A Study on Super Speed Forming of Metal Sheet by Laser Shock Waves

Metal sheet plastic deformation or forming is gener at ed through a mechanical pressure or a thermal variation. These pressure variatio ns or thermal variations can be created by a variety of means such as press form ing, hydroforming, imploding detonation and so on. According to the magnitude of the strain rates all these forming methods can be divided into quasi-static fo rming and dynamical forming. Up to now there are no reports of forming methods w ith the strain rates above 10 5sec -1, even though the exploding forming. In this article, we work on a dynamic super-speed forming method driven by lase r shock waves and advanced a novel concept of laser shock forming. The initial o bservation of the laser shock forming is done through a bugle testing with speci mens of SUS430 sheet metal, using a neodymium-glass laser of pulse energy 10J～ 3 0J and duration of 20 ns (FWHM). The investigation revealed that the plastic de formation during the laser shock forming is characterized as ultrahigh strain ra te up to 10 7sec -1. We indicate that plastic deformation increases nonlin early when the energy density of the laser varies. By investigating the hardness and residual stress of the surfaces, we conclude that laser shock forming is a combination technique of laser shock strengthening and metal forming for introdu cing a strain harden and a compressive residual stress on the surface of the wor k-piece, and the treated surface by laser shock forming has good properties in fatigue and corrosion resistance. This technique can achieve forming wit h or without mould.

Geometrical, microstructural and mechanical characterization of pulse laser welded thin sheet 5052-H32 aluminium alloy for aerospace applications

Pulse laser welding of 0.6 mm-thick AA5052-H32 was performed to determine the optimum set of parameters including laser pulse current,pulse frequency and pulse duration that meets the AWS D17.1 specifications for aerospace industry.The microstructure and mechanical properties of the weldments were also investigated.Relationships between the parameters and weld bead geometry were found.High quality weld joints without solidification crack that met AWS D17.1 requirements were obtained at(I)high pulse energy(25 J)and high average peak power(4.2 kW)and(II)low pulse energy(17.6 J)and low average peak power(2.8 kW).The weld joint formed at lower heat energy input exhibited finer dendritic grain structure.Mg vapourisation and hard phase compound(Al0.5Fe3Si0.5)formation decreased in the weld joint formed at lower heat energy input.Consequently,the tensile strength of the weldment formed at lower heat energy input(168 MPa)is by a factor of 1.15 higher but showed^29%decrease in hardness(111 HV0.1)at the joint when being compared with the weldment formed at higher heat energy input.Appropriate parameters selection is critical to obtaining 0.6 mm-thick AA5052-H32 pulse laser weld joints that meet AWS D17.1 requirements for aircraft structures.

Laser brazing with filler wire for galvanized steel sheets

The process properties and interface behavior of CO_2 laser brazing with automatic wire feed for galvanized steel sheets were investigated, in which the brazing filler metal was CuSi3 and no flux was used. As to the appearance quality of the brazing seams, the roles of the processing parameters, such as brazing speed, wire feeding rate, inclination and feeding direction of the wire, laser power, spot diameter and heating position, were assessed. The further investigation indicates that the behavior of the active elements Si, Mn and Zn are significantly influenced by energy input. At the interface, the microstructure of the base metal was composed of columnar crystals and the acicular α solid solution was found on the filler metal side.

Microstructure characteristics and liquation behavior of fiber laser welded joints of Mg-5Zn-1Mn-0.6Sn alloy sheets

Fine-grained Mg?5Zn?1Mn?0.6Sn alloy sheets of2mm in thickness were welded by fiber laser welding.The appearanceand microstructures of the welding joints and liquation behaviors in the partially melted zone(PMZ)were investigated.The resultsshow that,with the lower welding power and higher welding speed,the width and depth of the joints decrease.Moreover,some poresare detected at a very high welding speed.There are two kinds of liquation phenomena in the PMZ.One is the liquation networkalong grain boundaries associated with the liquation of substrate and segregation-induced liquation,the other is the molten poolinvolved with the liquation of the residual second phases at the boundaries.However,the liquation of substrate and thesegregation-induced liquation are the main liquation mechanism in the PMZ.

