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Volume 26 (2021): Issue 2 (June 2021)

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Volume 23 (2018): Issue 3 (August 2018)

Volume 23 (2018): Issue 2 (May 2018)

Volume 23 (2018): Issue 1 (February 2018)

Volume 22 (2017): Issue 4 (December 2017)

Volume 22 (2017): Issue 3 (August 2017)

Volume 22 (2017): Issue 2 (May 2017)

Volume 22 (2017): Issue 1 (February 2017)

Volume 21 (2016): Issue 4 (December 2016)

Volume 21 (2016): Issue 3 (August 2016)

Volume 21 (2016): Issue 2 (May 2016)

Volume 21 (2016): Issue 1 (February 2016)

Volume 20 (2015): Issue 4 (December 2015)

Volume 20 (2015): Issue 3 (August 2015)

Volume 20 (2015): Issue 2 (May 2015)

Volume 20 (2015): Issue 1 (February 2015)

Volume 19 (2014): Issue 4 (December 2014)

Volume 19 (2014): Issue 3 (August 2014)

Volume 19 (2014): Issue 2 (May 2014)

Volume 19 (2014): Issue 1 (February 2014)

Volume 18 (2013): Issue 4 (December 2013)

Volume 18 (2013): Issue 3 (August 2013)

Volume 18 (2013): Issue 2 (June 2013)

Volume 18 (2013): Issue 1 (March 2013)

Journal Details
Format
Journal
eISSN
2353-9003
ISSN
1734-4492
First Published
19 Apr 2013
Publication timeframe
4 times per year
Languages
English

Search

Volume 22 (2017): Issue 1 (February 2017)

Journal Details
Format
Journal
eISSN
2353-9003
ISSN
1734-4492
First Published
19 Apr 2013
Publication timeframe
4 times per year
Languages
English

Search

15 Articles
Open Access

Response of Thermoelastic Micropolar Cubic Crystal under Dynamic Load at an Interface

Published Online: 04 Mar 2017
Page range: 5 - 23

Abstract

Abstract

The purpose of this paper is to study the two dimensional deformation in a thermoelastic micropolar solid with cubic symmetry. A mechanical force is applied along the interface of a thermoelastic micropolar solid with cubic symmetry (Medium I) and a thermoelastic solid with microtemperatures (Medium II). The normal mode analysis has been applied to obtain the exact expressions for components of normal displacement, temperature distribution, normal force stress and tangential coupled stress for a thermoelastic micropolar solid with cubic symmetry. The effects of anisotropy, micropolarity and thermoelasticity on the above components have been depicted graphically.

Keywords

  • thermoelasticity
  • cubic symmetry
  • microtemperature
  • normal mode
Open Access

Inductive Decision Tree Analysis of the Validity Rank of Construction Parameters of Innovative Gear Pump after Tooth Root Undercutting

Published Online: 04 Mar 2017
Page range: 25 - 34

Abstract

Abstract

The article presents an innovative use of inductive algorithm for generating the decision tree for an analysis of the rank validity parameters of construction and maintenance of the gear pump with undercut tooth. It is preventet an alternative way of generating sets of decisions and determining the hierarchy of decision variables to existing the methods of discrete optimization.

Keywords

  • inductive decision tree
  • gear pump
  • tooth root undercutting
  • validity rank of the construction parameter
  • optimization
Open Access

Oblique Water Wave Diffraction by a Step

Published Online: 04 Mar 2017
Page range: 35 - 47

Abstract

Abstract

This paper is concerned with the problem of diffraction of an obliquely incident surface water wave train on an obstacle in the form of a finite step. Havelock expansions of water wave potentials are used in the mathematical analysis to obtain the physical parameters reflection and transmission coefficients in terms of integrals. Appropriate multi-term Galerkin approximations involving ultraspherical Gegenbauer polynomials are utilized to obtain a very accurate numerical estimate for reflection and transmission coefficients which are depicted graphically. From these figures various interesting results are discussed.

