基于高光谱漫透射成像可视化检测脐橙可溶性固形物

厚皮类瓜果内部品质的无损检测是目前水果产业的检测技术瓶颈。本文采用高光谱漫透射技术对脐橙可溶性固形物(SSC)含量进行可视化分析研究。通过基线校正(Baseline)预处理结合连续投影算法(SPA)优选9个特征波长,建立SSC偏最小二乘回归(PLSR)模型,校正集相关系数r_(cal)为0.891,校正集均方根误差RSMEC为0.612°Brix,预测集相关系数r_(pre)为0.889,预测集均方根误差RMSEP为0.630°Brix。最后,计算各个像素点的SSC值结合图像处理技术得出SSC的可视化分布图,直观判断脐橙SSC含量高低。     

Nondestructive testing of objects of complex shape using infrared thermography: Determination of the spatiotemporal distribution of the irradiation heat flux

The existing inverse methods used to determine the heat flux density require that the forward problem and the problem domain (geometry) be known. In this paper, in order to determine the spatiotemporal heat flux density without knowing the real problem domain, we propose an approach based on temporal tracking of the thermal front. The proposed approach is particularly relevant when a three-dimensional formulation is adopted for nondestructive testing using infrared thermography. For such a formulation, heat flux density resulting from the external thermal stimulus is needed and must be determined to accurately characterize the defects and reconstruct the internal geometry of the inspected objects. The proposed approach uses only two inputs: the time-dependent temperature of the frontal surface recorded by an infrared camera and the 3D point cloud of the frontal surface collected by a 3D scanner. The method is evaluated numerically on an object of complex shape. We consider the case of pulsed thermal stimulus as well as the cases of unit step and modulated thermal stimuli. An experimental validation is performed on a cylindrical object submitted to a pulsed thermal stimulus and a modulated thermal stimulus. The results show the accuracy of the method which can easily be implemented as the initial step of the three-dimensional quantitative nondestructive testing of objects using infrared thermography.     

X射线荧光光谱测定石墨烯粉体中的杂质元素

石墨烯粉体是我国已具备规模化生产能力的主要石墨烯材料,针对其关键物理化学特性建立准确可靠的测量方法极为重要.开发了一种利用X射线荧光光谱（XRF）技术对石墨烯粉体中杂质进行快速、无损分析的检测方法,可实现对石墨烯粉体产品质量的便捷初判.研究了石墨烯粉体样品的不同测试形态,并通过将XRF测量结果与电感耦合等离子体-原子发射光谱（ICP-OES）、电感耦合等离子体-质谱（ICP-MS）和X射线能谱（EDX）等检测技术的测量结果进行对比,结果表明XRF可对石墨烯粉体样品中的非金属杂质S、Cl、Si、P及金属杂质Na、Mg、Ca、Fe、Cu、Ti、W、Cr等可靠检出,可实现对石墨烯粉体中杂质元素的快速、简便、无损低成本的定量测量.     

基于激光超声的微裂纹检测技术的研究

在固体中利用激光产生超声波 ,可作为超声测量和材料无损检测的一种新方法。介绍了激光超声表面波的产生机理、微裂纹的检测方法及其应用。采用Nd∶YAG脉冲激光器、扩束与聚焦透镜组、PZT探头、数据分析仪等器件设计并构建了一套基于接触式检测方法的激光超声微裂纹检测实验系统。通过对大量实验数据进行处理 ,得出了相应的各种关系曲线 ,说明了线光源产生的超声表面波非常适用于材料表面微裂纹的检测     

小波变换理论在损伤探测中的应用

本文采用小波变换技术，对含边裂纹的悬臂梁受冲击载荷作用的情况进行分析。根据电测法得到的动态应变的实验结果，用Morlet小波变换处理，能够很好地确定边缘缺陷的特性。这为结构损伤检测提供了一个很有效的方法，具有广阔的工程应用前景。     

High-temperature deformation measurements using digital-image correlation

The ability of the computer-vision technique of digital-image correlation to measure full-field in-plane surface deformations at elevated temperatures was evaluated by a series of experiments. Samples were subjected to pure translation, free thermal expansion and uniform tensile loads. Results are presented which show that the digital-image-correlation technique remains fully capable of accurate measurement of the displacements and strains on the surface of a planar object at temperatures up to 650°C.     

用磁性探头检测承受偏心载荷的开口钢环的应力分布

用磁性探头测量了45~#钢制开口环在承受偏心载荷作用下的应力分布,与有机玻璃试样的光弹检测结果基本一致.本工作将探测到的感生电压积分,直接获得磁感强度峰值与待测应力的函数关系.实验证实,在较宽的应力范围内,二者有较好的线性关系,易于作应力标定。     

应力波在管道中传播的实验研究

实验研究了轴对称加载条件下,在有、无缺陷的管道中应力波的传播特性。实现了在非弥散频率范围内单模态应力波的激励;在无缺陷的情况下研究了应力波的反射、衰减等;同时研究了缺陷前后不同点、距缺陷一定距离的同一截面上的多点对激励的响应。结果表明,由于在波的传播过程中衰减相对较小,这种方法有望实现管道的长距离缺陷检测。     

用压电材料进行损伤鉴别的理论与数值分析

对压电材料用于损伤监测的理论和数值分析做了一些研究。首先,设计了一种用压电材料进行损伤监测的模型。然后,对这个模型进行分析,找出简单有效的解答办法,将求解过程分解为断裂力学分析和压电分析两部分,并通过适当的假设,进行了详细的理论推导。通过正电有限元程序进行仿真计算,将数值计算结果与理论解进行比较以验证提出理论的正确性,并分析得到了裂纹参数与压电层表面电势变化之间的关系和普通弹性材料泊松比对波峰参数的影响。最后,用提出的方法验算了两个例题。从结果来看,理论结果和数值结果非常接近。     

Reflection coefficient of ultrasonic waves as a measure of interface stresses in high pressure multi-layer cylinders

Abstract

Contact stresses in high pressure multi-layer cylinders are sometimes measured using ultrasonic technique. As a measure of the contact stresses the coefficient of reflection of ultrasonic waves from the contact interface between two adjacent outer layers is applied. The coefficient of reflection is an involved function of several parameters. Experimental and theoretical investigations show that this function may change non-monotonously with frequency of ultrasonic waves which may lead to an ambiguity of the assumed criterion. In order to check this function for higher frequencies, measurements of the reflection coefficient from a contact interface between plane steel samples were made for the frequencies up to 190 MHz.