The paper presents the development of an analytical model and Computational Fluid Dynamics (CFD) model of abrasive water slurry jet machining (AWSJM), along with the experimental investigation of the ...micro-channel formation. The proposed work presents an improvised approach of AWSJM by equipping the conventional abrasive water jet (AWJ) machine with a setup for injecting polymer (Gelatin) solution into the AWJ nozzle, which leads to efficient energy transfer, improved cutting efficiency, and increased material removal rate. The CFD model is developed to simulate jet dynamic characteristics. The modeling of abrasive water jet machining (AWJM) and AWSJM process indicates that the calculated material removal rate is proportional to the power of the water jet. It is further proven from the analytical calculations that during the process of material removal, there is energy loss in both the AWJM and AWSJM. The results from the analytical model are validated through experiments performed on an AWJ machine. The micro-channels were fabricated to compare the depth of cut in the present research work. The analytical model developed to calculate the total depth of jet penetration correlates quite well with the experimental data. It is also observed that the maximum error predicted by the analytical expression and the simulation model for velocity and energy are within 10%.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Reaction-bonded silicon carbide (RB-SiC) is regarded as difficult-to-machine ceramic materials with extremely high strength and hardness. The work focuses on the grinding performance evaluation of ...RB-SiC ground by the dressing diamond grinding wheel with AWJ. Orthogonal experiments studied the influence of processing parameters on grinding force and 3D surface roughness, with the response surface method identifying optimal parameters. Explanation of the ground surface topography and 3D surface roughness in a comprehensive manner shows that an erosion of the bonding material by micro-cutting but diamond grains are being pulled out rather than cut. Results reflect a correlation between surface topography and diamond wheel dressing. The results are of great significance for future formulating an appropriate grinding process to machine RB-SiC ceramics.
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•An efficient RB-SiC machining-strengthening technique integrates abrasive water jet dressing and grinding.•The amplitude, spatial, and hybrid parameters of 3D surface topography were analyzed.•The bonding material is eroded through micro-cutting while the diamond grains are being pulled out.•The IAWJD technique enhanced the grindability and reduced the dressing time.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•·Acoustic emission signals characteristics of AWJ impacting concrete is studied.•·Correlation between AE signals and development of erosion hole is studied.•·The damage of concrete is defined based ...on the ultrasonic velocity is established.•·Damage distribution of concrete impacted by AWJ.
The breaking process and damage distribution characteristics of concrete are the theoretical basis for improving the quality and safety of concrete impacted by abrasive water jet (AWJ) technology. Therefore, the process of AWJ impacting concrete is monitored online based on acoustic emission (AE) technology in this paper. The results show that the AE signals of AWJ impacting concrete have two peaks in frequency domain, the low frequency signals are generated by AWJ and the high frequency signals are generated by concrete breaking. The autoregressive (AR) model is used to estimate the power spectrum of AE signals. The variations of AWJ signals and concrete crushing signals in the impact process are analyzed based on the power of AE signal defined by the area under the power spectral density (PSD) curve. Through monitoring the development process of erosion hole inside the transparent materials impacted by AWJ, it is verified that the power of the concrete crushing signals after the formation of the erosion hole can reflect the penetration rate well. In addition, the damage characteristics of concrete specimens impacted by AWJ are studied in this paper by measuring the transverse ultrasonic velocity of the specimens before and after impact.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The influence of conventional drilling (CD) and abrasive water jet (AWJ) machining on the mechanical behavior of hybrid carbon/flax composites was investigated. The specimens were manufactured using ...woven carbon fiber (C) and unidirectional flax fiber (F) in three configurations: unidirectional 0-90C2/0F6S, cross-ply 0-90C2/(0/90)F6S, and angle-ply 0-90C2/(±45)F6S laminates. The examination of the hole surface revealed severe damage in the form of peel-up, push-out, and secondary delamination of AWJ machined holes, and only push-out delamination at the exit side of the CD drilled hole. A delamination factor was developed to quantify the delamination at the hole surface. The specimens were subjected to quasi-static load-unload tensile tests to assess their damage response and surface fracture. Unidirectional and angle-ply specimens drilled with AWJ accumulated a higher damage compared to CD specimens. This correlates with the delamination factor, indicating that the delamination at the entry and exit of the hole and secondary delamination greatly affect the damage evolution of the laminates.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The goal is to study the influence of abrasive water jet (AWJ) machining parameters (jet pressure, traverse speed and scan step) on the cutting depth of 3D woven Carbon Fibres Reinforced Polymer ...(CFRP) composite. The original material linked to this non-conventional milling process has not been treated yet. The depths of cut were measured and characterized as a function of the machining parameters. Finally, two prediction models for the cutting depth are proposed and validated experimentally.
