计算机模拟双折射滤光片抑制绿激光器噪声

结合NdYVO4激光器自身的特点及双折射滤光片的选波长作用,提出以控制晶体的厚度及光轴的夹角来实现单模振荡.经计算机模拟,分析其滤波效果,证明用双折射滤光片解决"绿光问题"是可行的.YVO4和KTP晶体的厚度分别为d1=0.532mm,d2=4.457mm;调谐角分别为13.3°、27.0°.     

计算机模拟双折射滤光片抑制绿激光器噪声

结合Nd:YVO4激光器自身的特点及双折射滤光片的选波长作用,提出以控制晶体的厚度及光轴的夹角来实现单模振荡.经计算机模拟,分析其滤波效果,证明用双折射滤光片解决"绿光问题"是可行的.YVO4和KTP晶体的厚度分别为d1=0.532mm,d2=4.457mm;调谐角分别为13.3°、27.0°.     

高精度双折射晶体定轴测厚仪

一、前言为研制透过带为0.12～0.15(?)窄带双折射滤光器,要求双折射晶片的光程差的偏差小于1/200波长,晶体光轴定向误差小于2′。而以往用常规仪器测定,厚度偏差只能达到1/50波长,定向误差约5′。为此,我们研制了高精度双折射晶体定轴测厚仪。本仪器用来测量晶体厚度、晶轴的方位角及晶体材料的双折射率(μ值)。测厚精度达1/(1000)波长,定轴精度优于1′,μ值可定准到5×10~(-5),测试数据稳定可靠。二、仪器的测量原理及精度1.晶体测厚原理及精度在两平行或正交的偏振片之间,放一片双折射晶体b(图1),其晶轴躺在通光面上,且与偏振轴成45°夹角。光束通过双折射晶体后,o 光和e 光之间有光程差σ为:     

巧改车床卡爪结构

图1所示工件为石油化工设备用缠绕式密封垫骨架。其材料为Q235-A冷轧钢板,厚度3mm,外径d=φ20～φ300mm,宽度B=6～20mm,槽宽2mm,两侧面夹角60°±2°(有时外圆需加工成槽形,要求与内槽相同)。     

介绍两种延长冲裁模具寿命的方法

1.减小凹模刃口高度h值在冲裁模中,有各种不同类型的刃口形状,但常用的形状如图所示。这种模具通常取α=2°～3°,刃口高度h值为几毫米。苏联研究设计和目前采用的同样刃口形状的模具,其寿命就有显著的提高。其主要特点是:刃口高度h=0.1mm,当被冲压材料厚度在1.5mm以下时,α=0.5°;当材料厚度超过1.5mm时,则α=0.75°,且冲头进入凹模的深度不超过0.1～0.2mm。此外模具的间隙为常用值的1/2。据说按     

高温合金曲面上钻斜孔

我厂有一个高温合金零件(材料GH140固溶处理),要在曲而上钻斜孔(图1),孔径4.5mm,孔深6～7mm。开始加工时,采用高钒高速钢钻头,结构如图2,其中:L=120mm,L_切=60mm,k=0.25 d,d=4.5mm,钻头锋角2φ=140°,外缘后角α_p=16°,螺旋角ω=33°。钻头     

过滤机齿轮断裂的原因及修复

一、齿轮参数及使用情况一对用在转鼓过滤机上的齿轮,大齿轮Z_1=198,m=10,α=20°,顶圆直径φ=2000,齿长130mm;小齿轮Z_2=18,m=10,α=20°,顶圆直径φ=200,齿长140mm.1971年3月投运,1994年4月发现小齿轮连续3个齿齐根折断,大齿轮虽未断齿,但有4处断裂,如图1所示.     