Keywords

  • finite step
  • Havelock expansion
  • Galerkin approximation
  • Gegenbauer polynomial
  • reflection and transmission coefficients
Open Access

A Numerical Analysis of Selected Elastic-Plastic Fracture Parameters for DEN(T) Plates under Plane Strain Conditions

Published Online: 04 Mar 2017
Page range: 49 - 80

Abstract

Abstract

This paper provides a numerical analysis of selected parameters of fracture mechanics for double-edge notched specimens in tension, DEN(T), under plane strain conditions. The analysis was performed using the elastic-plastic material model. The study involved determining the stress distribution near the crack tip for both small and large deformations. The limit load solution was verified. The J-integral, the crack tip opening displacement, and the load line displacement were determined using the numerical method to propose the new hybrid solutions for calculating these parameters. The investigations also aimed to identify the influence of the plate geometry and the material characteristics on the parameters under consideration. This paper is a continuation of the author’s previous studies and simulations in the field of elastic-plastic fracture mechanics [4, 6, 16, 17, 31].

Keywords

  • DEN(T)
  • fracture mechanics
  • -stress
  • maximum stress
  • -integral
  • CTOD
  • load line displacement
  • limit loads
Open Access

Modelling of Dynamics of a Wheeled Mobile Robot with Mecanum Wheels with the use of Lagrange Equations of the Second Kind

Published Online: 04 Mar 2017
Page range: 81 - 99

Abstract

Abstract

The work presents the dynamic equations of motion of a wheeled mobile robot with mecanum wheels derived with the use of Lagrange equations of the second kind. Mecanum wheels are a new type of wheels used in wheeled mobile robots and they consist of freely rotating rollers attached to the circumference of the wheels. In order to derive dynamic equations of motion of a wheeled mobile robot, the kinetic energy of the system is determined, as well as the generalised forces affecting the system. The resulting mathematical model of a wheeled mobile robot was generated with the use of Maple V software. The results of a solution of inverse and forward problems of dynamics of the discussed object are also published.

Keywords

  • wheeled mobile robots
  • mecanum wheels
  • mathematical model
Open Access

Analysis of the Forming Process of Conical-Like Helical Surfaces with Roller Tools

Published Online: 04 Mar 2017
Page range: 101 - 110

Abstract

Abstract

The article presents a methodology of an analysis and modeling of technological systems and the grinding process of conical-like helical surfaces with the use of modern CAD/CAE systems and calculations in the Matlab system. The methodology developed allows one to carry out simulation tests for the accuracy of the grinding process of helical surfaces taking into consideration the deviations of the location and shape of the system’s elements, axial and radial striking the spindle of the workpiece machined and the grinding wheel as well as the tool’s geometrical features.

Keywords

  • grinding
  • CAD/CAE
  • axial profile
  • helical surface
  • Matlab
Open Access

Hall Effects on Isothermal Vertical Plate with Uniform Mass Diffusion in the Presence of Rotating Fluid and Chemical Reaction of First Order

Published Online: 04 Mar 2017
Page range: 111 - 121

Abstract

Abstract

An exact solution of the combined study of Hall effects on a vertical plate with a rotating fluid in the presence of a homogeneous chemical reaction of first order has been analysed. The dimensionless governing coupled partial differential equations are tackled using the usual Laplace transform technique. The sway of the Hall parameter, Hartmann number, Grashof number, Prandtl number, Schmidt number, chemical reaction parameter on the axial velocity and concentration of the fluid has been depicted graphically. When the non-dimensional angular velocity, Ω=2M21+m.2$\Omega = {{{\it 2}M^2 } \over { {\it 1} + m.^{2} }}$, the transverse velocity component vanishes, thereby the axial velocity of the fluid attains the maximum value. It is noted that with increase in the Hall parameter, thermal Grashof number and mass Grashof number, the axial velocity of the fluid increases significantly.

Keywords

  • Hall effect
  • chemical reaction parameter
  • rotating fluid
  • angular velocity
Open Access

Mixed Convective Fully Developed Flow in a Vertical Channel in the Presence of Thermal Radiation and Viscous Dissipation

Published Online: 04 Mar 2017
Page range: 123 - 144

Abstract

Abstract

The effect of thermal radiation and viscous dissipation on a combined free and forced convective flow in a vertical channel is investigated for a fully developed flow regime. Boussinesq and Roseseland approximations are considered in the modeling of the conduction radiation heat transfer with thermal boundary conditions (isothermal-thermal, isoflux-thermal, and isothermal-flux). The coupled nonlinear governing equations are also solved analytically using the Differential Transform Method (DTM) and regular perturbation method (PM). The results are analyzed graphically for various governing parameters such as the mixed convection parameter, radiation parameter, Brinkman number and perturbation parameter for equal and different wall temperatures. It is found that the viscous dissipation enhances the flow reversal in the case of a downward flow while it counters the flow in the case of an upward flow. A comparison of the Differential Transform Method (DTM) and regular perturbation method (PM) methods shows the versatility of the Differential Transform Method (DTM). The skin friction and the wall temperature gradient are presented for different values of the physical parameters and the salient features are analyzed.

