超声波轴向应力仪的研制

本文叙述了用超声方法测量材料轴向应力的计算公式,介绍了超声波轴向应力仪的工作原理,并利用该仪器对M36×260高强度螺栓进行了轴向应力的测量。实验结果表明:该仪器的声时测量精度为10~(-10s),轴向应力的测量精度优于0.4kgf/mm~2(约3.9N/mm~2)。     

用同一个晶体管发射超声单脉冲和调制波的声速仪

一、工作原理用同一个晶体管发射超声单脉冲和调制波的声速仪的工作原理如图1所示.图1中脉冲回波重合法时序逻辑电路周期性地产生发射同步信号,信号经开关K1选通后,分别被送往单脉冲形成电路或调制波形成电路,然后再经过开关K2送在发射电路.当电源切换开关K3将高压直流电压VH送入发射电路时,该超声波声速仪处于发射超声单脉冲波的工作状态,发射电路输出幅度很高、边沿很陡的电脉冲,经过输出高频插座去激励压电晶片产生单脉冲的超声波,压电晶片与电感构成一个调谐回路路.当电源切换开关K3转向另一侧,将低压直流电压VL送入发射电路,该声速…     

声波反射和折射中的一个問題

声波从第一媒貭垂直投射于第一媒貭和第二媒质的分界面时,一部分反射,另一部分透入第二媒质中(見下图)。当波在第二媒貭中传播至无限远处而沒有反射时,根据压強連續和速度連續的边界条件,可以推得声压透射系数为 p_2+/p_1+=2γ/γ+1。 (1)     

关於力学中三條守恒定律的適用範圍

在普通物理的教學中,講到力學中機械能守恆定律、動量守恆定律和角動量守恆定律的時候,我們對於這三條定律的適用範圍,往往不很强調或不很注意。我們摘引梁寶洪所譯的福里斯—季莫列娃普通物理學中的幾段有關的材料來看一下。在第一卷第66頁上有着關於動量不滅定律的敘述:“構成一封閉系統的各物體底動量底向量和,即這封閉系統底總動量向量,在整個的運動期間內保持不變”。而關於封閉系統的敘述則是“物體彼此之間相互作用,但不舆這系統外部的物體相互作用”。在93頁有着能底不滅和轉换定律的敘述:“對於一封閉的系統(外力之功等於零),當一切過程在這系統內部發生時,這系統底能量保持不變,在此情形下,能量可以從某種形式轉變為另一     

弯曲模式声波在充液井孔中的传播

本文由波动方程讨论了充液井孔中,弯曲模式声波在弹性和非弹性、无限大井壁介质以及有限大井壁介质情况下沿井轴方向的传播。数值计算了它们的相速度频散曲线和井孔的频率响应特性,计算了衰减正弦信号在井孔中激励的波形。利用PZT压电晶片的弯曲振动模式,制作了偶极子测井换能器,在混凝土浇注的人工模拟井中进行了测试,试验结果与理论计算结果作了对比。     

PULSE ECHO OVERLAP METHOD USING ELECTROSTATIC TRANSDUCERS

The pulse echo overlap method using electrostaic transducers for accurate measurement ofultrasonic velocity in solid media is discussed in this paper.Owing to the advantage of non-contactfor electrostatic transducers,the correction for coupling layer can be eliminated and the correct cyclicoverlap can be easily achieved,thus the performance of the echo measuring system is significanitlyimproved.In this paper the diffraction correction is calculated for the echo measuring system usingelectrostatic transducers,and an ultrasonic velocity measuring instrument and its transducers arealso described.The measuring results for several specimens of glass and aluminium show that themeasuring accuracy of transmission time in this system reaches 1/500 of RF period,that means themeasnring accuracy reaches 0.2 ns at 10 MHz.     

一个新型的T形耦合谐振光声腔

本文介绍一种工作于耦合谐振频率上的新型谐振式光声腔(T形腔)的设计及其性能.从腔内声压的积分表达式出发,用格林函数对耦合谐振腔的谐振频率作了理论计算,并对实际的T形腔的谐振频率作了数值计算和实验测定,结果表明两者良好吻合.在CO_2激光光声谱仪上,对T形腔性能的测量结果表明,耦合谐振光声腔有高达900左右的Ω值;并在T形腔的小腔的3λ/4开管谐振频率上,背景信号与光声信号是反相的,从而有可能简便而实时地记录下扣除了背景信号的光声谱。对甲醇及苯蒸气的浓度检测灵敏度分别为和     

一种光声检测材料热扩散率的新方法

本文介绍采用前表面激发的光声检测材料热扩散率的新方法及其检测原理。用该方法对纯铁、纯铜、黄铜、铝以及人造金刚石砂粒的热扩散率测定结果表明,它与通常背激发的光声技术和激光导热仪的测量结果是一致的。     

A NOVEL COUPLED RESONANT PHOTOACOUSTIC CELL(T-TYPE)

This paper describes the design and characters of a novel coupled resonant photoacoustic cell.It is called T-type cell,because it consists of two cylinders,one is thin and long,another is wide andshort.Its resonance frequencies are calculated on the basis of pressure integral expression in a cavityand Green's function.The coupled resonance frequencies of a prototype of T-cell are numericallyand are experimentally examined.The experimental and calculated results are in good agreement.When the length of the small cylinder equals to 3λ/4,another resonance occures.At this frequencythe background signal is in opposite phase with photoacoustic signal.Therefore it becomes possibleto record in real-time the PA spectra of samples(background signal having been subtracted).Itsdetection sensitivities for vapor concentration of C_6H_6 and CH_3OH have reached 7×10~(-8)/W HZ~(1/2)and 1×l0~(-8)/W Hz~(1/2) respectively.