塑料光纤微透镜耦合平头发光二极管

为了有效耦合平头发光二极管(LED),使用机械方法加工了锥球面塑料光纤(POF)微透镜。平头发光二极管由圆头发光二极管打磨掉聚光帽制得,其出光端面与芯片距离小于0.5mm。锥球面塑料光纤微透镜用数控机床加工制得。采用光线追迹法对耦合模型进行了分析。实验优化了锥球面光纤微透镜的参数、锥角、小球半径、工作距离和单端/双端模式,并理论分析了双端锥球面微透镜耦合的实验结果。当双端锥球面光纤微透镜锥角为140°、小球半径为0.15mm时,可带来20.4%的耦合效率增益。所用加工方法有利于微透镜参数优化,具有较好的加工精度和重现性,可以用于制作塑料光纤微透镜。     

四程抽运Yb:YAG薄片激光器

设计了四程抽运的Yb:YAG薄片激光器.选用掺杂原子数分数为10%,几何尺寸为Ф10 mm=300m的薄片状Yb:YAG晶体,采用铟焊工艺将其焊接到水冷系统上,用可调式恒温水箱对其进行温度控制.使用两个Ф一30 mm,R=50 mm的球面反射镜,完成了四程抽运.利用蒙特卡罗方法对抽运光斑的大小进行了计算,将反射镜轴向与光纤头轴向夹角控制在12°以内,以使抽运光斑半径与基模光斑半径比符合模式匹配原则.在LDA抽运功率为4.13 W时,获得了最高功率为670 mW的1 030 nm连续激光输出,光-光转换效率为16.2%.实验结果表明:该结构可降低激光介质的热透镜效应和应力双折射效应,获得高光束质量的激光输出,但散热系统和焊接工艺需进一步优化.     

四程抽运Yb:YAG盘式激光器

报道了激光二极管阵列(LDA)抽运Yb:YAG盘式激光器。Yb:YAG晶体掺杂浓度10-at.%,几何尺寸为Φ10mm×300μm,采用铟焊工艺将其焊接到水冷系统上,用可调式恒温水箱对其进行温度控制。利用蒙特卡罗方法对抽运光斑的大小进行了计算,将反射镜轴向与光纤头轴向夹角控制在120以内,以使抽运光斑半径与基模光斑半径比符合模式匹配原则。使用两个Φ=30mm,R=50mm的球面反射镜,完成了四程抽运。在LDA抽运功率为4.13W时,获得了最高功率为670mW的1030nm连续激光输出,光-光转换效率为16.2% 。     

双包层Yb/Er共掺光纤放大器的数值模拟

对980nm抽运的双包层Yb/Er共掺光纤放大器进行了数值模拟,分析了不同功率的信号光的增益情况,计算了稳态情况下光纤中反转粒子数,抽运光功率,信号光功率沿光纤轴向的分布以及放大器的斜率效率。当信号光初值较高时,通过模拟得到的斜率效率与实验结果相近。     

异径正心偏心斜交三通管料计算

一、正心针文‘计算公式图1、图2为计算公式符号示意图1)支管下端半径R:二R:一rs龙P,二(r,sin日。/sin。)哈只亡几拍放火 士〔R,一了兀冲丁行弃i五日汤厄下飞g“ 6)支管展开长S=2二:式中R一主管外半径 f一从外皮计插人量 H一支管中心至主管中心距离 r,一支管外半径 p,一圆周各等分点与同一直径夹角 。一支管倾斜角 r:一支管中半径 式中以图1主视图支管的轴线为中心线,线左侧取“+”,线右侧取“一”。表达式推导从路,参见局部视图B放大图。 2.举列(参见图1) 已知:R上=450。。,r:二315mm,f二50爪:。,H=SO0mm,a二60。则,R:=R:一f sina=41…     

圆柱凸轮靠模曲线的计算

本刊第十一期介绍了圆柱凸轮靠模曲线的计算原理和计算公式。本期就上述内容举一个计算实例。一个圆柱凸轮半径 r=45,靠模凸输半径R=90、r=10、δ=π/6、a=15,且靠模为带滚轮的机构,滚轮半径 r_1=16。求靠模滚轮中心线、包络线和它们的近似圆弧(长度单位为 mm,下同)。     