Keywords

  • mixed convection
  • thermal radiation
  • viscous dissipation
  • Differential Transform Method (DTM)
  • Perturbation Method (PM)
Open Access

Unsteady MHD Heat Transfer in Couette Flow of Water at 4°C in a Rotating System with Ramped Temperature via Finite Element Method

Published Online: 04 Mar 2017
Page range: 145 - 161

Abstract

Abstract

An unsteady magnetohydromagnetic natural convection on the Couette flow of electrically conducting water at 4°C (Pr = 11.40) in a rotating system has been considered. A Finite Element Method (FEM) was employed to find the numerical solutions of the dimensionless governing coupled boundary layer partial differential equations. The primary velocity, secondary velocity and temperature of water at 4°C as well as shear stresses and rate of heat transfer have been obtained for both ramped temperature and isothermal plates. The results are independent of the mesh (grid) size and the present numerical solutions through the Finite Element Method (FEM) are in good agreement with the existing analytical solutions by the Laplace Transform Technique (LTT). These are shown in tabular and graphical forms.

Keywords

  • MHD
  • Couette flow
  • heat transfer
  • FEM
Open Access

Effect of Rotation in an Orthotropic Elastic Slab

Published Online: 04 Mar 2017
Page range: 163 - 174

Abstract

Abstract

The fundamental equations of the two dimensional generalized thermoelasticity (L-S model) with one relaxation time parameter in orthotropic elastic slab has been considered under effect of rotation. The normal mode analysis is used to the basic equations of motion and heat conduction equation. Finally, the resulting equations are written in the form of a vector-matrix differential equation which is then solved by the eigenvalue approach. The field variables in the space time domain are obtained numerically. The results corresponding to the cases of conventional thermoelasticity CTE), extended thermoelasticity (ETE) and temperature rate dependent thermoelasticity (TRDTE) are compared by means of graphs.

Keywords

  • Orthotropic elastic slab
  • normal mode analysis
  • effect of rotation
Open Access

Bridges for Pedestrians with Random Parameters using the Stochastic Finite Elements Analysis

Published Online: 04 Mar 2017
Page range: 175 - 197

Abstract

Abstract

The main aim of this paper is to present a Stochastic Finite Element Method analysis with reference to principal design parameters of bridges for pedestrians: eigenfrequency and deflection of bridge span. They are considered with respect to random thickness of plates in boxed-section bridge platform, Young modulus of structural steel and static load resulting from crowd of pedestrians. The influence of the quality of the numerical model in the context of traditional FEM is shown also on the example of a simple steel shield. Steel structures with random parameters are discretized in exactly the same way as for the needs of traditional Finite Element Method. Its probabilistic version is provided thanks to the Response Function Method, where several numerical tests with random parameter values varying around its mean value enable the determination of the structural response and, thanks to the Least Squares Method, its final probabilistic moments.

Keywords

  • bridges for pedestrians
  • eigenfrequencies
  • Stochastic Finite Element Method
  • Response Function Method
  • generalized stochastic perturbation technique
  • reliability analysis
Open Access

On the Uniqueness Conditions and Bifurcation Criteria in Coupled Thermo-Elasto-Plasticity

Published Online: 04 Mar 2017
Page range: 199 - 227

Abstract

Abstract

The global and local conditions of uniqueness and the criteria excluding a possibility of bifurcation of the equilibrium state for small strains are derived. The conditions and criteria are derived analyzing the problem of uniqueness of solution of the basic incremental boundary problem of coupled generalized thermo-elasto-plasticity. This paper is a continuation of some previous works by the author, but contains new derivation of the global and local criteria excluding a possibility of bifurcation of the equilibrium state for a comparison body dependent on statically admissible fields of stress velocity. All the thermal elastoplastic coupling effects, non-associated laws of plastic flow and influence of plastic strains on thermoplastic properties of a body were taken into account in this work. Thus, the mathematical problem considered here is not a self-conjugated problem. The paper contains four Appendices A, B, C and D where the local necessery and sufficient conditions of uniqueness have been derived.

