Study on the Stiffness Loss and the Dynamic Influence on Rotor System of the Bolted Flange Joint

2014 ◽  
Author(s):  
Cun Wang ◽  
Dayi Zhang ◽  
Xiaobin Zhu ◽  
Jie Hong
Keyword(s):  
Finite Element ◽  
Mechanical Characteristics ◽  
Dynamic Properties ◽  
Bending Stiffness ◽  
Rotor System ◽  
Structural Parameter ◽  
Beam Model ◽  
Flange Joint ◽  
Bolted Flange ◽  
Stiffness Loss

The bolted flange joint is a kind of widely used joint structure in the rotor system. Its discontinuous mechanical characteristics result from the existing of the contact surface, which will slide and deform when the spool deforms. As a consequence, the joint’s stiffness is always smaller than that of fixed configuration, which affects rotor’s stiffness distribution and the rotor’s dynamics further. The objective of this study is to investigate the mechanical characteristics of the bolted flange joint, the affecting factors and the influence on rotor’s dynamics. According to the characteristics of structure and mechanical state, using the existing equivalent axial spring-bending beam model to describe the tension and compression stiffness of bolted flange joint section, then the bending stiffness model of whole bolted flange joint is established based on that. The results show that there is a significant effect of the bolted flange joint on the local stiffness of the rotor, the loss of local bending stiffness reach a high level when the number of bolts is few. The mathematical description between stiffness loss and structure size, load and assembling condition is obtained through the analytical results. A bolted flange joint simulation model, taking the characteristics of the contact into account, is built by the nonlinear finite element method. The trends of numerical results agree with the analytical conclusion, and show the stiffness of bolted flange joint is smaller than that of the fixed configuration. The stiffness of bolted flange joint decreases a small amount with the increasing moment. When the number and the pretension force increases, the stiffness increases nonlinearly. Based on the mechanism of stiffness loss, the equivalent stiffness is used to replace the fixed configuration stiffness on the location of bolts in finite element model of high pressure rotor system. The results of dynamic analysis shows that the stiffness loss has a greater impact on bending modes than the rigid modes while the static analysis shows that the stiffness loss has a small negatively effect on clearances. The study shows that, the stiffness loss of bolted flange joint has a close relationship with the load and assembling conditions. The results show the effectiveness in controlling the mechanical and dynamic properties of the rotor with bolted flange joints by careful adjusting of structural parameter, load parameter and assembling parameter during designing.

3-D Non-Linear Finite Element Analysis of a Non-Gasketed Flange Joint Under Combined Internal Pressure and Axial Loading

2007 ◽  
Author(s):  
Muhammad Abid ◽  
Abdul W. Awan
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Internal Pressure ◽  
Structural Integrity ◽  
Experimental Studies ◽  
Axial Loading ◽  
External Loading ◽  
Flange Joint ◽  
Element Analysis ◽  
Bolted Flange

A number of analytical and experimental studies have been conducted to study ‘strength’ and ‘sealing capability’ of bolted flange joint only under internal pressure loading. Due to the ignorance of the external i.e. axial loading, the optimized performance of the bolted flange joint can not be achieved. A very limited work is found in literature under combined internal pressure and axial loading. In addition, the present design codes do not address the effects of axial loading on the structural integrity and sealing ability of the flange joints. From previous studies, non-gasketed joint is claimed to have better performance as compared to conventional gasketed joint. To investigate non-gasketed joint’s performance i.e. joint strength and sealing capability under combined internal pressure and any applied external loading, an extensive 3D nonlinear finite element analysis is carried out and overall joint performance and behavior is discussed.

New Simplified Dynamic Modeling Method of Bolted Flange Joints of Launch Vehicle

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Gang Li ◽  
Zhaokun Nie ◽  
Yan Zeng ◽  
Jiacheng Pan ◽  
Zhenqun Guan
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Static Analysis ◽  
Dynamic Modeling ◽  
Element Model ◽  
Launch Vehicle ◽  
Modeling Method ◽  
Flange Joint ◽  
Longitudinal Response ◽  
Bolted Flange

