Search results for: butterfly valve vibration analysis

Authors: Gupta Rajesh, Paudel Sagar, Sharma Utkarsh, Singh Amit Kumar

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Thermal stratification has drawn much attention because of the malfunctions at various nuclear plants in U.S.A that raised significant safety concerns. The concerns due to this phenomenon relate to thermal stresses in branch pipes connected to the reactor coolant system piping. This stress limits the lifetime of the piping system, and even leading to penetrating cracks. To assess origin of valve damage in the pipeline, it is essential to determine the effect of turbulence penetration on valve leakage; since stratified flow is generally generated by turbulent penetration or valve leakage. As a result, we concluded with the help of coupled fluent-structural analysis that the pipe with less turbulence has less chance of failure there by requiring less maintenance.

Keywords: nuclear reactor coolant system, thermal stratification, turbulent penetration, coupled fluent-structural analysis, Von-Misses stress

Procedia PDF Downloads 257

Authors: Munirah Ismail, Joon Hock Yeo

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Paediatric patients who require ventricular outflow tract reconstruction usually need valve construction to prevent valvular regurgitation. They would face problems like lack of suitable, affordable conduits and the need to undergo several operations in their lifetime due to the short lifespan of existing valves. Their natural growth and development are also of concern, even if they manage to receive suitable conduits. Current prosthesis including homografts, bioprosthetic valves, mechanical valves, and bovine jugular veins either do not have the long-term durability or the ability to adapt to the growth of such patients. We have developed a new design of bi-leaflet valve. This new technique accommodates patients’ annular size growth while maintaining valvular patency. A mock circulatory system was set up to assess the hemodynamic performance of the bi-leaflet pulmonary valve. It was found that the percentage regurgitation was acceptable and thus, validates this novel concept.

Keywords: bi-leaflet pulmonary valve, pulmonary heart valve, tetralogy of fallot, mock circulatory system

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Authors: Aymen Laadhari, Gábor Székely

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In this work, the hemodynamics in the sinuses of Valsalva after Transcatheter Aortic Valve Implantation is numerically examined. We focus on the physical results in the two-dimensional case. We use a finite element methodology based on a Lagrange multiplier technique that enables to couple the dynamics of blood flow and the leaflets’ movement. A massively parallel implementation of a monolithic and fully implicit solver allows more accuracy and significant computational savings. The elastic properties of the aortic valve are disregarded, and the numerical computations are performed under physiologically correct pressure loads. Computational results depict that blood flow may be subject to stagnation in the lower domain of the sinuses of Valsalva after Transcatheter Aortic Valve Implantation.

Keywords: hemodynamics, simulations, stagnation, valve

Procedia PDF Downloads 267

Authors: Farshad Ghazalian, Laleh Hakemi, Lotfali Pourkazemi, Maryam Ameri, Seyed Hossein Alavi

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Background: The use of whole body vibration (WBV) as an exercise method has rapidly increased over the last decade. The aim of this study was to evaluate long term effects of different amplitudes of whole body vibration training with progressive frequencies on lipid profile of young healthy men. Materials and methods: Thirty three healthy male students were divided randomly in three groups: high amplitude vibration group (n=11), low amplitude vibration group (n=11), and control group (n=11). The vibration training consisted of 5 week whole-body vibration 3 times a week with amplitudes 4 and 2 mm and progressive frequencies from 25 Hz with increments of 5 Hz weekly. Concentrations TG, HDL, LDL, cholesterol, and VLDL before and after 5 weeks of training were measured in plasma samples. Statistical analysis was done using one way analysis of variance. P<0.05 was considered statistically significant. Results: The most important result of the present study is finding no favorable changes of 5-week vibration training with different amplitudes on blood lipid profiles. Discussion and conclusions: It was emphasized that in vibration training there should be a relationship between intensity and volume of exercise and lipid responses in order to improve blood lipoprotein profiles.

