DEVELOPMENT, CHARACTERIZATION AND DYNAMIC ANALYSIS OF METAL MATRIX COMPOSITE ROTOR

Abstract

Industrial development is one of the pioneer enablers of the economic and social prosperity of any nation. High efficiency, low cost and reliable system are the most critical factors that are focussed by industries. New developments in this direction are observed in the past few decades. Researchers thrive for new inventions and technologies by which high-quality output can be attained with effective and robust systems. Materials play an essential role in achieving high efficiency by providing an outcome-based response to any process. With the advent of composite materials, industries have started focusing on using lighter weight materials with the same mechanical properties. Metal matrix composites have the edge over the parent metals for rotor applications as it has a higher specific modulus and specific modulus is the critical material factor for vibration responses. Aluminium /alumina MMCs have shown prominent growth in the composite material market because of their compatibility with the rotor systems. Several types of research are available for the development of aluminium based metal matrix composites for industrial applications. The main focus of this research is to propose a method of development of metal matrix composite for specific rotary applications. This work focuses on the development, characterization and dynamic analysis of the metal matrix rotor. The rotors are developed through a cost-effective, flexible, and readily available method called the stir casting process. The physical properties of the composites depend primarily on the homogeneity and the fraction of reinforcement in the matrix. The uniformity and the concentration have been enhanced by optimizing process parameters in various researches. However, these

vii researches are based on the qualitative analysis (visual observation) of the microstructure of composites. These qualitative methods do not assist in providing numerical and objective-oriented results. Therefore, these methods lack a objective judgment that is crucial for comparing the dispersion of reinforcements consistently. Therefore, quantitative measurement of dispersion is essential for optimizing the process parameters in order to attain better results. There are several techniques for the quantitative measurement of particle dispersion in the matrix. The mean free path has been calculated by dividing micrograph images into multiple grid lines and was utilized for quantifying particle dispersions. The quantitative distribution index and area fraction may be beneficial in optimizing the process parameters and providing more authentic and reliable results than the qualitative analysis. There are

various methods used for parametric optimization having multivariant parameters. Box- Behnken designs (BBD) are rotatable or nearly rotatable second-order designs based on

three-level incomplete factorial designs. BBD is one of the main types of response surface design, the other being central composite design. The BBD design requires a smaller number of runs as compared to the central composite design. The Box-Behnken design operates within the range of parameters and does not generate experimentation points beyond the range of parameters like the central composite design. BBD is suitable for designs where the range of operations are constrained by manufacturing conditions. In this work, a novel technique has been adopted where newly developed quantitatively assessed responses are used for process optimization instead of conventional qualitative analysis and thus, it provides a profound methodology for optimization of process parameters.

viii A novel characterization approach has been adopted in this work, which determines the effect of reinforcements on the dynamic properties and residual stress of the Al 6061/Al2O3 shafts. Long and slender shafts were fabricated through a stir casting process. Grain structure has been obtained through optical microscopy, and morphological evaluation of the composites was performed through Scanning Electron Microscopy (SEM). In addition to that, an X-ray diffraction pattern (XRD) were analyzed, and residual stress was calculated by X-ray residual stress measurement system μ-X360 Ver. 2. 3. 0. 1. Tensile strength and microhardness were also determined in this analysis for various compositions of the composite material. For composite materials, the system response changes abruptly with a change in the properties of the material. Therefore, attaining significant knowledge about the effect of material composition on material properties is crucial. The researchers are looking for new computational methods which can predict these alterations so that the effort in experimental testing can be reduced. In this direction, this paper presents a robust and novel methodology of validating the estimation of the composite's effective properties through a multi-scale approach by a set of standardized experimentation. These effective properties are estimated through the mean-field homogenization technique, whose parameters are driven from the image analysis of Scanning Electron Microscopy (SEM) images. The predicted results are validated with the results obtained by the experimentation as per ASTM E1876 standard. This research work has adopted a novel approach of providing a dedicated methodology for determining the calibrated internal damping factor for bond graph dynamic analysis, which has been used in various literature for transient and stable

ix responses. The investigation has been performed on long and slender shafts of the metal matrix composites. An insight into the change in dynamic response with the difference in the composition of composite shafts is provided in this work. Many valuable insights and findings were obtained in this work related to the development and response of different compositions of metal matrix composite shafts. The optimization of the stir casting parameters using a quantitative distribution index and area fraction resulted in uniformly distributed composite shafts. The mechanical properties such as tensile strength, microhardness, specific modulus increased with the addition of reinforcement in the composite up to a particular limit. Above that limit, the agglomeration and porosity become prominent factors and further depletes the properties of a composite. The natural frequency of the composite shaft increased, and the amplitude of vibration was reduced for the composites with a high volume fraction of reinforcements. The values of Young's modulus of different compositions determined through computation were congruent with the experimental results. The dynamic response was simulated using bond graph analysis, and it was observed that the amplitude of orbits was also reduced for the composites with a high volume fraction of reinforcements.