精刨代替刮研的经验

(一)刀具的准备精鉋平面的鉋刀如图1,它的前角γ=10°,倒稜宽度2公厘,倒稜前角γφ=6°。后角α=10°,在2公厘宽处研磨成α=5°。主偏角=3°,副偏角_1=10°。刀刃斜角λ=10 °,刀尖半径R=1～2公厘。平刃宽度与全部刃宽度的比例是2∶3。精鉋立面及斜面的鉋刀的几何形状是:前角γ=7°～8°,倒稜宽2公厘、前角3°～4°,后角α=10°,宽2公厘处研磨成     

凸角留磨齿轮滚刀的设计及其在电力机车牵引齿轮加工中的应用

1　问题的提出韶山 6B型电力机车 (SS6B)主动齿轮和从动齿轮的基本参数为mn=13,z1=17,z2 =74 ,α =2 2 5° ,β =0° ;主动齿轮 3齿公法线长度W3=10 1 939- 0 2 8- 0 4 0mm ,分度圆直径df1=2 2 1mm ,齿顶圆直径da1=2 5 4 37mm ,齿根圆直径di1=194 31mm ;从动齿轮10齿公法线长度W10 =382 789- 0 2 4 - 0 35mm ,分度圆直径df2 =96 2mm ,齿顶圆直径da2 =10 0 0 5 94mm ,齿根圆直径di2 =94 0mm ,中心距a =6 0 2 + 0 2 0 mm ,齿轮根部圆弧半径R =4～ 5mm。主动齿轮材料为2 0CrMnMoA ,渗碳淬火 ,齿面硬度HRC >5 7,从动…     

机夹切断刀

一、刀具特点:1.刀片可采用切削力夹固或弹性一紧双固,装卸调整方便(见图1、图2);2.刀片基面选用120°定位,刀垫、压块装夹在刀杆20°槽内,定位准确,夹紧牢固;3.刀具前角γ=10°、后角a=4°、副后角a_1=2°、     

YVO4-Nd:YVO4复合晶体热效应研究

在全固态激光器中使用了复合结构的激光晶体,通过端面泵浦复合晶体工作特点分析,提出了矩形截面复合晶体热分析模型。在热模型中,考虑了复合晶体具有轴向加热、周边恒温,耦合后的泵浦光束具有高斯分布的特点。利用热传导方程,得出了YVO₄-Nd:YVO₄复合晶体内部温度场及端面热形变的一般解析表达式。研究结果表明,若用输出功率为20 W的激光二极管端面泵浦YVO₄-Nd:YVO₄复合晶体(其中复合晶体中YVO₄晶体长为2 mm,Nd:YVO₄晶体长为6 mm,钕离子掺杂质量分数为0.5%),泵浦光斑为0.2 mm时,复合晶体内最大温升为324.5 ℃,泵浦端面具有3.61 mm的热形变量。在相同泵浦条件下,采用复合晶体替代Nd:YVO₄晶体,可将其最大温升降低23.4%,这对于消弱激光晶体热效应的影响,解决激光二极管端面泵浦激光晶体引起的非均匀温升以及热折裂问题,提高激光器性能有着重要的意义。     

外腔型YVO4拉曼激光器

采用提拉法生长了高光学质量的YVO4晶体,最大尺寸为28mm×40mm,重126g。以脉冲宽度为40皮秒的Nd:YAG锁模激光器作为激发源,研究了YVO4晶体在外置谐振腔条件下的拉曼输出特性：多波长输出的总转换效率达到51.4%,最大输出能量2.21mJ;1175nm一级斯托克斯拉曼输出的最高转换效率为32%,最大输出能量0.57mJ;1313nm二级斯托克斯拉曼输出的最高转换效率为12.3%,最大输出能量0.36mJ。     

激光分布对抽运Nd:YVO4晶体热效应的影响

以解析各向异性分析理论为基础,研究矩形横截面Nd:YVO4激光晶体受到超高斯分布LD端面抽运时,激光晶体温度场分布和晶体抽运面热形变分布。通过激光晶体工作特点分析,考虑了激光分布和激光光束半径变化,建立了符合激光晶体工作状态的热模型。利用各向异性介质热传导方程的一种新求解方法,得出了矩形截面Nd:YVO4晶体的温度场、端面热形变场的通解表达式。研究结果表明：当使用输出功率为15W半导体激光器（超高斯阶次为1）端面中心入射Nd:YVO4晶体（晶体掺钕离子质量分数为0.5%）时,在抽运端面中心获得243.8C最高温升和1.99m最大热形变量,与实验结果一致。这种方法可以应用到其它激光晶体热问题研究中,为有效解决激光系统热问题提供了理论依据。     

