细观力学研究方法与实验技术

应用力学在工程应用中出现的事故导细观力学的兴起，本文阐述限细观力学的特点、研究方法和实验技术。对作者研究的电子光学散斑干涉法进行了简要的介绍。     

含夹杂和微裂纹复合材料的损伤演化和分析

利用细观力学的Ｅｓｈｅｌｂｙ和Ｍｏｒｉ－Ｔａｎａｋａ理论，考虑纤维和微裂纹之间的相互作用，研究了定向分布微裂纹的演化规律及其对材料力学性能的影响，分析了纤维体积份数，弹性系数、微裂纹密度，纤维不同取向与基体开裂强度之间的变化关系，并给出了许多有意义的结论。     

夹杂物附近萌生疲劳裂纹过程的细观力学实验研究

本文对夹杂物附近萌生疲劳裂纹过程进行了细观实验观察，在利用显微图象连续测量细观变形场的实验方法的基础上，对疲劳裂纹萌生过程的塑性应变场及其随循环次数增加变化的统计规律进行了研究。     

含裂纹弹性结构对声散射作用研究

研究了含裂纹的弹性结构对声的散射作用.应用分配形有限元和边界元相结合的方法于含裂纹的结构声相互作用问题.利用二级分形有限元方法对含裂纹结构进行离散,这将使得自由度大为减少;使用边界元方法计算外域散射声场,这将自动满足无限远辐射边界条件.数值结果初步表明:(1)随着裂纹深度的增加,结构声耦合系统的共振频率将下降;(2)裂纹附近的声场所受的影响更为明显.     

细观力学实验技术综述

本文以应用较多的光测技术为主,综述了细观力学测量中光、声、磁、射线等试验技术.可望在细观研究中发挥重要作用的光学方法有全息干涉、激光或非相干光散斑法、云纹和云纹干涉法、格子法、各种显微镜技术、衍射法和射线技术.在各种方法中,图像处理系统和技术都将发挥很大的作用。     

冲击作用下含预制裂纹梁柱试件的动态断裂

利用焦散线实验系统,进行了冲击加载下含预制裂纹梁柱试件的断裂实验,研究了梁柱试件的梁柱节点、梁上和柱端裂纹的扩展轨迹、扩展速度和应力强度因子的变化规律。实验结果表明:受冲击后,试件首先在梁柱节点处开裂,并在裂纹扩展过程中发生明显的曲裂运动,证明梁柱节点处最容易受到破坏。预制裂纹条数越多,梁柱节点处开裂越晚,说明裂纹条数少,能量可以在裂纹尖端积聚得更集中、更快。含柱端预制裂纹的试件,2条裂纹的开裂相隔时间要长于含梁上预制裂纹的试件;同时,试件的第2条裂纹优先在梁上裂纹处开裂,说明固端支座比简支梁断裂需要更多的能量。随着预制裂纹的增多,梁上裂纹在扩展过程中的曲裂现象减弱, 由于部分能量在柱端裂纹处积聚,用于推动梁上裂纹扩展的能量相应地减少。并且由于柱端裂纹的存在,梁上裂纹受到的拉应力分量减小,导致裂纹尖端受到弯矩变小,影响了裂纹的曲裂运动。     

云纹干涉法在新材料细观力学实验研究中的应用

本文介绍了云纹干涉法用于新材料细观力学实验研究的几个典型例子，实验结果不仅为这些新材料的细观本构理论研究提供了重要的实验依据，同时也表明云纹干涉法是固体材料细观力学实验研究的有效手段之一。最后简要地分析了云纹干涉法在细观力学实验研究中的测量能力。     

SHPB系统试件恒应变率加载实验方法研究

为了获得材料准确的动态力学性能参数,提出了两种对试件实现恒应变率加载的实验方法:双试件SHPB方法和将圆柱形子弹改变成柱锥形子弹的SHPB方法。对三种金属材料进行了实验,并用数值模拟的手段对这两种方法进行了验证和比较。     

复杂应力下脆性岩石材料的微裂纹损伤特性

基于无限大体深埋平片状椭圆形裂纹的变形场及其扩展条件,分别推导了脆性岩石材料内部具有任意空间取向的单个张开型或闭合型椭圆形微裂纹及其扩展引起的附加柔度张量;考虑微裂纹系统对材料变形的影响,引入了概率密度函数,得到了任意应力状态下脆性岩石材料的宏细观损伤模型;分析了椭圆形微裂纹的短长轴比率对材料损伤的影响.计算结果显示:材料损伤随着短长轴比率的增大而增大,短长轴比率对材料损伤的影响会随着载荷的增大而提高.将本文模型应用于混凝土的单轴拉伸和花岗岩的单轴压缩,结果表明本文模型能够对实验现象给予很好地解释.     

