Cantilever Support Research Articles

Механическое взаимодействие метаемого тела со стенками канала рельсового электромагнитного ускорителя. Численное решение

The vibration of the accelerator rails under the action of electromagnetic forces, the right boundary of which is moving along with the armature along the barrel bore, is considered. The rail accelerator is simply considered as a Bernoulli-Euler beam of finite length, lying on a viscoelastic foundation, with cantilever support from the side of the accelerator breech. The rail vibration is described by a differential equation in partial derivatives of the fourth order in coordinate and the second order in time. The equation is solved numerically by combined method: finite differences in time and finite elements in coordinate. A comparison of the results of numerical calculations with an analytical solution showed that the developed code evaluates the behavior of the rail well under the influence of an EM load moving along its length along the entire trajectory of the accelerated body. Using the developed code, the influence of the current profile in the accelerator circuit and the foundation parameters on the dynamics of bending waves arising and propagating in the rail, the position and magnitude of the maximum rail deflection was studied. It is shown that it is possible to select a current profile that minimizes the rail accelerator deflection during acceleration. It is also found that the choice of the optimal current profile has no less effect on the maximum rail deflection than improving the parameters of the accelerator foundation. The calculation results may be useful in the design of an electromagnetic rail accelerator.

Study of parametric interaction during fused filament fabrication (FFF) using interpretive structural modelling (ISM) followed by experimental analysis

PurposeFused filament fabrication (FFF) is a type of additive manufacturing (AM) based on materials extrusion. It is the most widely practiced AM route, especially used for polymer-based rapid prototyping and customized product fabrication in relation to aerospace, automotive, architecture, consumer goods and medical applications. During FFF, part quality (surface finish, dimensional accuracy and static mechanical strength) is greatly influenced by several process parameters. The paper aims to study FFF parametric influence on aforesaid part quality aspects. In addition, dynamic analysis of the FFF part is carried out.Design/methodology/approachInterpretive structural modelling is attempted to articulate interrelationships that exist amongst FFF parameters. Next, a few specimens are fabricated using acrylonitrile butadiene styrene plastic at varied build orientation and build style. Effects of build orientation and build style on part’s ultimate tensile strength, flexure strength along with width build time are studied. Prototype beams (of different thickness) are fabricated by varying build style. Instrumental impact hammer Modal analysis is performed on the cantilever beams (cantilever support) to obtain the natural frequencies (first mode). Parametric influence on natural frequencies is also studied.FindingsStatic mechanical properties (tensile and flexure strength) are greatly influenced by build style and build orientation. Natural frequency (NF) of prototype beams is highly influenced by the build style and beam thickness.Originality/valueFFF built parts when subjected to application, may have to face a variety of external dynamic loads. If frequency of induced vibration (due to external force) matches with NF of the component part, resonance is incurred. To avoid occurrence of resonance, operational frequency (frequency of externally applied forces) must be lower/ higher than the NF. Because NF depends on mass and stiffness, and boundary conditions, FFF parts produced through varying build style may definitely correspond to varied NF. This aspect is explained in this work.

ASSESSMENT OF FIRE RESISTANCE CHARACTERISTICS AND THEORETICAL MODELING AND NUMERICAL INVESTIGATION OF EFFECT OF LOAD ON CANTILEVER AND RIGIDLY FIXED NATURAL FIBER REINFORCED GREEN COMPOSITE

