Applied Mechanics and Materials Vols. 138-139

Abstract: Rock burst is a geological hazard which occurs when hard and brittle rock mass is excavated under high in-situ stresses or high stress concentration. The Qirehataer diversion tunnel has 15.66 km long at a maximum depth of 1720 m. About 64.5% of the tunnel is located in gneissic granite. During excavation of the tunnel, light to moderate rock burst occurred in about 300 m length of the tunnel. This paper provides the analysis of the characteristics and stress conditions in the rock burst site using the stress conditions around the excavation, and provides an explanation on the reasons why rock burst occurred from the beginning to middle of the vault on the right side of the tunnel section, and the most serious situation is located at 60° with respect to horizontal. Stress release hole and bolt or bolt and net are used to prevent and manage rock burst which have been shown to be effective in this case.

Abstract: In this paper, the microstructure of the water strider’s legs was observed, the lengths, diameters of the water strider’s legs were measured by the instruments such as scanning electron microscope . The supporting force model of water strider’s legs was established, the factors associated with the supporting force were analyzed. The critical conditions in which water strider’s legs do not pierce the water surface were discussed. the maximum supporting force of water strider’s single hind leg was calculated according to the supporting force model of water strider’s legs, the calculated value is 3399.13×10^-6N, which is about 17 times of its body weight.

Abstract: This thesis investigated the mechanical property of the semi-rigid steel beam-column connection and its influence upon the propery of the framework; grounded on several foreign common mathematical models on the moment-rotation relationship of semi-rigid connection, and on the basis of exponent function model, it derived the ultimate bearing capacity (M_μ) and initial connection stiffness (R_ki) which act as controlling function in the formula. Also, it imitated the typical connection of top-seat-angle with double web-angle, ensured its moment-rotation curve, and provided a reference for the analysis of the ultimate bearing capacity in the second-order effect of light steel frame structure.

Abstract: The Influence of moisture content on the performance of desulfurization plasterboard is studied by a series of experiments in this paper, it investigates the law of absorption procedure and relationship between density and moisture content. At the same time, this paper studies on the fracture load, which is varying with different moisture content of the plasterboard. Finally, we do the research on the change of impact resistance performance of plasterboard with the increase of the moisture content, and get some conclusions about the plasterboard production and application for the future reference.

Abstract: The temperature stress crack ^[1] in wall reduced the quality of wall, at the same time made sensory and psychological adverse effects on the residents. This paper is based on principle of temperature stress cracks, use ANSYS to establish models of concrete perforated brick masonry, through research on the maximum stress and horizontal displacement of the top end by finite element method, mainly studies on the influence of door and window openings on temperature effect of masonry, and advices the porosity of building exterior wall should be take 11.6 ~ 23.2%.

Abstract: The water entry of two-dimensional body with flow separation is simulated based on potential theory and boundary element method. The double point model and four-order Runge-Kutta method and jet-cut model and free surface smooth technique and regrinding technique are used to assure the stability and accuracy of the numerical result. A flow separation model is introduced to simulate the water entry of two-dimensional body with knuckle. The free surface elevation and pressure distribution of wedge with knuckle are predicted and compared with other theory result. Good agreement between numerical result and other theory result is indicated that the numerical method is stability and effective.

Abstract: In this paper, taking the high-power low-speed diesel engine as a study object, aiming at the key components' reliability analysis, a series of methods is proposed based on the finite element analysis. That is, the strength and fatigue analysis of the engine's body, the bending and torsion fatigue analysis of the crankshaft, the thermal fatigue and mechanical fatigue analysis of the cylinder head-piston, the wear analysis of the valve-seat, the structural-thermal coupling analysis and the other methods. The dynamics test system of the valve gear is built to provide the technical preparation for optimizing the diesel engine's structure.

Abstract: Analysis and calculation of stray light is important to improve the performance of infrared detection system. In this article, we mainly discussed two sources: earth and atmosphere emission and thermal stray radiation. A method based on Monte Carlo ray-tracing in TracePro is proposed to calculate the irradiance of detector arisen from earth and atmosphere emission. The thermal stray light irradiance on detector can also be obtained by simulation in TracePro.

Abstract: Fan is a pneumatic device in the 4ZTL-1800 combine harvester threshing prior to cutting. Based on the prophase search result that fan noise is highest when fan rotates at 1200r/min, in order to decrease noise of it, sigle-microperferated-panel muffler, double-microperferated-panel muffler and interposition muffler were designed and tested. The results show that double-microperferated-panel muffler is best and sound power level of fan is decreased 11dB, and that interposition muffler is better, and that sigle-microperferated-panel muffler is worst to descrease fan noise. Through contrast on transmission power loss of different mufflers, cone-shaped double-microperferated-panel muffler is verified to be best for noise control of fan.

Abstract: Fan is used for pneumatic conveying grain in the 4ZTL-1800 combine harvester threshing prior to cutting. In order to decrease power consume of it, the experimental modal analysis of fan was done by using hammer-hitting pulse-inspirit method. The natural frequencies of fan vibration is obtained, which is contrasted with inspirit frequency of fan, then resonance vibration of fan is found and its frequency is at 125Hz, which verifies the result of the experimental modal analysis.The results are beneficial to decrease power consume of fan.