共查询到16条相似文献,搜索用时 140 毫秒
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小波去噪在焊接裂纹声发射信号处理中的应用 总被引:1,自引:0,他引:1
针对低碳钢焊接裂纹的特点和形成机理,研究了利用小波分析技术对焊接裂纹声发射信号进行消噪的过程.通过对提取典型的110~190kHz频率范围内的裂纹信号进行波形和频谱分析,其结果肯定了小波分析在裂纹信号处理中的有效性,为帮助判定焊接结构的完整性和可服役性提供了一定的帮助. 相似文献
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基于LabVIEW软件平台,绘制了6063铝合金缺口试样低周疲劳试验的声发射特征参数统计图和累积图。通过与断口分析结果进行对比,划分出AE信号对应裂纹扩展的三个阶段,并且发现两次主裂纹合并对应着三个高强度脉冲信号。通过对裂纹扩展三个阶段的撞击数进行波形分析和频谱对比分析,得出6063铝合金低周疲劳的声发射信号特征频率为225~250kHz和350~500kHz. 相似文献
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目的 为提高激光冲击强化(LSP)的声发射(AE)监测精度,结合AE监测技术与LSP弹塑性波理论,探究LSP过程中弹塑性波传播规律。方法 首先,基于弹塑性波理论设计LSP试验,采用AE监测技术实时获取冲击信号,并测量冲击后铝合金7075的塑性变形程度。然后,基于AE信号的时域波形,提出包络欧式距离法,确定对加工质量敏感的感兴趣片段(FOI)。进一步基于FOI,结合实际加工条件,定义了新的累积AE波形熵特征。最后,基于AE信号的多模态和非平稳信息,定义瞬时峰值能量曲线(IPEC),并进一步提取相关特征,从而探究弹塑性波传播规律、衡量传感器优劣。结果 仅包含弹性波的AE信号波形明显区别于弹塑性双波,塑性波传播速度明显落后于弹性波。包络欧式距离法确定的FOI能很好地定位弹塑性波。相较于AE波形熵,累积AE波形熵特征能很好地区分不同程度的弹塑性波。对比弹性波,塑性波主要集中在中低频段(200 kHz以下)。IPEC曲线精准确定31 kHz模态为塑性波的主要成分。进一步提取的峰值变化量 和峰值延迟时间 表明:相较于谐振传感器,宽频传感器对塑性波更加敏感。结论 所提方法和特征分别从时域和时频域上探究了弹塑性波的传播规律,所得的结论为规范和提高LSP的AE监测技术提供了理论支持与指导。 相似文献
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采用声发射技术对电梯钢丝绳拉伸过程进行监测,获取钢丝绳断丝信号,并对断丝信号进行参数分析和波形分析。试验结果表明:声发射检测技术能很好地定性辨识断丝信号。断丝信号具有高幅值高能量的特点,信号幅值在80~100 dB之间或绝对能量在2×10~6 mV·s以上的信号可定性认定为断丝信号。通过对具有这些特征的信号进行统计,可对钢丝绳断丝情况定量计算,从而推断出钢丝绳的剩余强度。钢丝绳断丝信号为突发型信号,对信号进行快速傅里叶变换可得知断丝信号的频率主要分布在0~220 kHz之间,且在25~50 kHz之间有明显的能量峰值。 相似文献
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采用有限元方法分析了激励信号的中心频率、轴向裂纹长度、缺陷深度和缺陷位置对周向超声导波反射的影响.利用时域反射系数R评价了轴向裂纹反射回波强度随缺陷尺寸和中心频率的变化趋势.对于一定尺寸的非贯通轴向裂纹,当中心频率从55 kHz增加到110 kHz时,周向水平剪切模态(C-SH0)的R略有增加.在给定的中心频率下,随着... 相似文献
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采用单颗金刚石压头作为磨粒对玻璃进行磨削实验,采集了磨削过程中的声发射信号,分析了磨削参数变化对声发射信号参数特征值的影响。结果表明:磨削过程中产生的声发射信号特征参量值振铃计数值、信号均方根值RMS随着磨削深度和磨削速度的增大而增大;随着工作台移动速度的增大而减小。在本实验条件下得到的声发射信号频率峰值主要在15.53 kHz以及18.65 kHz两个部分,且实验时主要研究玻璃材料脆性方式去除过程,说明了玻璃脆性断裂时产生的声发射信号频率峰值集中在15.53kHz和18.65 kHz。 相似文献
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搭建了基于磁巴克豪森噪声(MBN)原理的电磁检测平台,以Q235钢为试验对象开展了应力检测研究。在试验之前采用不同的波形、频率和电压进行测试,分析MBN信号峰值与频率、电压的关系,确定最优的激励参数。通过静载拉伸试验确定MBN信号与拉应力之间的关系,拟合MBN信号峰值与拉应力的关系曲线,分析信号峰值作为应力评价指标的可行性。结果表明:正弦波作为激励信号产生的MBN信号特征明显、信噪比高;MBN信号峰值随拉应力的增大而先增大后减小;分析非线性拟合曲线可以对应力集中程度进行评估。 相似文献
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Ki-Woo Nam Chang-Yong Kang Jae-Yoon Do Seok-Hwan Ahn Sang-Kee Lee 《Metals and Materials International》2001,7(3):227-231
The fatigue crack propagation of super duplex stainless steel was investigated for the effect of various volume fractions
of the austenite phase by changing the heat treatment temperature. We also analyzed acoustic emission signals obtained during
the fatigue crack propagation by the time-frequency analysis method. As the temperature of the heat treatment increased, the
volume fraction of austenite decreased and coarse grain was obtained. The specimen treated at 1200 had a longer fatigue life
and slower rate of crack growth. Results of time-frequency analysis of acoustic emission signals during the fatigue test showed
