Applied Mechanics and Materials Vols. 66-68

Abstract: When the metal - carbon eutectic gets phase transition, the graphite crucible will be effect by the thermal stress and the phase transformation stress, which often make the crucible rupture, fail to achieve durability requirements, and then affect the research of high temperature eutectic fixed-point’s long-term stability and reproducibility. In order to improve the durability of crucible, the finite element software ANSYS and direct coupling method were used in this paper to analyze the heat-stress of Pt-C fixed-point crucible with sleeve (graphite sleeve) during the solidification. Based on the results of the simulation, we analyze the reasons of the breakdown of the crucible and propose two measures to improve the durability of crucible, which are adding graphite cloth or graphite foil between the crucible and the sleeve. Then we use ANSYS to analyze the two improved crucibles, and prove the effectiveness of these two measures.

Abstract: Chlorophytum comosum seedlings were treated with different Zinc (Zn) concentrations (CK, 200, 400, 600, 800, 1000, 1500, 2000 mg·kg^-1dried growth medium) under controlled conditions. Physiological parameters and Zn content of roots and shoots were examined by pot-planting over a period of three months. The results showed that the length of roots, the fresh and the dried weight of plants were inhibited by Zn of all concentrations, while the length of aboveground parts and the volume of roots were stimulated by the lower Zn level. The Tolerance Index (TI) of C. comosum were above 50 in soil of Zn concentration less than 600mg·kg^-1. In addition, results indicate that C. comosum can accumulate Pb up to 1093 mg·kg^-1 and 4700 mg·kg^-1 dry weight in roots and leaves respectively in Zn concentration of soil up to 2000 mg·kg^-1.

Abstract: Composites have become valuable construction materials in the aerospace, defense, automobile, and civil industries due to their superior mechanical properties. However, there are significant differences between the machining of metals and alloys and that of composites, because composites are anisotropic and inhomogeneous. Drilling with a conventional twist drill is characterized by a relatively large thrust force due to a negative rake and negligibly small cutting speed at the chisel edge. Such a large thrust force causes defects and damages the composites, leading to poor hole quality, and reduced in-service life under fatigue loads. Although significant efforts have been made to realize the thrust force of twist drill, there are few papers reporting the effect of peripheral drilling moment (torque) on delamination in drilling composite materials. In this paper, an attempt is made to develop the critical thrust of the twist drill with peripheral drilling moment using linear elastic fracture mechanics (LEFM) and energy conservation. The theoretical results agree well with the practical experience in industries.

Abstract: Effect of porosity distribution in the weld metal of AA 6061-T6 with 6 mm thickness plate using two dissimilar filler metals in the gas metal arc welding (GMAW) process was investigated. This paper provides a characterization of the porosity in term of the distribution, location and size of the pores in the weldment region. The porosity characterization was made by using 3D X-Ray Computed Tomography and Scanning Electron microscope. The existing pores resulting from the cause of the filler metal in welded alloy used ER4043 (Al-5Si) was compared with the weldement used ER5356 (Al-5Mg). From this investigation, it is exhibited that the pores only distributed and located mainly at the edges and at the root of the weldment with ER5356 weld metal, however, for weldment with ER4043, the pores were mainly scattered in the centre region. The distribution and location of pores in weld metal is believed due to the effect of convections in the molten metal, solidification rate and also from the gases induced during the weld process. Apart from that, results of tensile test indicated the weldment has affected the strength and ductility of the two different fillers selected. AA6061 with ER5356 are dropped 50% in ultimate tensile strength (UTS) and 40 % in elongation; meanwhile AA6061 with ER 4043 was dropped 70% in UTS and 90% in elongation. The different principle alloying element of these two filler metals have play significant role in the distribution of porosity in AA6061 weldment and had influence the strength and ductility of the weld joint.

Abstract: The organic material named 4-amino-5-phenyl-4H-1, 2, 4-trizole-3-thiol (APTT) was studied as inhibitor for mild steel corrosion in 1.0 M HCl at 30 °C. The effects of turbulent flow on the inhibition process were characterized using open circuit potential (OCP), potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Turbulent flow condition experiments were simulated by Rotating Cylinder Electrode (RCE). Results obtained from changes of open circuit potential (OCP) with immersion time, potentiodynamic polarization, and impedance measurements all are in good agreement and indicated that the formation and the development of the inhibitor film were flow rate dependence. The scanning electron micrograph confirmed film structure is dependence of flow condition.

Abstract: In this paper, the hemming process, which widely used in automobile industry, was studied by a method of constructing mechanical models combined with FEM simulation results. The warp producing mechanism in the straight edge- plane hemming process was analyzed in detail using this mechanical model. The reason why the warp produced at the position of near the contact point between the out panel and the position surface of hemming die during the pre-hemming process, and the phenomena of warp reducing firstly and then increasing before the position point T and the warp reducing again after point T during the final hemming process were interpreted. The work finished in this paper provides a theoretical basis to understand hemming process and a tool to analyze the reasons why warp produced in the hemming processes.

Abstract: The vibration characteristics of the thermoelastic coupling rectangular plate under the action of uniformly distributed tangential follower force are investigated. The coupled thermoelastic differential equation of the plate under the action of uniformly distributed tangential follower force was derived. Dimensionless complex frequencies of the thermoelastic coupling rectangular plate with one edge clamped and other three edges simply supported, two opposite edges simply supported and other two edges clamped were calculated by the differential quadrature method. The effects of the dimensionless thermoelastic coupling factor on the stability and critical load of the thin plate were analyzed. The results show that the flutter loads of the coupled modes increase with the increase of the dimensionless coupled thermoelastic factor and the aspect ratio.

Abstract: To meet the air emergency evacuation needs of aircraft flight test team members, we developed the air emergency opening system of aircraft service port. During the flight tests, the probability of false triggering of the electro-explosive system used in the emergency opening system is called for not more than 0.001 in the confidence of not less than 90% under the interference of external electromagnetic radiation, and when the aircraft experience an emergency, the electro-explosive system can work reliably according to the preestablished instructions to detonate the detonation power unit of the emergency opening system, and the service port will be pushed into the cabin fast and accurately, so that the aircrew could bail out of the aircraft by the barrier-free access. Therefore, this paper examines the electromagnetic radiation environment of the inner and outer fuselage of the aircraft, and then analyzes the hazard of the electromagnetic environment to the electro-explosive system of the emergency opening system as a base for the safety design of the anti-electromagnetic radiation of the emergency opening system.

Abstract: To circumvent the poor prediction accuracy of traffic volume models available due to the lack of traffic data and inaccurate judgments on the traffic influence factors, in this paper we established a traffic volume prediction model using grey forecasting model GM(1,1) based on the real traffic data from the highway toll database. The GM(1,1) method has advantage of the strong adaptiveness to Complex system, thus getting a great advantage over other methods for modeling such a complex nonlinear traffic volume system with many uncertain influence factors. Simulation results show that our GM(1,1) model has mean relative prediction error of 3.9%, which accomplishes our intended prediction accuracy.

Abstract: Machining deformation has always been a bottleneck issue in the manufacturing field of aeronautical monolithic components. On the base of finite element method, the effect of the process steps and tool paths on the workpiece stiffness and the redistribution of residual stress in the machining process of aeronautical frame monolithic component was investigated under the given fixturing scheme. Thus, the prediction of the workpiece deformation can be carried out in reason. The proposed simulation approach to deformation analysis can be used to observe the true characteristic of milling forces and machining deformations. Therefore, the proposed method can supply the theoretical basis for the determination of the optimal process parameters.