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Identification of Micro-cracks in Ceramics by AE-Wave Form Analysis.

通过 AE 波形分析识别陶瓷中的微裂纹。

基本信息

批准号：
59470060
负责人：
YASUDA Eiichi
金额：
$ 4.86万
依托单位：
Tokyo Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1984
资助国家：
日本
起止时间：
1984 至 1986
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-59470060/
关键词：
Acoustic Emission AE; Ceramics Microcracks Fracture toughness Composite 複合材料界面剥離

项目摘要

Evaluation of fracture toughness is very important for ceramics which has poor toughness. When the large specimen is prepared separatery for toughness testing, the <K_(IC)> value of large specimen is sometimes different from that of objective materials. Therefore the Indentation Microfracture (IM) method becomes very useful, because of the unnecessity of large specimen. However, IM method includes many problems as time dependency of crack extension and complex interaction of different types of crack, etc. In this research, acoustic emission (AE) technique is applied to identify the type of cracks during the measurement by IM method. To make clear the identification, glass was used as a model materials, because of the possibility of in situ observation. At the initial indentation period, small surface cracks were observed on the contact area of the indentor. Radial type penny shape median crack initiated just beneath the indentor around few kgw during the increase of load, or decreasing load. Two penny shaped median cracks developed to half penny shaped cracks during decreasing the indentation load. Just before taking out the load, lateral type cracks initiated. Acoustic emissions were accompanied to every crack and the amplitude of the median crack was the largest one. Different from these types of the cracks, interfacial debonding occurres in the composite materials. To make clear the identification of the debonding, model samples were made from the transparent plastic as a matrix and lead of the pencil or carbon fires as a filler materials. After wave form analysis of the AE signals, small amplitude and high frequency were characterised to that of debonding. After three years research,it was cleared that the identification the different type of cracks is possible by analysing the wave form of the AE signal.

对于韧性较差的陶瓷来说，断裂韧性的评价非常重要。当单独制备大试样进行韧性测试时，大试样的<K_(IC)>值有时与目标材料的<K_(IC)>值不同。因此，压痕微断裂（IM）方法变得非常有用，因为不需要大样本。然而，IM方法存在裂纹扩展的时间依赖性以及不同类型裂纹之间复杂的相互作用等许多问题。本研究采用声发射（AE）技术来识别IM方法测量过程中的裂纹类型。为了清楚地识别，由于可以进行现场观察，所以使用玻璃作为模型材料。在压痕初始阶段，在压头接触区域观察到小的表面裂纹。在负载增加或负载减少期间，径向型便士形状中值裂纹在压头下方大约几公斤处开始出现。在降低压痕载荷过程中，两个便士形中间裂纹发展为半便士形裂纹。就在卸下负载之前，出现了横向裂纹。每条裂纹均伴有声发射，其中中位裂纹振幅最大。与这些类型的裂纹不同，复合材料中发生界面脱粘。为了明确脱粘的识别，以透明塑料为基体，以铅笔芯或碳火为填充材料制作模型样品。对AE信号进行波形分析后，发现脱粘信号振幅小、频率高。经过三年的研究，明确了通过分析声发射信号的波形可以识别不同类型的裂纹。