超声波探伤论文 超声波探伤毕业论文

1、II处相邻两缺陷在一直线上，其间距为11mm，小于12mm，作为一条缺陷处理。以两缺陷长度和作为其指示长度，即33mm。5.3 超声探伤缺陷评定 承压设备对接焊接接头检测一般用B级检测技术。由4.2.2中摘录的GB11345-89标准中关于缺陷评定的叙述及表5-2可的缺陷级别评定如表6-2所示。表5-2 缺陷级别评定缺陷 = 1 * ROMAN I = 2 * ROMAN II = 3 * ROMAN III级别 = 4 * ROMAN IV = 4 * ROMAN IV = 4 * ROMAN IV 由表5-2可知，板材共存在三处缺陷，等级均为 = 4 * ROMAN IV，不符合合格级别，

2、应进行焊缝返修。结论科技在发展，焊缝无损检测技术也在向着自动化、智能化和信息化的方向发展。但是，我们也应看到，针对我国当前的实际情况，手动人工超声波探伤仍是主要的探伤方法，且应用依然相当广泛。并且在实际的超声波探伤过程中，仍在不断涌现许多新问题。针对这些实际问题，在指导老师的悉心指导下，在前人成果的基础上，本文对焊接缺陷的超声波探伤技术进行了详细介绍，并通过钢板焊缝的超声波探伤实验详细讲述了超声波探伤的操作步骤、注意事项和等级评定标准。本课题着重做了以下工作：论述了过程设备制造工艺流程，并详细介绍了焊接过程中常见的缺陷和产生缺陷的原因。详细讲述了超声波探伤技术的原理、分类、评定等级和评定标准。

3、结合实验详细介绍了超声波探伤的操作步骤和注意事项，并对给定板材焊缝进行了现场探伤和等级评定，完成了焊缝超声检测报告和焊缝超声检测工艺卡。焊缝超声波检测作为检验焊缝质量的一种有效方法，其检测的可靠性和有效性还待进一步完善。由于超声检测的本身所固有的特点和局限性，在实际的无损检测中还须与其他检测方法配合使用。我们坚信，随着研究工作的进一步深入，此问题将会不断完善。参考文献1邹广华，刘强过程装备制造与检测北京：化学工业出版社，2003，7.32522邓辉，林树青.超声检测.第二版.北京：中国劳动社会保障出版社，2008.353郑津洋，董其伍，桑芝富.过程设备设计.北京：化学工业出版社，2005，5.

4、91954曹玉华. 焊接质量的超声波探伤无损检测.宁夏机械，2008，4：7375 5单宝华,喻言,欧进萍.超声相控阵检测技术及其应用.无损检测，2004，26（5）：2352386于建军.焊缝的超声波检测技术研究.硕士学位论文.新疆：新疆农业大学，2005致谢本毕业设计是在胡效东老师的精心指导和下完成的。值此论文完成之际，谨向胡老师及过控系各位老师致以最崇高的敬意和衷心的感谢！很庆幸自己在求学阶段遇到这样好的老师，师恩难忘。衷心感谢实验室刘梅老师给予我的指导和帮助。衷心感谢我的同学在论文的撰写和答辩的准备工作中给予我的热情的帮助。感谢山东科技大学为我们提供的良好的学习和生活环境。 最后，向审

5、阅本文的老师致以深深的敬意，并再一次真诚的感谢所有关心、帮助过我的老师、同学和朋友们! 在此，谨向你们致以最崇高的敬礼，谢谢！附录英文文献1.BASIC ULTRASONIC PRINCIPLESa.What is Ultrasound?Sound generated above the human hearing range (typically 20KHz) is called ultrasound. However, the frequency range normally employed in ultrasonic nondestructive testing and thickne

6、ss gaging is 100KHz to 50MHz. Although ultrasound behaves in a similar manner to audible sound, it has a much shorter wavelength. This means it can be reflected off very small surfaces such as defects inside materials. It is this property that makes ultrasound useful for nondestructive testing of ma

7、terials.The Acoustic Spectrum in Figure (1) breaks down sound into 3 ranges of frequencies. The Ultrasonic Fig.1b. Frequency, Period and WavelengthUltrasonic vibrations travel in the form of a wave, similar to the way light travels. However, unlike light waves, which can travel in a vacuum (empty sp