基于复合正交试验的犁削—挤压参数优化设计

基于复合正交试验方法,研究了单齿犁削—挤压过程的参数优化,为热管内表面吸热芯多齿犁削—挤压过程的优化设计提供了参考依据。对单齿犁削—挤压过程中影响翅形貌的多种因素及水平值进行分组,对两组因素的主次关系和优水平进行了试验研究。试验结果表明,得到的刀具参数优化值为β=30°,α=-8°,h=0·6mm,H=4mm,θ=45°,η=35°;工艺参数优化值为αp=0·24mm,V=113mm/s。     

Shape optimization of the cone body for the improved performance of the V-cone flowmeter: A numerical study

The present study has been carried out to optimize the shape of the cone body by providing a curved surface (the radius of curvature (R)) at the base of the cone element for improving the performance of the V-cone flowmeter using CFD. Radii of curvature of 20 mm (hemispherical, R/d = 0.5), 22 mm (R/d = 0.55) 25 mm (R/d = 0.625) and 27.62 mm (R/d = 0.6905) are taken in order to gradually reduce the arc length keeping the chord length constant. In addition a semi-elliptical based cone with 20 mm semi-major axis and10 mm semi-minor axis has also been investigated in the present study. The centre of the spheres and ellipse lie on the axis either in the frustum or cylindrical part of the cone. The equivalent diameter ratio (β) has been taken as 0.6 while three different fore-vertex angles (φ) namely 60°, 75° and 90° have been investigated. The Reynolds number has been varied in the range of 1 × 10³ to 1 × 10⁶. The results have been compared with the slant surface based cone. It is seen that introduction of a curved surface at the cone base has profound effect on the coefficient of discharge of the V-cone flowmeter. The coefficient of discharge is dependent on Reynolds number for the flowmeter with hemispherical and semi-elliptical based cone element. The coefficient of discharge is seen to be a weak function of Reynolds number for Re = 4000 and beyond for the other three curvatures. The cone flowmeter with a curved base cone of R/d equals to 0.55 has higher coefficient of discharge and smaller standard deviation compared to a device with an aft vertex cone.     

结构和材料参数对旋转轴唇形密封可靠性影响

基于流量因子统计学方法建立油封密封区域的混合润滑数值模型,利用有限元软件进行求解,分析结构和材料参数对油封密封可靠性的影响规律。结果表明：在研究的参数范围内,静态密封可靠性随腰厚、腰长、空气侧唇角、弹簧的弹性模量、橡胶硬度的增加而提高,随过盈量、油侧角和理论接触宽度的增大而减小;当过盈量为0.4~0.55 mmm、理论接触宽度为0.3~0.6 mm、油侧角为35°~50°、空气侧唇角为15°~30°、腰厚为1.0~1.3 mm、腰长为0.9~1.2 mm、弹簧模量为1 175~1 250 MPa,橡胶硬度为70HA~85HA时有利于油封可靠性的提高,且在此取值范围内,动态密封可靠性随过盈量、油侧唇角、橡胶材料硬度、腰厚和理论接触宽度的增加而增大,随弹簧弹性模量、腰长、空气侧唇角的增大而减小。     

Thermodynamic Behavior Research Analysis of Twin-roll Casting Lead Alloy Strip Process

The thermodynamic behavior of twin-roll casting(TRC) lead alloy strip process directly affects the forming of the lead strip, the quality of the lead strip and the production efficiency. However, there is little research on the thermodynamics of lead alloy strip at home and abroad. The TRC lead process is studied in four parameters: the pouring temperature of molten lead,the depth of molten pool, the roll casting speed, and the rolling thickness of continuous casting. Firstly, the thermodynamic model for TRC lead process is built.Secondly, the thermodynamic behavior of the TRC process is simulated with the use of Fluent. Through the thermodynamics research and analysis, the process parameters of cast rolling lead strip can be obtained: the pouring temperature of molten lead: 360–400 °C, the depth of molten pool: 250–300 mm, the roll casting speed: 2.5–3 m/min, the rolling thickness: 8–9 mm.Based on the above process parameters, the optimal parameters(the pouring temperature of molten lead:375–390 °C, the depth of molten pool: 285–300 mm, the roll casting speed: 2.75–3 m/min, the rolling thickness:8.5–9 mm) can be gained with the use of the orthogonal experiment. Finally, the engineering test of TRC lead alloy strip is carried out and the test proves the thermodynamic model is scientific, necessary and correct. In this paper, a detailed study on the thermodynamic behavior of lead alloy strip is carried out and the process parameters of lead strip forming are obtained through the research, which provide an effective theoretical guide for TRC lead alloy strip process.     

