An extensive experimental database has been assembled from very detailed teardown examinations of fatigue cracks found in rivet holes of fuselage structural components. Based on this experimental database, a comprehensive analysis methodology was developed to predict the onset of widespread fatigue damage in lap joints of fuselage structure. Several computer codes were developed with specialized capabilities to conduct the various analyses that make up the comprehensive methodology. Over the past several years, the authors have interrogated various aspects of the analysis methods to determine the degree of computational rigor required to produce numerical predictions with acceptable engineering accuracy. This study led to the formulation of a practical engineering approach to predicting fatigue crack growth in riveted lap joints. This paper describes the practical engineering approach and compares predictions with the results from several experimental studies.

An extensive experimental database has been assembled from very detailed teardown examinations of fatigue cracks found in rivet holes of fuselage structural components. Based on this experimental database, a comprehensive analysis methodology was developed to predict the onset of widespread fatigue damage in lap joints of fuselage structure. Several computer codes were developed with specialized capabilities to conduct the various analyses that make up the comprehensive methodology. Over the past several years, the authors have interrogated various aspects of the analysis methods to determine the degree of computational rigor required to produce numerical predictions with acceptable engineering accuracy. This study led to the formulation of a practical engineering approach to predicting fatigue crack growth in riveted lap joints. This paper describes the practical engineering approach and compares predictions with the results from several experimental studies. Harris, C. E. and Piascik, R. S. and Newman, J. C., Jr. Langley Research Center NASA/TM-2000-210106, NAS 1.15:210106, L-17956

Fatigue of the pressurized fuselages of transport aircraft is a significant problem all builders and users of aircraft have to cope with for reasons associated with assuring a sufficient lifetime and safety, and formulating adequate inspection procedures. These aspects are all addressed in various formal protocols for creating and maintaining airworthiness, including damage tolerance considerations. In most transport aircraft, fatigue occurs in lap joints, sometimes leading to circumstances that threaten safety in critical ways. The problem of fatigue of lap joints has been considerably enlarged by the goal of extending aircraft lifetimes. Fatigue of riveted lap joints between aluminium alloy sheets, typical of the pressurized aircraft fuselage, is the major topic of the present book. The richly illustrated and well-structured chapters treat subjects such as: structural design solutions and loading conditions for fuselage skin joints; relevance of laboratory test results for simple lap joint specimens to riveted joints in a real structure; effect of various production and design related variables on the riveted joint fatigue behaviour; analytical and experimental results on load transmission in mechanically fastened lap joints; theoretical and experimental analysis of secondary bending and its implications for riveted joint fatigue performance; nucleation and shape development of fatigue cracks in riveted longitudinal lap joints; overview of experimental investigations into the multi-site damage for full scale fuselage panels and riveted lap joint specimens; fatigue crack growth and fatigue life prediction methodology for riveted lap joints; residual strength predictions for riveted lap joints in a fuselage structure. The major issues of each chapter are recapitulated in the last section.

A round-robin analysis was conducted which evaluated and compared different methods currently in practice for predicting crack growth under random loading. This report describes the prediction method used by the Fracture Mechanics Engineering Section (FMES) at NASA-Langley Research Center. It also presents the ratios of the predicted lives to the test lives for eleven of the thirteen specimens tested.

Accounting for fatigue loadings has been a concern ever since the widespread introduction of metallic materials into load-bearing components in the nineteenth century. Calculations were developed based on the analysis capabilities of their time incorporating all the latest technologies of their era. At the time, that technology was pencil-and-paper calculations. Today's calculations are computer-based. The widespread use of computing methods has greatly enhanced the analyst abilities for simulating internal stress and strain fields. Unfortunately, current fatigue analyses often force-fit current stress field calculations into fatigue analysis methods meant for nineteenth century stress calculation methods. It's never a good idea to force methods optimized for pre-computer calculations to work with computers. This text presents a more integrated approach to computer-based fatigue analysis methods. Like what was originally done, the latest technologies are applied rather than force-fitting computer computational capabilities into nineteenth-century techniques. Holistic approaches incorporating all knowledge have long been established as the most successful approach to problem-solving. Incorporating all knowledge with the most modern capabilities is the preferred approach. Holistic methods strive to reduce subjective inputs and replace them with consistent objective ones. This text aims to transition disjointed inefficient analyses into a unified computer-based holistic technique by introducing a fatigue analysis method specifically developed for computer simulations. Ultimately, for any method or theory to be valuable, it must be put into practice and prove itself. That entails leadership decision-making. Engineering design development activities will lead to final decisions. Information in a holistic approach must include the reliability of the information. How consistent are the predictions? Are the two types of potential scatter, analytic, and physical properly addressed? Is analytic scatter minimized while maintaining creativity? Is physical scatter totally understood? Effective program management requires knowledge on both types of scatter and, most importantly, the ability to realize the difference. A novel computer-based unified approach to fatigue methods is presented which incorporates a holistic approach for more accurate and consistent analyses, including the management and leadership of fatigue analysis projects, minimization of analytic scatter, management of physical scatter, and unification of methods that minimize subjective inputs often needed to bridge inconsistent techniques.