The current study is ambitious to develop a hybrid composite specimen for evaluating fire resistance characteristics and performing model analysis for validating theoretical and numerical frequencies under cantilever and rigidly fixed support conditions. The composite test specimens are developed using hemp and banana fibers by applying the traditional hand layup fabrication technique. The focus on the use of various natural fibers is very rapid in both domestic and industrial applications. Natural fibers are handy in availability and are possesses extremely good mechanical, chemical and thermal properties. This work is focused on developing the composite specimen according to ASTM –D2863-87, for evaluating fire resistance characteristics. This work also includes theoretical and numerical validation of natural frequency under cantilever and rigidly fixed conditions. The finite Element Analysis (FEM) tool is used to validate the theoretical frequency. Through the statistical analysis, it is concluded that the developed composite specimen showcases good fire resisting property up to a temperature of 175o c with a good fire propagation time of 6minutes. It also exhibits excellent bonding strength up to a temperature of 95o c. It was found that the natural frequency calculated numerically using Roark’s formula closely satisfied with the values of theoretically obtained frequency from the Finite Element Method (FEM). The maximum natural frequency developed under cantilever support is 421.04Hz and 626.82Hz for fixed support conditions.

Механическое взаимодействие метаемого тела со стенками канала рельсового электромагнитного ускорителя. Тестовая задача

The vibration of the accelerator rails under the action of electromagnetic forces is considered. The armature and with it the right boundary of electromagnetic forces application moves along the barrel bore from the breach to muzzle. The rail accelerator is simply considered as a Bernoulli-Euler beam of finite length, lying on a viscoelastic foundation, with cantilever support from the side of the accelerator breech. The rail vibration is described by a differential equation in partial derivatives of the fourth order in coordinate and the second order in time. Using the eigenmode expansion method an analytical solution of the equation is obtained taking into account the change in the armature speed along the length of the barrel. Taking into account the peculiarities of the expression for natural vibration modes for this problem made it possible to simplify the calculations and take into account appropriate number of harmonics along the entire trajectory of the armature, which is difficult in the traditional application of the method, and thereby increase the accuracy of predicting the amplitude and nature of rail vibrations during the shot. The proposed approach allows testing and debugging numerical methods for solving complex problems, as well as more correctly designing the barrel of a rail accelerator.

Computational Study of Excitation Controlling Parameters Effect on Uniform Beam Deformation under Vibration

Understanding a structure’s behavior is necessary for most applications, especially excitation in ultrasonic applications. Currently, ultrasonic devices are used in various fields and have an essential role in nondestructive testing (NDT). The structure’s behavior must be concerned with achieving the best practice. The structural vibrational behavior depends on natural frequency and mode shape. This study attempted to determine the effect of influence parameters on shape deformation for designing the adequate excitation condition. In this study, the influence parameters of a uniform beam, including geometry, support condition, and material, were included to investigate their effect on the frequency, mode shape, and structural response. The result showed the significant influence of a structure’s length and support condition on the mode frequency, dramatically decreasing mode frequency for extended installation and cantilever support. This study investigated the three common mode shapes revealed that the longitudinal bending shape dominated due to the loading direction. Therefore, the shape deformation of the structure is mainly governed by the external excitation source, and the high structural response is received by applying the excitation near the antinode position of the vibration. Nevertheless, the computational result showed a good agreement with the analytical validation with less than 1 % error. The study leads to understanding the vibration, which can be further used for either the effective sensor attachment or designing the vibration control of ultrasonic applications.

Numerical modeling of natural vibrations of coaxial shells partially filled with fluid, taking into account the effects on the free surface

This work is devoted to the numerical analysis of vertical elastic coaxial cylindrical shells completely or partially filled with a quiescent compressible fluid with account for sloshing of its free surface. The problem is solved in the axisymmetric formulation using a semi-analytical version of the finite element method. The fluid medium is described by the wave equation, which together with the conditions prescribed at its boundaries is reduced to the weak form by the Bubnov - Galerkin method. A mathematical formulation of the dynamic problem for thin-walled structures is developed using the variational principle of virtual displacements and linear theory of thin shells based on Kirchhoff - Love hypotheses. The fluid pressure on the walls of the structure is calculated according to Bernoulli's equation. Sloshing modes caused by gravitational effects on free surface of liquid medium are excluded from the resulting system of equations through the use of the iteration dynamic condensation method. The numerical model has been verified by comparing it with the known data for the case of a single shell partially filled with fluid. The influence of the fluid level on the lowest natural frequencies of the system vibrations at different variants of kinematic boundary conditions for shells (rigid clamping at both edges, cantilever support) and different widths of the annular gap between them has been evaluated. It has been found that for the examined configurations, the level of the fluid in the annular channel has a stronger influence on the frequency spectrum compared to the level of fluid in the cavity of the inner shell due to the fact that vibration frequencies change in a wider range.

