温度对超声波在16MnR钢中传播速度的影响

研究了温度变化对超声波探伤定位的影响,以及在20~450℃范围内,超声波在16MnR钢内的横波传播速度规律。应用最小二乘法拟合了3种速度规律关系式,并对其进行了比较,得出精确计算横波声速拟合公式VT=3253.31-1.8114T+1.18193×10-2T2-3.51474×10-5T3+3.05267×10-8T4。同时得出了由于热膨胀造成的试件半径变化对速度测量误差的影响在10-1mm量级,对缺陷位置和尺寸的影响不大。给出了实际波速、量程修正和误差幅度关系式。分析了由于温度变化造成的弹性模量、泊松比和密度的变化对速度变化的影响,得到了超声波在高温钢种下的理论修正公式。     

高温超声横波检测在压力容器焊缝缺陷检测运用研究

本文主要研究的是化工压力容器高温超声横波检测技术。针对化工压力容器大多数是在高温、高压、低温、疲劳及腐蚀性介质等苛刻工况下运行,在生产和使用中的失效形式比较复杂的现状,本提出了一种高温超声横波检测方法,其在压力容器焊缝缺陷检测具有一定的运用价值。     

高温作用下牺牲混凝土的损伤演化

以掺加/不掺加聚丙烯纤维的核电牺牲混凝土为对象,研究了不同温度作用下牺牲混凝土的力学性能和损伤演化规律。采用超声波检测技术,得到不同温度作用下牺牲混凝土试件中的超声波波速。根据损伤定义和应力波理论,得到牺牲混凝土损伤与其超声波波速之间的关系,最终建立了不同温度作用下牺牲混凝土的损伤演化模型。结果表明:在25~400℃时,不掺加聚丙烯纤维的牺牲混凝土试件的残余抗压强度均高于掺加纤维的试件的残余抗压强度,600~1 000℃时则呈现相反趋势;高温作用下,聚丙烯纤维的掺加对在牺牲混凝土中传播的超声波波速具有双重效应——正效应和负效应,在200~1 000℃时,负效应起主导作用;掺加/不掺加聚丙烯纤维的牺牲混凝土的损伤随温度演化结果一致,在高温作用下牺牲混凝土损伤随温度演化符合Weibull分布,该损伤演化模型可以用于高温作用下牺牲混凝土损伤分析以及核灾难后评估鉴定。     

换热器中介质温度对超声波传播特性的影响

在超声波防除垢试验台上,通过实验研究温度对除垢超声波传播特性的影响。保持液体流速、超声波发射频率和功率恒定,测量不同温度下换热管测点1和测点2处声强的大小,分析超声波声强随温度变化的规律,确定介质温度对换热管道内超声波传播特性的影响。结果表明:实验温度在25～55℃范围内时,超声波衰减随温度的升高而减小;实验温度在55～75℃范围内时,超声波衰减随温度的升高而增大。     

转化炉炉管水浸超声检测应用研究

转化炉炉管作为转化炉中的关键设备,既充当换热器又充当反应器,材料通常为HP40或HP40Nb,在工作过程中最高温度可达到1000℃左右,经过长时间的高温蠕变会逐渐产生裂纹。炉管表面有杨梅粒子涂层,常规检测方法无法对炉管进行检测。本文对转化炉炉管的水浸超声检测方法进行了相关研究。研究发现水浸超声检测灵敏度较高,能准确记录整根炉管超声波信号高度的变化;并且超声波衰减也可能是因为炉管发生了材质劣化。     

超声波对水垢形成过程影响的准静态实验研究

在极低的工质循环流速下进行超声波处理硬水实验,实时测量了超声处理后硬水钙离子浓度和电导率的变化,考察了超声波频率、初始硬度、温度对于硬水水质的影响。结果表明,准静态下超声波作用能加快溶液中碳酸钙初级晶核生成速度,使溶液硬度降低,电导率减小。初始硬度越大,温度越高,超声波结垢作用越明显。     

压力管道未焊透超声波检测的探头选择

未焊透是压力管道中最常见的危害性缺陷,超声波检测是压力管道检验中发现和评价未焊透的主要手段。闸述了压力管道未焊透超声波检测的现状和存在的主要问题,认为斜探头参数的合理选择是保证检测质量的关键。分析了斜探头晶片尺寸、探头频率、折射角(K值)、斜探头前沿长度对超声波检测可靠性的影响,计算出典型参数的平面单晶横波探头的声场特性值,提出了压力管道未焊透超声波检测横波探头的选择原则。     

超声波对固定化辣根过氧化物酶活性影响研究

为了研究超声波对固定化酶活性的影响,以固定化辣根过氧化物酶为对象,研究了不同超声波处理条件(超声功率,超声时间)以及超声条件下催化体系的pH、温度对固定化酶活性的作用。同时对超声波处理后固定化酶活的重复利用性进行测定。结果表明,超声波处理对提高固定化酶在高温、强酸碱条件下催化活性有一定帮助,最佳处理条件为:超声波功率50 W,超声时间30 min,pH 8,温度35℃,在此条件下,与未经超声波处理相比,固定化酶活性提高了17.6%,固定化酶重复利用性增强,经7次使用后,固定化酶催化活性是未经处理的1.8倍。     

