Linear Stress Analysis Research Articles

Experimental and Numerical Study the Linear Stress Analyses for the Prediction of Fracture Toughness of Ductile Material

The purpose of this paper is to determine a stress intensity factor experimental and numerically in the linear region by using a CT specimen of ductile material with a thickness of 15 mm, a width of 30 mm, and pre-crack 1.3 mm this dimension according to ASTM-E399-12 [1], by pulling the specimen in a 600 kN universal testing machine at a very slow speed rate of 0.5 mm/min. The load is applied until the fracture is accrued, the computer-controlled universal testing machine gives the value of the load and the displacement transducer gives a crack mouth opening displacement. The result showed experimental KI is equal to 75.412 MPa√m, and numerical KI is equal to74.576 MPa√m, this test showed a very slight decrease in FEA stress intensity factor compared to that in an experimental result which means the stress intensity factor, KI remains very close between experimental and numerical with an error percentage of about (1.12 %). The finite element analysis provides the best approximation to true fracture toughness values, and it can be used to acquire close parameters if experimental testing is not possible.

Endocrown Feasibility for Primary Molars: A Finite Element Study.

To study the possibility of using pediatric endocrowns to restore the second primary molar using three-dimensional (3D) finite element analysis. A 3D finite element model was built for a pediatric mandibular molar, starting with laser scanning a naturally extracted tooth. The access cavity had an elliptic shape with 6 mm width, 4 mm height, and 2 mm depth with a wall taper angle of 5 degrees.Two materials (Zr and E-max) were tested for the endocrown and two cementing materials (glass ionomer and resin cement) with 20 to 40 μm thickness. Twelve case studies were reported within this research as the applied load of 330 N was tested with three angulations vertical, oblique at 45 degrees, and laterally. Twelve linear static stress analyses were performed. The resultant stresses and deformations' distribution patterns did not alter much, and values were within the threshold of physiological tolerance. Deformations were negligibly changed with changing endocrown and cement materials. In contrast, endocrown stresses indicated zirconia endocrown would have a long lifetime, while E-max one will have a relatively short lifetime. Analysis results indicated that bone was negligibly affected by changing endocrowns and cementing materials. Both tested endocrown materials can be used safely. Zirconia endocrowns may have a much longer lifetime than E-max.

Parametric linear finite element stress and stability analysis of isotropic and orthotropic self-supporting Miura-ori structures

Sandwich structures with Miura-ori cores have been studied especially in aerospace industry. However, by removing the face sheets one can obtain esthetical, multifunctional, self-supporting structures for various applications, such as packaging. This study focuses on the mechanical performance of planar, self-supporting Miura-ori structures under compressive loads. Through systematic variations of both origami geometry and base material orientation, this study performs linear stress and stability analyses by utilizing the finite element method. The results reveal the effects of the geometric parameters and the material orthotropy on the structural performance, finally resulting in parameter ranges forming a basis for structural design.

Design, Analysis, Control and Manufacturing of a Head Massaging Machine

Nowadays, a lot of people are suffering from unexpected Headaches at odd hours of the day due to their hectic schedule and busy lifestyle. Many devices for massage therapy have already been introduced in the market for the same but none of them are actually worth the price as they fail to deliver the quick necessary relief. For overcoming this problem, we have come up with a new design for head massaging which mainly works on the ideal concept of massage therapy by pressing the optimum pressure points located at the extremes of the forehead. The novelty of this paper lies in the mechanism involved that will help us to achieve the desired output. We will be presenting the complete design, control and manufacturing for the product by a series of simulations which will includes Linear Static Stress analysis for evaluating the strength of the design which can produce the right amount of force, Vibrational/Modal Frequency response for analysing the stability while functioning, Fatigue Test for evaluating the maximum stress the design can bear for a good life and finally comes the Thermal Analysis for evaluating the heat dissipation from the electronics. The Computer Aided Design will be developed on SOLIDWORKS Software and the Finite Element Simulations will be conducted on ANSYS for optimization. Some post simulations will also be conducted such as drop test for evaluating the chances of sudden failure under the circumstances of impact loading. At last there will be a complete manufacturing planning for the entire design along with its DFMA planning.