Abstract The bolted flange joint is an important source of nonlinearity in dynamical analysis of launch vehicles, which will lead to both longitudinal and transversal responses simultaneously subject to transversal dynamic loads, and may result in the failure of the connection structure. In this paper, a novel simplified dynamic modeling method via structural static analysis is proposed to simulate dynamical response of nonlinear bolted flange joints of launch vehicle, in which only static analysis of the detailed finite element model or static experiment is used for parameter identification of the model. Two types of nonlinear springs are designed for different tensile and compressive stiffness of the bolted flange joint, which affect longitudinal dynamic behaviour of the connection, and a shear spring is used to modify the transversal stiffness. The sections of launch vehicle are modeled as linear beams for efficiency. Effectiveness of the proposed modeling method is confirmed by a typical connection structure, bolted flange connected cylindrical shells, whose finite element models are verified with dynamic experiments. Superiority of the simplified dynamic model from the proposed method is demonstrated by comparing with the previous simplified model. The connection structures with different numbers of bolts are studied, and most of the dynamic responses calculated from the proposed model agree well with those from the finite element model. The coupling vibration of the connection structure is predicted successfully, in which longitudinal response of the structure is excited by the transversal load.

scholarly journals Rigid Finite Element Method in Modeling Composite Steel-Polymer Concrete Machine Tool Frames

Materials ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3151 ◽  
Author(s):  
Paweł Dunaj ◽  
Krzysztof Marchelek ◽  
Stefan Berczyński ◽  
Berkay Mizrak
Keyword(s):  
Finite Element ◽  
Machine Tool ◽  
Experimental Verification ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
High Accuracy ◽  
Mode Shapes ◽  
Polymer Concrete ◽  
Beam Model ◽  
Low Dimensional

At the stage of designing a special machine tool, it is necessary to analyze many variants of structural solutions of frames and load-bearing systems and to choose the best solution in terms of dynamic properties, in particular considering its resistance to chatter. For this reason, it is preferred to adopt a low-dimensional calculation model, which allows the user to reduce the necessary calculation time while maintaining a high accuracy. The paper presents the methodology of modeling the natural frequencies, mode shapes, and receptance functions of machine tool steel welded frames filled with strongly heterogenous polymer concrete, using low-dimensional models developed by the rigid finite elements method (RigFEM). In the presented study, a RigFEM model of a simple steel beam filled with polymer concrete and a frame composed of such beams were built. Then, the dynamic properties obtained on the basis of the developed RigFEM models were compared with the experimental results and the 1D and 3D finite element models (FEM) in terms of accuracy and dimensionality. As a result of the experimental verification, the full structural compliance of the RigFEM models (for beam and frame) was obtained, which was manifested by the agreement of the mode shapes. Additionally, experimental verification showed a high accuracy of the RigFEM models, obtaining for the beam model a relative error for natural frequencies of less than 4% and on average 2.2%, and for the frame model at a level not exceeding 11% and on average 5.5%. Comparing the RigFEM and FEM models, it was found that the RigFEM models have a slightly worse accuracy, with a dimensionality significantly reduced by 95% for the beam and 99.8% for the frame.

Three-Dimensional Finite Element Analysis of Bolted Joint With Helical Thread Connection

2014 ◽  
Author(s):  
Kondaiah Bommisetty ◽  
Kumar Narayanan
Keyword(s):  
Finite Element ◽  
Contact Pressure ◽  
Axial Load ◽  
Circumferential Direction ◽  
Outer Diameter ◽  
Fe Model ◽  
Flange Joint ◽  
Loaded Surface ◽  
Thread Root ◽  
Bolted Flange

Conventional analytical and numerical methods for the mechanical properties of helical threads are relied on many assumptions and approximations and thus hardly yield satisfactory results. In this paper, an effective mesh generation scheme is used which can provide accurate helical thread model to analyse specific characteristics of stress concentrations and contact pressure distributions caused by the helical thread geometry. Sector model of bolted flange joint has been analysed for pretension alone and combination of pretension and axial load. Using the finite element (FE) model with accurate thread geometry with pretension, the thread root stresses, contact pressure along the helix and at the nut loaded surface in the circumferential direction have been studied. The peak stress occurs at the first engaged bolt thread root from nut loaded surface. This stress at the thread root gradually decreases towards the free face of the nut. The contact pressure at nut bearing surface varies in the circumferential direction because of the circumferential variation of the stiffness of engaged threads adjacent to the nut loaded surface. The axial load along the engaged threads gradually decreases from nut loaded surface to zero towards the free surface of the nut. Results from analysis with pretension and axial load indicate that the contact separation starts at the inner radius of flange and grows towards outer diameter of flange as the axial load is increased in the bolted flange joint. It is observed from the analyses that the load is shared by flanges when the external applied axial load is up to 15% of preload, and beyond this, bolt starts sharing external load. The maximum stress occurs at the first engaged bolt thread root. Most of the bolt failures are at the first engaged thread. The study suggests that it is necessary to consider threads in FE model to obtain accurate contact pressure, thread stress, stiffness and bolt load predictions. These critical observations provide insight for optimization of bolted flange joint to meet the structural requirements and weight optimisation.