the main frequency of 200-300 kHz to have no correlation with heat treatment and crack length, and the 500 kHz signal to be
due to dimples and separation of inclusion. 相似文献
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Interface fracture toughness and fracture mechanisms of thermal barrier coatings investigated by indentation test and acoustic emission technique 下载免费PDF全文
Interface fracture toughness and fracture mechanisms of plasma-/sprayed thermal barrier coatings (TBCs) were investigated by interfacial indentation test (IIT) in combination with acoustic emission (AE) measurement. Critical load and AE energy were employed to calculate interface fracture toughness. The critical point at which crack appears at the interface was determined by the IIT. AE signals produced during total indentation test not only are used to investigate the interface cracking behavior by Fast Fourier Transform (FFT) and wavelet transforms but also supply the mechanical information. The result shows that the AE signals associated with coating plastic deformation during indentation are of a more continuous type with a lower characteristic frequency content (30-60 kHz), whereas the instantaneous relaxation associated with interface crack initiation produces burst type AE signals with a characteristic frequency in the range 70-200 kHz. The AE signals energy is concentrated on different scales for the coating plastic deformation, interface crack initiation and interface crack propagation. Interface fracture toughness calculated by AE energy was 1.19 MPam1/2 close to 1.58 MPam1/2 calculated by critical load. It indicates that the acoustic emission energy is suitable to reflect the interface fracture toughness. 相似文献
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真实裂纹的反演重构是无损检测理论的难点之一。由于反问题的不适定性,在应力腐蚀裂纹(SCC)的定量重构中常出现裂纹深度的过小评估。根据SCC电导率的测定结果,采用裂纹区电导率分区域赋值的思想,建立了SCC精细数值计算模型,有效改善了SCC深度的欠评估问题。裂纹重构过程中,利用基于粒子群算法(PSO)和共轭梯度法(CGM)的混合逆策略,分别寻求裂纹的形状参数和电导率分布。数值模拟和实际涡流检测信号的重构结果,验证了所提出的模型和方法对于应力腐蚀裂纹重构的有效性。 相似文献
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Correlation between the amount of artificial defects in bonded region and the acousto-ultrasonic parameters (AUPs) including the signal amplitude in adhesively bonded joints of carbon-fiber reinforced plastic (CFRP) laminates and Al6061 plates was investigated. The effect of the frequency content and the bandwidth of input signals were studied using 200 kHz, 650 kHz, 1 MHz, 2 MHz pulses and 1 MHz tone-burst signals. With increasing fraction of defects, the signal amplitude and AUP1 were decreased but AUP2 was increased. This result was attributed to the energy transfer characteristics of bonded joints with delamination-type defects and the change of spectral content as a result of the defects. Considering the highly attenuative nature of composite laminates, a pulse signal with major frequency content at or around the third harmonic of thickness mode resonance, 600700 kHz for the dimension of specimens used in this study, was found optimal for acousto-ultrasonic testing of CFRP-aluminum joints. 相似文献