Applied Mechanics and Materials Vol. 248

Abstract: In order to solve much energy waste of the ammonia refrigeration system, we analyze many parameters and processes in depth theoretical methods, experimental verification and numerical simulation in actual working condition. The results show that improve suction pressure and reduce exhaust pressure can reduce energy consumption of the system. The value of suction pressure and exhaust pressure is the optimal value when corresponding superheat degree and super cooling degree are 1°C. Control the pressure difference between inlet and outlet of compressor by increasing the exhaust pressure; the system is more stable and less energy loss. Take advantage of bypass channel to control the superheat degree is more effect than by evaporator itself. The air volume of condenser fans should adjust with its load and the outdoor dryness temperature. When the ratio approaches to the load one, the total energy consumption decreased obviously.

Abstract: For the commonly used wet cylinder liner assembly characteristics and structure of water-cooled internal combustion engine, the influencing factors of wet cylinder liner deformation in the assembly conditions are calculated and analyzed using finite element method. Mainly from the matching stiffness of block-cylinder liner-gasket-cylinder head assembly, the local stiffness of the cylinder head, cylinder head bolt preload and the structure form of cylinder liner, get the influence laws of the various factors on the cylinder liner radial deformation and its each order Fourier series deformation, which provides guidance direction to control the cylinder liner deformation under assembly loading.

Abstract: Aiming at the importance of the microcosmic topography of connecting surface and bolt assembling technique to the bolt connection performance, the fractal characteristic of bolt joint rough surface is studied based on the power spectrum of its micro surface profile. Fractal models of 2D and 3D rough surfaces are presented by W-M function and the 2D and 3D bolt joint rough surfaces are reconstructed. Imageware and Pro/e are used to build the bolt connecting model based on the real rough surface presented by W-M function. The preload is imitated by the PREST179 element. The finite element transient analysis is used to imitate the speed and force size of the bolt tightening. The relationship model between tighten speed, preload size and connecting performance whose target is contact stress is presented based on the finite element analysis results. According the model, the single bolt precise assembling technique is obtained.

Abstract: This article states seal clearance and fluid leakage.By means of pressure distribution calculation and theoretical analysis, theoretically it establishs the mathematical model of the leakage with liquid material, the sealing structure and the fuel tank between the internal and external pressure.The whole processes on Matlab platform meet the complex engineering requirements,so the calculation process is simple and convenient. By calculating the results should be very intuitive, it closes to the sealing gap and leakage distribution curve. Thus, it is sure sealing clearance is the first element in the ultra-high pressure seal system.

Abstract: Jet pump has different basic characteristics when it is used in different working condition. According to the model of jet pump unloading system used in the oilfield, the lab experiment use high pressure pump to provide high power liquid and suction liquid, and also making use of throttle valve providing back pressure condition, to simulate the condition of oil well unloading system much better. The experiment tests pressure and flow of power liquid, suction liquid and mixture liquid , and achieve the basic characteristic curve of jet pump. The result show that according to the different application conditions, can change the jet pump efficient working area range when needed, by adjusting the distance between nozzle and throat, and the optimal distance is the diameter of nozzle 2~3 times.

Abstract: The 3D engineering surfaces are comprised of a range of spatial frequency components, such as form, waviness and roughness. Filtering techniques are commonly adopted to separate the different components. To overcoming the shortcomings of traditional filtering method, a new separation method is proposed with the correlation analysis of sub-bands in nonsubsampled contourlet transform (NSCT) domain. The 3D engineering surface topography is decomposed into different sub-bands by NSCT, and the correlation coefficients of NSCT sub-bands with its parent and children sub-bands are calculated by Pearson correlation method. Then the roughness, waviness and form of 3D real surface topography are restructured respectively by the inverse NSCT based on the NSCT sub-bands which belong to different components. Finally, a group of 3D engineering surfaces are separated into different components, and the result shown that the proposed method can separate 3D engineering surface effectively.

Abstract: Mission reliability model is important for evaluation of the production capability of a manufacturing system. The manufacturing system mission reliability refers to the ability that the manufacturing system completes the production mission under specified conditions and within the specified time. The production mission includes two factors: quality of products and the productivity. Calculation of traditional evaluation parameters like Cpk and Ppk excludes the abnormal interruption of production and inspection errors. For some manufacturing systems with low degree of automation in the field of domestic weapons, both production disruptions and misjudgments in inspection processes have an impact on the mission reliability of the manufacturing system. A method of mission reliability modeling of discrete manufacturing system is proposed in this paper. The manufacturing system is composed of several processes. Abnormal interruption of production, inspection errors and substandard quality parameters of the products are involved in the modeling of the process mission reliability. The sequential and concurrent relationship between the processes is also taken into account in the modeling process.

Abstract: Optimal selection of cutting parameters is one of the significant issues in achieving high quality machining. In this study, a method for the selection of optimal cutting parameters during lathe operation is presented. The present study focuses on multiple-performance optimization on machining characteristics of St-37 steel. The cutting parameters used in this experimental study include cutting speed, feed rate, depth of cut and rake angle. Two output parameters, namely, surface roughness and tool life are considered as process performance. A statistical model based on linear polynomial equations is developed to describe different responses. For optimal conditions, the Non-dominated Sorting Genetic Algorithm (NSGA) is employed in achieving appropriate models. The optimization procedure shows that the proposed method has a high performance in problem-solving.

Abstract: The stability and performance of the web running is one of the key factors of printing quality. Through the analysis of the mechanical structure of web running, movement rules and dynamic characteristics of the tape established the physical simulation model. A physical simuliation platform of the web-fed system was built based on technical load testing about feeding device, the feed rollers and tension control, a guidance for optimizing the structure, designing of high-performance presses on the basis of the experiment and web running was provided.

Abstract: Plasticity induced crack closure (PICC) simulation using finite element analyses has been concerned by many researchers. In the present investigation elliptical corner fatigue crack growth from a hole was predicted using PICC method. An elastic-plastic finite element model is built with a suitably refined mesh and time-dependent remote tractions are applied to simulate cyclic loading. In a 3D geometry the crack opening value will vary along the crack front. For simplicity this shape evolution is neglected and the crack front is extended uniformly. Predicted fatigue life using crack closure method for elliptical corner crack is in good agreement with the experimental data. The results obtained highlighted the sensitivity of crack closure method to the opening stress intensity values.