4/2006 Advanced Implementations of Computational Thermo-Mechanics

Contents:

• J.Bobinski, FE Analysis of Strain Localization in Concrete in Elasto-plasticity and Damage Mechanics with Non-local Softening - abstract | full text
• M.Karcz, Mean and Turbulent Thermal Fields Due to Film Cooling Via an Eddy Heat Diffusivity Closure - abstract | full text
• L.Bohdal and L.Kukielka, The Effect of Selected Material Parameters on the Stress and Strain States in the Process of Cutting a Sheet Plate with Circular Cutters - abstract | full text
• W.Sobieski, Mass Exchange Model in Flows with Cavitation - abstract | full text
• R.Kucharski, Modeling Ductile Damage of Steel in Aggressive Environment - abstract | full text
• P.Kaldunski and L.Kukielka, Numerical Analysis of Sheet Metal Forming: the Corrugation Effect - abstract | full text
• A.Ambroziak and P.Klosowski, Survey of Modern Trends in Analysis of Continuum Damage Mechanics - abstract | full text
• A. Wisniewski and R.Kucharski, Eigencharacteristics of Fluid Filled Tanks an Extended Symmetrical Coupled Approach - abstract | full text
• W.Dudda, The Truss Overload Analysis Under Corrosive Degradation - abstract | full text

Abstracts:

• J.Bobinski, FE Analysis of Strain Localization in Concrete in Elasto-plasticity and Damage Mechanics with Non-local Softening

  Results of FEM simulations of a strain localization in concrete specimens are presented. Two different continuum approaches have been used to model to behaviour of concrete: (i) an elasto-plastic constitutive law with the Drucker-Prager criterion in the compression regime and the Rankine criterion in the tensile regime, with isotropic hardening and softening and (ii) an isotropic continuum damage model with the equivalent strain corresponding to the Rankine failure criterion and modified Huber-Mises criterion in terms of strains, with exponential softening. Both constitutive models were enriched by non-local terms to describe strain localization properly, ensure mesh-independence in the softening regime and capture the deterministic size effect. The constitutive models were used to simulate strain localization in concrete in two boundary value problems under plane strain conditions, viz. uniaxial tension and three-point bending. The effect of the characteristic length on load-displacement curves and widths of strain localization is discussed.

• M.Karcz, Mean and Turbulent Thermal Fields Due to Film Cooling Via an Eddy Heat Diffusivity Closure

  The two-equation level of turbulent heat flux modelling is considered for application in film cooling instead of the turbulent Prandtl number concept. The investigations involve numerical analysis of mean and fluctuating temperature fields near the coolant injection inlet. The results of the implemented coupled v²−f−k_θ−ε_θ model are compared with measurement data for a flat plate cooled with compound angle orientation of discrete injection holes. The results of numerical analysis agree very well with the experimental data. The coupled model offers a detailed picture of gas turbine cooling problems without using time-consuming, inherently unsteady models.

• L.Bohdal and L.Kukielka, The Effect of Selected Material Parameters on the Stress and Strain States in the Process of Cutting a Sheet Plate with Circular Cutters

  The influence of the type of material on deformations and stresses of sheet metal in the process of cutting with numerical tools is presented. The Cowper-Symonds model is used to describe the properties of cut sheet-plate and the influence of two parameters C and P on the state of stresses and strains in steel cutting element. Numerical results were obtained by the finite element method (FEM) making use of the ANSYS LS-DYNA ver. 9.0 program, based on the explicit time method.

• W.Sobieski, Mass Exchange Model in Flows with Cavitation

  The paper presents a mathematical model of three-component flow of the liquid-liquid vapor-gas type including the mass exchange between the liquid and its vapor. The model is implemented in the Multi Flower 2D calculation package and used for computer simulations of flows with cavitation. An algorithm for model implementation, basic tests and an example of application are presented. The model's quality was assessed with a special test station equipped with a cavitation chamber allowing cavitation studies. The final section of the paper includes a qualitative comparison of observations made at the laboratory station with the results of numerical simulations, discusses the model's advanrages, disadvantages and possible further development.

• R.Kucharski, Modeling Ductile Damage of Steel in Aggressive Environment

  This paper is a proposition of a new damage model, extended to include the influence of the external environment, based on the Gurson yield function and a new damage evolution equation. The model also contains a mass transport equation based on Fick's law. A comparison of experimental and numerical results is included.

• P.Kaldunski and L.Kukielka, Numerical Analysis of Sheet Metal Forming: the Corrugation Effect

  A new approach to solving the problem of the sheet-flange corrugation in the process of forming cylindrical sheet-metal elements is presented. A brief characteristic of the dynamic central-difference method is given. Technological parameters of a forming disk, a die block and a plunger die have been selected from references. Sample results of computer simulations with stress distributions in a disk are presented and serve as the basis for discussing the process of sheet metal forming.

• A.Ambroziak and P.Klosowski, Survey of Modern Trends in Analysis of Continuum Damage Mechanics

  A brief review of the damage mechanics literature is given. As this area of scientific research is very modern, the authors have restricted themselves to about 100 most important books and papers. Basic equations to introduce the isotropic model in the framework of thermodynamics are given in a form easily applicable in numerical symulations.

• A. Wisniewski and R.Kucharski, Eigencharacteristics of Fluid Filled Tanks an Extended Symmetrical Coupled Approach

  In the numerical analysis of the eigen behaviour of large liquid and gas storage tanks, an important role is played by initial pre-stressing of such thin-walled structures due to high fluid pressure and gravity. In a majority of numerical simulations, the finite state of deformation is first calculated, following which small, linear vibrations are superimposed on the finite state. This paper is devoted to refinement and assessment of the basic Eckart superimposed eigencharacteristics problem simultaneously stated in fluid and thin-walled structures. Eckart's coupled approach leads to variational structure-fluid coupling in the so-called acoustic approximation. In order to verify the feasibility and correctness of the symmetrical Eckart approach, finite element discretization and a calculation example of a rectangular tank are presented. The calculated results are compared with literature ones.

• W.Dudda, The Truss Overload Analysis Under Corrosive Degradation

  A contribution to analytical and numerical tools is presented that permits deterministic evaluation of structures' behavior under multiparameter and/or cyclic mechanical, thermal and chemical loads. Particular structure elements undergo plastic and corrosive degradation and dissipate energy, which consists of irreversible contributions, like the work of inelastic strains. The construction and its units' lifetime are estimated according to the dissipated energy criterion. Modeling and numerical implementation of degradation effects are discussed, including cyclic plasticity generated by mechanical and thermal loads, stress corrosion, electrochemical corrosion and low-cyclic corrosion.