Applied Mechanics and Materials Vols. 423-426

Abstract: A three dimensional mathematical model was developed to calculate the displacement of a 350 kA cell with graphitized cathode during preheat and early operation, and the calculated results have been compared and discussed with the measurements. The displacement has been studied for three typical kinds of aluminum reduction cells (semi-graphitic, graphitic and graphitized) after 30 days start-up. First, the sodium concentration distribution after 30 days start-up in cathode carbon blocks was calculated by one FE model of a cathode block. And numerical simulation was utilized to study the displacement fields of the above three typical kinds of the cell, which took the stress caused by chemistry and temperature gradient into account. The results indicate that the value of the cell displacement decreases with time during 30 days start-up and reaches a constant value.

Abstract: The objective of the research was that analyzed the microstructure and mechanical properties of metal part built by SLM in this paper. The tensile samples were made by SLM, the rupture gotten with tensile experiment was scan by SEM, and the rupture property was analyzed. The results of experiment showed: the parts formed by optimized parameters have a density above 96%, a tensile strength of 635MPa, an extension of 55.679% and an average micro hardness of HV307 for stainless steel powder. It is interesting to find that the phase of the built parts is also austenite by XRD, which is the same as that of the starting material.

Abstract: The present article deals with the surface topography during high speed grinding of particulate reinforced titanium matrix composites (PTMCs). Scanning electron microscopic images of the ground surface was analyzed. Combining the results presented in this paper, the following results could be summarized: (1) The reinforcing particles of PTMCs are removed by means of voids, pulled-out, fracture or crushed, and micro-cracks, which attributed to the plowing and shearing during high speed grinding. (2) The formation of the fracture pattern of PTMCs is formed due to the wear debris of the abrasion during high speed grinding.

Abstract: The purpose of this study is to investigate the microstructure, mechanical properties and adhesion of Ti/TiN/TiAlN and Zr/ZrN/TiAlN trilaminar coatings, which were deposited on the high-speed steel substrate and cement carbide substrate by a hybrid PVD coating technique. X-ray diffraction technique (XRD) was used to reveal the structure of coatings. The fracture appearance of coatings was presented by scanning electron microscopy (SEM) and the element content was characterized by energy dispersive X-ray (EDX). Hardness and Yong's modulus were measured by using a nanoindentation technique and the adhesion of coatings was carried out with Rockwell HRC indentations. The results showed that all the coatings present a fcc B1 (NaCl type) structure and the TiN (111) is the dominant orientation. The TiAlN coatings with Ti/TiN interlayer presented a typical columnar structure, while the columnar structure became ambiguous in TiAlN coatings with Zr/ZrN interlayer. The chemical composition of TiAlN coatings is almost unacted on the inner interlayer. The hardness of the coatings on CC substrate is greater than that of on HSS substrate. However, the Ti/TiN/TiAlN coatings on HSS substrate has the maximum the H³/E^*2 ratio at 0.178 with a lowest hardness. The adhesion of Ti/TiN/TiAlN and Zr/ZrN/TiAlN coatings on CC substrate is remarkable greater than the adhesion of same coatings on HSS substrate.

Abstract: The failure time of polyvinylchloride (PVC) insulated power cables was studied using an infrared radiation heating furnace and insulation resistance measurements. The temperature-time curve inside the furnace was similar to that of the ISO 834 standard. Two popular fire protection methods were employed for the cables; one method applied fire-retardant coatings directly on the cable surface, and the other inserted the cables into metal conduits coated with structural steel fire-retardant coating. The results showed that for both protection methods, the failure time of the cable increased with the thickness of the coating. However, if the cable coatings were thicker than 1.5 mm, the coating will crack in the case of cable movement. When the steel structural coating was thinner than 1 mm or thicker than 3 mm, the protective effect was not remarkable for the relatively small expansion multiple. For the longest failure time of the cables, less than 10 minutes in these tests, neither of the two methods was effective in protecting the electrical cables that supply power (on transmit a signal) to equipment required to operate over a relatively long duration in fire conditions.

Abstract: By using the method of low pressure sintering, both of adding and not adding grain growth inhibitor of WC-Co ultra-fine cemented carbide cutting inserts were prepared, tool life tests of continuous cutting superalloy GH2132 were carried out, respectively. ZEISS continuous zoom stereo microscope and microphotograph system were used to observe flank surface wear morphology of the cutting inserts, and analysis the topography and elements of central wear region of flank surface by X-ray energy dispersive spectrometry and scanning electron microscope. The results show that the main wear mechanism of ultrafine cemented carbide cutting inserts is adhesive wear, and the wear resistance of ultrafine cemented carbide cutting inserts that added grain growth inhibitor is superior to no grain growth inhibitor, adding grain growth inhibitor helps increase the resistance of abrasive wear, adhesive wear and oxidative wear as well as diffusive wear of cutting inserts).

Abstract: Effects of different pulse voltage and frequency on solidified structure of superalloy K4169 under low-voltage pulsed magnetic field (LVPMF) were investigated in this paper, and the related mechanism was also discussed. The experimental results show that grain of superalloy K4169 can be refined greatly by LVPMF treatment during the course of solidification. Growth of dendrite is restrained and primary grain is changed from large dendrites to smaller equiaxed grains. When the pulse voltage is at 0-280V, grain size of the alloy decreases as pulse voltage increases, and primary dendrites are fractured from well-developed dendrites into fine equiaxed grains and non-dendritic structures. When the pulse frequency is at 0-5Hz, the increase of pulse frequency enhances the refinement effect of LVPMF processing. With the increase of the pulse frequency, grain size of the alloy increases.

Abstract: Transmittance is the key factor to the quality of solar glass. At present visible light transmittance (380-780 nm) and solar direct transmittance (300-2500 nm) were used to evaluate the light transmission property without considering the specificity of solar glass. In this work a new parameter of effective transmittance in the 380-1200 nm region which was consistent with the spectral response range of solar cells was proposed and calculated to evaluate the property. The value of effective transmittance lies between that of visible light transmittance and solar direct transmittance. Using effective transmittance instead could reflect the performance of solar glass on real applications properly.

Abstract: A new stretch-forming process based on discretely loading for three-dimensional sheet metal part is proposed and numerically investigated. The gripping jaw in traditional stretch-forming process is replaced by the discrete array of loading units, and the stretching load is applied at discrete points on the two ends of sheet metal. By controlling the loading trajectory at the each discrete point, an optimal stretch-forming process can be realized. The numerical results on the new stretch-forming process of a saddle-shaped sheet metal part show that the distribution of the deformation on the formed surface of new process is more uniform than that of traditional stretch-forming, and the forming defects can be avoided and better forming quality will be obtained.

Abstract: An end mills wear experiment was designed to model and predict the end mills wear in micro turn-milling process. Based on the on-line visual measurement system, the tool wear was measured, then micro turn-milling tool wear regression models were established according to Response surface Method (RSM). The relationship between cutting parameters and tool wear was discussed in detail. The results indicate that the regression model can predict the value and regularity of end mills wear accurately, which can provide guidance on improving machining precision and quality in micro turn-milling process.