An increase in cutting depth with the pressure and a decrease as the traverse speed and/or the scan step increase were observed. The first prediction model, based on the pocket depth measurements, has a mean error of 5%. However, the error increases (up to 23%) when the pocket becomes shallow (lesser than 1 mm). The second prediction model, based on the algebraic sum of elementary passes modelled with Gaussian bells, shows at first a mean error of 12%. A correction was performed depending on the erosion regime piloted by the depth of the elementary trench constitutive of the pocket. This enhancement, performed thanks to the primary jet diameters measurements with high speed camera, has improved the second model with a mean error of 5% (error <16%).
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Various kinds of optical structured surface have been widely used in different fields, such as imaging and illumination. However, the machining process of the optical structured surface usually ...leaves tool marks, burs, debris and defects on the structured surface. Currently, it is still a challenging problem to remove these kinds of defects and further improve the surface quality effectively, to obtain better functional performance. In this paper, maskless fluid jet polishing (MFJP) is innovatively presented which is an attempt to solve this problem. In MFJP, low pressure micro abrasive water jet slurry is impinged on the structured surface to implement tiny material removal without using a mask. Experimental investigations on the polishing of sinusoidal structured surface and V-groove structured surface were performed to realize the technical feasibility of MFJP on structured surface, based on the analysis of surface roughness, form maintainability, and surface smoothness. A computational fluid dynamics (CFD) model was also developed to simulate the MFJP process on V-groove surface to demonstrate the fluid flow movement and material removal characteristics. In addition, the effect of the key polishing parameters was also studied and discussed. The results indicate that MFJP can significantly improve the surface quality of optical structured surface, while possessing high form maintainability under certain conditions. It may become a competitive method for the precision polishing of optical structured surfaces. And this study also sheds some light on the application of MFJP for the polishing of other kinds of surfaces with small or micrometer scale cavities or channels, such as microfluidic chips, etc.
∙A maskless fluid jet polishing (MFJP) method is innovatively proposed for the polishing of optical structured surface.∙Polishing performance of MFJP on sinusoidal structured surface and V-groove structured surface are demonstrated to prove the feasibility of MFJP on optical structured surface.∙A computational fluid dynamics (CFD) model is developed to simulate the MFJP process to investigate the fluid flow field and material removal characteristics.∙Effect of fluid pressure, impinging angle and stand-off distance are analyzed and discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper presents an experimental investigation to ascertain the parametric impact of abrasive water jet machining on the surface quality of Inconel 718 material. Experiments were designed ...according to response surface methodology-box Behnken design by maintaining three levels of four process parameters-abrasive flow rate, water pressure, stand-off distance and traverse speed. The surface irregularity is measured during machining. The design expert software was used to establish an optimized mathematical model of process parameters for achieving the required surface roughness. Desirability function has also been used to optimize the process parameters. The confirmation experiments validate the reliability and capability of the developed model. Further, the surface characteristics were analyzed through scanning electron microscope images and energy-dispersive X-ray spectroscopy.
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BFBNIB, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
P618.11; 我国煤层气资源丰富,但是"单井产量低"长期难以改变.提出了煤层气水平井水力喷射分段造穴的新思路,旨在大范围释放储层应力、提高渗透率,从而提高单井产量.首先介绍了水平井水力喷射分段造穴的优势:灵活调控洞穴形状和尺寸、定点喷射、精准分段、多簇卸压、构建体积缝网、符合煤炭原位流态化开采的科学构想.然后,采用有限元-离散元耦合方法(Finite-Discrete Element ...Method)建立了水平井造穴诱导煤层应力演化流-固耦合模型,计算了多段洞穴形成的应力释放区域,描述了穴周、穴间应力干扰区诱导形成的裂缝分布特征,阐释了水平井分段造穴应力释放开采煤层气的原理.其次,开展了淹没条件下磨料直射流和旋转磨料射流喷射煤岩的室内实验,研究了磨料射流喷射煤岩的成孔形态和破坏模式及天然裂隙对破坏作用的影响,发现磨料射流冲击下,层裂是煤岩重要的破裂机制.接着,介绍了裸眼井、筛管井、套管井、顶底板间接改造井等不同水平井完井方式下水力喷射分段造穴的井下核心工具、工艺流程和煤粉返排方式.最后,探讨了该技术的地质储层适应性和应用前景,有望在构造煤、深部煤、煤系薄互层及压裂造缝效果欠佳或无法实现分支井眼重入的松软煤层等推广应用.
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