Fracture Toughness Evaluation of AA 3003 Aluminum Alloy through Alternative Experimental Methods and Finite Element Technique

The structural integrity assessment of a material in the presence of preexisting flaw or an assumed defect falls under purview of fracture mechanics. Though more parameters used for quantifying the effect of crack in structural component plane strain fracture toughness is the frequently used one. Conventional fracture toughness testing involves higher material and facility cost. Hence there is an interest among researchers to look for alternate test methods including non destructive technique. Ball indentation test is one among them Has conducted ball indentation test to study the elastic/plastic deformation behavior of aluminum 2024 [1]. The elastic modulus of the material has been predicted by measuring the peak load (plastic) and depth and correlating with empirical relations. Evaluated fracture toughness from Vickers indentation and tensile data [2]. A theoretical model of for Indentation Energy to Fracture (IEF) was developed and KIC values were compared with CVN energy data. Predicted energy parameter correlation of failure life data between cyclic ball indentation and low cycle fatigue [3]. Finite element simulation of ball indentation was successfully done and the region of failure was determined with appropriate empirical relations. Determined yield strength by developing stress-strain micro probe setup in which the diameter of the grain size is also included in the empirical relation to identify the fracture toughness [4, 5]. The test is best suited for metallic materials for thin applications. Conducted spherical indentation test on metallic materials and compared stress-strain curve values with an optimization algorithm [6]. Material uni-axial properties were analyzed with σ-ε curves. The results were also compared with Hertzian analytical solution for elastic contact. Derived equations for non-linear bending of cantilever and 3-point bending of beams which obeys the Ramberg-Osgood behavior [7]. Standard mathematical relations were adopted to analyze the bending moment and bending stress and the same is correlated to toughness of the material. Developed relation between stress intensity factor and crack indent size to achieve fracture toughness according to Lankford formula [8]. For validation the results have been compared with direct crack measurement. The test results showed better agreement for specimens that produce radial pattern when indented. Assessed the fracture toughness of aluminum by punch test and validated through FEA [9]. The strain energy density and plastic energy were studied from specific models. The test was mainly adopted to study the ductile-brittle transition of aluminum 6061. The results showed an increase of fracture toughness and aging (temperature) of the specimen. Evaluated fracture toughness by miniaturized 3 point bend specimen ranges from 3.3 to 7.0 mm thickness [10]. The test was conducted under Mode-I loading conditions. The fracture toughness values were obtained using loaddeformation curve. In this method AA3003 material is selected as it has high ductility and corrosion resistance also this specific aluminum alloy is used for designing pressure vessels for its desired strength. Ball indentation test has been adopted with steel indenter made of chromium and also three point bend test to calculate KIC of the material. From the literature review it concludes that Ball Indentation test provides methodology for calculation of plane strain facture toughness which is essentially meant for conservative design of thick components. In thick applications light weight requirement is not insisted and also the test method is also simple and less costly. The present work primarily aims at determination of fracture toughness from cyclic ball indentation test and the non-linearity of the material is validated through FEA. Three point bend test is also conducted under room temperature for the conformity of toughness value from ASTME1290-08 and simulated for better results. With not much of researches in this area it motivates to study the material behavior during indentation and its relevance to fracture toughness. Hence it is the interest of this research to simulate the process as closely as possible and validate through simple testing methods including ball indentation test, and three point bend test. The peak load obtained from both the test was determined as the failure load and fracture toughness value was calculated using the empirical relations.