Keywords: long term, body, vibration training, lipid

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Authors: Pradeep A. G, Gorantla Giridhar, Vijay Turaga, Vinod Srinivasa

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The major problem in the flow control valve is of lower Cv, which will reduce the overall efficiency of the flow circuit. Designers are continuously working to improve the Cv of the valve, but they need to validate the design ideas they have regarding the improvement of Cv. The traditional method of prototyping and testing takes a lot of time. That is where CFD comes into the picture with very quick and accurate validation along with visualization, which is not possible with the traditional testing method. We have developed a method to predict Cv value using CFD analysis by iterating on various Boundary conditions, solver settings and by carrying out grid convergence studies to establish the correlation between the CFD model and Test data. The present study investigates 3 different ideas put forward by the designers for improving the flow capacity of the valves, like reducing the cage thickness, changing the port position, and using the parabolic plug to guide the flow. Using CFD, we analyzed all design changes using the established methodology that we developed. We were able to evaluate the effect of these design changes on the Valve Cv. We optimized the wetted surface of the valve further by suggesting the design modification to the lower part of the valve to make the flow more streamlined. We could find that changing cage thickness and port position has little impact on the valve Cv. The combination of optimized wetted surface and introduction of parabolic plug improved the Flow capacity (Cv) of the valve significantly.

Keywords: flow control valves, flow capacity (Cv), CFD simulations, design validation

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Authors: Pisit Poolprasert, Auttpol Nakwa, Keerati Tanruean, Ezra Mongkolchaichana, Ezra Mongkolchaichana, Sinlapachai Senarat, Mark Tunmore

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This present preliminary study aimed to observe the butterfly species diversity in two selected subdistricts i.e., Mae Klong and Umphang of Umphang district, Tak province, northern Thailand, during May to September 2018. A survey method using sweep net was employed along line transects between 10.00-12.00 a.m. and 13.00-15.00 p.m. A total of 337 butterflies representing 37 species, 26 genera in five families were encountered. The family Nymphalidae held the highest species richness (15 species), followed by Papilionidae (9 species) and Pieridae (6 speices), respectively. Herein, four uncommon species, namely Junonia iphita iphita, Tanaecia julii odilina, Penthema darlisa melema, and Papilio alcmenor alcmenor, were discovered in this time. The Shannon diversity (H’) for all samples obtained from the pooled data set of this observation valued 2.563 with relatively high values of Evenness (J’= 0.710) and Simpson index and (D = 0.829). For similarity index (Ss), the assemblage recorded of butterfly species between Mae Klang-Umphang shared about 0.629, implying that the environmental conditions in both surveyed zones were alike. Additionally, the accumulation curve in both locations of the butterfly was still increasing gradually when the collection ended, indicating that the lepidopteran species would be raised if we continue to survey more in next month. Nevertheless, to gain more butterfly taxa, observing different plant communities covering every season and using several survey techniques should be considered for further investigation.

Keywords: butterfly, biodiversity, tak province, thailand

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Authors: Vikas Kumar, V. H. Saran, Arpit Mathur, Avik Kathuria

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The evaluation of biodynamic responses of the human body to whole body vibration exposure is necessary to quantify the exposure effects. A force plate model has been designed with the help of CAD software, which was investigated by performing the modal, stress and strain analysis using finite element approach in the software. The results of the modal, stress and strain analysis were under the limits for measurements of biodynamic responses to whole body vibration. The physical model of the force plate was manufactured and fixed to the vibration simulator and further used in the experimentation for the evaluation of apparent mass responses of the ten recruited subjects standing in an erect posture exposed to vertical whole body vibration. The platform was excited with sinusoidal vibration at vibration magnitude: 1.0 and 1.5 m/s2 rms at different frequency of 2, 3, 4, 5, 6, 8, 10, 12.5, 16 and 20 Hz. The results of magnitude of normalised apparent mass have shown the trend observed in the many past studies. The peak in the normalised apparent mass has been observed at 4 & 5 Hz frequency of vertical whole body vibration. The nonlinearity with respect to vibration magnitude has been also observed in the normalised apparent mass responses.

