Mechanics plays a key role in automotive design, development and utilization. The requirements of safety, energy efficiency, and environment protection for modern vehicles involve all disciplines of mechanics. This paper briefly introduces the history of vehicles development and its basic structure and performances. The state of the art of the vehicle mechanics is described with emphasis on the key problems in tire mechanics, vehicle directional stability, crashworthiness, and noise and vibration. The vehicles mechanics problems in the future are summarized.
Reducing the structural weight and enhancing the effective load of all kinds of aircrafts are the eternal subjects for designers all long. As regards that the air vehicles are usually in a special and complex service environment, one or more functions should be also given consideration except to the carrying capacity of the structures is designed. This article presents a comprehensive review on integrated design of lightweight multifunctional sandwich structures, which can realize loading and other multifunction, such as thermal control, heat protection, electron effect, stealth technique, energy absorption, actuating, energy storage, damping etc. This paper pools all those studies of lightweight multifunctional sandwich structures in the field of satellites, unmanned air vehicles and hypersonic space vehicles and so on. At last, the development tendency of lightweight lattice truss multifunctional structures is pointed out.
To aim to dynamic modification of one type frame of cross-country vehicle, combined the FRS and Test Modal technology, the dynamic response characteristic before and after the chassis was modified was compared and studied under the typical road exciting simulation in this paper. The analysis results indicated that FRS technology is a high efficient method for structure dynamic modification.
In order to improve the modeling efficiency for the computational dynamics of the open loop flexible robot, the generalized hybrid recursive dynamics base on the Spatial Operator Algebra (SOA) theory was presented. The generalized flexible robot was described in according to the type of the joint (active or passive). The generalized articulated inertia-matrix, the residual forces and the generalized acceleration and torque were computed through twice tip-to-base recursion and once base-to-tip recursion. At last the O(n) hybrid dynamics was gained. Then the real time solver for the differential-algebra equation was studied based on the linear multi-step method in this paper. Simulations results show that the dynamic modeling and fast integration techniques proposed in this paper are very useful.
We deducted the stiffness equation of the beam element with spring joint and the plane frame of spring element with property of semi-rigid joint by using force method and the method of gradual rigidization. The method has the characterics of clear physical concept, simplicity of deduction processes. The beam element with spring joint and the plane frame of spring element were employed to calculating and analyzing bearing capacity in engineering structures with semi-rigid joints.
ICM method is applied to slove topological optimization of plate and shell structure with stress constraints. An approximately explicit topological ICM optimization model of plate and shell structure with each design variable controlling multiple elements is established to minimize the weight with stress constraints. Stress constraints are transformed into structural distortional energy constraints in terms of the Misses strength theory which reduces the number of the stress constraints. The model is solved by SQP (sequential quadratic programming) algorithm using exact dual mapping. MSC/Patran & Nastran software is taken as a secondary development platform. The algorithm in this paper is implemented on by PCL language. Examples for the design variables equal to the number of cells were calculated, indicating that the method is effective and feasible.
In order to realize transmission underground information, using acoustic as the carrier and using the drill string as the transmission channel, it is necessary to understand the transmission characteristics of different types acoustic wave transmited in drill string. The drill string is simplified as ideal periodic tube structure. Finite-difference method is employed to simulate and analyse the unit impulse function acoustic signal propagation in periodic tube structure. Based on the obtained time domain and frequency domain distribution of the signals, the following conclusions are given. The output end will receive a relatively long time signal under the excitation of the unit impulse function acoustic signal, the signal will decay with the increase of time, and maximum amplitude is less than the input signal; drill string channel structure is the comb filter structure; pass band exists resonant peak, peak number is associated with the number of drill pipe and joints. The simulation results have good consistency with similar research results and verify that the feasibility and validity of the mathematical model and numerical method adopted.
Interior bracing support foundation pit possesses the characteristics of economy, rapid and high efficiency. Mechanical characteristics, structural analysis and program selection of deep foundation support were introduced with the practice of foundation supporting project of the stormwater pipeline project in Zhengzhou City, which provides some references for design and construction of the interior bracing support pit.
Remote projectile landing time and location on the earth's surface were calculated using two ap-proaches, becase of the calculation defects in the rectangular Cartesian coordinate system connected to the earth's surface. First, we established a rectangular Cartesian coordinate system on the earth's surface, and then calculated the analytical solution for arbitrary projection angles considering the air resistance and the earth rotation. The conversion relation between the rectangular Cartesian coordinate system and the geocen-tric coordinate system was obtained. The landing time and location of the remote projectile were calculated under the condition that the distance between the projectile and the earth's core is equal to the earth radius R. Second, the position, velocity and acceleration of the projectile was described in the spherical coordinates system, the landing information of the projectile was obtained by numerical calculation. The calculation results from the two methods are very close, indicating that both the two methods are feasible for obtaining information of the projectile.
During analyzing the drillstring dynamics in 3D borehole, initial bending of drillstring must to be dealed with. And the effects of position and deviation on contact force between the drillstring and borehole should be considered. Based on mechanical model of turning drillstring in 3D borehole, the affine coordinate system was introduced to analyze the deformation, contact force and friction torque. A new method was offered for study of drillstring dynamics.
In order to analyse the sensitivity of the influential factors of the uniaxial compressive strength of the artificially frozen soil, this paper selected seven influential factors of the uniaxial compressive strength of the artificially frozen soil, according to the method of orthogonal experiment design, a number of uniaxial compression tests are conducted, the test results are analysed by using the grey relational theory, the magnitude of the sensitivity of all selected influencing factors and the order of arrangement of them are given. The results show that: In the selected seven influential factors, the temperature is the most sensitive influencing factor, and then is the depth, the next is soil property, followed by loading rate, maintenance time and density, and the selected seven influencing factors are all important factors, provided the basis for related laboratory test and engineering application.