Stability, Stress and Strain Analysis of Very Slender Pinned Thin-Walled Box Columns according to FEM, Euler and TSTh

In this study, a Finite Element Method (FEM) analysis is presented for the loss of stability in elastic states of very slender pinned without friction box-section thin-walled column axially compressed. From the FEM buckling linear stress analyses are determined the compressing critical forces for 36 cases, presented in tables and as the surface functions in dependence on the slenderness ratio and cross-section. Also are presented graphs obtained from the FEM post-buckling linear stress analysis for the elastic central line, slope, deflection and states of the stresses and strains of the box-section column 20×28×1×2500 mm made of steel, by the assumption that a maximal deflection equals the half of a side dimension. The obtained from the FEM computing function and surface graphs are compared and then discussed with graphs corresponding to Euler’s and Technical Stability Theory (TSTh) results. Finally are compared graphs of the stresses and strains of box-section thin-walled column 20×28×1×2500 obtained from FEM and TSTh, but under compressing critical force determined according to TSTh.

Nonlinear Stress Analysis of Compressed Composite Electrode in Sulfide All-Solid-State Lithium-Ion Battery with X-Ray CT

Sulfide solid electrolytes display favorable characteristics for applications in all-solid-state batteries.Various solid electrolytes have been developed so far, but in order to realize high ionic conductivity, it is necessary to apply pressure to reduce voids between the solid electrolytes[1][2]. This is important when preparing an electrode layer. Particularly in cathode, which is a mixture of hard cathode active materials and soft sulfide solid electrolyte, inhomogeneous stress distribution could be generated in the solid electrolyte in cathode. It is expected that this results in non-uniform ionic conductivity. Therefore, by analyzing stress distribution in cathode, ion transport phenomenon in the solid electrolyte can be clarified, and we can obtain insights for optimum battery design. There are mainly two methods for analyzing the stress distribution in powder mixture. One is Discrete Element Method (DEM), which treats powder particles as independent discontinuous bodies and analyzes interactions between powder particles. With DEM, while detailed interactions between voids and particles can be analyzed, stress analysis inside the particles is difficult. Moreover, the calculation cost is very high. Another is the Finite Element Method (FEM), which is a method that captures powder and voids as a continuous body that is divided into small elements for analysis. Although detailed interaction between voids and particles cannot be analyzed, the advantage of FEM is that all the stresses in each small area can be solved and the calculation cost is small. In previous study, ion transportation simulation in a pseudo cathode with linear FEM stress analysis was conducted [3][4]. The numerical ionic conductivity is almost same as the experimental results, but the results have large error range since the Young's modulus of the solid electrolyte must be constant in linear stress analysis. But in reality, the Young’s modulus of powder is not constant [5]. This is because the voids decrease as the stress increases. When the stress is low, the Young's modulus is small since many voids remain and there are rooms to fill the voids. However, when the stress is high, the Young's modulus is large since the powder will not strain with small amount of voids. For high accuracy numerical simulation with small error range, the Young’s modulus should not be constant and non-linear stress analysis should be conducted for FEM.In this study, to focus on the ionic conduction characteristics in the electrode layer, the cathode active material was replaced with an electrochemically stable ZrO2 to suppress the charge / discharge reactions. The prepared composite material was loaded into a cell with excellent airtightness, and three-dimensional structural measurement and strain measurement were performed by X-ray CT. Then, stress analysis by COMSOL was performed using the three-dimensional structural data obtained by X-ray CT.Figure 1 shows the relationship between Young's modulus and stress of a compressed solid electrolyte. As shown, Young's modulus of solid electrolyte has a strong nonlinearity and increases with stress. Figure 2 shows the stress-strain characteristics obtained from experiment, linear stress analysis, and non-linear stress analysis. Previous studies have shown that the Young's modulus of solid electrolytes is in between 25 MPa and 25 GPa.[5] In this study, we set the lower limit of Young's modulus to 25 MPa and the upper limit to 25 GPa for the error range in linear analysis. In linear analysis, error range is heavily dependent of the Young’s modulus of solid electrolyte. On the other hand, in nonlinear analysis, it is possible to reproduce the strain close to that from the experiment. Figure 3 is a cross-sectional view of the stress distribution in non-linear stress analysis results. In this figure, the stress is normalized by applied pressure. As seen in previous studies, materials with high Young’s modulus acts as pillar in a composite and causes stress concentration. [3].However, the relative stress in the solid electrolyte with applied pressure of 200 MPa is higher than that of 100 MPa. This is a result of reflecting the non-linearity of the solid electrolyte. As shown in Fig.1, the Young's modulus of a solid electrolyte with strong nonlinearity increases with increasing stress. As a result, it is considered that the difference in Young's modulus between ZrO2 and solid electrolyte decreases. And thereby causes the stress concentration on ZrO2 to decrease and causes the relative stress of solid electrolyte to increase. The higher the stress on solid electrolyte, the higher the ionic conductivity. We will also discuss the effect of non-linearity of solid electrolyte on ionic conduction characteristics by conducting electricfield analysis based on stress distribution obtained by non-linear analysis in oral presentation. Figure 1

