共查询到18条相似文献,搜索用时 171 毫秒
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基于HHT的预应力钢筋混凝土梁断裂AE信号分析 总被引:2,自引:0,他引:2
针对混凝土材料损伤所产生的声发射信号复杂的特点,提出了基于Hilbert—Huang变换的分析混凝土声发射信号的新方法。利用全波形声发射技术记录了预应力混凝土梁在三点弯曲荷载试验下整个破坏过程的声发射信号,研究了声发射累计能量随时间变化的关系曲线,分析了梁在不同破坏阶段产生的实测声发射信号,获得了信号的Hilbert谱。通过与小波分析结果进行比较,显示出该方法具有处理精度高、自适应性强的特点,能有效地提取声发射信号中损伤的主要特征,为声发射信号处理提出了一种新的途径。 相似文献
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文中以P92钢与Ni基焊材焊接热影响区为研究对象,通过采集紧凑拉伸试验过程中异种钢接头热影响区启裂及裂纹扩展的声发射特性信号,分析裂纹扩展的声发射信号幅值、频率分布、能量及振铃计数等特征参数,同时分析声发射特征信号与断口形貌之间的对应关系。结果表明:裂纹扩展声发射信号均为突发型信号,频率主要集中在50~200 kHz;裂纹稳定扩展的声发射信号具有平均幅值较低、总能量和振铃计数率参数变化平缓的特点;裂纹失稳扩展的声发射信号具有平均幅值较高、总能量和振铃计数率参数呈瞬时增加的特点;裂纹稳定扩展阶段的声发射特征信号与韧性断口特征相对应;裂纹失稳扩展阶段的声发射特征信号与准解理断裂或解理断裂特征相对应。 相似文献
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应用声发射技术对蜂窝夹层复合材料压缩损伤过程进行了试验研究。分析载荷与声发射信号关联图,依据其损伤过程和声发射特征,发现随着加载条件下载荷的增加,复合材料的损伤逐步增大。在加载初始阶段,仅有少量声发射信号,各种表征信号量小幅度增加;在加载中期,声发射信号增多,各种表征信号量不断增大;在加载后期,声发射信号有明显突增,各种表征信号量急剧增加。复合材料压缩损伤破坏与声发射的幅值、能量、撞击、上升时间、持续时间和计数等参量特征相关。根据各阶段特征参量滤波后所得信号分布与实际断裂位置相吻合。 相似文献
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D.J. Stephenson X. Sun C. Zervos 《International Journal of Machine Tools and Manufacture》2006,46(10):1053-1063
ELID grinding of BK7 glass and Zerodur was investigated using acoustic emission. Experiments showed that the contacting area between the wheel and workpiece in a grinding process was critical to influence wheel loading for a fine grit size resin-bonded cup wheel. ELID can be used for efficient material removal when the wheel/workpiece contacting area is large. Correlations were observed between the dressing intensity on the ELID wheel and the detected AE signals. Aggressive ELID dressing parameters for grinding with finer grit size wheels corresponded to a lower AE level. With an increase in the processing time of an ELID wheel, low and stable AE amplitudes became large with fluctuations due to the deterioration of the grinding wheel. Results indicate that the AE sensing technique has the potential to be adopted as an effective method for monitoring an ultra precision grinding process, identifying the condition of the grinding wheel and investigating the mechanism of ELID grinding. 相似文献
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在硬脆难加工材料硬质合金PA30高速深磨声发射实验中,随着工件速度和磨削切削深度增加,声发射信号特征参数均方根(AERMS)和磨削力变大;随着砂轮速度增大,AERMS和磨削力减小。磨削力和AERMS有相同的变化趋势。硬质合金PA30高速深磨AE频谱的能量在100~600kHz的频段比较集中,其AE信号频谱的能量与频率范围明显高于低速浅切磨削。 相似文献
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采用一种新型砂轮破碎状态信号检测方法——声发射(AE)技术,通过采集环境背景、空转、空载和负载AE信号,并对信号进行时频域研究。对比砂轮破碎后和破碎前AE信号特征,时域信号特征电压值增大了2.5倍、能量谱峰值增大了4倍、均方根值(RMS)增加了1.17倍,频域信号经快速傅里叶转换(FFT)后得到了一个高频电压信号。研究结果表明:声发射技术优于目前常用的振动法、音量法和光电法,更适合用于砂轮回转实验破碎识别。 相似文献
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Curt E. Everson S. Hoessein Cheraghi 《International Journal of Machine Tools and Manufacture》1999,39(3):349
Precision drilling is a process where a close tolerance hole can be produced with a special drill bit without subsequent reaming. Producing a hole without reaming results in less overall processing time during hole preparation. Precision drilling is best accomplished by a robot with a computer controlled drilling end effector due to the high degree of process control required. Some aspects of the process, such as spindle speed, feed rate, and peck cycles, can easily be controlled by a computer controlled end effector. Other variables, such as drill bit wear, chipping, and point geometry variation, cannot be controlled with the end effector. These variables affect the diameter of the hole but cannot be detected unless the hole or the drill bit is manually inspected. It is not practical to stop the process and check the diameter after every hole. Therefore, a means to perform real time drilling process monitoring is required to detect if an oversized hole is being drilled. The primary objective of this research was to correlate the diameter of a hole drilled in steel with any acoustic emission (AE) signal measurement parameter. The secondary objective was to correlate drill bit lip height variation, which has a significant influence on the diameter of a hole, with any AE signal measurement parameter. The results of this study showed that acoustic emission could only be correlated to hole diameter variations if those variations were related to the lip height variations. However, AE energy and RMS were correlated to lip height variations under a wide variety of conditions. 相似文献
