Electromagnetic Acoustic Transducer (EMAT) is an ultrasonic testing technique that generates sound in the part inspected instead of the transducer. Electromagnetic ultrasonic guided wave detection technology has problems such as low energy conversion efficiency and the great influence of environmental noise, resulting in low echo signal amplitude. When the two rows of permanent magnets are arranged non-parallel, the sound beam will be focused at the intersection point of the axes of the two rows of permanent magnets. This article uses this rule to optimise the design parameters of PPM EMAT. Distance amplitude curve (DAC) is a method of compensating. However, large-scale detection requires a flat DAC curve. In addition, the increase in the angle and length of the permanent magnets and the number of pairs of permanent magnets will improve the intensity of the defect wave indication intensity. However, the increase in the angle of the permanent magnets will increase the signal attenuation. After simulation and experiments, when the angle, length and number of permanent magnet pairs are 4 degrees, 25 mm and 8 pairs, the corresponding EMAT has the optimal axis radiation sound field and a smoother DAC, which is more suitable for stainless steel sheets, long-distance rapid guided wave detection.

A metal fatigue damage model is established in this study by employing real-time strain monitoring to evaluate the damage state of metal materials. The fatigue life simulation, based on crystal plasticity finite element analysis, establishes the constitutive relationship between strain and damage before microcrack initiation in the low-cycle fatigue state of aerospace aluminum alloy. Subsequently, a comprehensive analysis of the strain–damage relationship is conducted under various stress conditions. Electron backscattering diffraction analysis (EBSD) is used to examine the fatigue damage state of the grooved specimen before initiating fatigue cracks at various stages. This analysis validates the metal fatigue damage model proposed in this paper and is based on strain monitoring, contributing to the enhanced confirmation of the model’s accuracy.

To investigate small crack propagation and closure mechanisms in a powder metallurgy superalloy FGH4096 at room and high (600 degrees C) temperatures in air, meso-scale digital image correlation (DIC) was applied. CODs of small cracks did not increase monotonically as cracks propagated, which was related to the potential role of subsurface crack morphology. Roughness induced crack closure was found to be the leading mechanism at times. Oxidation induced crack closure was negligible at 600 degrees C, resulting from the oxidation-resistance of FGH4096. Crack opening stress intensity factors were generally higher at 600 degrees C, which ascribed to the higher level of plasticity induced crack closure.

SiCp/AZ91D magnesium matrix composites are widely used in the aerospace field, but there is less report on the distribution of SiCp particles in SiCp/AZ91D magnesium matrix composites by ultrasonic testing methods at home and abroad. In this paper, SiCp particle reinforced magnesium matrix composites with volume fractions of 0%, 2%, 4% and 6% were prepared by squeeze casting. In order to study the particle distribution in composite materials, ultrasonic velocity method, ultrasonic attenuation method, ultrasonic characteristic scanning imaging method and nonlinear ultrasonic testing method were used to study the dispersion of SiCp particles. The relationship between various acoustic parameters and SiCp volume fraction, and the difference of detection ability of different detection methods for SiCp particle distribution were explored and verified by experiments. The results show that ultrasonic characteristic scanning detection and ultrasonic velocity method can quantitatively detect SiCp macro agglomeration, ultrasonic attenuation method can have a good effect on characterizing both micro agglomeration and macro agglomeration, and nonlinear ultrasonic detection method is more sensitive to detecting SiCp micro agglomeration. When the particles are uneven, the mechanical properties are most affected, and the tensile strength is greatly reduced.

