Journal of Engineering and Thermal Sciences
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Assessment of foot trajectories and ground reaction force in a trans-femoral amputee with Jaipur Knee and 3R20 knee joints
Get PDFIn developing countries like India, unilateral transfemoral amputees encounter with the challenge to select and evaluate the knee joint performance. This study aims to evaluate the response of knee joint on vertical ground reaction forces (vGRFs), walking speed, range of motion (ROM) of joints like hip, knee and ankle joints in first two weeks and enhanced response. Movements of different joints were recorded through VICON motion analysis system. Vertical ground reaction forces were captured through AMTI strain gauzed force plate. It has been observed that in two weeks normalized speed increases 0.41 to 0.49 with 3R20. Range of motion of joints was observed with interesting fact that in general with 3R20, joints angle their respective ROM were more than Jaipur Knee but in same cases in second half of gait cycle Jaipur Knee responded better than 3R20 knee joint
Simulation on metro railway induced vibration. Part I: effect of out-of-round wheels
Get PDFThis paper discussed the effect of out-of-round wheels on simulation of rail dynamic behavior in the frequency range for ground vibration and ground-borne noise. A train-track interaction model was built by software Simpack and Abaqus. The input roughness was measured from a worn wheel and was applied moving on perfect smooth rail surface in different train speeds. Simulation results indicated that out-of-round wheel would affect the calculation result that could not be neglected, as the affected frequency range would be lower enough to influence the ground vibration (1-80 Hz) and ground-borne noise (16-250 Hz)
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
Classification of diaphysis based on the mechanical response of femur bone
Get PDFThis work deal with the biomechanical analysis of the Captum Collum Diaphysis (CCD) femur bone. The femur is the largest bone in the upper leg. The angle between femur neck and femur shaft of the femora is a parameter in determining the CCD or FSA angle. 126 ° is the usual angle for a healthy adult and variation in this angle leads to the CCD. This angle in the femur bone helps in determining the knock knee and bow leggedness orthopaedic disease. This angle impacts on the distribution of stress and deflection in the femur bone during the daily activities. Computational Multi-Scale analysis has been done for homogenized properties of femur bone. A Numerical simulation has been made for the biomechanical analysis of CCD femur bone using Finite Element Method. There is significant impact of stress distribution and deflection over the femur bone in case of change in optimum CCD angle (coxa norma) and also leads to change the natural frequency of the bone. Predicted results shows the above mentioned disease behaviour over the healthy bone. The study of these deformity and their results are of clinical importance in musculoseketal behaviour of the human femur bone
Randomness complexity as a family feature of rolling bearings’ degradation
Get PDFRandomness complexity is a kind of features which is widely used to describe bearings’ degradation. However, different randomness complexities present different properties. It is necessary to figure out different randomness complexities’ properties. In this paper, we are going to make comparisons of seven commonly used randomness complexities namely approximate entropy, sample entropy, fuzzy entropy, Shannon entropy, permutation entropy, Lempel-Ziv complexity and C0 complexity by simulation signals with three different aspects and two run-to-failure bearing’s data. By comparisons, we have found that there are a kind of similarity between them and we have proposed a trend similarity index to expound this similarity. Based on the comparisons, we can infer that randomness complexities are a family feature of rolling bearings’ degradation. Among the seven discussed complexities, sample entropy has the best performance, and it can be a good representative of the complexity features. In this paper, the difference between complexity features and other features when monitoring bearings’ degradation have been discussed. The research will provide a reference for rolling bearings’ multi-features dimensionality reduction by attribute selection method
Numerical modelling of shear thickening fluid in nanosilica dispersion
Get PDFIn this paper, a numerical model of the shear thickening fluid (STF) is generated and the rheological properties are compared with the experimental data. Power Law model has been used to fit the rheological data for STF. Experimental data is taken from a performed study and a user defined function (UDF) has been written to develop the shear thickening behavior. The purpose of this study is to exactly model the behavior of shear thickening fluids by using UDF, to explain the shear-thickening mechanisms under different shear rates. Different parameters like viscosity, shear stress and velocity of the STF have also been reported
Effects of the wide-body suspension bridge auxiliary structure on flutter characteristics by CFD
Get PDFThis paper is focused on the CFD numerical simulation of flutter characteristics of the wide-body flat steel box girder of Chongqing Cuntan Yangtze Bridge. The specific influence on the aerodynamic performance and flutter critical wind velocity have been studied by setting different railing ventilation rates. The results show that: the subsidiary structures of the main beam have an adverse effect on the stability of bridge flutter. The ventilation rate of the railings affects the flutter derivatives and the critical wind speed of the flutter
Experimental determination on the critical angle of seismic incidence of curved bridge
Get PDFThe shaking table model test mainly focuses on the study of seismic response law, aseismic performance and seismic damping and isolation effect of bridges with a single or multi-platform shaking table. Basically, the plane principal axis direction is adopted for the seismic input of structural models. Little research effort considering multi-angle seismic input has been reported in the structural model test. In this paper we designed and conducted a small-scale shaking table model test to study the seismic response law of the curved girder bridges with seismic input at different angles, and provided experimental verification for the theoretical method of the most unfavorable angle of seismic input. The experimental results show that the variation trend of component response to variation of the seismic input direction is consistent with that of the numerical analysis, which indicates that the designed device is effective
Stability of stope structure under different mining methods
Get PDFThe ore body has a great influence on the stability of surrounding rock and mining safety under different mining modes, and the reasonable selection of mining mode depends on other characteristics, such as ore structure surface feature, rock mass mechanical property, and ground stress distribution. Given the insufficient mining research data, this study establishes a 3D model by using the FLAC3D calculation program. Through numerical simulation and other technical means, a preliminary study on plastic and minimum stress changes during horizontal pillar mining, stress changes under different mining modes, and the effect comparison of full filling mining modes is conducted. Results show that the surrounding rock at the corner of pillar 1 is damaged, the plastic zone decreases, and the minimum stress in each working procedure increases slightly. The area of the plastic zone in alternate mining is smaller to that in continuous mining. This study provides a theoretical basis for ore body mining
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