Purpose – Devoted to a description and evaluation of a selected maintenance process (assembly) at the aero‐engines maintenance unit of a large aerospace company by implementation of TQM tools, this paper attempts to identify the causes behind the defect observed and form the scientific platform for initiatives in a TQM‐governed enterprise and to broaden the principles of TQM for the selected process, prior to moving to a more structured plan that will include the entire unit.Design/methodology/approach – Process monitoring and evaluation are organised by an application of control charts in order to provide vital information regarding the level of control in the selected process. Quality control data are contrasted with component specifications by employing control charts to provide a metric for the level of the process capability index. As a result a Fishbone diagram is constructed to identify existing interrelations between the causes responsible for the defect observed.Findings – The maintenance process...

An application of TQM tools at a maintenance division of a large aerospace company

This paper presents an application of artificial neural network (ANN) technique for conducting the reliability analysis of Boeing 737 tires. For this purpose, an ANN model utilizing the feed-forward back-propagation algorithm as a learning rule is developed. The inputs to the neural network are the flight operational time and the number of landings as independent variables and the output is the failure rate of the tires. Two years of data are used for failure rate prediction model and validation. Model validation, which reflects the suitability of the model for future predictions, is performed by comparing the predictions of the model with that of Weibull regression model. The results show that the failure rate predicted by the ANN is closer in agreement with the actual data than the failure rate predicted by the Weibull model. The present work also identifies some of the common tire failures and presents representative results based on the established model for the most frequently occurring tire failure. Copyright © 2010 John Wiley & Sons, Ltd.

Artificial neural network application of modeling failure rate for Boeing 737 tires

Multi-scale vibration behavior of a graphite tube with an internal vapor–liquid–solid boiling flow

Effects of fluidized solid particles on vibration behaviors of a graphite tube evaporator with an internal vapor–liquid flow

problem of major interest to researchers and practicing engineers. Tube array vibrations may lead to tube failure due to fretting wear and fatigue. Such failures have resulted in numerous plant shutdowns, which are often very costly. The need for accurate prediction of vibration and wear of heat exchangers in service has placed greater emphasis on the improved modeling of the associated phenomenon of flow-induced vibrations. In this study, the elastodynamic model of the tube array is modeled using the finite element approach, wherein each tube is modeled by a set of finite tube elements. The interaction between tubes in the bundle is represented by fluidelastic coupling forces, which are defined in terms of the multidegree-of-freedom elastodynamic behavior of each tube in the bundle. Explicit expressions of the finite element coefficient matrices are derived. The model admits experimentally identified fluidelastic force coefficients to establish the final form of equations of motion. The nonlinear complex eigenvalue problem is formulated and solved to determine the onset of fluidelastic instability for a given set of operating parameters. DOI: 10.1115/1.3006950

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part I: Numerical Modeling vibrations due to crossflow in the shell side of heat exchangers pose a

The reliability of wear/failure data of brake assemblies of a commercial aeroplane (Boeing 737) is analysed using the Weibull model This model can be effectively integrated into an aviation maintenance facility computerized material requirement planning system to forecast the number of brake assemblies needed for a given planning horizon

Reliability analysis of aeroplane brakes

It has become evident that the modeling of the complex dynamics of fluidelastic forces that give rise to vibrations of tube bundles requires a great deal of experimental insight. Accordingly, the prediction of the flow-induced vibration due to unsteady cross-flow can be greatly aided by semi-analytical models, in which some coefficients are determined experimentally. A laboratory test rig with an instrumented test bundle is constructed to measure the fluidelastic coefficients to be used in conjunction with the mathematical model derived in Part I of this paper. The test rig admits two different test bundles, namely, the inline-square and 45 deg rotated-square tube arrays. Measurements were conducted to identify the flow-induced dynamic coefficients. The developed scheme was utilized in predicting the onset of flow-induced vibrations in two configurations of tube bundles, and results were examined in the light of Tubular Exchange Manufacturers Association (TEMA) predictions. The comparison demonstrated that TEMA guidelines are more conservative in the two configurations considered.

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part II: Experimental Investigation

Flow-induced vibrations due to crossflow in the shell side of heat exchangers pose a problem of major interest to researchers and practicing engineers. Tube array vibrations may lead to tube failure due to fretting wear and fatigue. Such failures have resulted in numerous plant shutdowns, which are often very costly. The need for accurate prediction of vibration and wear of heat exchangers in service has placed greater emphasis on the improved modeling of the associated phenomenon of flow-induced vibrations. In this study, the elastodynamic model of the tube array is modeled using the finite element approach, wherein each tube is modeled by a set of finite tube elements. The interaction between tubes in the bundle is represented by fluidelastic coupling forces, which are defined in terms of the multidegree-of-freedom elastodynamic behavior of each tube in the bundle. Explicit expressions of the finite element coefficient matrices are derived. The model admits experimentally identified fluidelastic force coefficients to establish the final form of equations of motion. The nonlinear complex eigenvalue problem is formulated and solved to determine the onset of fluidelastic instability for a given set of operating parameters.

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part I: Numerical Modeling

The need for accurate prediction of vibration and wear of heat exchangers in service has placed greater emphasis on improved modeling of the associated phenomenon of flow-induced vibrations. It was recognized that modeling of the complex dynamics of fluidelastic forces, that give rise to vibrations of tube bundles, requires a great deal of experimental insight. Accordingly, the prediction of the flow-induced vibration due to unsteady cross-flow can be greatly aided by semi-analytical models, in which some coefficients are determined experimentally. In this paper, the elastodynamic model of the tube array is formulated using the finite element approach, wherein each tube is modeled by a set of finite tube-elements. The interaction between tubes in the bundle is represented by fluidelastic coupling forces, which are defined in terms of the multi-degree-of-freedom elastodynamic behavior of each tube in the bundle. A laboratory test rig with an instrumented square bundle is constructed to measure the fluidelastic coefficients used to tune the developed dynamic model. The test rig admits two different test bundles; namely the inline-square and 45o rotated-square tube arrays. Measurements were conducted to identify the flow-induced dynamic coefficients. The developed scheme was utilized in predicting the onset of flow-induced vibrations, and results were examined in the light of TEMA predictions. The comparison demonstrated that TEMA guidelines are more conservative in the two configurations considered.

http://www.wseas.us/e-library/conferences/2010/Tunisia/CONTROL/CONTROL-11.pdf

S. A. Al-Kaabi

Papers

Reliability analysis of aeroplane brakes

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part I: Numerical Modeling vibrations due to crossflow in the shell side of heat exchangers pose a

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part II: Experimental Investigation

Prediction of Flow-Induced Vibrations in Tubular Heat Exchangers—Part I: Numerical Modeling

The onset of flow-induced vibrations in a square tube array subjected to cross-flow