Precision comparison of analytical and statistical-regression models for AWJ cutting

The article is focused at the comparison of results calculated using analytical model for determination of abrasive water jet cutting and equations prepared via application of the statistical-regression approach. The statistical-regression model (SRM) is based on measurement of a set of column holes cut in a plan-parallel brass plate according to Box-Behnken design. The material and respective range of factors were selected so that they cover the largest possible scale of varying kerf shapes; brass 2.0402 (CuZn40Pb2), water pressure from 280 to 380 MPa, abrasive mass flow rate from 150 to 450 g/min and variable traverse speed from 25 to 75 mm/min. The main results arising from the experiments were the ideal diameters of the holes’ sections in several selected depths of material and the cylindricity, i.e. the difference of the real shape of the “column” hole from the ideal one represented by a column with ideal diameter. The statistical-regression equations for calculation of the selected parameters were set-up. The comparison of the analytical model and the one created via statistical-regression was performed for bottom diameters of the produced holes. The reliability of the statistical-regression model is high within the tested scope of factors. However, its precision can be significantly reduced beyond the selected range of factors or by changes that cannot be involved in the regression (change of material wear character, etc.). Statistical processing of the measured data yields interesting relations between certain factors (abrasive mass flow rate, pressure) and respective results (diameters of holes, cylindricity). Therefore, the respective statistical-regression equations are also presented graphically. The comparison proved that the analytical model also has a very high accuracy and, moreover, its application is not limited by the selected ranges of factors.     

Monitoring of abrasive water jet (AWJ) cutting using sound detection

Our main objective in the present work is to develop a methodology and create a system for the abrasive water jet (AWJ) machining process control. In the case of AWJ cutting, besides the cutting head traverse rate, the distance between the mixing tube and the workpiece, designated as the stand-off distance, has a predominant influence on the workpiece quality. The control of the traverse rate is performed by the machine controller. The stand off-distance control during the machining represents a problem because no effective on-line in real-time stand-off distance detection system has been developed yet. The detection of the stand-off distance during cutting enables better AWJ machining process control. order to monitor the stand-off distance, we measure the emitted sound generated during the AWJ straight cut operation and analyse its characteristic attributes. In order to verify the proposed stand-off distance monitoring methods, a set of experiments was carried out. The signal analysis was performed in both time and frequency domain. The obtained results show an evident influence of the stand-off distance on sound emission. Thus, efficient control of the AWJ cutting process through sound detection appears to be viable.     

Investigation on the effect of cavitation in ultrasonic-assisted AWJ

In order to provide some insight into the complex fluid behavior involved in ultrasonic vibration-assisted abrasive waterjet machining, a three-dimensional     

磨料水射流切割碳纤维复合材料的表面粗糙度试验

采用超高压磨料水射流技术对碳纤维复合材料进行切割试验,借助μscan激光共聚焦显微镜重构样品切口的三维表面,测得样品切口表面粗糙度;研究了扫描分辨率对表面粗糙度测量的影响,以及切割速度、样品厚度对样品切口表面粗糙度的影响规律。试验结果表明：扫描分辨率对表面粗糙度的测量无明显的影响;当切割深度较小（0~0.6 mm）时,即在切口入口处,表面粗糙度随切割深度的增大而减小,当切割深度较大（大于0.6 mm）时,表面粗糙度随切割深度的增大而增大;当样品厚度一定时,随着切割速度的增大,切口最大表面粗糙度在整体趋势上是增大的,而样品厚度的大小对表面粗糙度的影响并无明显的规律。     

后混合水射流供料系统的改进设计

供料系统是后混合水射流设备中不可或缺的组成部分,极大地影响着后混合技术在实践中的作业效率和精度。本文通过归纳传统后混合水射流设备所采用的几种供料方式和供料装置特点,分析其存在的不足。并结合计算机模拟仿真手段,研究了气流在输送管道内的运动规律,提出了两种在现有装置条件下改进的供料系统设计方案,具有极好的运用前景。     

Analytical prediction of cutting forces in orthogonal cutting using unequal division shear-zone model

This paper presents an analytical method based on the unequal division shear-zone model to study the machining predictive theory. The proposed model only requires workpiece material properties and cutting conditions to predict the cutting forces during the orthogonal cutting process. In the shear zone, the material constitutive relationship is described by Johnson?CCook model, and the material characteristics such as strain rate sensitivity, strain hardening, and thermal softening are considered. The chip formation is supposed to occur mainly by shearing within the primary shear zone. The governing equations of chip flow through the primary shear zone are established by introducing a piecewise power law distribution assumption of the shear strain rate. The cutting forces are calculated for different machining conditions and flow stress data. Prediction results were compared with the orthogonal cutting test data from the available literature and found in reasonable agreement. In addition, an analysis of the deviation from experimental data for the proposed model is performed, the effects of cutting parameters and tool geometry were investigated.     

