Key Engineering Materials Vols. 462-463

Abstract: Al-2%Mn alloy matrix composites reinforced with Al2O3 particulates was fabricated by stirring cast, and the composites was characterized and analyzed by using a variety of analytical techniques, such as XRD, SEM, EDS, Brinell hardness tester, ring-on-block tribometer, and erosion-corrosion tester. The results show that the composites in as cast condition is mainly composed of Al,  -Al2O3, MnAl6 and Al11Mn4 phase, and the Al2O3 particles are dispersed uniformly in the Al matrix. Compared with the base aluminium and the Al-2%Mn alloy, the HB hardness of the composites is increased significantly, and the wear loss is far less under the SO4•Cl- Na•Ca• Mg corrosive alkalescent aqueous solution lubricated condition. The erosive-corrosive wear rates of the composites are lower than those of the Al-2%Mn alloy irrespective of the rotational speed or the size of grinding particles. The Al2O3 particulates reinforced Al-2%Mn alloy matrix composites possesses a good wear-resistance and erosion-corrosion resistance due to its higher hardness.

Abstract: A low-cost direct metal RP process based on the plasma arc welding (PAW) is presented. The impacts of two important process parameters (pulse current and wire-feeding speed) on the distortion of the substrate are investigated. The temperature field and the distortion of the depositing process are simulated by finite element analysis. The results show that the heat input and the quantity of the metal fed into the molten pool influence the distortion of the substrate. Higher pulse current and wire-feeding speed will bring on larger distortion.

Abstract: Meshing for finite element analysis accuracy plays a very important part in numerical simulation of Periodic Symmetric Struts Support (PSSS). Different accuracy can be obtained by different element sizes or types. Three element types and eight element sizes are used for comparing the accuracy of modal analysis in this paper. Comparing with the mutual relations of different accuracy, the scientific basis is provided for selecting the correct mesh size and improves the efficiency of numerical calculation in modal analysis.

Abstract: In this paper, in order to overcome the technical difficulty of center level height of Periodic Symmetric Struts Support (PSSS) by using the test in the field and reduce the high cost of testing, the method of the finite element analysis by considering thermal condition and the dynamic response is used and the center level height of PSSS is evaluated. Some relations for center level height changing process of PSSS were found and some parametric effects are obtained for the stability analysis of gas turbine by changing the number of struts support and angle.

Abstract: Wind-Blown sand movement is a complicated, non-linear, self-organized and two-phase flow. Conventional theory of mechanics and existing experimental observation method can’t describe that inherent mechanism exactly, and then appeared much difficulty of numerical method for computational simulation of wind-blown sand movement. In this paper, the smoothed particle hydrodynamics (SPH) method is used for simulating the wind-blown sand movement process. According to the characteristic of wind-blown sand movement the sand grains phase and the gas phase are modeled by considering the different kernel function and the particles size, mass, density, velocity and other physical quantities, which can movement along with controlling equation. Finally the numerical simulations are conducted for wind-blown sand movement and some reasonable results are obtained.

Abstract: Electrochemical finishing (ECF), which is based on anodic electrochemical dissolution (ECD) process, appears to be very promising as a future finishing technique, since in many areas of applications it offers attractive advantages over traditional finishing processes such as its applicability regardless of material hardness, no cathode tool wear, smooth and bright surface, and a wide range of materials that can be finished. Therefore, in this contribution, a review is presented on current research, advancement and industrial practice in ECF. This paper highlights the influence of various predominant factors of ECF, including power supply, design and advancement of cathode tool, etc. The finishing mechanism of ECF and its hybrid processes are also concerned in this paper.

Abstract: In this paper, the sand break into highway problem in desert, which is caused by the sand flow blown by wind, is studied. The mathematical models are introduced by considering the fixed, semi-fixed and free sand desert fields based on the fluid dynamics and the sand particle dynamics. Different kinds of numerical models are made by changing the desert highway height, wind flow direction and its uniformity. The weak coupling method is used due to spatial relationships between air flow field and the sand flow field. Finally, by coupling the airflow field and sand flow field with desert highway, the numerical simulations of sand forming process on desert highway are conducted. The numerical results shown, that the wind blown sand breaks into highway easier when wind direction perpendicular highway and if the highway height higher than the range size of the sand surface the wind blown sand break into highway is more difficult.

Abstract: Wind caused the much sediment fluxes leading to both erosion and deposits in the sandy desertification area, and the much kind of beautiful sandy desert morphologies are formed. This is really crucial to the development of the dynamic behaviour of aeolian transport of sand particles. The sand desert morphologies are representing significant information archives for understanding the desertification problem. Dynamics and numerical modeling provides an essential tool for studying the aeolian transport of sand particle and morphology of sand desert such as ripple and dune. In this study, the mathematical models based on the dynamics are analyzed by considering the several keys as saltation, creep, suspension, avalanche and its threshold condition etc. for sand morphology forming processes. Then due to sand flow field real characteristics, the establishing process of stream flow field are analyzed, and the implication relationships as well as the coupling process between uniform stream flow field and the sand flow field are analyzed. Finally, the sand flow field models is discretized, and different kinds of sandy desert morphology are simulated by considering the sand particle size and mass in fixed, semi-fixed and free sand flow field area.

Abstract: This article studies the effect of Uyghur sand therapy on rabbit femur bending mechanics. Methods: Papain was injected into the joint space of right knee of 20 male rabbits. The Paptain injected rabbits were divided into two different groups: sand therapy group and control group. The control group rabbits weren’t interfered in any way. The sand therapy group rabbits were given sand therapy for 30 minutes each day for 15 days. On the 16th day, the femur of each rabbit was taken as specimen. The specimen was given the tree-point bending test and the load-deflection curves were obtained. Then Finite Element Ansys method was used to analyze the stress cloud and the deformation cloud; Results:. Damage occurred in the position where the first maximum main stress was given; the form of damage was a brittle fracture. However, the position which corresponds to the maximum bending compressive stress has not been damaged. Finite Element Ansys analysis also showed a similar result. Conclusion: Sand therapy can improve femur bending strength and toughness.

Abstract: The work presents a summary of previous studies on fatigue crack propagation within various Aluminum alloys. The effective characteristics on crack growth are first highlighted and the influence of surface engineering such as polishing, shot peening and skimming to enhance the failure resistance are discussed. Several different existing developed models for predicting the rate of crack propagation are compared in terms of incorporated effective parameters. Finally numerical and computational analyses as the accurate, fast and cheap methods which have attracted the Engineers’ interest are reviewed and compared with other methods.