PULSE ECHO OVERLAP METHOD WITH ALTERNATIVE TRIGGERING AND LIQUID VELOCIMETER

In this paper,the usual pulse echo overlap method for ultrasonic wave velocity measurement isdeveloped to pulse echo overlap method with alternative triggering.The principle of the method liesin that,when the first ultrasonic echo train,being given rise from the first transmitting pulse,is dis-played on an oscilloscope,the oscilloscope is triggered normally and synchronized with the transmittingpulse.But for the next echo train to be displayed,which is given rise from the second transmittingpulse,it will be triggered after a further time delay than that of the first one,which is equal to a roundtrip time of an ultrasonic pulse in the sample.Then the whole procedure is repeated again and againand on the oscilloscope a pattern of overlapped echo trains can be observd.The value of the delaytime can be obtained directly from a digital counter.By changing the scanning rate of the oscilloscopeand adjusting its triggering delay,any part of the overlapped pattern can be observed and studied. Based on this princi     

用脉冲重叠法精确测定表面声波的传播速度

本文提出采用交叉触发脉冲重叠法来精确测定材料的表面声波相速度.在一块样品上制作相同的三个叉指换能器A、B、C,在B与C之间的样品表面镀上金属膜.分别依次由A或C发射表面声波,而由其它两个换能器接收,即可测定表面声波的速度和速度变化.本文对LiNbO,石英及压电陶瓷样品进行了测量,测量精度估计约为±2m/s.     

熔石英的弹性模量和超声状态方程

利用“脉冲回波重合法”精密地测定了熔石英的2,3阶弹性模量C₁₁,C₄₄;C₁₂₃,C₁₄₄,C₄₅₆,由应变能对应变的级数展开,获得了由2,3,4阶弹性模量表示系数的熔石英超声状态方程。计算到3阶弹性模量的状态方程,与Bridgman的实验值比较,在压力增加时偏离增加。但当计入4阶弹性模量效应后,在熔石英发生状态改变前的区域,则两者之间符合得很好。 关键词：     

利用超声方法测定北京大钟寺永乐古钟的壁厚

利用超声测厚的方法第一次测定了北京永乐古钟的壁厚。由于采用了交叉触发脉冲重叠法以及适当调节工作频率,从而解决了测量中的实际困难。测量精度约为1.5％。还根据测得大钟的直径和密度,计算出大钟连同其挂钩在内的总重量约为46.6±1吨。     

利用超声脉冲回波重合法测定铌酸锂单晶弹性常数CijE和CijD

本文从基本的压电Christoffel方程出发导出三角晶系3m点群压电晶体弹性常数的表示式。并采用10MHz射频超声脉冲回波重合法测量了沿LiNbO₃不同对称方向传播的声速,结合e_ij和ε_ij⁵给出了LiNbO₃全部弹性常数C_ij^E和C_ij^D。它们是C₁₁^E=19.8 关键词：     

在PEO法声速测量中确定反射相移时延修正值与判别正确重合的方法

脉冲回波重合法(PEO法)目前已被公认为精密测定声速绝对值的最适用方案。为了使该法所具有的高精度测时能力起到实际效果,必须把其中所包含的反射时延、衍射时延等修正值相应地推求出来,加以修正。至今所广泛采用的反射时延计算方法,在实用上仍有所不便,在理论上也不尽准确,为此,本文进一步作了分析。 本文得出了包括衍射影响在内的反射相移时延修正值的计算方法。并提出了一种双晶片法实验测定修正值的方案。本文并提出取零相移周期增量Δг,作为实验常数,其值在一般情况下约为1.7~(ns),这样对实用就更为简便。 本文还提出了一种判别准确重合的方案。当准确重合时,测得声时一周期曲线的斜率为—h。     

DETERMINATION OF REFLECTION TIME DELAY AND CRITERION OF CORRECT OVERLAP IN ULTRASONIC WAVE VELOCITY MEASUREMENT WITH PEO METHOD

The Pulse-Echo-Overlap method(PEO method)has now been considered as the most adequatemethod for accurate measurement of the absolute value of ultrasonic velocity.For this accurate timemeasurement,it is essential to find the time delay and implement its corrections,e.g.the correction ofreflection time delay,the correction of diffraction time delay,etc.To overcome the inconvenience of thewidely used in practice method of reflection time delay calculation,and its imperfection in theory,a newcalculation procedure of the reflection time delay correction is worked out in this paper,and an experimentaldetermination method for its value by means of double crystal is suggested.This paper further suggests aparameter of the period increment of zero phase shift Δτ_r,and considers it as an experimental constant,whose value is about 1.7 ns in practical applications. Furthermore,this paper suggests a criterion of correct overlap.If the echoes are correctly overlapped,the slope of the curve of the ultrasonic wave tri     

THE ACOUSTIC POWER OF A PULSED SOUND

A metrological principle for pulse acoustic power,based on the envelope value of the acoustic pressure,isproposed.The deduced value may be defined as pulse acoustic power.Thus in combination with the existedterms for ultrasonic power,a complete system of the terminology can then be fulfilled.     

高温声速测量的激光遥测系统

不少年来人们一直在致力于探索高温下固体中超声声速的测量方法。其主要困难是测量所用的压电换能器能承受的温度有限制。为此而采取的措施有:加进足够长的耦合棒;选用能隔热的耦合剂;采用短时接触的传声方法;以及采用非接触方式的电磁声换能方法等。但所有这些仍未能使问题得到满意的解决。为此本文提出了一种全面激光遥测的方法,即用一套激光系统来激发超声脉冲,同时又用另一套激光系统来测量该声脉冲在样品中的传播时间,从而得出被测样品的超声声速。被测样品被密封在高温真空炉中,激光束则通过炉壁上的透光窗孔射入和射出。使测量装置与被测样品完全分离开,成为一套不受工作温度限制的遥测系统。     

1964年全国超声应用学术会议

由中国科学院技术科学部、中国电子学会超声专业委员会和北京科学技术协会联合主办的1964年全国超声应用学术会议,于1964年11月20日至28日在北京科学会堂举行。中国科学院声学研究所承担了这次会议的具体筹备工作。这次会议受到全国各地区各有关单位的重视和支持。上海地区为了参加这次会议曾于会前专门召开了超声诊断学术会议,推选出论文送到这次会上。