Advanced Materials Research Vols. 154-155

Abstract: Machine vision technique is an advanced method for tool wear monitoring. In this article, a holding system has been designed and fabricated to realize the combination of machine tools and machine vision system. On-machine experiments were carried out to test the effect of this method. Experimental results indicate that tool condition monitoring can be successfully accomplished by analyzing texture feature information extracted from the machined surface.

Abstract: The quenching process is a complex process, which involves quenching medium flow field, work piece temperature and stress field. In this paper, the 40Cr steel belt wheel is chosen for the sample of finite element method to simulate the quenching process. The temperature changes with time at any position in the work piece are directly reflected in the actual quenching process. The cooling curves of center and general surface are obtained after simulation. Combined with cooling curve of transformation of under cooled austenite, it is easy to predict whether the technological results meet the performance of organization, and conduct a security assessment of the work piece.

Abstract: The influence of weld heat input on weld joint between B610CF and 16MnR steel using shielded metal arc welding method was investigated by metallographic experiment and mechanical properties experiment. Metallographic experimental results show that in welded metal with the increasing of weld heat input the quantity of bainite is decreased and crystalline grain is larger; but in both B610CF and 16MnR steel heat affected zone, with the increasing of weld heat input there is no distinct difference in microstructure. Mechanical property experimental results show that in weld metal with the increasing of weld heat input the impact toughness decreases, but in both B610CF and 16MnR heat affected zone, there is less difference in impact toughness; and there is no distinct difference in tensile strength and plasticity of weld joint, which is consistent with the metallographic experiment results.

Abstract: In this paper, using experimental method studied to repair surface fatigue damage of the metal material by heat treatment. Analyzed the mechanism to repair surface fatigue damage of the metal material by heat treatment. From the test, it have been found that the Metal materials has temping threshold behavior in repairing it’s fatigue damage by heat treatment. For the same kind of material, there is a threshold characteristics in choosing tempering temperatures when repaired the fatigue damage of metal material surface through changed tempering temperatures. Experimental results shows that the temping temperature threshold to repair metal material fatigue damage is the first tempering temperature after materials was hardened before it was in fatigue damage.

Abstract: the problem of polarity effect in EDM is researched in this paper. In order to find out the deterioration of the anode and the cathode, the experiment with single pulse is taken in kerosene oil. We find the deterioration of the anode is larger than that of the cathode even in the condition of large pulse width. But this result is contradictory with that gotten in electric discharge machining with continue pulses. Through analyzing the movement of the electron and positive ion in plasma canal, we explain the phenomenon above rationally.

Abstract: In order to reduce the environmental pollution from chromate used in plating factories, one new kind of non-chromium passivation solution containing silicate, hydrogen peroxide and fluoride ion, etc. has been explored to form blue-white conversion film on alkaline electrodeposited zinc coatings. The conversion films on zinc coatings with both glossy blue-white surface and high anti-corrosion performance have been obtained by optimizing the experimental conditions. The results show that silicate-based passivation technique is able to be widely applied to solve the problem of pollution caused by waste from plating industry in the future.

Abstract: Calcite is a common scale in water cooling systems treated and controlled with Organic phosphonates. The effect of three phosphonic acids (ethylene diamine tetra(methylene phosphonic acd), EDTMP; hexamethylene diamine tetra(methylene phosphonic acd), HDTMP; and diethylene triamine penta(methylene phosphonic acd), DTPMP) on the growth of the calcite has been investigated by pH curve method(pHCM). Experimental data obtains by pH value measurement of Ca(HCO3)2 supersaturated solution before and after precipitation. Besides, molecular dynamic simulations of the interaction of the phosphonic acids with the calcite(104) indicate the inhibitor effectiveness: EDTMP< DTPMP< HDTMP according to the difference in the carbon chain between nitrogen atoms. This is in agreement with the pHCM measurements.

Abstract: In order to theoretically simulate the welding process of complex structure with large quantities of welding spots, a simplified method for analyzing a single spot welding should be developed firstly. In this paper, a 2D axisymmetric model of thermoelectric Finite Element Method (FEM) is developed to analyze the transient thermal behavior of Resistance Spot Welding (RSW) process using ANSYS. The determination of the contact resistance at the faying surface is moderately simplified to reduce the calculating time, while the temperature dependent material properties, phase change and convectional boundary conditions are taken into account for the improvement of the calculated accuracy. The thermal history of the whole process and temperature distributions for any position in the weldment is obtained through the analysis. The model can also predict the weld nugget size and the width of the Heat Affected Zone (HAZ).

Abstract: Glass/yttrium silicates/SiC multi-layer coating for carbon/carbon (C/C) composite was prepared and the flexural strength and weight changes of the coated samples after oxidation in air and combustion atmosphere at 1500oC were investigated. Results show that when oxidation in air and combustion atmosphere, the C/C composites lost weight by a linear and a parabolic law respectively. The weight loss reaches its maximum value at about 800oC in air but the strength of the specimen arrives at the lowest value at about 850oC. There are three oxidation zones along the specimens. A non-oxidation zone is below 400oC. Close to it is the cracking-oxidation zone (400-1100oC). At the temperature range from 1100oC to 1500oC is the coating-oxidation zone. Fracture of the coated sample at the temperature spot of 850oC is observed after oxidation in combustion atmosphere at 1500oC for 70 hours, which are considered to be responsible for the cracking and decreasing in strength during the test in combustion atmosphere.

Abstract: Many important time-domain characteristic parameters are extracted through the short-time analysis of arc sound signal in MIG butt welding with spray transfer, which can be used for the diagnosis on the weld penetration status. And the short-time autocorrelation function and short-time average amplitude difference function are adopted to pitch estimation. The analysis results show that the penetration status can be accurately recognized via the short-time energy, average magnitude, average zero-crossing and zero-to-energy and so on. Meanwhile, the pitch estimation of arc sound signal in experiments is at 220 points, that is 5 ms or 200 Hz in cycle. The methods and results provide a foundation for the diagnosis on penetration based on analysis of arc sound signal and have great theoretical meaning and practical value.