端面泵浦热传导各向异性激光棒温场特性研究

了解决LD端面泵浦热传导各向异性激光介质产生的热效应问题,建立了端面绝热、侧面冷却的Nd:YVO4晶体热模型。考虑到Nd:YVO4为热传导各向异性材料,而光纤耦合LD输出光束有着超高斯分布的特点,利用特征函数法和常数变异法得到了超高斯光束端面泵浦热传导各向异性激光介质温度场的一般解析表达式。并定量分析了超高斯泵浦光阶次、泵浦功率以及光斑尺寸对于Nd:YVO4晶体温度场的影响。新的各向异性介质热传导方程求解方法具有计算量小、精度高等特点。研究结果表明：若LD输出功率为30W,光学聚焦耦合器的传输效率为82%时,4阶超高斯光束端面泵浦掺钕离子质量分数为0.5%的Nd:YVO4晶体,泵浦面获得528.95C的最大温升。所得结果可用于LD端面泵浦热传导各向异性激光介质全固态激光器热稳腔的设计之中,对于提高激光器性能具有了理论指导作用。     

Springback evaluation in hot v-bending of Ti-6Al-4V alloy sheets

In this paper, v-bending of Ti-6Al-4V alloy sheet was conducted from room temperature to 850 °C at a fixed velocity of 0.1 mm/s. Punches with punch radii of 1, 2, 4, and 6 mm, as well as several holding times were used. V-bending and springback behaviors were numerically analyzed with an isotropic hardening model that considered rate-dependent effects. Using a punch radius of 1 mm always leads to negative springback in the temperature range of 550–750 °C. This behavior occurs because an arc formed in the transition side near the end of bending and flattened at the end of bending, leading to an internal bending moment which causes specimen to bow inward after unloading. At a punch radius of 2 mm, positive springback occurs at 300–650 °C, while negative springback occurs at 700–750 °C. At punch radii of 4 and 6 mm, positive springback occurs at 600–750 °C, and the angle decreases as temperature increases. At 850 °C, negative springback occurs at a punch radius of 4 mm due to the decrease in yield strength. At a punch radius of 1 mm, cracking occurs at room temperature and 500 °C, while at 2 mm, it occurs only at room temperature. This discrepancy is ascribed to the greater plastic deformation caused by the smaller punch. As holding time increases, the shape of the deformed specimen more closely matches the desired shape.     

Numerical and experimental investigation of wind loadings on vertical axis wind turbine blade deflection

This work focuses on experimental and numerical investigation of the deflection on VAWT blade surface against the high measured wind speeds that were simulated in FLUENT to obtain the corresponding static forces. The effect of forces, blade setting angle and thickness to chord ratio along with their combined effects on deflection were assessed experimentally and numerically. Three airfoils of gradually increasing thickness to chord ratio, NACA 0015, 0021 and 4412, were selected along with three levels of forces and tested at 5°, 10° and 15° of blade setting angle. A 3³ factorial experimental design was used to perform experiments and Analysis of variance (ANOVA) confirmed that individual effects of force and thickness to chord ratio were the most significant factors while blade setting angle had lesser significance on deflected values. However, interactive effects of these parameters were significant. Minimum deflections were observed in the range of 0.25-0.28 mm on NACA 0021 at 3 kg force in combination with all blade setting angles. Maximum observed value of defection was 1 mm, which occurred at 9 kg force at 5°, 10° and 15° of blade setting angle on NACA 0015 and 4412 airfoil shapes. The results ensure that the blade structure remains stable at 9 kg which corresponds to 20 m/s wind speed without affecting the performance. The deflections obtained from Finite element method were compared with experimental results and found in good agreement with each other.