不锈钢薄板的激光弯曲成形试验研究

以不锈钢薄板的激光弯曲成形为研究对象，通过实验研究其成形过程及影响因素。首先介绍了激光成形的工艺过程及影响因素；然后通过试验研究了激光能量、扫描速度、激光光斑大小和扫描次数等因素对弯曲成形角度的影响。     

板料激光弯曲成形技术的研究现状及展望

综述了近年来国内外对激光弯曲成形技术的研究现状,概述了激光工艺参数、板料几何参数及材料性能等因素对弯曲成形的影响,分析了扫描轨迹对成形结果的影响以及激光成形闭环控制系统的应用,并对板料激光弯曲成形的应用和发展前景作了展望。     

板料激光弯曲成形技术的研究现状及展望

综述了近年来国内外对激光弯曲成形技术的研究现状，概述了激光工艺参数、板料几何参数及材料性能等因素对弯曲成形的影响，分析了扫描轨迹对成形结果的影响以及激光成形闭环控制系统的应用，并对板料激光弯曲成形的应用和发展前景作了展望。     

管材激光弯曲成形的试验研究

进行了管材激光弯曲的试验研究,确定了工艺参数范围及扫描方式。通过单因素试验法研究了不同的激光参数(激光功率、扫描速度、离焦量和扫描包角)、扫描次数和管径对弯曲角度的影响规律,从而得到了单因素条件下的最佳工艺参数,为激光弯曲成形零件提供了应用基础。     

厚钢板激光多次扫描弯曲成形的研究

采用数值模拟和实验研究分析了厚钢板激光多次扫描弯曲成形过程中弯曲角度与激光扫描次数之间的关系。建立三维热力耦合有限元模型计算了成形过程的温度场、应力场和弯曲角度的变化,对不同厚度钢板的激光多次扫描弯曲成形过程进行了实验研究,模拟结果与实验结果符合较好。在相同的工艺参数条件下,钢板越厚,弯曲角度越小。钢板弯曲角度随激光扫描次数的增加而增大,但对不同厚度钢板,它们的变化规律不同。钢板下表面的应变强化是多次扫描过程中随扫描次数增加而弯曲角度增量减小的主要原因。     

不锈钢钢板热应力成形试验研究及其工艺参数评价

以不锈钢钢板为研究对象,通过改变激光光束能量、光斑直径、机床扫描速度、扫描次数以及扫描路径对不锈钢钢板进行弯曲试验,研究了厚度一定的不锈钢钢板弯曲成形时的工艺参数对弯曲角度的影响,并对热应力弯曲成形的工艺参数进行评估。     

铝合金交叉筋壁板激光多道扫描成形研究

本文利用激光诱导热成形技术对5A06铝合金交叉筋壁板进行圆柱面弯曲成型的过程中,根据交叉筋分布位置,对边缘区、筋部及网格区扫描时壁板的多道扫描变形进行实验研究,讨论扫描方式对壁板成形的影响。针对多道扫描过程中非期望变形的累积效应,提出一种扫描纵向加强筋的方法来减小自由端的纵向弯曲程度,并对交叉筋壁板圆柱面弯曲成型的多道扫描流程和扫描策略进行规划,通过成形试验检验策略的有效性。     

约束对板材激光直线扫描成形的影响

板材激光弯曲成形是利用激光成形工件的柔性成形技术。以板材激光单次扫描成形过程为研究对象,对板材激光直线扫描成形过程进行了有限元模拟,分析了有约束和无约束情况下板材的变形行为。     

基于吸收系数修正的硅片激光弯曲模拟与实验

考虑热吸收系数随温度变化的因素,以硅为对象进行了激光弯曲模拟和实验。借助APDL语言编写了激光弯曲成形的仿真程序,对单脉冲作用过程进行模拟,以得到单点脉冲周期内的温度分布;采用NiCr／NiSi合金薄膜热电偶对单脉冲作用过程中的温度分布进行测量,对比上述的温度模拟与测量结果,修正硅材料的激光综合吸收系数为0．82。采用有限元分析软件实现了硅片的脉冲激光弯曲成形的仿真和模拟,并对硅片多次连续扫描的弯曲模拟与弯曲实验进行对比,误差仅为0．1°,验证了仿真程序的有效性,为硅片的激光弯曲成形提供了理论与实验依据。     