Keywords: whole body vibration, apparent mass, modeling, force plate

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Authors: Burdin Louise, Brulez Anne-Catherine, Mazurcyk Radoslaw, Leclercq Jean-louis, Benayoun Stéphane

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By using a biomimetic approach, an investigation was conducted to determine the connections between morphology and wetting. The interest is focused on the Morpho peleides butterfly. This butterfly is already well-known among researchers for its brilliant iridescent color and has inspired numerous innovations. The intricate structure of its wings is responsible for such color. However, this multiscale structure exhibits a multitude of other features, such as hydrophobicity. Given the limited research on the wetting properties of Morpho butterfly, a detailed analysis of its wetting behavior is proposed. Multiscale surface topographies of the Morpho peleides butterfly were analyzed using scanning electron microscope and atomic force microscopy. To understand the relationship between morphology and wettability, a goniometer was employed to measured static and dynamic contact angle. Since several studies have consistently demonstrated that superhydrophobic surfaces can effectively delay freezing, icing delay time the Morpho’s wings was also measured. The results revealed contact angles close to 136°, indicating a high degree of hydrophobicity. Moreover, sliding angles (SA) were measured in different directions, including along and against the rolling-outward direction. The findings suggest anisotropic wetting. Specifically, when the wing was tilted along the rolling outward direction (i.e., away from the insect’s body) SA was about 7°. While, when the wing was tilted against the rolling outward direction, SA was about 29°. This phenomenon is directly linked to the butterfly’s survival strategy. To investigate the exclusive morphological impact on anti-icing properties, PDMS replicas of the Morpho butterfly were obtained. When compared to flat PDMS and microscale textured PDMS, Morpho replications exhibited a longer freezing time. Therefore, this could be a source of inspiration for designing superhydrophobic surfaces with anti-icing applications or functional surfaces with controlled wettability.

Keywords: biomimetic, anisotropic wetting, anti-icing, multiscale roughness

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Authors: Yong-Taeg Lee, Jun-Ho Na, Seung-Hun Kim, Seong-Uk Hong

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Damages from noise and vibration are increasing every year, most of which are noises between floors in deteriorated building caused by floor impact sound. In this study, the concrete slab measured vibration impact sound for evaluation floor vibration of deteriorated buildings that fails to satisfy with the minimum thickness. In this experimental study, the vibration scale by impact sound was calibrated and compared with ISO and AIJ standard for vibration. The results show that vibration in slab with thickness used in existing building reach human perception levels.

Keywords: vibration, frequency, accelerometer, concrete slab

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Authors: A. Nabhan, Mohamed R. El-Sharkawy, A. Rashed

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The main aim of this paper is to dedicate the belt drive system faults like cogs missing, misalignment and belt worm using vibration analysis technique. Experimentally, the belt drive test-rig is equipped to measure vibrations signals under different operating conditions. Finite element 3D model of belt drive system is created and vibration response analyzed using commercial finite element software ABAQUS/CAE.  Root mean square (RMS) and Crest Factor will serve as indicators of average amplitude of envelope analysis signals. The vibration signals pattern obtained from the simulation model and experimental data have the same characteristics. It can be concluded that each case of the RMS is more effective in detecting the defect for acceleration response. While Crest Factor parameter has a response with the displacement and velocity of vibration signals. Also it can be noticed that the model has difficulty in completing the solution when the misalignment angle is higher than 1 degree.

Keywords: simulation model, misalignment, cogs missing, vibration analysis

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Authors: Sarakorn Sukaviriya

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This paper describes the inspection procedure, root cause analysis, the rectification of crack, and how to apply the procedure with other similar plants. During the operation of the steam turbine (620MW), instruments such as speed sensor of steam turbine, the servo valve of main stop valve and electrical wires were malfunction caused by leakage steam from main steam governing valve. Therefore, the power plant decided to shutdown steam turbines for figuring out the cause of leakage steam. Inspection techniques to be applied in this problem were microstructure testing (SEM), pipe stress analysis (FEM) and non-destructive testing. The crack was initially found on main governing valve’s weldment by visual inspection. To analyze more precisely, pipe stress analysis and microstructure testing were applied and results indicated that the crack was intergranular and originated from the weld defect. This weld defect caused the notch with high-stress concentration which created crack and then propagated to steam leakage. The major root cause of this problem was an inappropriate welding process, which created a weld defect. To repair this joint from damage, we used a welding technique by producing refinement of coarse grain HAZ and eliminating stress concentration. After the weldment was completely repaired, other adjacent weldments still had risk. Hence, to prevent any future cracks, non-destructive testing (NDT) shall be applied to all joints in order to ensure that there will be no indication of crack.

