Unique Challenges for Bolted Joint Design in High-Bypass Turbofan Engines

2005 ◽  
Vol 127 (2) ◽  
pp. 240-248 ◽  
Author(s):  
Robert P. Czachor
Keyword(s):  
High Speed ◽  
Analytical Techniques ◽  
Aircraft Engine ◽  
Bolted Joints ◽  
Turbine Engines ◽  
Bolted Joint ◽  
Turbofan Engines ◽  
Component Test ◽  
Structural Failures ◽  
Fan Blade

Bolted joints are used at numerous locations in the rotors and carcass structure of modern aircraft turbine engines. This application makes the design criteria and process substantially different from that used for other types of machinery. Specifically, in addition to providing engine alignment and high-pressure gas sealing, aircraft engine structural joints can operate at high temperatures and may be required to survive very large applied loads which can result from structural failures within the engine, such as the loss of a fan blade. As engine bypass ratios have increased in order to improve specific fuel consumption, these so-called “Ultimate” loads increasingly dominate the design of bolted joints in aircraft engines. This paper deals with the sizing and design of both bolts and lever flanges to meet these demanding requirements. Novel empirical methods, derived from both component test results and correlated analysis have been developed to perform strength evaluation of both flanges and bolts. Discussion of analytical techniques in use includes application of the LS-DYNA™ code for modeling of high-speed blade impact events as related to bolted joint behavior.

Unique Challenges for Bolted Joint Design in High-Bypass Turbofan Engines

2003 ◽  
Author(s):  
Robert P. Czachor
Keyword(s):  
High Speed ◽  
Analytical Techniques ◽  
Aircraft Engine ◽  
Bolted Joints ◽  
Turbine Engines ◽  
Bolted Joint ◽  
Turbofan Engines ◽  
Component Test ◽  
Structural Failures ◽  
Fan Blade

Bolted joints are used at numerous locations in the rotors and carcass structure of modern aircraft turbine engines. This application makes the design criteria and process substantially different from that used for other types of machinery. Specifically, in addition to providing engine alignment and high-pressure gas sealing, aircraft engine structural joints can operate at high temperatures and may be required to survive very large applied loads which can result from structural failures within the engine, such as the loss of a fan blade. As engine bypass ratios have increased in order to improve specific fuel consumption, these so-called “Ultimate” loads increasingly dominate the design of bolted joints in aircraft engines. This paper deals with the sizing and design of both bolts and lever flanges to meet these demanding requirements. Novel empirical methods, derived from both component test results and correlated analysis have been developed to perform strength evaluation of both flanges and bolts. Discussion of analytical techniques in use includes application of the LS-DYNA™ code for modeling of high-speed blade impact events as related to bolted joint behavior.

Designing for Maintainability in Preliminary Aircraft Engine Design

1997 ◽  
Author(s):  
Carrie R. Nottingham ◽  
Roberto A. Ortega ◽  
Bharadwaj Rangarajan ◽  
Patrick N. Koch ◽  
Farrokh Mistree
Keyword(s):  
High Speed ◽  
High Performance ◽  
Aircraft Engine ◽  
Turbine Engines ◽  
Exploration Process ◽  
Transport Aircraft ◽  
Design Specifications ◽  
Conceptual Design Phase ◽  
Engine Design ◽  
Concept Exploration

Abstract With the high performance demands of turbine engines, particularly during aircraft take-off and landing, the necessity of scheduled and unscheduled maintenance makes designing these engines for maintainability extremely important. Maintenance issues, however, are normally not addressed in the preliminary stages of design. Thus, we are interested in determining top level engine design specifications which include maintainability issues. For this study we use the High Speed Civil Transport aircraft engine cycle as our example. We identify critical maintenance actions and levels for the HSCT and map these maintenance issues into the conceptual design phase. To facilitate a thorough concept exploration process for top level design specifications including maintainability issues, we implement the Robust Concept Exploration Method (RCEM). Our focus in this paper is to demonstrate a method of abstracting maintainability issues to the preliminary stages of design, rather than the results per se.

Observed Rotordynamic Phenomena in Aircraft Gas Turbine Development

2015 ◽  
Author(s):  
Fredric F. Ehrich
Keyword(s):  
Gas Turbine ◽  
High Speed ◽  
Nonlinear Effects ◽  
Aircraft Engine ◽  
Tip Clearance ◽  
Resonant Peak ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Nonlinear Responses ◽  
Remedial Actions

Observations, analysis and understanding of out-of-the-ordinary rotordynamic phenomena (including several instabilities and nonlinear responses) observed in aircraft gas turbine engines and other high-speed rotating machinery over the course of the author’s career in the design and development of aircraft gas turbine engines are described. Some observed phenomena were already widely recognized in the rotordynamic community such as: • Hysteretic whirl • The tip clearance effect on stability of turbomachinery rotors • Instability due to trapped liquids in the rotor • Hysteresis in the resonant peak amplitude • Effective suppression of rotor instability by anisotropy in the engine support structure Other observations were fairly new to the field of rotordynamics at that time they were observed but were identified as being new manifestations of vibration phenomena already familiar to vibration technologists in fields other than high-speed rotordynamics such as: • Sum-and-difference frequency response • Relaxation oscillations • Nonlinear effects of anisotropic clearance in roller and gas bearings At that time these phenomena were observed, the pressure for remediation of the problems they represented in the context of ongoing aircraft engine development resulted in intense attention and analysis which, in turn, often resulted in new insights, useful diagnoses, and effective remedial actions.

