- TITLE:
MATHEMATICAL MODELLING OF THE STRAIN HARDENING AND CREEP BEHAVIOUR OF ALUMINIUM ALLOY 2024-T3 AT ROOM AND HIGH TEMPERATURE
- AUTHOR(S):
J.T. Maximov, G. V. Duncheva, A. P. Anchev, M. D. Ichkova
- ABSTRACT:
In this paper constitutive models of aluminium alloy 2024-T3 have been developed at room and high temperature in order to be used in finite element simulations of the manufacturing processes. The material behaviour in the plastic field has been described by the nonlinear kinematic hardening on the basis of uniaxial tensile test (half cycle) at 8 different temperatures in the range between 250C and 200 0 C. The
dependence of the yield stress at zero plastic strain and the kinematic hardening modulus C on the temperature have been established when the material parameter is equal to 10. The latter determines the rate at which C decreases with increasing plastic deformation. The constitutive model’ authenticity has been proved by finite element simulations of the uniaxial tensile tests. The creep behaviour of the
aluminium alloy 2024-T3 at high temperatures (150 0C – 200 0 C) has been described by the power-law model. The model’ material parameters A, n and m have been determined as functions of the temperature on the basis of uniaxial creep test. The constitutive model’ authenticity has been proved experimentally and by finite element simulations of the creep test. The obtained constitutive models have been
used in finite element simulations of residual stress relaxation around cold expanded open holes due to thermal overloading.
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MATHEMATICAL MODELLING OF THE STRAIN HARDENING AND CREEP BEHAVIOUR OF ALUMINIUM ALLOY 2024-T3 AT ROOM AND HIGH TEMPERATURE
- TITLE:
AN APPLICATION OF TRIGONOMETRIC SERIES FOR MODELLING OF THE ELASTIC LINE OF STRAIGHT TWO-SUPPORTED BEAM WITH ANGULAR ELASTIC CONNECTIONS
- AUTHOR(S):
J.T. Maximov, V. P. Dunchev
- ABSTRACT:
This article presents a method for modeling of the elastic curve of Euler-Bernoulli straight two-supported beam with angular elastic supports of the end cross-sections. These angular connections restrict the rotations of the end cross-sections when the beam is subjected to bending in principal inertia plane. The beam is statically undetermined. The method is based on an application of infinite trigonometric series. Each combination of simple circular functions, which corresponds to a serial number of the series, satisfies the generalized boundary conditions of the beam. The unknown coefficients in the model are found by means of the principle of virtual displacements for two cases – concentrated force and uniformly distributed load. The beam deflection and bending moments in the end and middle cross-sections are
determined for the generalized boundary conditions through introducing dimensionless functions with general argument. The method has been applied for determination of the basic natural frequency of the beam with generalized boundary conditions.
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AN APPLICATION OF TRIGONOMETRIC SERIES FOR MODELLING OF THE ELASTIC LINE OF STRAIGHT TWO-SUPPORTED BEAM WITH ANGULAR ELASTIC CONNECTIONS
- TITLE:
DYNAMIC BEHAVIOUR OF STRAIGHT BEAM ON ELASTIC SUPPORTS SUBJECTED TO MOVING LOAD – GENERALIZATION OF R. WILLIS’ EQUATION
- AUTHOR(S):
J.T. Maximov, V. P. Dunchev
- ABSTRACT:
This article discusses the dynamic response of Bernoulli-Euler straight beam on elastic supports subjected to moving load with variable velocity. An engineering approach for determination of the dynamic effect from the moving load on the stressed state of the beam has been developed. A dynamic coefficient, a ratio of the dynamic to the static deflection of the beam, has been defined. Generalization of the R. Willis’ equation has been carried out: generalized boundary conditions have been introduced; the force of inertia from normal acceleration, Coriolis force and reduced beam mass have been taken into account. The influence of the boundary conditions and kinematic characteristics of the moving load on the dynamic coefficient has been investigated.
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DYNAMIC BEHAVIOUR OF STRAIGHT BEAM ON ELASTIC SUPPORTS SUBJECTED TO MOVING LOAD – GENERALIZATION OF R. WILLIS’ EQUATION
- TITLE:
SCHEMATICS COMPARISON OF WELDING INVERTERS
- AUTHOR(S):
D. Dankov
- ABSTRACT:
This paper evaluates several DC-DC power converter topologies suitable for arc welding focusing on MMA type (Manual Metal Arc). The aim is to outline the main characteristics of this process that directly affect the electronic design of the DC-DC converter and to set criteria to select the most adequate. They will be compared taking into account schematics, volume, weight, cost and functionality.
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SCHEMATICS COMPARISON OF WELDING INVERTERS
- TITLE:
TRANSFORMER INDUCTION WATER HEATER
- AUTHOR(S):
P. T. Ivanov, R. G. Ivanova
- ABSTRACT:
The present report focuses on submersible transformer induction heater for liquids and in particular for water, operating directly from the power supply grid. The proposed heat exchanger design provides both a relatively large contact area with the liquid (efficient heating) and high cos transformers induction heater.
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TRANSFORMER INDUCTION WATER HEATER