Effect of Al coating conditions on laser weldability of Al coated steel sheet

Al coated steel sheets with excellent heat resistance,thermal reflection,and corrosion resistance are widely used in various applications.The laser weldability of the Al coated steel sheet for full penetration welding was reported.The phenomenon caused by intermixed aluminum and behavior of aluminum in the weld were investigated.Al coated steel sheets that have various thickness and coating mass were prepared for laser welding.The effects of parameters such as welding conditions and Al coating conditions were investigated.Al content mixed in the weld after laser welding was evaluated,and then a correlation between the mixed Al and mechanical properties was investigated.The results show that the Al-rich zones which have Fe-Al intermetallic compounds are found in the weld.The intermetallic compounds cause the decreased strength of the weld.

Influence of process parameters on drilling characteristics of Al 1050 sheet with thickness of 0.2 mm using pulsed Nd:YAG laser

The object of this work is to investigate the influence of process parameters on drilling characteristics of an Al 1050 sheet with a thickness of 0.2 mm using a pulsed Nd:YAG laser through numerical analyses and experiments. By comparing the numerical analyses with the experiments, a proper numerical model was obtained. From the results of the numerical analyses and the experiments, the effects of process parameters on entrance diameters of drilled holes, shapes of the holes, taper angles of the holes and temperature distributions in the vicinity of the holes were examined quantitatively. In addition, the optimal drilling condition was estimated to improve the quality of the drilled holes.

Simulation and prediction in laser bending of silicon sheet

The laser bending of single-crystal silicon sheet （0.2 mm in thickness） was investigated with JK701 Nd：YAG laser. The models were developed to describe the beam characteristics of pulsed laser. In order to simulate the process of laser bending, the FEM software ANSYS was used to predict the heat temperature and stress-strain fields. The periodic transformation of temperature field and stress-strain distribution was analyzed during pulsed laser scanning silicon sheet. The results indicate that the mechanism of pulsed laser bending silicon is a hybrid mechanism in silicon bending, rather than a simple mechanism of TGM or BM. This work also gets silicon sheet bent after scanning 6 times with pulsed laser, and its bending angle is up to 6.5°. The simulation and prediction results reach well agreement with the verifying experiments.

AN EXPERIMENTAL STUDY OF CO_2 LASER CUTTING OF METALLIC COATED SHEET STEELS

An experimental investigation is outlined for the CO 2 laser cutting process of metallic coated sheet steels, GALVABOND. It shows that by proper control of the cutting parameters, good quality cuts are possible at high cutting rate. Visual examination indicates that when increasing the cutting rate to as high as 5000 mm/min (about 100 times that suggested previously), kerfs of better quality can be achieved. Some kerf characteristics such as the width, heat affected zone and dross in terms of the process parameters are also discussed. A statistical analysis has arrived at a recommendatio on the optimum cutting parameters forprocessing GALVABOND.

Influence of cutting parameters on surface characteristics of cut section in cutting of Inconel 718 sheet using CW Nd:YAG laser

Recently, laser cutting technologies begin to use for manufacturing mechanical parts of Inconel super-alloy sheet due to difficulties of machining of the Inconel material as a results of its extremely tough nature. The objective of this work is to investigate the influence of cutting parameters on surface characteristics of the cut section in the cutting of Inconel 718 super-alloy sheet using CW Nd:YAG laser through laser cutting experiments. Normal cutting experiments were performed using a laser cutting system with six-axis controlled automatic robot and auto-tracking system of the focal distance. From the results of the experiments, the effects of the cutting parameters on the surface roughness, the striation formation and the microstructure of the cut section were examined. In addition, an optimal cutting condition, at which the surface roughness is minimized and both the delayed cutting phenomenon and the micro-cracking are not initiated, is estimated to improve both the part quality and the cutting efficiency.

Numerical Investigation of the Effect of Process and Sheet Parameters on Bending Angle in the Laser Bending Process

In this work, the effects of process parameters such as laser output power, beam diameter and scan speed and also sheet thickness on the bending angle have been numerically investigated in the laser bending process. For this purpose, Abaqus software is used for investigating the effect of various process and sheet parameters on the bending angle. The results show that with increasing the laser output power, bending angle is increased. Also, the bending angle is decreased with increasing the beam diameter, scan speed and sheet thickness.