多模光纤弯曲损耗特性的测量与分析

分析了多模光纤强度型微弯传感器中多模光纤的弯曲损耗。提供了弯曲半径为1mm~8mm和10mm~26mm,光源波长为0.633μm、0.780μm、0.830μm G raded Index多模光纤的弯曲损耗特性的测试结果。首次观察到了多模光纤弯曲损耗随着弯曲半径的减小而增大的趋势,以及在弯曲半径为10mm~26mm范围内损耗特性的不平滑性,并利用传播常数和W G模理论对此现象进行了解释。     

双圈同轴光纤束位移传感器研究

设计了用于测量滑动轴承油膜的双圈同轴式光纤位移传感器,建立了双圈同轴光纤传感器调制函数的数学模型,并对其补偿机理进行了分析.对影响传感器特性的参数,包括接收光纤纤芯半径a0、发射光纤和接收光纤的轴间距d、光纤的最大入射角θc等进行了仿真计算和分析.结果表明,这种光纤传感器可以有效地消除因光源光强波动、表面反射率以及光纤传输损耗的改变对输出特性的影响.最后,通过分析给出了系统最终选定的设计参数.     

测量纵向位移的光纤位移传感器

提出了一种测量纵向位移的光纤位移传感器的方法。列出了3种可行性结构方案：双棱镜单光纤位移传感器、单棱镜单光纤位移传感器、双棱镜双光纤位移传感器，并对各自进行了理论推导以及系统仿真，得到了比较满意的结果。其中双棱镜双光纤位移传感器的性能最佳，在自聚焦透镜的半径为1mm的前提下，检测纵向位移的范围可以达到4mm，这为将来的实际应用提供了有效的参考。     

四程抽运Yb∶YAG薄片激光器

设计了四程抽运的Yb∶YAG薄片激光器。选用掺杂原子数分数为10%,几何尺寸为Φ10 mm×300μm的薄片状Yb∶YAG晶体,采用铟焊工艺将其焊接到水冷系统上,用可调式恒温水箱对其进行温度控制。使用两个Φ=30 mm,R=50 mm的球面反射镜,完成了四程抽运。利用蒙特卡罗方法对抽运光斑的大小进行了计算,将反射镜轴向与光纤头轴向夹角控制在12°以内,以使抽运光斑半径与基模光斑半径比符合模式匹配原则。在LDA抽运功率为4.13 W时,获得了最高功率为670 mW的1030 nm连续激光输出,光-光转换效率为16.2%。实验结果表明:该结构可降低激光介质的热透镜效应和应力双折射效应,获得高光束质量的激光输出,但散热系统和焊接工艺需进一步优化。     

Deformation path and springback behavior in double-curved bending at high temperature

In this work, integrated double-curved bending-sizing-unloading is simulated for a Ti6Al4V titanium alloy sheet. Bending radii R30 mm × R30 mm and R30 mm × R15 mm are used in the bending tests at 700 °C and 750 °C, respectively. A holding time of 0–600 s is applied to explore the effect of sizing time on forming accuracy. Similar experimental tests are performed for comparison with the finite element analysis results. Results show that bending behavior varies remarkably with the bidirectional radii. As for equal bidirectional curvature, bending along each direction occurs simultaneously. Given that bidirectional radii are different, the sheet consecutively experiences single small-, single large-, and double-curved bending. The deformation path results in nonuniform plastic strain distribution. The springback amount increases from the center to the marginal middle zone. Sizing at 700 °C or 750 °C in 600 s or 180–600 s can remarkably reduce the springback amount, respectively. The springback prediction via finite element method is consistent with that of the experiment.

