Browsing by Author "Hosseini, Sayyed Ali"

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Analytical and experimental study of the effect of cutting tool microgeometry on the impact resistance of milling tools
(2021-01-01) Hopkins, Connor G.; Hosseini, Sayyed Ali
This thesis conducted a two-part investigation into the ability of a milling tool cutting insert to resist the impacts that occur during the milling process, with respect to the cutting edge microgeometry. The first part of this thesis contains a mathematical model that was used to predict the cutting forces acting on the tool during milling, accounting for the edge radius. The second part reports the findings of a series of milling tests that were performed, both to verify the mathematical model and to track the wear and failure of the various milling inserts. Five different edge radii were tested and compared. It was found that altering the edge geometry of the tool does affect the cutting forces, wear behaviour, and impact resistance of the cutting inserts, with an edge radius of 35 μm proving to be the optimum choice.
Application of traveling salesman problem in generating a collision-free tool path in drilling
(2021-04-01) Khodabakhshi, Zahra; Hosseini, Sayyed Ali
In machining, the tool path is generated according to the workpiece geometry and arrangement of holes. Majority of Computer Aided Manufacturing (CAM) software offer a set of predefined strategies to choose from. These tool paths are mostly far from being the optimum path, specifically for complex geometries with non-flat surfaces. This thesis introduces a new algorithm based on Travelling Salesman Problem (TSP). The proposed local search algorithm generates an optimum collision free tool path in drilling operations. The developed optimization algorithm considers multiple constraints such as location of tool origin and presence of obstacles. Furthermore, a discussion on stopping criteria for the developed algorithm is presented. Obtained results confirm the proposed algorithm is capable of providing optimum collision free path with more than 50% reduction (in given examples) in path length compared to the HSMWorks software.
Design and control of an active ankle-foot orthosis
(2022-04-01) DeBoer, Benjamin; Hosseini, Sayyed Ali; Rossa, Carlos
Active ankle-foot orthoses (AAFOs) assist a user unable to dorsiflex the ankle joint. The optimal AAFO is lightweight and aids the user in achieving a nominal gait. This thesis presents the design and control of a novel discrete nonlinear series elastic actuator for AAFOs. The actuator uses regenerative braking to reduce the peak mechanical input power to the AAFO by 77.2%. To control the designed actuator and AAFO, two methods are proposed. First, an adaptive extended state observer is developed to reject disturbance and estimate the error in the dynamics model. Second, a nonlinear model predictive controller is presented to track the ankle trajectory while reducing assistance to the user. The adaptive extended state observer can identify the AAFO and ankle joint parameters. The nonlinear model predictive controller with the adaptive extended state observer reduced the trajectory tracking error by up to 58.3%.
Effect of cutting tool microgeometry when milling hardened steels, a finite element simulation and surface integrity analysis
(2021-01-01) Imad, Mohamd; Hosseini, Sayyed Ali; Kishawy, Hossam
This research work presents a 3D finite element model for the milling of hardened steels. The model was developed using ABAQUS/Explicit software and the Lagrangian approach was utilized. Experimental milling tests were performed to validate the numerically generated cutting forces and chip morphologies. A close agreement between the results was reported. Moreover, experiments results were used to investigate the impact of cutting conditions and the microgeometry of cutting inserts on the cutting forces and the surface integrity. Two levels of feed rate, three levels of cutting speeds, and five levels of edge radii were utilized. The impact of edge radii on the workpiece surface integrity was analyzed in terms of 2D surface roughness, generated feed marks, subsurface plastic deformation, and subsurface microhardness.
Machining of additively manufactured titanium Ti-6Al-4V; cutting forces and chip morphology
(2023-04-01) Nguyen, Nam; Hosseini, Sayyed Ali
This thesis studies the machining of additively manufactured (AM) titanium Ti-6Al-4V and presents a model to determine Johnson Cook (J-C) constitutive parameters from complex machining processes through numerical modeling and experimental validation. The J-C parameters are important in describing the characteristics and behaviors of materials during high-strain rate high-temperature machining processes. These parameters are traditionally determined through time-consuming and costly split-Hopkinson pressure bar tests. The proposed model uses a combination of experimentally measured cutting forces and optimization methods including genetic algorithm and particle swarm optimization to find the suitable J-C parameters. Force simulation and experiments were conducted to validate the proposed model and the results showed its effectiveness in estimating the J-C parameters directly from milling tests as an oblique cutting operation. Chip morphology has also been investigated to determine the mechanics of chip formation and its relationship to the properties of the AM titanium.
Model based simulation of broaching operation: cutting mechanics, surface integrity, and process optimization
(2013-04-01) Hosseini, Sayyed Ali; Kishawy, Hossam A.
Machining operations are widely used to produce parts with different shapes and complicated profiles. As a machining operation, broaching is commonly used for the machining of a broad range of complex internal and external profiles either circular or non-circular such as holes, keyways, guide ways, and slots on turbine discs having fir-tree shape. Broaching is performed by pushing or pulling a tapered tool through the workpiece to remove the unwanted material and produce the required profile. Broaching is also acknowledged because of its high productivity and attainable surface quality in comparison to the other machining processes. The objective of this thesis is to simulate the broaching operation and use the results to present a methodology for optimum design of the broaching tools. In the course of the presented thesis, a new B-spline based geometric model is developed for broaching cutting edges followed by model validation using 3D ACIS modeller. To study the mechanics of cutting and generated cutting forces during broaching operation, an energy based force model is presented which can predict the cutting forces based on the power spent in the cutting system. An experimental investigation is conducted in order to confirm the estimated forces. The integrity of the broached surface is also investigated by focusing on surface roughness, subsurface microhardness, and subsurface microstructure as three major parameters of surface integrity. An optimization procedure for broaching tools design is presented in this thesis. A mathematical representation of broaching tooth geometry is also presented which is used to simulate the tooth as a cantilevered beam subjected to a distributed load. The beam is solved considering the given design constraints to achieve optimum geometric parameters for maximum durability and performance.