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Analysis of vibration based windmill coupled micromachined energy harvester
Get PDFThe present work exploits the centripetal, Coriolis and Euler forces generated in a rotating windmill. The MEMS device is placed on the blade of a windmill to harvest the energy. Modal analysis is carried out to optimize the dimensions of the structure to match the desired conditions. The real time response of the structure and the voltage generated in the piezoelectric layer are evaluated using transient analysis. It was noticed that Euler and Coriolis forces have a significant contribution in the initial time when the wind turbine accelerates from rest. The later portion is dominated by the Coriolis and Euler forces, and in some instances they cancel out each other. However, there is always a steady contribution from the centripetal force which is proportional to the magnitude of angular velocity of the wind turbine
Numerical analysis of temperature distribution in sliding contacts of pin on disc model
Get PDFPin on disc is a tribosystem confirming to ASTM G99, is employed in this work. It consists of deformable cylindrical disc and rigid pin with friction. Coating of Inconel 712 is added on stainless steel disc and pin is made of SiC3. The FEM software ANSYS R19.1 is employed for simulation of temperature distribution produced due to friction between pin on disc. Stress distribution is calculated from result produced between pin and disc interface due to applied contact load on pin. The governing equation is mentioned in introduction section. Result showing as contact load on pin increases maximum principle stress is increases. Temperature rises in direct proportion with sliding distance and time. Simulation result validates and confirmed with experimental results
Chaotic time series prediction using wavelet transform and multi-model hybrid method
Get PDFIn order to further improve the prediction accuracy of the chaotic time series and overcome the defects of the single model, a multi-model hybrid model of chaotic time series is proposed. First, the Discrete Wavelet Transform (DWT) is used to decompose the data and obtain the approximate coefficients (low-frequency sequence) and detailed coefficients (high-frequency sequence) of the sequence. Secondly, phase space reconstruction is performed on the decomposed data. Thirdly, the chaotic characteristics of each sequence are judged by correlation integral and Kolmogorov entropy. Fourthly, in order to explore the deeper features of the time series and improve the prediction accuracy, a sequence of Volterra adaptive prediction models is established for the components with chaotic characteristics according to the different characteristics of each component. For the components without chaotic characteristics, a JGPC prediction model without chaotic feature sequences is established. Finally, the multi-model fusion prediction of the above multiple sequences is carried out by the LSTM algorithm, and the final prediction result is obtained through calculation, which further improves the prediction accuracy. Experiments show that the multi-model hybrid method of Volterra-JGPC-LSTM is more accurate than other comparable models in predicting chaotic time series
Dynamic analysis of towing operation with military tracked recovery vehicle
Get PDFThe present work is focused upon development of multi-body dynamic (MBD) models of a military tracked recovery and towed vehicles in Adams Tracked Vehicle (ATV) toolkit, and carrying out the dynamic analysis of towing operation with the vehicles. Towing is one of the important recovery operations for the military recovery vehicle, which is generally carried out on plain terrain conditions. However, it is also desired to tow another vehicle of similar weight class over certain gradients as well. In this regard, it is required to assess the structural rigidity of the tow bar assembly, while negotiating the gradients. The finite element models of the tow bars have been developed in Abaqus/CAE, from which the modal information is extracted. The finite element models of the tow bars have been integrated with the MBD model of the recovery and towed vehicles in ATV through Adams/Flex. The dynamic analyses of towing operation with the existing tow bar assembly, have been carried out over different gradients, based on which required design modifications have been proposed to minimize the relative angular motion between the tow bars while descending the gradient. With an objective of further weight reduction and enhanced gradient climbing capability, suitable recommendations have further been provided to modify the tow bar assembly design. Dynamic simulations were carried out with the modified tow bar assembly design, through which higher gradients could be negotiated with reduced tow bar assembly weight. The above dynamic analyses have provided a base platform for arriving at the standard operating procedure of carrying out the towing operation in practice. The analyses have also established a framework for future design of tow bar assemblies under the influence of a three dimensional vehicle dynamic environment
Dynamic analysis of slider-crank mechanism with clearance fault
Get PDFIn this paper, the dynamic behavior of the slider-crank mechanism with clearance fault is investigated. The revolute joint with clearance is equivalent to a virtual massless rod, and then the dynamic equation of the crank slider mechanism with clearance is established by the Lagrangian method. In addition, a three-dimensional dynamic model of the crank slider mechanism with clearance is also established by ADAMS. The numerical results show that the clearance affects the displacement and velocity response of the crank-slider mechanism in a weak way, but influences the acceleration response of the mechanism in a significant manner. Due to the existence of the clearance, the revolute joint of the mechanism produces a rub-impact phenomenon, and the larger the clearance, the greater the impact strength. During the rub-impact process, there are three kinds of motion states of separation, collision and contact occur
Sound radiation of simply supported rectangular plate using finite element method
