Improved Analytical Model for Bolted Joint Evaluation in Gas Turbines

2012 ◽  
Author(s):  
H. S. Prasanna Kumar ◽  
M. M. Mayuram ◽  
K. S. Raghavan
Keyword(s):  
Analytical Model ◽  
Gas Turbines ◽  
Bolted Joints ◽  
Analytical Models ◽  
High Fidelity ◽  
Fe Model ◽  
Operating Load ◽  
Bolt Stress ◽  
The Right ◽  
Analytical Approaches

Modern day gas turbines are very complex in construction consisting of a large number of smaller components connected and kept together by means of bolted joints. These joints operate at high temperatures, pressures and speeds. It is essential that the structural behavior of all the joints be assessed to address issues such as fatigue, creep and flange opening. During the preliminary design and concept optimization stage it is prudent to use simple analytical approaches rather than full fledged finite element simulation models. A number of analytical models are available in literature. Prominent among them are analytical model for “Flat Faces Flanges with Metal-to-Metal Contact beyond the Bolt Circle” by Schneider, which later become standard in ASME code and more recent one is by Galai and Bouzid that uses annular plate theory and thin cylinder theory in conjunction to simulate flange. However such analytical models do not account for all the operating parameters and it is essential to assess their adequacy. The main purpose of the proposed paper is to carry out critical assessment of the simpler analytical approaches and document the findings. The purpose is also to refine the approaches so that the shortcomings are addressed. To this end a 3D high fidelity finite element model including flanges, bolt and nut along with threads is developed simulating bolted joints in gas turbine cases and analyzed for different preload and external operating load conditions like pressure and axial blow off loads. The model is also analyzed for different geometric configuration by varying flange thickness, height and bolt spacing ratio. Different analytical approaches for fastener and member stiffness calculation are evaluated and identified the right combination for the complete model. Existing analytical model for flange opening and bolt stress is then updated by including the right stiffness models. The updated analytical model is compared with high fidelity FE model for different geometry configurations. Results show that the bolt stress variation between the updated analytical model and 3D FE model is around 10% as against 20% in the existing analytical model. Improved analytical method also provides good agreement with the 3D FE results for external loads up to about 60% of the bolt preload, which is well above the normal operating load.

Analytical Solution for the Stresses Arising in +/− Angle Ply Belts of Radial Tires

2008 ◽  
Vol 36 (4) ◽  
pp. 244-274 ◽  
Author(s):  
R. D. McGinty ◽  
T. B. Rhyne ◽  
S. M. Cron
Keyword(s):  
Analytical Solution ◽  
Analytical Model ◽  
Design Space ◽  
Analytical Description ◽  
Analytical Models ◽  
Shear Stresses ◽  
Finite Width ◽  
Fe Model ◽  
Poisson Effect ◽  
Insight Into

Abstract Stresses arising in the belts of radial ply tires, particularly those at the belt edge, are known to be critical to tire durability. Belt edge stresses are commonly calculated using finite element (FE) methods that provide estimates of the levels but do not necessarily give significant insight into the underlying mechanics. In contrast, analytical models can provide physical insight into the mechanisms affecting tire durability but are currently incomplete due to the challenges faced in obtaining closed-form mathematical solutions. Nevertheless, analytical solutions remain important to tire design and development because they can expose the entire design space, show the mathematical relationships between the variables, and allow rapid parameter studies. This work develops an analytical description of the belt deformations and stresses, particularly at the belt edge. The formulation captures all the first-order mechanics pertinent to finite width, antisymmetric +/− angle belt packages present in radial tires. It incorporates interply shear stresses already recognized in the literature and adds to that a new mechanism controlling the interaction of the plies via a Poisson effect. The analytical model is validated by comparison to FE simulations and is also contrasted with a classical analytical model in the literature. The design space for the belt composite is then explored by parameter variation. Finally, since all these solutions depend on homogenization of the belt layers, the analytical solution is compared to a FE model of discrete cables embedded in rubber to explore the accuracy of the homogenization step.