This work proposes a new global FD-RTM method to solve the problem of ultrasonic inspection of parts with complex geometric shapes. With this method, the frequency domain reverse time migration (FD-RTM) algorithm is used to adapt to the complex refraction of ultrasonic waves by the surface, while an interface solution algorithm based on tangent fitting is used to solve the interface position with high precision through the full matrix reception data. Based on high-precision interface information, a hybrid extrapolation algorithm and a situation-specific probe movement strategy are used to enable the probe to find the next sampling point according to the direction of the workpiece surface, allowing complex surface topography features to be identified without relying on the workpiece CAD drawing. This makes it possible to achieve the automated inspection of workpieces. To verify the proposed method’s effectiveness, an aluminum alloy model with side-drilled holes (SDH) is used. The geometry of the model consists of multiple convex and concave surfaces. By comparing the local FD-RTM imaging with images synthesized using the entire scan path, it is shown that gFD-RTM improved the imaging performance. Compared with FD-RTM, the average signal-to-noise ratio of gFD-RTM was increased by 20%, and the array performance index (API) was reduced by 70%, indicating effective detection coverage.

航空用金属材料中允许存在的缺陷越来越小,有时需要识别几十微米的夹渣缺陷.由于微小缺陷对声波的反射能力弱,常用的超声脉冲反射法的识别能力遇到瓶颈.该文利用超声干涉原理对微小缺陷进行识别.首先,理论分析入射波与微缺陷散射波的干涉机理;其次,采用有限元仿真方法分析了入射波经过微小缺陷后的波形变化,归纳出入射波与微缺陷散射波干涉规律.最后,以底波尾部干涉波列幅值作为成像参量对微小缺陷试样进行了成像检测,得到微小缺陷灰度图像.研究结果表明:该方法能够有效识别埋深5～80 mm、孔径为?0.1 mm的微小缺陷,当缺陷埋深小于5 mm时,能够有效区分横向间距1 mm、?0.2 mm的相邻微缺陷.

A new AlN film-based surface acoustic wave (SAW) device was explored for sensing strain at high tem-perature. AlN/metal/Si multilayer composite structure was proposed to construct the strain sensing chip, and the corresponding theoretical analysis on SAW propagation were performed by using finite element method (FEM). High-quality AlN piezoelectric thin-film was prepared by using magnetron sputtering on Si substrate, and Pt electrodes was then lithographically prepared to build the sensing chips with one-port resonator pattern operating at 607 MHz and 620 MHz. To compensate the temperature cross sensitivity and enhance the strain sensitivity, two sensing chips were positioned perpendicular on a ceramic package, then the differential frequency signal was extracted to evaluate the applied strain. A high-temperature strain testing platform was constructed to characterize the prepared strain sensor with orthometric structure, larger strain sensitivity of 0.84 ppm/mu epsilon at 550 degrees C in the range 0 - 500 mu epsilon and excellent temperature stability of 0.624 ppm/degrees C at the temperature range of 20-600 degrees C were achieved successfully. (C) 2021 Elsevier B.V. All rights reserved.

高端飞行器的可靠性往往受限于其发动机内部盘、板等构的结构强度和使用寿命,因此对这类部件的无损检测在制造业上具有巨大需求.超声检测作为一种应用广泛、高效、环保的检测方法,常常被应用于这类构件的检测中.但是,大厚度盘、板类构件内的微小缺陷反射能力弱,常规超声脉冲反射法无法进行有效检测.为实现大厚度盘、板类构件内部微小缺陷的识别和定位,采用共线异侧纵波混频法,通过和差频信号特征识别微小缺陷;研究缺陷埋深变化对混频效果的影响,通过测量和差频信号幅值变化,实现微小缺陷的深度定位.结果表明:该方法可有效识别7075铝合金中埋深80 mm的?0.2 mm横孔微缺陷,且可实现微小缺陷的深度定位.

直升机桨叶前缘加热组件为复杂曲面多层粘接结构,其粘接质量影响着桨叶乃至整机的安全.目前针对加热组件脱粘缺陷的超声检测,存在缺陷信号提取困难、单探头检测效率低等问题.针对存在的问题,研究了声波在多层介质中的传播规律,明确了结构中不锈钢/橡胶粘接层缺陷的识别方法,针对加热组件的复杂形状及扫查需要制作了阵列探头,对试样及实际加热组件进行了阵列成像检测.结果表明,采用阵列成像方法可检测加热组件不锈钢/橡胶层的脱粘缺陷,且缺陷形貌准确清晰.