In-situ monitoring and modelling of distortion in multi-layer laser cladding of Stellite 6: Parametric and numerical approach

Laser cladding is a direct metal deposition technique used for repair and rebuilding of worn-out components. In this process, the component is subjected to high heating and cooling cycles, which generate residual stresses and distortion affecting the part quality. The present work is to investigate and evaluate distortions generated during deposition using in-situ measuring method and also with numerical modelling. The role of different support conditions (simply, cantilever, and fixed) and process parameters (laser power, scan speed) on distortion are examined. A numerical model in COMSOL Multiphysics software was developed to generate thermal history and distortion in multi-layer cladding of Stellite 6. The temperature data shows large thermal gradients development along the thickness; allowing material to expand and contract at different rates, leading to substrate distortion. This was evidence in laser displacement sensor data and simulation. The results showed simple and fixed supports develop 40 - 50% and 60 - 70% less distortion than cantilever. Additionally, when the scan speed is decreased from 20 mm/s to 12 mm/s, distortion is lowered by 15 - 40%. An increase in laser power from 2400 W to 3400 W showed distortions to be 30 - 60% higher; while the second layer depositions have given 15 - 25% lower deflection. The simulation results are in good agreement with experimental values and reveals that support conditions are significant on distortion. Conclusion:- Laser cladding with simple and fixed supports developed 40 % - 50 % and 60 % - 70 % lower distortions than cantilever support; and increases with increase in laser power and decrease in scan speed.

High mechanical Q-factor measurement of Si using a 3D cantilever support.

Thermal noise in test mass substrates and coatings is a significant noise contribution in the detection band of current and proposed future gravitational wave detectors. Substrate thermal noise can be reduced by using high mechanical Q-factor materials and cooling the test mass mirrors. Silicon is a promising potential candidate for the next generation detector test masses. The low thermal expansion and high thermal conductivity of silicon allow efficient cryogenic operation, and a significant increase in the amount of optical power that can be used in the detectors by decreasing thermal deformation and aberration. Mechanical stress, damage, poor surface quality or contamination can result in increased loss and thermal noise. Therefore, the characterization of mechanical loss in silicon test masses is necessary. In this project, we developed a technique to measure high Q-factor mechanical modes. We used finite element modeling to optimize the design of the test mass support structure to minimize the loss coupling from the support structure over a wide frequency range. Mechanical Q-factors of the order of 107 were achieved for several modes of a 10cm diam. × 3cm cylindrical silicon test mass with such a support at room temperature.

Construction Technology of Cantilever Support for Continuous Rigid Frame Side Span Cast-in-place Section

Construction Technology of Cantilever Support for Continuous Rigid Frame Side Span Cast-in-place Section

A new type of auxiliary structure for tunnel-surrounding rock support – composite cantilever support structure

Abstract. The deformation and damage mechanisms of tunnel-surrounding rock masses have always been a major problem in underground engineering, and studying these mechanisms plays an important role in preventing this kind of geological disaster. Against the background of the above project, in this paper, we propose a new type of support structure: a composite cantilever support structure. Studies involving the numerical calculation and application of this support structure are carried out, and the conducted investigation indicates that (1) for a relatively broken rock mass, the composite cantilever support structure can effectively restrain the deformation of the tunnel-surrounding rock mass, (2) through numerical calculation, the appropriate design parameters of the support structure are obtained, and (3) the design parameters and design structure of the composite cantilever support structure must be further studied and verified under complex geological conditions by engineering.

Analysis of the Innovative Channel Strut Concept Manufactured by Roll-Forming.