Finite Element Study of Double-Gasket Bolted Joint Connection for Different Gaskets and Bolt Torques

2017 ◽  
Author(s):  
Reza Ghafouri-Azar ◽  
Rosha Banan ◽  
Miodrag (Mike) Stojakovic
Keyword(s):  
Finite Element ◽  
Bolted Joints ◽  
Analysis Tool ◽  
Fe Model ◽  
Fe Modeling ◽  
Bolted Joint ◽  
Modeling And Analysis ◽  
Joint Connection ◽  
Size Type ◽  
The Right

In order to understand the behavior of bolted joints and select a right size, type and gasket load combination, a detailed analysis tool is very helpful. However, the modeling and analysis of a bolted joint connection is a complicated, complex process; particularly if multiple parts are considered in the Finite Element (FE) modeling. Analysis results are often sensitive to bolt pre-torque, gasket type, gasket thickness and other challenges of Finite Element (FE) modeling. In addition, often credible and reliable gasket deflection-load data are not readily available. The bolted joint under study was a double-gasket joint with inner gasket leakoff. The joint has leaked on several occasions, sometimes after several years of service due to warmup/cooldown cycling and sometimes immediately after installation and pressurization. A 3-D FE model was developed for assembly of tubesheet, bolt, two inner and outer gaskets, and vessel cover. Different cases were studied by changing gasket load-deflections for different gasket materials, gasket thicknesses and bolt loads. The outcome of the analyses was used to predict the behavior of bolted joints and understand the root cause of leakage. The results provided guidance for choosing the right combination of bolt pre-torque and gasket type.

Representation of bolted joints in a structure using finite element modelling and model updating

2020 ◽  
Vol 14 (3) ◽  
pp. 7141-7151 ◽  
Author(s):  
R. Omar ◽  
M. N. Abdul Rani ◽  
M. A. Yunus
Keyword(s):  
Finite Element ◽  
Dynamic Behaviour ◽  
Model Updating ◽  
Complex Structure ◽  
Bolted Joints ◽  
Model Parameters ◽  
Fe Model ◽  
Bolted Joint ◽  
Fe Modelling ◽  
Joint Structure

Efficient and accurate finite element (FE) modelling of bolted joints is essential for increasing confidence in the investigation of structural vibrations. However, modelling of bolted joints for the investigation is often found to be very challenging. This paper proposes an appropriate FE representation of bolted joints for the prediction of the dynamic behaviour of a bolted joint structure. Two different FE models of the bolted joint structure with two different FE element connectors, which are CBEAM and CBUSH, representing the bolted joints are developed. Modal updating is used to correlate the two FE models with the experimental model. The dynamic behaviour of the two FE models is compared with experimental modal analysis to evaluate and determine the most appropriate FE model of the bolted joint structure. The comparison reveals that the CBUSH element connectors based FE model has a greater capability in representing the bolted joints with 86 percent accuracy and greater efficiency in updating the model parameters. The proposed modelling technique will be useful in the modelling of a complex structure with a large number of bolted joints.

A novel model of Z-pin insertion in prepreg based on fracture mechanics

2021 ◽  
pp. 095440542110144
Author(s):  
Guobiao Ji ◽  
Liang Cheng ◽  
Shaohua Fei ◽  
Jiangxiong Li ◽  
Yinglin Ke
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Analytical Model ◽  
Model Parameters ◽  
Force Model ◽  
Fe Model ◽  
Cohesive Elements ◽  
Fe Method ◽  
Insertion Force ◽  
Mechanics Model

Through-thickness reinforcement is a promising solution to the problem of delamination susceptibility in laminated composites. Modeling Z-pin–prepreg interaction is essential for accurate robotics-assisted Z-pin insertion. In this paper, a novel Z-pin insertion force model combining the classical cohesive finite element (FE) method with a dynamic analytical fracture mechanics model is proposed. The velocity-dependent cohesive elements, in which the fracture toughness is provided by the analytical model, are implemented in Z-pin insertion FE model to predict the crack initiation and propagation. Then Z-pin insertion experiments are performed on prepreg sample with metallic Z-pins at different velocities to identify the analytical model parameters and validate the simulation predictions offered by the model. Dynamics of Z-pin interaction with inhomogeneous prepreg is described and the effects of insertion velocity on prepreg contact force are studied. Results show that the force model agrees well with experiments and the fracture toughness rises with the increasing Z-pin insertion velocity.

