基于ANSYS的镍钛合金心血管支架光纤激光切割温度场仿真

为了研究光纤激光切割镍钛合金心血管支架过程中温度场分布情况,通过ANSYS有限元软件模拟建立了镍钛合金心血管支架三维仿真模型,运用APDL编程语言,实现高斯热源沿轨迹移动。采用单因素变量方法,探究激光功率、切割速度对不同切割轨迹温度分布以及变化的影响。结果表明,激光切割镍钛合金管时温度场分布近似为椭圆形,靠近热源中心处等温线分布较密集,远离热源中心等温线分布较稀疏。切割区域温度随激光功率的升高而增大,随切割速度的升高而降低。激光功率过大或切割速度过小时,会使熔渣在镍钛合金管内表面堆积严重。激光功率过小或切割速度过大时,会导致传递到管壁的热量不足,工件难以切透。仿真结果对实际切割参数的选取提供依据。     

多自由度旋转激光切割头研制

针对普通激光切割机切割头存在的旋转不灵活及旋转自由度少等问题,优化了激光切割头多自由度旋转控制方式,研制了能够在立体空间上进行多自由度转动的激光切割头,实现了激光切割机对船舶舾装任意形状工件的切割功能,解决了因切割表面不平整而容易损伤切割头的问题。实验证明,改进的切割头具有更好的切割效果。     

船舶舾装数控激光切割机关键技术研究

针对现有船舶舾装数控激光切割机作业曲线受限、转角作业损伤工件以及作业过程中遇到障碍物损毁电机的问题,从激光切割头多自由度旋转控制的优化设计、增加转角保护系统及船舶舾装数控激光切割机外力过载保护器等三方面对船舶舾装激光切割机关键技术进行研究,实现了激光切割机对船舶舾装任意形状工件的切割功能,解决了激光切割工件易损伤和切割机电机易烧毁等问题。     

YAG激光切割不锈钢切缝宽度影响因素分析

采用YAG激光对厚度为1 mm的1Gr17Mn6Ni5N薄钢板进行切割试验,通过正交试验设计的直观分析法和方差分析法对上下切缝宽度试验数据进行处理,系统地分析了激光功率、脉冲宽度、重复频率各参数对激光切割薄钢板的上下切缝宽度的影响规律,为激光切割加工时工艺参数的选取提供了依据。     

数控技术在避免激光切割工件烧损上的研究与应用

本文论述了通过开发M70数控系统的"工作数据读取功能",结合PLC程序的开发,使M70数控系统能够随时获得运行速度数据,实现了根据速度变化对激光功率的控制,从而避免了激光切割工件烧损的问题。这一技术对数控系统在激光切割机上的应用具有极大意义。     

基于正交试验钛合金激光切割工艺参数优化

激光切割质量受各种因素的影响,为了得到高质量的激光切割件,需要根据不同的切割板材进行优化。利用厚度1.5mm的TC1薄板作为研究对象,研究激光功率、切割速度、焦点位置和辅助气体压力主要因素对激光切割质量的影响,采用正交试验方法安排激光切割试验,使用L16(45)正交表,完成十六组激光切割试验。利用测量点轮廓精度的算术平均值作为结果进行分析,采用直观分析法,因素效应曲线图,方差分析对切割参数进行分析研究。结果表明:切割速度和辅助气体压力是主要因素,对切割质量和精度有较大影响,而激光功率对切割后试件的轮廓度影响较之上两个因素小,但是激光功率改变对切割件的表面质量影响显著。     

烧结钕铁硼激光切割质量工艺影响研究

探讨工艺参数对激光加工烧结钕铁硼的影响,对烧结钕铁硼磁性材料进行激光切割试验,以割缝宽度、R_a和熔渣量为衡量指标。通过正交试验探讨电流、脉宽、频率和氧气压力等工艺参数对切割质量的影响,研究分析得出激光切割烧结钕铁硼的最佳工艺参数。增加电流及氧气气压,降低加工脉宽及频率,有利于提高切割质量。切割截面可分为光亮区和熔融区,工艺参数不同,切割后两个区域所占的面积也不同。     

