共查询到19条相似文献,搜索用时 234 毫秒
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通过红砂岩单轴压缩声发射试验,基于裂纹扩展规律,将红砂岩变形破坏过程分为不同阶段,研究红砂岩不同变形阶段的声发射事件率特征和主频特征。研究结果表明:在压密阶段,声发射事件率先快速增大,随后逐步减小至接近于0,σcc对应于声发射事件率下降至接近于0的拐点;σcc~σci阶段声发射事件率保持恒定且接近0,σci后声发射事件率上升,σci为声发射事件率由恒定转为增加的拐点。在裂纹稳定扩展和非稳定扩展阶段,随应力的增加低主频声发射增多;峰后破坏阶段,声发射主频带变宽,有较多的高主频和低主频声发射产生。声发射事件率和主频均能反映声发射源的特征,通过声发射事件率和主频变化特征能粗略判断裂纹闭合应力和起裂强度。将声发射事件率和声发射主频进行联合分析,能更加全面地了解声发射源的特征,达到识别声发射源的目的。 相似文献
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研究了超高相对分子质量聚乙烯抵密度聚乙烯( PE-UHMW /PE-LD)单向层合板拉伸破坏过程中的声发射信号参数之间的相关性,并进行了主成分分析。结果表明,声发射参数间存在较强的相关性,其中[0]层合板(加载方向与纤维方向平行)持续时间和振铃计数之间相关系数达到0.976,[90〕层合板(加载方向与纤维方向垂直)振幅和振铃计数之间相关系数达到0.8。主成分分析显示[0]和[90]层合板第一主成分主要反映上升时间、持续时间等信号的时域特点,第二主成分主要反映峰值频率、频率重心等信号的频域特点。通过[90〕层合板声发射信号的主成分得分图,显示出界面裂纹产生、扩展和界面分离等不同损伤模式对应不同的主成分得分。 相似文献
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对平纹编织C/SiC复合材料样品拉伸破坏过程的声发射进行监测,采用基于改进遗传算法的无监督聚类方法对声发射信号进行模式识别,统计分析各类声发射模式的特征及其演化过程,结合断口分析,研究了C/SiC复合材料的拉伸强度、损伤机制与声发射信号演化之间的关系.结果表明:维断裂的声发射能量能够反映纤维/基体界面结合强度;低强度C/SiC材料中存在引起应力集中的基体富集区,在加载初期基体开裂事件占比超过50%;中强度C/SiC材料由于较强的界面,纤维损伤以单丝或部分纤维断裂事件为主;高强度C/SiC材料界面结合强度适中,纤维簇断裂是主要的失效模式. 相似文献
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为揭示聚乙烯自增强复合材料(PE-UHMW/PE-LD)不同损伤模式的声发射信号频率特征,通过对基体、单纤维复合材料、90°单向板+45°/-45°层合板的拉伸破坏,分别诱导产生基体损伤、纤维断裂、纤维/基体界面损伤和层间损伤的AE信号,并和非损伤AE信号(环境噪声、断铅模拟)频率特征进行对比。实验结果表明,非损伤AE信号和损伤AE信号之间均具有不同的峰值频率和频率分布特征。 相似文献
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《玻璃钢/复合材料》2021,(8)
针对碳纤维增强复合材料(CFRP)损伤机制复杂、损伤声发射信号识别困难的问题,本文提出了一种基于模态分离方法的CFRP损伤信号识别分类算法,可实现CFRP损伤声发射信号的模态表征。首先,基于CFRP层合板模拟声源模态分析结果设计不同范围的数字滤波器,实现了声发射信号中的S_0、A_0模态分离;随后,根据纤维断裂和基体开裂单一损伤信号的模态特征,建立了损伤信号的识别分类算法,并验证了其对单一损伤信号的分辨率;最后,利用算法对层合板面内弯曲损伤信号进行分析,验证其在CFRP完整结构损伤信号识别中的有效性。结果表明,该算法在纤维断裂和基体开裂试验中的分辨率分别高达97.3%和92%,同时也实现了CFRP层合板的损伤过程表征,证明其可实现CFRP完整结构损伤机制的识别。 相似文献
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介绍了声发射技术的基本原理,用声发射技术监测了莫来石-钛酸铝陶瓷材料急冷时热震损伤强度衰减及裂纹的扩展过程,结果表明:由热应力引起的微裂纹稳态扩展和失稳扩展的声发射特性与该试样热震损伤后的残余强度变化趋势是一致的。 相似文献
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为研究风电叶片复合材料损伤破坏的声发射特性以及复合材料的力学性能,对含有纤维预断试件和无纤维预断的完好试件分别进行了三点弯曲力学性能试验,并在加载过程中采用声发射检测仪实时监测整个损伤破坏过程。对采集到的声发射信号处理分析,便可获得风电叶片复合材料的弯曲力学性能和损伤破坏的声发射特性。试验结果表明:玻璃纤维复合材料在弯曲载荷作用下出现典型的破坏特征包括纤维断裂、纤维/基体脱胶和纤维分层。纤维预断试件的声发射信号波形最高幅度达到2.5 V,频带分布在20~300 k Hz范围;无纤维预断试件的声发射信号波形最高幅度为0.07 V,频带分布在10~180 k Hz之间。 相似文献
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通过对碳纤维编织复合材料的拉伸实验,利用声发射技术(Acoustic Emission,简称"AE")和数字图像相关(Digital Image Correlation,简称"DIC")方法研究碳纤维复合材料的损伤演化规律。通过采集试件在拉伸过程中的声发射信号、损伤变形与应变场信息,分析碳纤维编织复合材料的力学加载、变形场和声发射特征参数的关系。结果表明复合材料的位移场、应变场信息以及AE信号特征参数能良好地描述复合材料在拉伸状态下的损伤累积和破坏过程。在加载前期,以40~60 dB低幅度信号为主;随着载荷增加,撞击累计数急剧升高,高幅度、高持续时间信号增多。通过DIC测得的位移场和应变场信息,发现对于相同的载荷增量,加载方向的位移和最大拉应变呈先增加后减小的趋势。 相似文献
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Acoustic emission (AE) during irreversible deformation in short glass fiber reinforced poly(vinyl chloride) (PVC) composites was studied using a piezoelectric crystal transducer. Compared to the well-coupled composites, many more AE events were observed during tensile deformation in the poorly-coupled composites, presumably due to failure at the fiber-matrix interface. No fiber fracture was detected in the tensile tests for either well-coupled or poorly-coupled composites. Irreversibility of acoustic emission was observed in repeated tensile loading experiments. Unlike PVC, the short fiber composites fractured during stress relaxation at 1 percent elongation. Studies of acoustic emission behavior during stress relaxation indicated that interfacial debonding is a time-dependent process. Relaxation fracture time was strongly increased by chemical coupling at the interface. 相似文献