Keywords

  • bifurcation of the equilibrium state
  • conditions and criteria of uniqueness
  • boundary-value problem
  • generalized coupled thermo-elasto-plasticity
  • comparison bodies
  • family of local conditions of uniqueness
  • parameter of the optimization
Open Access

Analysis of Parallelogram Mechanism used to Preserve Remote Center of Motion for Surgical Telemanipulator

Published Online: 04 Mar 2017
Page range: 229 - 240

Abstract

Abstract

This paper presents an analysis of a parallelogram mechanism commonly used to provide a kinematic remote center of motion in surgical telemanipulators. Selected types of parallel manipulator designs, encountered in commercial and laboratory-made designs described in the medical robotics literature, will serve as the research material. Among other things, computer simulations in the ANSYS 13.0 CAD/CAE software environment, employing the finite element method, will be used. The kinematics of the solution of manipulator with the parallelogram mechanism will be determined in order to provide a more complete description. These results will form the basis for the decision regarding the possibility of applying a parallelogram mechanism in an original prototype of a telemanipulator arm.

Keywords

  • parallelogram mechanism
  • surgical telemanipulator
  • robot minimally invasive surgery
  • stiffness FEM analysis
  • RCM mechanism
Open Access

Study of CPM Device used for Rehabilitation and Effective Pain Management Following Knee Alloplasty

Published Online: 04 Mar 2017
Page range: 241 - 251

Abstract

Abstract

This paper defines the design assumptions for the construction of an original demonstration of a CPM device, based on which a solid virtual model will be created in a CAD software environment. The overall dimensions and other input parameters for the design were determined for the entire patient population according to an anatomical atlas of human measures. The medical and physiotherapeutic community were also consulted with respect to the proposed engineering solutions. The virtual model of the CPM device that will be created will be used for computer simulations of changes in motion parameters as a function of time, accounting for loads and static states. The results obtained from computer simulation will be used to confirm the correctness of the design adopted assumptions and of the accepted structure of the CPM mechanism, and potentially to introduce necessary corrections. They will also provide a basis for the development of a control strategy for the laboratory prototype and for the selection of the strategy of the patient's rehabilitation in the future. This paper will be supplemented with identification of directions of further research.

Keywords

  • CPM device
  • rehabilitation robot
  • effective pain management
  • knee alloplasty
  • FEM analysis
Open Access

Similarity Solutions on Mixed Convection Heat Transfer from a Horizontal Surface Saturated in a Porous Medium with Internal Heat Generation

Published Online: 04 Mar 2017
Page range: 253 - 258

Abstract

Abstract

The aim of this work is to study the mixed convection boundary layer flow from a horizontal surface embedded in a porous medium with exponential decaying internal heat generation (IHG). Boundary layer equations are reduced to two ordinary differential equations for the dimensionless stream function and temperature with two parameters: ε, the mixed convection parameter, and λ, the exponent of x. This problem is numerically solved with a system of parameters using built-in codes in Maple. The influences of these parameters on velocity and temperature profiles, and the Nusselt number, are thoroughly compared and discussed.

Keywords

  • mixed convection
  • horizontal porous surface
  • internal heat generation
15 Articles
Open Access

Response of Thermoelastic Micropolar Cubic Crystal under Dynamic Load at an Interface

Published Online: 04 Mar 2017
Page range: 5 - 23

Abstract

Abstract

The purpose of this paper is to study the two dimensional deformation in a thermoelastic micropolar solid with cubic symmetry. A mechanical force is applied along the interface of a thermoelastic micropolar solid with cubic symmetry (Medium I) and a thermoelastic solid with microtemperatures (Medium II). The normal mode analysis has been applied to obtain the exact expressions for components of normal displacement, temperature distribution, normal force stress and tangential coupled stress for a thermoelastic micropolar solid with cubic symmetry. The effects of anisotropy, micropolarity and thermoelasticity on the above components have been depicted graphically.

Keywords

  • thermoelasticity
  • cubic symmetry
  • microtemperature
  • normal mode
Open Access

Inductive Decision Tree Analysis of the Validity Rank of Construction Parameters of Innovative Gear Pump after Tooth Root Undercutting

Published Online: 04 Mar 2017
Page range: 25 - 34

Abstract

Abstract

The article presents an innovative use of inductive algorithm for generating the decision tree for an analysis of the rank validity parameters of construction and maintenance of the gear pump with undercut tooth. It is preventet an alternative way of generating sets of decisions and determining the hierarchy of decision variables to existing the methods of discrete optimization.