Due to the wide use of channel strut components, manufacturing is implemented in many industrial plants. Standard technology of profiles is based on welding of two parts of the profile and requires the regalvanizing of the joint zone causes. Thus, the production is challenging to automate on a single line. The main idea of the article is to present a concept of a channel strut, a cold-formed continuous metal component with an open or closed profile section. It would serve as a cantilever support instead of a standard solution. In the article, a unique lock system combination is proposed and analyzed both numerically and experimentally to provide steadiness of the strut without welding or other joining techniques. Two main lock shapes—semicircular and triangle—were proposed with some variations in the cutting plane. Analyses were carried out for three main profile cross-sections with different dimensions, based on the current industrial applications. The semicircular type of the lock was found to be the most stable, giving optimal strength to the strut under assumed loading, comparable to traditional solutions. The commercial FEM software MSC Marc was used for the numerical analysis.

Mechanical Analysis of Auxiliary Crank Mechanism for Orbiting Motion of Scroll Compressors

In most scroll compressors, the Oldham ring is often used to realize the orbiting motion, which causes a vibration problem due to its reciprocating motion at higher speed operation. In order to solve the vibration problem, the auxiliary crank mechanism may be introduced for the orbiting motion, thus realizing the perfect balance operation of the scroll compressors. Furthermore, the auxiliary crank system can reinforce the weakness in strength of the cantilever support mechanism of the main crankshaft. First, this study examines the number of the auxiliary crank, necessary for realizing the smooth orbital motion, and subsequently presents the fundamental analyses of auxiliary mechanism for the constraint forces on the auxiliary cranks, due to the compressed-gas moment, the frictional moments on the turning pairs and the balancing in moment due to the centrifugal loads. The final target of the present study is to develop a prototype of superlarge scroll compressor with the cooling capacity over 350kW, realizing the perfect balance operation and reinforcing the weakness in strength of the cantilever support mechanism of the main crankshaft.

Free in-plane vibration of plates with arbitrary curvilinear geometry: Spectral-Chebyshev model and experimental study

The spectral-Chebyshev method is firstly applied to the free in-plane vibration of arbitrarily shaped plates with curvilinear geometry under different boundary conditions. With the aim of facilitating the calculation of energy, an arbitrarily shaped plate is mapped into a square plate by the one-to-one coordinate transformation. The displacement functions of the plate after transformation are then generally expressed as the two-dimensional Chebyshev polynomials. The experimental study of in-plane natural frequencies of six aluminum plates with different shapes is carried out for the first time, including free boundary conditions and cantilever support boundary conditions. The proposed spectral-Chebyshev method is applied to simulate the in-plane vibration of six aluminum plates to evaluate the precision and demonstrate the applicability of the current solution. The present calculated natural frequencies converge with the increase of Chebyshev polynomials and are in good agreement with the experimental results and the FEM solution. Thus, our conclusion is that the current spectral-Chebyshev model can accurately and quickly calculate the in-plane vibration of plates with arbitrary curvilinear geometry. Moreover, the in-plane experimental results of plates with six different curvilinear geometries can provide a reference for future theoretical research.

In-plane modal studies of arbitrary laminated triangular plates with elastic boundary constraints by the Chebyshev-Ritz approach

Firstly, the Chebyshev-Ritz method is applied to the free in-plane vibration of arbitrary shaped laminated triangular plates with elastic boundary conditions. In order to facilitate the calculation of energy, the arbitrary shaped triangular laminated plate is mapped into a square plate by the coordinate transformation. The constitutive equation of laminated materials is constructed by the equivalent monolayer theory. The displacement functions of the square plate after transformation are generally expressed as two-dimensional Chebyshev polynomials multiplied by coefficients. By means of artificial virtual spring technology, the arbitrary elastic boundary conditions of the plate can be obtained by changing the stiffness values of each spring. The in-plane free vibration characteristics of the triangular laminated plate under different boundary conditions are calculated and the accuracy of this method is verified by comparing with finite element results and experimental results. In this paper, modal experiments of three different triangular plates with free boundary and cantilever support boundary are carried out. The comparison results show that the present method has good convergence, high efficiency and satisfactory actuarial accuracy. Finally, novelty numerical analysis is carried out, the influence of geometrical properties, material parameters and boundary conditions on in-plane modal characteristics of laminated triangular plates are studied in detail.

