基于TDC的L_(CR)波切向应力检测方法的研究

基于固体中声速与应力的关系以及临界折射纵波(critically refracted longitudinal wave,LCR)的产生机理,提出一种利用LCR波从表面检测物体内部切向应力的实施方法,并对测量系统的硬件结构和工作原理进行详细阐述。针对应力改变导致的LCR波传播时间的微量变化,系统采用基于逻辑门绝对传输时间原理工作的"时间—数字转换器"(time to digi-tal converter,TDC)来满足高精度的时间间隔测量要求。在测量过程中采用"单端发射—双端接收"的布局模式进一步降低测量误差,以提高应力检测的精度。     

用临界折射纵波测量切向应力时的影响因素研究

研究了基于声弹性理论,利用临界折射纵波(critically refracted longitudinal wave,LCR波)从构件表面测量内部切向应力时的几个关键问题。应力测量接收到的波形非常复杂,其他的波形影响了对LCR波的识别,相关的影响因素也很多,包括楔块角和试块厚度的影响,进行了这两影响因素在LCR波传播中的对比实验,以构建适合测量切向应力的模型系统,达到对各影响因素优化组合的目的。     

基于水平剪切波声弹特性的矩形管轴向应力检测方法与试验研究

矩形管作为一种非典型波导结构,导波在其中的传播特性较为复杂,不便于利用其特有的模态进行检测。为实现矩形管结构应力的在役检测,基于特征频率法计算了水平剪切波SH_0模态的声弹特性,搭建了矩形管轴向应力评估检测系统。针对试验加载条件,利用有限元法分析受轴向拉伸矩形管的应力分布情况,以合理布置SH_0模态EMAT传感器,并对矩形管在承受不同拉应力条件下的声弹常数进行了试验研究。试验结果表明:矩形管中SH_0模态的试验声弹常数与理论计算结果的比值为0.592 6,其声弹效应受材料织构效应影响较弱,通过应力评估误差结果可发现,SH_0模态在低应力区域误差较大,当应力低于100 MPa时,应力偏差普遍在20 MPa以上;而在高应力区域偏差可稳定在10 MPa左右,结果表明基于SH_0模态声弹效应可以预估矩形管结构应力是否超载。     

基于声-超声技术的钢丝绳强度检测方法的研究

简述了钢丝绳检测目前存在的一些问题,介绍了声一超声检测的发展及现状,提出了基于声-超声检测技术和拉断试验来推断钢丝绳破断拉力的方法,着重介绍其系统、原理及检测方法.     

航空透明件表面应力声弹检测方法的实验研究

针对航空透明件的特点,本文简要地导出了其表面波传播速度与表面应力之间的一般关系,提出了声时差测定技术,建立了平面声弹性实验系统,并给出了试件（航空有机玻璃）声时差与应力之间的经验关系式。     

窄板无损检测用水平剪切波电磁声传感器的研制

低阶水平剪切波具有的几个特点使得它特别适合应用于结构大范围无损检测。通过对换能器几何结构的设计,电磁声换能器能实现多种不同模态导波的激励,如板中的兰姆波和水平剪切波,但电磁声换能器的性能受其结构参数影响很大。为实现磁铁阵列式电磁声换能器的性能评价,开发一种用于换能器远场周向声场分布计算的线源分布模型,对具有不同几何参数的电磁声换能器的性能进行数值计算,如磁铁数量、磁铁周期、线圈的内外径等。这些参数对激励出的SHO波的指向性有很大影响,主要表现在主瓣及旁瓣的幅值及宽度方面。根据数值分析结果,为获得较好的指向性对换能器的结构参数进行优化设计。将优化设计研制出的换能器用于窄板结构无损检测,结果表明窄板的侧边界对SHO波的传播基本没有影响,可用于窄板结构的无损检测。提出可预测出磁铁阵列式电磁声换能器的声场分布并用于换能器参数优化的线源分布模型。     

