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J.r. Klepaczko - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of temperature coupling by thermovision and Constitutive Relation at high strain rates for the dual phase sheet steel
    Journal De Physique Iv, 2003
    Co-Authors: Alexis Rusinek, W. K. Nowacki, P. Gadaj, J.r. Klepaczko
    Abstract:

    The paper presents an original experimental set-up to study the thermo-visco-Plastic behavior of a dual phase sheet steel DP 600. It is also shown how to determine the temperature gradients during shear test at different strain rates varying from 10 -4 < γ ≤ 10 3 s -1 up to large shear strains, γ 1. The temperature increments are measured by an infrared camera recording the infrared radiation emitted from the shear zone during the process of Plastic deformation. Due to combination of a fast hydraulic machine and the direct impact technique with the Hopkinson tube, [1], together with an infrared camera, it was possible to find the stress evolution with the shear strain and the local temperature in the shear zone [2]. At the same time it was possible to estimate the s train rate when the adiabatic shear bands appear. Moreover, an original thermo-visco-Plastic Constitutive Relation is proposed and compared with that by Johnson-Cook, [3].

  • shear testing of a sheet steel at wide range of strain rates and a Constitutive Relation with strain rate and temperature dependence of the flow stress
    International Journal of Plasticity, 2001
    Co-Authors: Alexis Rusinek, J.r. Klepaczko
    Abstract:

    Abstract In this paper, a new experimental technique is reported to study behavior of sheet metals in the range of low and high strain rates. The main purpose of this work was to analyse visco-Plastic behavior of sheet metals for an industrial application. It may be mentioned that a variety of industrial processes, such as drawing or even crashworthiness, involve a wide range of strain rates. The test method which is based on previous work, ( Klepaczko, J.R., 1994 . An experimental technique for shear testing at high and very high strain rates. The case of mild steel. Int. J. Impact Engng. 15, 25–39), is a combination of two experimental techniques, that enables one to obtain the range of strain rates from 10 −4 to 10 3 s −1 , ( Rusinek, A., Klepaczko, J.R., 1998. Etude experimentale du double cisaillement des toles, modelisation de l'ecoulement viscoplastique. Rapport interne, LPMM ). The double-shear specimen is loaded by a fast hydraulic machine, and in the second case a specimen of the same geometry can be loaded by the direct impact of a projectile. The combination of direct impact with the double shear specimen, which is based on the Hopkinson tube technique of force measurement, permits to reduce the rise time of loading in comparison to the bar-tube configuration ( Campbell, J.D., Ferguson, W.G., 1970. The temperature and strain rate dependence of shear strength of mild steel. Phil. Mag. 21, 63–82 ). The combination of two schemes of loading assures a complete determination of the shear stress τ( t ), the shear strain Γ( t ) and shear strain rate Γ (t) as a function of time at wide range of strain rates. The test method has been applied to determine the visco-Plastic behavior of cold rolled, Al-calmed sheet steel used in the automotive industry. The experimental results obtained with those two experimental techniques are in agreement with other reported data. An original visco-Plastic Constitutive Relation has been proposed. It permits to model the viscoPlastic behavior of the sheet metal tested in the whole range of strain rates considered. A general procedure for the identification of the material constants is proposed (Rusinek, A., Klepaczko, J.R., 1998. Etude experimentale du double cisaillement des toles, modelisation de l'ecoulement viscoplatique. Rapport interne, LPMM.). It offers the advantage of subdividing the total number of constants into groups, this procedure simplifies the problem of identification. The Constitutive Relation proposed takes into account the strain hardening, the strain rate sensitivity and temperature effects. A comparison with experimental results is presented in the form of stress–strain curves at different strain rates, up to 10 3 s −1 .

