Approach to health monitoring and assessment of rolling bearing

A bearing is the most common and vital element in the majority of rotating machinery. Condition monitoring and performance assessment of rolling bearing have recently attracted significant attention. This paper proposes a set of methodologies to realize the efficient health monitoring and assessment of rolling bearing. Considering the difficulties and disadvantages in detecting the fault signal of rolling bearing with background noise, this paper presents a method based on the Duffing oscillator and Hu’s moment invariant for health monitoring. The proposed method mainly combines the chaotic oscillator and moment invariant, fully utilizing the sensitivity of the former to detect the fault signal and taking the latter as a quantitative index for fault identification without the need for a qualitative artificial judgment on the Duffing oscillator phase trajectory map. To provide the optimal performance of Hu’s moment invariant in automatic recognition for the phase trajectory map, the influencing principle of different oscillator parameters was analyzed. Therefore, the health state of rolling bearing can be automatically monitored by quantitatively identifying the transition state of the phase trajectory map. A health assessment model was established to evaluate the health state of bearings. Wavelet packet transform was used to extract the features (approximate entropy) of bearing vibration signal, which were input into the self-organizing map (SOM) network. The health state of rolling bearings was then assessed using the SOM network and confidence values. A case study on health monitoring and assessment for rolling bearing was conducted to demonstrate the effectiveness and accuracy of the proposed methods

Study on damage mechanism and treatment of water sprayed roof in Jurassic stratum roadway

The roof of the Jurassic main coal seam in western China generally contained low level weak rich water layer, which led to the long-term watering of the roof of the coal roadway especially the roof anchor cable hole and the reduction of the roof surrounding rock strength and the roof support effect, and affected the safety of the coal roadway roof. In order to study the damage mechanism and control measures of the water sprayed roof, the No.414106 auxiliary transportation water spraying area of Yangjiacun Coal Mine of Shuangxin Mining in Inner Mongolia was taken as the research object. Through field investigation and roof drilling sampling, it could be seen that there were obvious water conducting cracks in the area 4m above the roof of the roadway in the synclinal area. The water flowing from the anchor cable hole was in a linear water spraying state. The roof surrounding rock had a large degree of deflection, and some anchor cable anchorage sections were separated from the surrounding rock. The mineral composition analysis and water physical test showed that the clay minerals in the roof sandy mudstone contain up to 73% kaolinite, and the softening coefficient is 0.162, which had obvious water softening characteristics. At the initial stage, the roof of the coal roadway in the water spraying area was mainly destroyed by hydrostatic pressure, and the water softening property reduced the mechanical properties of the fracture structural plane, which led to the expansion of the size of the surrounding rock fractures in shear under the action of hydrostatic pressure. In the later stage, the roof surrounding rock was mainly destroyed by hydrodynamic pressure, which was mainly manifested in the deformation and expansion of fracture structural plane, displacement of fracture fillings, piping, etc. The destruction speed of roof surrounding rock was gradually accelerated. The whole process of surrounding rock of water drenching roadway roof from ground pressure appearance deformation and crack softening expansion to piping corrosion failure was analyzed. According to the main forms of the surrounding rock failure of roof drilling (physical softening, seepage failure, suction corrosion expansion failure, scouring deformation failure), it was divided into four different stages. The criteria for determining the development stage of roof failure of roadway drenching water had been formed with the main forms of roof drilling surrounding rock failure, the flow state of the roof anchor cable hole, roof surrounding rock fracture development characteristics and water control reinforcement principles as the key indicators. Combined with the site conditions, the 414106 auxiliary transportation water spraying area was the Ⅲ stage of the development of spraying roof damage. The structural form of anchor cable sealing grouting (drainage) and the principle of “deep hole drainage + shallow water sealing + deep reinforcement + high pressures support” were proposed for the roof of the roadway in the spraying area. An integrated reinforcement scheme of anchoring, sealing and grouting, which combined the reinforcement of high pre-tightened long anchor cables and sealing and grouting on the roof of the roadway in the water-spraying area, had been formulated. According to the field industrial test and rock pressure monitoring, the effect of roof water control and surrounding rock reinforcement was achieved

