中文摘要
超聲波是頻率在2×10 ～10 Hz的聲波，它廣泛存在于自然界和日常生活中。
超聲波測試把超聲波作為一種信息載體，它已在海洋探查與開發(fā)、無損檢測與評價、醫(yī)學(xué)診斷等領(lǐng)域發(fā)揮著不可取代的獨(dú)特作用。例如，在海洋應(yīng)用中，超聲波可以用來探測魚群或冰山、潛艇導(dǎo)航或傳送信息、地形地貌測繪和地質(zhì)勘探等。在檢測中，利用超聲波檢驗(yàn)固體材料內(nèi)部的缺陷、材料尺寸測量、物理參數(shù)測量等。在醫(yī)學(xué)中，可以利用超聲波進(jìn)行人體內(nèi)部器官的組織結(jié)構(gòu)掃描（B超診斷）和血流速度的測量（彩超診斷）等。
本實(shí)驗(yàn)簡單介紹超聲波的產(chǎn)生方法、傳播規(guī)律和測試原理，通過對固體彈性常數(shù)的測量了解超聲波在測試方面應(yīng)用的特點(diǎn)，通過對試塊尺寸的測量和人工反射體定位了解超聲波在檢驗(yàn)和探測方面的應(yīng)用。
Abstract
Ultrasonic is the sound wave which frequency ranges from 2×104Hz to 1012Hz . Its frequency is far above the range of human hearing, which is only about 20Hz to 18KHz. However, some mammals can hear well above this. For example, bats and whales use echolocation that can reach frequencies in excess of 100KHz.
In 1830, F. Savart produced the first man-made ultrasonic at the frequency of 2.4×104 with a gear wheel. In 1929 and 1935, Sokolov studied the use of ultrasonic in detecting metal objects. Mulhauser, in 1931, obtained a patent for using ultrasonic, using two transducers to detect flaws in solids. Firestone (1940) and Simons (1945) developed pulsed ultrasonic testing using a pulse-echo technique. After the World War II, instrumentation of ultrasonic testing got a rapid developments spurred by the technological advances from the 1950’s continue today. Especially through the 1980’s and continuing into present, computers have provided technicians with smaller and more rugged instruments with greater capabilities.
Ultrasonic has so many advantages that it is employed in a wide range of applications in research, industry and medicine. First of all, it is a elastic wave therefore it can transmit in the most types of materials and it can be used to investigate both their surfaces and their interiors, whereas light can just get through the lucid materials and Hertzian waves is unable to transmit in the conductive materials. Secondly, the energy of the ultrasonic is so concentrated and its diffuse angle is so small that it can focus the object accurately. Such advantage was made use of in materials metering, non- destructive testing, submarine navigation and the like.
There is widespread agreement among researchers and scientists that ultrasonic is still in its infancy. This is evidenced by the fact that there is a great deal which is still not known about the field and the continued rapid rate of progress on nearly all aspects of it. Among the keys to further progress will be advances in materials (particularly piezoelectric materials for the transducers), in electronics and in computers (for interpreting and enhancing the results). Improvements in performance will be accompanied by further reductions in cost and increased diversity in the applications, likely including the development of some completely new uses.