Eugenio Oñate - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear Formulations of a Four-Node Quasi-Conforming Shell Element
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Gilson R. Lomboy, Songsak Suthasupradit, Eugenio Oñate
    Abstract:

    The quasi-conforming technique was introduced in the 1980’s to meet the challenge of inter-elements conforming problems and give a unified treatment of both conforming and nonconforming elements. While the linear formulation is well established, the nonlinear formulation based on the quasi-conforming technique that includes geometric and material nonlinearity is presented in this paper. The formulation is derived in the framework of an updated Lagrangian stress resultant, co-rotational approach. The geometric nonlinear formulation provides solutions to buckling and postbuckling behaviour while the material nonlinear formulation considers the spread of Plasticity within the element while maintaining an explicit construction of element matrices. Aside from the elasto-Plastic Constitutive Relation, formulations on laminate composites and reinforced concrete are also presented. The formulations of laminate composite and reinforced concrete material are present based on the layer concept, the material properties can vary throughout the thickness and across the surface of a shell element. The various failure criteria for laminate composite are included in the formulation which makes it possible to analyses the progressive failure of fibre and matrix. For the reinforced concrete material, the nonlinearities as a result of tensile cracking, tension stiffening between cracks, the nonlinear response of concrete in compression, and the yielding of the reinforcement are considered. The steel reinforcement is modeled as a bilinear material with strain hardening.

  • Nonlinear Formulations of a Four-Node Quasi-Conforming Shell Element
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Gilson R. Lomboy, Songsak Suthasupradit, Eugenio Oñate
    Abstract:

    The quasi-conforming technique was introduced in the 1980’s to meet the challenge of inter-elements conforming problems and give a unified treatment of both conforming and nonconforming elements. While the linear formulation is well established, the nonlinear formulation based on the quasi-conforming technique that includes geometric and material nonlinearity is presented in this paper. The formulation is derived in the framework of an updated Lagrangian stress resultant, co-rotational approach. The geometric nonlinear formulation provides solutions to buckling and postbuckling behaviour while the material nonlinear formulation considers the spread of Plasticity within the element while maintaining an explicit construction of element matrices. Aside from the elasto-Plastic Constitutive Relation, formulations on laminate composites and reinforced concrete are also presented.

Alexis Rusinek - One of the best experts on this subject based on the ideXlab platform.

  • Measurement of temperature coupling by thermovision and Constitutive Relation at high strain rates for the dual phase sheet steel
    Journal De Physique Iv, 2003
    Co-Authors: Alexis Rusinek, W. K. Nowacki, P. Gadaj, J.r. Klepaczko
    Abstract:

    The paper presents an original experimental set-up to study the thermo-visco-Plastic behavior of a dual phase sheet steel DP 600. It is also shown how to determine the temperature gradients during shear test at different strain rates varying from 10 -4 < γ ≤ 10 3 s -1 up to large shear strains, γ 1. The temperature increments are measured by an infrared camera recording the infrared radiation emitted from the shear zone during the process of Plastic deformation. Due to combination of a fast hydraulic machine and the direct impact technique with the Hopkinson tube, [1], together with an infrared camera, it was possible to find the stress evolution with the shear strain and the local temperature in the shear zone [2]. At the same time it was possible to estimate the s train rate when the adiabatic shear bands appear. Moreover, an original thermo-visco-Plastic Constitutive Relation is proposed and compared with that by Johnson-Cook, [3].

  • shear testing of a sheet steel at wide range of strain rates and a Constitutive Relation with strain rate and temperature dependence of the flow stress
    International Journal of Plasticity, 2001
    Co-Authors: Alexis Rusinek, J.r. Klepaczko
    Abstract:

    Abstract In this paper, a new experimental technique is reported to study behavior of sheet metals in the range of low and high strain rates. The main purpose of this work was to analyse visco-Plastic behavior of sheet metals for an industrial application. It may be mentioned that a variety of industrial processes, such as drawing or even crashworthiness, involve a wide range of strain rates. The test method which is based on previous work, ( Klepaczko, J.R., 1994 . An experimental technique for shear testing at high and very high strain rates. The case of mild steel. Int. J. Impact Engng. 15, 25–39), is a combination of two experimental techniques, that enables one to obtain the range of strain rates from 10 −4 to 10 3 s −1 , ( Rusinek, A., Klepaczko, J.R., 1998. Etude experimentale du double cisaillement des toles, modelisation de l'ecoulement viscoplastique. Rapport interne, LPMM ). The double-shear specimen is loaded by a fast hydraulic machine, and in the second case a specimen of the same geometry can be loaded by the direct impact of a projectile. The combination of direct impact with the double shear specimen, which is based on the Hopkinson tube technique of force measurement, permits to reduce the rise time of loading in comparison to the bar-tube configuration ( Campbell, J.D., Ferguson, W.G., 1970. The temperature and strain rate dependence of shear strength of mild steel. Phil. Mag. 21, 63–82 ). The combination of two schemes of loading assures a complete determination of the shear stress τ( t ), the shear strain Γ( t ) and shear strain rate Γ (t) as a function of time at wide range of strain rates. The test method has been applied to determine the visco-Plastic behavior of cold rolled, Al-calmed sheet steel used in the automotive industry. The experimental results obtained with those two experimental techniques are in agreement with other reported data. An original visco-Plastic Constitutive Relation has been proposed. It permits to model the viscoPlastic behavior of the sheet metal tested in the whole range of strain rates considered. A general procedure for the identification of the material constants is proposed (Rusinek, A., Klepaczko, J.R., 1998. Etude experimentale du double cisaillement des toles, modelisation de l'ecoulement viscoplatique. Rapport interne, LPMM.). It offers the advantage of subdividing the total number of constants into groups, this procedure simplifies the problem of identification. The Constitutive Relation proposed takes into account the strain hardening, the strain rate sensitivity and temperature effects. A comparison with experimental results is presented in the form of stress–strain curves at different strain rates, up to 10 3 s −1 .

Gilson R. Lomboy - One of the best experts on this subject based on the ideXlab platform.

  • Nonlinear Formulations of a Four-Node Quasi-Conforming Shell Element
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Gilson R. Lomboy, Songsak Suthasupradit, Eugenio Oñate
    Abstract:

    The quasi-conforming technique was introduced in the 1980’s to meet the challenge of inter-elements conforming problems and give a unified treatment of both conforming and nonconforming elements. While the linear formulation is well established, the nonlinear formulation based on the quasi-conforming technique that includes geometric and material nonlinearity is presented in this paper. The formulation is derived in the framework of an updated Lagrangian stress resultant, co-rotational approach. The geometric nonlinear formulation provides solutions to buckling and postbuckling behaviour while the material nonlinear formulation considers the spread of Plasticity within the element while maintaining an explicit construction of element matrices. Aside from the elasto-Plastic Constitutive Relation, formulations on laminate composites and reinforced concrete are also presented. The formulations of laminate composite and reinforced concrete material are present based on the layer concept, the material properties can vary throughout the thickness and across the surface of a shell element. The various failure criteria for laminate composite are included in the formulation which makes it possible to analyses the progressive failure of fibre and matrix. For the reinforced concrete material, the nonlinearities as a result of tensile cracking, tension stiffening between cracks, the nonlinear response of concrete in compression, and the yielding of the reinforcement are considered. The steel reinforcement is modeled as a bilinear material with strain hardening.

  • Nonlinear Formulations of a Four-Node Quasi-Conforming Shell Element
    Archives of Computational Methods in Engineering, 2009
    Co-Authors: Gilson R. Lomboy, Songsak Suthasupradit, Eugenio Oñate
    Abstract:

    The quasi-conforming technique was introduced in the 1980’s to meet the challenge of inter-elements conforming problems and give a unified treatment of both conforming and nonconforming elements. While the linear formulation is well established, the nonlinear formulation based on the quasi-conforming technique that includes geometric and material nonlinearity is presented in this paper. The formulation is derived in the framework of an updated Lagrangian stress resultant, co-rotational approach. The geometric nonlinear formulation provides solutions to buckling and postbuckling behaviour while the material nonlinear formulation considers the spread of Plasticity within the element while maintaining an explicit construction of element matrices. Aside from the elasto-Plastic Constitutive Relation, formulations on laminate composites and reinforced concrete are also presented.

Xiao-hua He - One of the best experts on this subject based on the ideXlab platform.