Pediatric Stainless-Steel Crown Cementation Finite Element Study.

Objective To study the effect of using different cement types under pediatric stainless-steel crown (SSC) around mandibular second primary molar using three-dimensional (3D) finite element analysis. Materials and Methods A 3D finite element model was built for pediatric mandibular molar by laser scanning of natural extracted tooth. Four types of cement (zinc phosphate, glass ionomer, resin-modified glass ionomer, and resin) of 200 μm layers thickness were tested under a stainless-steel crown of 130-μm thickness. Twelve case studies were reported within this research, as the applied load of 330 N was tested with three angulations: vertical, oblique at 45°, and laterally. Results Linear static stress analysis was performed. The resultant stresses and deformations' distribution patterns did not change with cement type, while the values were altered. All deformations and stresses were found within the normal range. Conclusions Analysis results indicated that using stiffer cement material increases tooth structure stresses and reduces crown body stresses and deformations, while bone was nearly insensitive to cement type.

Analysis of stress induced by plasma disruption on vacuum vessel through multi-physics modeling

Abstract The analysis of the stresses induced on the vacuum vessel (VV) of a Tokamak and its internal components by the plasma instabilities, such as plasma disruptions, also following a Vertical Displacement Event (VDE), is one of the major concern in the Tokamak mechanical design. So the availability of a fast simulation tool for evaluating the different design options and also able to perform parametric analysis is highly attractive to define the project requirements and to verify the conceptual design. To respond to this wish, a methodology based on the multi-physics modeling capability offered by the Comsol® software platform was developed. It consists in coupled simulations based on the data sharing between two 2D axisymmetric models, everyone coupled with two corresponding 3D models shifted each other of 10 degrees. In the 2D axisymmetric model of every couple, the magnetic and electric fields generated by the plasma VDE and disruption are calculated imposing the plasma time evolution as input. In the corresponding 3D model only the metallic structures are present and on them the Electric and Magnetic fields are extruded, determining so the induced currents diffusion in the passive conductors. Then the resulting Lorentz’s forces are imposed as body loads on the mechanical structures, so a linear stress analysis can be carried out after the constraints assignment. The same procedure is followed with the second couple of 2D/3D models for check purposes, comparing some proper physical quantities, such as the total induced current flowing on the VV. In this paper the methodology is presented by reporting the simulation of a double null plasma VDE, lasting c.a. 100 ms, followed by a full 5.5 MA plasma current quench in about 40 ms, in a medium size Tokamak intended for experimental research purposes.

Linear wave-induced dynamic structural stress analysis of a 2D semi-flexible closed fish cage