Keywords: steam-pipe leakage, steam leakage, weld crack analysis, weld defect

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Authors: Kouider Bendine, Zouaoui Satla, Boukhoulda Farouk Benallel, Shun-Qi Zhang

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Turbine blades are subjected to a variety of loads, lead to an undesirable vibration. Such vibration can cause serious damages or even lead to a total failure of the blade. The present paper addresses the vibration control of turbine blade. The study aims to propose a passive vibration control using piezoelectric material. the passive control is effectuated by shunting an RL circuit to the piezoelectric patch in a parallel configuration. To this end, a Finite element model for the blade with the piezoelectric patch is implemented in ANSYS APDL. The model is then subjected to a harmonic frequency-based analysis for the case of control on and off. The results show that the proposed methodology was able to reduce blade vibration by 18%.

Keywords: blade, active piezoelectric vibration control, finite element., shunt circuit

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Authors: Long Kim Vu, Ban Dang Nguyen

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In this paper, the finite element method (FEM) is utilized to simulate the comprehensive process including tightening, releasing and self-loosening of a bolt joint under transverse vibration. Following to the accurate geometry of helical threads, an absolutely hexahedral meshing is implemented. The accuracy of simulation process is verified and validated by comparison with the experimental results on clamping force-vibration relationship, which shows the sufficient correlation. Further analysis with different amplitude and frequency of transverse vibration is done to determine the dominant factor inducing the failure.

Keywords: bolt self-loosening, contact state, finite element method, FEM, helical thread modeling

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Authors: Mostafa Firoozabadi, Alireza Foroughi Nematollahi

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Semi autogenous mills are designed for grinding or primary crushed ore, and are the most widely used in concentrators globally. Any defect occurrence in semi autogenous mills can stop the production line. A Gearbox is a significant part of a rotating machine or a mill, so, the gearbox monitoring is a necessary process to prevent the unwanted defects. When a defect happens in a gearbox bearing, this defect can be transferred to the other parts of the equipment like inner ring, outer ring, balls, and the bearing cage. Vibration analysis is one of the most effective and common ways to detect the bearing defects in the mills. Vibration signal in a mill can be made by different parts of the mill including electromotor, pinion girth gear, different rolling bearings, and tire. When a vibration signal, made by the aforementioned parts, is added to the gearbox vibration spectrum, an accurate and on time defect detection in the gearbox will be difficult. In this paper, a new method is proposed to detect the gearbox bearing defects in the semi autogenous mill on time and accurately, using the vibration signal analysis method. In this method, if the vibration values are increased in the vibration curve, the probability of defect occurrence is investigated by comparing the equipment vibration values and the standard ones. Then, all vibration frequencies are extracted from the vibration signal and the equipment defect is detected using the vibration spectrum curve. This method is implemented on the semi autogenous mills in the Golgohar mining and industrial company in Iran. The results show that the proposed method can detect the bearing looseness on time and accurately. After defect detection, the bearing is opened before the equipment failure and the predictive maintenance actions are implemented on it.

Keywords: condition monitoring, gearbox defects, predictive maintenance, vibration analysis

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Authors: J. H. Kim, J. H. Kwon, J. S. Park, K. J. Lim

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This paper has investigated a technique that predicts the performance of a bar-type unimorph piezoelectric vibration actuator depending on the frequency. This paper has been proposed an equivalent circuit that can be easily analyzed for the bar-type unimorph piezoelectric vibration actuator. In the dynamic analysis, rigidity and resonance frequency, which are important mechanical elements, were derived using the basic beam theory. In the equivalent circuit analysis, the displacement and bandwidth of the piezoelectric vibration actuator depending on the frequency were predicted. Also, for the reliability of the derived equations, the predicted performance depending on the shape change was compared with the result of a finite element analysis program.

Keywords: actuator, piezoelectric, performance, unimorph

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Authors: Kavindan Balakrishnan

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Root cause Identification of the Vibration phenomenon in a feedwater pumping station was the main objective of this research. First, the mode shapes of the pumping structure were investigated using numerical and analytical methods. Then the flow pressure and streamline distribution in the pump sump were examined using C.F.D. simulation, which was hypothesized can be a cause of vibration in the pumping station. As the problem specification of this research states, the vibration phenomenon in the pumping station, with four parallel pumps operating at the same time and heavy vibration recorded even after several maintenance steps. They also specified that a relatively large amplitude of vibration exited by pumps 1 and 4 while others remain normal. As a result, the focus of this research was on determining the cause of such a mode of vibration in the pump station with the assistance of Finite Element Analysis tools and Analytical methods. Major outcomes were observed in structural behavior which is favorable to the vibration pattern phenomenon in the pumping structure as a result of this research. Behaviors of the numerical and analytical models of the pump structure have similar characteristics in their mode shapes, particularly in their 2nd mode shape, which is considerably related to the exact cause of the research problem statement. Since this study reveals several possible points of flow visualization in the pump sump model that can be a favorable cause of vibration in the system, there is more room for improved investigation on flow conditions relating to pump vibrations.