激光切割低碳钢板工艺试验研究

本文通过各项试验找出了各基本工艺参数对激光切割表面熔渣高度、表面粗糙度、切缝宽度、尖角熔损长度及热影响的影响规律性，可供从事激光切割工作人员参考。     

切割速度对6061铝合金薄板激光切割温度场的影响

为了揭示切割速度对6061铝合金薄板激光切割过程中温度场的分布及工艺规律，利用有限元软件对2 mm厚铝合金薄板在不同激光切割速度下的温度场进行数值模拟，并通过实验对仿真结果进行验证。仿真结果表明：当激光切割速度为80 mm/s时，工件的热影响区宽且熔深大，切缝处较宽范围内的材料均已达到熔点温度，随着切割速度增大，热影响区宽度、切缝处材料熔化量及熔深均逐渐减小。当切割速度为120 mm/s时，工件的熔深刚好达到材料的厚度。实验结果表明，当切割速度过低时，切缝处材料熔化量过多，在底部形成较厚的挂渣，随着切割速度增大切缝质量得到有效改善，但切割速度过大则会导致切缝处材料熔化量减小，粗糙度增大，切割速度为120 mm/s时，切缝质量最好。实验结果与仿真结果一致性较好，证明了仿真结果的准确性。     

激光切割

一、激光切割的现象和原理激光切割是将激光束经透镜等集光系统得到高密度的光能,使被切割部位加热汽化,穿孔进行切割。现在的激光切割,一般都是与激光束同轴吹进气体,除极薄板的微细加工外,大多使用氧气或其它气体做辅助气体。利用气体辅助切割,对铁系材料来说有如下效果。1.氧气和铁的氧化反应热可以帮助加工部位的熔化;2.使生成的熔渣流动性好,并由气流将熔化     

MICROMILLING IN MINIMUM QUANTITY LUBRICATION

This study investigates micromilling of 316 L stainless steel under minimum quantity lubrication. A laser-based technique was developed to measure spindle runout and assist tool setting for fragile micro cutting tools. Thresholds were established to help select cutting parameters and avoid catastrophic tool failure. Computational fluid dynamics was used to simulate flow of lubricant microdroplets around a rotating tool. When properly applied to wet the tool and workpiece, minimum quality lubrication reduces the build up edge on a cutting tool and increases the tool life up to 100 times compared to dry micromilling of 316L and stainless steel.     

三角皮带轮单辊轮辊轧成形机理的研究

研究实心钢制三角皮带轮的辊轧成形工艺,进行了单轧辊连续进给的辊轧成形实验,并运用DEFORM软件对辊轧成形过程进行数值模拟。研究表明,成形过程中工件的内径将会增大,其原因是变形区的金属产生了切向流动所致;在稳定变形时,切向流动小,对工件内径影响小,而随着变形过程,金属的径向和轴向流动阻力加大,切向流动增强,导致工件内径产生显著变化,甚至造成工件失稳;因此,解决金属的切向流动时皮带轮辊轧成形工艺的关键。     

Optimisation for hot turning operations with multiple performance characteristics

This paper presents an investigation on the optimisation and the effect of cutting parameters on multiple performance characteristics (the tool life and the workpiece surface roughness) obtained by hot turning operations. A plan of experiments based on the Taguchi method was designed. M20 sintered carbide as tool and the high manganese steel as workpiece material were used in experiments. The workpiece material heated with liquid petroleum gas flame was machined under different settings of feed rate, depth of cut, cutting speed and workpiece temperature on a lathe. The results showed that cutting speed and feed rate were the dominant variables on multiple cutting performance characteristics. An optimum parameter combination was obtained by using statistical analysis.     

Dynamics of a rotating Rayleigh beam subject to a repetitively travelling force

The dynamics of a rotating Rayleigh beam subject to a force travelling at a constant speed along the axial direction is studied. The beam is chosen as a simple model of the workpiece in the lathing process. A technique is developed for modeling the repetitive cutting force on the workpiece. The amplitude of the cutting force is chosen to be either constant or dependent on the motion of the beam. The discretized equations of motion of the rotating beam are obtained by Galerkin’s method. The time response of the rotating beam subject to the external force is discussed. The possible resonant conditions resulting in divergent solutions are studied. The stability of the response, due to a travelling motion-dependent force, is determined by the method of multiple scales. The effects of varying the rotating frequency, the travelling speed of the external force, and the movement of the force are also investigated.     

