Applied Mechanics and Materials Vols. 633-634

Abstract: Development of low-sulfur and Pb-free free cutting steel is significant because the use of S or Pb free-cutting steel can result in serious pollution. The hypoeutectoid graphitized free cutting steel was proposed. The graphitizaion is difficult due to slow graphitization process, so it is curcial to accelerate the graphitization process. The results show that, through appropriate composition design and technology, the C atom can quickly transform to grahite within 4 hours. The microstructure of the graphitized free cutting steel consists of ferrite, graphite and carbide. Moreover, the grain size of grapite is fine and the distribution is uniform, and the carbide mainly locate the ferrtie grain boundary or in the ferrite. In addition, the nuleation of graphite not only can take place on the second-pahse particles, but also spontaneous nuleation and growth.Key words: free cutting steel, hypoeutectoed steel, graphite, carbide, nucleation

Abstract: In this study, the joint strength and microstructure of carbon steels welded by an super-deformation joining process in air were investigated. The two block of model steels are overlapped and heated. The steels are welded with 1000% deformation at approximately 1000°C.The joint strengths are evaluated by uniaxial tension testing. The joint microstructures and fractured surfaces are investigated with OM and SEM. The results revealed that the mechanical properties of joint are close to the matrix’s, the grains adjacent to the interface are merged into one grain, which indicates that both blocks are soundly joined,fracture surface was covered with dimple indicating ductile fracture occurred. Joint fracture behavior is initiated by the brittle fracture of scale inclusions and growth around the internal oxides. Surface scale is the most important factor of sound joining.

Abstract: In this paper, the solidification behaviors of hypoeutectic grey iron under different vacuum conditions in lost foam casting (LFC) were discussed by using thermal analysis method. In order to reveal unique solidification characteristics in LFC, green sand casting (GSC) is introduced as comprehensive study. To comprehensively investigate solidification process, several groups of continuous cooling curves were taken from the geometrical center of the different thickness section (from 5mm to 45mm) of the stepped test bar in practical pouring experiment for the above two processes. And the first derivative of these cooling curves and key temperature points were evaluated. In this paper, through more complete comparative analysis of cooling curves, vacuum environment in LFC would not only change the filling characteristics of melt, but also importantly effect on the further solidification of melts, thereby effect on solidification processes and structural feature of hypoeutectic grey iron.

Abstract: The various chemical compositions of stainless steels can result in complication of the formation of oxide scales in hot rolling process. The time for formation of tertiary oxide scale during finishing rolling is short. In the present study, the oxidation tests with short time period were carried out on eight stainless steel grades by Gleeble 3500 thermal mechanical simulator in a simulated water mist environment. Multi-layers of oxide scale have been developed on all the steel grades during short time oxidation. Internal and intergranular oxides were formed in the steel matrix underneath the inner spinel oxide layer. The cross section of the oxide scales were examined and measured by SEM to understand the oxide scale cross section morphology and thickness.

Abstract: Cooling water surplus heat utilization by lithium bromide absorption heat pump is a significant measure of energy saving in thermal power plants, however, lithium bromide corrosion on tubes seriously affects the reliability of heat pump absorbers. Through weight loss methods and electrochemical polarization methods, corrosion resistance of copper tube and five types of stainless steel tubes 304,316 L,436L,444 and 445J2 have been studied under absorber conditions. The results reveal that the corrosion resistance of five types of stainless steel tubes is significantly better than copper tubes in 62wt-% LiBr solution, and the corrosion resistance of the order of tubes is 316L>445J2≈444>304≈436L>>TP2. Inhibition effect of lithium molybdate is a little better than sodium molybdate at the same weight concentration.

Abstract: The effect of the iPP content on crystallisation, dynamic mechanical relaxation behavior and mechanical properties for high density polyethylene/isotactic polypropylene (HDPE/iPP) was investigated. It was found that crystallinity of HDPE decreased while crystallinity of iPP increased with the increase of iPP content. Two relaxations, namely, γ relaxation associated with amorphous phase of HDPE and α relaxation at positive temperature related to crystalline phase were detected, respectively. γ relaxation of HDPE/iPP blending monofilaments shifted to a higher temperature while α relaxation temperature remained unaffected with raising the content of iPP component. The mechanical properties were significantly affected by the iPP content. Thus, an efficient method to improve the mechanical properties of HDPE monofilaments by introducing iPP component was established.

Abstract: In this paper, we mainly introduces the influence of the processing aids TR131 which namely the lubricating and dispersion agents on the properties of high filled polypropylene. The experiment compared the melt flow rate, tensile strength, bending strength and impact strength of the high filled polypropylene with processing aids TR131 and without it. The results show that high filled polypropylene with Calcium Carbonate could improve the bending strength and impact strength of the pure polypropylene, but the melt flow rate and tensile strength decreased. Incorporation of processing aids TR131 could improve the melt flow rate and the tensile strength of the high filled polypropylene.

Abstract: The mesoscale simulation of polymer blends, Polypropylene (PP) and Polyamide12 (PA12), was calculated by Mesoscopic Dynamic method (MesoDyn). The free energy density, the order parameters and the density profiles were got by the simulation. The evolvement of the phase status was analyzed based on the free energy density and the order parameters. Using density profiles, the kinetics of phase separation was examined and the phase separation behavior was observed. Results showed that mesoscale simulation can be used to determine phase separation of sparingly miscrible polymer blends.

Abstract: Metal rubber material is a mesh structure woven by wire (metal rubber called MR), a new type of isolated-vibrated material with elastic rubber property ^{[1, 2]}. Static mechanical properties of MR are discussed in this paper. First of all, this paper introduces load-displacement function of micro element spring. And a constitutive model of MR is proposed. Secondly, this paper discusses how different parameters such as wire diameter and relative density influence energy dissipation. Also, compared the theoretical results with the experimental results in order to test the accuracy of the theory.

Abstract: The paper mainly concerns about how relative density and pre-compression quantity of metal rubber shock absorber (MRSA) affect acceleration transmissibility, natural frequency and other parameters of MRSA. In order to study the influence law, sine wave sweep experiment was conducted on different MRSA, and the final data was processed. The influence law could provide reference for practical application of MRSA.