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T. Warren Liao Chi-Fen Ting J. Qu P.J. Blau 《International Journal of Machine Tools and Manufacture》2007,47(3-4):580-592
Grinding wheel surface condition changes as more material is removed. This paper presents a wavelet-based methodology for grinding wheel condition monitoring based on acoustic emission (AE) signals. Grinding experiments in creep feed mode were conducted to grind alumina specimens with a resinoid-bonded diamond wheel using two different conditions. During the experiments, AE signals were collected when the wheel was ‘sharp’ and when the wheel was ‘dull’. Discriminant features were then extracted from each raw AE signal segment using the discrete wavelet decomposition procedure. An adaptive genetic clustering algorithm was finally applied to the extracted features in order to distinguish different states of grinding wheel condition. The test results indicate that the proposed methodology can achieve 97% clustering accuracy for the high material removal rate condition, 86.7% for the low material removal rate condition, and 76.7% for the combined grinding conditions if the base wavelet, the decomposition level, and the GA parameters are properly selected. 相似文献
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声发射检测的主要目的是发现声发射源和有关源的信息,声发射源定位是声发射检测中至关重要的指标,其准确程度反映了声源的检测位置与实际缺陷源位置的符合程度。本研究针对复合材料的特性,结合实际情况进行了声速和衰减测量实验,并通过断铅实验对复合板进行声发射定位。通过对复合材料板压缩实验的在线监测,基于声发射信号参数的提取及关联图分析,给出了各损伤阶段的参数特征,以及声发射监测区域内的裂纹萌生扩展断裂的时间和位置。研究结果表明,复合板实际断裂位置与声发射监测得出的位置相吻合。 相似文献
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Acoustic emission signals from interrupted machining operations exhibit spikes at workpiece entry and exit, which are particularly conspicuous in grinding. Although their occurrence has been widely reported, these spikes are yet to be clarified in terms of their origin or interpreted to yield useful process information. This paper hence reports on the analyses of time-averaged and raw acoustic emission signals from surface grinding, with reference to burr formation as well as dynamic and thermal effects, in order to elucidate this intriguing phenomenon. The transient spikes at the entry and exit are shown to be a consequence of the wheel establishing and losing contact with the work over the actual contact length, in terms of heat conduction and damping, which are reflected in characteristic frequency bands of the AE signal. The research is demonstrated to have consequently yielded a simple, non-destructive method for assessing the actual wheel–work contact length in grinding. 相似文献
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The aim of this work is to study the wheel/workpiece dynamic interactions in high-speed grinding using vitrified CBN wheel and DTG (difficult to grind) work materials. This problem is typical in the grinding of engine valve heads. The influence of tangential force per abrasive grain was investigated as an important control variable for the determination of G ratio. Experiments were carried out to observe the influence of vibrations in the wheel wear. The measurements of acoustic emission (AE) and vibration signals helped in identifying the correlation between the dynamic interactions (produced by forced random excitation) and the wheel wear. The wheel regenerative chatter phenomenon was observed by using the wheel mapping technique. 相似文献