Tool Failure Analysis in High Speed Milling of Titanium Alloys

In high speed milling of titanium alloys the high rate of tool failure is the main reason for its high manufacturing cost. In this study,fractured tools which were used in a titanium alloys 5-axis milling process have been observed both in the macro scale using a PG-1000 light microscope and in the micro scale using a Scanning Electron Microscope (SEM) respectively. These observations indicate that most of these tool fractures are the result of tool chipping. Further analysis of each chipping event has shown that beachmarks emanate from points on the cutting edge. This visual evidence indicates that the cutting edge is failing in fatigue due to cyclical mechanical and/or thermal stresses. Initial analyses explaining some of the outlying conditions for this phenomenon are discussed. Future analysis regarding determining the underlying causes of the fatigue phenomenon is then outlined.

Benchmarking Approach to Compare Web Applications Static Analysis Tools Detecting OWASP Top Ten Security Vulnerabilities

To detect security vulnerabilities in a web application,the security analyst must choose the best performance Security Analysis Static Tool(SAST)in terms of discovering the greatest number of security vulnerabilities as possible.To compare static analysis tools for web applications,an adapted benchmark to the vulnerability categories included in the known standard Open Web Application Security Project(OWASP)Top Ten project is required.The information of the security effectiveness of a commercial static analysis tool is not usually a publicly accessible research and the state of the art on static security tool analyzers shows that the different design and implementation of those tools has different effectiveness rates in terms of security performance.Given the significant cost of commercial tools,this paper studies the performance of seven static tools using a new methodology proposal and a new benchmark designed for vulnerability categories included in the known standard OWASP Top Ten project.Thus,the practitioners will have more precise information to select the best tool using a benchmark adapted to the last versions of OWASP Top Ten project.The results of this work have been obtaining using widely acceptable metrics to classify them according to three different degree of web application criticality.

Prediction of cutting force in ultra-precision machining of nonferrous metals based on strain energy

The effects of the nonuniform cutting force and elastic recovery of processed materials in ultra-precision machining are too complex to be treated using traditional cutting theories,and it is necessary to take account of factors such as size effects,the undeformed cutting thickness,the tool blunt radius,and the tool rake angle.Therefore,this paper proposes a new theoretical calculation model for accurately predicting the cutting force in ultra-precision machining,taking account of such factors.The model is first used to analyze the material deformation of the workpiece and the cutting force distribution along the cutting edge of a diamond tool.The size of the strain zone in different cutting deformation zones is then determined by using the distribution of strain work per unit volume and considering the characteristics of the stress distribution in these different deformation zones.Finally,the cutting force during ultra-precision machining is predicted precisely by calculating the material strain energy in different zones.A finite element analysis and experimental data on ultra-precision cutting of copper and aluminum are used to verify the predictions of the theoretical model.The results show that the error in the cutting force between the calculation results and predictions of the model is less than 14%.The effects of the rake face stress distribution of the diamond tool,the close contact zone,and material elastic recovery can be fully taken into account by the theoretical model.Thus,the proposed theoretical calculation method can effectively predict the cutting force in ultra-precision machining.

Static Analysis and Code Complexity Metrics as Early Indicators of Software Defects

Software is an important part of automotive product development, and it is commonly known that software quality assurance consumes considerable effort in safety-critical embedded software development. Increasing the effectiveness and efficiency of this effort thus becomes more and more important. Identifying problematic code areas which are most likely to fail and therefore require most of the quality assurance attention is required. This article presents an exploratory study investigating whether the faults detected by static analysis tools combined with code complexity metrics can be used as software quality indicators and to build pre-release fault prediction models. The combination of code complexity metrics with static analysis fault density was used to predict the pre-release fault density with an accuracy of 78.3%. This combination was also used to separate high and low quality components with a classification accuracy of 79%.