基于倒置声学黑洞的弹性波汇聚检测研究

传统的嵌入式声学黑洞(ABH)以材料的幂律裁剪方式达到阻抗的变化,实现弹性波的汇聚或控制,但同时也破坏了材料本身结构、减小了材料的刚度,限制了其在检测领域作为增敏结构的应用。本文提出一种倒置粘贴式的ABH结构,在一定范围内其厚度变化符合幂律衰减规律,尺寸小巧,易于粘附于被测物体表面而不破坏被测物。有限元仿真结果显示,倒置ABH在中高频激励下在圆心附近有着7倍左右的弹性波汇聚效果。激光多普勒测振仪扫描测试表明,倒置ABH结构具备良好的弹性波汇聚效果,可将弹性波放大2～4倍。将光纤布拉格光栅(FBG)粘贴在该倒置ABH表面,采用强度解调,构成具有汇聚放大作用的弹性波传感器,在无损检测等方面具备重要的应用价值。     

基于磁致伸缩效应的钢管缺陷检测实验研究

根据铁磁体具有磁致伸缩特性,提出一种基于磁致伸缩效应的钢管无损检测技术。对其检测原理和系统设计方案作了介绍,并对样本管进行了有缺陷和无缺陷的模拟试验,分别给出了所获得的信号。实验结果表明．该检测技术对钢管缺陷检测是可行的,而且检测灵敏度比较高,安装单个传感器即可对很长段钢管进行检测。     

电磁超声单向应力横纵波联合测量方法研究

针对单向应力检测时厚度不均匀及拉伸变形等严重影响应力检测精度的难题,提出一种电磁超声横纵波联合测量单向应力的方法.通过基于洛伦兹力换能机理,优化设计出电磁超声纵波与横波探头,可有效提高回波信号的信噪比与幅值大小.分析了纵波与横波应力-声时差关系,建立了横纵波联合的单向应力电磁超声测量模型.利用自制的铝合金7075螺栓模...     

三波谐波齿轮传动柔轮应力分析

根据弹性理论 ,分析了三波谐波齿轮传动柔轮应力 ,推导了柔轮应力计算公式 ,并通过实例验证了公式的正确性 ,为三波谐波齿轮传动的进一步研制、开发提供了理论依据     

新型应力波铆接设备研制中若干问题探讨

本文分析了飞机制造对应力波铆接技术的需求和我国应力波铆接设备存在的问题,指出了研制新型应力波铆接设备需要解决的问题,提出了解决方案。     

Damage detection of concrete piles subject to typical damage types based on stress wave measurement using embedded smart aggregates transducers

Concrete piles are the most common types of foundation structures. Pile damages, such as fractures, cracks, mud intrusion and secondary concrete pouring, are the leading causes of pile structural failure, which may directly result in casualties and economic loss. It is desirable to develop a monitoring system that can detect these pile damages. In this paper, embedded piezoceramic-based smart aggregates transducers along with the active sensing approach are developed to detect common types of pile damages, including crack, partial mud intrusion, secondary pouring, and full mud intrusion, based stress wave measurement. With the active sensing approach, one smart aggregate is used as an actuator to generate a stress wave that will propagate along the pile, and other smart aggregate(s) will measure the propagating wave. All damages, which introduce new interfaces and discontinuities, attenuate the stress wave propagation. The attenuations of the stress waves based on different pile damages were compared by the received sensor signal in time domain. A wavelet packet-based energy analysis was used to develop an energy index to assist the detection of damages. Experimental results demonstrated the feasibility that the proposed approach can detect all four types of common damages associated with concrete piles.     

A study of the development of the stress optic law of photoelastic experiment considering residual stress

Photoelastic experiment has two significant problems. The first problem is manufacturing a model specimen for complicated shapes of structures. The second problem is residual stress contained in the photoelastic model material. In this paper, the stress optic law that can be effecitvely used on photoelastic model materials with residual stress is developed. By using the stress optic law as developed in this research, we can obtain good results in photoelastic experiments using model material in which residual stress is contained. It is assured that the stress optic law developed in this research is useful. Therefore, it is suggested that the stress optic law considering residual stress can be applied to the photoelastic experiment for the stress analysis of the composite materials or bi-materials in which the residual stress is easily contained.     

