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.

scholarly journals Image-based semi-multiscale finite element analysis using elastic subdomain homogenization

Meccanica ◽  
2021 ◽  
Author(s):  
J. Jansson ◽  
K. Salomonsson ◽  
J. Olofsson
Keyword(s):  
Finite Element ◽  
Analytical Method ◽  
Effective Properties ◽  
Reference Model ◽  
Computational Time ◽  
Component Level ◽  
Element Analysis ◽  
Model Fidelity ◽  
Multiscale Finite Element ◽  
Anisotropic Elastic

AbstractIn this paper we present a semi-multiscale methodology, where a micrograph is split into multiple independent numerical model subdomains. The purpose of this approach is to enable a controlled reduction in model fidelity at the microscale, while providing more detailed material data for component level- or more advanced finite element models. The effective anisotropic elastic properties of each subdomain are computed using periodic boundary conditions, and are subsequently mapped back to a reduced mesh of the original micrograph. Alternatively, effective isotropic properties are generated using a semi-analytical method, based on averaged Hashin–Shtrikman bounds with fractions determined via pixel summation. The chosen discretization strategy (pixelwise or partially smoothed) is shown to introduce an uncertainty in effective properties lower than 2% for the edge-case of a finite plate containing a circular hole. The methodology is applied to a aluminium alloy micrograph. It is shown that the number of elements in the aluminium model can be reduced by $$99.89\%$$ 99.89 % while not deviating from the reference model effective material properties by more than $$0.65\%$$ 0.65 % , while also retaining some of the characteristics of the stress-field. The computational time of the semi-analytical method is shown to be several orders of magnitude lower than the numerical one.

scholarly journals Practical Prediction of the Boil-Off Rate of Independent-Type Storage Tanks

2021 ◽  
Vol 9 (1) ◽  
pp. 36
Author(s):  
Dong-Ha Lee ◽  
Seung-Joo Cha ◽  
Jeong-Dae Kim ◽  
Jeong-Hyeon Kim ◽  
Seul-Kee Kim ◽  
...  
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Environmentally Friendly ◽  
Fuel Tank ◽  
Computational Time ◽  
Insulation Material ◽  
Element Analysis ◽  
Vertical Temperature Profile ◽  
Space Efficiency ◽  
Key Aspects

Because environmentally-friendly fuels such as natural gas and hydrogen are primarily stored in the form of cryogenic liquids to enable efficient transportation, the demand for cryogenic fuel (LNG, LH) ships has been increasing as the primary carriers of environmentally-friendly fuels. In such ships, insulation systems must be used to prevent heat inflow to the tank to suppress the generation of boil-off gas (BOG). The presence of BOG can lead to an increased internal pressure, and thus, its control and prediction are key aspects in the design of fuel tanks. In this regard, although the thermal analysis of the phase change through a finite element analysis requires less computational time than that implemented through computational fluid dynamics, the former is relatively more error-prone. Therefore, in this study, a cryogenic fuel tank to be incorporated in ships was established, and the boil-off rate (BOR), measured considering liquid nitrogen, was compared with that obtained using the finite element method. Insulation material with a cubic structure was applied to the cylindrical tank to increase the insulation performance and space efficiency. To predict the BOR through finite element analysis, the effective thermal conductivity was calculated through an empirical correlation and applied to the designed fuel tank. The calculation was predicted to within 1% of the minimum error, and the internal fluid behavior was evaluated by analyzing the vertical temperature profile according to the filling ratio.

Structural Analysis of Centrifugal Fan Impeller Using CATIA Software

2015 ◽  
Vol 809-810 ◽  
pp. 859-864
Author(s):  
Dănuţ Zahariea
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Structural Analysis ◽  
Design Methods ◽  
Constant Thickness ◽  
Blade Design ◽  
Centrifugal Fan ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Modes Of Vibration

