Monitoring of the fatigue of d16aт alloy according to the characteristics of deformation surface pattern

Abstract

It is shown that the deformation pattern is formed under cyclic loads and develops on the surface of the cladding layer of a structural aluminum alloy. The quantitative parameters of the deformation pattern, namely, the saturation, roughness, and plastic strains on the surface, serve as indicators of damage to the material. The experimental dependences of the analyzed parameters on the operating time (number of loading cycles) can be used for the creation of new methods aimed at the prediction of the limit state of structural elements of the aircraft structures.

Multi-purpose fatigue sensor. Part 2. Physical backgrounds for damages accumulation and parameters of their assessment

“…Microscale level. The force affecting the surface layer of the specimen gives rise to changing the stress-strain state of its local volumes, generation, accumulation and annihilation of point defects [23][24][25]. However, the main relaxation processes are carried due to formation of microscale shear strains.…”

Evolution of the deformation relief on the surface of a clad aluminum alloy at random cyclic loads

“…The surface image with DR traces was digitally processed, and 3D topography of an examined surface was determined [11].…”

“…The process of plastic deformation in clad layer occurs in the rate exceeding that in the D16 core material. Discussed parameters, including micro plastic deformation have been selected due to the good correlation with the accumulated damage as it was proved by the experiments presented in the works [11].…”

“…where S is the total area with DR traces on an examined site of the surface area A. The DR in the direction normal to the surface was quantitatively characterized by the roughness The procedure of determining the surface area variations by the measurement results of its 3D topography is presented in the study [11].…”

“…Micron-Alpha noncontact interference profilometer permits of determining additional DR characteristics (3D numerical data), which cannot be identified from optical 2D images. They are the relative roughness of the surface relief a R and microplastic surface strain a  [11]. The interrelation between these DR characteristics and its saturation D was studied under regular cyclic loading of the specimens from a D16AT aluminium alloy with a thin cladding layer [11] The present study is devoted to the behaviour of the DR characteristics at random cyclic loads close to the in-service range for aircraft structures.…”