Optimal Design of Rotary Tool based on ANSYS Workbench

Rotary tool of garbage crusher is the key component of the whole mechanism, which is of vital importance to tool design and analysis. Based on ANSYS Workbench 3D modeling, we carried on finite element analysis to tool, and used the method of goal driven optimization to optimize the rotary tool. The optimization proves that the optimized maximum equivalent stress is 544.14 MPa, the quality is less, and the optimized rotary tool size is more reasonable. So it provided reasonable and scientific reference frame to the structural design of rotary tool.

园林修剪机器人臂端刀具优化设计与稳态分析

我国园林绿化面积不断扩大,但园林修剪机设备目前处于半人工半自动化状态。为此,提出并设计了园林修剪机器人,并对园林修剪机器人末端执行机构刀具进行优化设计与稳态特性研究,最终达到设备稳定修剪的目的;阐述了园林修剪机器人末端中机构的结构、工作原理及操作方法;以多种组合刀具为研究对象,利用ANSYS有限元分析以及其Ls-Dyna有限元显式求解程序对多种组合修剪刀具进行静力学分析、模态分析及动力学仿真计算,构建出应力值与应变值、刀具齿数、刃口形状的关系模型;然后,进行齿数、刃口形状对刀具进行稳态特性优化,研究稳态性能,找出刀具最优组合。结果表明:最佳刀具组合为100齿双刃,其最大应力、最大应变值分别为5.3475×10^(6)Pa、2.6342×10^(-5)m/m,刀具共振频率为243Hz。切割动力学仿真分析表明:刀具在切割外径8mm的树枝时,刀具修剪能量变化均匀,对树枝修剪产生的切割力呈现有规律的曲线,最大切割力为498N。智能园林修剪机器人修剪试验结果表明:修剪刀具在不同的转速下进行园林修剪,呈现出良好的稳态特性,运行平稳,刀齿端磨损较少,无共振现象,达到了设计目标要求。

考虑结合面特性影响的机床整机有限元静力学分析模型

针对机床数字化设计中典型结合面建模精度误差较大的问题,提出了一种采用虚拟材料等效结合面静力学特性的方法,建立了考虑结合面特性影响的机床整机有限元静力学分析模型,并完成了相应的静刚度测试实验。首先,综合考虑了弹塑性变形机制和摩擦力的影响,提出了一种新的结合面法向和切向刚度的分析模型;其次,根据不同类型结合面的特点,采用虚拟材料模拟结合面的刚度特性,建立了刚度特性与虚拟材料弹性模量和泊松比的关系,并将其应用于精密数控机床整机的静刚度分析;最后,开展了整机工艺系统的静刚度测试实验,得到了主轴末端X、Y、Z三个方向的刚度分别为26.60 N/μm、41.87 N/μm和40.17 N/μm,并将其与仿真数据进行了对比。研究结果表明:不考虑结合面影响的模型相对误差将近17%,而考虑结合面影响的模型相对误差在5%以内,验证了考虑结合面特性影响的机床整机有限元静力学分析模型的有效性;采用虚拟材料等效结合面静力学特性的方法可作为机床数字化设计的一种可行的方法。

断屑槽形状对硬质合金刀具切削性能的影响分析

在切削加工过程中,切削力可以反映切削刀具的切削性能,直接影响加工精度及加工质量。为了分析不同形状的断屑槽对硬质合金刀具切削性能的影响,利用数值仿真技术对切削加工进行有限元模拟。分析结果表明,不同形状的断屑槽对硬质合金刀具切削性能的影响程度存在差异,其中,直线圆弧形断屑槽对应的硬质合金刀具切削性能最好。

回注泵液力端承压能力提升研究

钻屑回注泵液力端存在易疲劳开裂的现象,维护成本极高。在高泵注压力条件下,钻屑回注泵液力端内应力峰值较大,排出孔相贯口处易开裂,导致钻屑回注泵使用寿命较短。为此,利用ANSYS软件对液力端进行静力学分析,分析发现,在排出工况下液力端相贯区域为应力集中区域,最大应力值为725MPa,利用FACET修型技术优化之后,最大应力值降为636MPa。

