云纹干涉法测定复合材料单孔连接件的应力场

本研究首次将云纹干涉法应用于复合材料单销钉连接件位移场的测量。从位移的云纹图用位移导数法求得销钉孔中心水平截面上的应变。根据复合材料层合板的直法线假设和层合板的折算刚度矩阵算出截面的平均应力分布。通过静力平衡,所得误差在6%以内。本研究结果证实,云纹干涉法测量复合材料连接件的应变场和应力场是有效的实验方法。      

测量薄膜折射率的光栅衍射干涉方法

根据光的干涉理论,讨论了条纹周期数对测量薄膜折射率不确定性的影响,推导出干涉条纹错位量与薄膜折射率和厚度的关系式。由此提出采用光栅衍射干涉测量薄膜折射率的方法和实验方案。实验表明:该方法的干涉条纹测量精度达λ/10~λ/20,薄膜折射率测量精度可达 0.01 以上。     

干涉SAR在遥感测量中的应用

目的　论述干涉 SAR技术在遥感测量中的应用 .方法　在回顾干涉 SAR发展历史之后 ,详细地说明了干涉 SAR的工作原理和信号处理技术 ,最后讨论了干涉 SAR广泛的应用现状和前景 .结果　干涉SAR技术可以广泛应用于 DEM测量及地球测绘的多个方面 .结论　这项技术将会得到更大的发展 ,中国应广泛开展干涉 SAR技术的应用研究     

希尔伯特变换实时全息干涉条纹相位提取

实时全息干涉法可以观察记录整个测试过程中条纹图的动态变化,传统相位提取算法只适合于静态干涉条纹图相位的提取.根据实时全息干涉条纹和希尔伯特变换的特点,提出了利用希尔伯特变换提取实时全息干涉条纹相位值的方法,采用了高通滤波的方法减少背景光强的影响,对铝片受力变形实验中实时全息干涉条纹的相位变化分布进行了提取.实验表明:希尔伯特变换法适合于动态条纹的相位提取,可以自动提取实时全息干涉测量过程中全场各点在任意两个时刻间的相位变化值,且测量结果与实时全息干涉条纹人工分析结果一致.     

全视场外差白光干涉测量技术

为了解决传统白光干涉测量技术中对线性位移机构的位移精度要求过高的问题,本文提出了一种全视场外差白光干涉测量技术。该技术主要通过使用存在差频的白光干涉信号作为光源来实现在大扫描步长和低扫描精度条件下相干峰位置的高精度检测。本文首先建立了白光外差干涉的数学模型,再根据数学模型提供的光强信号特性提出了整体系统设计方案,然后对测量方案的可行性进行了实验验证。最后针对多种误差对算法计算精度的影响进行了理论分析和数据对比。误差分析的结果表明:白光外差干涉测量技术提供更高的测量精度和更好的抗干扰性能,有效地降低了传统白光干涉测量对线性位移机构精度的严苛依赖,为光学自由曲面检测技术提供了更多的可选解决方案。     

干涉条纹图估测基线的方法研究

根据SAR干涉测量原理，提出了利用干涉相干条纹估测基线的方法，并以欧洲空间局资源卫星1号和2号携带的SAR系统在中国新疆伽师试验区获取的串接式（Tan-dem）干涉测量数据为数据源，对提出的方法进行了验证，结果表明，该方法能有效地估测基线，并弥补不能有效获取卫星轨道参数时，对基线进行估测的缺陷，该方法尤其适用于差分干涉测量的研究。     

白光相移干涉中频谱对测量精度的影响

在相移干涉中有时采用白光干涉来扩大深度测量范围,白光光源的使用,缩短了光束的相干长度,降低了测量精度。本文从干涉理论出发推导了白光相移干涉法测量三维表面形貌的计算公式,通过数值积分的方法分析了干涉光频谱对测量精度的影响。分析表明,在白光相移干涉测量中表面形貌的测量精度与中心波长和频谱宽度有关,白光频谱越宽,测量精度越低,中心波长越大,测量精度越高。     

