汽車起重機關鍵結構件損傷的聲發(fā)射特性與源識別方法研究
發(fā)布時間：2018-08-08 17:25
【摘要】：汽車起重機作為一種被廣泛應用的特種設備，在中國數量多、增速快。且由于其關鍵結構件長期受交變載荷的作用，所處工作環(huán)境惡劣，因此易產生裂紋、銹蝕等損傷缺陷，從而造成整機的災難性事故，因此對其進行損傷檢測與分析研究十分必要。由于聲發(fā)射技術能夠檢測金屬材料早期裂縫產生和擴展過程，使其非常適合作為結構件局部損傷的監(jiān)測方法�，F(xiàn)階段對汽車起重機的關鍵結構件進行局部損傷監(jiān)測還處于初級階段，對其聲發(fā)射源特性缺乏清晰的認識，未形成行之有效的方法與策略對關鍵結構件局部損傷及危險狀態(tài)進行預警，而且對工作環(huán)境下汽車起重機局部損傷聲發(fā)射源的識別有待于進一步的研究。因此結合國家重點高技術研究發(fā)展計劃開展了相關課題的研究工作，具體研究內容包括： (1)通過汽車起重機常用Weldox960鋼和HG70鋼母材及焊接試件拉伸破壞的聲發(fā)射監(jiān)測實驗，對材料損傷過程中聲發(fā)射信號特征參數變化規(guī)律及其對損傷行為的敏感性進行了研究，并采用時差濾波方法實現(xiàn)了裂紋損傷聲發(fā)射信號的有效分離。研究結果表明：有效值電壓（RMS電壓）對材料屈服變形損傷較為敏感，據此提出了一種基于RMS電壓局部極小值的材料屈服變形損傷預警方法，其對HG70鋼母材預警應力比為75%、對Weldox960鋼母材為90%左右；而質心頻率、峰值頻率及幅值的變化可有效監(jiān)測裂紋萌生及擴展過程。 (2)汽車起重機服役過程中其多個部件受彎曲載荷作用，，因此在實驗室條件下，采用聲發(fā)射技術監(jiān)測了其常用鋼母材及焊接缺陷試件的三點彎曲實驗過程,研究了不同損傷階段的聲發(fā)射特征，并提出了一種基于最小改進b值（最小Ib值）的裂紋損傷預警方法。實驗結果表明：最小Ib值可以實現(xiàn)對焊接裂紋擴展損傷的預警；幅值、振鈴計數等多個特征參數值對母材損傷變形過程較為敏感；而信號能量計數值、質心頻率等多個特征參數可作為焊接試件裂紋擴展的敏感特征指標。 (3)提出了一種聲發(fā)射檢測點優(yōu)化設計及局部損傷定位方法，該方法首先進行汽車起重機結構件的建模和有限元分析，然后結合分析結果與加載應力實驗確定應力集中及易損傷區(qū)，以此為依據確定聲發(fā)射監(jiān)測的重點部位，最后進行聲發(fā)射檢測實驗方案及四探頭陣列的聲發(fā)射定位方法設計。實驗結果表明：該方法準確確定了聲發(fā)射監(jiān)測的兩個重點區(qū)域，斷鉛模擬實驗及起重機加載實驗均驗證了該方法能夠對吊臂等關鍵結構件上的損傷源實現(xiàn)準確定位。 (4)提出了一種基于混合特征向量與最小二乘支持向量機的汽車起重機典型聲發(fā)射源識別方法。首先結合小波包分析，信號時域及頻域特征分析生成聲發(fā)射混合特征向量，然后結合類間距離評估因子方法對生成的特征向量進行降維處理，再將其作為輸入值帶入構造的最小二乘支持向量機識別模型完成識別分析。通過對工業(yè)現(xiàn)場常見6種典型聲發(fā)射源數據識別結果表明：該模型對不同聲發(fā)射源的識別率均超過了93%，而且相較于神經網絡方法有更高的識別精度。 通過論文的研究，有助于加深對汽車起重機關鍵結構件損傷聲發(fā)射源的全面了解，為相關聲發(fā)射檢測標準的制定提供理論及實驗基礎，對加速聲發(fā)射技術在相關領域的推廣應用具有重大的現(xiàn)實意義。
[Abstract]:As a kind of special equipment widely used, automobile crane is widely used in China, and its speed is fast. And because its key structural parts are subjected to alternating load for a long time, the working environment is bad, so it is easy to produce crack, corrosion and other damage defects, which cause catastrophic accidents of the whole machine, so the damage detection and analysis of it is ten. Because acoustic emission technology can detect the early crack generation and expansion process of metal materials, it is very suitable to be used as a monitoring method for local damage of structural parts. At the present stage, the local damage monitoring of the key structural parts of the truck crane is still in the primary stage, and the characteristics of the acoustic emission source are lack of clear understanding, and no line is formed. The effective methods and strategies are used to predict the local damage and dangerous state of the key structure, and the identification of the acoustic emission source of the local damage of the truck crane in the working environment needs further study.
(1) through the acoustic emission monitoring experiment on the tensile failure of Weldox960 steel and HG70 steel and welding specimen, the characteristics of the characteristic parameters of acoustic emission signals and the sensitivity of the damage behavior in the process of material damage are studied, and the effective separation of the acoustic emission signals from the crack damage is realized by the time difference filter method. The results show that the effective value voltage (RMS voltage) is more sensitive to the damage of material yield deformation. Based on this, an early warning method for yield deformation damage of materials based on the local minimum of RMS voltage is proposed. The early warning stress ratio of HG70 steel is 75%, and the base material of Weldox960 steel is about 90%; and center frequency, peak frequency and amplitude The process of crack initiation and propagation can be monitored effectively.
