No abstract

No abstract

No abstract

KarlsruheGcrmsI v MARCP 19q67 FOREWORDThe Structures and Materials Panel, of the Advisory Group for Aerospace Research and Development (AGARD) is comprised of scientists, engineers and technical administrator.s, from industry, government and universities throughout NATO, concermed with aivanc.1kng the statns of aerospace research and development and with developing technical means and data for optimizing the vehicles and equinment of interest to NATO. The Panel, therefore, providea a discussion forum, a mechanism for exchr.aging information, and a means for establishing and conducting cooperative laboratory programs in selected technical areas.One of the technical areas of piime concern to this Panel is that of the behaviour of materJils and structures at high temperatures. The range between about 1300 0 C and 2500 0 C is of particular interest, partly because of the incidence of this range in powerplants, very high speed flight, re-entry from space, propulsion devices such as rockets, etc. Several rrojects have been undertaken by this Panel on the development and behavior (mechanical end chemical) of materials in the lower part of this range but the Panel also recognized the dearth of necessary data on thermophysical properties, the lack of agreement, or in some cases knowledge, on methods of determining these data end the inadequacy of tneory and understanding. It was also recognized that considerable work ws" underway on this subject in various countries. Accordingly, in early 1966, the Panel agreed to initiate a project (1) to examine current -' t ivities and to evaluate the present stage of knowledge of thermal physical properties, (2) to examine techniques for their determination at elevated temperatures and encourage improvement in these techniques or drvipmeut of iiew ones, (3) to promote fundamental research of the type that might .ovide a reliable theoretical basis for the calculaAion of these properties, and (4) possibly to define and organize a cooperative experimental program.As a means of initiating action responLive to the above objectives, Prof. Dr Erich Fitzer, of the Institut fur Chemische Tecunlk, Karlsruho, Germany. was engaged to vibit a nimber of sources in NArG countries in order to prepare a survey of measurement techniques, a related bibliography and a limited compilition of data and theory on selected properties. This publication is Pcofessor Fitzer's first report based primar.l'y on his first series of visits and his related studies. The Panel. in the meantime, has engaged in a supplementary small symposium and is contemplating a limited cooperative laboratory program to test the reliability of measurement of thernal conductivity. It contains a survey of measurement techniques, a related bioliography and a limited compilation of data and theory on selected thermophysical properties of high temperature materials.The visits confirmed that knowledge of thermal conductivity is the key point of all further research in this f'"id, and the report deals mainly with its measurement and theory; ...

Widespread fatigue damage is one of the main damages of aging aircraft structures, and the problem of multi-site damage has always been a research hotspot in engineering analysis. The traditional probabilistic model for calculating the growth rate of multiple cracks takes into account the multiple uncertain parameters that affect each other’s cracks. However, when solving the multi-site damage (MSD) crack growth problem, the traditional random model needs to solve multiple nonlinear equations. This method becomes no longer applicable. Based on the statistical point of view, this study gives the mutual influence factors of the crack growth process in the form of distribution, and then calculates the probability density function of the crack length under different cycles by sampling with the Monte Carlo (MC) method. Finally, compared with the experimental data, the results show that the calculation results of this method are more accurate and are in good agreement with the experimental data. This method is feasible and accurate for multi-crack propagation analysis of random parameter structures.