8、ace), ultrasound requires an elastic medium such as a liquid or a solid. Shown in Figure (2) are the basic parameters of a continuous wave (cw). These parameters include the wavelength ()and the period (T) of a complete cycle.b.Frequency,Period and WavelengthUltrasonic vibrations travel in the form

9、of a wave,similar to the way light travels.However,unlike light waves,which can travel in a vacuum (empty space),ultrasound requires an elastic medium such as a liquid or a solid.Shown in Figure(2)are the basic parameters of a continuous wave(cw).These parameters include the wavelength() and the per

10、iod(T)of a complete cycle.The number of cycles completed in one second is called frequency(f)and is measured in Hertz(Hz),some examples follow; 1 cycle/second= 1Hz 1000 cycles/second= 1KHz 1,000,000 cycles/second= 1MHzThe time required to complete a full cycle is the period (T), measured in seconds.

11、 The relation between frequency and period in a continuous wave is given in Equation (1).Eqn. 1 f = 1/Tc.Velocity of Ultrasound and WavelengthThe velocity of ultrasound (c) in a perfectly elastic material at a given temperature and pressure is constant. The relation between c, f, and T is given by E

12、quations (2) and (3):Eqn. 2 = c/f Eqn. 3 = cT = Wavelengthc = Material Sound Velocityf = FrequencyT = Period of timeTable 1 on page 40 lists the longitudinal and shear wave velocities of materials that are commonly tested with ultrasonics.d.Wave Propagation and Particle MotionThe most common methods

13、 of ultrasonic examination utilize either longitudinal waves or shear waves.Other forms of sound propagation exist,including surface waves and Lamb waves.The longitudinal wave is a compressional wave in whichthe particle motion is in the same direction as the propagation of the wave.The shear wave i

14、s a wave motion in which the particle motion is perpendicular to the direction of the propagation.Surface(Rayleigh)waves have an elliptical particle motionand travel across the surface of a material.Their velocity isapproximately 90%of the shear wave velocity of the materialand their depth of penetr

15、ation is approximately equal toone wavelength.Plate(Lamb)waves have a complex vibration occurring inmaterials where thickness is less than the wavelength ofultrasound introduced into it.Figure(3)provides an illustration of the particle motion versus the direction of wave propagation for longitudinal

16、 waves and shear waves.e.Applying UltrasoundUltrasonic nondestructive testing introduces high frequency sound waves into a test object to obtain information about the object without altering or damaging it in any way.Two basic quantities are measured in ultrasonic testing;they are time of flight or

17、the amountof time for the sound to travel through the sample and amplitude of received signal.Based on velocity and round trip time of flight through the material the material thickness can be calculated as follows:Eqn.4 T=Material Thicknessc=Material Sound Velocity=Time of FlightMeasurements of the

18、 relative change in signal amplitude can be used in sizing flaws or measuring the attenuation of a material.The relative change in signal amplitude is commonly measured in decibels.Decibel values are the logarithmic value of the ratio of two signal amplitudes.This can be calculated using the followi

19、ng equation.Some useful relationships are also displayed in the table below;Eqn.5 dB=20log10(A1/A2)dB=DecibelsA1=Amplitude of signal 1A2=Amplitude of signal 2f.Sensitivity and ResolutionSensitivity is the ability of an ultrasonic system to detect reflectors (or defects)at a given depth in a test mat

20、erial.The greater the signa that is received from thesereflectors,the more sensitive the transducer system.Axial resolution is the ability of an ultrasonic system to produce simultaneous and distinct indications from reflectors Iocated at nearly the same position with respect to the sound beam.Near

21、surface resolution is the ability of the ultrasonic system to detect reflectors located close to the surface of the test piece.2.ADVANCED DEFINITIONS AND FORMULASa.Transducer waveform and spectrumTransducer waveform and spectrum analysis is done according to testconditions and definitions of ASTM E1

22、065.Typical units are MHz for frequency analysis,microseconds for waveform analysis,and dB down from peak amplitude.Figure(4)illustrates waveform duration at the 14dB level or 20%amplitude of peak.The-40dB waveform duration corresponds to 1%amplitude of peak.Figure(5)illustrates peak frequency,upper

23、 and lower-6dB frequencies and MHz bandwidth measurements.The relation between MHz bandwidth and waveform duration is shown in Figure(6).The scatter is wider at-40dB because the 1%trailing end of the waveform contains very little energy and so has very little effect on the analysis of bandwidth.Beca

