共查询到18条相似文献,搜索用时 218 毫秒
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基于小波有限元和遗传优化算法的转轴裂纹诊断 总被引:1,自引:0,他引:1
构造Rayleigh-Euler和Rayleigh-Timoshenko区间B样条小波梁单元,分别离散柔性转轴和刚性转盘,建立转子系统有限元模型.求解裂纹转子前三阶固有频率,并将其拟合成裂纹相对位置和相对深度的函数.将裂纹识别中的匹配追踪问题转化为多维优化问题,以实测固有频率作为输入,利用遗传算法寻优求解出与输入值相差最小的样本点,进而测出裂纹的相对位置和深度.试验研究表明,所提出的裂纹诊断方法具有较好的精度和鲁俸性,且易于在工程实践中进行裂纹转子定量诊断. 相似文献
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研究基于模型的结构裂纹故障诊断中的正反问题,即求解含裂纹参数结构的固有频率以及利用实测固有频率,定量识别裂纹参数。构造用于求解正问题的一维区间B样条小波裂纹单元,通过求解裂纹结构有限元模型,绘制以裂纹等效刚度与裂纹位置为变量的三阶频响函数解曲线,将实际测出的系统前三阶固有频率作为输入,根据曲线的交点定量预示出裂纹的位置和深度。实验研究表明,文中构造的区间B样条小波裂纹单元有效克服了传统有限元分析在求解裂纹奇异性问题时存在的效率低、精度差甚至难以收敛到正确解的缺陷,同时具有足够的辨识精度,为早期裂纹故障定量诊断提供新方法。 相似文献
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梁类结构多裂纹微弱损伤的小波有限元定量检测方法 总被引:2,自引:1,他引:1
提出了一种定量检测梁类结构多裂纹参数的方法。利用适宜求解奇异性问题的小波有限元法,从动力学正问题入手,对裂纹梁进行有限元建模,获得裂纹故障在结构固有频率上反映的本质征兆,并利用曲面拟合技术绘制出以裂纹位置和深度作为变量的固有频率变化率曲面,然后对整个裂纹梁进行剖分,迭代求解出每个剖分单元上的结构损伤系数。损伤系数为正的单元诊断为裂纹单元,在每个裂纹单元上求出裂纹对应的前三阶固有频率变化率,并分别将其作为输入参数代入固有频率变化率曲面,做出前三阶模态的频率变化率等高线,最后通过三条等高线的交点预测出裂纹存在的位置和深度,算例分析验证了该算法的有效性。 相似文献
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工字截面梁轨结构裂纹损伤的小波有限元定量诊断 总被引:1,自引:0,他引:1
研究工字截面梁轨结构裂纹定量识别中的正反问题,即通过裂纹位置和深度求解结构的固有频率以及利用结构的固有频率,识别裂纹位置和深度.裂纹被看作为一扭转线弹簧,利用工字梁裂纹应力强度因子推导出线弹簧刚度,构造出结构的小波有限元刚度矩阵和质量矩阵,从而获得裂纹结构的前3阶固有频率.通过行列式变换,将反问题求解简化为只含线弹簧刚度一个未知数的一元二次方程求根问题,分别做出以不同固有频率作为输入值时裂纹位置与裂纹深度之间的解曲线,曲线交点预测出裂纹的位置与深度,试验结果验证算法的有效性. 相似文献
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结构中裂缝的存在使其模态参数发生改变 ,如局部刚度减小、阻尼增大、固有频率降低。把裂缝梁模拟成由扭曲弹簧连接 ,并对其前三阶固有频率的变化与裂缝位置和深度之间的关系进行计算和分析 ;利用特征方程以及前三阶固有频率 ,通过作图法对裂缝参数进行识别。识别结果证明 ,这种方法精度较高、简单可行 ,可用于机械工程实时监测。 相似文献
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Xiang Jia-wei Chen Xue-feng He Zheng-jia He Yu-min 《Frontiers of Mechanical Engineering in China》2006,1(2):177-182
The model-based forward and inverse problems in the diagnosis of structural crack faults were studied. The forward problem
is to solve the natural frequencies through a cracked structural model and the inverse problem is to quantitatively determine
the crack parameters using the experimental testing frequencies. Then, the one-dimensional crack element of B-spline wavelet
on the interval (BSWI) was built to solve the forward problem. Contour plots of normalized crack location versus normalized
crack size were plotted by using the first three natural frequencies as the inputs. The intersection of the three curves predicted
the normalized crack location and size. The experimental study verified the validity of the wavelet-based crack element in
solving crack singular problems to overcome the disadvantages of the traditional finite element method (FEM), such as low
efficiency, insufficient accuracy, slow convergence to correct solutions, etc. At the same time, it had adequate identification
precision. The new method can be applied to prognosis and quantitative diagnosis of incipient crack.