Closed fish cages in the sea are proposed as a new concept in marine aquaculture, replacing the conventional net cages in order to meet ecological challenges related to fish lice and escapes. A closed fish cage can be compared to a floating tank structure with an internal free surface. Several types of closed cages have been suggested, and they are categorised according to structural properties as flexible membrane structures (fabric), semi-flexible structures (glass fibre) and rigid structures (steel or concrete). To be able to develop safe and reliable structures, more knowledge is required on the seakeeping behaviour of closed cages in waves and the structural response to the wave loads. This paper builds on a theory presented in Strand and Faltinsen (2019) on the linear wave loads on a 2D closed flexible fish cage. A modelling error has been found in Strand and Faltinsen (2019), however, all the main conclusions are in hold. The error has been corrected in the model in the present paper. The present paper extends the model to include bending in the structural model to be able to handle semi-flexible structures where bending stiffness is significant. In this paper, the linear theory of a 2D semi-flexible closed fish cage in waves is developed and analysed to investigate the structural response of the semi-flexible closed cage in waves. We have compared a quasi-static analysis with a fully coupled hydroelastic analysis to investigate if it is a valid and conservative assumption to assume that the stresses in the structure can be assumed quasi-static. If a hydroelastic analysis is necessary or not, is dependent on the stiffness of the structure. We have investigated what happens with the stress in the curved beam part of the closed fish cage for increasing and decreasing stiffness relative to a reference composite structure. One stiffer and two softer cases have been analysed. One major concern for the structural stresses in a closed cage is the effect of sloshing. Sloshing is internal wave motion inside the cage and have multiple resonance periods. The results indicate that to use the quasi-static assumption in structural stress calculation is conservative within the given frequency range for all examined stiffnesses and frequencies, except the frequencies very close to the second sloshing frequency. Close to the second sloshing frequency for all the examined stiffnesses, a localised peak can be observed in the coupled hydroelastic results. The second sloshing frequency is a frequency connected to a symmetric sloshing mode. Rigid body motion is not affected at the symmetric sloshing frequency for an assumed rigid structure, and are therefore also not visible in the stress results from the quasi-static analysis. The structural stress in irregular sea was calculated. These results show no indication of increased stress close to the second sloshing frequency. However, this is not a surprising result since the stress peak is very localised in frequency, and the accumulated effect on the stress standard deviation is therefore small.

Linear and Non-Linear Stress Analysis for the Prediction of Fracture Toughness for Brittle and Ductile Material using ASTM E399 and ASTM E1290 By ANSYS Program package

Prediction of fracture toughness value of most the metallic materials is a very important issue to be consider in designing of engineering structural components like pipes, flow tanks and pressure vessel where it can be used in the evaluation of critical crack length that is consider very important factor in non-destructive testing because during inspections of these components, the critical crack length is being compared with the minimum allowable flow size. Fracture toughness value can be predicted by using two different types of experimental tests such as ASTM-E399 (which is used to predict fracture toughness under plane strain condition for brittle materials which undergo to small plastic deformation) and ASTM-E1290 (which is used to predict fracture toughness for ductile materials which undergo to large plastic deformation). These experimental tests utilize specimens such as compact tension specimen CT and three-point bend specimen SENB which must be pre-cracked. However, manufacturing of pre-cracked in metallic structural components before testing is expensive and time-consuming process, thus in the current study, fracture toughness will be predicted by using economized method in both time and cost that is the finite elements method by using ANSYS PROGRAM Where, a three-dimensional model has been designed by using two different types of elements (plane-82) and (solid-95).Firstly, two-dimensional model mesh will be idealized by using element type (plane-82) due to ANSYSY PROGRAM can pick–up singularity for two dimensional model only, but in order to obtain more accurate results, a three dimensional model will be designed by utilizing Sweep Model with restriction with ANSYSY abilities in the treatment of fracture mechanics problems for three dimensional model analysis where the element length must be ranging from 1to4 in all directions. In elastic region, the fracture toughness is been predicted directly from ANSAYS PROGRAM using the specification in ASTM-E-399 for compact tension specimen for practical design problems. But in elastic-plastic region, the fracture toughness is been predicted by using the crack tip opening displacement model (CTOD-Model) using the specification in ASTM-E-1290 for three-point bend specimen for practical design problem. The critical value for crack tip opening displacement will be calculated after extracting load-displacement data from ANSAYS PROGRAM then using these data in (CTOD-Model) which is separated into two components, elastic and plastic, the elastic component has been estimated using Dug Dual-Model, while the plastic component will be estimated using Plastic Hinge-Model. However, the fracture toughness value that has been predicted by finite element method from non –linear elastic analyses and from non –linear elastic-plastic analyses gives excellent results which are very close to the experimental results with error ratio ranging between (10% to 14%).