The Effect of Microstructural and Geometric Inhomogeneities Induced by Laser for Forming Strain Analysis on Sheet Metal Formability

A commercially available laser marking system based on diode-pumped Nd:YVO4 laser was used for creating grid patterns for forming strain analysis of a dual-phase steel. The aim was to determine and analyze the influence of laser working parameters on the formability of sheet material by means of an in-depth characterization of this induced microstructural and geometric inhomogeneity. The electrochemical etching served as the reference method without the negative effect of generating inhomogeneity. The formability was evaluated using the cupping test according to Erichsen. While the quantification of geometric inhomogeneity was based on the determination of the notch factor, light microscopy and microhardness measurement were used for the evaluation of microstructural inhomogeneity. Furthermore, on the basis of the results an empirical regression model was established which described in terms of quantity the relationship between the examined factors such as laser power, pulse frequency and scanning speed as well as the command variable and the mark depth. The results showed that microstructural inhomogeneity in the used marking parameters due to their locally very limited formation did not have an appreciable influence on the mechanical properties. In contrast to this, the induced geometric inhomogeneity had a marked influence on the material formability.

基于3 mm厚碳钢薄板激光切割工艺的试验研究

随着制造业的快速发展,激光切割技术作为一种先进的加工方法,在薄板切割领域得到了广泛应用。文章主要研究了3mm厚碳钢薄板的激光切割工艺,通过试验的方法分析了切割速度、辅助气体气压和焦点位置等工艺参数对切割质量的影响。试验结果表明,适当切割速度和辅助气体气压可以提高切割质量和效率,而焦点位置的优化可以进一步改善切割断面的质量。这些发现对于指导实际生产,提高薄板激光切割的工艺水平具有重要意义。

316L不锈钢薄板焊缝成形及力学性能研究

目的减少1 mm厚度316L不锈钢薄板在焊接生产过程中出现的缺陷等问题,并提高不锈钢薄板焊缝成形质量和焊接接头力学性能。方法采用脉冲激光焊接技术实现对厚度1 mm的316L不锈钢薄板的精确焊接,并利用金相显微镜、维氏硬度计、万能拉伸试验机和扫描电镜对焊缝的表面形貌、微观结构、力学性能、断口形貌进行表征分析。结果当激光功率为403 W、输出电流为150 A、焊接速度为150 mm/min、离焦量为−5.525 mm时,焊缝正反面的形貌规则无缺陷。焊缝区内的微观结构主要由δ-铁素体和奥氏体2种晶粒构成,相较于母材及热影响区,焊缝区晶粒尺寸更细小均匀,平均硬度为156HV,表现出更高的硬度特性。焊接接头的抗拉强度和屈服强度均值分别达到643.28 MPa和305.95 MPa,相对于母材的强度分别提高了7%和49%;平均断后伸长率为37.2%,达到原始母材伸长率的55%;断裂呈现韧性断裂的塑性变形和延展性特征。结论优化调整焊接工艺参数后,1 mm厚度316L不锈钢薄板的焊缝成形质量提高,无缺陷且微观组织分布均匀,焊接接头强度显著提高。

微细波纹板激光热应力成形边界效应的抑制方法

激光热应力成形为微细薄板结构的无模制造提供了解决方案,然而其边界效应严重影响成形精度。针对金属薄板激光热应力成形过程中的边界效应,采用振镜式激光,结合有限元模拟和成形试验分析激光工艺参数对边界效应的影响规律。研究了变速度、变方向以及两者耦合的边界效应抑制策略,进而用于微细波纹板成形过程。结果表明,扫描路径上的温度与应力分布不均是造成边界效应的主要原因,薄板成形过程中的热累积主要存在于扫描结束端,激光工艺参数是影响弯曲成形件变形的重要因素;采用变向-变速耦合策略比单方向扫描的相对角度变化减小77.8%,实现了深宽比大于0.75的微细波纹板精密成形。变向-变速耦合策略能够有效抑制微细波纹板激光热应力成形中的边界效应,为高质量微细薄板成形提供参考。