24、use of the scatter it is most appropriate to specify waveforms in the time domain (microseconds)and spectrums in the frequency domain.The approximate relations shown in Figure(6)can be used to assist in transducer selection.For example,if a-14dB waveform duration of one microsecond is needed,what fr

25、equency transducer should be selected?From the graph,a bandwidth of approximately 1 to 1.2MHz corresponds to approximately 1 microsecond-14dB waveform duration.Assuming a nominal 50%fractional bandwidth transducer, this calculates to a nominal center frequency of 2 to 2.4MHz.Therefore,a transducer o

26、f 2.25MHz or 3.5MHz may be applicable.b.Acoustic Impedance,Reflectivity, and AttenuationThe acoustic impedance of a material is the opposition to displacement of its particles by sound and occurs in many equations.Acoustic impedance is calculated as follows:Eqn.6 Z=cZ=Acoustic Impedancec=Material So

27、und Velocity=Material DensityThe boundary betweeen two materials of different acoustic impedances is called an acoustic interface.When sound strikes an acoustic interface at normal incidence,some amount of sound energy is reflected and some amount is transmitted across the boundary.The dB loss of en

28、ergy on transmitting a signal from medium 1 into medium 2 is given by:Eqn.7a dB loss=Z1=Acoustic Impedance of First MaterialZ2=Acoustic Impedance of Second MaterialThe dB loss of energy of the echo signal in medium 1 reflecting from an interface boundary with medium 2 is given by:Eqn.7b dB loss=For

29、example:The dB loss on transmitting from water(Z=1.48)into 1020 steel(Z=45.41)is -9.13dB;this also is the loss transmitting from 1020 steel into water.The dB loss of the backwall echo in 1020 steel in water is-0.57dB;this also is the dB loss of the echo off 1020 steel in water.The waveform of the ec

30、ho is inverted when Z2Z1.Finally,ultrasound attenuates as it progresses through a medium. Assuming no major reflections,there are three causes of attenuation: diffraction,scattering and absorption.The amount of attenuation through a material can play an important role in the selection of a transduce

31、r for an application.c.Sound FieldThe sound field of a transducer is divided into two zones;the near field and the far field.The near field is the region directly in front of the transducer where the echo amplitude goes through a series of maxima and minima and ends at the last maximum,at distance N

32、 from the transducer.The location of the last maximum is known as the near field distance (N or)and is the natural focus of the transducer.The far field is the area beyond N where the sound field pressure gradually drops to zero.Because of the variations within the near field it can be difficult to

33、accurately evaluate flaws using amplitude based techniques. The near field distance is a function of the transducer frequency, element diameter,and the sound velocity of the test material as shown by Equation 8:Eqn.8 Eqn.8a N=Near Field DistanceD=Element Diameterf=Frequencyc=Material Sound Velocity=

34、Wavelength(Table 2 on page 40 lists the near field distances in water for manycombinations of transducer frequency and element diameter.)3.Desing cgaracteristics of transducersa.What is an Ultrasonic Transducer?A transducer is any device that converts one form of energy to another.An ultrasonic tran

35、sducer converts electrical energy to mechanical energy,in the form of sound,and vice versa. The main components are the active element,backing,and wear plate.b.The Active ElementThe active element,which is piezo or ferroelectric material, converts electrical energy such as an excitation pulse from a

36、 flaw detector into ultrasonic energy. The most commonly used materials are polarized ceramics which can be cut in a variety of manners to produce different wave modes. New materials such as piezo polymers and composites are also being employed for applications where they provide benefit to transduc

37、er and system performance.c.BackingThe backing is usually a highly attenuative,high density material that is used to control the vibration of the transducer by absorbing the energy radiating from the back face of the active element. When the acoustic impedance of the backing matches the acoustic imp

38、edance of the active element,the result will be a heavily damped transducer that displays good range resolution but may be lower in signal amplitude.If there is a mismatch in acoustic impedance between the element and the backing,more sound energy will be reflected forward into the test material.The

39、 end result is a transducer that is lower in resolution due to a longer waveform duration,but may be higher in signal amplitude or greater in sensitivity.d.Wear PlateThe basic purpose of the transducer wear plate is to protect thetransducer element from the testing environment.In the case of contact

40、 transducers,the wear plate must be a durable and corrosion resistant material in order to withstand the wear caused by use on materials such as steel. For immersion,angle beam,and delay line transducers the wear plate has the additional purpose of serving as an acoustic transformer between the high

