Gavrylov I. A Comprehensive method for controlling side negative effects caused by the application of film-forming anti-corrosion compounds

The work is devoted to the development of a comprehensive method for the controlling negative side effects caused by the applying corrosion preventive compounds. Requirements for anti-corrosion protection of transport category aircraft are determined by airworthiness standards. An additional means of providing anti-corrosion protection is the use Corrosion Preventive Compounds ( CPC). At the same time analysis of some results points out the necessity to control negative side effects of their application, special attention must be drawn to the negative impact on riveted joins, which are sensitive to cyclical loading and thus define lifetime of aircraft. The aim of the research is prevention of negative side effects caused by the application of film forming anticorrosion compounds. The introduction describes the actuality of the dissertation, formulates aim and objectives of the work. The links with research programs and works, as well as scientific novelty and practical value of the results obtained is shown. Information about the approval of the dissertation work results and personal contribution of the author is provided. The first chapter deals with the review of the literature on the theme of the dissertation work. Significant number of aircraft components failures occurs due to the corrosion and fatigue. Special attention is paid to structural connections, in particular riveted joints, which are highly sensitive to both the corrosive environment and the action of cyclic loading, the combination of which often leads to catastrophic consequences. The peculiarities of the use of corrosion preventive compounds are considered. On the basis of conducted analysis, conclusions were made; the aim and objectives of the research were formulated. The second chapter deals with substantiated methods and techniques of experimental researches. Methodology of the research provided practical value of the work due to the heading on the problem of protection against corrosion for real structures of the planes of transport category. A methodological feature of research is application of the device developed along the process of dissertation research for estimation of the static friction forces in riveted joints. Application of the Finite Elements Methods provided the assessment of the relation between the friction forces in the riveted joint with stress-strain state in the area of fatigue crack nucleation. In third chapter results of the experiments are presented. It is shown that penetration property of the CPC defines their penetration into the gaps of riveted joints. Corrosion preventive compounds, which are being penetrated into the gaps of the joints, cause negative influence on fatigue life were found. Technology of treatment which leads to the reduction of the fatigue life was determined as well. New method for accelerated estimation of friction forces in riveted joints confirmed by the Patent of Ukraine on Utility Model. The following aspects have been studied: influence of the protective film thickness in the gap of the riveted joint on the friction forces; influence of the duration of the time interval between the treatment and loading of the structure; influence of the rivets squeezing force on the friction force. Finite elements analysis of the riveted joint work at the presence of protective compounds provided important conclusion: local stresses in the hole for rivet area depends on static friction between sheets. The fourth chapter describes the comprehensive method for the control of side negative effect caused by application of corrosion preventive compounds. Primary and additional components of the comprehensive method are substantiated and formulated. The scientific novelty of the results: 1. The assumption about influence of corrosion preventive compounds on fatigue life has been substantiated. 2. The relation of the corrosion preventive compounds characteristics and side effects of their application was found. 3. By application of original device, the influence of the corrosion preventive compounds on the static friction between the elements of riveted joint has been assessed. 4. By application of Finite Elements Analysis, the relation of static friction coefficient and stress state at the area of fatigue crack initiation was found. 5. The new complex method for the control of side negative effects caused by application of corrosion preventive compounds has been developed.