Keywords

  • inductive decision tree
  • gear pump
  • tooth root undercutting
  • validity rank of the construction parameter
  • optimization
Open Access

Oblique Water Wave Diffraction by a Step

Published Online: 04 Mar 2017
Page range: 35 - 47

Abstract

Abstract

This paper is concerned with the problem of diffraction of an obliquely incident surface water wave train on an obstacle in the form of a finite step. Havelock expansions of water wave potentials are used in the mathematical analysis to obtain the physical parameters reflection and transmission coefficients in terms of integrals. Appropriate multi-term Galerkin approximations involving ultraspherical Gegenbauer polynomials are utilized to obtain a very accurate numerical estimate for reflection and transmission coefficients which are depicted graphically. From these figures various interesting results are discussed.

Keywords

  • finite step
  • Havelock expansion
  • Galerkin approximation
  • Gegenbauer polynomial
  • reflection and transmission coefficients
Open Access

A Numerical Analysis of Selected Elastic-Plastic Fracture Parameters for DEN(T) Plates under Plane Strain Conditions

Published Online: 04 Mar 2017
Page range: 49 - 80

Abstract

Abstract

This paper provides a numerical analysis of selected parameters of fracture mechanics for double-edge notched specimens in tension, DEN(T), under plane strain conditions. The analysis was performed using the elastic-plastic material model. The study involved determining the stress distribution near the crack tip for both small and large deformations. The limit load solution was verified. The J-integral, the crack tip opening displacement, and the load line displacement were determined using the numerical method to propose the new hybrid solutions for calculating these parameters. The investigations also aimed to identify the influence of the plate geometry and the material characteristics on the parameters under consideration. This paper is a continuation of the author’s previous studies and simulations in the field of elastic-plastic fracture mechanics [4, 6, 16, 17, 31].

Keywords

  • DEN(T)
  • fracture mechanics
  • -stress
  • maximum stress
  • -integral
  • CTOD
  • load line displacement
  • limit loads
Open Access

Modelling of Dynamics of a Wheeled Mobile Robot with Mecanum Wheels with the use of Lagrange Equations of the Second Kind

Published Online: 04 Mar 2017
Page range: 81 - 99

Abstract

Abstract

The work presents the dynamic equations of motion of a wheeled mobile robot with mecanum wheels derived with the use of Lagrange equations of the second kind. Mecanum wheels are a new type of wheels used in wheeled mobile robots and they consist of freely rotating rollers attached to the circumference of the wheels. In order to derive dynamic equations of motion of a wheeled mobile robot, the kinetic energy of the system is determined, as well as the generalised forces affecting the system. The resulting mathematical model of a wheeled mobile robot was generated with the use of Maple V software. The results of a solution of inverse and forward problems of dynamics of the discussed object are also published.

Keywords

  • wheeled mobile robots
  • mecanum wheels
  • mathematical model
Open Access

Analysis of the Forming Process of Conical-Like Helical Surfaces with Roller Tools

Published Online: 04 Mar 2017
Page range: 101 - 110

Abstract

Abstract

The article presents a methodology of an analysis and modeling of technological systems and the grinding process of conical-like helical surfaces with the use of modern CAD/CAE systems and calculations in the Matlab system. The methodology developed allows one to carry out simulation tests for the accuracy of the grinding process of helical surfaces taking into consideration the deviations of the location and shape of the system’s elements, axial and radial striking the spindle of the workpiece machined and the grinding wheel as well as the tool’s geometrical features.

Keywords

  • grinding
  • CAD/CAE
  • axial profile
  • helical surface
  • Matlab
Open Access

Hall Effects on Isothermal Vertical Plate with Uniform Mass Diffusion in the Presence of Rotating Fluid and Chemical Reaction of First Order

Published Online: 04 Mar 2017
Page range: 111 - 121

Abstract

Abstract

An exact solution of the combined study of Hall effects on a vertical plate with a rotating fluid in the presence of a homogeneous chemical reaction of first order has been analysed. The dimensionless governing coupled partial differential equations are tackled using the usual Laplace transform technique. The sway of the Hall parameter, Hartmann number, Grashof number, Prandtl number, Schmidt number, chemical reaction parameter on the axial velocity and concentration of the fluid has been depicted graphically. When the non-dimensional angular velocity, Ω=2M21+m.2$\Omega = {{{\it 2}M^2 } \over { {\it 1} + m.^{2} }}$, the transverse velocity component vanishes, thereby the axial velocity of the fluid attains the maximum value. It is noted that with increase in the Hall parameter, thermal Grashof number and mass Grashof number, the axial velocity of the fluid increases significantly.