Keywords: vibration, simulation, analysis, Ansys, Matlab, mode shapes, pressure distribution, structure

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Authors: Gürkan Şakar, Fevzi Çakmak Bolat

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In this study free vibration analysis of aluminum honeycomb sandwich structures were carried out experimentally and numerically. The natural frequencies and mode shapes of sandwich structures fabricated with different configurations for clamped-free boundary condition were determined. The effects of lower and upper face sheet thickness, the core material thickness, cell diameter, cell angle and foil thickness on the vibration characteristics were examined. The numerical studies were performed with ANSYS package. While the sandwich structures were modeled in ANSYS the continuum model was used. Later, the numerical results were compared with the experimental findings.

Keywords: sandwich structure, free vibration, numeric analysis, 3D model, continuum model

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Authors: Agata Krawczyk-Ozog, Mateusz K. Holda, Mateusz Koziej, Danuta Sorysz, Zbigniew Siudak, Wieslawa Klimek-Piotrowska, Dariusz Dudek

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Introduction: Rapid development of the surgical and less-invasive percutaneous mitral valve repair procedures greatly increase the interest of the mitral valve anatomy. The aim of this study was to characterize morphological variability of the mitral valve leaflets and to provide the size of their particular parts. Materials and Methods: In the study, we included 200 autopsied human hearts from Caucasian individuals (25% females) with mean age 47.5 (±17.9) without any valvular diseases. The morphology of the mitral valve was evaluated. The intercommissural and aorto-mural diameters of the mitral annulus were measured. All leaflets and their scallops were identified. The base and the height of the posteromedial commissure (PM-C), anterolateral commissure (AL-C), anterior leaflet (AL) and posterior leaflet (PL) with their scallops were measured. Results: The intercommissural diameter was 28.0±4.8 mm, the aorto-mural diameter 19.7±4.8 mm, circumference of the mitral annulus 89.9±12.6 mm and the area of the mitral valve 485.4±171.4 mm2. Classical mitral valves (AL+AL-C+PL(P1,P2,P3)+PM-C) were found in 141 (70.5%) specimens. In classical type, the mean AL base and height were 30.8±4.9 mm and 20.6±4.2 mm, while mean PL base and height 45.1±8.2 mm 12.9±2.8 mm respectively. The mean ratio of the AL base to PL base was 0.7±0.2. Variations in PL were found in 55 (27.5%) and in AL in 5 (2.5%) hearts. The most common variations were: valve with one accessory scallop (AcS) between P3 and PM-C (7%); AcS between P1 and AL-C (4%); connections of P2 and P3 scallops (4%); connections of P1 and P2 scallops (3%); AcS in AL (2.5%). All AcS were smaller than the main PL scallops. The mean intertrigonal distance was 21.9±3.8 mm. Conclusions: In all cases, the mitral valve is built by two main leaflets with possible variants in secondary to leaflets scallops (29.5%). The variations are largely associated with PL and are mostly related to the presence of AcS. Anatomically the AL is not divided into scallops, and it occupies 34.5% of the mitral annulus circumference. Understanding the anatomy of the mitral valve leaflets helps to planning and performing mitral valve repair procedures.

Keywords: accessory scallop, commissure, connected scallops, human heart, mitral leaflets, mitral valve

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Authors: Ahmed Bensreti, Mohamed Gouarsha

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This paper presents a review of the pressure surge simulations carried out for Phase III of the Man Made River project in Libya with particular emphasis on the transient generated by simultaneous pump trips at Al Gardabiya Pump Station. The omission of the surge vessel check valve and bypass system on the grounds of cost, ease of design, and construction will result in, as expected, increased surge fluctuations as the damping effect in the form was removed. From the hydraulic and control requirements, it is recommended for Al Gardabiya Pump station that the check valve and check valve bypass be included in the final surge vessel design.

