Applied Mechanics and Materials Vols. 668-669

Abstract: Aerodynamics of flow past two tandem bluff bodies is a critical problem in fluid mechanics. In this work, the flow over two circular cylinders with unequal diameters in tandem arrangement is numerical investigated using lattice Boltzmann method. The diameter of the bigger one is adopted as the characteristic length, the diameter ratio is fixed as 2, and the Reynolds number is 100. Spacing between two cylinders (scaled by the characteristic length) are varied from 0 to 3 characteristic diameter, and the effects of which on the flow patterns of such a system are studied. The results show that flow patterns behind two tandem unequal circular cylinders are significantly different from that behind a single one. Due to the downstream cylinder, two classic vortex interaction modes are observed, known as destruction interaction mode and construction mode.

Abstract: Sub-frame of dump truck is a special equipment, which is used to avoid carriage of goods having stress concentration on the chassis frame, and its design rationality have very important influence on the using performance of whole vehicle. In this paper, according to the phenomenon that the sub-frame of a company's mining heavy-duty dump trucks often appear crack and even rupture, using finite element analysis method, the sub-frame has been carried on the static analysis in both cases that the normal load and eccentricity loading when unloading goods. The analysis result shows that the reason of crack and even rupture of secondary frame is stress concentration occurs in the shaft hole connecting balanced frame with sub-frame because of lateral centroid of goods deviating from the longitudinal symmetry plane caused by goods loading or overloading and maximum stress is beyond the material yield limit. The improvement suggestions of sub-frame design are put forward finally.

Abstract: In the field of mechanical installation and repairing, drawing devices are often used to disassemble or push up components of various types of axie and set. Nowadays it is widely used in areas such as mechanical installation, machinery manufacturing, machinery repair, but still have problems to be used well with an appropriate force. The article presents a new kind of drawing device named force multiplication drawing device. It is designed by using the lever principle and can acquire much stronger drawing force. After theoretical calculations, it is proved to be very valuable.

Abstract: Nonlinear dynamic behaviors of the fractional calculus model viscoelastic arch are discussed in this paper. The motion equations governing dynamic behaviors of the viscoelastic arch is derived and simplified by Galerkin method. The numerical method for solving the motion equations with fractional calculus is presented here. The influences of the load parameter and the material parameter are considered respectively. The results show that the chaotic vibration of the arch appears in forced vibration. And both the load parameter and the material parameter affect the dynamic behavior of the arch. With the increasing of the load parameter, the motion states changed from periodic motion with period 1 to complex motions, such as mult-periodicity, quasi-periodicity or chaos. The increasing of the material parameter benefits the stability of the structures.

Abstract: Based on computational fluid dynamics numerical simulation methods, this article studied the changes of resistance characteristics and tail pressure distribution on the 35° slant angle Ahmed model after installing the rear flaps. The results show that the appropriate size and reasonable arrangement of flaps can make the model tail separated airflow attach on the flap and the flap trailing edge separate again, narrow the tail separation zones, improve the model tail pressure, reduce the pressure difference on the forepart and rear model,lower the model resistance, then causing the drag reduction effect. The study found that the best drag reduction effect is to use 50 mm high flap, decorate in the rear bevel edge from Ahmed model 15 mm, the largest model resistance can be reduced by 5.37%.

Abstract: The paper defines the transmission errors of planetary gear trains, derives from kinetic tooth contact analysis. The method to calculate transmission errors of planetary gear trains is put forward. An integrated platform was constructed for measuring gear noise, vibration and transmission error to verify the effectiveness and feasibility of the analytical. Finally, experimental investigations of the gear noise and vibration spectrum in time domain are introduced, which was solved and simulated in Matlab software.

Abstract: The mechanical property of woven liner spherical plain bearing in different clearance has been analyzed using the finite element software. It indicated that when the positive clearance of woven liner spherical plain bearing is 100um, the maximum stress of its inner ring is the lowest. The position of the maximum stress is in the middle of the inner ring. That makes the bearing has a bigger carry capacity. Based on above analysis, the thermal properties between the friction pair of woven liner spherical plain bearing which clearance is 100um is also analyzed. The node temperature variation trend of inner ring and liner along with the analysis process is obtained.

Abstract: Error modeling and analysis can improve the manufacturing precision and the error compensation accuracy of machine tool. According to the surface of the parts topography information, this paper puts forward a kind of error model of machine tool based on cutter contacting point vector chain. Based on analyzing the cutter contacting point of one tool path which is on the surface of the parts, Based on analyzing action rules of a single cutter contacting point error, the cumulative rules of errors and calculation methods were introduced detailedly, and an application demonstration is given.

Abstract: In order to determine the pipeline characteristics of the sand-wind simulation system, using the closed wind tunnel system, the partial loss of the fan’s pre-axial guide device was obtained from experiments at different openings. The partial loss of the axial guide device was simulated at different boundary conditions with FLUENT [1]. The simulation and experiment results were compared and a plan of setting reasonable boundary conditions was confirmed. A feasible method of using numerical simulation to predict the characteristics of dusty weather simulation pipeline system was developed.

Abstract: This work aims to predict fatigue life of hybrid integrated circuit (HIC) hermetical metal sealing structure mounted on PCB under random vibration loading. The prediction method consists of following steps. Firstly, finite-element model was developed to obtain model parameters (including natural frequencies and mode shapes) and power spectral density (PSD) of the critical part of sealing structure by ANSYS workbench. Secondly, modal test and random vibration test were conducted to verify the results of simulation. Thirdly, the Von Mises stress PSD was transformed into time-history data through inverse Fourier transform with Matlab program after calculating from the FEA results. The rainflow-counting algorithm was employed to evaluate cumulative damages of the critical part. The material’s S-N curve, Palmgren-Miner’s damage accumulation rule and rainflow-counting algorithm were used to predict fatigue life. A specially designed fixture and board with heat sink were used in the experiment to verify the first five mode shapes and response spectrum of the six critical points with hammer excitation. The calculation result of in this study is 70.3 hours which could be a reference for structural design of hybrid integrated circuit hermetical metal sealing under vibration conditions.