碳纤维增强碱激发粉煤灰矿渣混凝土的高温损伤研究

本文以碳纤维、粉煤灰、矿渣、氢氧化钠、硅酸钠等为原料,制备了碳纤维增强碱激发粉煤灰矿渣混凝土(CFSC),通过抗压强度试验及超声波检测,研究了不同温度作用后CFSC的损伤特性.结果表明:高温后CFSC的抗压强度及超声波检测声速随加热温度的升高不断减小,掺入碳纤维对CFSC的温后抗压性能具有一定的增强效果,且增大纤维掺量可使同一高温下CFSC声速降幅减小;高温后CFSC抗压强度与声速间具有明显的二次多项式关系;高温导致CFSC的测试声波波形及主频发生显著变化,随着温度的升高,波形形态较常温产生畸变,声波主频不断降低,掺入碳纤维后CFSC的主频降幅较不掺纤维时有所减缓.     

温度对管道超声导波检测定位的影响规律研究

本文主要介绍了温度对管道超声导波检测技术缺陷定位判定的影响,研究分析了温度对超声导波传播的作用原理及影响规律,并针对该问题提出了温度引起的缺陷定位误差修正方法。     

Nondestructive and in‐situ monitoring of mechanical property buildup in epoxy adhesives for civil applications by propagation of ultrasonic waves

Ultrasonic inspection for nondestructive analysis is already widely applied to the control of structural integrity of concrete, presenting among other advantages the reliability, the simplicity and low costs. Although ultrasonic testing are mainly used for nondestructive evaluation of defects, it may be also applied to follow the changes of mechanical properties occurring in a material which evolves in time, such as during the crosslinking of thermosetting resins. These time dependent properties may be measured by longitudinal and shear ultrasonic velocity operating by pulse‐echo and/or through‐transmission methods. In this work, ultrasonic wave propagation has been applied to the monitoring of the progress of the curing reaction of an epoxy adhesive for civil applications. The data have been collected in isothermal conditions on the neat resin, as well as in a coupled system concrete‐resin‐concrete. The measurements of longitudinal and shear velocity have been used for the calculation of Young and shear moduli. The change of velocity during cure must be considered a powerful tool for the measurement of the progress of ambient temperature cure reactions like in the case of adhesives for civil applications.     

Ultrasonic Velocity Technique for Nondestructive Quantification of Elastic Moduli Degradation during Creep in Silicon Nitride

The ultrasonic velocity technique was used for nondestructive quantification of creep damage during interrupted tensile creep tests at 1400°C in an advanced silicon nitride to investigate the possibilities of this technique for creep damage monitoring in ceramic components. The longitudinal and shear wave velocities, Poisson's ratio, and Young's, shear, and bulk moduli linearly decreased with strain. Precise density change measurements indicated a linear relationship with a coefficient of proportionality of 0.69 between the volume fraction of cavities and tensile strain. Cavitation was identified as the main creep mechanism in the studied silicon nitride and the reason for ultrasonic velocity and elastic moduli degradation. The measurement of just the longitudinal wave velocity changes was found to be sufficient for quantification of cavitation during creep. The capability of the ultrasonic velocity technique for simple, sensitive, and reliable nondestructive monitoring of creep damage during intermittent creep was demonstrated in silicon nitride.     

导波在石化企业高温管道腐蚀检测中的应用

超声导波检测应用的范围与导波激发的原理有关,根据高温管道的特点,选择采用磁致伸缩效应作为高温管道超声导波检测的激发原理。介绍了采用新型基于磁致伸缩效应的导波仪MsS 3030以高温管道的导波检测为例进行的现场检测,同时利用现场测厚验证导波检测的可靠性。结果证明,基于磁致伸缩效应的导波检测可以实现高温管道的在线检测,能有效发现腐蚀等面积缺陷,具有广泛的应用前景。     

A Novel Method of Predicting Ultrasonic and Elastic Properties of Isotropic Ceramic Materials after Sintering from the Properties of Partially Sintered or Green Compacts

A novel method for predicting the porosity dependence of ultrasonic and elastic properties of isotropic ceramics after sintering based on the properties of green or partially sintered compacts has been proposed. The method is based on the observation that the ratio of ultrasonic shear wave to longitudinal wave velocity is a function of porosity only and varies linearly with the longitudinal wave velocity. It is also shown that the predicted trend of variation of Poisson's ratio with porosity agrees with the predictions of the Mori–Tanaka mean field approach. The method can be used as a quality control tool during the preparation of ceramic materials.     