Keywords: computational fluid dynamics, surge vessel design, transient surge analysis, water pipe hydraulics

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Authors: Abraham J. Rizkalla, Tristan D. Yan

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Purpose: Durable mitral valve repair is preferred to a replacement, avoiding the need for anticoagulation or re-intervention, with a reduced risk of endocarditis. Robotic mitral repair has been gaining favour globally as a safe, effective, and reproducible method of minimally invasive valve repair. In this work, we showcase the use of the Davinci© Xi robotic platform to perform several advanced techniques, working synergistically to achieve successful mitral repair in advanced mitral disease. Techniques: We present the case of a Barlow type mitral valve disease with a tall and redundant posterior leaflet resulting in severe mitral regurgitation and systolic anterior motion. Firstly, quadrangular resection of P2 is performed to remove the excess and redundant leaflet. Secondly, a sliding leaflet plasty of P1 and P3 is used to reconstruct the posterior leaflet. To anchor the newly formed posterior leaflet to the papillary muscle, CV-4 Goretex neochordae are fashioned using the innovative string, ruler, and bulldog technique. Finally, mitral valve annuloplasty and closure of a patent foramen ovale complete the repair. Results: There was no significant residual mitral regurgitation and complete resolution of the systolic anterior motion of the mitral valve on post operative transoesophageal echocardiography. Conclusion: This work highlights the robotic approach to complex repair techniques for advanced mitral valve disease. Familiarity with resection and sliding plasty, neochord implantation, and annuloplasty allows the modern cardiac surgeon to achieve a minimally-invasive and durable mitral valve repair when faced with complex mitral valve pathology.

Keywords: robotic mitral valve repair, Barlow's valve, sliding plasty, neochord, annuloplasty, quadrangular resection

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Authors: Hyo Lim Kang, Tae An Kim, Seung Ho Han

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A 3-way reversing valve has been used in automotive washing machines to remove remaining oil and dirt on machined engine and transmission blocks. It provides rapid and accurate changes of water flow direction without any precise control device. However, due to its complicated bottom-plug shape, a cavitation occurs in a wide range of the bottom-plug in a downstream. In this study, the cavitation index and POC (percent of cavitation) were used to evaluate quantitatively the cavitation phenomena occurring at the bottom-plug. An optimal shape design was carried out via parametric study for geometries of the bottom-plug, in which a simple CAE-model was used in order to avoid time-consuming CFD analysis and hard to achieve convergence. To verify the results of numerical analysis, a flow visualization test was carried out using a test specimen with a transparent acryl pipe according to ISA-RP75.23. The flow characteristics such as the cavitation occurring in the downstream were investigated by using a flow test equipment with valve and pump including a flow control system and high-speed camera.

Keywords: cavitation, flow visualization test, optimal shape design, percent of cavitation, reversing valve

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Authors: Nesrine Gaaliche

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This study provides a finite element dynamic model for analyzing rolling bearing system vibration response. The vibration responses of polypropylene bearings with and without defects are studied using FE analysis and compared to experimental data. The viscoelastic behavior of thermoplastic is investigated in this work to evaluate the influence of material flexibility and damping viscosity. The vibrations are detected using 3D dynamic analysis. Peak vibrations are more noticeable in an inner ring defect than in an outer ring defect, according to test data. The performance of thermoplastic bearings is compared to that of metal parts using vibration signals. Both the test and numerical results show that Polypropylene bearings exhibit less vibration than steel counterparts. Unlike bearings made from metal, polypropylene bearings absorb vibrations and handle shaft misalignments. Following validation of the overall vibration spectrum data, Von Mises stresses inside the rings are assessed under high loads. Stress is significantly high under the balls, according to the simulation findings. For the test cases, the computational findings correspond closely to the experimental results.

