基于动态滑动步长改进LMD算法的砂浆脱空识别

Mortar Void Identification Based on the Improved LMD with Dynamic Moving Step

水泥沥青砂浆作为板式无砟轨道的重要结构,在列车高频动载与温度荷载共同作用下,极易发生脱空损伤。根据轮对加速度变化特征可实现砂浆脱空快速、准确定位。利用自适应动态滑动步长改进局部均值分解算法,将轮对垂向加速度分解为一系列乘积函数分量。依据峭度变化规律选取最能反映砂浆脱空特征的第1个乘积函数分量,并求其瞬时能量和标准化瞬时能量以增强砂浆脱空特征。根据瞬时能量和标准化瞬时能量的包络函数是否存在离群值判断砂浆是否脱空。结果表明:当砂浆脱空长度不超过0.30 m时,瞬时能量的包络函数在脱空处未出现离群值,导致“漏判”,而标准化瞬时能量的包络函数在脱空和未脱空处均出现离群值,导致“误判”;当砂浆脱空长度不小于0.65 m时,瞬时能量和标准化瞬时能量的包络函数均只在脱空处出现离群值,可准确定位砂浆脱空。通过车辆结构响应识别砂浆脱空,可有效缓解轨道损伤检测压力,提高车辆运营效率。

As an important component of the ballastless slab track,cement asphalt mortar is prone to void damage under the combined action of high-frequency train loads and temperature loads.The mortar void can be located quickly and accurately according to the change characteristics of wheelset accelerations.The vertical wheelset acceleration was decomposed into a series of product functions via local mean decomposition improved by adaptive dynamic moving step.Based on the change of kurtosis,the first product function that can best reflect the mortar void characteristics was selected,and its instantaneous energy and standardized instantaneous energy were calculated to enhance the mortar void feature.By analyzing whether there are outliers in the envelope functions of instantaneous energy and standardized instantaneous energy,whether the mortar is damaged can be determined.The results show that when the mortar void length is no more than 0.30 m,there is no outlier in envelop function of instantaneous energy at the mortar void position,resulting in“missing judgment”;and the envelop function of standard instantaneous energy has outliers both at the void and non-void position,resulting in“misjudgment”.When the mortar void length is no less than 0.65 m,the envelope functions of instantaneous energy and standardized instantaneous energy only have outliers at the mortar void position,which can be directly used to locate the mortar void position.Identifying mortar void through responses of vehicle structures can effectively alleviate the pressure of track damage detection and improve vehicle operation efficiency.