Nonlinear dynamic properties of the rotor-bearing system involving bolted disk-disk joint

2020 ◽  
pp. 095440622097616
Author(s):  
Zhong Luo ◽  
Yuqi Li ◽  
Lei Li ◽  
Zijia Liu
Keyword(s):  
Critical Speed ◽  
Dynamic Properties ◽  
Rotor System ◽  
Structural Parameter ◽  
Largest Lyapunov Exponent ◽  
Three Dimension ◽  
Bolted Joint ◽  
Response Curves ◽  
Typical Structure ◽  
Joint Element

Bolted joints are major components to connect the multiple stages of disks in the aero-engine, which directly influences the motion state of the rotor system. This paper studies the effect of some typical structure parameters on the time-varying bending stiffness of the bolted disk-disk joint through finite-element simulations. Based on the Lagrange’s equations, a two-node element used to represent the bolted joint is derived, which is called the joint element. Then, a mathematical model of the rotor system with a bolted disk-disk joint supported by ball bearings is established through the Timoshenko beam and the joint element. The dynamic model is numerically solved using the Newmark-β method. The largest Lyapunov exponent, three-dimension spectral plots, and frequency-response curves are employed to reveal the effect of the bending behavior on the rotor dynamics. Comparisons indicate that the structural parameter of the bolted joint has a slight influence on motion stability, critical speed, and amplitude corresponding to the critical speed. Finally, an experimental study is conducted through a bolted-disk joint rotor test rig with an electrical tightening wrench, showing that the increase of pre-tightening torque will lead to a decrease of the amplitude corresponding to critical speed due to the hardening effect. The modeling method proposed in the present work paves a way for modeling and analyzing of the rotor system with a bolted disk-disk joint.

Using the Simple Structural Beam (SSB) Model to Optimize and Analyze Automotive Structures for Bending Stiffness and Natural Frequency

2014 ◽  
Author(s):  
Ian Wood ◽  
Ahmad Barari ◽  
Ebrahim Esmailzadeh
Keyword(s):  
Natural Frequency ◽  
Early Stage ◽  
Dynamic Properties ◽  
Weight Ratio ◽  
Bending Stiffness ◽  
Beam Model ◽  
Beam Elements ◽  
Fundamental Natural Frequency ◽  
Stage Of Development ◽  
Vehicle Structure

When designing a vehicle structure, an optimum design is desired because the structure has a significant impact on its performance. The structure impacts other components in the vehicle as well. The designing process usually involves complex iteration. Analyses must be done at the early stage of the vehicle’s development (body-in-white) to minimize the amount of parameter changes needed during the late stage of development. Successfully implementing this strategy reduces the time and cost required to develop an effective vehicle structure. A method known as Simple Structural Surfaces can be used to model the vehicle structure as several planar sheets, as well as determine the forces in each sheet. The downside of using this method is that by using it, determining the deflections in the structure is difficult. In order to eliminate this difficulty, the vehicle is modeled as several beam elements instead. In this method, a finite element method is used to numerically solve for the deflections, reaction forces, and internal loading on each element of the structure. This Simple Structural Beam model can be adapted to allow optimization of the static property of the structure bending stiffness. Dynamic properties of the vehicle structure are also examined through vibration analysis, by determining the fundamental natural frequency of the structure. Vibration also has a large impact on the structure’s performance. The goal of the research is to obtain a design that will optimize the static and dynamic properties of the vehicle’s structure. In the beam elements, the parameters involved are the length, orientation, cross-sectional area, and moment of inertia. The optimizing process is automated and determines the beam dimensions with largest stiffness to weight ratio. The fundamental natural frequency calculated must be distant from the frequency of the engine, as resonance is also a concern for structural performance. Resonance occurs when the natural frequency of the system is equal to the frequency of a connecting component. This increases the amplitude of vibration significantly and is undesirable for any structural design.

Modeling and Simulation of Dynamic Property of Vehicle Frame Based on Finite Element Method

2013 ◽  
Vol 367 ◽  
pp. 118-121
Author(s):  
Sheng Li Kong
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Modeling And Simulation ◽  
Working Conditions ◽  
Dynamic Property ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
High Accuracy ◽  
Beam Model ◽  
Shell Models

The dynamic property of vehicle frame directly affects the safety and comfort of whole vehicles. In order to fully understand the dynamic properties of vehicle frame, both finite element beam and shell models for vehicle frame are established and the natural frequencies of vehicle frame in free working conditions are obtained. The results from beam model and shell model have high accuracy. Those results can be helpful for improvement and optimization of the vehicle frames.

