• Advances in concrete construction
• /
• v.5 no.6
• /
• pp.575-586
• /
• 2017

The disposal of polythene waste and fly ash is causing serious threat to the environment. Aim of this study is to decrease environmental pollution by using polythene waste and fly ash in concrete. In this study, cement was partially replaced with 0%, 5%, 10%, 15% and 20% fly ash (by weight) and plastic waste was added in shredded form at 0.6% by weight of concrete. The specimens were prepared for the concrete mix of M25 grade and water to cementitious material ratio (w/c) was maintained as 0.45. Fresh concrete property like workability was examined during casting the specimens. Hardened properties were found out by carrying out the experimental work on cubes, cylinders and beams which were cast in laboratory and their behavior under test were observed at 7 & 28 days for compressive strength and at 28 days for density, flexural strength, dynamic modulus of elasticity, abrasion resistance, water permeability and impact resistance. Overall results of this study show that addition of 0.6% (by weight of the concrete) plastic waste with 10% (by weight of cement) replacement of cement by fly ash result an improvement in properties of the concrete than conventional mix.

• Structural Engineering and Mechanics
• /
• v.81 no.6
• /
• pp.769-780
• /
• 2022

This paper studies the dynamic behavior of laminated composite circular cylindrical shells interacting with a fluid. The mathematical formulation of the dynamic problem for an elastic body is developed based on the variational principle of virtual displacements and the relations of linear elasticity theory. The behavior of an ideal compressible fluid is described by the potential theory, the equations of which together with boundary conditions are transformed to a weak form. The hydrodynamic pressure exerted by the fluid on the internal surface of the shell is calculated according to the linearized Bernoulli equation. The numerical implementation of the mathematical formulation has been done using the semi-analytical finite element method. The influence of the ply angle and lay-up configurations of laminated composites on the natural vibration frequencies and the hydroelastic stability boundary have been analyzed for shells with different geometrical dimensions and under different kinematic boundary conditions set at their edges. It has been found that the optimal value of the ply angle depends on the level of filling of the shell with a fluid. The obtained results support the view that by choosing the optimal configuration of the layered composite material it is possible to change upwards or downwards the frequency and mode shape, as well as the critical velocity for stability loss over a wide range.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.502-502
• /
• 2007

A catenary system should be designed to have an uniform elasticity over a span in order to maintain the lowest possible loss of contact between a pantograph and a contact wire. A elasticity uniformity of a catenary can be regarded as a important design factor used for predicting the current collection performance for a catenary. There are a couple of formulas to calculate the degree of elasticity uniformity of a catenary according to the literature survey. The effectiveness of these formulas is reviewed by performing catenary elasticity and loss of contact analysis for various different configurations of catenary systems using a beam element based FEM program. The results reveals that these formulas are not suitable to predict the current collection performance for a catenary. Therefore, a new formula based on the standard deviation of the elasticity over a span is proposed in this study. The analysis results show that the new formula for an elasticity uniformity of a catenary is very effective in predicting the current collection performance for a catenary.

• Computers and Concrete
• /
• v.20 no.3
• /
• pp.297-310
• /
• 2017

A CFD software was used to simulate free surface flow of SCC in the T-Box test. In total, seven simulations were developed to study the effect of rheological parameters on the non-restricted flow performance of SCC in both horizontal and vertical directions. Different suspending fluids having five plastic viscosity values between 10 and 50 Pa.s, three yield stress values between 14 and 75 Pa, one density of $2500kg/m^3$, and one shear elasticity modulus of 100 Pa were considered for suspension of 178 spherical particles of 20-mm diameter and $2500kg/m^3$ density. The results of the simulations are found to correlate well to changes in rheological parameters of the suspending fluid. Plastic viscosity was shown to be the most dominant parameter affecting flowability and dynamic stability compared to the yield stress. A new approach was proposed to evaluate performability of SCC based on a trade-off between flowability and dynamic stability.