Keywords: viscoelastic, FE analysis, polypropylene, bearings

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Authors: Po-Yuan Tung, Jen-Chueh Kuo, Chia-Ray Chen, Chien-Hsing Li, Kuo-Liang Pan

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The main-body structure of satellite is mainly constructed by lightweight material, it should be able to withstand certain vibration load during launches. Since various kinds of change possibility in the space, it is an extremely important work to study the random vibration response of satellite structure. This paper based on the reciprocity relationship between sound and structure response and it will try to evaluate the dynamic response of satellite main body under random acoustic load excitation. This paper will study the technical process and verify the feasibility of sonic-borne vibration analysis. One simple plate exposed to the uniform acoustic field is utilized to take some important parameters and to validate the acoustics field model of the reverberation chamber. Then import both structure and acoustic field chamber models into the vibro-acoustic coupling analysis software to predict the structure response. During the modeling process, experiment verification is performed to make sure the quality of numerical models. Finally, the surface vibration level can be calculated through the modal participation factor, and the analysis results are presented in PSD spectrum.

Keywords: vibration, acoustic, modal, honeycomb panel

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Authors: Su Yi Ming, Hou Ying, Zou Guang Ping

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Metal-net rubber is a new dry friction damping material, compared with the traditional metal rubber, which has high mechanization degree, and the mechanical performance of metal-net rubber is more stable. Through the sine sweep experiment and random vibration experiment of metal-net rubber vibration isolator, the influence of several important factors such as the lines slope, relative density and wire diameter on the transfer rate, natural frequency and root-mean-square response acceleration of metal-net rubber vibration isolation system, were studied through the method of control variables. Also, several relevant change curves under different vibration levels were derived, and the effects of vibration level on the natural frequency and root-mean-square response acceleration were analyzed through the curves.

Keywords: metal-net rubber vibration isolator, relative density, vibration level, wire diameter

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Authors: Mohd A. Azizan, Mohd Z. Zali

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It is well established that exposure to vibration has an adverse effect on human health, comfort, and performance. However, there is little quantitative knowledge on performance combined with drowsiness level during vibration exposure. This paper reports a study investigating the influence of vibration amplitude on seated occupant reaction time and drowsiness level. Eighteen male volunteers were recruited for this experiment. Before commencing the experiment, total transmitted acceleration measured at interfaces between the seat pan and seatback to human body was adjusted to become 0.2 ms-2 r.m.s and 0.4 ms-2 r.m.s for each volunteer. Seated volunteers were exposed to Gaussian random vibration with frequency band 1-15 Hz at two level of amplitude (low vibration amplitude and medium vibration amplitude) for 20-minutes in separate days. For the purpose of drowsiness measurement, volunteers were asked to complete 10-minutes PVT test before and after vibration exposure and rate their subjective drowsiness by giving score using Karolinska Sleepiness Scale (KSS) before vibration, every 5-minutes interval and following 20-minutes of vibration exposure. Strong evidence of drowsiness was found as there was a significant increase in reaction time and number of lapse following exposure to vibration in both conditions. However, the effect is more apparent in medium vibration amplitude. A steady increase of drowsiness level can also be observed in KSS in all volunteers. However, no significant differences were found in KSS between low vibration amplitude and medium vibration amplitude. It is concluded that exposure to vibration has an adverse effect on human alertness level and more pronounced at higher vibration amplitude. Taken together, these findings suggest a role of vibration in promoting drowsiness, especially at higher vibration amplitude.

Keywords: drowsiness, human vibration, karolinska sleepiness scale, psychomotor vigilance test

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Authors: Ramanen Sugunesegran, Michael L. Williams

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Over the past two decades surgical approaches for mitral valve (MV) disease have evolved with the advent of minimally invasive techniques. Robotic mitral valve repair (RMVr) safety and efficacy has been well documented, however, mid- to long-term data are limited. The aim of this review was to provide a comprehensive analysis of the available mid- to long-term term data for RMVr. Electronic searches of five databases were performed to identify all relevant studies reporting minimum 5-year data on RMVr. Pre-defined primary outcomes of interest were overall survival, freedom from MV reoperation and freedom from moderate or worse mitral regurgitation (MR) at 5-years or more post-RMVr. A meta-analysis of proportions or means was performed, utilizing a random effects model, to present the data. Kaplan-Meier curves were aggregated using reconstructed individual patient data. Nine studies totaling 3,300 patients undergoing RMVr were identified. Rates of overall survival at 1-, 5- and 10-years were 99.2%, 97.4% and 92.3%, respectively. Freedom from MV reoperation at 8-years post RMVr was 95.0%. Freedom from moderate or worse MR at 7-years was 86.0%. Rates of early post-operative complications were low with only 0.2% all-cause mortality and 1.0% cerebrovascular accident. Reoperation for bleeding was low at 2.2% and successful RMVr was 99.8%. Mean intensive care unit and hospital stay were 22.4 hours and 5.2 days, respectively. RMVr is a safe procedure with low rates of early mortality and other complications. It can be performed with low complication rates in high volume, experienced centers. Evaluation of available mid-term data post-RMVr suggests favorable rates of overall survival, freedom from MV reoperation and freedom from moderate or worse MR recurrence.

