scholarly journals Aircraft repair damage tolerance analysis

2021 ◽  
Author(s):  
Dejan Markovic
Keyword(s):  
Structural Integrity ◽  
Damage Tolerance ◽  
Tolerance Analysis ◽  
The United States ◽  
Air Travel ◽  
Point Of View ◽  
Economic Life ◽  
Inspection Interval ◽  
Business Jet ◽  
Damage Tolerance Analysis

Modern air travel has become a perpetual evolution both from a practical and scientific point of view. However, it is also becoming increasingly common to fly in an airplane with little or no regard for the immense engineering involvement that goes into making air travel as safe and efficient as possible. This report considers the problems of aircraft fatigue and how it translates to inspectability for safety in order to predict problems and solve them before they actually occur. The most common aircraft repair is a crack in a pressurized skin panel. This report evaluates the structural integrity of a particular panel that is assumed to have failed in service and thus been repaired by the addition of a doubler. Damage tolerance analysis is used to evaluate a conservative crack growth scenario for a typical business jet with a structural economic life of 15,000 flight hours. The step shown follow the guidelines approved by the regulating aviation bodies of both Canada and the United States (Transport Canada and the FAA respectively). Structural inspections are a common practice for aircraft at their half lives; in this case it would be 7,500 flights. The report determines that this particular scenario defines a threshold inspection interval of 8,414 flights and a repeat of 2,944 flights thereafter. In comparison with an actual test aircraft, having experienced an almost identical failure and repair program, the test aircraft experienced failure at 9,963 flights. Therefore, the intervals presented herein provide adequate clearance for the detection and repair of such damage. The purpose of this report is to introduce the underlying principals of damage tolerance analysis to the reader and illustrate the analytical process with a real world example. Such is the job of an aerospace stress engineer.

scholarly journals Aircraft repair damage tolerance analysis

2021 ◽  
Author(s):  
Dejan Markovic
Keyword(s):  
Structural Integrity ◽  
Damage Tolerance ◽  
Tolerance Analysis ◽  
The United States ◽  
Air Travel ◽  
Point Of View ◽  
Economic Life ◽  
Inspection Interval ◽  
Business Jet ◽  
Damage Tolerance Analysis

Modern air travel has become a perpetual evolution both from a practical and scientific point of view. However, it is also becoming increasingly common to fly in an airplane with little or no regard for the immense engineering involvement that goes into making air travel as safe and efficient as possible. This report considers the problems of aircraft fatigue and how it translates to inspectability for safety in order to predict problems and solve them before they actually occur. The most common aircraft repair is a crack in a pressurized skin panel. This report evaluates the structural integrity of a particular panel that is assumed to have failed in service and thus been repaired by the addition of a doubler. Damage tolerance analysis is used to evaluate a conservative crack growth scenario for a typical business jet with a structural economic life of 15,000 flight hours. The step shown follow the guidelines approved by the regulating aviation bodies of both Canada and the United States (Transport Canada and the FAA respectively). Structural inspections are a common practice for aircraft at their half lives; in this case it would be 7,500 flights. The report determines that this particular scenario defines a threshold inspection interval of 8,414 flights and a repeat of 2,944 flights thereafter. In comparison with an actual test aircraft, having experienced an almost identical failure and repair program, the test aircraft experienced failure at 9,963 flights. Therefore, the intervals presented herein provide adequate clearance for the detection and repair of such damage. The purpose of this report is to introduce the underlying principals of damage tolerance analysis to the reader and illustrate the analytical process with a real world example. Such is the job of an aerospace stress engineer.