41、 acoustic impedance of the active element and the water,the wedge or the delay line all of which are of lower acoustic impedance.This is accomplished by selecting a matching layer that is 1/4 wavelength thick(/4)and of the desired acoustic impedance (the active element is nominally 1/2 wavelength).T

42、he choice of the wear suface thickness is based upon the idea of superposition that allows waves generated by the active element to be in phase with the wave reverberating in the matching layer as shown in Figure(4). When signals are in phase,their amplitudes are additive,thus a greater amplitude wa

43、ve enters the test piece.Figure(12)shows the active element and the wear plate,and when they are in phase.If a transducer is not tightly controlled or designed with care and the proper materials and the sound waves are not in phase,it causes a disruption in the wavefront.英文文献译文超声波的基本原理a什么是超声波？超出人类听觉

44、范围的声波（通常高于20KHZ）称为超声波。然而用于超声无损检测及厚度测量的超声波频率范围通常是50100KHz。虽然超声波的表现方式与声波类似，但它的波长很短。这意味着它可以反映很小的表面，如材料内部的缺陷。正是这一特性使得超声波在无损检测中得到了广泛的应用。如图1，声波频谱图可分为3个范围。超声波又可进一步分为3部分。频率、周期及波长 超声波波形的振动传播方式与光波的传播方式类似。然而不同于光波可以在真空中传播，超声波的传播需要一种弹性介质，如液体或固体。如图（2）是连续波的基本参数。这些参数包括波长和周期。一秒内完成的周期数称为频率，用Hz为单位计量。如下几个例子：1周期/秒=1Hz10

45、00周期/秒=1KHz1,000,000周期/秒=1MHz完成一个整波所用的时间称为周期，用秒为单位。周期和频率的关系如连续波方程（1）所示。方程.1 1f =1/T超声波波速和波长超声波波速(c)在理想的弹性材料，特定温度和特定压力下是不变的。C、f、和T之间的关系如方程2，3所示：方程.2 =c/f方程.3 =cT=波长c =材料声速f=频率T =周期40页附表一列出了经常使用超声波检测的材料的纵波和横波波速。波的传播和粒子的运动超声波检测探伤最常用的是纵波探伤和横波探伤。同时朝声检测中也存在其他类型的波。包括表面波和兰姆波。(1)纵波是指传播方向和介质粒子振动方向相同的波。横波是指传播方

46、向和介质粒子振动方向垂直的波。表面波瑞)(一个椭圆质点运动和穿越表面形成一层材料他们的速度大约90%的剪切波速的资料他们的穿透深度,大约等于一个波长。 (4)板波发生在一个复杂的振动在材料的厚度小于波长超声引入。图(3)展示了一个质点运动与方向的纵向波和波传播的横波传播速度快。a.超声波的应用介绍了超声无损检测高频声波进入测试对象来获取信息的对象不改变或损坏以任何方式两个基本量测的超声波检测;他们的飞行时间或时间对于声音穿越样品和振幅对接收信号一种基于速度往返传播时间通过物质材料厚度计算方式如下:方程.4 T =材料的厚度,c =材料声速传播时间。测量的相对变化信号振幅可用于测量尺寸瑕疵或衰减

47、的材料在信号幅值的相对变化通常是用分贝表示分贝值对数比的两种信号振幅这可以用下面的公式计算出一些有用的关系也显示在表。方程.5 dB = 20log10(A1 / A2)。dB =分贝,A1 =振幅的信号1 A2 =振幅的信号2b.灵敏度和分辨率 灵敏度是一种超声检测谐振(或缺陷)在某一特定深度对测试材料更多的信号,收到这些反射更敏感的传感系统。 轴分辨率超声波体系的能力产生同步和鲜明标志Iocated从反射几乎相同的位置时的声音柱。 近近场的判断是有能力的超声波检测反光位于靠近被检测面的测试片。附加的定义和公式a.传感器波形及频谱 传感器波形及频谱分析是根据试验条件和定义的ASTM E1065典型的单位。兆赫频率分析的基础上,进行了分析,并对波形微秒的数据库从amplitude.Figure高峰期间(4),说明了在14dB波形的峰值水平或20%amplitudeThe-40dB 1%amplitude对应的波形持续peak.Figure(5),上部和lower-6dB峰频率测量频率和兆赫带宽兆赫之间的关系的带宽和波形时间是显示在图(6).由于广at-40dB散这个1%trailing结束的波形只含有少量的能源等几乎没有影响分析的带宽因为它是最合适的分散在指定的时