Geometrical dependence of viscosity of polymethylmethacrylate melt in capillary flow

The shear viscosity of polymethylmethacrylate (PMMA) melt is particularly investigated by using a twin‐bore capillary rheometer at four temperatures of 210, 225, 240, and 255°C with different capillary dies. Experimental results show that the geometrical dependence of shear viscosity is significantly dependent on melt pressure as well as melt temperature. The measured shear viscosity increases with the decrease of die diameter at lower temperatures (210 and 225°C) but decreases with the decrease of die diameter at higher temperatures (240 and 255°C). Based on the deviation of shear viscosity curves and Mooney method, negative slip velocity is obtained at low temperatures and positive slip velocity is obtained at high temperatures, respectively. Geometrical dependence and pressure sensitivity of shear viscosity as well as temperature effect are emphasized for this viscosity deviation. Moreover, shear viscosity curve at 210°C deviates from the power law model above a critical pressure and then becomes less thinning. Mechanisms of the negative slip velocity at low temperatures are explored through Doolittle viscosity model and Barus equation, in which the pressure drop is used to obtain the pressure coefficient by curve fitting. Dependence of pressure coefficient on melt temperature suggests that the pressure sensitivity of shear viscosity is significantly affected by temperature. Geometrical dependence of shear viscosity can be somewhat weakened by increasing melt temperature. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 3384–3394, 2013     

基于超声衰减和声速动态监测石蜡的相变过程

为研究石蜡在相变过程中内部结构和状态的改变特性,用中心频率为5 MHz的脉冲式超声波动态测量石蜡的相变过程,采集并分析不同升降温速率下的声速和声衰减信号的变化规律,结果与差示扫描量热仪(DSC)测量的热力学性质比较,并拍摄石蜡溶解过程的图像为辅助,探讨了二者由于测量原理不同导致的差异和特点。结果表明,两种方法均得到约50℃的初凝点,且二者信号反映的相变规律一致,表明利用声衰减和声速能够较好的表征石蜡在相变过程中的声学特性。超声可能成为一种新的蜡化物性质原位测量手段。     

Structural and Mechanical Properties of Fats Quantified by Ultrasonics

Since the velocity of an ultrasonic wave through a material depends on its density, bulk modulus (K), and shear modulus (G), a new approach to determine the shear elastic modulus and the mass fractal dimension (D) in a fat crystal network was developed. An ultrasonic chirp wave containing a range of frequencies and amplitudes, was used to estimate the structural and mechanical properties of palm oil based fats, crystallized under shear at three different temperatures (20, 25, and 30 °C). Considering the fat crystal network as a two-phase system (i.e. liquid and solid fat) the velocity of sound in both phases was obtained separately, assuming that the speed of sound in the oil phase was inversely dependent on the temperature. A constant shear modulus for the solid fraction was obtained experimentally by rheology, which was independent of the sample’s nature. These parameters were used for the determination of sample compressibility and its corresponding shear modulus by ultrasonic velocimetry. In addition fractal dimensions (D) were determined by using the relationship of the shear elastic modulus (G) to the mass fraction of the solid fat (φ) in a weak-link regime. The obtained results are comparable and consistent with previously reported fractal dimension values. This method allows online determination of the shear modulus of fats and could be potentially applied for quality control purposes in manufacturing.     

Effect of different types of carbon black on the mechanical and acoustic properties of ethylene–propylene–diene rubber

The effects of the incorporation of different types of carbon black as fillers on some selected physical and mechanical properties of ethylene–propylene–diene rubber (EPDM) based compounds were studied with the results of density, ultrasonic wave velocity, and tensile measurements. Ultrasonic wave velocities (both longitudinal and shear) were measured at frequencies up to 4 MHz at room temperature. The density, ultrasonic attenuation coefficient, and tensile strength results showed that rubber mixes containing general‐purpose furnace (GPF) black at a concentration of 25 phr had the best physical and mechanical properties. These results were interpreted to be due to the better compatibility of GPF black, which, because of its particle size and structure, filled the interstitial spaces in EPDM and provided better reinforcement of the elastomer. The use of a nondestructive technique such as ultrasonic measurement presents a new possibility for testing rubber and plastic products more efficiently. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

超声波H_2O_2在线式浓度计的研制

引　言Ｈ2 Ｏ2 在生产过程中 ,其质量分数变化于 0～52 %之间 ,此变化对Ｈ2 Ｏ2 生产的产量、质量、能源的消耗等技术经济指标都有直接的影响 .Ｈ2 Ｏ2浓度的在线检测一直是Ｈ2 Ｏ2 在生产和控制中的一项难题 .本文通过一套由微机控制的Ｈ2 Ｏ2 在线式超声波浓度计测定了质量分数为 0～ 52 %、温度为 10～50℃的Ｈ2 Ｏ2 溶液的超声波速度 ,计算了超声波速度、温度和浓度间的相互关系 ,为Ｈ2 Ｏ2 溶液浓度的超声在线检测提供了依据 .利用三者关系制成的超声波Ｈ2 Ｏ2 在线式浓度计在生产中取得了良好的测量效果 ,精度优于 0 .5% .1　仪　器超…