• Journal of the Korean Society for Precision Engineering
• /
• v.6 no.4
• /
• pp.126-135
• /
• 1989

In this study, in order to perform dynamic design of machine tools reasonably and effectively, a method was formulated to be applicable to the structures connected by joints having elasticity and damping by using substructure synthesis method. And to analyze chatter-free performance, a 3 dimensional cutting dynamics theory was used. Computer program package for the dynamic design of machine tools was developed by combining those and spplied to improvement of performance of NC lathe. Also, the optimization in the structural modifications of machine tool substructure was studied by evaluating the effects of the substructural modifications on total system performance.

• Advances in materials Research
• /
• v.8 no.3
• /
• pp.179-196
• /
• 2019

This paper researches static and dynamic bending behaviors of a crystalline nano-size shell having pores and grains in the framework of strain gradient elasticity. Thus, the nanoshell is made of a multi-phase porous material for which all material properties on dependent on the size of grains. Also, in order to take into account small size effects much accurately, the surface energies related to grains and pores have been considered. In order to take into account all aforementioned factors, a micro-mechanical procedure has been applied for describing material properties of the nanoshell. A numerical trend is implemented to solve the governing equations and derive static and dynamic deflections. It will be proved that the static and dynamic deflections of the crystalline nanoshell rely on pore size, grain size, pore percentage, load location and strain gradient coefficient.

• Advances in nano research
• /
• v.8 no.2
• /
• pp.157-167
• /
• 2020

This paper studies forced vibrational behavior of porous nanocrystalline silicon nanoshells under radial dynamic loads using strain gradient theory (SGT). This type of material contains many pores inside it and also there are nano-size grains which define the material character. The formulation for nanocrystalline nanoshell is provided by first order shell theory and a numerical approach is used in order to solve nanoshell equations. SGT gives a scale factor related to stiffness hardening provided by nano-grains. For more accurate description of size effects due to nano-grains or nano-pore, their surface energy influences have been introduced. Surface energy of inclusion exhibit extraordinary influence on dynamic response of the nanoshell. Also, dynamic response of the nanoshell is affected by the scale of nano-grain and nano-pore.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.1
• /
• pp.418-429
• /
• 2018

This paper studies the decentralized position/force control problem for constrained reconfigurable manipulator without torque sensing. A novel joint torque estimation scheme that exploits the existing structural elasticity of the manipulator joint with harmonic drive model is applied for each joint module. Based on the estimated joint torque and dynamic output feedback technique, a decentralized position/force control strategy is presented. In order to solve the problem of controller parameter perturbation, the non-fragile robust technique is introduced into the dynamic output feedback controller. Subsequently, the stability of the closed-loop system is proved using the Lyapunov theory and linear matrix inequality (LMI) technique. Finally, two 2-DOF constrained reconfigurable manipulators with different configurations are applied to verify the effectiveness of the proposed control scheme in numerical simulation.

• Structural Engineering and Mechanics
• /
• v.22 no.1
• /
• pp.107-130
• /
• 2006

The paper deals with the numerical solution of the dynamic problem of masonry structures. Masonry is modelled as a non-linear elastic material with zero tensile strength and infinite compressive strength. Due to the non-linearity of the adopted constitutive equation, the equations of the motion must be integrated directly. In particular, we apply the Newmark or the Hilber-Hughes-Taylor methods implemented in code NOSA to perform the time integration of the system of ordinary differential equations obtained from discretising the structure into finite elements. Moreover, with the aim of evaluating the effectiveness of these two methods, some dynamic problems, whose explicit solutions are known, have been solved numerically. Comparisons between the exact solutions and the corresponding approximate solutions obtained via the Newmark and Hilber-Hughes-Taylor methods show that in the cases under consideration both numerical methods yield satisfactory results.

• Advances in materials Research
• /
• v.12 no.3
• /
• pp.193-210
• /
• 2023

This paper aims to analyze the dynamic response of a double nanobeam system with a medium viscoelastic layer under a moving load. The governing equations are based on the Eringen nonlocal theory. A thin viscoelastic layer has coupled two nanobeams together. An exact solution is derived for each nanobeam, and the dynamic deflection is achieved. The effect of parameters such as nonlocal parameter, velocity of moving load, spring coefficient and the viscoelastic layer damping ratio was studied. The results showed that the effect of the nonlocal parameter is significantly important and the classical theories are not suitable for nano and microstructures.