Xu Yue Wang

Modeling of Laser Dressing for Metal-Bond Diamond Grinding Wheel

Laser processing of super-abrasive grinding wheel is paying a role in a truing/dressing technique to complement mechanical methods recently. However, normal dressing/truing is difficult owing to the toughness of metal-bond materials and high hardness of diamond abrasive. Both geometric and mathematic models were developed to improve laser processing quality and predict various processing parameters, such as focal offset, and incident power, and power density to perform material removal during laser processing a metal-bond diamond grinding wheel. Various trends of the geometrical features of dressing zone in terms of the varying focal offsets were analyzed. Discussions were also given on dressing-zone geometry control. Experimental studies were carried out using different processing parameters to test the effects of laser poweres on dressing quality. Further grinding-force measurement determined the laser dressing parameters with respect to the wheel surface conditions. The normal force FN reduces up to 20%, while tangential force FT decreases to 7% too.The outcomes were shown well agreement with predicted results.

Laser Truing and Dressing of Small Vitrified CBN Grinding Wheel

This paper aims at the development of an alterative technique for truing and dressing a small vitrified CBN grinding wheel used for the internal finishing of small holes measuring several millimeters in diameter. In conventional truing and dressing, a single-tip diamond dresser or a rotary GC cup wheel dresser is employed. This levels off the improvement in the wheel truing accuracy because the stiffness of the grinding wheel shaft with an open-sided structure is low, and the shaft is thus deformed easily due to the truing force. In the present work, a new truing and dressing technique is proposed in which a Nd:YAG laser beam is employed as the dresser. Experiments were carried out with respect to the effects of the laser beam conditions (amplitude, width and frequency of pulse, and focus offset) and the relative motion between the laser beam and CBN wheel. It was found that the run-out of the CBN wheel was decreased significantly, and the wheel surface condition was improved greatly after laser truing and dressing.

Scattering of SH Waves by an Arc-Shaped Crack between a Cylindrical Piezoelectric Inclusion and the Matrix: Near Fields

The scattered far field pattern(SFFP) and scattered cross section(SCS) are obtained based on the work of part I. Different from the near field case, the numerical results indicate that the resonance occurs at relatively high frequency, and on the whole keeps in a wake of decreasing resonance peaks.

Energy Model in Laser Processing of a Cylindrical Grinding Wheel

Laser processing of abrasive grinding wheels is paying a great role in a truing technique to complement mechanical methods. An energy balance model was adopted that took into account the space modes of laser energy absorbed/scattered by the wheel (circular profile). Both geometric and mathematic models were developed to reveal laser processing mechanism and predict various processing parameters, such as incident position, focal offset, and incident power, to perform material removal during laser processing a cylindrical grinding wheel. Moreover, the incident angle for laser processing of small-vitrified CBN grinding wheels was optimized. Further theoretical analysis and experiments determined the focal position of the incident beam with respect to the wheel profile. Experimental studies were carried out using different processing parameters and grinding wheels to test the effects of laser space properties on processing quality. The experimental results were shown to be in reasonable agreement with predicted results.

Energy-Mode Adjustment in Laser Processing a Small Vitrified CBN Grinding Wheel

A study of the energy-mode adjustment and application was presented to investigate the effects of adjustable methods on energy mode. Three methods of energy-mode adjustment were used: by circular profile itself, by an optical scanning expander and deformable mirror. The circular profile naturally modifies energy density with the changes of incident angle. The optical scanning expander was used to turn a Gaussian beam into a uniform beam. Also a novel technique of deformable mirror was designed to obtain a more controllable energy mode for laser selective processing. Moreover, the models describing energy modes were developed to improve laser-processing performance. An experiment was arranged to simulate single-tip diamond truing and produced a result, as shown in the SEM photo, quite similar to a fine thread. The results were discussed to reveal the mechanism of laser processing.

