共查询到19条相似文献,搜索用时 671 毫秒
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采用声发射技术,对四种不同晶粒度20~#钢试件的单轴拉伸过程进行监测,探究不同晶粒度对于金属材料损伤过程中声发射特性的影响。试验结果表明:声发射信号的幅值、能量和撞击计数等特征参数能够很好地描述材料不同晶粒度大小对材料拉伸过程中声发射特性的影响。细晶粒试件声发射信号数较少,强度较低,随着试件晶粒度的增大,声发射信号的强度和活性呈现明显增加的趋势。说明粗晶粒试件力学性能劣化严重,拉伸过程极易损伤,因此,试验结果也反映了金属材料微观损伤过程中声发射与材料内部的损伤演化密切相关。 相似文献
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为了深入研究螺纹钢拉伸全过程声发射信号特征,开展了完整和焊接试样的拉伸实验,通过SAEU2S型数字声发射系统对损伤特性进行实时监测。结合金属材料力学行为特性,根据计数率将全过程划分成不同的阶段,采用伪Margenau-Hill(PMH)分布进行了时频分析并利用小波包变换对信号进行了能量分析。结果表明:声发射特性参数能够很好的描述焊接对材料力学性能的影响,PMH分布具有良好的时频聚集性,频域和能量分析能够很好地描述焊接对材料力学性能的影响。实验结果为声发射技术应用于钢结构工程损伤定量、寿命预测、实时监测的研究提供了参考依据。 相似文献
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金属点蚀过程声发射源机制研究 总被引:3,自引:0,他引:3
研究了腐蚀特别是点蚀过程产生应力波,即声发射(AE)的源机制,估算了单个钝化膜破裂所产生的薄板表面位移量级,并用实验进行了论证。作者提出,利用板波声发射理论加上参数识别方法,可将腐蚀过程产生的声发射信号同背景噪声相区别。 相似文献
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为研究蒸汽养护对再生骨料混凝土断裂过程损伤特征的影响,开展了再生骨料混凝土三点弯断裂试验,并采用声发射技术对损伤过程进行了监测分析。结果表明,蒸养降低了再生骨料混凝土断裂峰值荷载,断裂过程中声发射信号强度低于标准养护试件。声发射振铃计数、撞击数、b值等参数能够准确反映再生骨料混凝土断裂过程损伤演变规律。加载上升阶段,声发射信号活动性很低,试件内以微裂纹的形成为主,加载至荷载峰值,声发射振铃计数累计值增长呈现平缓阶段,混凝土内微裂缝的聚合会持续一段时间。峰值后荷载迅速降低阶段声发射信号最活跃,为裂缝迅速发展的过程。峰后荷载缓慢降低的过程,声发射信号活跃性降低,裂缝扩展至试件顶部区域,主要是宏观裂缝的开展,不再产生新的裂缝。 相似文献
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The stress corrosion cracking (SCC) of high-strength steel used in prestressed concrete structures was studied by acoustic emission technique (AE). A simulated concrete pore (SCP) solution at high-alkaline (pH ≈ 12) contaminated by sulphate, chloride, and thiocyanate ions was used. The evolution of the acoustic activity recorded during the tests shows the presence of several stages related respectively to cracks initiation due to the local corrosion imposed by corrosives species, cracks propagation and steel failure. Microscopic examinations pointed out that the wires exhibited a brittle fracture mode. The cracking was found to propagate in the transgranular mode. The role of corrosives species and hydrogen in the rupture mechanism of high-strength steel was also investigated. This study shows promising results for an potential use in situ of AE for real-time health monitoring of eutectoid steel cables used in prestressed concrete structures. 相似文献
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《声学学报:英文版》2015,(3)
The safety of rail is very important for the development of high speed railway,and it is necessary to investigate the features of inner cracks in rail.In order to obtain the features of Acoustic Emission(AE)sources of inner cracks in rail,AE sources with different types,depths and propagation distances are examined for crack in rail.The finite element method is utilized to model the rail with cracks and the results of experiment demonstrate the effectiveness of this model.Wavelet transform and Rayleigh-Lamb equations are utilized to extract the features of crack AE sources.The results illustrate that the intensity ratio among AE modes can identify the AE source types and the AE sources with different frequencies in rail.There are uniform AE mode features existing in the AE signals from AE sources in rail web,however AE signals from AE sources in rail head and rail base have the complex and unstable AE modes.Different AE source types have the different propagation features in rail.It is helpful to understand the rail cracks and detect the rail cracks based on the AE technique. 相似文献
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Lifang Mei Genyu Chen Xiangzhong Jin Yi Zhang Qiang Wu 《Optics and Lasers in Engineering》2009,47(11):1117-1124
The paper presented some useful results of deep-penetration laser welding of high-strength galvanized steel sheets, which had been carried out by a self-made CO2 laser unit with maximum power output of 1.5 kW. The workpieces of high-strength galvanized automobile steels with thickness of 1.5 mm were butt-welded with argon as the shielding gas. The effects of such factors as laser power, welding speed, focal position, shielding gas and zinc vaporization on the quality of welds are investigated. With the processing parameters optimized and the proper shielding gas used in both coaxial and side-blow direction, most of the defects, such as pores, cracks and softening in HAZ, can be avoided in laser welding joints. The microstructure, the hardness distribution and the elemental distribution in the welding joints can be changed due to laser heating and recrystallization. In order to determine the mechanical properties of the welding joints, the static tensile strength was tested. Experimental results indicated that both the strength and microhardness of welding joints were higher than those of the base metal. Consequently, the welding quality is reliable for manufacturing of automobile bodies. 相似文献
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提出了一种利用ANSYS软件模拟单轴扩散焊过程的仿真计算方法,主要研究采用单轴扩散焊工艺制备聚变实验包层模块冷却管板中的管道变形问题,同时采用低活性马氏体钢进行了相关实验研究,并将实验结果与仿真结果进行对比以验证计算方法的可靠性。结果表明,在单轴扩散焊过程中,管道出现较大变形;仿真计算结果与实验结果吻合良好。这表明本方法将有助于单轴扩散焊制造冷却板的工艺改进。 相似文献