薄板件高精度测量线激光连续扫描路径规划

线激光检测技术以其高精度的特点在复杂零部件检测中获得广泛应用,扫描路径规划结果对三维薄板件检测精度具有重要影响。由于线激光具有连续逐行扫描、单帧数据呈直线分布等特点,基于离散视点的规划方法难以实现被测件的各型面关键特征点的自动覆盖测量。为此,提出一种面向检测精度的多目标优化连续覆盖路径规划算法。首先,综合考虑路径长度、传感器入射角等因素,构建线激光连续扫描路径的多目标优化模型;其次,引入搜索随机树规划策略,通过对不确定度指数的迭代优化实现复杂结构件的全型面上关键特征点覆盖路径规划;最后,结合车门总成扫描案例开展应用验证,并与传统三维覆盖路径规划方法进行对比分析。结果显示所提出方法的测点平均不确定度指数较比较方法有所降低,验证了所提出方法的有效性和可行性。

Development of an ultrathin liquid sheet target for laser ion acceleration at high repetition rates in the kilohertz range

A colliding microjet liquid sheet target system was developed and tested for pairs of round nozzles of 10,11 and 18μm in diameter.The sheet's position stability was found to be better than a few micrometers.Upon interaction with 50 mJ laser pulses,the 18μm jet has a resonance amplitude of 16μm at a repetition rate of 33 Hz,while towards 100 Hz it converges to 10μm for all nozzles.A white-light interferometric system was developed to measure the liquid sheet thickness in the target chamber both in air and in vacuum,with a measurement range of 182 nm±1μm and an accuracy of±3%.The overall shape and 3D shape of the sheet follow the Hasson±Peck model in air.In vacuum versus air,the sheet gradually loses 10%of its thickness,so the thinnest sheet achieved was below 200 nm at a vacuum level of 10±4mbar,and remained stable for several hours of operation.

冷轧薄板激光切割热影响区的深度及性能

为确定激光切割热影响区深度和激光切割热影响区对不同厚度、不同强度冷轧薄板产品力学性能的影响,通过改变激光切割速率的方法,对冷轧薄板产品进行激光切割试验,并对激光切割后热影响区的组织、深度和板材的拉伸性能进行研究。结果表明:热影响区可分为两部分,第一部分为激光切缝边缘的熔化区,第二部分为非熔化区,熔化区主要为马氏体,非熔化区主要为马氏体+贝氏体,激光切割速率越快,冷轧薄板的热影响区深度越小,冷轧薄板的强度越高或厚度越厚,热影响区深度越大;激光切割加工试样比加工中心加工试样的屈服强度和抗拉强度高,断后伸长率低,且随着钢种等级的提高,两者间的差异不断增大。

邮轮薄板激光生产线工艺流程中的变形精度控制分析

针对邮轮薄板激光生产线工艺流程中的钢板预处理矫平阶段、主板拼接阶段、主板自动划线阶段、纵骨装焊阶段、T形梁装配阶段和T形梁焊接阶段,依据不同的变形精度控制要素,对工艺流程中的变形精度控制进行分析,可为后续邮轮薄板分段制造精度策划与设计提供指导性建议。

汽车贯穿式尾灯高度影响因素分析

汽车贯穿式尾灯设计已成为汽车主流设计之一,尾灯高度的大小直接影响车灯造型、尾灯支架结构及尾灯支架的连接工艺,进而影响可制造性及制造成本。文章在介绍汽车贯穿式尾灯的基础上,分析了影响贯穿式尾灯高度的相关因素,讨论了钣金造型设计、尾灯发光区域设计、尾门钣金结构设计、尾门钣金连接工艺等方面对贯穿式尾灯高度的影响,并分析其对整车成本的影响情况,为汽车贯穿式尾灯造型设计提供参考。

STUDY ON REDUCING THE CORE LOSS OF GRAIN ORIENTED SILICON STEEL AND IMPROVING ITS AGING PROPERTY BY LASER NITRIDING TECHNIQUE IN ATMOSPHERIC AMBIENT

CW-CO2 laser nitriding technique was applied to improve the properties （such as aging property and the core loss） of grain oriented silicon steel. The samples were nitrided with regular space. Laser power density and scanning speed were chosen as 7.8×10^5W·cm^-2 and 100mm·min^-1. By some laser irradiation, Fe4N and Fe3N were formed in the nitrided zone. The nitrided samples were annealed at the temperatures ranged from 100 to 90℃. The core loss of some interested samples was tested. The results show that the core loss of the nitrided samples with different thickness of 0.23 and 0.30mm decreased by 14.9% and 9.4% respectively, and the aging property were improved up to 800℃. The mechanism of laser nitriding to improve the properties of grain oriented silicon steel is discussed.