Mathematical Modeling of Electrochemical Deburring

The drilling burr is taken as the research object. A mathematical model of electrochemical deburring (ECD) is established and the effects of main influencing factors, such as inter-electrode gap, applied voltage and deburring time, on burr height have been analyzed. The results show that the deburring time increases with the increase of initial burr height, inter-electrode gap, with the decrease of volume of electrochemical equivalent of the workpiece material, conductivity of electrolyte and applied voltage. The deburring time for various burr heights can be predicted by the mathematical model. The calculated results obtained from the mathematical model are approximately consistent with the experimental results. The results show that initial burr height h0=0.722mm is removed, and the fillet radius R=0.211mm is obtained.

Laser Cutting Quality of the Ceramic Slabs

An experimental analysis is presented which investigates the relationship between cutting parameters and the volume of material removal as well as its cutting quality on a Nd:YAG laser cutting system. The parameters that varied on two testing thickness during cutting include cutting speed, incident laser power and focal position in a continuous through cut. Various trends of the kerf geometrical features in terms of the varying process parameters are analyzed and shown to be reasonable. Discussions are also given on kerf geometry control in situations with cutting parameters. It shows that the effects of varying parameters such as cutting speed, laser power and focal position on cutting kerf width, surface roughness, and striation that have provided a deeper understanding of the laser machining.

A Basic Study on Precision in Electrochemical Abrasive Lapping of Plate

Taking plate as the example, this paper studies the effect of tool’s shape and movement on the electrochemical as well as mechanical lapping characteristics in Electrochemical Abrasive Lapping (ECAL). It is assumed that the removal size of electrochemical action at a random point is in direct proportion to the electrical amperage through this point and the removal size of the lapping action is in direct proportion to the relative frictional distance. Based on the assumption above, electrochemical and mechanical lapping characteristics with different tools shape are studied theoretically. The results show that the diameter of the tool should be larger than the width of the workpiece when a discal tool is used and the inner diameter of the tool should be larger than the width of the workpiece when a ringed tool is used, on the other hand the ratio of the revolving radius of the tool to the diameter of the tool as larger as possible avails to improve the precision and so does the ratio of the angular velocity of the workpiece to the rotating angular velocity of the tool.

Numerical and Experimental Research on the Flexible Forming of Metal Sheet Using Magnetic-Driving Plasma Arc

Flexible forming of metal sheet using plasma arc is a new technique which forms parts by thermal stress without moulds and external force. To improve the surface quality of formed parts, a magnetic-driving plasma arc (MDPA) was applied in monitoring the distribution of heat flux. A mathematical model was developed to study the variations of temperature fields and deformation fields with MDPA and merely with plasma arc, which was validated by the forming experiments. The results indicated that the swing amplitude of MDPA increased linearly when the exciting current Ie < 1.2 A, and the distribution of heat flux with MDPA was more uniform than that merely with plasma arc in the heating zone, which avoided the possible partial melting and ablation of metal sheet. Moreover, the “U-shape” occurred with MDPA, and the material accumulation with MDPA was smaller than that merely with plasma arc on the surface of metal sheet.

Investigation of the Transient Deformation in the Flexible Forming of Laminated Composite Metal Sheets Using Plasma Arc

A three-layer FEM model, based on the characteristics along the thickness direction of laminated composite metal sheets (LCMS), was developed to study the variation rules of transient deformation in the flexible forming of LCMS using plasma arc. Besides, the comparisons of the typical LCMS Q235A/1Cr13 and single layer metal sheet (SLMS) Q235A were performed. It indicates that the displacement of end point of SLMS is 0.076 mm larger than that of LCMS with the same process parameters. Moreover, the differences of X-axis plastic strain, Z-axis plastic strain along the thickness direction of LCMS decide the bending direction, the occurrence of the edge effect of LCMS during linear heating, respectively. Furthermore, Y-axis stresses of LCMS different layers undergo three dramatic changes with the maximum stress difference of 1.420×107 Pa, and the possible failure of interface delamination occurs in the bonding interface of Q235A and transition layer.