Experimental Investigation on Vibration Responses of Fiberglass Reinforced Plastic

The purpose of this study is to analyze the vibration displacement on fiberglass reinforced plastic beams with variations a number of fibers in the resin matrix. Composite beams was made of fiberglass and polyester resin matrix with a number of fiberglass: 0, 24, and 48. Composite beams was manufactured by hand lay-up method with the unidirectional fiber orientation. The composite beams used have the dimension of length: 500 mm, height: 20 mm, and width: 20 mm. During the experimental test, the beam was vibrated using an exciter motor which was placed at the end of the cantilever support then using a vibration meter, the vibration displacement data (mm) was measured by placing the vibration transducer postions : 50 mm, 250 mm, and 450 mm from the cantilever support. During the vibration test, the vibration displacement data on the vibration meter screen were recorded using a camera recorder and the data was taken 6 times at each of measurement points. The experimental and analysis results show that the value of vibration displacement (mm) decreases when the fiberglass is added to the composite beam, or in other words, the addition of fiberglass provides an increase in the ability of the beam to withstand vibrations. The maximum vibration displacement value on composites with 0 fiberglass: 0.641 mm, then the vibration displacement decreased in composites with 24 fiberglass: 0.506 mm and the lowest displacement value for the composites with 48 fiberglass: 0.395 mm. Whereas for 3 measurement points at positions 5 cm, 25 cm, and 45 cm along the beam for three kind of the composites, the maximum value of vibration displacement value was obtained at the end of beam composites or at 45 cm from cantilever support: 0.735 mm on composite beam with 0 fiberglass and minimum at position 5 cm near the cantilever support with the value of vibration displacement: 0.323 mm on composite beam with 48 fiberglass.

Miniature piezoresistive sensor for detecting volatile organic components

This paper reports a piezoresistive gas sensor, which detects the stress of polymer swollen due to sorption of trace gas molecules. The sensor consists of a Si-polymer composite and a Si cantilever with a piezoresistor at the support. The stress is transformed via the cantilever lateral deflection to the strain at the piezoresistor at the cantilever support. The saturation time for water signal is ca 440 s, and the response is reversible. The response rate, d(∆R/R)/dt, exhibits a maximum at 15.5 s. The ethanol and acetone signals show maxima of lower magnitude. The Fickian diffusion model with variable surface concentration of analyte represents very well the sensor response. The predicted maximum response rate is [d(∆R/R)/dt]max∝Sε∞D1/2b1/2, where S is device sensitivity, ε∞, is equilibrium strain of swollen polymer, D is analyte diffusivity, and b is the rate of change of surface concentration of analyte. The response time corresponding to this maximum is tmax∝1/b. For low humidity, the observed sensitivity is S=2.2. An array of sensors, with properly selected polymer sorbents is expected to function as detector of volatile gas components in human breath and/or in atmosphere.

Dynamic Response at Various Points of Aluminum Cantilever Beam

The aim of the study was to analyze the dynamic response along an aluminum cantilever beam. The data measured were displacement (mm), velocity (mm / s), and acceleration (m/s2) with 3 variations of the measurement position on the beam. The 6061 series aluminum beam used have length: 80 cm, height: 32 cm, and width: 32 cm. Data were collected experimentally using a vibration meter to measure beam vibrations at the various positions from the cantilever beam at a distance from support: 10 cm, 35 cm, and 60 cm. The results of the analysis showed that the values ​​of the displacement, velocity and acceleration of the object vibrations change when the measuring point was far from the cantilever support. The maximum displacement value is at 60 cm from the support: 0.02 mm, and the lowest is at 10 cm: 0.12 mm. The velocity value also increases, maximum at 60 cm from the support: 38.58 mm/s and the minimum value at 10 cm: 12.30 mm/s. While the acceleration value, the maximum at 60 cm from the support: 91150 mm/s2 and the minimum at 10 cm: 66900 mm/s2.