Hybrid Reduced Model of Rotor

2013 ◽  
Vol 60 (3) ◽  
pp. 319-333
Author(s):  
Rafał Hein ◽  
Cezary Orlikowski
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Hybrid Model ◽  
Rotor System ◽  
Reduced Model ◽  
Order Model ◽  
Gyroscopic Effect ◽  
Reduced Models ◽  
Rigid Finite Element Method ◽  
Low Order

Abstract In the paper, the authors describe the method of reduction of a model of rotor system. The proposed approach makes it possible to obtain a low order model including e.g. non-proportional damping or the gyroscopic effect. This method is illustrated using an example of a rotor system. First, a model of the system is built without gyroscopic and damping effects by using the rigid finite element method. Next, this model is reduced. Finally, two identical, low order, reduced models in two perpendicular planes are coupled together by means of gyroscopic and damping interaction to form one model of the system. Thus a hybrid model is obtained. The advantage of the presented method is that the number of gyroscopic and damping interactions does not affect the model range

scholarly journals Beam Theory of Thermal–Electro-Mechanical Coupling for Single-Wall Carbon Nanotubes

Nanomaterials ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 923
Author(s):  
Kun Huang ◽  
Ji Yao
Keyword(s):  
Mechanical Properties ◽  
Carbon Nanotubes ◽  
Beam Theory ◽  
Bending Stiffness ◽  
Single Wall Carbon Nanotubes ◽  
Beam Model ◽  
Euler Beam ◽  
New Model ◽  
Mechanical Coupling ◽  
Electrostatic Fields

The potential application field of single-walled carbon nanotubes (SWCNTs) is immense, due to their remarkable mechanical and electrical properties. However, their mechanical properties under combined physical fields have not attracted researchers’ attention. For the first time, the present paper proposes beam theory to model SWCNTs’ mechanical properties under combined temperature and electrostatic fields. Unlike the classical Bernoulli–Euler beam model, this new model has independent extensional stiffness and bending stiffness. Static bending, buckling, and nonlinear vibrations are investigated through the classical beam model and the new model. The results show that the classical beam model significantly underestimates the influence of temperature and electrostatic fields on the mechanical properties of SWCNTs because the model overestimates the bending stiffness. The results also suggest that it may be necessary to re-examine the accuracy of the classical beam model of SWCNTs.

scholarly journals Research on the longitudinal mechanical behaviours of subway turnouts of large slope under train braking force

2021 ◽  
Vol 104 (2) ◽  
pp. 003685042110283
Author(s):  
Zhiping Zeng ◽  
Ji Hu ◽  
Chunyu Tian ◽  
Ping Li ◽  
Xiangdong Huang ◽  
...  
Keyword(s):  
Finite Element ◽  
Temperature Change ◽  
Mechanical Characteristics ◽  
Element Model ◽  
Longitudinal Displacement ◽  
Longitudinal Deformation ◽  
Longitudinal Stiffness ◽  
Mechanical Behaviours ◽  
Longitudinal Resistance ◽  
Safety And Stability

To study subway turnouts’ adaptability to steep gradients, a finite element model of a metro No. 9 simple turnout was established. The main works include: (1) The train’s most unfavourable loading condition was modelled. (2) The turnout’s longitudinal displacement and stress were analysed with different gradients under the train braking load, temperature change load and a combination of the two, to determine the structure’s safety and stability under the most unfavourable working conditions. (3) The turnout structure’s cumulative longitudinal deformation under reciprocating load was studied. Both a fastener longitudinal resistance-displacement experiment under reciprocating load and a numerical simulation of No. 9 turnout modelled by the finite element modelling software, ANSYS, were carried out to study the gradient’s influence on the turnout’s longitudinal mechanical characteristics. (1) The turnout’s longitudinal displacement and stress increase linearly with an increase in gradient and temperature change, both of which are unfavourable to the turnout structure. As the gradient increases from 0‰ to 30‰, the longitudinal stress and displacement increase by more than 10%. (2) The turnout’s rail strength and displacement on a 30‰ slope under the most unfavourable load conditions are within the specification limitations. (3) Under reciprocating load, the fastener longitudinal stiffness decreases and the maximum and residual longitudinal displacement of the switch rail increase; an increased gradient intensifies these effects on the turnout.

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