磨料水射流切割石材加工表面质量的试验研究

文中对高压磨料水射流切割石材的加工表面质量进行了试验研究,分析了水射流压力、靶距、切割速度和磨料流量对加工表面质量的影响。结果表明:当水射流压力增大时,光滑区切割深度增大,而表面粗糙度先减小后增大;当靶距增加时,表面粗糙度增大,而切割光滑区切割深度减小;当切割速度增加时,表面粗糙度增大,而光滑区切割深度迅速减小;当磨料流量增加时,表面粗糙度减小,而切割表面的光滑区深度先增大后减小。     

纳米切削加工模型的研究

从分析建立传统切削加工模型的理论基础和分析方法入手,指出该模型应用于纳米切削加工的不合理性,应用分子动力学仿真建立了纳米切削的加工模型.研究表明,在纳米切削过程中,当切削深度小于最小切削深度时,工件材料只发生了弹塑性变形,没有形成切屑.     

Microstructural model of ceramic cutting plate

A microstructural model of a ceramic cutting plate is developed. It permits the derivation of a calculation scheme for a mathematical model that includes the density, the elastic modulus, the thermal conductivity, the specific heat, the linear expansion coefficient, and Poisson’s ratio.     

An approximate model of abrasive cutting

An approximate three-dimensional model of abrasive cutting is developed, modelling the abrasive grit by an irregular pyramid. The predictions of the model are compared with the results of some single-point scratch tests. Then it is used to predict how the shape of abrasive grits and the stiffness of their bond will affect the surface finish and specific energy in real abrasive processes.     

A model of the cutting mechanism in grinding

In order to achieve optimum working results during grinding, information regarding both the kinematic relations and the structure of the multiple cutting-edge tool is necessary. In addition, the physical and metallurgical properties of the workpiece material and the specific influence of the interfacial frictional effects must be taken into account.This paper presents a contribution to the understanding of the cutting mechanisms in grinding. An analysis of the grinding mechanism is made on the basis of the cutting-edge geometry and the kinetics involved. One physical model has been developed to explain all the phenomena from friction to ploughing and cutting under plane strain conditions.Starting from the velocity relation at an averaged penetrating cutting edge and characterizing frictional conditions at the interface between the cutting edge and the workpiece material, it is possible to calculate a slip-line field which satisfies all the existing boundary conditions. The flow pattern of the material can be drawn taking the corresponding hodograph into account. This results in a distortion of the square grid characterizing the material on passing through the region of plastic deformation. Agreement with cross sections of actual chip formation zones during grinding is observed. The significance of this analysis lies in the fact that it establishes a relation between chip formation and the resultant surface integrity.     

采煤机截割高度测量模型与测量误差分析

采煤机截割高度的测量及其误差分析是实现综采工作面自动化的一项重要研究内容.本文针对机身姿态传感器和摇臂摆角传感器测量方案、机身姿态传感器和调高油缸位移传感器测量方案,分别建立了采煤机截割高度测量模型.利用函数误差公式,推导了测量误差模型.以MG1000/2660-WD型采煤机为例,分析了截割高度测量误差分别随俯仰角、摇...     

高速干式飞刀的切削温度模型

根据传热学和金属切削原理等,建立高速干式飞刀的切削温度模型,推导出多因素切削温度的计算公式,该模型的建立为进一步分析高速干式滚齿切削温度及切削机理奠定了基础。     

A study on the compensation of secondary distortion effect in the cutting process of a welded structure

Journal of Mechanical Science and Technology - Lug structures are commonly used in heavy industries. Welded lugs with holes could be hooked onto and transported by a crane. After setting up, the...     

The axis of distortion

The shortening effect observed when structural members are subject to torsion is examined. Results obtained previously by Weber, Cullimore, Ashwell and Gregory are clarified and shown to be equivalent while all strains remain elastic. The co-ordinates of a fully plastic distortion axis are found for a range of sections. The significance of the co-ordinates of the distortion axis for a section twisted while all strains remain elastic and subject to axial loads, bending moments and end torques is discussed. It is shown that when the co-ordinates of the distortion axis are used as reference axes, the torsional stiffness of the member is easily found.     

Study on product configuration based on product model

A product configuration method based on a product model is introduced. Super-variable of component and independent principle are introduced and then a product model based on them is constructed. According to the source and function of the configuration rule, an organizational method of rules with some categories and levels is introduced and the steps of construction of the rule base are also put forward. Based on the product model and rule base, two configuration processes are introduced. Finally, a computer configuration example is given.     

基于产品模型的产品配置研究

对产品配置的相关对象进行了分析,提出了一种基于产品模型的产品配置方法。在构件超变量和不相关原则的基础上构造了产品模型;根据配置规则的来源及其在实例化中的用途,给出规则的分类分级组织方式及规则库的构建方法;给出了两种配置流程及"松"紧"结合的配置策略。最后给出了一个计算机配置的实例。