金属层合板激光圆弧扫描弯曲成形试验研究

采用激光圆弧扫描弯曲策略,针对矩形层合板主要分析激光功率P、离焦量H、激光扫描速度v以及层合板厚度h对层合板弯曲角度及曲面变形量的变化规律及其影响作用。研究结果表明:激光功率P增大,层合板弯曲角度及曲面变形量随之增大;离焦量H、激光扫描速度v以及层合板厚度h增大,层合板弯曲角度及曲面变形量随之减小;通过激光圆弧扫描弯曲,层合板呈显著三维曲面特征,激光圆弧扫描弯曲成形时层合板长度方向中线处弯曲角度小于层合板两侧边线弯曲角度,且激光扫描线处曲面变形量最大。基于矩形层合板曲面变形特征,为实现圆顶形激光弯曲三维曲面成形,最终利用圆形层合板,采用激光径向+轴向扫描策略弯曲成形圆顶形结构,其最外侧圆周测量线z向最大位移增量达到2. 23 mm。     

Effect of heating paths on strain distribution of plate in laser forming

In laser forming, a desired shape for a metal plate can be obtained by controlling a laser scan path and process parameters. The distance planned between parallel scan paths is larger in current laser path planning in order to avoid interference between them, and thus a continuous strain field cannot be formed. In addition, crossed heating lines are also adopted for forming complicated parts. The effects of the parallel and crossed scanning paths on the deformation field were investigated in this paper. The results show that for parallel heating lines, plastic strain fields produced by adjacent scans do not affect each other when the path spacing is greater than the laser spot diameter, but the plastic strain fields produced by the adjacent scans affect each other when the paths spacing is less than the laser spot diameter. A desirable continuous plastic strain field can be achieved by choosing appropriate path spacing and process parameters. For the crossed heating lines, the plastic strain field is different when adopting vertical and diagonal crossings. The influence between the different heating lines must be considered for high-precision laser forming.     

An experimental investigation on passive water cooling in laser forming process

The effect of passive water cooling in laser forming of thin sheets made of AISI 304 stainless steel is experimentally investigated. Indeed, since each laser scan can produce only small bending angles, multiple laser scans are required to produce a given deformation with a significant increase of production time due to cooling between consecutive scans. Therefore, passive water cooling is tested to verify its influence on minimum time between consecutive scans (cooling time), bending angle, and surface quality. A parametric approach is involved in the investigation and main process parameters are changed among the experiments by varying laser scanning speed, laser beam power, sheet thickness, and cooling media among several levels. It was discovered that the employment of passive water cooling in laser forming of thin sheets would be beneficial since the capability to dramatically reduce the cooling time and oxidation of both irradiated and cooled surfaces. In addition, the bending angle is only marginally affected by employment of water cooling. The effect of water cooling on stress and deformations are discussed by developing a numerical model based on finite element model.     

激光板料成形技术的研究及应用

金属板料激光成形技术是近年来出现的一种先进柔性加工技术.分别介绍了激光热应力成形、激光冲击成形(LSF)和激光喷丸成形(LPF)的成形机理,分析了成形的主要影响因素.影响这三种激光成形方式的因素主要有:激光参数、扫描轨迹、材料性质、板料几何参数和约束边界条件等.分别从机理、工艺参数、成形工艺等方面分析了这三种板料激光成形的技术特点.最后,对这三种激光板料成形技术的应用前景进行了展望,并指出激光板料成形技术在成形的精确控制及成形复杂件方面存在的一些尚待解决的关键问题.     

Investigation of laser and process parameters for Selective Laser Erosion

The process of Selective Laser Erosion (SLE) was investigated to study the effects of different process and laser parameters on the process outputs such as surface quality and erosion rate. The SLE process is a direct method to remove material in a layer-by-layer fashion due to high energy densities provided by the laser beam. In addition to its direct use as a subtractive manufacturing method, SLE may be used in combination with layer-additive techniques such as Selective Laser Melting (SLM). Such combination mainly makes sense when both processes can be performed with the same laser. However, one of the major problems involved in SLE process is the high number of the laser and process parameters (laser power, pulse frequency, scan speed, scan spacing, ambient atmosphere, etc.) and the complexity of the relations between them which has not yet been investigated completely.This paper presents an overview of the laser erosion process with nano-second Nd:YAG laser pulses and the results of several single-factor experiments that were carried out to determine the influence of the major parameters on the depth of erosion per layer and surface roughness. Additionally, the relations between the parameters are studied to investigate the interactions between them. The results from single-factor experiments showed that some relations were highly governed by the power intensity of the laser beam and also that cross interactions between the parameters play an important role on the output characteristics. The paper explains how multiple parameters (spot size, pulse frequency, scan speed, scan spacing) can be combined to define two indirectly controlled geometrical parameters, namely the scan and pulse overlap factors. Those two parameters allow calculating the number of hits of the laser beam on a same location on the workpiece possible which is the first step in physical modeling the topography of the surface left behind.     