     

Development of a simultaneous Hugoniot and temperature measurement for preheated-metal shock experiments: melting temperatures of Ta at pressures of 100 GPa

Equations of state of metals are important issues in earth science and planetary science. A major limitation of them is the lack of experimental data for determining pressure-volume and temperature of shocked metal simultaneously. By measuring them in a single experiment, a major source of systematic error is eliminated in determining from which shock pressure release pressure originates. Hence, a non-contact fast optical method was developed and demonstrated to simultaneously measure a Hugoniot pressure-volume (P(H)-V(H)) point and interfacial temperature T(R) on the release of Hugoniot pressure (P(R)) for preheated metals up to 1000 K. Experimental details in our investigation are (i) a Ni-Cr resistance coil field placed around the metal specimen to generate a controllable and stable heating source, (ii) a fiber-optic probe with an optical lens coupling system and optical pyrometer with ns time resolution to carry out non-contact fast optical measurements for determining P(H)-V(H) and T(R). The shock response of preheated tantalum (Ta) at 773 K was investigated in our work. Measured data for shock velocity versus particle velocity at an initial state of room temperature was in agreement with previous shock compression results, while the measured shock data between 248 and 307 GPa initially heated to 773 K were below the Hugoniot evaluation from its off-Hugoniot states. Obtained interfacial temperatures on release of Hugoniot pressures (100-170 GPa) were in agreement with shock-melting points at initial ambient condition and ab initio calculations of melting curve. It indicates a good consistency for shock melting data of Ta at different initial temperatures. Our combined diagnostics for Hugoniot and temperature provides an important approach for studying EOS and the temperature effect of shocked metals. In particular, our measured melting temperatures of Ta address the current controversy about the difference by more than a factor of 2 between the melting temperatures measured under shock and those measured in a laser-heated diamond anvil cell at ～100 GPa.     

Effects of inlet radius and bell mouth radius on flow rate and sound quality of centrifugal blower

The effect of inlet radius and bell mouth radius on flow rate of centrifugal blower were numerically simulated using a commercial CFD program, FLUENT. In this research, a total of eight numerical models were prepared by combining different values of bell mouth radii and inlet radii (the cross section of bell mouth was chosen as a circular arc in this research). The frozen rotor method combined with a realizable k-epsilon turbulence model and non-equilibrium wall function was used to simulate the three-dimensional flow inside the centrifugal blowers. The inlet radius was then revealed to have significant impact on flow rate with the maximum difference between analyzed models was about 4.5% while the bell mouth radius had about 3% impact on flow rate. Parallel experiments were carried out to confirm the results of CFD analysis. The CFD results were thereafter validated owning to the good agreement between CFD results and the parallel experiment results. In addition to performance analysis, noise experiments were carried out to analyze the dependence of sound quality on inlet radius and bell mouth radius with different flow rate. The noise experiment results showed that the loudness and sharpness value of different models were quite similar, which mean the inlet radius and the bell mouth radius didn’t have a clear impact on sound quality of centrifugal blower.     

超声点聚焦探头在球体中的声束发散与聚焦

探究了点聚焦探头焦点相对于球体在不同位置时的声束传播路径,讨论了进入工件内部的超声波束的聚焦与发散情况;分析计算出点聚焦探头在球体内实际焦距的表达公式,得到实际焦距与水层厚度等参数之间的关系;利用有限元分析软件建立点聚焦探头在球体内焦距变化的瞬态仿真模型,仿真结果与理论公式计算得到的结果基本一致;最后,通过实际焦距表达式确定了检测不同半径钢球的点聚焦探头的选型和水层厚度,实验现象验证了结果的可靠性。     

V型带传动的传递功率损失第Ⅱ部分:小带轮半径的影响(一)

采用运转的缠绕、毛边和齿形的V型带传递51,36和21 mm半径带轮间的功率.分开测量该带轮间的转矩和角速度损失表明它们分别近似与I/R和I/R2成比例,同时还大于根据现有理论的预测值.带轮半径由51减小至21 mm时,最大有效拉力比由21降至5.根据转矩损失的简化分析出现一无因次带变形参量（gEI/R4）^1/2,已经验求得与超出根据带拉长和径向屈服预测的转矩损失和速度损失两者有关.采用厚平带和圆柱带轮的辅助试验表明它的功率损失与相同截面积的V型带意外的接近,建议这些V型带损失归因于一般原始楔入带轮槽的情况,必须研究推测带体变斜或剪切变形说明小半径带轮与损失的关系.     