Effect of high-frequency orbital and vertical oscillations of the laser focus position on the quality of the cut surface in a thick plate by laser beam machining

In laser beam machining with oxygen gas, striations are formed on the cut surface due to the cyclic oxidization reaction, which is affected by the cutting conditions and the thermal properties of the workpiece. The formation of striations causes an increase in surface roughness. In order to reduce the surface roughness, we propose controlling the formation of striations by utilizing multi-DOF oscillation of the focus position of the laser. In this paper, we construct a laser machining system in which positioning control of the focus position is achieved by driving the focal lens. The effect of orbital oscillation of the laser focus position parallel to the top surface of the workpiece and vertical oscillation perpendicular to this surface on the formation of striations was evaluated by performing laser cutting tests on thick mild steel plates. The experimental results show that control of the formation of striations can be realized by choosing the appropriate oscillation conditions. The surface roughness with oscillation was less than half that without oscillation.     

Dross formation and process parameters analysis of fibre laser cutting of stainless steel thin sheets

The coronary stent fabrication requires a high-precision profile cut. Fibre lasers present a solution to accomplish these requirements. This paper presents an experimental study of fibre laser cutting of 316L stainless steel thin sheets. The effect of peak pulse power, pulse frequency and cutting speed on the cutting quality for fixed gas type and gas pressure was investigated. A mathematical model based on energy balances for the dross dimensions was formulated. The dross height and the dross diameter were analysed and compared with the experimental results. This allows adjustment of the process parameters to reduce the dimensions of the dross deposited at the bottom of the workpiece during laser cutting of thin sheets.     

Dynamic analysis of a rotating beam subjected to repeating axial and transverse forces for simulating a lathing process

The dynamics of the workpiece of a lathe is simulated in the presented paper. A rotating Rayleigh beam is chosen as a simple model of the workpiece. The beam or the workpiece is subjected to forces from the cutting tool of the lathe. The external forces, in transverse and axial directions, are traveling in a repeating or periodic motion. The force in the axial direction is a large cutting force resulting in coupled bending deformation while forces in the transverse directions are the contacting forces.In this paper, the governing equations of the rotating Rayleigh beam are derived by Hamilton's principle. The external, periodic forces resulted from the tool are expressed in Fourier series. Galerkin's method is then chosen for disceretizing the partial differential equations. The instability regions of the responses are determined by using the method of multiple scales and the Floquet theory. Fast Fourier transform gives the frequency domain responses for examining the dynamic characteristics. The numerical results are discussed. Parametric studies are also performed.     

Multi-response optimization of machining parameters in hot turning using grey analysis

This paper envisages the multi-response optimization of machining parameters in hot turning of stainless steel (type 316) based on Taguchi technique. The workpiece heated with liquid petroleum gas flame burned with oxygen was machined under different parameters, i.e., cutting speed, feed rate, depth of cut, and workpiece temperature on a conventional lathe. The effect of cutting speed, feed rate, depth of cut, and workpiece temperature on surface roughness, tool life, and metal removal rate have been optimized by conducting multi-response analysis. From the grey analysis, a grey relational grade is obtained and based on this value an optimum level of cutting parameters has been identified. Furthermore, using analysis of variance method, significant contributions of process parameters have been determined. Experimental results reveal that feed rate and cutting speed are the dominant variables on multiple performance analysis and can be further improved by the hot turning process.     

Workpiece temperature rise during the cutting of AISI 4340 steel

Temperature rises in workpieces were measured during the cutting of various hardnesses of steel by a ceramic tool. Thermocouples were embedded in a specially designed workpiece for the temperature measurement. This workpiece provided practical and accurate positioning of the thermocouples and it allowed the acquisition of reliable data from the cutting experiments. The effects of the workpiece hardness and cutting speed were examined and analyzed. The relationships between the workpiece temperature rise and residual stresses or structural change in a machined surface layer were discussed.It is concluded that the temperature rise in a steel workpiece during cutting by a ceramic tool is so low that it is less likely to cause any surface damage under normal conditions.     

锯齿形切屑的计算机仿真

采用有限元方法仿真了不同切削速度下加工45钢的切屑形成过程。结果表明，较低切削速度下形成连续带状切屑，而高速切削时形成锯齿形切屑。通过对工件和切屑应力及温度分布的分析，探讨了锯齿形切屑的形成机理及影响因素。