在压力容器的超声检测中,为解决传统相控阵(PA)二维成像存在缺陷图像畸变,难以准确定性等问题,采用1种基于全聚焦法(TFM)的实时超声成像技术,使用一维线阵和二维面阵分别对孔等典型实际缺陷进行扫查,获得缺陷的二维和三维图像,从定量角度对比分析2者的准确度.结果 表明:该方法获得的三维图像测量误差在8％以内,具有更高的精确度和检出率,对于孔类缺陷的还原度更高,这对于缺陷检测与评估以及和特种设备的安全生产具有重要意义.

采用凸面相控阵探头检测双金属涡轮盘内部,根据小孔径涡轮盘结合面缺陷的结构特征、双金属涡轮盘的结构特点以及扩散焊工艺的连接特点等,首先在理论上分析了相控阵超声的声场特性,然后利用CIVA仿真软件设计了一种8阵元凸面相控阵换能器,通过选择合适的相控阵参数,有效地抑制了声束扩散,并在涡轮盘试块中获得了较好的聚焦效果.检测结果表明,设计的凸面相控阵超声探头能够实现对小孔径远距离的聚焦,聚焦效果良好,能对缺陷进行准确定位,检测精度可达1 mm平底孔当量.

A new configuration is proposed to improve the sensitivity and temperature stability of the surface acoustic wave (SAW) strain sensor by using a differential dual-chip structure. Each SAW chip with a one-port resonator pattern is prepared by depositing Al interdigital transducers (IDTS) on Y-cut quartz crystal using the photolithographic technique, and positioned orthogonally in the ceramic package. The opposite polarity of the strain sensitivity arises from the directivity of the strain tensor, and enhanced sensitivity will be expected by differencing the response from each sensing chip. Referring to the perturbation theory and finite element modeling (FEM), the sensitivity of the proposed sensor configuration is simulated and predicted, and confirmed by the wirelessly characterization. Excellent temperature compensation at 0 – 120 °C, higher sensitivity of 1.3 kHz/ $\mu \varepsilon $ , and satisfied linearity in a detection range of ± $500~\mu \varepsilon $ are achieved, and estimated detection limit reaches ± $0.7~\mu \varepsilon $ .

《声学检测》课程的线上教学突破了师生的时空限制,在特殊背景下的远程培训中具有重要应用价值.由于线上课程教学过程脱离直接接触,教学环境的稳定性、教学环节的连续性和实践教学的可行性等均存在一定问题.构建了由多个网络平台组成的多维线上教学平台,形成了由教学、考核、持续改进等3大模块组成的线上课程闭环教学体系,并建设虚拟仿真试验项目,实现了超声检测实验课的远程教学,基本解决了《声学检测》课程线上教学的主要问题,取得了良好的教学效果.

随着现代工业的发展,由于传统的二维超声成像检测反映的缺陷空间信息过于片面,已经不满足实际的检测需求.因此,超声三维成像检测技术应运而生.超声三维成像技术包括丰富的缺陷空间信息,对工件的无损评价有实质性的帮助.该研究借助可视化工具包(VTK)绘制平台,采用编码器触发的一维线阵换能器对工件进行全覆盖式扫查,将每个截面的相控阵线阵换能器扫查所得的A扫波形信号进行横向排列处理,绘制出各个截面的B扫图像.提出了最临近插值绘制法,将各个截面的B扫图像进行堆叠,重构工件的三维图像.通过对试块的三维成像结果表明,该成像方法能准确地反映缺陷的空间信息.

