极值型风荷载作用下大型结构可靠性分析

研究了在极值型风荷载作用下大型结构的可靠性。结构的破坏以结构刚度矩阵奇异为依据，首先列举结构的主要破坏模式，其次利用增量载荷法求出的结构的安全余量方程，然后将极值型风荷载正态化，计算出各主要破坏模式的破坏概率，并用二阶窄界限理论计算大型结构的可靠性。最后以一大型输电塔为例进行了可靠性计算     

法向载荷和滑动速度对GCr15钢干滑动摩擦的影响

本文研究了在干滑动摩擦情况下,GCr15钢与YG8硬质合金对磨时的摩擦系数与法向载荷及滑动速度的关系。结果表明,摩擦系数是随着法向载荷和滑动速度的增加而降低。根据磨损表面发生的变化和磨损表面温度计算,作者认为法向载荷和滑动速度的增加使闪温增高,从而导致了摩擦磨损表面的局部熔化,即形成了边界润滑,故此摩擦系数降低,而且在较高的载荷和滑动速度条件下,不同显微组织材料的摩擦系数之差减小。     

连续体结构拓扑优化应力约束凝聚化的ICM方法

为克服应力约束下拓扑优化问题约束数目多、应力敏度计算量大的困难，提出 了应力约束化凝聚化的ICM方法. 在利用Mises强度理论将应力约束转换成应变能约束后， 提出了应力约束凝聚化的两条途径：其一为应力全局化的方法，其二为应力约束集成化的方 法. 由此建立了多工况下以重量为目标、以凝聚化应变能为约束的连续体结构优化模型，并 利用对偶理论对优化模型进行了求解. 4个数值算例表明：该方法具有较高的计算效率，得 到的拓扑结构比较合理，不仅适用于二维连续体结构，也适用于三维连续体结构.     

NONLINEAR VIBRATION OF CIRCULAR SANDWICH PLATES UNDER CIRCUMJACENT LOAD

Based on von Karman plate theory, the issue about nonlinear vibration for circular sandwich plates under circumjacent load with the loosely clamped boundary condition was researched. Nonlinear differential eigenvalue equations and boundary conditions of the problem were formulated by variational method and then their exact static solution can be got. The solution was derived by modified iteration method, so the analytic relations between amplitude and nonlinear oscillating frequency for circular sandwich plates were obtained. When circumjacent load makes the lowest natural frequency zero, critical load is obtained.     

Iodine-catalyzed aerobic oxidation of o-alkylazoarenes to 2H-indazoles

An iodine-catalyzed aerobic-oxidative C-H functionalization of o-alkylazoarenes to afford 2H-indazoles has been developed. CuI was found to be an effective additive to accelerate the regeneration of iodine in the catalytic cycle. This catalytic system is suitable for both electron-rich and electron-deficient azoarenes and tolerates a variety of functional groups with high yields. A gram-scale reaction was successfully conducted, proving the scalability of this reaction.     

Motion of a system of seismic sources over ice on a body of water under the action of a pulse

The vertical motion of a system of two identical seismic sources and a spring truck tractor on ice under the action of a shock pulse from the seismic sources is studied to estimate the strength of ice. It is shown that during the pulse time, the interaction of the masses of the seismic sources and the tractor is small and the compressibility effect of the liquid can be ignored. Calculations show that for the seismic sources, the dynamic load far exceeds the static load and for the tractor, the static load is maximal. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 2, pp. 147–155, March–April, 2007.     

高耸异型烟囱结构风压和风振系数试验研究

本文在模拟的大气边界层中,对某一发电厂高耸异型烟囱的刚性模型进行了测压试验研究,得到了这一结构的平均风压系数、最大和最小风压系数分布,以及该结构的风荷载体型系数;结果表明在烟囱外形明显变化的局部区域,风压绝对值较大,与理论分析一致。同时,对动态测力试验模型进行了高频动态天平测力试验研究,详细介绍了试验及数据处理方法,根据试验结果计算得到了该烟囱在风作用下的动力响应和风振系数;根据试验结果计算所得的风振系数值大于按规范公式估算值。这些结果不仅为结构的风荷载计算提供了依据,也有助于进一步认识该类异性烟囱结构的风荷载和风振特性。     

Steering forces on undriven tractor wheel

The steering forces on an undriven, angled wheel mounting a 6-16 8PR tire were measured on a wheel test carriage at zero camber angle and at 1.5 km/h forward speed in a soil bin with sandy clay loam soil. The lateral force developed was found to be a function of slip angle, normal load, and inflation pressure for a particular soil condition. An exponential relationship could estimate the coefficient of lateral force of the 6-16 tire. The coefficients of this equation were found to be linearly related to inflation pressure. Rolling resistance of the wheel tested was found to be a function of slip angle, normal load, and inflation pressure for the soil condition tested. A linear relationship existed between the rolling resistance and slip angle, where the coefficients were found to be a function of inflation pressure and normal load. The generalized equations developed in the present study for estimating coefficients of lateral force and rolling resistance by taking both the tire and operating parameters into account, were found to be reasonably good by looking at the high coefficient of determination between experimental and estimated values.     

DYNAMIC STABILITY OF AXIALLY MOVING VISCOELASTIC BEAMS WITH PULSATING SPEED

IntroductionThe class of systems with axially moving materials involves power transmission chains,band saw blades and paper sheets during processing. Vibration of such systems is generallyundesirable. The traveling tensioned Euler-Bernoulli beam is the pr…     

高速荷载下多孔饱和地基的动力响应

研究高速荷载作用下梁与多孔饱和半空间的动力响应。由Fourier变换求解多孔饱和固体的动力基本方程，根据梁与半空间的接触条件得出多孔饱和半空间上梁的垂直位移的表达式。文中的数值算例考虑了荷载移动速度对梁的动力位移的影响，并与相应的弹性半空间问题作了对比。从算例中可以发现荷载移动速度对动力位移有很大的影响，当移动速度与半空间的表面波速相近时，地面会当产生很大的振动，同时还发现当速度大于介质的剪切波速时，多孔饱和半空间上梁的动力响应与弹性半空间上梁的动力响应有很大的差别。