Below are some of my projects from internships, extracurricular activities, and courses.
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Modeling γ’ Precipitation Hardening in Haynes 233 and 282
At Haynes International, my main project was to develop an application that utilizes material models to predict the resulting mechanical properties from single-step aging. The alloys considered were HAYNES 233 and 282 whose strength is derived from the precipitation of the γ’ phase. Predicting the strength increment as a result of γ’ involved modeling the two different mechanisms associated with precipitation hardening: dislocation shear and dislocation bow (see figure on top right). When dislocations glide on a slip plane and come across a precipitate, they can either shear or bow a precipitate depending on the precipitate and its size. The Orowan bow and Friedel shear models are employed to model this behavior and determine the resulting strength of the material. Both of these models are dependent on various material parameters and are a function of the precipitate size and volume fraction. To minimize the parameters, another model was also utilized, the Ansell-Lenel model. This model is also dependent on various material parameters, but it is only a function of precipitate volume fraction. The Matlab-based application I developed for Haynes incorporates these models with the GUI shown in the figure on the bottom right. |
Precipitation hardening mechanisms : precipitate shearing (top) and bowing (bottom).
GUI interface of application that models the strength increment from γ’ precipitation as a result of one-step aging.
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Modeling Heat Transfer Through a Hybrid Rocket Motor
At Purdue, I was member of Purdue Orbital. The organization aims to design a launch service based on a "rockoon" (rocket-balloon) concept. As part of Orbital, I was the materials lead in the R&D sub-team where I primarily worked on the rocket's propulsion system. A large concern in the design of the combustion chamber was the materials selection due to the intense heat. One of my main contributions was modeling the heat transfer through the chamber and determining the temperatures experienced by the different components. For simplicity, I modeled the heat transfer by way of a thermal resistance network which is analogous to electric circuits. On the top right, an image is shown of the path of the heat through the combustion chamber with each medium being a "resistor" and transferring heat through different ways. The limitation of this approach is using the appropriate material parameters where approximations were made for materials whose parameters were not found. The bottom right image shows an example of the results we can get - the temperature of the paraffin wax (solid fuel) as a function of the burn time. This model helped calculate the temperature experienced by the outer casing and consequently let us narrow down the materials we can use. |
Thermal resistance network of heat transfer through a hybrid combustion chamber. Heat begins in the combustion chamber and transfers convectively and radioactively. From there, the heat is transferred to the paraffin fuel which transfers the heat via conduction. The heat then transfers to the outer casing and conducts outward to the ambient air.
Representative figure showing the inner surface temperature of the paraffin wax during combustion. Note that as paraffin wax is a solid fuel in this system, it has a variable thickness in the rocket motor as it is burned up.
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Finite Element Analysis of Thin-Walled Pressure Vessel
This study analyzes the stress state in the axial and hoop directions of a thin-walled pressure vessel through FEM and compares the results to a simple analytical solution. The main objective of this study is to analyze the effect of tank thickness on the stress states. The FEM conducted in ABAQUS allows for a realistic representation of the problem through boundary and load conditions. The mesh used for the model was informed via a convergence study to see the minimal refinement of mesh required to get a converged solution that is comparable to the analytical solutions. The analytical solution showed fair agreement with the FEM results, and it was seen that an increase in tank thickness led to a decrease in hoop and axial stress. |
(Left) SpaceX's Starship test tank, a pressure vessel that was used to test structural integrity of the design. (Right) The von Mises stress hot spots of FE model based on the Starship test tank.
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Experimental Characterization of Advanced Composites Materials
This study was part of a course taken at Purdue and involved fabricating and characterizing composites with the following tests: tensile, compression, shear, flexure, multiaxial, impact, and thermal tests to determine CTE. The properties were determined considering different layups (orientations and thickness) and varying stress concentrators including notches and open holes. The interdependence of the material properties with the mechanical and thermal properties was analyzed. The mechanical properties of the composites were compared with classical laminate theory where applicable. Download the full report consisting of 15 different experiments below! |
Fracture behavior of [0/45/-45/90] specimen with increasing open hole size from left to right.
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