A two-stage design optimization framework for multifield origami-inspired structures

2021 ◽  
pp. 1045389X2110116
Author(s):  
Wei Zhang ◽  
Saad Ahmed ◽  
Jonathan Hong ◽  
Zoubeida Ounaies ◽  
Mary Frecker
Keyword(s):  
Case Studies ◽  
Computing Time ◽  
Computational Cost ◽  
High Fidelity ◽  
Fe Model ◽  
Two Stage ◽  
Baseline Design ◽  
Optimization Framework ◽  
Highly Nonlinear ◽  
Stage 1

Different types of active materials have been used to actuate origami-inspired self-folding structures. To model the highly nonlinear deformation and material responses, as well as the coupled field equations and boundary conditions of such structures, high-fidelity models such as finite element (FE) models are needed but usually computationally expensive, which makes optimization intractable. In this paper, a computationally efficient two-stage optimization framework is developed as a systematic method for the multi-objective designs of such multifield self-folding structures where the deformations are concentrated in crease-like areas, active and passive materials are assumed to behave linearly, and low- and high-fidelity models of the structures can be developed. In Stage 1, low-fidelity models are used to determine the topology of the structure. At the end of Stage 1, a distance measure [Formula: see text] is applied as the metric to determine the best design, which then serves as the baseline design in Stage 2. In Stage 2, designs are further optimized from the baseline design with greatly reduced computing time compared to a full FEA-based topology optimization. The design framework is first described in a general formulation. To demonstrate its efficacy, this framework is implemented in two case studies, namely, a three-finger soft gripper actuated using a PVDF-based terpolymer, and a 3D multifield example actuated using both the terpolymer and a magneto-active elastomer, where the key steps are elaborated in detail, including the variable filter, metrics to select the best design, determination of design domains, and material conversion methods from low- to high-fidelity models. In this paper, analytical models and rigid body dynamic models are developed as the low-fidelity models for the terpolymer- and MAE-based actuations, respectively, and the FE model of the MAE-based actuation is generalized from previous work. Additional generalizable techniques to further reduce the computational cost are elaborated. As a result, designs with better overall performance than the baseline design were achieved at the end of Stage 2 with computing times of 15 days for the gripper and 9 days for the multifield example, which would rather be over 3 and 2 months for full FEA-based optimizations, respectively. Tradeoffs between the competing design objectives were achieved. In both case studies, the efficacy and computational efficiency of the two-stage optimization framework are successfully demonstrated.

scholarly journals Novel Structure and Thermal Design and Analysis for CubeSats in Formation Flying

Aerospace ◽  
2021 ◽  
Vol 8 (6) ◽  
pp. 150
Author(s):  
Yeon-Kyu Park ◽  
Geuk-Nam Kim ◽  
Sang-Young Park
Keyword(s):  
Analytical Model ◽  
Formation Flying ◽  
Thermal Environment ◽  
Thermal Analyses ◽  
Thermal Design ◽  
Analytical Models ◽  
Test Results ◽  
Solar Panels ◽  
Novel Structure ◽  
Micro Propulsion

The CANYVAL-C (CubeSat Astronomy by NASA and Yonsei using a virtual telescope alignment for coronagraph) is a space science demonstration mission that involves taking several images of the solar corona with two CubeSats—1U CubeSat (Timon) and 2U CubeSat (Pumbaa)—in formation flying. In this study, we developed and evaluated structural and thermal designs of the CubeSats Timon and Pumbaa through finite element analyses, considering the nonlinearity effects of the nylon wire of the deployable solar panels installed in Pumbaa. On-orbit thermal analyses were performed with an accurate analytical model for a visible camera on Timon and a micro propulsion system on Pumbaa, which has a narrow operating temperature range. Finally, the analytical models were correlated for enhancing the reliability of the numerical analysis. The test results indicated that the CubeSats are structurally safe with respect to the launch environment and can activate each component under the space thermal environment. The natural frequency of the nylon wire for the deployable solar panels was found to increase significantly as the wire was tightened strongly. The conditions of the thermal vacuum and cycling testing were implemented in the thermal analytical model, which reduced the differences between the analysis and testing.