Damage Tolerance Analysis of Railroad Tank Cars

2000 ◽  
Author(s):  
Wei Zhao ◽  
Michael A. Sutton ◽  
Jose Penã ◽  
Brenda K. Hattery ◽  
Duan Q. Wang ◽  
...  
Keyword(s):  
Structural Integrity ◽  
Damage Tolerance ◽  
Tolerance Analysis ◽  
General Purpose ◽  
Stress Distributions ◽  
Load Spectrum ◽  
Butt Weld ◽  
Service Load ◽  
Damage Tolerance Analysis ◽  
Global And Local

Abstract The paper summarizes an effort in improving structural integrity of the railroad tank cars. Damage tolerance analysis is performed on a DOT 111A100W1 general purpose tank car. Stress distributions and potential fatigue critical locations are determined using global and local finite element models. Welding residual stresses in an unconstrained TC128-B butt weld are obtained using neutron diffraction technique. Fatigue crack growth analysis under a tank car service load spectrum is carried out and inspection intervals are determined for various postulated initial flaws. Two materials are considered, a generic steel (presumably representing A516-70), and A515 for older tank cars.

Fracture Control and Damage Tolerance Analysis

2012 ◽  
pp. 303-326
Keyword(s):  
Structural Integrity ◽  
Damage Tolerance ◽  
Tolerance Analysis ◽  
Crack Size ◽  
Periodic Inspection ◽  
Fatigue Design ◽  
Proof Testing ◽  
Damage Tolerance Analysis ◽  
Fracture Control ◽  
Fail Safe

Abstract Fracture control can be defined as a concerted effort to maintain operating safety without catastrophic failure by fracture. It requires an understanding of how cracks affect structural integrity and strength and the time that a crack can grow before it exceeds permissible size. The chapter describes some of methods used to determine maximum permissible crack size and predict growth rates. It explains how the information can then be used to control fractures through periodic inspection, fail-safe features, mandated retirement, and proof testing. It presents a number of fracture control plans optimized for different circumstances, examines the damage tolerance requirements used by different industries, and discusses various approaches for fatigue design.

Micromechanics-Based Fracture Risk Assessment Using Integrated Probabilistic Damage Tolerance Analysis and Manufacturing Process Models

2016 ◽  
Author(s):  
Michael P. Enright ◽  
R. Craig McClung ◽  
Kwai S. Chan ◽  
John McFarland ◽  
Jonathan P. Moody ◽  
...  
Keyword(s):  
Grain Size ◽  
Gas Turbine ◽  
Manufacturing Process ◽  
Damage Tolerance ◽  
Random Variables ◽  
Software Tool ◽  
Tolerance Analysis ◽  
Turbine Engine ◽  
Damage Tolerance Analysis ◽  
Time Required

Materials engineering and damage tolerance assessment have traditionally been performed as disjoint processes involving repeated tests that can ultimately prolong the time required for certification of new materials. Computational advances have been made both in the prediction of material properties and probabilistic damage tolerance analysis, but have been pursued primarily as independent efforts. Integrated computational materials engineering (ICME) has the potential to significantly reduce the time required for development and insertion of new materials in the gas turbine industry. A manufacturing process software tool called DEFORM™ has been linked with a probabilistic damage tolerance analysis (PDTA) software tool called DARWIN® to form a new capability for ICME of gas turbine engine components. DEFORM simulates rotor manufacturing processes including forging, heat treating, and machining to compute residual stress and strain, track anomaly location, and predict microstructure including grain size and orientation. DARWIN integrates finite element stress analysis results, fracture mechanics models, material anomaly data, probability of anomaly detection, and inspection schedules to compute the probability of fracture of a gas turbine engine rotor as a function of operating cycles. Previous papers have focused on probabilistic modeling of residual stresses in DARWIN based on manufacturing process training data from DEFORM. This paper describes recent efforts to extend the probabilistic link between DEFORM and DARWIN to enable modeling of residual strain, average grain size, and ALA (unrecrystalized) grain size as random variables. Gaussian Process modeling is used to estimate the relationship among model responses and material processing parameters. These random variables are applied to microstructure-based fatigue crack nucleation and growth models for use in probabilistic risk assessments. The integrated DARWIN-DEFORM capability is demonstrated for a representative engine disk model which illustrates the influences of manufacturing-induced random variables on component fracture risk. The results provide critical insight regarding the potential benefits of integrating probabilistic computational material processing models with probabilistic damage tolerance-based risk assessment.

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