空化射流效应的实验研究

在对空化射流实验研究的基础上，研究了提高射流冲蚀性能的基本参数。分析这些参数得出如下结论：最佳冲蚀效果的有效靶距直径比为6，最佳冲蚀时间为3min；空化射流深度冲蚀能力平均为普通射流深度冲蚀能力的2倍，空化射流切缝直径是普通射流切缝直径的2．3倍；空化射流有利于深孔与大孔的切割，但随着围压的增大，冲蚀能力减弱。     

浮动式高分子管多缝对切装置的设计研究

高分子管是堆叠式高分子材料椎体扩张器的关键部件。为满足其功能需要,需在其侧壁上切出36条窄缝。如何快速、准确、可靠地在高分子管壁上按要求切缝是高分子材料椎体扩张器研发的关键问题之一。文中通过对切缝方案的分析研究,设计了浮动式高分子管壁多缝对切装置。通过对装置中分度机构、对切机构和夹紧机构的合理设计,有效解决了高分子管壁切缝的3大难题,并通过实验表明使用该装置切割窄缝操作简单、高效,切割出来的切缝尺寸及分布符合图纸要求。     

堆叠式椎体扩张器“高分子团”形成规律的研究

堆叠式高分子材料椎体扩张器前端的高分子管在工作状态下受轴向压力堆叠成"高分子团"以扩张塌陷椎体,高分子团的形状和尺寸直接影响椎体后凸成形手术的质量和效果。因此研究高分子管管壁切缝尺寸及分布与由其堆叠而成的高分子团尺寸、形状之间的关系,是椎体扩张器研发的关键问题之一。通过建立数学模型,推演出手术要求的高分子团的规格与高分子管管壁上切缝的尺寸及分布的规律,得出数学计算公式,并举例验证了切缝尺寸计算公式和分布规律的正确性,从而提高椎体扩张器的工作可靠性和效果可预测性。     

光纤激光切割不锈钢薄板工艺参数研究简

利用连续光纤激光器对0.3mm厚不锈钢薄板的切割工艺进行研究,分析了离焦量、激光功率、切割速度和调制频率对切缝宽度和切缝质量的影响.实验结果表明,实际应用时,不能只考虑一个因素,应选择适当参数,以获得所需的切缝宽度和较好的切缝质量.     

光纤激光切割不锈钢薄板工艺参数研究

;利用连续光纤激光器对0.3mm厚不锈钢薄板的切割工艺进行研究,分析了离焦量、激光功率、切割速度和调制频率对切缝宽度和切缝质量的影响。实验结果表明,实际应用时,不能只考虑一个因素,应选择适当参数,以获得所需的切缝宽度和较好的切缝质量。     

碳纤维增强复合材料水导激光切割试验研究

采用正交试验方法对影响水导激光切割碳纤维增强复合材料（CFRP）的关键工艺参数进行了深入研究,得出了进给速度、水射流速度、脉冲频率和激光功率对切割CFRP的影响规律,并用直接对比法和极差分析法所得最优参数进行单次划槽切割对比。研究结果表明：在极差分析法所得最优参数下切割CFRP时,切缝深度增大3.2%、切缝宽度减小9.2%、切缝锥度减小11.8%、线粗糙度减小40.2%。通过与干式激光加工方法对比发现,水导激光加工技术在切割CFRP方面优势明显,由于水射流的冲刷和冷却作用,材料切割表面几乎无热影响区和纤维拔出。另外,采用正交试验所得最优工艺参数实现了4 mm厚度CFRP的无锥度切割。     

激光切缝图形对金刚石圆锯片噪声的影响

根据金刚石圆锯片基体上激光切缝图形降低噪声的原理，设计了几种激光切缝图形的消音金刚石圆锯片；对金刚石圆锯片的噪声进行了对比测试研究，分析了不同激光切缝图形、喷水、槽宽等各种因素对噪声的影响。结果表明金刚石圆锯片基体上合理的激光切缝图形降低噪声的效果是相当明显的。     

线切割加工中切缝宽度与材料去除率的优化研究

在精密制造业中,切缝宽度对尺寸精度的影响尤为显著,而材料去除率是影响加工效率的最重要指标,其与切缝宽度之间关系复杂且相互制约,一组加工参数难以同时获得较小的切缝宽度和较高的材料去除率。针对此问题,运用BP神经网络与粒子群算法(PSO)的混合算法建立多目标预测优化模型;以Ti6Al4V合金为实验对象,以水压、脉冲时间、脉冲间隙、伺服电压和电极丝张力为工艺参数,以切缝宽度(Kerf)和材料去除率(MRR)为工艺目标,设计田口实验。结果显示,Kerf和MRR的预测平均相对误差分别为5.32%和6.14%,优化得到单目标和多目标最优工艺参数,Kerf同比降低11.10%,MRR同比提高27.37%,表明对切缝宽度和材料去除率的预测与参数优化效果显著。     