Keywords: mitral valve disease, mitral valve repair, robotic cardiac surgery, robotic mitral valve repair

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Authors: Mansour H. Alkmim, Adriano T. Fabro, Marcus V. G. De Morais

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In this paper, a global direct search optimization algorithm to reduce vibration of a tuned liquid column damper (TLCD), a class of passive structural control device, is presented. The objective is to find optimized parameters for the TLCD under stochastic load from different wind power spectral density. A verification is made considering the analytical solution of an undamped primary system under white noise excitation. Finally, a numerical example considering a simplified wind turbine model is given to illustrate the efficacy of the TLCD. Results from the random vibration analysis are shown for four types of random excitation wind model where the response PSDs obtained showed good vibration attenuation.

Keywords: generalized pattern search, parameter optimization, random vibration analysis, vibration suppression

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Authors: Mehdi Shekarzadeh, Pejman Taghipour Birgani

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In this paper, the effect of mass and height of tip on the flexural vibration modes of an atomic force microscope (AFM) rectangular cantilever is analyzed. A closed-form expression for the sensitivity of vibration modes is derived using the relationship between the resonant frequency and contact stiffness of cantilever and sample. Each mode has a different sensitivity to variations in surface stiffness. This sensitivity directly controls the image resolution. It is obtained an AFM cantilever is more sensitive when the mass of tip is lower and the first mode is the most sensitive mode. Also, the effect of changes of tip height on the flexural sensitivity is negligible.

Keywords: atomic force microscope, AFM, vibration analysis, flexural vibration, cantilever

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Authors: Marimuthu Gurusamy

Abstract:

In vibration analysis (with accelerometers) of rotating machines with rolling element bearing, the customers are interested to know the failure of the machine well in advance to plan the spare inventory and maintenance. But in real world most of the machines fails before the prediction of vibration analyst or Expert analysis software. Presently the prediction of failure is based on ISO 10816 vibration limits only. But this is not enough to monitor the failure of machines well in advance. Because more than 50% of the machines will fail even the vibration readings are within acceptable zone as per ISO 10816.Hence it requires further detail analysis and different techniques to predict the failure well in advance. In vibration Analysis, the velocity spectrum is used to analyse the root cause of the mechanical problems like unbalance, misalignment and looseness etc. The envelope spectrum are used to analyse the bearing frequency components, hence the failure in inner race, outer race and rolling elements are identified. But so far there is no correlation made between these two concepts. The author used both velocity spectrum and Envelope spectrum to analyse the machine behaviour and bearing condition to correlated the changes in dynamic load (by unbalance, misalignment and looseness etc.) and effect of impact on the bearing. Hence we could able to predict the expected life of the machine and bearings in the rotating equipment (with rolling element bearings). Also we used process parameters like temperature, flow and pressure to correlate with flow induced vibration and load variations, when abnormal vibration occurs due to changes in process parameters. Hence by correlation of velocity spectrum, envelope spectrum and process data with 20 years of experience in vibration analysis, the author could able to predict the rotating Equipment and its component’s deterioration and expected duration for maintenance.

Keywords: vibration analysis, velocity spectrum, envelope spectrum, prediction of deterioration

Procedia PDF Downloads 407

Authors: İkbal Eski

Abstract:

This investigation is researched on design of robust neural network predictors for analyzing vibration effects on moving parts of a drilling machine. Moreover, the research is divided two parts; first part is experimental investigation, second part is simulation analysis with neural networks. Therefore, a real time the drilling machine is used to vibrations during working conditions. The measured real vibration parameters are analyzed with proposed neural network. As results: Simulation approaches show that Radial Basis Neural Network has good performance to adapt real time parameters of the drilling machine.

Keywords: artificial neural network, vibration analyses, drilling machine, robust

Procedia PDF Downloads 356