激光钎焊多层金刚石磨粒Ni-Cr合金成形工艺研究

为实现多层金刚石磨粒逐层激光钎焊成形,从单道扫描到单层扫描,再到多层扫描,系统研究了镍铬合金与金刚石磨粒的多层激光钎焊工艺。通过提取钎焊道与层的截面成形特征参量,对钎焊层截面成形质量进行参数化评价,并结合钎焊层表面形态,对钎焊层综合成形特性进行评价和讨论,研究了工艺参数对钎焊成形的影响。研究结果表明：激光功率与扫描速度是影响钎焊成形的重要因素,不仅影响着合金粉末的熔合程度、熔池宽度,还影响金刚石的分散状态和钎料对金刚石的浸润包裹性,最终影响钎焊层的平整性。当道与道之间的搭接率为30%~40%时,钎焊成形质量较好。在采用逆向扫描策略,扫描道数为10、固定激光功率为700 W、扫描速度为15 mm/s、光斑直径为1.5 mm、搭接率为30%的条件下,实现了多层磨粒的激光逐层钎焊成形,钎料对金刚石浸润包裹充分,钎焊层中间区域平整连续,整体成形质量好。     

Experimental analysis and computer simulation of a methodology for laser focusing in the solar cell characterization by laser beam induced current

This paper presents a quick methodology for focusing a laser beam on a photoactive surface based on performing a single line scan while simultaneously modifying the laser's position over the surface and the distance between the focusing lens and the active surface. The methodology was tested using the computer simulation technique. Several configurations were computer simulated by programming different experimental situations to discover the situations in which this focusing methodology would provide optimum results. The conclusions obtained from computer simulation methodology were checked by means of experimental tests using several solar cells, such as a thin-film amorphous silicon solar cell, a monocrystalline silicon solar cell, and a polycrystalline silicon solar cell. From the tests performed, we concluded that optimum focusing is achieved in systems in which the laser beam induced current signal generated by the photoactive surface has no large heterogeneities (e.g., fingers or grain boundaries), artefacts, or defects. Thus, the best results are achieved in systems where the surface of the photovoltaic device has a certain degree of homogeneity.     

激光工艺参数对改善编织摩擦材料性能的研究

利用激光扫描编织摩擦材料能明显提高其摩擦性能。采用正交试验设计的方法优化激光工艺参数,以激光电流、扫描速度、离焦量和扫描轨迹为试验因素。试验结果表明,影响编织摩擦材料的摩擦性能最主要因素是温度,激光扫描编织摩擦材料的最佳试验参数:激光电流为13.5 A、扫描速度为700 mm/m in、离焦量为2 mm、扫描轨迹是间距为0.5 mm的矩形波。揭示了激光扫描后编织摩擦材料热衰退机理。     

基于神经网络的激光熔覆高度预测

激光成形过程中,对熔覆高度进行实时检测,从而实现熔覆高度闭环控制是成形高质量零件的保证.激光成形过程是一个多参数耦合的非线性过程,大量激光参数对成形熔覆表面质量具有重要影响.在分析激光参数对熔覆高度影响的基础上,建立利用激光工艺参数预测熔覆高度的误差反向传播(Back propagation,BP)神经网络模型,完成了网络算法设计.通过激光成形试验采集样本,利用训练样本对所建立的网络进行训练,完成网络输入输出高度映射关系,并利用测试样本对所训练的网络进行检验.仿真试验表明,神经网络熔覆高度预测模型具有很高的精度,验证了该预测模型在理论和实践上的可行性与有效性.神经网络熔覆高度预测模型为实现激光加工过程熔覆高度实时预测与闭环控制打下基础,对提高成形产品质量具有重要意义.     

Scan pattern, stress and mechanical strength of laser directly sintered ceramics

A finite element model was developed to simulate the influence of laser scan patterns (laser jump patterns, ratio of length to width and laser scan angle) on the temperature and stress distributions in the process of laser direct sintering ceramics. The effects of laser scan patterns on the stresses in the laser directly sintered ceramic samples were investigated by simulation. Different ceramic samples were prepared by the laser sintering process for the four-point bending strength measurement. The simulation results consist with the experimental ones. The results in the present research can be used to optimize process route for the laser direct sintering process and provide a guidance for selecting the laser processes parameters for high mechanical strength ceramic components.