(2) many parts of the truck crane are subjected to bending load during the service of the truck crane. So under the laboratory conditions, the acoustic emission technique is used to monitor the three point bending test process of its common steel material and welding defects, and the acoustic emission characteristics of different damage stages are studied, and a minimum improved b value (minimum Ib value) is proposed. The experimental results show that the minimum Ib value can realize the early warning of the weld crack propagation damage; the amplitude, the ringing count and other characteristic parameters are more sensitive to the damage and deformation process of the material, and the number of characteristic parameters such as the signal energy meter and the centroid frequency can be used as the sensitive characteristic of the crack propagation in the welding specimen. Indicators.
(3) an optimization design of acoustic emission detection point and a local damage location method are proposed. First, the modeling and finite element analysis of the structural parts of the truck crane are first carried out. Then the stress concentration and the vulnerable zone are determined by the analysis results and the loading stress experiments. In this way, the key parts of the acoustic emission monitoring are determined and the sound is sent to the sound. The experiment scheme and the acoustic emission positioning method of the four probe array are designed. The experimental results show that the method accurately determines the two key areas of acoustic emission monitoring. The simulation experiment of lead breaking and the loading experiment of the crane verify that the method can accurately locate the damage source on the key structural parts such as the crane arm.
(4) a typical acoustic emission source identification method based on hybrid eigenvector and least squares support vector machine is proposed. First, combined with wavelet packet analysis, the acoustic emission mixed eigenvectors are generated in time domain and frequency domain characteristic analysis, and then the generated eigenvector is reduced with the method of inter class distance assessment factor. The identification results of 6 typical acoustic emission sources in industrial field show that the recognition rate of the model is more than 93% for the different acoustic emission sources and has a higher recognition accuracy compared with the neural network method.
Through the research of this paper, it is helpful to deepen the comprehensive understanding of the damage acoustic emission source of the key structural parts of the automobile crane, and provide the theoretical and experimental basis for the formulation of the related acoustic emission testing standards. It has great practical meaning to the promotion and application of the accelerated acoustic emission technology in the related fields.
【學位授予單位】：北京理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TH213.6
本文編號：2172491
[Abstract]:As a kind of special equipment widely used, automobile crane is widely used in China, and its speed is fast. And because its key structural parts are subjected to alternating load for a long time, the working environment is bad, so it is easy to produce crack, corrosion and other damage defects, which cause catastrophic accidents of the whole machine, so the damage detection and analysis of it is ten. Because acoustic emission technology can detect the early crack generation and expansion process of metal materials, it is very suitable to be used as a monitoring method for local damage of structural parts. At the present stage, the local damage monitoring of the key structural parts of the truck crane is still in the primary stage, and the characteristics of the acoustic emission source are lack of clear understanding, and no line is formed. The effective methods and strategies are used to predict the local damage and dangerous state of the key structure, and the identification of the acoustic emission source of the local damage of the truck crane in the working environment needs further study.
(1) through the acoustic emission monitoring experiment on the tensile failure of Weldox960 steel and HG70 steel and welding specimen, the characteristics of the characteristic parameters of acoustic emission signals and the sensitivity of the damage behavior in the process of material damage are studied, and the effective separation of the acoustic emission signals from the crack damage is realized by the time difference filter method. The results show that the effective value voltage (RMS voltage) is more sensitive to the damage of material yield deformation. Based on this, an early warning method for yield deformation damage of materials based on the local minimum of RMS voltage is proposed. The early warning stress ratio of HG70 steel is 75%, and the base material of Weldox960 steel is about 90%; and center frequency, peak frequency and amplitude The process of crack initiation and propagation can be monitored effectively.
(2) many parts of the truck crane are subjected to bending load during the service of the truck crane. So under the laboratory conditions, the acoustic emission technique is used to monitor the three point bending test process of its common steel material and welding defects, and the acoustic emission characteristics of different damage stages are studied, and a minimum improved b value (minimum Ib value) is proposed. The experimental results show that the minimum Ib value can realize the early warning of the weld crack propagation damage; the amplitude, the ringing count and other characteristic parameters are more sensitive to the damage and deformation process of the material, and the number of characteristic parameters such as the signal energy meter and the centroid frequency can be used as the sensitive characteristic of the crack propagation in the welding specimen. Indicators.
(3) an optimization design of acoustic emission detection point and a local damage location method are proposed. First, the modeling and finite element analysis of the structural parts of the truck crane are first carried out. Then the stress concentration and the vulnerable zone are determined by the analysis results and the loading stress experiments. In this way, the key parts of the acoustic emission monitoring are determined and the sound is sent to the sound. The experiment scheme and the acoustic emission positioning method of the four probe array are designed. The experimental results show that the method accurately determines the two key areas of acoustic emission monitoring. The simulation experiment of lead breaking and the loading experiment of the crane verify that the method can accurately locate the damage source on the key structural parts such as the crane arm.
(4) a typical acoustic emission source identification method based on hybrid eigenvector and least squares support vector machine is proposed. First, combined with wavelet packet analysis, the acoustic emission mixed eigenvectors are generated in time domain and frequency domain characteristic analysis, and then the generated eigenvector is reduced with the method of inter class distance assessment factor. The identification results of 6 typical acoustic emission sources in industrial field show that the recognition rate of the model is more than 93% for the different acoustic emission sources and has a higher recognition accuracy compared with the neural network method.
Through the research of this paper, it is helpful to deepen the comprehensive understanding of the damage acoustic emission source of the key structural parts of the automobile crane, and provide the theoretical and experimental basis for the formulation of the related acoustic emission testing standards. It has great practical meaning to the promotion and application of the accelerated acoustic emission technology in the related fields.
【學位授予單位】：北京理工大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TH213.6
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