Design and failure modes of a standard railway catenary cantilever support

Infrastructure managers of small railways have limited action lines with respect to product development of maintenance components. In many cases, they have a significant number of different components in their operation railway lines. Therefore, they have a poor bargaining power when it comes to ordering components for the railway infrastructure due to small ordering volumes. In addition, a large number of components has to be produced and stored to answer the needs of the operation and maintenance, increasing the overall costs. An approach to reduce the mentioned problems is standardization, which comes as a solution to reduce lifecycle costs due to benefits such as increased production volumes, longer learning curves in manufacturing, maintenance and reduced stock levels. In this paper a set of standard cantilever supports for the railway catenary system were developed thus replacing a set of supports with different designs for similar functions. These components are of critical importance since they are responsible for transmitting the entirety of the pre-loads, as well as train dynamic loads, of the catenary system to the supporting poles. The new proposed solution was modelled and analysed using NX Nastran and ABAQUS simulation tools with contact detection between components. The finite element analyses covered the static behaviour as well as the linear fracture mechanics of cracks in critical areas of the designed cantilever supports. The linear fracture results were also used to estimate the fatigue life of the cantilever supports. The loads were modelled for train speeds of up to 300 km/h. The results indicate that the most likely failure mode is fatigue crack propagation in one of the critical areas of the lower cantilever support under tension with a fatigue life of 8224 load cycles. Due to the low fatigue life of the nodular cast iron GJS-400-15, the B319-T7 and A356-T6 aluminium alloys were also considered, resulting in fatigue lives of 375,990 and 1,093,500 cycles, respectively.

Measurement of the elastic modulus of nanowires based on resonant frequency and boundary condition effects

The elastic modulus of nanowires can be measured by resonant frequency method, in which the elastic modulus is determined using the classical theory of beam deflection. However, the measurement accuracy of the elastic modulus obtained from the resonant frequency can be largely affected by theoretical models and boundary conditions. In the present paper, a theoretical model is developed by considering nonlocal interactions and boundary condition effects of cantilever support. Based on the proposed model, we investigate the influence of nonlocal parameter and elastic foundation on the elastic modulus of carbon nanotubes (CNTs). The results show that the resonant frequency of CNTs is affected by the clamped cantilever condition. Support stiffness and clamped length of CNTS cannot be ignored in determining the elastic modulus of CNTs, especially for CNTs with low stiffness support. After considering the boundary conditions, the influence of cantilever support on the frequency is effectively removed, and the elastic modulus can be precisely determined by measuring the resonant frequency.

The Damping Mechanism of Steel-Rubber Composite Beam under Flexural Dynamic Excitation

Damping is one of the several important parameters in the dynamic system. It reduces amplitude response of a structure, especially around the resonance. The higher the damping, the better the performance (more comfort, lower stress, less fatigue), and the longer the life cycle of the structure will be. There are many types of damper amongst other is the tuned mass damper (TMD), where mass and spring are designed in such that the TMD frequency is close to the natural frequency of the structure in question where the phase angle is about 180 degree out of phase. Applying steel-rubber composite beam as a damper in the TMD system is expected to increase the damping of the structure of interest. The objective of this study is to test experimentally and numerically the dynamic parameters of the rubber-steel composite beam upon a cantilever support system under static load-displacement test and flexural dynamic excitation. The addition of steel (in the form of wire mesh) embedded in the rubber beam significantly increases the stiffness, but the damping ratio, at a small range of displacement. The effectiveness of rubber material in the steel-rubber composite beam is expected when large displacement occurs, meaning that more energy dissipation and larger damping ratio. The established numerical model is able to generate dynamic parameters close to results of the experimental model, but the damping ratios.