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Translated from Journal of Mechanical Strength, 2005, 27 (2) (in Chinese) 相似文献
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Second Generation Wavelet Finite Element and Rotor Cracks Quantitative Identification Method 总被引:2,自引:1,他引:1
The presence of cracks in the rotor is one of the most dangerous and critical defects for rotating machinery. Defect of fatigue cracks may lead to long out-of-service periods, heavy damages of machines and severe economic consequences. With the method of finite element, vibration behavior of cracked rotors and crack detection was received considerable attention in the academic and engineering field. Various researchers studied the response of a cracked rotor and most of them are focused on the crack detection based on vibration behavior of cracked rotors. But it is often difficult to identify the crack parameters quantitatively. Second generation wavelets (SGW) finite element has good ability in modal analysis for singularity problems like a cracked rotor. Based on the fact that the feature of SGW could be designed depending on applications, a multiresolution finite element method is presented. The new model of SGW beam element is constructed. The first three natural frequencies of the rotor with different crack location and size were solved with SGW beam elements, and the database for crack diagnosis is obtained. The first three metrical natural frequencies are employed as inputs of the database and the intersection of the three frequencies contour lines predicted the normalized crack location and size. With the Bently RK4 rotor test rig, rotors with different crack location and size are tested and diagnosed. The experimental results denote the cracks quantitative identification method has higher identification precision. With SGW finite element method, a novel method is presented that has higher precision and faster computing speed to identify the crack location and size. 相似文献
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H.B. Dong X.F. Chen B. Li K.Y. Qi Z.J. He 《Mechanical Systems and Signal Processing》2009,23(3):869-883
In this paper, a new method based on high-precision modal parameter identification method and wavelet finite element (WFE) model is presented to determine the depth and location of a transverse surface crack in a rotor system. The rotor system is modeled using finite element method of B-spline wavelet on the interval (FEM BSWI), while the crack is equivalent as a weightless rotational spring. Additionally, a novel method based on empirical mode decomposition (EMD) and Laplace wavelet is proposed to acquire modal parameters with high precision, which is implemented to improve the precision of crack identification. By providing the first three natural frequencies, contours for the specified natural frequency are plotted in the same coordinate, and the intersection of the three curves predicts the crack location and size. The experimental results indicate that the proposed method can accurately identify the position and depth of different cracks. The effectiveness and reliability of the proposed method is verified. 相似文献
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基于Bernoulli-Euler梁振动理论,以等效弹簧模拟裂纹引起的局部软化效应,利用传递矩阵法推导阶梯悬臂梁振动频率的特征方程,对于含多个裂纹以及复杂边界条件的阶梯梁,仅需求解4×4的行列式即可获得相应的频率特征方程。直接利用该特征方程,提出两种有效估计裂纹参数的方法———等值线法和目标函数最小化法,并应用两段阶梯悬臂梁的数值算例说明方法的有效性。算例结果表明,只需结构前三阶频率即可识别裂纹位置和深度。应用“零设置”可减小计算频率与理论频率不相等对识别结果的影响。等值线法可以直观给出裂纹位置和裂纹深度参数,目标函数最小化法可给出最优的裂纹参数结果,并且该方法可推广应用到含多个裂纹复杂梁(如非完全固支、弹性支撑等)结构的裂纹参数识别中。 相似文献
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局部柔度可描述结构上出现的裂纹,结构的模态参数将随着裂纹的扩展而改变,利用这一变化可辨识出裂纹发生的位置和深度。由此,建立了一种基于局部柔度变化的管道裂纹定量识别方法。该方法通过将管道结构沿径向离散为一系列依次嵌套的薄壁环,从而求得裂纹引起的局部柔度的变化规律,进而获得局部柔度与管道固有频率的特征关系,绘制裂纹管道的各阶固有频率曲面。采用实测前3阶固有频率去截取相应的固有频率曲面,获得各阶频率等高线,利用其交点定量诊断裂纹的位置与深度。实验结果验证了该方法的有效性。 相似文献
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Jing Liu Weidong Zhu Panos G. Charalambides Yimin Shao Yongfeng Xu Kai Wu Huifang Xiao 《机械工程学报(英文版)》2016,29(1):163-179
As one of the main failure modes, embedded cracks occur in beam structures due to periodic loads. Hence it is useful to investigate the dynamic characteristics of a beam structure with an embedded crack for early crack detection and diagnosis. A new four-beam model with local flexibilities at crack tips is developed to investigate the transverse vibration of a cantilever beam with an embedded horizontal crack; two separate beam segments are used to model the crack region to allow opening of crack surfaces. Each beam segment is considered as an Euler-Bernoulli beam. The governing equations and the matching and boundary conditions of the four-beam model are derived using Hamilton's principle. The natural frequencies and mode shapes of the four-beam model are calculated using the transfer matrix method. The effects of the crack length, depth, and location on the first three natural frequencies and mode shapes of the cracked cantilever beam are investigated. A continuous wavelet transform method is used to analyze the mode shapes of the cracked cantilever beam. It is shown that sudden changes in spatial variations of the wavelet coefficients of the mode shapes can be used to identify the length and location of an embedded horizontal crack. The first three natural frequencies and mode shapes of a cantilever beam with an embedded crack from the finite element method and an experimental investigation are used to validate the proposed model. Local deformations in the vicinity of the crack tips can be described by the proposed four-beam model, which cannot be captured by previous methods. 相似文献
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Jinhee Lee 《Journal of Mechanical Science and Technology》2010,24(3):801-804
A method to detect a crack in a beam is presented. The crack is not modeled as a massless rotational spring, and the forward
problem is solved for the natural frequencies using the boundary element method. The inverse problem is solved iteratively
for the crack location and the crack size by the Newton-Raphson method. The present crack identification procedure is applied
to the simulation cases which use the experimentally measured natural frequencies as inputs, and the detected crack parameters
are in good agreements with the actual ones. The present method enables one to detect a crack in a beam without the help of
the massless rotational spring model. 相似文献