平板闸门淹没出流流量的实验研究

搭建了一个水力学的实验模型,并对平板闸孔淹没出流的流量进行了实验,利用理论分析方法分析了平板闸门在淹没出流的流态下的流量计算公式,得出了淹没出流流量值主要与流量系数有关。为了对其流量系数进行研究分析,以常用的3种淹没出流流量系数的计算公式计算出流量,将计算得出的3种理论流量值分别与实验测得的流量值进行对比,得出了最优的计算方法,为工程应用中淹没流量系数计算公式的选择提供了实验依据。     

通过整体叶盘切缝的振动抑制方法初探

针对航空发动机整体叶盘设计在进一步降低发动机质量、减少连接件复杂性的同时，也带来阻尼不足引起的振动问题，首先，提出了一种基于叶盘切缝并辅以填充物的方法，使系统在振动过程中产生非弹性碰撞能量损耗以及填充材料的阻尼损耗，从而为整体叶盘振动提供额外的阻尼；其次，建立了切缝整体叶盘与切缝填充后的时变参数动力学简化模型；最后，分别从仿真与实验的角度对切缝整体叶盘与切缝填充后的自由振动响应进行了分析，并利用希尔伯特变换法，识别了整体叶盘结构的瞬时频率以及瞬时阻尼比。结果表明，整体叶盘切缝的碰撞与填充物可以增加系统阻尼，能够起到抑制振动的作用。     

Finite element analysis of laser inert gas cutting on Inconel 718

Inconel 718 has high strength, which makes it difficult to cut using conventional cutting methods. In the present study, the laser inert gas cutting of Inconel 718 was simulated by finite element analysis software ANSYS. Finite element method was used to predict thermal stress and kerf width formation during the laser cutting process. ANSYS Parameter Design Language was used to model the Gaussian-distributed heat flux from the laser beam acting on the workpiece. The removal of melted material during laser cutting to form the kerf width was modeled by employing the element death methodology in ANSYS. In addition, laser cutting was simulated at continuous wave (CW) and the effects of laser power and cutting speed on kerf width were investigated. A series of experiments were carried out to verify the predictions. The temperature fields on the workpiece were measured using thermocouples. The kerf width size was measured using a profile projector, whereas the metallurgical and morphological changes at the cutting edge were examined using scanning electron microscopy. A good correlation was found between the simulation and experimental results.     

基于气熔比的氧化锆陶瓷薄板激光切割质量研究

采用一种基于气熔比控制的激光精密切割方法,研究了气熔比和板厚对激光切割氧化锆陶瓷板质量的影响,即气熔比对切缝质量、切面条纹形貌及粗糙度的影响。对气熔比分别为0.099、0.160、0.184和0.202的4组试件进行观测,发现提高气熔比可明显改善切缝质量,增大切面条纹光滑区长度和条纹波长,切面粗糙度由6.969μm降低到2.482μm。同时对板厚分别为0.8mm、1.0mm、1.5mm、3.0mm的4组试件进行观测,随着板厚的增加,气熔比减小,切缝质量降低,切面粗糙度由5.946μm降低到2.287μm。板厚为0.8mm、1.0mm时,切面为较光滑的周期性条纹;板厚为1.5mm时,切面呈现两个区域,即光滑区和粗糙区;当板厚增加到3.0mm时,切面呈现三个区域,即光滑区、粗糙区和鳞状层叠区。综合研究气熔比和板厚可以加深对激光切割机理的认识,为提高氧化锆陶瓷板的激光切割质量提供理论与实验依据。     

A key parameter to characterize the kerf profile error generated by abrasive water-jet

As the only cold high-energy beam machining technology, abrasive water-jet (AWJ) is one of the most rapidly developed techniques in material manufacturing industry. However, the application of AWJ is limited by the cutting accuracy it can achieve. Kerf profile generated by AWJ is different as the cutting parameters change. As a result, it has become a major factor which affects the cutting accuracy when AWJ is used as a machining tool. Researchers used taper error to characterize kerf profile error generated by AWJ in the past years. And many efforts have been put on how to eliminate taper error by using a tilting cutting head of a 5-axis AWJ machine. However, using taper error to characterize the kerf profile error generated by AWJ is not accurate since kerf profile error might appear in different styles. And using a 5-axis AWJ machine to eliminate taper error is only effective in some special cases. To effectively eliminate taper error, the first thing needs to do is to find out whether the kerf profile error can be compensated or not. Based on research, a key parameter, named kerf profile coefficient O, which can be used to characterize kerf profile error and further to guide people to use different ways to compensate kerf profile error, has been defined in this paper. To further illustrate the efficiency of this coefficient, a series of cutting experiments have been carried out and the experimental results have been discussed.     

