Advanced Materials Research Vols. 989-994

Abstract: To provide the necessary design parameters for the actual motor control system, The paper introduces the modeling course of voltage space vector pulse wide modulation (SVPWM) arithmetic and AC motor under MATLAB/SIMULINK environment, discuss founding dynamic model of frequency-variable speed-adjustable system based on vector control, according to the principle of SVPWM. The paper presents the new detailed method of realizing simulation, key problems and results of the simulation were analyzed in detail. The experimental simulation results show that this system has smaller fluctuations of voltage and torque, quicker response speed, and all of the indicators accord with the performance of the actual motor. the simulation arithmetic have value to realize controlling motor with digital signals processing.

Abstract: Cryogenic treatment as an effective non-destructive modification of material, has been widely applied. Equipments and technologies of cryogenic treatment were described, the current research status of cryogenic treatment technology on cemented carbide was reviewed, the action mechanism of cemented carbide cryogenic treatment was analyzed. Finally, in this paper some views and outlooks of cryogenic treatment technology in industrial applications were put forward.

Abstract: Increasing attention has been paid on fatigue performance evaluation in the recent years. More efficient fatigue testing methods are imperatively needed to accomplish the test requirement. The modified staircase theory is introduced in this paper. Traditional staircase method and modified staircase method are respectively used to evaluate the fatigue performance of pressure vessel steel Q345R. Results show the fatigue limits are 194MPa and 193MPa respectively, which indicates the modified staircase method can enhance the testing efficiency about 50% and keep the test veracity.

Abstract: The residual stress on X groove welding plate of high performance bridge steel 4MnNbq is analyzed. The X-ray diffraction method, hole drilling method and indentation method are respectively used to test the residual stress on welding line, heat-affected zone and base metal. The longitudinal and transversal residual stress are analyzed and compared. The results show that the stress along welding line direction is far larger than the transversal one and the stress on base metal are comparatively smaller than the welding line. The testing results of three methods match well, while the results of X-ray method and hole drilling method are much closer, the relative error of indentation method is comparatively larger.

Abstract: The overheat phenomenon often appears in the fatigue test of some high strength materials. It leads the deconcentration of test data and low efficiency of experiment process, or even failure of the whole test. The frequency adjusting method (FAM) and sample shape design technology are developed to solve this problem. Experiment result shows that the FAM can moderately ameliorate the overheat phenomenon. The resistivity of overheat phenomenon of the funnel type sample is far stronger than the straight bar type one.

Abstract: To study the mechanism of metal magnetic memory (MMM) testing technology, the stress-magnetization effect on 20 steel specimens with different notch angles under exercise of the geomagnetic field and tensile load is simulated by using the finite element analysis (FEA) software ANSYS. With the stimulation, the stress and magnetic flux leakage distribution of the specimens is given. The results showed that internal stress distribution of different notch specimens under external tensile effects is different; The curves of relationship between damage degree of stress concentration and the distribution of magnetic flux leakage is also related to the defect shape and structure; Magnetization decreases with increases of stress at first and then increases with continuing increase of stress, which is called stress magnetization reversal. It provides an important reference for the quantitative research of metal magnetic memory technology.

Abstract: This paper firstly studied the structure of front longitudinal, then reviewing comprehensive literature draw the similarity of collision of the thin-walled tube and front longitudinal,finally ensure the study of collision of the thin-walled tube. And establishing three kinds of thin-walled welded rectangular beam finite element model of spot welding, seam welding and laser welding, arrive a more superior technology through researching and analyzing the model.

Abstract: This paper studied the borehole stability in Liulin bituminous core reservoirs during under-balanced drilling. The equivalent depth method was applied to study the formation pore pressure. The floor drain test method was applied to study the ground stress. Core strength experiments combined with logging data were used in the establishment of core strength predicting model. Mechanics analysis model was founded to study the borehole stability in the core reservoir. According to the studying and analyzing results, the under-balance drilling in Liulin coal reservoirs enjoys good borehole stability.

Abstract: This paper expounds the basic principles of composite element method (CEM).In order to model the discontinuity of the displacement, the asymptotic crack tip displacement fields are added to the CEM approximation for the local enrichment by using the framework of partition of unity. Thus, the crack tip can be inserted into anywhere within the element. The crack-tip displacement mode is given, and some formulas are derived and established in a CEM program. The evaluation of stress intensity is discussed. Numerical simulations illustrate that the proposed algorithm has similar accuracy compared to the FEM, and it has advantage of convenient of pre-process.

Abstract: This paper studies the prediction of power plant desulfurization efficiency, based on support vector machine through the meshing method for parameter optimization, establish a prediction model, with the running of the actual data to predict the results: mean square error (MSE) is 0.00259324, the correlation coefficient (R) is 0.979927%, the largest error is less than 1.5%, the results show that the established forecast model based on support vector machine (SVM) with high accuracy to predict the desulfurization efficiency, and can satisfy the engineering need of flue gas desulfurization efficiency prediction.