Discrete adjoint gradient evaluations for linear stress and vibration analysis

This paper presents methods used to perform discrete adjoint gradient evaluations for linear stress and vibration analysis. The methods are implemented within the framework of a discrete adjoint structural solver being developed for multidisciplinary adjoint optimizations of turbomachinery components. The code is differentiated using the algorithmic differentiation tool CoDiPack in tandem with manual treatment of the iterative solvers. Stress analysis leads to a linear system of equations that is typically solved by an iterative solver (e.g. GMRES). To ensure accuracy, the adjoint problem is formulated as a new linear system of equations to be solved. Vibration analysis results in a generalized eigenvalue problem that is also typically solved by an interative solver. The adjoint problem takes out the generalized eigenvalue solve and replaces it by one outer product per eigenfrequency, leading to significantly cheap eigenfrequency gradients for vibration analysis.

Composite Materials Behavior Analyze for Desk, Hull and Board Yacht's Panel

Materials science and composite technology are advancing rapidly, and new composites such as epoxy mixtures including the application of carbon nano tubes are becoming more popular with ever growing concern for high performance marine structures. Indeed, lightness, ease of production, durability and strength enable composites to play a vital role in marine applications. As the Marine sector continues to look at improving efficiency and reducing overall costs, Composite materials will play a huge part in the future of Marine construction. The paper is focused to the static linear simulation of elastic bodies using Solid Works Simulation. Stresses analyses have been developed in the static analyze which provide tools for the linear stress analysis of parts and assemblies loaded by static loads, taking in consideration for the analyze the most stressed part of the bottom, board and desk of the yachts Keywords: Static analyze, stress, composite materials, optimization, marine sector, leisure yachts.

Two bay crack arrest capability evaluation for metallic fuselage

Transport aircraft is a highly complex structure. The aircraft fuselage shell is composed of stressed skin, longitudinal stringers, and circumferential frames. The skin is connected to the stringers and frames mostly by rivets. The fuselage has a number of riveted joints and is subjected to a major loading of differential internal pressurization. When the fuselage is pressurized and depressurized during each take-off and landing cycle of aircraft, the metal skin of fuselage expands and contracts to result in metal fatigue. Due to the presence of a large number of rivet holes, the fuselage skin has a large number of high-stress locations and these are locations of potential crack initiation. The wide-bodied transport aircraft are designed to tolerate large fatigue cracks. This project focuses attention on damage tolerance design of a fuselage structure of transport aircraft. In this project, the stress intensity factor, quantifying the intensity of the stress field around a crack tip for a longitudinal crack under the pressurization load is studied. The objective of this project is to investigate crack initiation, crack growth, fast fracture and crack arrest features in the stiffened panel. The longitudinal crack is initiated from the rivet hole and stress intensity factor is calculated using modified virtual crack closure integral (MVCCI) method at each stage of crack propagation. In order to arrest crack propagation which is the capital importance of tear straps are used, which prevent the further crack propagation. In this project, the linear static stress analysis of the stiffened panel of a fuselage is performed using MSC NASTRAN solver. The pre-processing of the model is done by using MSC PATRAN software.

Composite Materials Behavior Analyze for Desk, Hull and Board Yacht's Panel

Abstract Materials science and composite technology are advancing rapidly, and new composites such as epoxy mixtures including the application of carbon nano tubes are becoming more popular with ever growing concern for high performance marine structures. Indeed, lightness, ease of production, durability and strength enable composites to play a vital role in marine applications. As the Marine sector continues to look at improving efficiency and reducing overall costs, Composite materials will play a huge part in the future of Marine construction. The paper is focused to the static linear simulation of elastic bodies using Solid Works Simulation. Stresses analyses have been developed in the static analyze which provide tools for the linear stress analysis of parts and assemblies loaded by static loads, taking in consideration for the analyze the most stressed part of the bottom, board and desk of the yachts

Classical, higher-order, zig-zag and variable kinematic shell elements for the analysis of composite multilayered structures