The effects of geometric offsets on the dynamic responses of a Scott—Russell amplifying mechanism with flexible hinges

2009 ◽  
Vol 223 (10) ◽  
pp. 2413-2423 ◽  
Author(s):  
C-M Chen ◽  
R-F Fung
Keyword(s):  
Numerical Simulations ◽  
Analytical Model ◽  
Dynamic Responses ◽  
Analytical Models ◽  
Dynamic Equations ◽  
Magnification Factor ◽  
Flexure Hinges ◽  
Magnification Factors ◽  
Straight Line ◽  
Deviation Factor

The dynamic equations of a micro-positioning Scott—Russell (SR) mechanism associated with two flexible hinges and an offset are developed to calculate output responses. Both rigid and flexible hinges are considered to explore the results. The main features in the kinematics of the SR mechanism are its displacement amplification and straight-line motion, which are widely needed in practical industries. The manufacturing inaccuracy of the SR mechanism definitely causes geometric offsets of flexure hinges, and affects displacement amplification and straight-line output motion. Analytical models based on kinematics and Hamilton's principle are derived to explore the variation of linearity ratio, magnification factor, and deviation factor due to various offsets and link lengths. From numerical simulations for the SR mechanism with various offsets of flexible hinges in the conditions of different link lengths, it is found that offsets of flexure hinges obviously affect the amplifying factor and linearity ratio, and appear to dominate the changes of magnification factors. Moreover, an analytical model is also used to predict magnification factors due to various offsets. Finally, some conclusions concerning the effects of offset on the performance of the SR mechanism are drawn.

A New Approach for Determining Joint Stiffness of Bolted Joints

2014 ◽  
Vol 670-671 ◽  
pp. 1041-1044 ◽  
Author(s):  
Xi Wang Wang ◽  
Xiao Yang Li ◽  
Lin Lin Zhang ◽  
Xiao Guang Wang
Keyword(s):  
Accurate Determination ◽  
Joint Stiffness ◽  
Fatigue Loading ◽  
Bolted Joints ◽  
Analytical Models ◽  
Bolted Connection ◽  
New Approach ◽  
Axisymmetric Model ◽  
Force Equilibrium

Joint member stiffness in a bolted connection directly influence the safety of a design in regard to both static and fatigue loading as well as in the prevention of separation in the connection. Thus, the accurate determination of the stiffness is of extreme importance to predict the behavior of bolted assemblies. In this paper, An analytical 3D axisymmetric model of bolted joints is proposed to obtain the joint stiffness of Bolted Joints. Considering many different analytical models have been proposed to calculate the joint stiffness, the expression based force equilibrium can be a easy way to choose the best expression for the joint stiffness as a judgment criteria.

scholarly journals Design and Control of a Magnetically Suspended Ceiling Actuator with Infinite Planar Stroke

2013 ◽  
Vol 416-417 ◽  
pp. 492-502 ◽  
Author(s):  
T.T. Overboom ◽  
J.P.C. Smeets ◽  
J.W. Jansen ◽  
E.A. Lomonova
Keyword(s):  
Permanent Magnet ◽  
Analytical Model ◽  
Normal Force ◽  
Tracking Error ◽  
Fe Model ◽  
Optimized Design ◽  
Three Phase ◽  
Linear Actuators ◽  
And Control ◽  
Infinite Planar

This paper presents the design and control of a magnetically suspended ceiling actuator which combines four iron-cored linear actuators and a checkerboard permanent magnet array for an infinite planar stroke. When the actuators are rotated with respect to the PM array, it is shown that the thrust and normal force produced by the three-phase linear actuators can be controlled by applying Park's transformation. The design of the iron-cored linear actuators is optimized for minimum losses when the translator inside the ceiling actuator and a payload are accelerated in the xy-plane. The optimization is performed using an analytical model is. Simulations of the optimized design with a 3D FE-model, show a maximum tracking error of 1 μm and rotations of 30 μrad when the translator is moved and controlled in 6 DOF.

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