基于ANSYS的模切机曲轴静力学与模态分析

模切机曲轴的性能影响模切的速度和精度。本文分析现有模切机曲轴特性,对曲轴进行有限元分析,运用Solidworks软件建立曲轴三维模型,导入ANSYS Workbench软件模拟分析曲轴在模切机工作时的静态力学特性以及曲轴的振动特性,得到了应力、应变云图和模态振型图。静力分析结果表明,最大应力为242.54MPa,小于轴的屈服极限强度,符合实际要求。模态分析结果表明,曲轴在低阶频率下以弯曲变形为主,最大振型位移出现在曲轴的两端;在高阶频率下以弯曲和扭转变形为主,主要发生在曲轴的两端连接肘杆的轴端。得到该曲轴的最小固有频率,为该曲轴的可靠性分析、疲劳强度校核提供计算依据。

基于元操作的智能合约漏洞检测方法

针对静态分析工具由于漏洞扫描流程代码强耦合于工具代码中导致其扩展漏洞成本较高的问题,文中提出了基于元操作的智能合约漏洞检测方法。该方法将工具中的基本检测流程转换为元操作抽象形式,通过不同元操作和逻辑运算符组合来自定义漏洞扫描流程,以达到通过编写少量漏洞扫描流程语法就可以实现检测不同漏洞,提高工具对智能合约新型漏洞的扩展能力。实验结果证明,根据文中方法所需编写的漏洞描述字符量仅为Slither工具漏洞检测逻辑字符量的8.9%~12.7%,假阳率相比Slither工具降低2%。证明了所提方法可以在保证工具检测可靠性的基础上提供了更强的扩展性和灵活性。

Cutting force and its frequency spectrum characteristics in high speed milling of titanium alloy with a polycrystalline diamond tool

In this paper, a series of experiments were performed by high speed milling of Ti-6.5Al-2Zr-1Mo-1V (TA15) by use of polycrystalline diamond (PCD) tools. The characteristics of high speed machining (HSM) dynamic milling forces were investi- gated. The effects of the parameters of the process, i.e., cutting speed, feed per tooth, and depth of axial cut, on cutting forces were studied. The cutting force signals under different cutting speed conditions and different cutting tool wear stages were analyzed by frequency spectrum analysis. The trend and frequency domain aspects of the dynamic forces were evaluated and discussed. The results indicate that a characteristic frequency in cutting force power spectrum does in fact exist. The amplitudes increase with the increase of cutting speed and tool wear level, which could be applied to the monitoring of the cutting process.

重切龙门镗铣加工中心结构静动态特性分析

为了在设计阶段精准评估重切龙门镗铣加工中心结构的动静态特性,建立加工中心整机结构有限元仿真模型,分析其静、动态特性。通过模态测试验证动态仿真模型的准确性和有效性,根据分析结果提出加工中心的结构优化建议。结果表明:由于滑枕的静刚度不足,导致加工中心Y方向的静刚度较低,在1 500 N切削力作用下,最大变形可达0.008 137 mm;加工中心的前6阶实测固有频率分别是41.87、55.69、88.06、103.45、129.68、159.41 Hz,前6阶固有频率的平均仿真计算误差为6.5%,立柱和滑枕位置在外部激振力作用下易发生较大的动态变形响应。

基于干扰观测器的非轴对称表面零件加工快速刀具伺服控制方法

非轴对称表面零件具有复杂的表面形状,刀具控制过程中难以应对加工过程中的等效干扰,使得加工精度不高。针对上述问题,提出基于干扰观测器的非轴对称表面零件加工快速刀具伺服控制方法。基于快速伺服刀具动态行为分析结果,干扰观测器计算等效干扰并以此得出扰动补偿量。以扰动补偿量和动态行为分析为基础,分别设计等效控制律和切换控制律,通过增量滑模控制器实现非轴对称表面零件加工快速刀具伺服控制。实验结果表明,所研究方法刀具伺服控制边界与监控边界高度重合,且跟踪偏移量数值为±0.02μm,具备更高的加工精度和跟踪稳定性能。