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Infrared thermography offers a wide range of possibilities for the detection of flaws in welding, being the main difference among them the thermal excitation of the material. This paper analyzes the application of an inexpensive and versatile thermographic test to the detection of subsurface cracks in welding. The procedure begins with the thermal excitation of the material, following with the monitoring of the cooling process with IRT (InfraRed Thermography). The result is a sequence of frames that enables the extraction of thermal data, useful for the study of the cooling tendencies in the defect and the non-defect zone. Then, each image is subjected to a contour lines algorithm towards the definition of the morphology of the detected defects. This combination of data acquisition and processing allows the differentiation between two types of cracks: toe crack and subsuperficial crack, as defined in the quality standards. 相似文献
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This paper attempts to introduce a near-field acoustic emission (AE) beamforming method to estimate the AE source locations by using a small array of sensors closely placed in a local region. The propagation characteristics of AE signals are investigated based on guided wave theory to discuss the feasibility of using beamforming techniques in AE signal processing. To validate the effectiveness of the AE beamforming method, a series of pencil lead break tests at various regions of a thin steel plate are conducted. The potential of this method for engineering applications are explored through rotor-stator rubbing tests. The experimental results demonstrate that the proposed method can effectively determine the region where rubbing occurs. It is expected that the work of this paper may provide a helpful analysis tool for near-field AE source localization. 相似文献
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Leak detection in water-filled plastic pipes through the application of tuned wavelet transforms to Acoustic Emission signals 总被引:4,自引:0,他引:4
A new method to detect leakage in a water-filled plastic pipe is proposed. In this method, a leakage signal-signature in time domain is first captured by monitoring the Short Time Fourier Transforms (STFT) of AE (Acoustic Emission) signals over a relatively long time-interval. The captured signal is then used to find a mother wavelet (tuned wavelet) for the best signal localization in time and frequency domains. The technique for AE signal detection using tuned wavelet is then described. Practical application of the method proposed herein is then presented using a water-filled plastic pipe as a case study. Signals generated from this experimental setup are collected to identify leakage signal-signatures from other interfering signals (background, pipe natural frequency, splash and environmental noise). The results of the experiment prove that using tuned wavelet, AE events can be detected and identified precisely in time. In addition, sources of signals due to leakage and their respective energy levels can also be recognized. 相似文献
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Investigation of fatigue failure prediction of Fe-Cr alloy coatings under rolling contact based on acoustic emission technique 总被引:2,自引:0,他引:2
The rolling contact fatigue (RCF) failure prediction of the coating Fe-Cr alloy coatings was investigated. The acoustic emission (AE) technique was used to monitor RCF tests of the coatings. The failure mechanism was investigated. Results showed AE signals sensitively detected the initiations and propagations of the fatigue cracks within the coatings before the obvious surface material losses. AE signals also reflected the cumulate damage procedure. So the coming RCF failures can be predicted by AE signal responses. Moreover, the micro-defects within the coatings were considered to be the fatigue crack origins. 相似文献
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This study is concerned with the effects of laser and arc arrangement on weld integrity for the hybrid laser arc welding processes. Experiments were conducted for a high-strength steel using a 4 kW Nd: YAG laser and a metal active gas (MAG) welding facility under two configurations of arc–laser hybrid welding (ALHW) and laser–arc hybrid welding (LAHW). Metallographic analysis and mechanical testing were performed to evaluate the weld integrity in terms of weld bead geometry, microstructure and mechanical properties. The morphology of the weld bead cross-section was studied and the typical macrostructure of the weld beads appeared to be cone-shaped and cocktail cup-shaped under ALHW and LAHW configurations, respectively. The weld integrity attributes of microstructure, phase constituents and microhardness were analyzed for different weld regions. The tensile and impact tests were performed and fracture surface morphology was analyzed by scanning electron microscope. The study showed that ALHW produced joints with a better weld shape and a more uniform microstructure of lath martensite, while LAHW weld had a heterogeneous structure of lath martensite and austenite. 相似文献