Determination of Material Constants of Internal Time Theory of Plasticity and Creep for Fatigue Analysis and Creep-Fatigue Analysis

2011 ◽  
Author(s):  
Osamu Watanabe
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Fatigue Analysis ◽  
Computer Hardware ◽  
Computational Time ◽  
Inelastic Behavior ◽  
Material Constants ◽  
Creep Fatigue ◽  
Recent Computer

Recent computer hardware is greatly developed to make possible fatigue analysis and creep-fatigue analysis of structures, which takes much computational time in the past. The code and standard recommend the simplified method in the fatigue analysis and creep-fatigue analysis instead of the detailed inelastic finite element solutions. It is widely recognized that the employed constitutive model affects inelastic finite element solutions significantly. However, the inelastic finite element solutions can consider effects of geometry shape or boundary conditions easily compared to the simplified methods. The other advantage of the inelastic solutions can also assist the mechanism of inelastic deformations. Thus, the accurate inelastic finite element solution is still intense research subject in this area.. The present paper will study constitutive model and the determination method of the material constants for the fatigue analysis and creep-fatigue analysis in order to simulate inelastic behavior at saturated condition, which differs from those at the initial loading.

scholarly journals Stiffness Estimation and Equivalence of Boundary Conditions in FEM Models

2021 ◽  
Vol 11 (4) ◽  
pp. 1482
Author(s):  
Róbert Huňady ◽  
Pavol Lengvarský ◽  
Peter Pavelka ◽  
Adam Kaľavský ◽  
Jakub Mlotek
Keyword(s):  
Boundary Condition ◽  
Finite Element ◽  
Boundary Conditions ◽  
Model Updating ◽  
Element Model ◽  
Computational Time ◽  
Stiffness Coefficients ◽  
First Case ◽  
Numerical Approaches

The paper deals with methods of equivalence of boundary conditions in finite element models that are based on finite element model updating technique. The proposed methods are based on the determination of the stiffness parameters in the section plate or region, where the boundary condition or the removed part of the model is replaced by the bushing connector. Two methods for determining its elastic properties are described. In the first case, the stiffness coefficients are determined by a series of static finite element analyses that are used to obtain the response of the removed part to the six basic types of loads. The second method is a combination of experimental and numerical approaches. The natural frequencies obtained by the measurement are used in finite element (FE) optimization, in which the response of the model is tuned by changing the stiffness coefficients of the bushing. Both methods provide a good estimate of the stiffness at the region where the model is replaced by an equivalent boundary condition. This increases the accuracy of the numerical model and also saves computational time and capacity due to element reduction.

Use of DNVGL-RP-C203 for Determining the Fatigue Capacity of Connectors

2021 ◽  
Author(s):  
Anthony Muff ◽  
Anders Wormsen ◽  
Torfinn Hørte ◽  
Arne Fjeldstad ◽  
Per Osen ◽  
...  
Keyword(s):  
Finite Element ◽  
Fatigue Testing ◽  
Experimental Testing ◽  
High Strength ◽  
Element Model ◽  
Fatigue Analysis ◽  
Full Scale ◽  
The Finite Element Model

Abstract Guidance for determining a S-N based fatigue capacity (safe life design) for preloaded connectors is included in Section 5.4 of the 2019 edition of DNVGL-RP-C203 (C203-2019). This section includes guidance on the finite element model representation, finite element based fatigue analysis and determination of the connector design fatigue capacity by use of one of the following methods: Method 1 by FEA based fatigue analysis, Method 2 by FEA based fatigue analysis and experimental testing and Method 3 by full-scale connector fatigue testing. The FEA based fatigue analysis makes use of Appendix D.2 in C203-2019 (“S-N curves for high strength steel applications for subsea”). Practical use of Section 5.4 is illustrated with a case study of a fatigue tested wellhead profile connector segment test. Further developments of Section 5.4 of C203-2019 are proposed. This included acceptance criteria for use of a segment test to validate the FEA based fatigue analysis of a full-scale preloaded connector.

Application of Various Spectral Fatigue Analysis Methods for Ship Structures

2021 ◽  
Vol 163 (A3) ◽  
Author(s):  
Y Parihar ◽  
A Negi ◽  
S Vhanmane
Keyword(s):  
Finite Element ◽  
Structural Analysis ◽  
Fatigue Analysis ◽  
Panel Method ◽  
Life Assessment ◽  
Computational Time ◽  
Element Analysis ◽  
Design Assessment ◽  
Hydrodynamic Analysis ◽  
Strip Method

The Spectral Fatigue Analysis (SFA) is a comprehensive fatigue life assessment method. The SFA is performed by following a systematic process at the onset of hydrodynamic analysis, structural analysis, and spectral analysis. Hydrodynamic analysis and finite element based structural analysis are numerically intense stages, and require a substantial amount of computational time and resources. In the present paper, some simplifications are imposed on individual stages to perform the SFA analysis in a practical time scale but not compromising on the underlying theoretical assumptions. Three distinct methods (semi-analytical formulation, 2D strip method, and 3D panel method) have been used to compute the wave-induced loads while the structural responses are obtained using the beam theory based formulations (in case of semi-analytical and 2D strip method) and finite element analysis (in case of 3D panel method). Fatigue damages are calculated using these methods at the selected locations of a bulk carrier and results are compared with each other. It has been shown that the first two methods (semi-analytical and 2D strip based methods) are quick and efficient and can be used in initial design assessment or identifying the fatigue prone locations. The third method is realistic and accurate and can be used in case of a comprehensive assessment of the design.