Get PDFIn this paper sound radiation of simply supported rectangular plate has been reported. The novelty in this research paper is a new method is prescribed for sound radiation calculation. The phenomenon of uncoupled structural acoustics have been followed such that structure is the critical part in structural vibration using modal analysis and harmonic response calculation for frequency range of interest 0 to 200 Hz, but in harmonic acoustic analysis the structure does not takes part in physics point of view but is used for only for transferring the normal velocity from wetted surface of the structure to the interface acoustic medium i.e. air. Sound Radiation parameters like Sound Pressure Level, Sound Power Level and Sound Radiation efficiency has been reported. Upon comparing the results with that from I. Zaman’s literature, it is found that the results are quite varying due to the fact the speed of sound in air as taken in literature is unjustified. So true simulation using correct data has been carried out in this paper and sound radiation results has been reported for frequency range of interest 0 to 200 Hz. It is found that the maximum sound pressure level is 72 dB and maximum sound power level is 78 dB which is suitable for noiseless environment
Qualitative assessment of the Upper limb of child with cerebral palsy
Get PDFThe management of the upper limb (MS) of the child with cerebral palsy (CP) is long past that of walking; many factors make it difficult to study the MS of the child PC: The variability of involvement (spasticity, dystonia) with, unlike the lower limb, the significant impact of associated disorders (sensory, cognitive) for functional use of the upper limb. The great diversity of tasks performed by the upper limb in contrast to the lower limb (cyclic activity of walking) which requires many assessment tools with standardized and age-appropriate tasks, for the multiple treatment goals. But for over fifteen years, with the advancement of research on brain plasticity, the development of new tools and access to certain therapeutics this care has taken a more important place and especially much earlier in the arsenal therapeutic. So we must emphasize the importance of choosing valuable tools for evaluation. .car if the used tests are not relevant, the relevance of the therapeutic action that will follow becomes her also questionable, Moreover, this means also that the therapist has some knowledge of possible therapeutics in order to able to inform his patient and refer him to appropriate stakeholders
Fine-grained fault recognition method for shaft orbit of rotary machine based on convolutional neural network
Get PDFIn the fault diagnosis of the shaft orbit of rotating machinery, there are few prejudgments about the severity of the faults, which is very important for fault repair. Therefore, a fine-grained recognition method is proposed to detect different severity faults by shaft orbit. Since different shaft orbits represent different type and different severity of faults, the convolutional neural network (CNN) is applied for identifying the shaft orbits to recognize the type and severity of the fault. The recognition rate of proposed fine-grained fault identification method is 97.96 % on the simulated shaft orbit database, and it takes only 0.31 milliseconds for the recognition of single sample. Experimental result indicated that the classification performance of the proposed method are better than the traditional machine learning models. Moreover, the method is applied for the identification of the measured shaft orbits of rotor with different degree of imbalance faults, and the testing accuracy of the experiments in measured shaft orbits is 97.14 %, which has verified the effectiveness of the proposed fine-grained fault recognition method
Influence of ultrasonic vibration on discrete media filled tubes during forward extrusion
Get PDFThe coupled deformation of composite structures of discrete media filled thin-walled tubes under the action of forces is a complicate mechanical process, especially when it is superimposed with external vibration. A Jenike shear cell connected with an ultrasonic exciting system was used to test the friction angles of the aggregations of ferric powder and steel ball under quasi-static and high frequency vibration conditions; then forward extrusion of Al6061 tubes filled with these discrete materials under different conditions were examined by experiment and numerical simulation. The results showed that the friction angles of both the discrete materials decreased under vibration, and those of the powders were reduced more, indicating that the “surface effect” of vibration on the particles with smaller granularity is more obvious. Under the combining action of “volume” and “surface” effects of vibration, the extrusion loads of the structures significantly decrease with the superposition of vibration, meanwhile the loads of the tubes filled with powders reduced more. With the imposed vibration, the density of fillers after forming are higher and the tube wall thickness distribution is more uniform
Damage detection in concrete gravity dams using signal processing algorithms based on earthquake vibrations
Get PDFIn structural engineering, damage detection in concrete gravity dams (CGDS) is a practical problem. Dam destruction can have severe financial consequences and may even lead to fatalities. Therefore, structural health monitoring in advance is crucial. In this regard, a well-known CGD, namely the Pine Flat Dam, has been chosen for the Finite Element Modeling. In this paper, damage is induced in the dam neck through elasticity modulus reduction by 40 % and 80 %. In addition, after applying Northridge earthquake, the acceleration in structure nodes for intact and damaged cases are recorded in vector formats. Using various methods, such as Discrete-time Fourier Transform (DTFT), Wavelet transform and Wiener transform, the differences between these two signals are investigated. The standard deviation (S.D.) of variations is chosen as the performance metric and is applied to the signal amplitude between intact and damage observations/signals. The reason why several signal processing algorithms are used is finding an approach which shows more clearly the differences caused by the destruction. This is evaluated via S.D. values for different algorithms. The results confirm the superiority of DTFT over other given algorithms. DTFT has a negligible outperformance (approximately zero dB) with respect to the Wavelet transform in both the crest and the lower nodes of the dam. This rate for DTFT and Wavelet is 10dB higher than that of Wiener and 35 dB in comparison with the simple amplitude difference. Moreover, the detection thresholds for the given methods are compared, and it is verified that the DTFT and Wavelet indicate the best performance