基于瑞利波的材料表面缺陷深度檢測數(shù)值研究
發(fā)布時間：2018-09-05 20:03
【摘要】：表面缺陷是工程材料最為常見的一種損傷,會降低工程結(jié)構(gòu)的耐久性和安全性。瑞利波檢測方法相對于傳統(tǒng)檢測方法,具有簡單易操作的優(yōu)點。本文以通用有限元軟件ANSYS為平臺,模擬了瑞利波波長大于表面缺陷深度和瑞利波波長小于表面缺陷深度這兩種情況的應(yīng)力波傳播過程,得出了瑞利波受表面缺陷作用后的幅值衰減、傳播時間延時、頻率阻隔規(guī)律。基于瑞利波在幅值、傳播時間、頻率三方面表現(xiàn)出來的規(guī)律,研究了瑞利波檢測材料表面缺陷深度的方法。當瑞利波波長大于表面缺陷深度時,研究了幅值衰減規(guī)律檢測表面缺陷深度的方法。通過有參考的布置方式,消除了材料阻尼和幾何擴散的衰減影響。通過定量計算確定了激勵源和觀測點的合理位置,減弱了雜波的混疊影響。計算出的傳遞系數(shù)曲線表明,當表面缺陷深度與瑞利波波長比值(h/λ)在0到0.3之間時,滿足單一映射,且下降趨勢陡峭,適合用來檢測大體積混凝土結(jié)構(gòu)的表面裂縫深度。當瑞利波波長小于表面缺陷深度時,根據(jù)瑞利波沿表面缺陷側(cè)面?zhèn)鞑グl(fā)生延時的規(guī)律研究了檢測表面缺陷深度的方法。數(shù)值模擬表明,當激勵頻率為8 MHz時,構(gòu)件高度在25 mm以上時,深度在1 mm和7 mm之間的表面缺陷均有較高檢測精度,且能實現(xiàn)移動掃描檢測和缺陷定位。該方法具有波包到達時刻易于確定的優(yōu)點,對于深度為1 mm和2 mm的較淺表面缺陷也能很好檢測出,適合檢測鋼材表面肉眼難以發(fā)現(xiàn)的缺陷深度。進一步,研究了瑞利波頻率阻隔規(guī)律檢測表面缺陷深度的方法。通過截斷波形前面部分衍射體波的方法,尋找出深度為4 mm到10 mm之間表面缺陷對應(yīng)的臨界頻率值,以及各深度表面缺陷能夠獲得臨界頻率值的有效激勵頻率范圍。擬合出表面缺陷深度和臨界頻率值成反比例關(guān)系,當表面缺陷過深時,擬合曲線變化趨勢平緩,不同深度表面缺陷的臨界頻率值過于接近。受臨界頻率值的區(qū)分度限制,該方法最大可檢測深度在10 mm左右,適合檢測鋼材表面的疲勞裂紋深度。
[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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU502
本文編號：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.
【學(xué)位授予單位】：哈爾濱工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：TU502
【參考文獻】
相關(guān)期刊論文 前1條
1 劉慧龍;劉志平;陳逸凡;唐凡芳;;起重機金屬結(jié)構(gòu)焊縫表面裂紋紅外熱波檢測仿真研究[J];武漢理工大學(xué)學(xué)報(交通科學(xué)與工程版);2014年01期
，本文編號：2225323
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