  • Study on Limit Load of Double Pipe Bend Combined Fittings
    Volume 3: Design and Analysis, 2015
    Co-Authors: Chang-yu Zhou, Jian Li, Xiao-hua He
    Abstract:

    Pipe bends and double pipe bends combined fittings including Back-to-back pipe combination (BB) and Face-to-face pipe combination (FF) play an important role in pressure pipeline system. Their carrying capacity will affect the integrity and safe operation of whole piping system directly. In this paper Plastic limit loads for double pipe bends combined fittings (BB and FF) are analyzed by finite element method with elastic-perfect-Plastic Constitutive Relation and the corresponding limit load equations are proposed which extends the range of pipe geometry λ Results show that the limit load equations available in references fail to be used for double pipe bends combined fittings and are unsafe, especially for FF combination. The limit loads increase with pipe thickness and bend radius in the meantime. The value of r/t is the main factor affecting limit load solutions. Detailed analysis also demonstrates that with applied load increasing, initial yielding appears in the FF combination firstly and finally overall yielding will happen. While the stress situation of BB combination is close to that of a single pipe bend. Eventually these proposed finite element based results are validated with experiment data and shows that finite element based solutions are believable.Copyright © 2015 by ASME

  • Finite Element Simulation of Limit Load of Components at High Temperature
    Materials Science Forum, 2011
    Co-Authors: Jian Peng, Chang-yu Zhou, Xiao-hua He
    Abstract:

    The creep of materials makes it difficulty to determine the limit load of component at high temperature. In this paper, limit load was obtained by finite element simulation according to isochronous stress versus cumulative strain data and creep failure criterion at high temperature. Firstly, isochronous stress versus cumulative strain data of P91 steel was generated. In finite element analysis code ABAQUS, isochronous stress versus cumulative strain data was replaced by equivalent elastic-Plastic Constitutive Relation. Then, sustained load versus cumulative strain curves at high temperature during service was obtained after finite element simulation. At last, limit load at high temperature during given working hours was determined based on the restriction of total strain at key point of specific component. The restriction of total strain which could also be regarded as long-term fracture strain was discussed in this paper. Finite element simulation of limit load of component at high temperature is simple and reasonable. Limit load of complex component at high temperature during given working hours can be obtained by this method. Using this method, limit loads of a pipe with local wall thinning defect and a branch junction at high temperature during given working hours were obtained as examples.

  • The Limit Load and Safety Assessment of Pressure Pipe With an External Pit Defect at High Temperature
    ASME 2011 Pressure Vessels and Piping Conference: Volume 3, 2011
    Co-Authors: Bo Wang, Chang-yu Zhou, Xiao-hua He
    Abstract:

    Local pit is the common volume defect in high temperature pressure pipe which is widely used in the fields of electric plant, nuclear power station, petrochemical plant and so on. In this paper finite element analysis code ABAQUS was used to simulate limit load of high temperature pressure pipe with an external pit defect which is in service for 105 hours. Four-point bending loading model was applied to calculate the limit load of the pipe. There are three dimensionless factors: relative depth, relative gradient and relative length which characterized the shape of an external pit defect. Orthogonal test of three factors at four different levels was carried out to analyze the sequence of the influence of these three parameters. In present paper when the maximum principal strain reaches 2%, the corresponding load is selected as the limit load. According to this strain criterion and isochronous stress strain data of P91 steel, limit load of high temperature pressure pipe with an external pit was determined by using ABAQUS. Firstly, isochronous stress strain data was generated and was inputted into ABAQUS as equivalent elastic-Plastic Constitutive Relation. Then, sustained load versus cumulative strain curves at high temperature during service was obtained after the simulation. At last, limit loads of high temperature pipe during service time was determined based on 2% total strain criterion. In order to obtain the safety assessment curve of high temperature pipe, five types of limit loads for pressure pipe with an external pit were needed: ultimate limit bending moment, limit internal pressure, limit bending moments at the pressure of 0.25PL ,0.5PL and 0.75PL individually. 16 sets of data formed 16 groups of curves which expressed the Relationship between the ratio of limit pressure and the ratio of limit bending moment for defective pipe and non-defective pipe. Based on the calculation results of limit load for pipe with 16 kinds of defects, a set of limit load formulae were established through multiple nonlinear regression of relative depth, relative gradient and relative length. So the equations of limit load and safety assessment for pressure pipe with an external pit under combined loading of pressure and bending moment were obtained. The results could provide a reference for safety assessment of high temperature creep pressure pipe with local pit defect.Copyright © 2011 by ASME