Applied Mechanics and Materials Vol. 251

Abstract: After tool edges sharpen, there are a variety of micro-defects in the area of edge, which will accelerate tool wear and shorten tool life. In order to increase tool life and production efficiency, the area of edge strengthen was needed. In this paper, the electrolysis technology was used to enhance the cutting edge of high-speed steel(HSS) tap, the rounding of the edge region of the forming edge and surface morphology of cutting edge were investigated. And the tapping tests were carried on the Ti6Al4V. The results showed that electrolysis enhanced technology can eliminate the defects, invert a circular edge and improve the tool edge strength. The original tap was worn rapidly in the early stages of wear and the cutting force was changed big variation. The results showed that tap strengthened can reduce tool wear and improve tool life.

Abstract: Spherical sponge iron (SSI) with high activity and intension could be prepared through direct reduction by charcoal or hydrogen. The capability of cadmium removal by SSI was investigated in. It was suggested that the reaction of SSI reduced by hydrogen was higher than that reduced by charcoal, and the increasing rate of pH and cadmium removal in solution by SSI reduced by hydrogen was higher than that reduced by charcoal. Moreover, cadmium removal percentage by SSI reduced with hydrogen was much higher than that reduced by charcoal. When the original concentration of cadmium was 50mg/L, cadmium removal by SSI appeared to be the pseudo-first-order reaction because the reaction order was from 0.861 to 0.984. The apparent reaction rate constant of cadmium removal by SSI reduced with charcoal was 0.586 h-1. While hydrogen was utilized as reduction agent, the apparent reaction rate constant of cadmium removal was increased by 7.3 and 13.7 times.

Abstract: Spherical sponge iron (SSI) with high activity and intension could be utilized to remove nitrate from wastewater. Reduction product of nitrate by SSI was investigated through static state experiment combined with E-pH diagram of Fe-N-H2O system. In a certain range of pH and redox potential, the speciation of iron include Fe0, Fe2+, Fe3+, Fe(OH)2 and Fe(OH)3, and the speciation of N was NO3-, N2, NH4+, or NH3 as the initial speciation of N was nitrate. pH in solution increased to above 10 in 6min because of quick erosion battery reaction of zero-valent iron in solution. Moreover, the E value in solution declined quickly to the minimum and then increased slightly because of dissolution of oxygen from atmosphere. It was suggested that nitrite was the intermediate product during reduction of nitrate by SSI, and ammonium was the finial product of nitrate and nitrite reduction. Nitrate removal from wastewater was related with escape of ammonia, which was gas state of ammonium in water, when the water solution was alkaline.

Abstract: Gas quenching steel slag (GQSS) without any post treatment and modification could be utilized to remove Cr(III) from wastewater. Due to lower content of reductive material in GQSS, it was suggested that dissolved oxygen in solution should be declined slightly to the minimum with libration time, and then increased as the testing centrifuge tubes without lids because of dissolution of oxygen from atmosphere. Dissolved oxygen chromium original have significant influence on redox potential in solution. pH increased with the increasing of libration time because of dissolution of alkaline material in GQSS. But dissolution oxygen has little influence on pH in solution. It was suggested that Cr(III) removal percentage when the solution was sealed from atmosphere was slightly higher than that as the soltuion without seal, which was related with the influence of dissolved oxygen on pH and redox potential in solution.

Abstract: In the paper, the steel intergranular corrosion of 304 stainless steels was studied in detail with the method of copper sulfate. The macro morphology, mechanical property and metallurgical structure were also discussed by contrast of before and after corrosion. The results indicated that many trans-crystalline cracks and micro cracks were found on the surface of stainless steel. The max bending force was decreased from 7.225KN to 4.926KN; the deposited carbide was seen on corroded grain boundary with the dropping of grain. The conclusions are important to analysis of surface corrosion of stainless steel.

Abstract: In this paper, the experimental research on crack of four recycled aggregate concrete simple beams under a concentrated load was presented. Through the analysis of evolution and distribution characteristics of cracks with different amount of recycled brick, it is verified that the surface cracks on the recycled aggregate concrete beams have a very good fractal behavior. The research shows that the content of the recycled brick has obvious influence on the fractal dimension of the surface cracks of the beams. The more the content of the recycled brick is, the bigger the fractal dimension is. So the fractal dimension can be regarded as an index to evaluate damage degree of the recycled aggregate concrete beam. This research provides a novel idea and a method for studying the damage of the concrete structures.

Abstract: One of promising candidates as dopants for forming ultra-shallow and high conductive source/drain in future silicon devices has been proposed to be dimer or trimer co-dopants containing pairs or trios of different impurity elements. Making choice of a combination of the impurity elements with a small ionization energy is essential for the appropriate dimers and trimers. In this work we calculated total energies of silicon with substitutional or ineterstitial impurity elements and derived formation energies for the substitutional and interstitial impurity elements for the atomic number 1 to 83 with the exception of inert gas and lanthanum series elements. We present here the periodic table with the formation energies of the substitutional and interstitial impurity elements for determining the most stable site of the impurity elements in Si lattice. We can use this table as a database for calculating ionization energies of the impurity element.

Abstract: The warm mix regeneration technology has prominent economical efficiency that can not only reduce the secondary aging of new asphalt and old asphalt in RAP materials during the production process, but also improve the use proportion of RAP materials. As for the increase of RAP dosage and the warm mix additive added to influence the plant regenerated asphalt mixture performance, this paper adopts two kinds of warm mix additive for the test and analysis of the warm mix regenerated asphalt mixture performance with 20% and 60% RAP. The results indicate that magnify the proportion of RAP percentage makes contribution to further improve high-temperature performance of the regenerated mixture, but it has adverse effects on water resistant damage performance and low-temperature performance. At the same time, adopting the warm mix additive can significantly reduce the adverse effect, so warm mix regenerated technology has better feasibility.

Abstract: The casting and solidification process of the bimetallic composite pipe were simulated by ProCAST software aiming at the misrun defect in the pipe. The causes of defect were analyzed from the factors of the pouring temperature, pouring time, preheating temperature of mold and the height of sprue. Reasonable improvements were presented based on the simulation results. Industrial tests showed that misrun defect disappeared after the process was improved, which in turn verified the effectiveness and reliability of simulation results.

Abstract: Welding crack analysis was carried out on tee joint crack of boiler platen superheater header (12Cr1MoV) of subcritical power station applying finite element analysis,microanalysis, mechanical properties test, chemical composition analysis, metallography examination and SEM observation etc. Results indicated that the improper structure, the original welding defects, higher welding heat input, excessive welding residual stress and improper heat treatment led to cold crack and reheat crack ,then induced to the leakage failure while operating.the welding crack originated at the original defects, connected with reheat cracks during propagation and led to leakage finally.