Determination of the dynamic elastic properties of Ti-6Al-4V parts manufactured with electron beam melting by impulse excitation technique

Ti-6Al-4V alloy is widely used in applications of aerospace, dental and automotive industries due to its high strength, high corrosion resistance and low density characteristics. However, the parts manufactured through conventional methods require machining challenges such as long machining time, tool wear and high cost. Because of these challenges it has restricted usage areas. Therefore, currently Ti-6Al-4V parts are manufactured by using one of the additive manufacturing methods. The main purpose of this thesis is to investigate whether the samples produced by additive manufacturing in different orientations can be used as a counterpart for the samples produced by the traditional manufacturing methods in terms of dynamic elastic properties. In this study, the samples are produced by the electron beam melting (EBM) method. Dynamic Young's modulus and dynamic shear modulus of the samples manufactured by EBM method were determined by the impulse excitation technique. The optimum dimensions of the samples for the impulse excitation technique is determined by finite element analysis. In order to investigate the effects of build direction on the material properties of Ti-6Al-4V alloy, the samples were fabricated in horizontal and vertical build directions. In order to make the samples produced by electron beam melting method suitable for the impulse excitation test method, the samples are machined without the need for pre-heating treatment. The elastic properties are determined according to ASTM 1876-15. Natural frequencies and the frequency response function (FRF) plots of the samples were obtained by using the impulse excitation test method. The value of dynamic Young's modulus is calculated by using the natural (resonant) frequency in the fundamental flexural mode of vibration. Similarly, the dynamic shear modulus is determined by using the fundamental torsional resonant frequency. In order to compute the Poisson's ratio, the formula between dynamic shear modulus and dynamic Young's modulus is used. As a result of this study it is found that the dynamic elastic material properties of the Ti-6Al-4V alloy plate samples produced by electron beam melting method provide the minimum material property requirements that the Ti-6Al-4V plates produced by the conventional methods according to SAE AMS4911R. The natural frequencies of the sample produced in the vertical built direction are higher than that of the natural frequencies of the sample built in the horizontal direction. The dynamic Young's modulus of the sample produced in the vertical built direction are higher than the dynamic Young's modulus of the sample built in the horizontal direction. The damping factor values of the specimen manufactured in the vertical build direction for all modes are lower than the damping factor values of the specimen manufactured in the horizontal build direction.