激光波高测量中示踪粒子性能分析

激光测量流体波动的波面高度,其基本原理是将激光投射到流体表面,通过计算投射距离,反演出波面高度。由于投射目标是气液的界面,,因此需要在接收激光投射的目标流体表面加用反射物质,以正确显示波面位置。通常采用反射示踪粒子撒播在被测流体表面,这是波高测量系统中的重要组成部分。本文通过对比不同示踪粒子反射性能的实验结果,分析所测示踪粒子的效果,对不同示踪粒子的特点、存在问题给出鉴定与讨论,并归纳出良好的波面反射示踪粒子应具备的特性。特别指出在气液交界面不宜使用气泡为示踪粒子及其原因。     

微机在压力容器应力测试中的应用

针对压力容器传统应力测试方法所存在的弊端,采用软硬件相结合的滤波方法,开发了以计算机为核心的应力自动测试系统,该系统可有效地消除系统噪声等污染源的影响,成功实现了对微弱信号的自动采集、处理和输出。     

锻件超声波探伤中缺陷波和伪缺陷波的识别

在超声波检测中根据锻件反射底波与缺陷波的静态与动态渡形特点,可以识别锻件内部缺陷(气孔、夹渣、夹层、裂纹、白点)与伪缺陷(迟到波、三角反射波、61°反射波及其它杂波),对指导锻件生产具有重要意义.     

一种新型面向制造工艺的测控实验装置的研究

介绍一种新型教学仪器,测控实验装置的设计思路及其组成,包括系统总体流程、系统组成、测量原理和误差分析。为了满足机械制造专业数控车削形位公差测量实验教学的需求,设计并制造了一套新型的测控工艺系统。测控系统包括测量和控制两大部分,实现对被测工件直径、圆度和圆柱度的在线测量,该装置具有结构简单、集成度高的特点,克服了传统教学设备的局限性。     

基于严格耦合波理论的亚波长光栅优化设计

亚波长衍射光栅的衍射效率不但与入射光的特性有关,而且与光栅结构和折射率等参数有关。采用严格耦合波理论对亚波长光栅的衍射效率公式进行了推导,对不同光栅结构参数(周期、槽深,占空比)和光栅脊、槽的折射率的亚波长衍射光栅的衍射效率进行了数值计算并用MatLab软件进行仿真模拟,光栅槽深与周期的比值为0.425,占空比为0.507,并且光栅脊、光栅槽的折射率为2.37时,得到具有最佳滤波和衍射效果的亚波长光栅的优化结构。     

Contact stress of O-ring under uniform squeeze rate by photoelastic experimental hybrid method

In this paper, photoelastic experimental hybrid methods using the external traction free boundary condition and that using the relative equation of two stress functions in contact problems are developed. The validities of these two methods are confirmed through experiments and discussions. Hertz’s contact theory and the two photoelastic experimental hybrid methods explained are applied to the analysis of the contact stress of an O-ring under 10% or 20% squeeze rate. The photoelastic experimental hybrid method using the relative equation of two stress functions in contact problems was found to be more effective. When the squeeze rates of an O-ring were 10% or 20%, the maximum of absolute σ _x was greater than the maximum of absolute σ _y , but was almost equal. Maximums of absolute τ _xy were 1/8 of absolute σ _x and 1/5 of absolute σ _x when the squeeze rates of the O-ring were 10% and 20%, respectively. This paper was recommended for publication in revised form by Associate Jai-Sug Hawong received a B.S. degree in Mechanical Engineering from Yeungnam Uni-versity in 1974. Then he received his M.S. degree and Ph.D. degree from Yeungnam University in Korea in 1976 and from Kanto Gakuin University in Japan in 1990, respectively. Prof. Hawong is currently a professor at the school of Mechanical Engineering at Yeungnam University, in Gyeongsan city, Korea. He is currently serving as an vise-president of Korea Society Mechanical Engineering. Prof. Hawong’s research interests are the areas of static and dynamic fracture mechanics, stress analysis, experimental mechanics for stress analysis and composite material etc.