In this paper, the finite element analysis for stress/deformation/modes of vibration for the centrifugal fan impeller with constant thickness backward-curved blades using CATIA software will be presented. The principal steps of the finite element analysis procedure using CATIA/Generative Structural Analysis environment will be presented: creating the 3D model; configuring the mesh; applying the restraints; applying the loads; running the numerical static analysis and the numerical frequency analysis; interpreting the results and observing the modes of vibration correlating with the impeller mode shape. This procedure will be used for 4 different centrifugal fan impellers according with the 4 blade design methods and the results will be comparatively analyzed. For each design method, two materials will be used: steel with density of 7860 kg/m3 and aluminium with density of 2710 kg/m3. Two important results have been obtained after the structural analysis: under the working conditions considered for the analysis, all 4 blade design methods leads to impellers with very good mechanical behaviour; any frequency of the main modes of vibrations for all blade design methods and for both materials is not in phase with the impeller speed, thus the possibility of resonance being eliminated.

Strength-based design of a sunflower stalk cutter machine design using finite element analysis and experimental validation

2021 ◽  
pp. 095440622110597
Author(s):  
Gürkan İrsel
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Stress Analysis ◽  
Strain Gage ◽  
Experimental Validation ◽  
Experimental Studies ◽  
Fatigue Analysis ◽  
Structural Stress ◽  
Element Analysis ◽  
Strength Based

In this study, the total algorithm of the strength-based design of the system for mass production has been developed. The proposed algorithm, which includes numerical, analytical, and experimental studies, was implemented through a case study on the strength-based structural design and fatigue analysis of a tractor-mounted sunflower stalk cutting machine (SSCM). The proposed algorithm consists of a systematic engineering approach, material selection and testing, design of the mass criteria suitability, structural stress analysis, computer-aided engineering (CAE), prototype production, experimental validation studies, fatigue calculation based on an FE model and experimental studies (CAE-based fatigue analysis), and an optimization process aimed at minimum weight. Approximately 85% of the system was designed using standard commercially available cross-section beams and elements using the proposed algorithm. The prototype was produced, and an HBM data acquisition system was used to collect the strain gage output. The prototype produced was successful in terms of functionality. Two- and three-dimensional mixed models were used in the structural analysis solution. The structural stress analysis and experimental results with a strain gage were 94.48% compatible in this study. It was determined using nCode DesignLife software that fatigue damage did not occur in the system using the finite element analysis (FEA) and experimental data. The SSCM design adopted a multi-objective genetic algorithm (MOGA) methodology for optimization with ANSYS. With the optimization solved from 422 iterations, a maximum stress value of 57.65 MPa was determined, and a 97.72 kg material was saved compared to the prototype. This study provides a useful methodology for experimental and advanced CAE techniques, especially for further study on complex stress, strain, and fatigue analysis of new systematic designs desired to have an optimum weight to strength ratio.

scholarly journals Fatigue life prediction of upper arm suspension using strain life approach

2019 ◽  
Vol 17 (1) ◽  
pp. 25-40 ◽  
Author(s):  
Hafida Kahoul ◽  
Samira Belhour ◽  
Ahmed Bellaouar ◽  
Jean Paul Dron
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Aluminium Alloys ◽  
Fatigue Analysis ◽  
Vertical Force ◽  
Upper Arm ◽  
Element Analysis ◽  
Content Type ◽  
Critical Location

Purpose This paper aims to present the fatigue life behaviour of upper arm suspension. The main objectives are to predict the fatigue life of the component and to identify the critical location. In this analysis, three aluminium alloys were used for the suspension, and their fatigue life was compared to select the suitable material for the suspension arm. Design/methodology/approach CAD model was prepared using Solid Works software, and finite element analysis was done using ANSYS 14.0 software by importing the Parasolid file to ANSYS. The model is subjected to loading and boundary conditions; the authors consider a vertical force with constant amplitude applied at the bushing that connected to the tire, the others two bushing that connected to the body of the car are constraint. Tetrahedral elements given enhanced results as compared to other types of elements; therefore, the elements (TET 10) are used. The maximum principal stress was considered in the linear static analysis, and fatigue analysis was done using strain life approach. Findings Life and damage are evaluated and the critical location was considered at node 63,754. From the fatigue analysis, aluminium alloys 7175-T73 (Al 90%-Zn 5.6%-Mg 2.5% -… …) and 2014-T6 (Al 93.5%-Cu 4.4%-Mg 0.5%… …) present a similar behaviour as compared to 6061-T6 (Al 97.9%-Mg 1.0%-Si 0.6%… … .); in this case of study, these lather are considered to be the materials of choice to manufacture the suspension arms; but 7175-T73 aluminium alloys remain the material with a better resistance to fatigue. Originality/value By the finite element analysis method and assistance of ANSYS software, it is able to analyse the different car components from varied aspects such as fatigue, and consequently save time and cost. For further research, the experimental works under controlled laboratory conditions should be done to determine the validation of the result from the software analysis.