切削17-4PH不锈钢时刀具磨损对切削过程的影响分析

为了探究刀具磨损对切削力和已加工表面温度的影响,考虑实际切削过程中的刀具磨损类型,建立了不同磨损类型的刀具几何模型,采用DEFORM软件建立17-4PH不锈钢正交切削有限元模型。基于有限元模型研究了刀具磨损对切削温度、分流点和接触表面应力等的影响规律,并通过切削实验验证磨损模型的可靠性,研究了后刀面磨损与切削力之间的演化规律。结果表明:前刀面磨损在一定程度上可以降低切削力和切削温度,其余磨损形式会增大切削力;随着后刀面磨损VB的增大,犁耕效应显著,切削力增大较为明显,而接触面的应力变化不明显。

电力金具螺栓紧固机器人研制

在高压线路拆装螺栓时,螺母可能会随螺栓同步转动,很难保证工作的准确性。而且目前的工装只适用于一种规格的螺栓尺寸。以高压输电线路电力金具引流板螺栓为作业对象和任务进行了分析,研究提出了一种红外传感器检测电力金具螺母松动时可以到达指定位置并进行电力金具引流板螺栓紧固的机器人,所研制的电力金具螺栓紧固机器人主要由移动升降平台、机械臂、螺栓紧固工装组成。研究了螺栓拧紧工装的机械结构和万能套筒,分析了工装的性能以及万能套筒静应力学。通过试验和模拟现场验证了所提出的构型方案的正确性和有效性,能够为机器人系统拧紧螺栓提供帮助,并为后续的视觉方案提供设计思路。本设计的拧紧工装提高了在视觉识别过程中的容错率,解决了螺栓旋转螺母跟着转动的问题。

数控机床切削过程中的振动分析与控制策略研究

数控机床切削过程中振动问题成因复杂且对切削加工精度、质量、效率等有较大影响。梳理了数控机床切削的振动的影响因素、振动机理、振动衡量等基础概念,以及金属切削过程的主动、被动和半主动颤振控制技术;从数控机床切削颤振控制技术发展、控制逻辑以及基于数理模型的控制模型建构逻辑角度等探讨颤振的控制策略,并从系统动力学、多元数据融合、智能控制等角度予解释。

基于检验需求的矿用电缆截断系统及关键部件设计

在矿用电线电缆质量安全检测检验工作中,针对大量同一样品不同长度的线缆试样需求,以及线缆线径较粗的现状,提出一种可实现大截面线缆定距切割的截断系统。结合矿用电缆的检测实际检测检验需求以及待检产品特性,对矿用线缆截断系统进行总体设计,并对系统主要部件,截断机构进行设计验证。运用ANSYS有限元分析软件分析切割过程中切割刀具的力学响应,结果显示,切刀在最大载荷200 kN切割力作用下,整体变形最大位移量为0.18292 mm,最大应力为471.33 MPa,安全系数大于2。现场试验证明该系统安全可靠,效率提升达30倍,具有推广应用价值。

拉西瓦水电站水轮机剪断销剪断原因分析及专用拆卸工具设计

剪断销作为水轮机导水机构的安全保护装置,在水轮机的安全、稳定运行中起着关键的作用。文章针对拉西瓦水电站近年来剪断销频繁剪断原因进行归纳分析,并通过Solidworks建模设计出专用剪断销拆卸的工具,解决剪断销拆卸困难的问题。该设计在实际应用中获得良好的效果,对水电站今后类似问题的处理具有一定的参考意义。

井下采煤机截割滚筒的行星架性能研究

以MG1000/2500-WD型大采高采煤机为研究对象,介绍一种行星架优化设计方案。基于多体动力学理论,采用ADAMS软件构建采煤机截割动力学仿真模型,并从两级行星架静力学分析和行星架疲劳寿命分析2个角度综合分析行星架性能,以确认行星架受力薄弱点,并以此为基础介绍行星架优化设计方案。将优化设计方案应用于实际工程,结果表明,与优化前相比,优化后行星架的综合性能有效提升。