Papers by Author: Xu Ma

Abstract: In this paper the fractures appeared in the surface of nanoparticle silicon anode for lithium-ion batteries was explored. The changes of nanoparticle silicon anode before and after cycling were charactered using SEM, XRD,Cyclic voltammograms (CV) and electrochemical impedance spectroscopy (EIS). The result indicates that the electrode cracking occured in the cycling process , the CV, EIS and discharge specific capacity curves proved the fractures could lead to the degradation of the electrochemical performance.

Abstract: In this paper, the defect sheet was captured coincidentally. According to the defective product’s characteristics, we suspected to be caused by the vertical vibration of the roll. When the rolling speed reached a certain value, the vibration of the fourth stand can be feel. The experiment of the vibration data collection was taken to compare the vibration parameters of rolling operating side with those of drive side by wavelet analysis. The result states that the abnormal vibration signal features can be extracted in a special frequency segment of wavelet decomposition, and the vibration frequency to the roll is confirmed which appeared product defects.

Abstract: According to the chatter phenomenon of 3^rd stand of a steelworks six-roller tandem cold mill (TCM), vertical vibration of tandem cold mill was simplified to eight degrees of asymmetric freedom mass-spring system. Virtual prototype model on vertical vibration of tandem cold mill was established and natural frequencies and main vibration mode of mill were solved by using automatic dynamic analysis of mechanical systems in software ADAMS. The modal coordinates of main vibration mode of the mill were referred firstly and obtained; the maximal mode of vibration system was found and finally discovered the fifth-octave-mode chatter was the probable vibration of the mill.

Abstract: The technology monitoring the operating state of the architecture construction is always hot topics in civil engineering. In this paper, attempts using the NiTiSMA film/ferroelectric ceramics PZT composite materials with the function of force - electricity conversion are introduced to the design of structural safety monitoring system. The sensing materials based on the function of force - electricity conversion, directly perceive the stress changes of architectural structure under the vibration loads, monitoring the state changes of internal cracks in the architectural structure. The results show that the safety monitoring system of architectural beam structure,on the sense of NiTiSMA film / ferroelectric ceramics PZT composite materials, possesses reaction speed in milliseconds, response frequency at 0-1000 Hz. It is suitable for monitoring the damage status of cracks in the architecture construction.

Abstract: According to the typical large-diameter thick-walled steel T/P91 (10Cr9Mo1VNb), during the hot working, there are dynamic recrystallization and grain growth. The influence of the samples at different hot treatment on the grain size and grain growth rate were obtained by the statistics of the grain size, The grain growth index under various heat treatment were compared, the mathematical model of the austenite grain growth law of P91 alloy steel was established.

Abstract: The subject of study is the vertical extrusion of P91 large diameter thick-walled seamless steel tube, simulate the variation of microstructure during the abbreviated ratio test. Compare the simulation results and the results of Steel pipe specimens metallographic which were in different extrusion ratio, research the influence of extrusion ratio on microstructure and properties from micro-organizational level, and verify the accuracy of the microstructure evolution of the mathematical model.

Abstract: In this work, On the basis of software ANSYS/LS-DYNA, the strip cold rolling simulation model was established. The process from biting to rolling steady were simulated and investigated for 6-high UCM (6-high middle rolls shift type HC-mill with middle roll bender) cold mill, including the stress, stain state, and velocity field of the workpiece and rolls. The result states that the stability of Biting Process of 6-high cold mill is preferable and the impact of biting process on the roll is acceptable. The simulation regularity corresponds well with the measurements.

Abstract: In this study TIG welding of Tailor welded Galvanized Sheets and their formability of stretch forming have been carried out. It has been found that the microstructure of weld region is ferrites and pearlites, and the microstructure of heat-affected zone (HAZ) is blocky pearlites and ferrites. Stretch tests suggested that when the weld line parallels the tensile axis, σs , σb and the σs/σb is higher than that of the weld line perpendicular to the tensile axis. When the weld line parallels the tensile axis, the elongation of the specimen and n are lower than that of the specimen with the weld line perpendicular to the tensile axis. When the weld line perpendicular to the tensile axis, the fracture surface is basically the same as that of the base metal, when the weld line parallels the tensile axis, the fracture surface is dimples and cleavages.

Abstract: Eccentric extrusion method is used in this paper，through this method achieved bending aluminum-alloy tube extrusion forming process. Used finite element method，achieved three-dimensional numerical simulation of bending aluminum-alloy tube in eccentric extrusion by DEFORM-3D finite element commercial software，analyzed velocity field distribution，material flow，squeezing pressure，stress and strain field distribution of the process；Introduce the mechanism of one step direct extrusion forming tube bending process，it will be of great guiding significance the actual die design.

Abstract: The development of new products of seamless tubes require the development of corresponding grooves in order to manufacture tubes with high precision, high efficiency at low cost. In this work, a finite element model and dynamic simulation of continuous rolling pass for seamless tubes process has been implemented under the ANSYS/LS-DYNA environment to verify the validity of the pass design. The result show the deformation characteristic of cross-section, the variation regularity of rolling force, strain and stress conform to the reality. The work is effective for developing new grooves and products for seamless tube continuous rolling.