Mathematical modelling of abrasive waterjet footprints for arbitrarily moving jets: Part I—single straight paths

It is notoriously well-known that abrasive waterjet milling (AWJM) is difficult to perform controlled-depth owing to variable geometries of the footprints that depends not only on jet energy and the exposure time upon the workpiece, but also on the orientation of the jet relative to the target surface. An attempt is made to develop a model that can be generally applied to different machine system and to predict individual jet footprints that are one of the key steps for controlled-depth AWJM. To address this, the paper breaks new ground in geometrical modelling of AWJM with the benefit of having few variables for predicting the footprints obtained under the following conditions: (i) any time exposures (i.e. V_f, jet feed speeds); (ii) jet orientations (θ) relative to the target surface; (iii) arbitrarily moving straight jet-paths (β). These conditions reflect the real industrial conditions under which the process is run. The geometrical model results in a non-linear partial differential equation, a method to evaluate the material specific erosion rate from the characteristics of a shallow trench obtained experimentally using high jet feed speeds. Under these conditions, the governing equations can be linearised and solved analytically.The model validation for full profile of trenches generated at various tilt angles (θ=70-90°), jet feed rates (V_f=500-1000 mm/min) and jet path directions (β=0-270°) indicates that a high degree of accuracy (mean of the residuals R_M<3% and root-mean-square error of residuals R_RMS<6%) has been achieved. This innovative footprint modelling approach has the key advantage of being independent of the properties of the workpiece material and/or machine setup, since it calibrates the specific etching rate. By considering any orientation of the jet plume vector relative to the target surface, this approach becomes a powerful tool for the development of advanced jet path strategies to enable AWJM of complex geometries.     

磨料水射流的切割机理

用磨料水射流对材料进行切割实质上是一个冲蚀作用过程。本文根据磨料颗粒对脆性材料的切割过程,研究了磨料水射流的切割机理,即对物体在磨料水射流冲蚀作用下表面所受的压力及分布、冲蚀破坏的方式及特点进行了探讨,并分析了磨料颗粒的密度、速度及尺寸对磨料水射流冲蚀能效的影响。     

IMPROVING FATIGUE STRENGTH OF METALS USING ABRASIVE WATERJET PEENING

Abrasive waterjet (AWJ) peening has been proposed as a viable method of surface treatment for metal orthopedic devices. In this study the influence of AWJ peening on the compressive residual stress, surface texture and fatigue strength of a stainless steel (AISI 304) and titanium (Ti6Al4V) alloy were studied. A design of experiments (DOE) and an analysis of variance (ANOVA) were used to identify the primary parameters contributing to the surface texture and magnitude of surface residual stress. The influence of AWJ peening on the fatigue strength of the metals was evaluated under fully reversed cyclic loading. It was found that AWJ peening results in compressive residual stress and is primarily influenced by the abrasive size and treatment pressure. The residual stress of the AISI 304 ranged from 165 to over 460 MPa. Using the optimum treatment parameters for maximizing the residual stress, the endurance strength of Ti6Al4V was increased by 25% to 845 MPa. According to results of this study AWJ peening is a viable method of surface treatment for applications that require an increase in surface roughness and maintenance or increase in fatigue strength, qualities that most often are not available from a single process.     

IMPROVING FATIGUE STRENGTH OF METALS USING ABRASIVE WATERJET PEENING

Abrasive waterjet (AWJ) peening has been proposed as a viable method of surface treatment for metal orthopedic devices. In this study the influence of AWJ peening on the compressive residual stress, surface texture and fatigue strength of a stainless steel (AISI 304) and titanium (Ti6Al4V) alloy were studied. A design of experiments (DOE) and an analysis of variance (ANOVA) were used to identify the primary parameters contributing to the surface texture and magnitude of surface residual stress. The influence of AWJ peening on the fatigue strength of the metals was evaluated under fully reversed cyclic loading. It was found that AWJ peening results in compressive residual stress and is primarily influenced by the abrasive size and treatment pressure. The residual stress of the AISI 304 ranged from 165 to over 460 MPa. Using the optimum treatment parameters for maximizing the residual stress, the endurance strength of Ti6Al4V was increased by 25% to 845 MPa. According to results of this study AWJ peening is a viable method of surface treatment for applications that require an increase in surface roughness and maintenance or increase in fatigue strength, qualities that most often are not available from a single process.     

高压水射流切割系统的研究与设计

阐述新型水射流切割系统的工作原理,混合流体满足的能量方程,计算水射流的动压力,简要介绍水射流切割机的硬件电路设计及软件实现。讨论了局部阴力系数对动压力的影响,并给出算例。     

水射流技术的应用研究

水射流是一项迅速崛起的新技术、新工艺,随着其参数(压力、流量、功率等)与喷射形式的不同,它可应用于许多方面.本文介绍了水射流在喷水推进、水雾灭火和射流切割、粉碎、表面清洗等方面的应用,并详细分析了其优点及应用机理.     

磨料水射流加工工程陶瓷工艺参数对加工质量的影响

研究用高压磨料水射流加工工程陶瓷，通过分析各工艺参数对加工质量的影响，提出了一种优选工艺参数的方法。     

磨料射流加工的主要参数对冲蚀体积的影响

试验研究了前混合磨料射流加工的主要参数（压力、磨料重量比浓度、靶距、横移速度、磨料粒径大小等）对冲蚀体积率的影响。试验结果表明：压力增大，冲蚀体积率增大；在其它参数不变时为获得最大的冲蚀体积率则有一最佳的磨料重量比浓度和横移速度及靶距；磨料粒径大小对冲蚀体积影响不大。     

超高压磨料水射流切割质量的实验研究

对磨料水射流切割断面的形貌特征及其形成机理进行了分析.针对国产AWJ切割系统的特点,实验研究了系统主要参数对几种常用材料切割质量的影响规律.分析了塑性和脆性材料的切割断面特点,为实际的工艺参数选择提供了可靠依据.     

High Performance Cutting with Abrasive Waterjets beyond 400 MPa

Abrasive waterjet (AWJ) cutting has been widely accepted by the industry after the successful introduction of 400 MPa cutting systems. This paper describes the cutting with AWJ beyond the current industrial pressure limit. Firstly, the factors that limit the water pressure are discussed. Secondly, the jet formation is considered by addressing the effects of the geometry of the upstream tube and the orifice. Finally, the AWJ cutting process is described in terms of energy transfer efficiency. There is an optimum abrasive load ratio over which the cutting ability of the jet decreases due to the less efficient power transfer from waterjet to the abrasives.