Keywords

  • Hall effect
  • chemical reaction parameter
  • rotating fluid
  • angular velocity
Open Access

Mixed Convective Fully Developed Flow in a Vertical Channel in the Presence of Thermal Radiation and Viscous Dissipation

Published Online: 04 Mar 2017
Page range: 123 - 144

Abstract

Abstract

The effect of thermal radiation and viscous dissipation on a combined free and forced convective flow in a vertical channel is investigated for a fully developed flow regime. Boussinesq and Roseseland approximations are considered in the modeling of the conduction radiation heat transfer with thermal boundary conditions (isothermal-thermal, isoflux-thermal, and isothermal-flux). The coupled nonlinear governing equations are also solved analytically using the Differential Transform Method (DTM) and regular perturbation method (PM). The results are analyzed graphically for various governing parameters such as the mixed convection parameter, radiation parameter, Brinkman number and perturbation parameter for equal and different wall temperatures. It is found that the viscous dissipation enhances the flow reversal in the case of a downward flow while it counters the flow in the case of an upward flow. A comparison of the Differential Transform Method (DTM) and regular perturbation method (PM) methods shows the versatility of the Differential Transform Method (DTM). The skin friction and the wall temperature gradient are presented for different values of the physical parameters and the salient features are analyzed.

Keywords

  • mixed convection
  • thermal radiation
  • viscous dissipation
  • Differential Transform Method (DTM)
  • Perturbation Method (PM)
Open Access

Unsteady MHD Heat Transfer in Couette Flow of Water at 4°C in a Rotating System with Ramped Temperature via Finite Element Method

Published Online: 04 Mar 2017
Page range: 145 - 161

Abstract

Abstract

An unsteady magnetohydromagnetic natural convection on the Couette flow of electrically conducting water at 4°C (Pr = 11.40) in a rotating system has been considered. A Finite Element Method (FEM) was employed to find the numerical solutions of the dimensionless governing coupled boundary layer partial differential equations. The primary velocity, secondary velocity and temperature of water at 4°C as well as shear stresses and rate of heat transfer have been obtained for both ramped temperature and isothermal plates. The results are independent of the mesh (grid) size and the present numerical solutions through the Finite Element Method (FEM) are in good agreement with the existing analytical solutions by the Laplace Transform Technique (LTT). These are shown in tabular and graphical forms.

Keywords

  • MHD
  • Couette flow
  • heat transfer
  • FEM
Open Access

Effect of Rotation in an Orthotropic Elastic Slab

Published Online: 04 Mar 2017
Page range: 163 - 174

Abstract

Abstract

The fundamental equations of the two dimensional generalized thermoelasticity (L-S model) with one relaxation time parameter in orthotropic elastic slab has been considered under effect of rotation. The normal mode analysis is used to the basic equations of motion and heat conduction equation. Finally, the resulting equations are written in the form of a vector-matrix differential equation which is then solved by the eigenvalue approach. The field variables in the space time domain are obtained numerically. The results corresponding to the cases of conventional thermoelasticity CTE), extended thermoelasticity (ETE) and temperature rate dependent thermoelasticity (TRDTE) are compared by means of graphs.

Keywords

  • Orthotropic elastic slab
  • normal mode analysis
  • effect of rotation
Open Access

Bridges for Pedestrians with Random Parameters using the Stochastic Finite Elements Analysis

Published Online: 04 Mar 2017
Page range: 175 - 197

Abstract

Abstract

The main aim of this paper is to present a Stochastic Finite Element Method analysis with reference to principal design parameters of bridges for pedestrians: eigenfrequency and deflection of bridge span. They are considered with respect to random thickness of plates in boxed-section bridge platform, Young modulus of structural steel and static load resulting from crowd of pedestrians. The influence of the quality of the numerical model in the context of traditional FEM is shown also on the example of a simple steel shield. Steel structures with random parameters are discretized in exactly the same way as for the needs of traditional Finite Element Method. Its probabilistic version is provided thanks to the Response Function Method, where several numerical tests with random parameter values varying around its mean value enable the determination of the structural response and, thanks to the Least Squares Method, its final probabilistic moments.

