基于瑞利波的材料表面缺陷深度检测数值研究
发布时间：2018-09-05 20:03
【摘要】：表面缺陷是工程材料最为常见的一种损伤,会降低工程结构的耐久性和安全性。瑞利波检测方法相对于传统检测方法,具有简单易操作的优点。本文以通用有限元软件ANSYS为平台,模拟了瑞利波波长大于表面缺陷深度和瑞利波波长小于表面缺陷深度这两种情况的应力波传播过程,得出了瑞利波受表面缺陷作用后的幅值衰减、传播时间延时、频率阻隔规律。基于瑞利波在幅值、传播时间、频率三方面表现出来的规律,研究了瑞利波检测材料表面缺陷深度的方法。当瑞利波波长大于表面缺陷深度时,研究了幅值衰减规律检测表面缺陷深度的方法。通过有参考的布置方式,消除了材料阻尼和几何扩散的衰减影响。通过定量计算确定了激励源和观测点的合理位置,减弱了杂波的混叠影响。计算出的传递系数曲线表明,当表面缺陷深度与瑞利波波长比值(h/λ)在0到0.3之间时,满足单一映射,且下降趋势陡峭,适合用来检测大体积混凝土结构的表面裂缝深度。当瑞利波波长小于表面缺陷深度时,根据瑞利波沿表面缺陷侧面传播发生延时的规律研究了检测表面缺陷深度的方法。数值模拟表明,当激励频率为8 MHz时,构件高度在25 mm以上时,深度在1 mm和7 mm之间的表面缺陷均有较高检测精度,且能实现移动扫描检测和缺陷定位。该方法具有波包到达时刻易于确定的优点,对于深度为1 mm和2 mm的较浅表面缺陷也能很好检测出,适合检测钢材表面肉眼难以发现的缺陷深度。进一步,研究了瑞利波频率阻隔规律检测表面缺陷深度的方法。通过截断波形前面部分衍射体波的方法,寻找出深度为4 mm到10 mm之间表面缺陷对应的临界频率值,以及各深度表面缺陷能够获得临界频率值的有效激励频率范围。拟合出表面缺陷深度和临界频率值成反比例关系,当表面缺陷过深时,拟合曲线变化趋势平缓,不同深度表面缺陷的临界频率值过于接近。受临界频率值的区分度限制,该方法最大可检测深度在10 mm左右,适合检测钢材表面的疲劳裂纹深度。
[Abstract]:Surface defects are the most common damage of engineering materials, which can reduce the durability and safety of engineering structures. The Rayleigh wave detection method has the advantages of simple and easy to operate compared with the traditional detection method. In this paper, the stress wave propagation process of Rayleigh wave growing up to the depth of the surface defect and the Rayleigh wave length smaller than the depth of the surface defect are simulated on the platform of the universal finite element software ANSYS. The amplitude attenuation, propagation time delay and frequency barrier of Rayleigh wave due to surface defects are obtained. Based on the law of Rayleigh wave in amplitude, propagation time and frequency, the method of Rayleigh wave to detect the depth of surface defect of material is studied. When the Rayleigh wave grows up to the depth of the surface defect, the method of detecting the depth of the surface defect by the law of amplitude attenuation is studied. The influence of material damping and geometric diffusion is eliminated by reference arrangement. The reasonable position of excitation source and observation point is determined by quantitative calculation, and the aliasing effect of clutter is reduced. The calculated transfer coefficient curves show that when the ratio of surface defect depth to Rayleigh wave length (h / 位) is between 0 and 0.3, a single mapping is satisfied and the downward trend is steep, which is suitable for detecting the surface crack depth of mass concrete structures. When the Rayleigh wave length is smaller than the depth of the surface defect, the method of detecting the depth of the surface defect is studied according to the law of delay of Rayleigh wave propagating along the side of the surface defect. Numerical simulation shows that when the excitation frequency is 8 MHz and the height of the component is more than 25 mm, the surface defects with depth between 1 mm and 7 mm have high detection accuracy, and can realize mobile scanning detection and defect localization. This method has the advantage that the arrival time of the wave packet is easy to determine, and it can also detect the shallow surface defects with depths of 1 mm and 2 mm, which is suitable for detecting the defect depth which is difficult to detect by the naked eye on the steel surface. Furthermore, the method of detecting the depth of surface defects by Rayleigh wave frequency barrier is studied. By truncating the diffractive body waves in front of the waveforms, the critical frequency values corresponding to the surface defects between 4 mm and 10 mm depth and the effective excitation frequency range of the critical frequency values can be obtained for each depth surface defect. When the depth of surface defect is too deep, the change trend of fitting curve is gentle, and the critical frequency value of surface defect with different depth is too close. The maximum detectable depth of the method is about 10 mm, which is suitable for detecting the fatigue crack depth of steel surface.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU502
本文编号：2225323
[Abstract]:Surface defects are the most common damage of engineering materials, which can reduce the durability and safety of engineering structures. The Rayleigh wave detection method has the advantages of simple and easy to operate compared with the traditional detection method. In this paper, the stress wave propagation process of Rayleigh wave growing up to the depth of the surface defect and the Rayleigh wave length smaller than the depth of the surface defect are simulated on the platform of the universal finite element software ANSYS. The amplitude attenuation, propagation time delay and frequency barrier of Rayleigh wave due to surface defects are obtained. Based on the law of Rayleigh wave in amplitude, propagation time and frequency, the method of Rayleigh wave to detect the depth of surface defect of material is studied. When the Rayleigh wave grows up to the depth of the surface defect, the method of detecting the depth of the surface defect by the law of amplitude attenuation is studied. The influence of material damping and geometric diffusion is eliminated by reference arrangement. The reasonable position of excitation source and observation point is determined by quantitative calculation, and the aliasing effect of clutter is reduced. The calculated transfer coefficient curves show that when the ratio of surface defect depth to Rayleigh wave length (h / 位) is between 0 and 0.3, a single mapping is satisfied and the downward trend is steep, which is suitable for detecting the surface crack depth of mass concrete structures. When the Rayleigh wave length is smaller than the depth of the surface defect, the method of detecting the depth of the surface defect is studied according to the law of delay of Rayleigh wave propagating along the side of the surface defect. Numerical simulation shows that when the excitation frequency is 8 MHz and the height of the component is more than 25 mm, the surface defects with depth between 1 mm and 7 mm have high detection accuracy, and can realize mobile scanning detection and defect localization. This method has the advantage that the arrival time of the wave packet is easy to determine, and it can also detect the shallow surface defects with depths of 1 mm and 2 mm, which is suitable for detecting the defect depth which is difficult to detect by the naked eye on the steel surface. Furthermore, the method of detecting the depth of surface defects by Rayleigh wave frequency barrier is studied. By truncating the diffractive body waves in front of the waveforms, the critical frequency values corresponding to the surface defects between 4 mm and 10 mm depth and the effective excitation frequency range of the critical frequency values can be obtained for each depth surface defect. When the depth of surface defect is too deep, the change trend of fitting curve is gentle, and the critical frequency value of surface defect with different depth is too close. The maximum detectable depth of the method is about 10 mm, which is suitable for detecting the fatigue crack depth of steel surface.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU502
【参考文献】
相关期刊论文 前1条
1 刘慧龙;刘志平;陈逸凡;唐凡芳;;起重机金属结构焊缝表面裂纹红外热波检测仿真研究[J];武汉理工大学学报(交通科学与工程版);2014年01期
，本文编号：2225323
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