Research progress of drug eluting balloon in arterial circulatory system

The arterial circulatory system diseases are common in clinical practice, and their treatment options have been of great interest due to their high morbidity and mortality. Drug-eluting balloons, as a new type of endovascular interventional treatment option, can avoid the long-term implantation of metal stents and is a new type of angioplasty without stents, so drug-eluting balloons have better therapeutic effects in some arterial circulatory diseases and have been initially used in clinical practice. In this review, we first describe the development, process, and mechanism of drug-eluting balloons. Then we summarize the current studies on the application of drug-eluting balloons in coronary artery lesions, in-stent restenosis, and peripheral vascular disease. As well as the technical difficulties and complications in the application of drug-eluting balloons and possible management options, in order to provide ideas and help for future in-depth studies and provide new strategies for the treatment of more arterial system diseases

The research about high-dynamic and low-gray target image differential capture technology based on laser active detection

Abstract The extraction and capture of the target by the medium-long wave infrared optical system is mainly achieved based on the gray difference between the target image and the background image. Under complex background conditions, such as air-to-ground alarms or target detection and capture will be strongly disturbed by the background environment. Especially under dynamic conditions, the background and the target are in a rapid change, how to detect real-time ground-to-air missile seeker and other weak targets is very difficult. It is one of the technical difficulties in the current image processing field to quickly locate and extract from high-dynamic low-contrast grayscale images. In this paper, a fast differential capture method for cat eye echo images using a highly active and low-gray optical target such as a seeker using laser active illumination detection is proposed to achieve efficient capture and extraction of the target. Using a 3.5-um band, 1 W average power laser to illuminate medium-wave infrared-waveband seeker with a 100 mm aperture, to achieve echo imaging of 2–4 orders of magnitude higher than traditional diffuse reflection, using 500 Hz large frame rate medium-wave imaging to achieve quick alignment and fast differential imaging of the target background. From the simulation and experimental results, this image processing method can effectively improve the optical system’s detection capabilities and capture speed and effectively solve the problems of low-gray level dynamic target detection and high-precision positioning in complex background

Analysis of dynamic response of a restraining system for a powerless advancing ship based on the kane method

Following general explanations of the working principles of different existing retardation systems to restrain an advancing powerless ship the principles of a new overhead retardation system are presented. A two dimensional simplified model of the activated overhead system is formulated based on Huston’s interpretation of the Kane methodology. Reduced Kane equations are used in the actual simulation, once initial conditions and mechanical analysis of constituent elements have been formulated. Having presented the computational process the various velocity, motion and joint constraint force characteristics of the anchor, the ship and the other elements are monitored in the time domain for the duration of the retardation process. Validation of the Kane based method is established utilising the conservation law and the Lagrangian based formulation of the retardation system within the ADAMS software. The results indicate that a peak value of constraint will occur because of the sudden movement of anchor and this peak is affected significantly by initial ship speed. Variation in anchor chain, overall cable length and its horizontal projected length has little influence upon retardation system performance, whilst the changes of sea bed friction, anchor mass, water depth, initial ship velocity and ship mass will make retardation behaviour different

Improving scratch-resistance and wear-resistance of VN film by deep cryogenic treatment with liquid nitrogen

Improving scratch-resistance and wear-resistance of VN film by deep cryogenic treatment with liquid nitroge

Fractal characteristics of pore-throat structure in tight sandstones using high-pressure mercury intrusion porosimetry

Microcosmic pore-throat structure is an important factor affecting the characteristics of sandstone reservoirs.However, the pore-throat of tight sandstone is complex and heterogeneous, which is difficult to be effectively characterized by conventional tests.Therefore, it is necessary to use fractal theory to research the pore-throat structure of tight sandstone.In this study, through high-pressure mercury injection porosimetry and fractal theory, the pore-throat structure and fractal dimension characteristics of the Chang 7 tight sandstones in Jiyuan area of the Ordos Basin are studied, and the relationship between infection points on the fractal curves and pore-throat structure are discussed.And combined with casting thin section and scanning electron microscope, the causes of fractal characteristics from pore-throat are analyzed.The results show that there are obvious infection points on fractal curves, and the infection point is the peak value of pore size distribution, which representes the transition from the large pore-throat with good connectivity to the small pore-throat with poor connectivity.The average fractal dimension of small pore-throat is 2.24, and that of large pore-throat is 4.65.The heterogeneity of large pore-throat is obviously stronger than that of the small pore-throat.And the correlation between fractal dimensions of small pore-throat and pore-throat structure is good.The small pore-throats of tight sandstones mainly consist of intercrystalline pores and throats, which have poor connectivity, small radius and weak influence by diagenesis.Therefore, the fractal dimensions of the small pore-throat are low.The large pore-throats of tight sandstone mainly consist of residual intergranular pores and dissolution pores.The large pore-throat has good connectivity, large radius and obvious transformation by diagenesis.Therefore, the fractal dimension of the large pore-throat is high