粘接双材料界面微区力学行为的细观实验分析

本文将显微光栅与显微测距技术结构起来，实现了物体表面位移场的细观测量，应用这一方法，本文定量地测量了高分子粘接结构界面及周围区域的变形的应变，实验发现界面两侧存在着一个影响区，在影响区内材料的力学性质发生了变化，本文在实验结果的基础上讨论和分析了这一变化并对界面的力学模型进行了讨论。     

THE MEASUREMENT OF PLASTIC DEFORMATION AND CRACK GROWTH IN CRACKED SPECIMENS BY SAM

In this paper,scanning acoustic microscope(SAM) was used to obtainsome characteristic photographs which explain the mesoscopic information of severalcracked specimens.New results on subsurface information of steel,nickel andaluminium were presented.Plastic deformation and crack initiation were observed andanalysed.The length of crack propagation was measured.SAM is particularly suited tothe study of many mesoscopic phenomena in material science because it can imagemesoscopic subsurface feature without sectioning.It is revealed that SAM has a brightfuture in the field of mesomechanics.     

Scanning Electron Microscopy for Quantitative Small and Large Deformation Measurements Part II: Experimental Validation for Magnifications from 200 to 10,000

A combination of drift distortion removal and spatial distortion removal are performed to correct Scanning Electron Microscope (SEM) images at both ×200 and ×10,000 magnification. Using multiple, time-spaced images and in-plane rigid body motions to extract the relative displacement field throughout the imaging process, results from numerical simulations clearly demonstrate that the correction procedures successfully remove both drift and spatial distortions with errors on the order of ±0.02 pixels. A series of 2D translation and tensile loading experiments are performed in an SEM for magnifications at ×200 and ×10,000, where both the drift and spatial distortion removal methods described above are applied to correct the digital images and improve the accuracy of measurements obtained using 2D-DIC. Results from translation and loading experiments indicate that (a) the fully corrected displacement components have nearly random variability with standard deviation of 0.02 pixels (≈25 nm at ×200 and ≈0.5 nm at ×10,000) in each displacement component and (b) the measured strain fields are unbiased and in excellent agreement with expected results, with a spatial resolution of 43 pixels (≈54 μm at ×200 and ≈1.1 μm at ×10,000) and a standard deviation on the order of 6 × 10⁻⁵ for each component.

贯穿的中心裂纹LY12板在动静态加载条件下的断裂实验研究

本文对具有不同裂纹尺寸的中心裂纹ＬＹ１２板试样在动、静态拉伸加载条件下，分别进行了断裂实验研究，得到了名义断裂应力与板的初始裂纹长度间的关系。通过对动、静态实验结果的比较，得到在动、静态拉伸加载条件下某些参量间的相互关系。     

脉冲放电止裂后裂尖处纳米尺度下的力学性能测试

应用扫描探针显微镜SPM(scanning Probe Microscopy)，对经过脉冲放电止裂后的40Cr模具钢裂尖处的组织进行了纳米尺度下的力学性能测试。测试结果表明：脉冲放电不仅使裂纹尖端钝化，同时使围绕裂尖处组织的细观硬度和细观杨氏弹性模量得到了提高，与宏观观测和分析规律相符，纳米尺度下微观力学性能测试结果为脉冲放电裂纹止裂技术的工程应用提供了微观尺度下的证据。     

Fracture Mechanics of Corrosion Cracking in Concrete by Acoustic Emission

Nucleation of microcracks can be detected and analyzed by acoustic emission (AE), by which crack kinematics of locations, types and rientations are quantitatively estimated. The procedure was applied to clarify mechanisms of corrosion cracking. Based on fracture mechanics, numerical analysis was conducted by the boundary element method (BEM). Relations between the stress intensity factors and crack types were investigated by BEM solutions. In experiments, four types of crack patterns were nucleated by employing expansive agent. Following the surface crack, the diagonal crack and/or the horizontal crack propagated. The internal crack extended after the surface crack was terminated. Depending on the crack types, contributions of mode-I and mode-II were varied. According to AE results, four crack patterns observed differently consisted of tensile, mixed-mode and shear cracks. It is demonstrated that mechanisms of corrosion cracking in concrete are dominantly of mode-I failure along with a minor contribution of mixed-mode and mode-II.     