Abstract In the present work, a shell finite element with a variable kinematic field based on a new zig-zag power function is proposed for the analysis of laminated shell structures . The kinematic field is written by using an arbitrary number of continuous piecewise polynomial functions. The polynomial expansion order of a generic subdomain is a combination of zig-zag power functions depending on the shell thickness coordinate. As in the classical layer-wise approach, the shell thickness can be divided into a variable number of mathematical subdomains. The expansion order of each subdomain is an input parameter of the analysis. This feature enables the solution to be locally refined over generic regions of the shell thickness by enriching the kinematic field. The advanced finite shell elements with variable kinematics are formulated in the framework of the Carrera Unified Formulation. The finite element arrays are formulated in terms of fundamental nuclei, which are invariants of the theory approximation order and the modelling technique (Equivalent-Single-Layer, Layer-Wise). In this work, the attention is focused on linear static stress analyses of composite laminated shell structures. The governing equations are obtained by applying the Principle of Virtual Displacements, and they are solved using the Finite Element method . Furthermore, the Mixed Interpolated Tensorial Components (MITC) method is employed to contrast the shear locking phenomenon . Several numerical investigations are carried out to validate and demonstrate the accuracy and efficiency of the present shell element.

Static and Vibration Analysis of an Aluminium and Steel Bus Frame

The transport sector is increasing day by day to satisfy the global market requirement. The bus is still the main mode of intercity transportation in Canada. Despite, an essentially unchanged conception, the total weight of the bus has increased by over 25% during the last three decades. To solve this problem, industrialists have moved to the use of light metals in the transportation field. Therefore, use of lightweight materials, such as aluminum is essential to reduce the total weight of bus. In this study, the focus is on the bus frame as it represents 30% of the total weight and it is the most stressed part of the bus. Its life duration is more important compared to that of all other elements. Thus, a study of the static and vibratory behavior would be very decisive. In this article, two types of analysis are carried out. First is the modal analysis to determine the natural frequencies and the mode shapes using a developed dynamic model of the bus. Because if any of the excitation frequencies coincides with the natural frequencies of the bus frame, then resonance phenomenon occurs. This may lead to excessive deflection, high stress concentration, fatigue of the structure and vehicle discomfort. In this case, the results analysis shows that the natural frequencies are not affected by the change of material. The second type of analysis is the linear static stress analysis to consider the stress distribution and deformation frame pattern under static loads numerically. For the numerical method, the frame is designed using SolidWorks and the analysis is made using Ansys WorkBench. The maximum Von Mises stress obtained for the static loading is in the same order for the three chassis frames studied. But in the case of the aluminium frame, the weight of 764 kg was reduced.

Stress Analysis of Composite Materials Used for Yacht Production Through Solid Work Simulation

In recent years, considerable progress has been made in understanding the characteristic of composite materials and their tailored structures in the marine environment. Processing and production sectors also have received more attention resulting in the potential for the construction of complex, large assemblies capable of withstanding heavy loads. However, the key challenges involved in employing composites for marine applications include the need for optimization of capital expenditure and operating costs of boats, ships and other marine artifact’s constructed using composites. Materials science and composite technology are advancing rapidly, and new composites such as epoxy mixtures including the application of carbon nano tubes are becoming more popular with ever growing concern for high performance marine structures. Indeed, lightness, ease of production, durability and strength enable composites to play a vital role in marine applications. As the Marine sector continues to look at improving efficiency and reducing overall costs, Composite materials will play a huge part in the future of Marine construction. The paper is focused to the static linear simulation of elastic bodies using Solid Works Simulation. Stresses analyses have been developed in the static analyze which provide tools for the linear stress analysis of parts and assemblies loaded by static loads, taking in consideration for the analyze the most stressed part of the bottom, board and desk of the yachts

熱応力解析理論に基づくショットピーニング面の残留応力深さ分布推定

In the shot peening process, the residual stress on the shot-peened surface and its distribution under the surface are important evaluation items for the high value-added surface creation. In this paper, it was proposed that the residual stress distribution under the shot-peened surface for a thin plate was non-destructively estimated from the measured value of residual stress on the surface and that of the arc height, by applying the theory of linear thermal stress analysis for a thin plate. The analyzed residual stress profile showed good agreement with that of the experimental results obtained from the surface removal by electro-polishing. From the results of analysis, it was found that the depth of compressive residual stress (the depth which changes from the compressive stress to the tensile stress), the residual stress at the depth of the inherent strain and the residual stress on the opposite surface to the shot-peened surface characterizing the profile of residual stress distribution had a relationship with the ratio of a thickness of plate to an inherent strain depth.

