Micromechanism Study And Finite Element Simulation Of Fatigue Fracture Process Of High Strength Aluminum Alloy

With herniation property advantages of high specific strength, good processabilityand low price, high-strength aluminum alloys become the important structural materialsfor the means of transport and many military and civilian aircraft, and which have animportant strategic position in the national defense construction and development of thenational economy. Fatigue crack initiation more occurred in the inherent defects of thematerials (such as porosity defects and inclusions), and fatigue failure is the main failureform of aircraft, ships, vehicles, nuclear, chemical and marine engineering structures.Therefore, avoiding the occurrence of fatigue failure has significant economic and socialbenefits for the protection of life and property safety and the conservation of resources,etc.For the problem of fatigue fracture caused by fatigue crack initiation ofhigh-strength aluminum alloy components, the author carried out research work. Thisarticle will focus on the fatigue damage of high-strength aluminum alloy (2024, Al-Znalloy) thick plates which consider inclusions as the main location of fatigue crackinitiation. Study the effects of the inclusions’ position in particle size, shape and thesurrounding matrix crystal material characteristics and other factors on the stress fieldsaround inclusion particles in the surface by using a finite element analysis method, thenresearch the effects of the variation of aspect ratio and angle on the crack initiation; createa finite element method which can estimate the location of surface crack initiation pointbased on the crack criterion; reconstruct the2D and3D microscopic structure model ofthe second phase inclusion particles on the basis of the statistical results of theobservation and measurement of the second phase inclusion particles of the materialsurface, and then obtains the effects of real inclusion particles morphology on fatiguecrack initiation; analysis the specific conditions of crack initiation, growth and fractureby simulating crack initiation and propagation process of second phase inclusion particles,and compare the results between numerical simulation and experimental observations;finally, study the effects of the distribution of grain and crystal orientation on the stress distribution and crack initiation.The micro-based material fatigue crack prediction model established in this articlebased on the microscopic nature of the material has important significance for theprevention of the occurrence of component fatigue fracture, and it can be furtherextended to the alloy materials which consider other defects as the major factors of crackinitiation.