重轨InSAR平地干涉相位特性研究

鉴于平地干涉相位的补偿是重轨合成孔径雷达干涉测量（InSAR）的重要环节以及平地干涉相位特性对于InSAR处理过程中的参数选择和基线重估计的重要意义,本文针对不同参考面对平地干涉相位特性的影响以及如何利用平地干涉相位特性实施干涉基线重估计的问题进行了研究,从理论上推导出了参考面为平面和球面情况下平地干涉相位以及平地干涉相位频率的标量表示方法,对平面、球面和WGS84椭球面三种不同参考面所对应的平地干涉相位特性进行了对比分析,给出了利用平地干涉相位和平地干涉相位频率方法进行干涉基线重估计的算法理论。研究表明,利用平地干涉相位特性可以实施干涉基线重估计,而考虑到参考面选择对平地干涉相位的影响,在进行干涉处理过程中必须选择适当的参考面。     

激光外差干涉测试

激光干涉测试具有测量准确度高、测量范围宽、测量速度快、测量过程容易实现自动化等优点。本文介绍一种抗干扰能力强、能在车间现场进行精密计量的激光外差干涉测试法和它的应用。     

柱面面形干涉测量

介绍了一种柱面面形干涉测量方法。该方法选用计算全息片作为柱面波转换器,能够将平面干涉仪出射的平面波转换成理想柱面波前,依此为基础,建立了柱面干涉测量系统,能够实现柱面的干涉测量。为了获得柱面的真实面形误差,分析了调整误差引起的失调像差,并给出了失调像差的分离方法。最后,以玻璃圆柱体为被测样本,对单孔径面形的重复性进行验证,20次测量结果峰谷值（PV）标准差为20.2 nm,为PV平均值的0.55％。     

Numerical simulations and experimental measurements of the stress intensity factor in perforated plates

A numerical procedure, which combines two hybrid finite element formulations, was developed to analyse the stress intensity factors in cracked perforated plates with a periodic distribution of holes and square representative volume elements. The accuracy of the method in predicting the stress intensity factor was verified by a comparison with experimental measurements, carried out by a photoelasticity method, and by commercial finite element software. Several simulations were executed by varying both the crack length and the hole diameters, and the effects of the holes on the stress intensity factor are illustrated. The method shows high accuracy and efficiency, as small differences were observed when compared with the traditional finite element method, notwithstanding a strong reduction in degrees of freedom and mesh complexity.     

芯棒锥面结构对孔冷挤压强化残余应力场的影响

为了在紧固孔周引入均匀的残余压应力,以延长紧固孔构件的疲劳寿命、提高其抗应力腐蚀性能,利用ANSYS有限元软件,建立了轴对称弹塑性有限元模型,对直接芯棒冷挤压强化过程进行了仿真,特别是对芯棒的前锥段曲线结构形式进行了设计与分析,研究了前锥段曲线形式对残余应力场分布的影响.结果表明:孔壁表面的周向残余应力分布复杂且不均匀,比较而言,外凸型正弦曲线型芯棒所产生的残余压应力沿孔壁深度方向分布更加均匀;几种曲线形式的芯棒在上表面近孔边区域均产生了径向残余拉应力,在孔的挤入段产生了轴向残余拉应力,但外凸型正弦曲线型芯棒在上述区域所产生的残余拉应力较小,且分布区域也较小.     

Methods for modelling the ultimate strength of orthotropic plate with a central hole under uniaxial tension

The stress state in plates with circular holes made of orthotropic homogeneous material has no singularities and it can be exactly determined. The numerical stress distribution calculation by the finite element method will be compared with those obtained by the analytical equations developed by several authors. The goal of this work is to validate the finite element method, in conjunction with in-plane and out of plane failure criteria, in order to calculate not only the stress distribution for orthotropic plates with circular holes but also to determine their ultimate strength.The tool used has been a user subroutine (UMAT) specially developed for this work that implements the features of the commercial FE program (ABAQUS). The code performs an implicit analysis of the stress-state with progressive damage modelling.Finally, both of them, numerical and analytical method, will be checked with experimental tests by means of strain gauges.     

The residual stress intensity factors for cold‐worked cracked holes: a technical note

Cold‐working of riveted holes reduces the stress intensity factor associated with cracks that may develop at the hole boundary, by creating a compressive residual stress field. The residual stress field is determined using the finite‐element method and the reduction of the stress intensity factor for different values of the interference is evaluated with the weight function method, in the case of an infinite plate made from an elastic–perfectly plastic material, and having a hole with two symmetrical cracks. Once the weight function of the structure is known, further calculation of the stress intensity factors for different loadings such as a remote uniform stress, or a point load that simulates the action of the rivet can be performed without difficulty.     