The impact of geometric non-linearities on the fatigue analysis of trailing edge bond lines in wind turbine rotor blades

The accurate prediction of stress histories for the fatigue analysis is of utmost importance for the design process of wind turbine rotor blades. As detailed, transient, and geometrically non-linear three-dimensional finite element analyses are computationally weigh too expensive, it is commonly regarded sufficient to calculate the stresses with a geometrically linear analysis and superimpose different stress states in order to obtain the complete stress histories.In order to quantify the error from geometrically linear simulations for the calculation of stress histories and to verify the practical applicability of the superposition principal in fatigue analyses, this paper studies the influence of geometric non-linearity in the example of a trailing edge bond line, as this subcomponent suffers from high strains in span-wise direction. The blade under consideration is that of the IWES IWT-7.5-164 reference wind turbine. From turbine simulations the highest edgewise loading scenario from the fatigue load cases is used as the reference. A 3D finite element model of the blade is created and the bond line fatigue assessment is performed according to the GL certification guidelines in its 2010 edition, and in comparison to the latest DNV GL standard from end of 2015.The results show a significant difference between the geometrically linear and non-linear stress analyses when the bending moments are approximated via a corresponding external loading, especially in case of the 2010 GL certification guidelines. This finding emphasizes the demand to reconsider the application of the superposition principal in fatigue analyses of modern flexible rotor blades, where geometrical nonlinearities become significant. In addition, a new load application methodology is introduced that reduces the geometrically non-linear behaviour of the blade in the finite element analysis.

Design and Analysis of a Slanted Strapon Nose Cone (SSNC) of an Advanced Launch Vehicle

Launch vehicles are used to transport satellite or space craft into space. To minimize the aero acoustic and aerodynamic loads, the nose cones are slanted to an angle on free side and straight on the interference side in advanced launch vehicles. Objective of this paper is to design and analyze nose cone region of a typical launch vehicle using integrally stiffened panel concept, made of aluminium alloy material. The first part of the present work is to make the optimum design of a slanted SNC structure and the second is to verify the detailed design through finite element method. Linear static stress analysis, buckling analysis and free vibration analysis of the finalized design is carried out using finite element analysis software NISA. Aerodynamic pressure distribution over the surface is generated using computational fluid dynamic analysis code PARAS 3D. Static, dynamic and buckling analysis results are presented here. Optimum design based on the integrally stiffened panel construction is compared with the design by combination of stiffened skin with bulkheads and isogrid type of construction. 0 on the free side and straight on the interference side are selected based on various studies. The change in pressure rise on core will be more for slanted nose cone. But the zone of influence is more in regular nose cones. Appreciable weight savings are possible through the integral section design which also develops high resistance to buckling loads. This method improved performance through smoother exterior surfaces by reduction in number of attachments and non- buckling characteristics of skin. Design of structural components has to meet specific requirements which influence the complexity of its structure and the materials used in its construction. Aluminium, blended with small quantities of other metals is used on most types of aircraft because it is lightweight and strong. AA2014 aluminium alloy is an aluminium-based alloy often used in the aerospace industry.(1) It is easily machined in certain tempers, and among the strongest available aluminium alloys, as well as having high hardness. II. Slanted Strapon Nose Cone Configuration The non-dimensional parameters of the SSNC selected for the present study is described here. The base diameter D is selected as reference dimension for this configuration. Aft End (AE) ring is a cylindrical structure with inclined top surface and tangential to the conical section. Nose cone is a truncated cone with non-parallel top and bottom surfaces also tangential to the nose cap and AE ring at all interfacing location. SSNC having an overall height of 1.68D and fore end of the cone is covered by a spherical cap of radius 0.23D. The AE ring has a height of 0.25D at straight side and 0.36D on the other side due to the slanted configuration as shown in Fig. 1(a).