V型带传动的传递功率损失 第Ⅱ部分:小带轮半径的影响(二)

采用运转的缠绕、毛边和齿形的V型带传递51,36和21mm半径带轮间的功率。分开测量该带轮间的转矩和角速度损失表明它们分别近似与I/R和I/R2成比例,同时还大于根据现有理论的预测值。带轮半径由51减小至21mm时,最大有效拉力比由21降至5。根据转矩损失的简化分析出现一无因次带变形参量(gEI/R4)1/2,已经验求得与超出根据带拉长和径向屈服预测的转矩损失和速度损失两者有关。采用厚平带和圆柱带轮的辅助试验表明它的功率损失与相同截面积的V型带意外的接近,建议这些V型带损失归因于一般原始楔入带轮槽的情况,必须研究推测带体变斜或剪切变形说明小半径带轮与损失的关系。     

Non-contact measurement of the coefficient of thermal expansion of Al 6061-T6 with fiber Bragg grating sensors

An experimental study describing the non-contact measurement of the coefficient of thermal expansion of an aluminum (Al-6061-T6) specimen with two fiber Bragg grating sensors using a pair of C-lens collimators was carried out. The collimators were used for the freespace coupling between the fiber Bragg sensors and the optical sensing interrogator. During the experiment, the wavelength distortion of the optical signals was observed. Consequently, the measured thermal strains were corrected using an estimated collimator correction factor of 0.8466. The coefficient of thermal expansion of the specimen was then calculated to be (22.0 ± 0.1)×10^?6°C^?1 for every 5°C step in the range 35°C～75°C, which was in good agreement with the typical value of 23.6×10^?6°C^?1 for aluminum.     

Influence of piezoceramic to fused silica plate thickness on the radii of curvature of piezoelectric bimorph mirror

Piezoelectric based bimorph mirrors (PBM) find extensive use in focusing of x-ray beams. Many optical instruments require use of PBM whose radii of curvature can be tuned precisely. The 100 mm and 300 mm PBMs were fabricated with varying piezoelectric to fused silica plate thicknesses. The radii of curvature of free standing mirrors were measured as a function of voltage and it was found to decrease with increasing voltage. For a given piezoelectric plate thickness, as the fused silica thickness increases, the radii of curvature was found to increase owing to increase in stiffness of the mirror. On the other hand, for a given fused silica plate thickness, when the piezoelectric plate thickness is increased, the radii of curvature are decreased for a given electric field, due to increase in generated force. This study brings out the influence of piezoceramic to fused silica plate thickness on the radii of curvature of PBM.     

Theoretical and Experimental Temperature Distribution along a Plate

Existing equations for the temperature distribution along a plate produced by a point heat source are analyzed. Experimental values are compared with theoretical results from a formula employed in the development of a thermoelectric element for borehole use. On that basis, the influence of the heat-transfer coefficient on the calculated temperature distribution is established. In order to ensure agreement between the distribution calculated by the proposed formula and the experimental distribution, the value of the heat-transfer must be corrected.     

A two-stage vision-based method for measuring the key parameters of ball screws

Ball screws are crucial for improving the reliability and interchangeability of transmission mechanical systems; however, existing contact measurement methods that utilise stylus contact are not efficient, which precludes their use for rapid in-situ geometry evaluation. This paper presents a vision-based two-stage method for rapid measurement of key parameters (raceway arc radii and centre distance) of ball screws. The edge contour information is extracted from the acquired image using the dual-tree complex wavelet transform and non-maximal suppression. In the matching stage, a shape-matching algorithm is used for detecting approximate geometrical centres of raceway arcs. The refinement stage, on the other hand, is implemented for acquiring precise dimensional results. Furthermore, the method of averaging multiple measurements is performed to suppress random noise. A comparative experiment is presented to validate the robustness of the proposed method. Based on experimental results, the calculated mean absolute errors in the measurement of the two raceway arc radii and the centre distance are found to be 0.0082 mm, 0.0079 mm and 0.0055 mm, respectively. This study therefore paves the way for key parameter measurement without removing ball screws.