Keywords

  • bridges for pedestrians
  • eigenfrequencies
  • Stochastic Finite Element Method
  • Response Function Method
  • generalized stochastic perturbation technique
  • reliability analysis
Open Access

On the Uniqueness Conditions and Bifurcation Criteria in Coupled Thermo-Elasto-Plasticity

Published Online: 04 Mar 2017
Page range: 199 - 227

Abstract

Abstract

The global and local conditions of uniqueness and the criteria excluding a possibility of bifurcation of the equilibrium state for small strains are derived. The conditions and criteria are derived analyzing the problem of uniqueness of solution of the basic incremental boundary problem of coupled generalized thermo-elasto-plasticity. This paper is a continuation of some previous works by the author, but contains new derivation of the global and local criteria excluding a possibility of bifurcation of the equilibrium state for a comparison body dependent on statically admissible fields of stress velocity. All the thermal elastoplastic coupling effects, non-associated laws of plastic flow and influence of plastic strains on thermoplastic properties of a body were taken into account in this work. Thus, the mathematical problem considered here is not a self-conjugated problem. The paper contains four Appendices A, B, C and D where the local necessery and sufficient conditions of uniqueness have been derived.

Keywords

  • bifurcation of the equilibrium state
  • conditions and criteria of uniqueness
  • boundary-value problem
  • generalized coupled thermo-elasto-plasticity
  • comparison bodies
  • family of local conditions of uniqueness
  • parameter of the optimization
Open Access

Analysis of Parallelogram Mechanism used to Preserve Remote Center of Motion for Surgical Telemanipulator

Published Online: 04 Mar 2017
Page range: 229 - 240

Abstract

Abstract

This paper presents an analysis of a parallelogram mechanism commonly used to provide a kinematic remote center of motion in surgical telemanipulators. Selected types of parallel manipulator designs, encountered in commercial and laboratory-made designs described in the medical robotics literature, will serve as the research material. Among other things, computer simulations in the ANSYS 13.0 CAD/CAE software environment, employing the finite element method, will be used. The kinematics of the solution of manipulator with the parallelogram mechanism will be determined in order to provide a more complete description. These results will form the basis for the decision regarding the possibility of applying a parallelogram mechanism in an original prototype of a telemanipulator arm.

Keywords

  • parallelogram mechanism
  • surgical telemanipulator
  • robot minimally invasive surgery
  • stiffness FEM analysis
  • RCM mechanism
Open Access

Study of CPM Device used for Rehabilitation and Effective Pain Management Following Knee Alloplasty

Published Online: 04 Mar 2017
Page range: 241 - 251

Abstract

Abstract

This paper defines the design assumptions for the construction of an original demonstration of a CPM device, based on which a solid virtual model will be created in a CAD software environment. The overall dimensions and other input parameters for the design were determined for the entire patient population according to an anatomical atlas of human measures. The medical and physiotherapeutic community were also consulted with respect to the proposed engineering solutions. The virtual model of the CPM device that will be created will be used for computer simulations of changes in motion parameters as a function of time, accounting for loads and static states. The results obtained from computer simulation will be used to confirm the correctness of the design adopted assumptions and of the accepted structure of the CPM mechanism, and potentially to introduce necessary corrections. They will also provide a basis for the development of a control strategy for the laboratory prototype and for the selection of the strategy of the patient's rehabilitation in the future. This paper will be supplemented with identification of directions of further research.

Keywords

  • CPM device
  • rehabilitation robot
  • effective pain management
  • knee alloplasty
  • FEM analysis
Open Access

Similarity Solutions on Mixed Convection Heat Transfer from a Horizontal Surface Saturated in a Porous Medium with Internal Heat Generation

Published Online: 04 Mar 2017
Page range: 253 - 258

Abstract

Abstract

The aim of this work is to study the mixed convection boundary layer flow from a horizontal surface embedded in a porous medium with exponential decaying internal heat generation (IHG). Boundary layer equations are reduced to two ordinary differential equations for the dimensionless stream function and temperature with two parameters: ε, the mixed convection parameter, and λ, the exponent of x. This problem is numerically solved with a system of parameters using built-in codes in Maple. The influences of these parameters on velocity and temperature profiles, and the Nusselt number, are thoroughly compared and discussed.

Keywords

  • mixed convection
  • horizontal porous surface
  • internal heat generation

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