Analysis of particles size distribution on the agglomeration and shrinkage of alumina-zirconia compacts

The combination of Alumina and Zirconia has emerged as a promising ceramic structure for advance machine tool application. However, the particles of Alumina and Zirconia tend to agglomerate during mixture which affected shrinkage and dimension accuracy of the end product. This study focused on the analysis of the particle size of Alumina-Zirconia compacts and their relationship with the shrinkage and agglomerates. The particles size of single Alumina, Zirconia and ball-milled Alumina-Zirconia with 90-10 wt% ratio were examined by mastersizer. These powders then were compacted and sintered at 1400°C to examine their shrinkage. The results show that Alumina possesses larger particles size of 109.65 μm, which is 10 folds larger than Zirconia at 6.10 μm. When blended by ball mill, the Alumina�Zirconia particles were changed into 9.77 μm, showing that the ball mill to refine powder particles while reducing the risk of agglomeration. After sintering, the Alumina-Zirconia compacts were shrunk to maximum 9.56% when 75-25 wt% of Alumina-Zirconia. The combination of porosity, agglomerate and infiltration of zirconia between alumina grains were responsible for the shrinkage of Alumina-Zirconia compacts

Effect of laser parameters on the surface cleaning of galvanised steel by laser engraving process

Laser cleaning is a method of removing layers of material from a surface by using laser irradiation. The energy from the laser provides a textured pattern on the melting surface, as well as colour changes and variations in surface roughness. This study looks into the effect of laser parameters on the cleaning surface of galvanized steel. In particular, the laser engraving method was used to irradiate the selected area by varying the laser power and irradiation cycle. The results show that the upper layer of galvanized steel can be rapidly removed, altering the surface profile and roughness. Increasing laser power and cycling the resultant colour change from white or bright to dark. In terms of surface roughness, the first irradiation cycle demonstrated increasing surface roughness as laser power was increased. The fourth cycle, on the other hand, showed a decrease in surface roughness as the laser power increased. In terms of surface finish, laser engraving at 16W power is recommended due to its best surface roughness of 1.17 μm. In terms of surface profile, laser engrave is suggested to be applied during the fourth irradiation cycle because the surface pattern demonstrated dark appearances and minimal surface roughness

การศึกษาปัจจัยของการตัดด้วยน้ำแรงดันสูงที่ส่งผลต่อคุณภาพการตัดแผ่นปูพื้นยางพาราInfluence of Abrasive Waterjet Cutting on Efficiency of Cutting Rubber Floor Mats

งานวิจัยนี้มีวัตถุประสงค์เพื่อศึกษาปัจจัยของการตัดด้วยน้ำแรงดันสูงที่ส่งผลต่อคุณภาพการตัดแผ่นปูพื้นยางพารา เพื่อพัฒนาเป็นแผ่นจิกซอว์ยางพารา โดยพิจารณาปัจจัยตัวแปรการตัด ประกอบด้วย อัตราการไหลของผงตัด ระยะห่างระหว่างหัวตัดกับชิ้นงาน แรงดันน้ำ และความเร็วในการตัด ที่ส่งผลต่อคุณภาพการตัดชิ้นงาน คือ ความหยาบผิวของรอยตัด ความกว้างของรอยตัด และมุมเอียงของรอยตัด โดยใช้การออกแบบการทดลองแฟกทอเรียลเต็มรูปที่ 3 ระดับ เพื่อหาเงื่อนไขการตัดที่เหมาะสมต่อคุณภาพชิ้นงาน เมื่อทำการวิเคราะห์ผลการทดลองทางสถิติโดยกำหนดระดับนัยสำคัญที่ 0.05 พบว่า ปัจจัยอัตราการไหลของผงตัด ระยะห่างระหว่างหัวตัดกับชิ้นงาน แรงดันน้ำ และความเร็วในการตัดมีผลต่อคุณภาพการตัด เงื่อนไขการตัดแผ่นจิกซอว์ยางพารา ขนาดความหนา 7 มิลลิเมตร และความแข็ง (Shore A) 50–90 ที่เหมาะสม คือ อัตราการไหลของผงตัด 350 กรัมต่อนาที ระยะห่างระหว่างหัวตัดกับชิ้นงาน 2 มิลลิเมตร แรงดันน้ำ 300 เมกะปาสคาล และความเร็วในการตัด 2,000 มิลลิเมตรต่อนาที เมื่อนำปัจจัยที่เหมาะสมดังกล่าว ไปประยุกต์ใช้ในกระบวนการตัดจริงสามารถตัดชิ้นงานได้จริงโดยใช้เวลาตัดน้อยเพียงประมาณ 3 นาทีต่อชิ้นงานขนาด 10×10 เซนติเมตร คุณภาพรอยตัดความหยาบผิวเฉลี่ยด้านบนและด้านล่างอยู่ที่ 3.15 ไมโครเมตร และ 3.37 ไมโครเมตร ความกว้างเฉลี่ยด้านบนและด้านล่างอยู่ที่ 1.35 มิลลิเมตร และ 1.28 มิลลิเมตร และมุมเอียงรอยตัดเฉลี่ยอยู่ที่ 1.83 องศา ตามลำดับ ซึ่งผลการวิจัยเป็นประโยชน์ต่อผู้ประกอบการที่ต้องการเพิ่มมูลค่าแผ่นปูพื้นยางพาราเป็นแผ่นจิกซอว์ยางพารา โดยกระบวนการตัดหลังการขึ้นรูปThe purpose of this research is to investigate the influence of high-pressure water cutting on efficiency of cutting rubber mats to develop into rubber puzzle mats. The cutting variables, i.e. abrasive mass flow rate, stand-off distance between a nozzle and the workpiece, water pressure and cutting speed were taken into account. The effects of cutting parameters on the subsequent quality, specifically surface roughness, kerf width and kerf bevel angle were explored. The three-level full factorial experimental design was applied to define optimization of cutting parameters (p<0.05) and ideal cutting conditions were observed. From the experiment, it was found that the abrasive mass flow rate factor, stand-off distance between nozzle and workpiece, water pressure and cutting speed have a significant influence on cutting characteristics. Optimal cutting conditions for 7mm thickness, 50–90 Shore A rubber puzzle mats were determined as follows: abrasive mass flow rate of 350 g/min, stand-off distance of 2 mm, jet pressure of 300 MPa and cutting speed of 2,000 mm/min. Practical applications of these optimal parameters for 10×10 cm rubber puzzle mats proved that cutting process could be completed within 3 minutes. This is acceptable for industrial manufacturing. The cut quality characteristics were exposed as 3.15 μm top surface roughness, 3.37 μm bottom surface roughness, 1.35 mm top kerf width, 1.28 mm bottom kerf width and 1.83 degree kerf bevel angle, respectively. The results of this study can prove beneficial to rubber mats manufacturers by increasing the value of rubber mats by post cutting process for creating rubber jigsaw mats