Three-dimensional pulse response of curved composite sandwich panel with compressible core using non-linear higher-order theory

2020 ◽  
pp. 109963622098008
Author(s):  
Seyed Ali Ahmadi ◽  
Mohammad Hadi Pashaei ◽  
Ramazan-Ali Jafari-Talookolaei
Keyword(s):  
Finite Element ◽  
Dynamic Response ◽  
Sandwich Panel ◽  
Viscoelastic Model ◽  
Three Dimensional ◽  
Higher Order ◽  
Computer Hardware ◽  
Computational Time ◽  
Damping Factor ◽  
Non Linear

In this paper, the dynamic response of cylindrical sandwich panels with compressible core is obtained using the extended non-linear higher-order sandwich panel theory. It is assumed that the sandwich panel has simply supported boundary at all edges and is consisted of orthotropic face sheets and viscoelastic core layer. To describe the mechanical properties of the viscoelastic foam core, the Kelvin-Voigt linear viscoelastic model was applied. Three-dimensional linear equations of motions were used to describe the sandwich panel deformations. The effects of various parameters including the panel span, core and facing thickness, the viscous damping factor, pulse duration, and maximum pressure on the dynamic response of the sandwich cylindrical panel are studied. The results obtained from present method are compared with finite element solutions and those reported in the literature, and consequently, agreement among the results could be observed. The results shown that applied viscoelastic model has a signification effect on the panel response and reduces the magnitude of vibrations. The presented programming code (DQ) needs less computational time and computer hardware capacity and is faster than finite element solution.

Determination of the Optimal Balancing Head Location on Flexible Rotors Using a structural Dynamics Modification Algorithm

1985 ◽  
Vol 199 (1) ◽  
pp. 19-25 ◽  
Author(s):  
Y D Kim ◽  
C W Lee
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Dynamics ◽  
Current Approach ◽  
Optimal Location ◽  
Computational Time ◽  
Rotating Shaft ◽  
Element Analysis ◽  
Flexible Rotors

Bishop (1) proposes an effective way of balancing a flexible rotating shaft using one motorized balancing head. To determine the optimal location of the head and the amount of correction unbalance required, the change in modal properties due to the presence of the balancing head has to be completely examined, which is often laborious and time consuming. In this paper, a simple and effective method to determine the optimal location of the balancing head and the amount of correction unbalance, adopting a structural dynamics modification (SDM) approach, is presented and an example problem is solved. It is shown that the current approach yields results almost as accurate as those obtained by finite element analysis, while computational time and effort are remarkably reduced.

Constitutive Model for Rockfill Materials and Determination of Material Constants

2006 ◽  
Vol 6 (4) ◽  
pp. 226-237 ◽  
Author(s):  
A. Varadarajan ◽  
K. G. Sharma ◽  
S. M. Abbas ◽  
A. K. Dhawan
Keyword(s):  
Constitutive Model ◽  
Material Constants ◽  
Rockfill Materials

The use of static reduction in the finite element solution of two-dimensional frictional contact problems

2013 ◽  
Vol 228 (9) ◽  
pp. 1474-1487 ◽  
Author(s):  
A Thaitirarot ◽  
RC Flicek ◽  
DA Hills ◽  
JR Barber
Keyword(s):  
Finite Element ◽  
Stiffness Matrix ◽  
Frictional Contact ◽  
Contact Problems ◽  
Computational Time ◽  
Friction Laws ◽  
Periodic Loading ◽  
Frictional System ◽  
Well Posed

In this paper, detailed instructions are given for performing static reduction on a finite element description of an elastic contact problem, thus reducing the dimensionality of the problem to the set of contact nodes alone. This significantly reduces the computational time for the solution to evolutionary contact problems and also gives the user greater control over the detailed implementation of the contact and friction laws. The reduced stiffness matrix is also an essential ingredient in the determination of the critical coefficient of friction for the problem to be well posed, and it facilitates the determination of the conditions under which a frictional system may shake down under periodic loading.

Determination of Ultimate Filling Height of Slag Subgrade with FEM Modelling

2012 ◽  
Vol 188 ◽  
pp. 84-89 ◽  
Author(s):  
Bing Gen Zhan ◽  
Yi Dong Ruan ◽  
Ding Han
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Creep Test ◽  
Finite Element Modelling ◽  
Differential Settlement ◽  
Element Modelling ◽  
Filling Height ◽  
Pavement Structures ◽  
Surface Increase

To use slag in high subgrade reasonably and effectively, the filling height limit was investigated. The viscoelasticity parameters of slag in a ascertain graduation were gained by viscoelasticity constitutive model and indoor creep test. The differential settlement values (DSV) of subgrade surface at various filling heights were obtained by the finite element modelling. The research results show that the DSVs on subgrade surface increase with the filling height. According to the effects of DSV on pavement structures, four grades of differential settlement from low to high were divided, the ultimate filling heights of slag were evaluated correspondingly.

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