针对金属中微小缺陷在超声检测时回波信号较弱,利用时域回波信号对微小缺陷试块进行C扫描成像时图像噪声较大且信噪比较低的问题,借鉴医学超声影像领域中的背散射积分诊断技术,提出了一种通过计算缺陷回波信号的功率谱(PSD)和频域背散射积分(IBS)来表征微小缺陷的方法.在使用IBS对试块进行成像后发现成像的信噪比较时域成像有显著的提高,但图像出现了明显的网格化.对此提出了使用频域背散射补偿积分(IBSC)和频域背散射全宽带积分(IBSF)成像的两种改进降噪方法.实验结果表明,这两种改进的成像方法均能在保持成像具有较高信噪比的条件下抑制图像的网格化,但IBSC的计算量远小于IBSF,更适用于金属中微小缺陷的成像检测.

This work addresses the theoretical and experimental investigations of a Love wave based device employing waveguide structure of SiO2/36° YX-LiTaO3 for sensing icing process. The mass loading effect induced by the icing process modulates the acoustic wave propagation, and corresponding changes in device frequency can be collected to evaluate the icing process. The waveguide structure confines the acoustic wave energy into SiO2 thin-film, which contributes well to the improvement of the mass loading sensitivity. The corresponding sensing mechanism was analyzed by solving the acoustic propagation equations in layered structure. The sensing device patterned by delay-line on 36° YX-LiTaO3 substrate with SiO2 guiding layer was photolithographically developed as the sensor element, and characterized by using the high-low temperature chamber. The icing process was simulated by dropping appropriate water on top of the device surface. Very clear and fast frequency response was observed from the proposed sensing device in the icing process, and also, the influence of SiO2 guiding layer thickness on sensor response was also investigated.

C/SiC复合材料在化学气相沉积(CVI)过程中不可避免地会产生孔隙、微裂纹和分层等缺陷,超声能量衰减极大,组织极不均匀,几乎看不到二次底波,用常规的多次底波法无法测量其声速,提出了一种利用信号处理中的相关原理来测量其声速的方法,并用MATLAB软件进行了仿真以验证该方法的可行性.结果表明,利用相关法测量6种材料的声速,其误差均在2.5％以内,因此利用这种方法测量C/SiC复合材料的声速是可行的,对于C/SiC复合材料的声速测定有很大的实际意义.

为对整体涡轮的斜结合面进行无损检测,依据涡轮整体的结构特点,研制了一套同深度扫描超声成像检测系统.基于相控阵超声偏转角可控的特点,采用相控阵发射声波,曲面探头接收声波的方式,结合自动扫描装置对涡轮斜结合面进行扫查.获取接收信号后,以信号的幅值为特征对斜结合面中的缺陷进行成像.结果表明,该装置可对处于涡轮斜结合面30,50,70,90 mm深度处的直径为2,3 mm的缺陷进行超声成像检测,实现了对整体涡轮斜结合面不同深度位置缺陷的准确超声成像检测.

A temperature-compensated surface acoustic wave (SAW) device was developed to build a wireless and passive strain sensor. Y-cut 35 degrees X quartz with perfect temperature stability was employed as the piezoelectric substrate of the sensing device patterned by one-port resonator. Optimization by coupling of modes (COM) model towards sensing chip was conducted to determine the optimal design parameters, which offers lager Q-value. The prepared sensing device by standard photolithographic technique operating at 434MHz was characterized wirelessly. High strain sensitivity, excellent temperature stability, and high resolution were achieved in the wireless measurements. (C) 2020 Elsevier B.V. All rights reserved.

通过对纤维缠绕成型复合材料声学特性的研究,针对常规超声底波法检测该材料的困难,提出了一种利用超声背向散射信号表征材料均匀性的无损检测方法.通过大功率超声脉冲反射法提取玻璃纤维缠绕复合材料试块多个区域的回波信号,引入超声背向散射积分作为参数对背向散射信号进行时域和频域的分析,最后利用超声非线性系数对其表征效果进行验证.结果表明:时域背向散射积分对缺陷的敏感性高于频域积分、低于超声非线性系数,背向散射积分是有效、准确评价材料内部质量均匀性的参数.