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A brief review is given of work performed in the Netherlands in the field of aeronautical fatigue. Where possible, applicable references have been presented.

In dit rapport, dat een vervolg is op het NLL rapport TM S.548, wordt de numerieke oplossing van warmtegeleidingsvraagstukken met behulp van differentiemethoden nader bestudeerd. Twee differentiemethoden worden aan de hand van een eenvoudig rekenvoorbeeld vergeleken. Als voorbeeld voor de berekening van temperatutirsverdelingen in aërodynamisch verhitte vliegtuigconstructies wordt een numerieke oplossing gevonden voor de in rapport S.548 op analytische wijze bestudeerde huidplaat-lijfplaatcombinatie. Ten slotte wordt aandacht besteed aan het probleem der thermische weerstand van verbindingen in vliegtuigconstructies.

This memorandum presents results of crack propagation tests on notched Alclad 2024-T351 sheet specimens. Two thicknesses were investigated (2 mm and 8 mm), as well as various spectrum modifications and the effect of clustering of severe flights within the test load sequence.

The present review gives a brief summary of the work performed in the Netherlands in the field of aeronautical fatigue, during the period from March 1993 until March 1995. The contributions come from three different sources, namely: The National Aerospace Laboratory (NLR) • The Department of Aerospace Engineering, Delft University of Technology (DUT) Fokker Aircraft B.V. The names of the principal investigators and their affiliation are presented between brackets at the end of each topic title

Standard methods for the calculation of Design Continuous Gust Loads cannot be applied in the case of aircraft with nonlinear response characteristics. In such cases, Design Loads can be calculated using stochastic simulation techniques. These techniques, however, require a very large computational effort. Hence, alternative methods, indicated as "Deterministic Spectral Gust Methods" have been developed. This report gives a brief review and comparison of three of these methods. A proposal is formulated for a Cooperative Working Activity, to evaluate and validate these methods as an "acceptable means" for the Definition of Design Continuous Gust Loads for nonlinear aircraft.

The paper starts with a general discussion on various aspects of life re-assessment. Specific attention is paid to the possibility of re-assesgrnent by means of comparative fatigue tests on specimens. As an illustration of this method, the paper gives a description of the life-re-assessment procedures applied by the Royal Netherlands Airforce for their NF 5A/B aircraft. Paper presented at the Xth ICAF-Symposium, 16-18 May 1979, Brussels, Belgium.

Due to the development of servo hydraulic fatigue testing machines, fatigue tests under realistic loading conditions have become possible. In these tests, standardized load sequences can be applied. The paper describes the main properties of such sequences, including TWIST and FALSTAFF. Various examples of application of these sequences are presented. The paper ends with a discussion on the future development of stemdard sequences. Paper presented at the 2nd AIFA (Italian Association on Aeronautical Fatiguw) Meeting, Naples, 26-28 February 1980.

Many military aircraft are used more severely and over a longer periodthan originally intended. Consequently, a careful life management, including service load monitoring has become indispensable. This paper describes the development of a simple method to quantify the severity in terms of "potential crack growth" of recorded load spectra. This Crack Severity Index accounts for load interaction effects under spectrum loading. Crack growth tests under a variety of different load spectra have proved the validity of the CSI-concept. It is shown that the CSI-concept can also be used as a tool in studies to influence fatigue life consumption by operational measures.

Buckling loads euid interaction curves are derived for plates having all four edges clamped, or two opposite edges clamped and the other two simply supported. The analysis is hased on Bijlaard's method of split rigidities in combination with the energy method. A comparison is made with results derived elsewhere without the use of Bijlaard's method, A simple procedure for computing additional results without the use of the computer programme is given in the appendix.

Since more than ten years, service load data, including e.g. acceleration peaks, recorded in B747 aircraft have been stored at NLR in the so-called AIDS-Fatigue Data Base. This paper describes the procedures applied to reduce the acceleration date to "delivered gust velocities". The results are presented and compared with other data sources. The validity of the assumptions made in the derivation are discussed.

In this Report the analysis of the response of the "Fokker Bond Tester" on single lap joints, given in NLR Report M.2080, is extended to the case of douhle lap joints. Theoretical results are compared with measurements, indicating a good agreement "between theory and experiment.

A series of Redux-bonded single and double lap-joints with non-porous gluelayers of various glueline thicknesses were tested ultrasonically by means of the Fokker Bond Tester. Tensile shear tests were carried out after completion of the ultrasonic tests. Bond Tester indications were in good agreement with theoretical results , indicating the instrument's ability to detect glueline stiffness. The static strength of double lapjoints turned out to be nearly independent of glueline thickness} for single lapjoints a strong dependence on glueline thickness was found. The analysis of the tensile shear testof adhesive bonded Joints is discussed.

A statistical analysis was made of flight load data pertaining to about 10000 RNLAF F-104G operational flights. The distributions of load experience per flight could be fairly well approximated by Weibull-distribution functions. Specific attention is paid to the differences in load experience per aircraft. The paper concludes with a discussion on basic aspects of Fatigue Load Monitoring.

A brief review is given of work performed in the Netherlands in the field of aeronautical fatigue. Where possible, applicable references have been presented. This review will be presented at the 25th ICAF Conference, Edinburgh, United Kingdom, 16-17 June 1997.

A brief review is given of work performed in the Netherlands in the field of aeronautical fatigue. Where possible, applicable references have been presented.

Modern aircraft structures have a finite fatigue life. During the design an estimation of the aircraft usage and the associated load experience will be made. Safe service lives and inspection schedules are determined by analysis and tests on the basis of this design load spectrum. However, the actual service usage can deviate appreciably from design assumptions. In that case a re-assessment of lives and inspection schedules will be necessary. This paper gives a brief review of methods for monitoring fatigue loads in service.

The contents of this report will become part of an AGARDograph with the title: "Helicopter Fatigue Design Guide". After a general definition of counting principles, a detailed description of the so called Range Pair- Range or Rainflow Counting Method is presented. Flow diagrams are included. The method is illustrated by means of a worked-out example.

Using a relatively simple model, calculations are made of the effect of various load spectrum variations on fatigue damage accumulation for fighter aircraft, with specific reference to RNLAF F-16 A/B aircraft. As the larger part of the total damage is due to manoeuvres with peak value between An = 3.5 and An = 6, reduction of manoeuvring in this range is most effective in reducing fatigue damage. Truncation of the load spectrum, by restricting the maximum load factor, has an unfavourable effect on fatigue damage.