A Study of the abrasive waterjet hole machining processes on woven CFRPs and the jet impact characteristics

A comprehensive literature review on the development of the abrasive waterjet (AWJ) machining technology and the knowledge relating to the AWJ machining processes has been conducted. It is revealed that the AWJ machining has been proven to be an effective tool for processing composite materials due to its distinct advantages. However, the understanding of the AWJ machining performance on polymer matrix composites (PMCs), particularly the woven carbonfibre reinforced polymers (CFRPs) that are gaining increasing industrial applications, remains unclear, while the knowledge of delamination induced by the machining process is even in more dearth. Furthermore, there is little reported study on the jet impact process and phenomenon under the ultrahigh velocity conditions relevant to AWJ machining. AWJ cutting and drilling (or piercing) processes for through holes on woven CFRPs are experimentally investigated to understand the characteristics of machined holes and the influencing parameters. It is shown that small holes whose diameter is slightly greater than the nozzle diameter can be effectively generated by AWJ drilling, while relatively large holes of a desired diameter can be produced by AWJ cutting. The holes machined by both processes exhibit similar geometrical features, where the hole top diameter is greater than the bottom, so that a hole wall inclination angle is formed. Plausible trends of the hole characteristics with respect to the process parameters are discussed. In the cutting process, a higher water pressure or a slower nozzle traverse speed causes a larger hole diameter and a smaller hole wall inclination angle. In the drilling process, the hole diameter increases with an increase in standoff distance or water pressure, while the hole wall inclination angle increases with an increase in standoff distance or a decrease in water pressure. The shock wave impact of the waterjet at the initial jet-workpiece interaction is found to be the major cause for the formation of hole defects, such as delamination and chipping. The drilled holes have more severe defects than the cut holes because the defects caused by the initial jet impact stay with the drilled holes, while the hole cutting process can start at somewhere on the workpiece that eventually becomes a scrap. Nevertheless, the defects can be alleviated or eliminated by selecting the recommended appropriate process parameters. Mathematical models for predicting the relevant machined hole characteristics, namely hole diameter and hole wall inclination angle, have been developed. It has been shown that the predicted results from the models agree well with the experimental data under the corresponding conditions.In order to understand the jet flow and impact characteristics under the ultrahigh velocity conditions relevant to AWJ machining, a computational fluid dynamics (CFD) model has been developed. A CFD model for the AWJ flow characteristics is first developed, experimentally verified, and used to simulate and study the jet and particle flow characteristics typified by velocities. This simulation study shows that the waterjet and particle velocity profiles across the jet evolve from the initial one-seventh power law distribution to a flatter cap distribution with an increase in downstream distance from the nozzle exit. The change rate of the water velocity is higher than that of the particles due to the less density and momentum of the water. However, a smalldifference between the waterjet and particle velocities is found even at the 70 mm downstream location. The AWJ flow model is then extended to allow the study of the AWJ impact characteristics on a solid surface. It is revealed that stagnation is developed at the jet impact site, which has a significant effect on the energy of the waterjet and particles that can be transferred to the target surface. The average particle velocity across the jet is reduced by approximately 33% by the damping effect of the stagnation for the conditions considered in this study. The stagnation also induces the particles to deviate from their moving trajectory, so that the particle impact angle is changed and the jet impact area is enlarged. The formation of stagnation is found to be influenced by the jetting and impact parameters. An increase in standoff distance or nozzle diameter results in an increase in the magnitude of the stagnation zone. An oblique jet impact yields an asymmetric stagnation zone, where the stagnation centre is away from the jet axis. Mathematical models for the relevant particle impact characteristic quantities, namely the particle impact velocity, particle translation in the jet radial direction and particle impact angle, are finally developed based on the understanding gained from the CFD simulation studies. The models are verified by comparing the model predictions with the corresponding numerical data. It is shown that the developed particle impact models can provide adequate predictions for use in future studies of the particle impact micro-mechanics and impacterosion