CO2 laser cutting of Kevlar laminate: influence of assisting gas pressure

In the present study, laser cutting of Kevlar laminate is considered, and the effect of assisting gas pressure and laser output power on the end product quality is examined. The end product quality is judged via measurement of out-of-flatness and kerf width ratios. Experimental tests are carried out using a CO₂ laser beam with pulse repetition rate of 300 Hz. The cutting model introduced previously is accommodated to predict the kerf size for various laser output power and assisting gas pressures. The predictions are compared with the experimental results. It is found that the predictions of kerf size are in good agreement with the experimental results. The influence of assisting gas pressure is significant on the resulting cut quality, in which case, out-of-flatness and kerf width ratio improve considerably at high assisting gas pressures (500 kPa).     

Experimental investigation of kerf characteristics through wire electrochemical spark cutting of alumina epoxy nanocomposite

Alumina epoxy nanocomposite (AENC) is an emerging class of composites with a wide range of functionality and applicability; however, managing AENC using a machine is difficult because of its special mixed characteristics. The presence of extremely hard alumina particles in soft epoxy matrix enhances material properties. The present work investigates the kerf characteristics of a straight cut made in AENC through Wire electrochemical spark cutting (WECSC) process. The kerf characteristics, such as kerf deviation and taper, are used to measure the cut quality. The applied voltage, electrolyte concentration, wire velocity, pulse on-time and pulse off-time are varied, and their effects on the kerf characteristics are experimentally investigated in a developed setup. Influencing parameters for straight cutting of AENC are applied voltage, concentration of electrolyte and wire velocity.

     

Laser cutting of 7050 Al alloy reinforced with Al2O3 and B4C composites

In the present study, laser cutting of 7050 aluminum alloy sheets reinforced with Al₂O₃ and B₄C particles are carried out. The cut geometry is examined using scanning electron microscope and the optical microscope. The lump parameter analysis technique is used to formulate and determine the kerf width size. The predictions for kerf width are compared with experimental data. The percentage kerf width size variation along the cut edges is determined and the influence of the laser power level and duty cycle of the laser pulses on the percentage kerf width size variation is examined. It is found that 7050 aluminum alloy reinforced with 20% Al₂O₃ composite results in relatively large kerf width size as compared to its counter parts that corresponding to 7050 aluminum alloy reinforced with 20% B₄C composite. The kerf width size predicted agreed with the experimental data for both composites.     

Development of an algorithm for optimum control process to compensate the nozzle wear effect in cutting the hard and tough material using abrasive water jet cutting process

In the process of abrasive water jet cutting, the change of nozzle diameter, due to nozzle wearing throughout cutting process, causes a decrease in surface quality and an increase in kerf width. In this paper, a series of experiments have been done to determine the effect of process parameters and the results show that traverse speed and nozzle diameter are significant parameters on the kerf quality and geometry, and a control program algorithm is suggested to compensate the effect of nozzle diameter increase on cut surface quality and kerf width and the control program creates an offset with required amount in nozzle path.     

车轮残余应力测试方法研究

采用仿真分析的方法研究了火车轮径向锯切过程中锯缝宽度的变化以及锯缝附近踏面上应力/应变的变化规律。分析表明,当锯切深度达到轮辋与辐板连接处时,锯缝附近残余应力的释放已经十分充分,可根据残余应力的释放情况计算踏面上残余应力的大小。按照径向锯切方法,在锯缝附近粘贴应变片,径向锯切到轮辋与辐板连接圆弧处时停止锯切,依据应变片记录的应变值可计算踏面上的残余应力。     

Single and dual gas jet effect in Ytterbium-doped fibre laser cutting of dry pine wood

This paper presents single and dual assist gas jet effects in the single-pass laser cutting of dry pine wood. The laser wood cutting process is influenced by the assisting gas jet(s) applied. Therefore, it is important to understand their roles in the removal of fumes and combusted materials from the cutting kerf. A computational fluid dynamic model is developed to investigate the effect of single and dual gas jets in the laser wood cutting process. In order to obtain a close approximation of the actual process, a three-dimensional model was considered. Results obtained in the simulations were compared with experimental data collected from a multifactor experiment analysing the laser cutting process of dry pine wood. A high brightness, 1?kW IPG single-mode, continuous-wave Ytterbium fibre laser was employed to cut cubic wood samples parallel to the wood fibre direction. It has been found that shear stresses produced by the gas jet(s) on the kerf walls have an important correlation with the yield and cut quality.