scholarly journals Finite Element Analysis Based Structural Analysis of Stacked Heat Exchanger

2014 ◽  
Vol 11 (4) ◽  
pp. 65-69
Author(s):  
Patil Tushar Vishwas ◽  
◽  
Supale Jayant P ◽  
Vinaay Patil
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Heat Exchanger ◽  
Structural Analysis ◽  
Element Analysis

scholarly journals Failure Analysis of fractured Fixing Bolts of a Mobile Elevating Work Platform using Finite Element Methods

2019 ◽  
Author(s):  
DongHoon Choi ◽  
Jae-Hoon Kim
Keyword(s):  
Finite Element ◽  
Chemical Composition ◽  
Chemical Analysis ◽  
Failure Analysis ◽  
Visual Inspection ◽  
Standard Procedure ◽  
Fatigue Analysis ◽  
Certification Authority ◽  
Element Analysis ◽  
Safety Certification

Mobile elevating work platforms (MEWPs) consist of a work platform, extending structure, and chassis, and are used to move persons to working positions. MEWPs are useful but are composed of pieces of equipment, and accidents do occur owing to equipment defects. Among these defects, accidents caused by the fracture of bolts fixed to the extension structure and swing system are increasing. This paper presents a failure analysis of the fixing bolts of MEWP. Standard procedure for failure analysis was employed in this investigation. Visual inspection, chemical analysis, tensile strength measurement, and finite element analysis (FEA) were used to analyze the failure of the fixing bolts. Using this failure analysis approach, we found the root cause of failure and proposed a means for solving this type of failure in the future. First, the chemical composition of the fixing bolt is obtained by a spectroscopy chemical analysis method, which determined that the chemical composition matched the required standard. The tensile test showed that the tensile and yield strengths were within the required capacity. The stress analysis was carried out at five different boom angles, and it was determined that the fixing bolt of MEWP can withstand the loads at all the boom angles. The outcomes of the fatigue analysis revealed that the fixing bolt fails before reaching the design requirements. The results of the fatigue analysis showed primarily that the failure of the fixing bolt was due to fatigue. A visual inspection of the fractured section of the fixing bolt also confirmed the fatigue failure. We propose a method to prevent failure of the fixing bolt of the MEWP from four different standpoints: the manufacturer, safety certification authority, safety inspection agency, and owner.

Formulation of Three-Dimensional Green’s Function and its Application to Fatigue Life Evaluation of Pressurizer

2006 ◽  
Vol 324-325 ◽  
pp. 387-390
Author(s):  
Yoon Suk Chang ◽  
Shin Beom Choi ◽  
Jae Boong Choi ◽  
Young Jin Kim ◽  
Myung Jo Jhung ◽  
...  
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Green’S Function ◽  
Green's Function ◽  
Three Dimensional ◽  
Stress Transfer ◽  
Life Assessment ◽  
Element Analysis ◽  
Fatigue Evaluation ◽  
Effective Assessment

Major nuclear components have been designed by conservative codes to prevent unanticipated fatigue failure. However, more realistic and effective assessment is necessary in proof of continued operation beyond the design life. In the present paper, three-dimensional stress and fatigue evaluation is carried out for pressurizer employing complex full geometry itself instead of conventional discrete subcomponents. For this purpose, temperature and mechanical stress transfer Green’s functions are derived from finite element analyses and applied to critical locations of pressurizer. In accordance with comparison of resulting stresses obtained from the Green’s function and detailed finite element analysis, suitability of the specific Green’s function is investigated. Finally, prototype of fatigue life assessment results is provided along with relevant ongoing activities.

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