Photomobile Polymer Materials with Crosslinked Liquid‐Crystalline Structures: Molecular Design,Fabrication, and Functions

Crosslinked liquid‐crystalline polymer materials that macroscopically deform when irradiated with light have been extensively studied in the past decade because of their potential in various applications, such as microactuators and microfluidic devices. The basic motions of these materials are contraction–expansion and bending–unbending, which are observed mainly in polysiloxanes and polyacrylates that contain photochromic moieties. Other sophisticated motions such as twisting, oscillation, rotation, and translational motion have also been achieved. In recent years, efforts have been made to improve the photoresponsive and mechanical properties of this novel class of materials through the modification of molecular structures, development of new fabrication methods, and construction of composite structures. Herein, we review structures, functions, and working mechanisms of photomobile materials and recent advances in this field.     

红宝石脉冲激光动态光力学方法研究与进展

本文提出了瞬态图像采集技术和电磁脉冲加载装置。应用红宝石脉冲激光光源,介绍了动态全息光弹性、动态散斑干涉、动态云纹干涉、水下爆炸全息干涉、动态电子散斑干涉和动态数字散斑相关等多种方法的测试原理和测试技术。为动态位移场、应变场和应力场的定量分析提供了广泛的应用前景。     

基于BP神经网络的条纹级数插值方法

数据采集是光测力学数据处理自动化的关键和难点，特别是对条纹稀疏和低级数区．针对上述困难，本文利用ＢＰ神经网络能对函数进行逼近的特征，对条纹插值进行了探讨；经研究改进后的算法，其收敛速度明显提高．作为例子，给出了一幅光弹性等差线条纹图的插值实验，获得了令人满意的结果．     

虚位移场方法在石墨材料力学参数测量中的应用

光测实验技术在现代力学研究中得到了广泛的应用。对于材料力学参数如杨氏模量和泊松比的测量,可利用典型加载试验如拉伸试验、弯曲试验并结合光测方法(如云纹和数字图像相关技术)得到位移值,利用载荷信息和应变场信息通过计算获得相关的力学参数。本文利用虚位移场方法测量石墨材料的力学参数。结合石墨材料的三点弯曲实验,由数字图像相关法测量得到试件表面的非均匀变形场。通过选择两组不同的虚位移场,可以反算出材料的力学参数:杨氏模量和泊松比。结果表明这种方法可以有效测量石墨材料的弹性参数。该方法可望在材料力学行为检测中得到推广应用。     

成像光路布置对数字相机热致测量误差影响规律的研究

研究了数字相机成像系统中物距和成像系统固定方式两个因素对相机自发热导致的图像变形误差的影响规律,通过分析得到了热致图像"虚变形"与物距的倒数关系并进行了实验检验。推导了固定位置位于镜头上时图像"虚变形"的表达式并进行了实验验证。研究表明,无论是成像系统的固定点位于相机上还是镜头上,自发热都会使得图像发生一个虚的膨胀变形,其大小与镜头接口的热膨胀参数和像距有关。本研究得到的模型和规律为指导实际光测力学应用中的光路布置以减小数字相机自发热导致的测量误差提供了理论依据。     

Effects of double photoreactions on polycoumarate photomechanics

We established a polymerization condition of 3‐hydroxycinnamic acid, 3HCA, having photoreactive units over all the main chains. The polymers showed two types of photoreaction, that is, intramolecular E–Z isomerization and interchain [2 + 2] cycloaddition. Spectroscopic studies showed that the rate of the isomerization was higher than that of the cycloaddition. Although the original fiber was very brittle, the short‐time UV‐irradiation made the fiber softer and more elastic because the chain bending by the isomerization preferentially occurred. On the other hand, the long‐time irradiation made the fiber harder because of the cross‐linking by the cycloaddition, and simultaneously enhanced the elasticity. Besides we found that the cast film of P3HCA showed a photo‐bending behavior with the convex surface facing the UV‐lamp by the initial E–Z isomerization. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

动态光力学多种测试方法研究及其进展

本文提出了多种动态光力学方法，还介绍一种瞬态图象的采集技术，并将其应用到动态电子散斑（ＤＥＳＰＩ）的测试方法中     

红宝石脉冲激光动态光力学方法研究与进展

本文提出了瞬态图像采集技术和电磁脉冲加载装置。应用红宝石脉冲激光光源,介绍了动态全息光弹性、动态散斑干涉、动态云纹干涉、水下爆炸全息干涉、动态电子散斑干涉和动态数字散斑相关等多种方法的测试原理和测试技术。为动态位移场、应变场和应力场的定量分析提供了广泛的应用前景。     

Organic Photomechanical Materials

Organic molecules can transform photons into Angstrom‐scale motions by undergoing photochemical reactions. Ordered media, for example, liquid crystals or molecular crystals, can align these molecular‐scale motions to produce motion on much larger (micron to millimeter) length scales. In this Review, we describe the basic principles that underlie organic photomechanical materials, starting with a brief survey of molecular photochromic systems that have been used as elements of photomechanical materials. We then describe various options for incorporating these active elements into a solid‐state material, including dispersal in a polymer matrix, covalent attachment to a polymer chain, or self‐assembly into molecular crystals. Particular emphasis is placed on ordered media, such as liquid‐crystal elastomers and molecular crystals, that have been shown to produce motion on large (micron to millimeter) length scales. We also discuss other mechanisms for generating photomechanical motion that do not involve photochemical reactions, such as photothermal expansion and photoinduced charge transfer. Finally, we identify areas for future research, ranging from the study of basic phenomena in solid‐state photochemistry, to molecular and host matrix design, and the optimization of photoexcitation conditions. The ultimate realization of photon‐fueled micromachines will likely involve advances spanning the disciplines of chemistry, physics and engineering.     

A BRIEF REVIEW AND PROSPECT OF EXPERIMENTAL SOLID MECHANICS IN CHINA

In this review, acritical look at the research progress ofexperimentalsolid mechanics in China for the past years is presented. Issues are discussed of the discovery and development of new fundamental methods and techniques versus performance benchmarking for many of their applications. Included herein are photoelasticity and various forms of modern photomechanics, acoustical techniques, image processing and videometrics, radial and spectrum techniques, and experimental mechanics on micro/nano scale. It is also noticed that both the ever developed instrumentation and specialized synthetical techniques have played important roles in advancing experimental mechanics in scientific researches and industrial applications. Finally, an attempt is made to look into the future of experimental solid mechanics with personal opinions offered on what the future trends will be for the researches in the field.