3-D transient numerical simulation on the process of laser cladding by powder feeding

A 3-D transient mathematical model for laser cladding by powder feeding was developed to examine the macroscopic heat and momentum transport during the process, based on which a novel method for determining the configuration and thickness of cladding layer was presented. By using Lambert-Beer theorem and Mie‘s theory, the interaction between powder stream and laser beam was treated to evoke their subtle effects on heat transfer and fluid flow in laser molten pool. The numerical study was performed in a co-ordinate system moving with the laser at a constant scanning speed. A fixed grid enthalpy-porosity approach was used,which predicted the evolutionary development of the laser molten pool. The commercial software PHOENICS, to which several modules were appended, was used to accomplish the simulation. The results obtained by the simulation were coincident with those measured in experiment basically.     

激光淬火技术在发动机大修中的应用

作者介绍了激光淬火提高气缸套耐磨性和使用寿命以及提高曲轴抗磨损、抗疲劳性的强化机理、激光处理工艺及方式、方法 ,讨论了激光淬火强化效果的影响 ,总结并分析了强化效果。结果表明 :在优化的工艺条件下 ,激光淬火不仅提高了气缸套和曲轴的耐磨性和抗疲劳性 ,而且还提高了其使用寿命 ,在发动机大修中应该得到大力提倡     

Effects of Powder Feeding Rate on Interaction between Laser Beam and Powder Streamin Laser Cladding Process

A theoretical model was presented to calculate the laser intensity distribution and the particle temperatures at different sites of the workpiece in the laser cladding process By using this model, the effects of the powder feeding rate on the laser intensity distribution and the particle temperatures were inrestigated ,the caleuluted results under the condition of different injection angles were also plotted it is shout that with increasing the injection angle,the laser inuensity distributwons are similar but the peak ralue of the laser intensity decreases simdlaneously the peak ralue of the particle tenperature increases and the disribution of the particle temperatures gets central symmetrical gradually.these tests reslts should be considered in model of laser cladding due to their sub the effects on the dynamic processes in laser molten pool.     

新型热电材料及其新应用

热电材料，由于在清洁能源、光电子探测等诸多方面有巨大的应用前景，因而受到科学上和技术上的广泛关注．最新的理论进展和若干新材料的发现，为人们提供了新的应用机会．一类新材料就是基于强关联电子系统，典型例子是过渡族金属氧化物，这类材料以前从热电材料的角度并未受到重视．我们将讨论几点最近的进展，着重讨论生长在倾斜切割衬底上薄膜的新的应用．这种情况下热电电压的产生是基于各向异性的塞贝克效应．当光辐射照射到薄膜表面时，薄膜上下表面的温差引起横向的电势差，从而可用于光、热辐射的探测．我们论证：这类探测器有很具特色的优点，宽的光谱响应，快的时间响应，同时不须施加偏压或偏流，因而十分节能．我们还讨论了几种典型材料的性能．     

粗糙度与激光强度分布对光船聚焦性能的影响

激光束聚焦性能研究是激光推进技术研究中的一个重要内容。根据实验装置的形状和激光强度分布,建立了计算模型,编写了计算程序。用该程序可通过计算空间某点的激光能流密度和某个区域的能流密度分布来确定点火线的形状和点火区域的大小;研究喷管内壁的表面粗糙度和入射激光束的强度分布对聚焦性能的影响。为进一步研究激光支持等离子体流场特性和脉冲激光推进性能等提供重要的理论依据。     

激光莫尔传感器在精密定位中的应用

应用激光莫尔信号传感器设计了一套精密定位装置 ,可实现高精度位置检测及精密自动定位 ;系统采用的激光补偿技术及差动光栅技术 ,极大地提高了位置检测信号的灵敏度与定位精度 .实验结果表明 ,精密定位装置可获得± 0 1μm的定位精度 ,对集成电路制造技术等精密加工工程领域具有重要的实用价值     

激光电视全息技术及其在无损检测中的应用

激光电视全息技术是一种测量物体表面微小变形的非接触式测量技术.与常规检测方法相比,它具有高精度、全场、实时测量等特点,有着重要的理论研究和实用价值,是当前无损检测领域研究热点之一.本文介绍了激光电视全息技术的基本原理和特点、国内外在无损检测领域的应用成果和最新研究进展,并探讨了未来的发展趋势.     

激光衍射法测试表面改性超细TiO_2粉体粒度的分散方法研究

探讨了用激光衍射法测试经PEG(400)表面改性的超细TiO_2粉体粒度的过程中,不同分散介质对经表面改性的超细TiO_2粉体粒度测试结果的影响。实验结果表明,用乙醇和六偏磷酸钠溶液(0.1g/ml)为混合分散介质(体积比1:1)时能最佳分散样品,此时的测试结果也最准确地表征了样品的粒度。     

济钢中板厂提高长度定尺精度实践

为了提高钢板长度定尺精度,精整车间针对长度定尺机进行了局部改造,提出了2#剪板机横移激光划线的改造要求并对2#剪实施了温度补偿自动控制,使钢板长度尺寸精度平均提高8～12mm的精度波动范围,使济钢中板厂的成材率和双向定尺率得到有效提高。     

采用激光熔敷Ni—WC技术修复破碎辊的工艺研究

熔敷Ni—WC技术采用自重送粉法，在ZG35CrMo基体表面用圆光斑激光熔敷Ni—WC复合涂层，其过程中要严格控制激光功率、扫描速度、送粉量、光斑进给量及基材的温度。这种方法可有效地减少表面裂纹、气孔，并能降低基体材料对熔敷材料的稀释，有效地提高熔敷层的硬度和耐磨性，延长破碎辊的使用寿命。