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.

scholarly journals Experimental study of lateral resistance of bolted joints using Japanese cedar (Cryptomeria japonica) treated with resin impregnation

2020 ◽  
Vol 66 (1) ◽  
Author(s):  
Keita Ogawa ◽  
Satoshi Fukuta ◽  
Kenji Kobayashi
Keyword(s):  
Short Pulse ◽  
Japanese Cedar ◽  
Bolted Joints ◽  
Bolted Joint ◽  
Yield Load ◽  
Short Pulse Laser ◽  
Resin Impregnation ◽  
Lateral Resistance ◽  
Ultraviolet Wavelength ◽  
Resistance Performance

Abstract The development of wooden joints possessing high resistance performance has become an important issue for the construction of newer buildings. This study attempts to strengthen the lateral resistance of bolted joints using the previously reported plasticizing technique. This technique consists of two processing stages: incising the surface of the wood using an ultraviolet wavelength short-pulse laser and impregnating the resin into the incised area. This technique makes it possible to plasticize only a local part of the wood surface. Bolted joint specimens were assembled using plasticized wood around the bolt hole, and the lateral tests were conducted. Acrylic monomer and urethane prepolymer were used as the impregnating resins and their incision depths were set as 4 and 10 mm. When the lateral load acted parallel to the grain, changes in the lateral resistance characteristics were observed, especially for the stiffness and yield load. For example, when acryl was used, and the incision depth was 10 mm, an increment of 73% in the yield load was observed, as compared to the non-impregnated specimens. The specimen groups impregnated with acryl exhibited greater changes in their properties than those using urethane. When loaded perpendicular to the grain, an increase in properties were observed; however, these increments were lower than those of the groups loaded parallel to the grain.

Accurate Evaluation of Bolt and Clamped Members Stiffnesses Of Bolted Joints

2021 ◽  
Author(s):  
Rashique Iftekhar Rousseau ◽  
Abdel-Hakim Bouzid ◽  
Zijian Zhao
Keyword(s):  
Finite Element ◽  
Joint Stiffness ◽  
Element Model ◽  
Fe Analysis ◽  
Bolted Joints ◽  
Analytical Models ◽  
Fe Modeling ◽  
Bolted Joint ◽  
A New Technique ◽  
External Loads

Abstract The axial stiffnesses of the bolt and clamped members of bolted joints are of great importance when considering their integrity and capacity to withstand external loads and resist relaxation due to creep. There are many techniques to calculate the stiffnesses of the joint elements using finite element (FE) modeling, but most of them are based on the displacement of nodes that are selected arbitrarily; therefore, leading to inaccurate values of joint stiffness. This work suggests a new method to estimate the stiffnesses of the bolt and clamped members using FE analysis and compares the results with the FE methods developed earlier and also with the existing analytical models. A new methodology including an axisymmetric finite element model of the bolted joint is proposed in which the bolts of different sizes ranging from M6 to M36 are considered for the analysis to generalize the proposed approach. The equivalent bolt length that includes the contribution of the thickness of the bolt head and the bolt nominal diameter to the bolt stiffness is carefully investigated. An equivalent bolt length that accounts for the flexibility of the bolt head is proposed in the calculation of the bolt stiffness and a new technique to accurately determine the stiffness of clamped members are detailed.

Viscous Friction Effect During the Process of Tightening and Loosening of Bolted Joints

2021 ◽  
Author(s):  
Qingyuan Lin ◽  
Yong Zhao ◽  
Qingchao Sun ◽  
Kunyong Chen
Keyword(s):  
Friction Coefficient ◽  
Viscous Friction ◽  
Normal Pressure ◽  
Friction Model ◽  
Bolted Joints ◽  
Critical Parameters ◽  
Bolted Joint ◽  
Sliding Velocity ◽  
Friction Effect ◽  
Bearing Friction

Abstract Bolted connection is one of the most widely used mechanical connections because of its easiness of installation and disassembly. Research of bolted joints mainly focuses on two aspects: high precision tightening and improvement of anti-loosening performance. The under-head bearing friction coefficient and the thread friction coefficient are the two most important parameters that affect the tightening result of the bolted joint. They are also the most critical parameters that affect the anti-loosening performance of the bolted joint. Coulomb friction model is a commonly used model to describe under-head bearing friction and thread friction, which considers the friction coefficient as a constant independent of normal pressure and relative sliding velocity. In this paper, the viscous effect of the under-head bearing friction and thread friction is observed by measuring the friction coefficient of bolted joints. The value of the friction coefficient increases with the increase of the relative sliding velocity and the decrease of the normal pressure. It is found that the Coulomb viscous friction model can better describe the friction coefficient of bolted joints. Taking into account the dense friction effect, the loosening prediction model of bolted joints is modified. The experimental results show that the Coulomb viscous friction model can better describe the under-head bearing friction coefficient and thread friction coefficient. The model considering the dense effect can more accurately predict the loosening characteristics of bolted joints.

Renovation features of powder high-speed steels broaches with plazma hardening

2021 ◽  
pp. 82-85
Author(s):  
A.S. Politov ◽  
R.R. Latypov
Keyword(s):  
Gas Turbine ◽  
Comparative Studies ◽  
High Speed ◽  
Atmospheric Plasma ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Cold Atmospheric Plasma ◽  
Plasma Hardening

The comparative studies results of the durability of cutting properties of new and restored by regrinding and repeated plasma hardening with the application of multi-layer Si—O—C—N nanocoating system (PECVD by cold atmospheric plasma) powder high — speed steels broaches teeth for the processing of hard-to-process materials profilecomposite gas-turbine engines components are presented.

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