Journal of Engineering and Thermal Sciences
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Experimental study on dynamic bending rigidity of aluminium cable steel reinforced
Get PDFThe dynamic bending rigidity of aluminium cable steel reinforced (ACSR) is a key parameter for analyzing the breeze vibration, galloping and de-icing vibration response of overhead transmission lines. In this paper, the calculation formula of the dynamic bending rigidity under axial force is derived based on the theory of Bernoulli-Euler beam. The dynamic response of one typical ACSR with different spans and different axial forces are studied by white-noise excitation and hammer excitation. The variation rules of dynamic bending rigidity of ACSR are presented. The comparison between the experimental results of the static and dynamic bending rigidity shows that the dynamic bending rigidity of the ACSR is much larger than the static bending rigidity
On the issue of the motion of balls in a double pendulum
Get PDFThe paper considers a model of a vertical double pendulum with one suspension centre moving in a vertical plane. For the proposed system of pendulums, differential equations of motion and conditions for the collision of balls are obtained. When modelling the movement of pendulums, the central impact of the balls was considered for various variants of the movement of the suspension point: the suspension point oscillates in the vertical direction; the suspension point makes rotational movements in the vertical plane. In this case, various conditions of the central impact between the balls were considered: absolutely inelastic impact; absolutely elastic impact; impact with the transformation of impact energy (elastic impact). Comparison of the results of the numerical simulation and the results of experiments with the Kapitza pendulum in published sources confirmed the possibility of modelling an elastic impact between balls in a double pendulum and between balls in an autobalancer with a horizontal axis of rotation of the rotor
Modal analysis of a milling dynamometer considered as 1DOF system
Get PDFA force transducer-based plate dynamometer for milling force measurements is presented in this paper. The main components of the designed dynamometer were described, and experimental modal analysis was carried out while considering the dynamometer as a 1DOF system. The values of the main components of the 1DOF systems such as mass, damping coefficient, and equivalent stiffness were identified, and the natural frequency for rings and dynamometer was calculated. The calculated natural frequencies of components were found in reacceptance FRF, obtained by modal analysis done with an impact hammer. A MATLAB simulation was done to validate the system using the transfer function based on the modal test
Recycling technology of old cement concrete pavement in highways
Get PDFThrough the practice of a highway pavement overhaul project, the feasibility of the old concrete pavement recycling scheme in terms of technology, economy and sustainable development is analyzed. The dynamic characteristics of concrete pavement were tested. The results show that crushing the old concrete panels into recycled aggregates and then re-use them not only eliminates the negative impact on the ecological environment caused by the land occupation of waste aggregates and needs to be disposed of, but also promotes the recycling of engineering waste and reduces the project cost. The pavement paved with recycled cement concrete can basically achieve the same dynamic performance as the pavement paved with conventional concrete
Modelling and experimental investigation of the vibratory conveyor operating conditions
Get PDFThe paper’s objective is to study the dynamic parameters and operating conditions of the vibratory conveyor, which is based on the double-mass oscillatory system and equipped with the pull-type (single-cycle) electromagnetic exciter. The scientific novelty consists in substantiating the conveying capacity of various standard sizes of bolts at different operating conditions defined by the input parameters, particularly supplied voltage. In order to describe the conveying tray vibrations, the simplified mathematical model of the conveyor’s double-mass oscillatory system is developed using the Euler-Lagrange equations and is numerically solved in the Mathematica software with the help of the Runge-Kutta methods. The experimental investigations are carried out at the Vibroengineering Laboratory of Lviv Polytechnic National University and are focused on testing the conveying speed of various bolts at different motion conditions: detachable (bouncing, hopping, jumping over the conveying surface) and non-detachable (sliding along the conveying surface). The obtained results show the basic kinematic parameters of the conveying tray motion at different voltages supplied to the actuating electromagnet and the dependencies of the conveying speeds of various bolts at different motion conditions mentioned above. The paper may be useful for designers and researchers while improving and implementing similar vibratory equipment in various industries
Shimmy analysis of light weight aircraft nose wheel landing gear
Get PDFThis paper presents mathematical modeling and analysis of shimmy oscillations for a light weight airplane single wheel nose landing gear. Shimmy is a self-excited oscillation which occurs usually on the nose wheel landing gear assembly during ground maneuvers which is governed by the dynamic characteristics of the landing gear and tires. Shimmy oscillation may lead to reduce the fatigue life of the landing gear and fuselage structure. So, the study of dynamic response and stability boundaries of landing gear plays crucial role while designing of airplanes. In earlier studies of vehicle shimmy only 3 degrees of freedom (DOF) considered such as torsional mode, lateral bending mode and tire lateral deformation. In this work along with above mentioned DOF, two more additional DOF introduced such as axial vibration of strut and tire in order to include the effect of vertical dynamics on shimmy model. Gyroscopic coupling effect also included in the model to study its influence on shimmy. Analysis carried out to determine critical velocity region for occurrence of shimmy and to investigate the effectiveness of ground unevenness on the landing gear system for two different runway conditions such as flat runway and random roughness runway. The results are more helpful to study significant interaction between the different parameters of landing gear and to represent stability boundaries