An Experimental Investigation into the Acoustic Characteristics of Fluid-filled Porous Structures—A Simplified Model of the Human Skull Cancellous Structure

In nature, shape and structure evolve from the struggle for better performance. Often, biological structures combine multiple beneficial properties, making research into mimicking them very complex. Presented here is a summary of observations from a series of experiments performed on a material that closely resembles the human skull bone’s cancellous structure under acoustic loads. Transmission loss through flat and curved open-cell polyurethane foam samples is observed using air and water as the two interstitial fluids. Reduction in strength and stiffness caused by porosity can be recovered partially by filling the interstitial pores with a fluid. The test findings demonstrate the influence of the interstitial fluid on the mechanical characteristics of a porous structure in a quantitative manner. It is also demonstrated that the transmission loss does not depend only on the mass per unit area of the structure as predicted by acoustic mass law. Current tests also demonstrate that the transmission loss is more sensitive to the interstitial fluid than the shape and support conditions of the structures. Test observations thus support the concepts of “moisture-sensitivity of biological design” and the “law of hierarchy in natural design”.     

中心直裂纹平台巴西圆盘复合型动态断裂实验研究

制作了中心直裂纹平台巴西圆盘（cracked straight through flattened Brazilian disc-CSTFBD）试样,利用分离式霍普金森压杆（split Hopkinson pressure bar-SHPB）加载,进行了岩石纯Ⅰ型和复合型（Ⅰ＋Ⅱ型）动态断裂实验。由于加载角（载荷方向与裂纹线的夹角）在制作试样时已经通过裂纹线与试样平台的位置关系确定,因此在实验中可以方便而准确地实施加栽。比较了纯Ⅰ型加载和复合型加载下压杆上记录的入射波、反射波和透射波的波形。采用实验与数值相结合的方法,将实验得到的动态载荷输入有限元程序,得到了纯Ⅰ型试样的动态断裂韧度和复合型试样的两种动态应力强度因子的时间历程。计算了加载角为15°的试样应力强度因子的复合比（KI（t）／KⅡ（t））,此计算值与文献结果吻合较好,验证了实验方法的有效性。     

飞机典型结构件的声疲劳实验研究

飞机典型结构件为蒙皮、框和长桁组成的双向双加筋的九格壁板结构.利用高声强行波管系统,以典型试件中心格的第一阶频率为中心、1/3倍频程为带宽的窄带随机谱激励,再现壁板结构的声疲劳破坏方式.通过原始状态的典型试件的两次预试验,发现了原典型结构件的设计缺陷.采用三种方式对原结构框的两端进行了支持加强,得到各种支持状态下的声疲劳破坏形式.     

水下航行体通气超空泡形态实验研究

在水洞中对航行体模型的通气超空泡形态及其影响因素进行了系列实验研究。在低速的情况下通过向空化器下游通入空气生成了超空泡。通过改变水洞速度、压力，通气参数，模型外形和状态产生了多种超空泡外形并研究了超空泡外形与空化器、空化数和通气参数之间的关系以及影响超空泡形状的因素，得出了有益的结论。对于下一步的研究工作具有指导意义，对于航行体超空泡外形控制技术的研究具有重要参考价值。     

爆轰波在阻尼管道中声吸收的实验研究

实验旨在研究气相爆轰波在阻尼管道 (管壁上衬有吸收材料 )中传播时的衰减现象。先是在光滑管壁的管道中产生稳定的具有胞格结构的爆轰波 ,然后使其通过专门设计的管壁上衬有吸收材料 (金属丝网或不锈钢纤维 )的阻尼段。利用高速摄影、压力传感器和烟迹技术等手段 ,记录和测试了阻尼段对几种混合气体爆轰波的传播速度、爆压及胞格结构产生的影响。实验分别在方管和圆管中进行。发现在某些条件下爆轰波可以被衰减成强爆燃。