1975,16(1):99-103
Exact expressions are found for the drag (modified Stokes force) and the lift (modified Magnus force) on a porous sphere spinning slowly in a viscous fluid flowing slowly and uniformly past it. 相似文献
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为研究行车车速、桥面的不平度和桥面损伤对车-桥面铺装耦合振动系统动力效应的影响规律,将汽车等效为两自由度五参数模型,将正交异性桥面铺装等效为梁-板结构.在车辆与桥面铺装接触点采用接触力和位移协调的条件,建立车辆和桥面铺装动力耦合系统模型和振动方程组.利用模态分析法以及时变力学系统的求解方法-状态空间法,借助大型有限元软件ANSYS和MATLAB编程技术,求解车-钢桥面铺装耦合振动系统的动力响应.分析由桥面铺装的不平度、车速以及桥面损伤等引起的行驶车辆的随机动荷载对桥面铺装冲击系数的影响,并考虑桥面的不平整将车辆荷载简化成沿铺装层表面的随机动荷载和车辆荷载简化成沿铺装层表面纵向移动的恒载两种加载方式的分析结果进行比较.研究结果表明,在进行铺装层结构设计计算以及复合梁疲劳试验时,可考虑冲击系数为1.5. 相似文献
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I. V. Schweigert V. A. Schweigert 《Journal of Applied Mechanics and Technical Physics》1998,39(6):825-831
An equilibrium two-layer structure of charged microparticles in the near-electrode layer of a radio-frequency discharge was
simulated numerically using the Monte Carlo method. Depending on gas pressure, the microparticles either move chaotically
or form a multilayer structure with a hexagonal lattice in a horizontal plane. Based on the experiment, a mechanism is proposed
that describes the unusual structure of a plasma crystal in which particles of the lower layer are located in the vertical
direction strictly under the particles of the upper layer and form vertical columns.
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 39, No. 6, pp. 8–15, November–December, 1998. 相似文献
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断裂能是定量表征混凝土断裂韧性的重要指标,但其实验结果显著依赖于混凝土试件断面面积评价方法的有效性和准确性。因测定困难,通常情况下只能由截面面积代替,造成断裂能计算结果存在较大误差。本文以碳纤维混凝土为研究对象,采用数字处理技术对混凝土断面形貌进行量化分析、重构,结合分形计算方法得到混凝土的真实断面面积,并将其用于碳纤维混凝土的断裂能计算,分析讨论了纤维掺量和长度对混凝土断裂能的影响规律。实验结果表明:碳纤维的引入显著提高了混凝土断面的粗糙度,表现为断裂面分形维度的明显提高,实际断面面积随之增大,以此为依据计算出的混凝土断裂能及其增益比随碳纤维掺量和长度的变化规律与韧度系数测试数据(按ASTM C1018)的一致性良好。 相似文献
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Using the basic equations of hydromechanics and also the Lagrange equations of the second kind, expressions are derived for the force acting between a liquid and a vapor bubble growing within it. Cases studied include those of the growth of a bubble on a thin filament or plane surface in an ideal liquid and a liquid of low viscosity. The sign of the hydrodynamic forces depends on the particular law of growth of the vapor bubble.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 165–170, May–June, 1973. 相似文献
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混凝土断裂过程及尺寸效应分析 总被引:1,自引:0,他引:1
为研究混凝土裂纹断裂过程和最大承载力计算方法,通过实验机对四种不同尺寸混凝土紧凑拉伸断裂试件进行了加载过程实验,并对其中一个试件进行应变片跟踪测试.由实验结果分析得到了一系列关系曲线,如试件的载荷-加载点位移关系曲线,断裂损伤区变形随载荷变化曲线;并且计算了不同尺寸断裂试件的应力强度因子.结合计算粘聚裂纹应力强度因子的公式与断裂准则,完成了对承载力理论值的计算,并将其与实验峰值平均值进行对比,其结果是两者相比误差较小,表明此种计算裂纹结构最大承载力方法是可行的. 相似文献