The abrupt fracture of vibrating screen lower beam would make the whole coal preparation product line shutting down and result in large economic *** this paper,the evolution law between the transfer function of vibrat...
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The abrupt fracture of vibrating screen lower beam would make the whole coal preparation product line shutting down and result in large economic *** this paper,the evolution law between the transfer function of vibrating screen lower beam and the emergence and growth of the crack is researched,and a quick detection method is proposed based on the technical method of metal magnetic memory test(MMMT). The experimentation and spot application results show that the method is efficient,and it could achieve the earlycrack fault quick detection of vibrating screen lower *** application could decrease and even avoid the lower beam abrupt fracture occurrence of the vibrating screen.
This study introduces an advanced non-destructive inspection (NDI) technique employing Phased Array Ultrasonic Testing (PAUT) to identify early-stage damage in welds located within orthotropic steel bridge decks. Orth...
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This study introduces an advanced non-destructive inspection (NDI) technique employing Phased Array Ultrasonic Testing (PAUT) to identify early-stage damage in welds located within orthotropic steel bridge decks. Orthotropic steel bridge decks, renowned for their lightweight and resilient characteristics, are extensively employed in contemporary bridge construction endeavors. Nonetheless, ensuring their structural soundness and detecting flaws holds paramount importance in guaranteeing safety and durability. The initial phases of crack propagation pose challenges for detection through conventional visual inspection methods due to the minute scale of crack dimensions. Nevertheless, adopting preemptive measures during these nascent stages of crack propagation is imperative for reinforcing maintenance protocols and bolstering structural safety measures. A PAUT protocol tailored to the specific characteristics of steel bridge structures is developed through a comprehensive analysis of current non-destructive testing methodologies. Experimental investigations using a specimen validate PAUT's efficacy in detecting cracks in various weld types, including those between U-ribs and deck plates, U-shaped splice plates and deck plates, and floor beams and deck plates. The results demonstrate PAUT's ability to identify early damage within steel structures and welds that are not visible to the naked eye, accurately locate defects, determine their size, and identify the direction of crack propagation. The innovative application of PAUT on orthotropic steel bridge decks reflects the maturation and advancement of this technology, offering an effective non-destructive approach for earlydetection of cracking damage. Prompt identification of potential issues facilitates timely maintenance and reinforcement efforts, ultimately minimizing the risk of human and economic losses.
This paper presents an introduction to the dynamic behaviour of a one disc rotor (Laval rotor) having a transverse crack in the elastic shaft. With the aid of a simple crack model the non-linear equations of motion ar...
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This paper presents an introduction to the dynamic behaviour of a one disc rotor (Laval rotor) having a transverse crack in the elastic shaft. With the aid of a simple crack model the non-linear equations of motion are derived. Due to the weight dominance in the elastic deflection of the horizontal shaft the equations can be simplified to linear but time-variant equations. The stability analysis is carried out with Floquet's method and the results are presented in an overview diagram. The forced vibrations due to crack and unbalance are discussed in much detail. The orbit decomposition into forward and backward whirls (two-sided spectral order analysis) turns out to be a helpful tool for the understanding the complicated dynamic phenomena. Some hints for crackdetection are given. (C) 2007 Elsevier Ltd. All rights reserved.
Due to notches, welds are most critical regarding fatigue failure within cyclic loaded constructions. Therefore, various post-weld-treatment techniques like post-weld treatment by high-frequency mechanical impact (HFM...
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Due to notches, welds are most critical regarding fatigue failure within cyclic loaded constructions. Therefore, various post-weld-treatment techniques like post-weld treatment by high-frequency mechanical impact (HFMI) treatment have been invented to improve the fatigue strength of welded details. The benefit, resulting from HFMI treatment, has already been proven by numerous studies. Since a manual HFMI treatment must be performed by a skilled and trained person to ensure an acceptable treatment quality, an automated application of HFMI treatment is supposed to result in a more reliable and consistent treatment result, which does not depend on the operator. Furthermore, a robotic application of HFMI treatment enables an economic implementation of HFMI treatment of automated welded constructions like offshore wind energy converters and various mechanical components, as these parts do not have to be taken out of the production chain to manually perform HFMI treatment. This paper focuses on the experimental investigation of the fatigue behaviour of automated HFMI-treated welds, using a developed robotic application of the HiFIT device (specific HFMI tool).
The model-based method plays an essential role in crackdetection of rotor systems. To improve the reliability and accuracy of model-based method in rotor crackdetection, this paper proposes a coupled multi-crack rot...
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The model-based method plays an essential role in crackdetection of rotor systems. To improve the reliability and accuracy of model-based method in rotor crackdetection, this paper proposes a coupled multi-crack rotor model by considering the coupling effect between cracks under complex excitations as an additional flexibility. The systemic stiffness matrix is derived based on the Timoshenko beam theory and fracture mechanics, in which a detailed description of the coupling mechanism between cracks is presented. The systemic stiffness variation with rotation angles and the effects of crack orientation angles, unbalance orientation angles, and crack depths on dynamic characteristics of the coupled multi-crack rotor are analysed at 1/3 and 1/2 subcritical speeds. The complex nonlinearity induced by the coupling effect between cracks is responsible for the dynamic differences between the coupled and uncoupled models of a multi-crack rotor. The magnitudes of most of 2X and 3X components (X is the rotating frequency of rotor system) of the coupled rotor model are nearly twice as those of the uncoupled model. The prominent super-harmonic components and orbits' morphological features of the coupled multi-crack rotor model are shown to be suitable for early crack detection and crack parameter identification. The theoretical findings of the proposed coupled model show an excellent agreement with the experimental results. This work can give confidence in the applications of the model-based method in health monitoring and multi-crackdetection for actual rotors.
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