Evaluation of structural performance of steel-concrete joints in Hybrid Girder Bridges
Get PDFThe steel-concrete joint, serving as a transition zone between the steel and concrete girders, is the key component for transferring force among the hybrid girder systems. Despite the expected smooth transition of stiffness, high strength, easy fabrication, and verified static resistance, the structural performance of the steel-concrete joint under service loadings in a long-term period remains unclear. In this study, a FE model of a 1/2 steel-concrete joint from a real bridge is established to explore the long-term performance of the structure. Numerical results show that the minimal relative slip between the concrete infill and steel girder indicated the reliable capability of the steel-concrete joint, and the maximum concrete and steel stresses are 8.8 MPa and 192.8 MPa, respectively, which are far less than the material’s ultimate strength. The outcomes of this study can serve as a reference for analyzing the long-term performance of steel-concrete joints in hybrid girder bridges
Indoor and outdoor multi-source 3D data fusion method for ancient buildings
Get PDFAncient buildings carry important information, such as ancient politics, economy, culture, customs. However, with the course of time, ancient buildings are often damaged to different degrees, so the restoration of ancient buildings is of great importance from the historical point of view. There are three commonly used non-contact measurement methods, including UAV-based oblique photogrammetry, terrestrial laser scanning, and close-range photogrammetry. These methods can provide integrated three-dimensional surveys of open spaces, indoor and outdoor surfaces for ancient buildings. Theoretically, the combined use of the three measurement methods can provide 3D (three-dimensional) data support for the protection and repair of ancient buildings. However, data from the three methods need to be fused urgently, because if the image data is not used, it will lead to a lack of real and intuitive texture information, and if only image matching point clouds are used, their accuracy will be lower than that of terrestrial laser scanning point clouds, and it will also lead to a lack of digital expression for components with high indoor historical value of ancient buildings. Therefore, in this paper, a data fusion method is proposed to achieve multi-source and multi-scale 3D data fusion of indoor and outdoor surfaces. It takes the terrestrial laser point cloud as the core, and based on fine component texture features and building outline features, respectively, the ground close-range image matching point cloud and UAV oblique image matching point cloud are registered with the terrestrial laser point cloud. This method unifies the data from three measurements in the point cloud and realizes the high-precision fusion of these three data. Based on the indoor and outdoor 3D full-element point cloud formed by the proposed method, it will constitute a visual point cloud model in producing plans, elevations, sections, orthophotos, and other elements for the study of ancient buildings
Analysis and optimization of seismic performance of high-rise residential building
Get PDFIn order to improve the seismic performance of high-rise buildings, a friction damper installation scheme was proposed in the paper. Through numerical simulation and experimental testing, the vibration reduction effect was compared and verified. Herringbone structure was applied to install friction damper in the bearing wall. Based on this vibration reduction scheme, the finite element model of high-rise building was established, and the influence of damper on the modal characteristics of building frame was analyzed. It can be known that the damper has little influence on the natural frequency, but has a great influence on the amplitude range of the excitation response. In the finite element model, two kinds of seismic waves were applied, the strength and dynamic response was simulated and calculated, and the maximum deformation and stress results were obtained. Compared with the initial model, it can be known that the more intense the vibration is, the more obvious the damping effect of the damper is. A seismic excitation simulation system based on acceleration sensor detection is designed and applied to the wall vibration test. The results show that the maximum vibration acceleration of the measured point is reduced by 26.3 % by the damper, and the stable seismic effect can still be maintained during the impact of extension. Compared with the traditional hardness and volume reinforcement scheme, the friction damper can reduce the production cost and improve the adaptability to seismic wave excitation, which provides an important basis for seismic research in other fields
Skull base flexion and its influence on chewing
Get PDFSkull base asymmetries can occur in the intrauterine period, manifesting from birth as craniofacial asymmetries and should be investigated both in the maxilla and mandible and in the craniofacial region, as they are related to the base of the skull. The objective of this study was to explain that treatment using Craniofacial Biodynamics (CFBD) enables symmetrical craniofacial growth, being recommended from three to six years of age, when the processes of skull base remodeling cease. This study was based on exploratory bibliographic research, aiming at a better understanding of the concepts presented in this therapeutic approach, to verify the influence that such concepts exert on treatment through CFBD. It was evidenced in this research that these asymmetries may be corrected, or even minimized through the CFBD, which relates the ontogenetic development of the skull base with orofacial development