Journal of Engineering and Thermal Sciences
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The multivariable finite elements based on B-spline wavelet on the interval for 1D structural mechanics
Get PDFWavelet finite elements with two kinds of variables for 1D structural mechanics are constructed based on B-spline wavelet on the interval (BSWI) and the generalized variational principle. In contrast to the traditional method, the BSWI element with two kinds of variables (TBSWI) can improve the solution accuracy of the generalized stress apparently, because generalized displacement and stress are interpolated separately. Another superiority of the elements constructed is the interpolating function BSWI, which has very good approximation property, further guarantees solution accuracy. Euler beam, Timoshenko beam and Elastic foundation beam are studied providing several numerical examples to verify the efficiency
Experimental studies of stabilization of boring cutter form – building top oscillation
Get PDFThe article deals with application of automatic control of cutting tool oscillations, which permits to control the cross-sectional form of a hole. This parameter can be controlled in mass-produced machine tools only through machine tool geometrical relationship, which is ensured during manufacturing of metal cutting machine tools. The purpose of the proposed control system is to increase technological capabilities of the equipment in order to improve boring accuracy as compared with the accuracy regulated by the standards for this type of equipment. Testing of the proposed technological equipment demonstrated high efficiency of damping in the process of boring in terms of response to mechanical and impact actions. Rational combinations of cutting modes were revealed, which provide the needed accuracy and acceptable productivity in the hole cutting process
Influence of concave groove on transmission of blasting vibration wave
Get PDFWith the extensive application of blasting techniques, the prediction and hazard control of explosion-induced vibration is an important issue which cannot be ignored in blasting engineering. A numerical approach is presented to study the explosion-induced pressure load on the surface of C-4 explosives in a semi-infinite space, in order to explore the effectiveness of concave grooves in ground vibration wave barrier. Numerical simulations are carried out by using a widely applied explicit dynamic nonlinear finite element software LS-DYNA and adopted the Arbitrary Lagrangian-Eulerian method for numerical analysis to simulate the propagation of blast waves. The analysis shows that the concave grooves have a significant effect on attenuating the propagation of detonation waves. The vibration control is related to the width and depth of the groove, and the impact of the depth is greater than that of the width. This study can be used as a reference in hazard control of explosion-induced vibration
Novel attitude control devices for CubeSat satellites
Get PDFIn recent years a very modern trend of space exploration activities – constructing, launching and operating nano-satellites, became very popular. One of the main problems in implementation and control of nano-satellite is ensuring accurate yet simple and small-sized attitude control equipment. Most of the equipment implemented for that task in the past was large, bulky and could be hardly used on extremely small CubeSat standard nano-satellites. The equipment under development for attitude control of the satellites is described in this paper. The equipment relies on implementation of piezoelectric transducers for rotation of spherical body – reaction sphere, thus ensuring precise three-axis attitude control of the satellite by means of single device. Description of the device under development with some calculations and examples of implementation of such instrumentation is further described in the paper
Study of wave barriers design for the mitigation of railway ground vibrations
Get PDFNowadays, the consolidation of the rail in highly populated areas has become a reality. Foundations, buildings, high accuracy devices and people are susceptible to suffer from vibrations induced by passing trains. Therefore, models for predicting ground vibrations are required in order to determine new mitigation measures. Rectangular open or in-filled trenches are a suitable solution to be used near constructed railway lines. Their installation is fast, easy and economic since no intrusion in the track is needed. In this work, the influence of the trench design on its effectiveness is analyzed considering a train moving with subsonic speed. A finite element model of the track has been developed and validated with real data registered along the tram network in Alicante (Spain). The analysis is carried out in the time domain considering the quasi-static movement of the vehicles. The results demonstrate that, in ascending order, the most relevant parameters in a trench are its width, depth and in-filled material or trench typology. However, it is also concluded that other conditions such as the stratification of soil are essential in order to determine an optimal design of a wave barrier
Research of lateral vibrations of a passenger wagon running along the curved path
Get PDFThe objective of this work is to study transverse vibration of a passenger car body running at various speeds over the track irregularities, which are usually encountered in practice. The tasks that are addressed in this research work: perform tests at track irregularities of symmetrical sinusoidal shape running both along straight and curved paths, as well as driving over the junctions along the straight and curved paths, and compare the results
A new method for building risk level estimation under dynamic load
Get PDFA building, as mechanical system, is composed of elements with different properties and distinctions. Vibration or shock impact action is one of the most effective methods to produce substantial qualitative and quantitative changes in such system. Buildings may be conditionally divided into three main categories: residential, public or social and manufacturing or industrial buildings. Any building during interaction with the dynamic load could pose hazard to human safety in the crowded place, particularly in the case of accidental progressive collapse. This phenomenon is a relatively rare event but study of its behavior is very important both for newly erected and existing buildings in order to reduce the number of casualties in accidents. In general, civil engineering structures such as buildings are composed of elements with different properties. Interaction between these elements subjected to shock loading can be analyzed using „missing column” or „missing slab (beam)” scenarios. It is obvious that the most dangerous buildings are those with massive gathering of people, i.e. leisure, entertainment, shopping centers, high-volume administrative or industrial buildings, residential buildings, buildings of national significance, etc. Our goal is to propose a method to assess each building on a comprehensive hazard risk level under the influence of special effects, especially when the building experiences impact loading. The result would be a given expression of building index which is called a point of risk level D. The use of this point summon up additional assumptions for the assessment of building as integral building system, the consequences of accidents, as well as their prevention
Piecewise exact solution of nonlinear momentum conservation equation with unconditional stability for time increment
Get PDFExact solution is adopted for computation of the inviscid Burgers equation on finite difference grid. Initial condition and following computed values of the independent variable are assumed to be piecewisely linear between fixed grid points, and local exact solution is used to find the value at the next time step at each grid point. Comparisons of Piecewise Exact Solution Method (PESM), existing upwind scheme, and the analytic solution show that the present method is more accurate than the upwind scheme. The unconditional stability is a strong merit of this method and is shown with a test result
Nonlinear vibration of rectangular plate under the parametric excitation
Get PDFIn this paper, the dynamic behavior of rectangular plate under the in-plane load is studied. The partial differential equation based on the mechanical model is established, which will be deduced into two ordinary differential equations by use of Galerkin method. The existence of 1/2 harmonic solutions of the dynamical system applying the harmonic balance method is analyzed. The amplitude-frequency relationship is found, and the stability of solutions is investigated. The stable zone of dynamical system is determined
Research on the performance of buffer for landing gear based on the drop test
Get PDFBased on the drop test of the articulated main landing gear of Seagull 300 light multifunctional amphibious airplane, a further study has been conducted to establish buffer performance under different air chamber pressures and attitude angles. Through comparative analysis of the test results, the influencing rule of air chamber pressure and attitude angle on the buffer performance parameters (system capacity, vertical load, buffer compression, system efficiency and buffer efficiency) was obtained. The results demonstrate that air chamber pressure has a significant effect on the buffer system efficiency, while the attitude angle influences the system capacity a lot. With air chamber pressure increasing system efficiency decreases first, then gradually increases after reaching its minimum at 2.15 MPa and decreases at last after reaching its maximum at 2.7 MPa. Buffer efficiency decreases first and then increases after reaching its minimum at 2.2 MPa. When the attitude angle is between 3 and 12 degrees, the smaller the attitude angle, the more energy the system absorbs and the better the buffer performance is. The rate of change of performance parameters varies linearly with attitude angle. With the increase of angle, system capacity, maximum vertical load and system efficiency increase, and the change rate of buffer compression decreases correspondingly. The rate of change of system efficiency has the fastest growth