Papers by Author: Mamtimin Gheni

Abstract: In this research, the FEM models of sealing rings for welding bellows mechanical seals were established by applying both isolation and integral contact method, and the displacement and stress of sealing ring’s were calculated. The result shows that a wedge-shaped was appeared on the seal face under the medium pressure and spring force. It can be seen that the integral contact analysis effectively illustrated that the convergence and divergence of the wedge-shaped deformation will be occurred in the contact face. The researching results provide a theoretical basis for the furthermore analysis of the deformation and frictional wear and structure optimization of sealing rings for welding bellows mechanical seal.

Abstract: Smoothed particle hydrodynamics (SPH) method is used to simulate the lift-off phenomenon of sand particles in the air flow. Whether the sand particles make any form of movement in the air flow, firstly, they always jump into the air from a standstill condition, so it is helpfull to understand the saltation mechanism of sand particles. Because the computitional region is discreted into particles in the SPH method, the movement of each particle can represent the machnical behavior of sand particles if the particle dispersion has the same characteristic with the sand particles. The foundmental theory of SPH method and its key elements are reviewed in detail, such as the kernel function, the choice of smoothing length and their influence on the numerical simulation results.In this study a numerical simulation model of wind-blown sand two-phase flow using SPH model is proposed and then the model is discreted to simulate the take-off process of sand particles with adquate boundary conditions. Simulation results show that the proposed model can be used to simulate the dynamic characteristics of sand particles in lift-off.

Abstract: In this paper，the simplified three-dimensional model of Periodic Symmetric Struts Support (PSSS) was established, which is applied to a certain type of gas turbine. The software of computational fluid Dynamics (CFD) and the standard k-ε turbulence model are used in the numerical simulation．To simulate the coupling problems of fluid and solid，the numerical models by considering the heat transfer problem coupling with the solid and fluid have been developed．The internal flow field in PSSS was numerically simulated by an effective method for solving integrated coupling problems. The temperature field and thermal deformation rule of the PSSS was obtained. Through comparison coordinate values of the checked points before and after thermal deformation, the impact of thermal deformation on bearing center level height under temperature load was studied. The centering process of the PSSS at high temperature state was verified.

Abstract: Existence of back tempered regions in laser hardened materials is a common industrial problem. As a result of back tempering, the areas have lower hardness compared to hardened areas, becoming a potential breakage starting point. In this research Laser hardening is applied to AISI 1060 work piece to analyze relationship between laser beam parameters and back tempered region. Analytical model for thermal cycle similar to experimental condition is built and results from experiment and modeling are compared.

Abstract: In this paper, based on survey data of delays on intersections in urban highways and in accordance with theoretical capacity of each traffic lane, various reasons of delay in intersections are analyzed numerically. A discrete traffic model to simulate traffic in intersections using Gaussian mesh method is built. After modifying intersection properties, weight of each factor in terms of their effect to capacity is acquired. An optimized way to solve traffic delay is hereby recommended.

Abstract: In this paper, strength evaluations and reliability analysis are conducted for different types of PSSS(Periodically Symmetric Struts Supports) based on the FEA(Finite Element Analysis). The numerical models are established at first, and the PMA(Prestressed Modal Analysis) is conducted. The nodal stress value of all of the gauss points in elements are extracted out and the stress distributions are evaluated for each type of PSSS. Then using nonlinear least squares method, curve fitting is carried out, and the stress probability distribution function is obtained. The results show that although using different number of struts, the stress distribution function obeys the exponential distribution. By using nonlinear least squares method again for the distribution parameters a and b of different exponential functions, the relationship between number of struts and distribution function is obtained, and the mathematical models of the stress probability distribution functions for different supports are established. Finally, the new stress distribution model is introduced by considering the DSSI(Damaged Stress-Strength Interference), and the reliability evaluation for different types of periodically symmetric struts supports is carried out.

Abstract: Bone forming phenomenon is an exquisitely genetic programmed and dynamic process that occur from early embryo skeletal development to postnatal growth and culminating in the formation of highly variable and complex but perfect optimized structures. In this study the high resolution imaging techniques such as computerized tomography (CT) is used to obtain quantitative information about the progressive changes in three-dimensional (3D) skeletal morphology and density of rabbit thighbone during early embryo skeletal development to postnatal growth. Then the changes of the thighbone volume, shape and density during the bone growth process are evaluated by using the 3D images reconstruction method, and the growing direction of the thighbone structure is also evaluated. The effects of genetic and environmental complications to optimized skeletal patterns of bone are discussed.

Abstract: The piston is a key moving-part of the reciprocating piston compressor with a high failure rate. Because of the difficult exact calculation of machinery dynamic, the traditional and common way to find the reason of fracture is based on metal-lographic phase of piston material. The C102B reciprocating piston compressor is an important equipment in methanol plant. In this paper, in connection with the piston fracture of the C102B fresh air compressor on service , besides a lot of analysis on metal-lographic phase, the 3-D model of piston and cylinder were built-up, and the two dangerous places where the piston suffered max-force were found. Bases on ANSYS and FEM technology, the value of max-force on piston at the two places were carried out. Finally, the reasons of piston fracture of the C102B fresh air compressor were found and some preventive suggestion was proposed.

Abstract: With the necessity and importance of reconstructing medical image model on the medical application and research, a variety of methods reconstructing human body tissues were introduced according to different original data and application purposes. The different reconstruction processes of human pelvic tissues, molar and incisor models are detailed. This proves the validity and feasibility of the different means.

Abstract: In order to research the surface integrity of SEAM, the surface figure, surface heat-affected zones (HAZ ) and surface hardness are analyzed. The author mainly researches the influence factors of water pressure, air pressure, cathode feed rate and relative line speed on processing indictor. The orthogonal experiment results indicate that the main influence factors of surface roughness and HAZ are air pressure, gap voltage and cutting depth. In SEAM, certain scope pressure atomization of dielectric liquid has deionization and arc-extinguishing effect, and takes away melted metal and heat from the discharge channel in time. Workpiece surface will be smoothness. However, the enlarged air pressure will break normal electrode discharge and make the surface smoothness worse. The research of influence of gap voltage on surface quality are accomplished.