Effect of detail design on fatigue performance of fastener hole

In the present study, a series of tests were conducted on aluminum alloy 2024 to investigate the effect of detail design on the fatigue behavior of fastener holes in specimens. Two types of detail designs were concerned. One was the mode of fastener holes (countersunk rivet or countersunk bolt), the other was drilling process (traditional air-drilling process or one step compound cutting process). The fracture surfaces were observed by means of an optical microscope. Finite element method (FEM) was employed to analyze the distribution of stress around the fastener holes. The results showed that crack always initiated at the hole edge where the stress concentration occurred. Crack initiation was induced by stress concentration. Crack initiation life accounted for 80% of total fatigue life of fastener holes. The fatigue life of fastener hole using countersunk rivet was longer than that using countersunk bolt. Contrasted to traditional air-drilling process, the fatigue life of fastener hole could be improved by 44–55% using one step compound cutting process. However, the dispersibility of fatigue life became increasingly severe when fatigue life was prolonged.     

Stress intensity factors for some through-cracked fastener holes

A stress intensity factor solution is developed for a large plate containing radial hole cracks loaded with arbitrary crack face pressure. When the pressure is defined as the unflawed hoop stress surrounding a mechanical fastener, stress intensity factor calibrations are readily computed by the linear superposition principle. Results obtained in this manner agree well with previous solutions determined for open holes loaded in remote tension. The potential usefulness of the present analysis is further demonstrated with application to specific fastener configurations, including interference fit fasteners, pin-loaded plates, and cold-worked holes.     

气膜孔分布对DD6单晶高温合金高周疲劳断裂行为的影响

利用带不同电液束加工气膜孔分布的DD6单晶气冷叶片模拟试样,研究其在常温下的高周疲劳性能,并对试样断口及断口侧面形貌进行宏观与微观观察。结果表明:在相同的实验条件下,气膜孔的存在对试样高周疲劳寿命的影响较大,无孔试样的平均寿命约为带3排孔试样的4倍,但是气膜孔布局对疲劳寿命的影响相对较小。通过断口宏观与微观观察发现,无孔试样呈线源特征,而1~3排孔试样裂纹均从气膜孔附近起源,呈多源特征。根据断口和晶体学理论推测,对于无孔、1排孔和多排孔试样的中间部位,裂纹沿{001}滑移面扩展;而对于多排孔试样的上下2排孔孔周的裂纹沿{111}滑移面扩展。采用有限元方法分析4种不同试样孔边应力场的分布规律,数值模拟分析结果与试样的断裂位置及形貌吻合。     

含多椭圆孔无限大各向异性薄板弯曲问题研究

该文利用各向异性体弹性理论中的复势方法,以Faber 级数和保角映射为工具,对含多椭圆孔无限大各向异性薄板弯曲问题进行分析,得到了含多椭圆孔无限大各向异性薄板弯曲的级数解形式,给出了无限大薄板在受到弯曲载荷时孔边的应力分布,并讨论了孔距、孔的数量、排列方式、椭圆度、材料的各向异性对孔边应力分布的影响,得到了有益的结论.该方法具有计算精度高、收敛速度快、方便快捷等优点.     

The stress distribution around holes in thermal barrier coatings

The residual stress distribution in the thermally grown oxide (TGO) around holes in thermal barrier coatings has been measured using luminescence piezospectroscopy. Far removed from the holes the residual stress field in the oxide is equi-biaxial and independent of position but in the vicinity of the holes, the mean stress decreases monotonically towards the edge of the hole. The characteristic distance over which the stresses vary is of the order of the half the hole radius, typically 10–100 times the thickness of the TGO, consistent with a shear-lag model for stress redistribution. The measurements also indicate that the stress distribution in the TGO is unaffected by the presence of an as-deposited thermal barrier coating.     

基于有限元法的果蔬保鲜包装箱通风孔设计

通过建立不同通风孔设计的果蔬保鲜包装箱有限元模型,模拟分析了其应力分布云图,探讨了果蔬保鲜包装箱通风孔设计的主要参数。分析结果表明,长圆形、靠近纸箱中部且对称分布的偶数个通风孔设计,能有效减少应力集中,避免纸箱压缩强度的大幅下降。为实际应用中果蔬保鲜包装箱通风孔结构设计提供参考。