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声发射技术可以评估混凝土的损伤演化过程。为合理描述混凝土的受压损伤演化过程,开展了轴压和偏压状态下混凝土损伤全过程的声发射试验,分析了轴压和偏压状态下混凝土损伤全过程声发射特征参数的演化规律,进而合理遴选了描述混凝土损伤演化过程的声发射特征参数,揭示了混凝土应力-应变曲线特征点与声发射特征参数特征点之间的对应关系。分析表明:振铃计数、持续时间、幅值、信号强度和平均频率可以较好地表征轴压与偏压状态下混凝土损伤的演化规律;混凝土试件受压破坏过程中声发射特征参数特征点与应力-应变曲线特征点之间具有高度的相关性,其中声发射特征参数特征点中的第一个分界点对应于应力-应变曲线弹性阶段的起点,第二个分界点对应于应力-应变曲线的峰值应力点,信号强度的最大突变点对应于应力-应变曲线的开裂点。 相似文献
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Three-point-bend testing of a continuous unidirectional glass reinforced unsaturated polyester composite was chosen as a model to study the acoustic emission (AE) response and associated damage events in composite materials. Conventional three-point-bend samples were tested over a wide range of span-to-depth ratios, with failure modes established by post-failure scanning electron microscope (SEM) analysis. In addition, in-situ AE monitoring with simultaneous SEM recording was undertaken during three-point-bend testing inside an SEM vacuum chamber. These two test methods, using different equipment and sample geometry, were found to yield similar mechanical and AE results. The in-situ tests enabled the development of the various stages of damage to be observed while the AE response was simultaneously monitored. This enabled the AE signals to be unambiguously assigned to specific damage accumulation mechanisms. It was concluded that the AE amplitude distribution can be divided into three main ranges in this system: 60 to 65 dB, 75 to 85 dB, and larger than 90 dB corresponding to matrix damage, fiber-matrix debonding, and fiber breakage, respectively. It has been demonstrated that the coupling of AE monitoring with SEM recording of a composite system undergoing mechanical loading is a very powerful technique in the study of damage accumulation in advanced composite materials. 相似文献
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The failure mode in injection-molded short (SGF) and long glass fiber (LGF) reinforced polypropylene (PP) was studied on compact tension (CT) specimens simultaneously by acoustic emission (AE) and transmitted light microscopy. A significant difference was revealed in the failure manner characterized by the cumulative run, amplitude and energy distribution curves between the SGF- and LGF-PP both in the crack initiation and propagation stage. It was established that the failure of SGF-PP did not alter with the loading; this composite failed mostly by matrix deformation along with fiber/matrix debonding and some fiber pull-out. The failure mode of the LGF-PP differed from that scenario, since fiber fracture was resolved in every stage of the loading. On the contrary to SGF-PP, the failure of this composite was governed by fiber-related events (fracture, pull-out, debonding). The amplitude and energy of the AE signals were assigned to individual failure events and thus the failure sequence concluded. 相似文献
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建立了预测含初始脱粘缺陷复合材料加筋壁板渐进压溃响应的数值分析模型。该模型综合考虑了复合材料层合板的纤维失效、基体失效和纤维-基体剪切失效三种典型的面内损伤模式,并通过编写用户自定义材料子程序VUMAT实现面内失效类型的判断和相应材料性能的折减;在壁板和筋条连接界面应用虚裂纹闭合技术(VCCT)计算层间裂纹前缘的应变能释放率,并结合B-K混合模式准则控制缺陷的起裂以模拟脱粘的扩展演化过程;采用显式动力学方法准静态分析结构在压缩载荷下的屈曲、后屈曲直至最终压溃的响应过程。数值分析结果与文献试验、数值结果吻合良好,验证了模型的合理性和有效性,并详细研究了复合材料脱粘加筋壁板的损伤演化过程和渐进压溃行为。 相似文献