Date of Award

Spring 2015

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

First Advisor

Brad L Kinsey

Second Advisor

Ioannis P Korkolis

Third Advisor

Barry K Fussell

Abstract

Characterization of the evolving yield loci and forming limit diagrams for sheet materials under biaxial loading is necessary for the development of accurate sheet metal forming process simulations. Biaxial tension testing has been shown to have significant advantages over the current computational and experimental methods for such material characterization; however, the few commercially available loading frames are far too large and expensive to be practical for most metal forming research laboratories. To address this problem, the University of New Hampshire’s Mechanics, Materials, and Manufacturing Lab is working to design a practical servohydraulic biaxial loading frame for such metal forming laboratories. The physical system design, fabrication, and component selection was performed previously by a team of mechanical engineering seniors in collaboration with Greenerd Press and Machine Co. To continue the project, this thesis presents the design, implementation, and validation of a PLC-based control system and LabVIEW graphical interface for operating the biaxial loading frame. Experimental data shows that the displacement control system can accurately maintain equal displacement of opposing actuators to within 0.1[mm] for fixed position, 80[mm/min] ramp, and 0.2[Hz] sinusoidal profiles. The selection and mounting position of the hydraulic control valves were found to be the major limiting factor in the abilities of the control system. Preliminary uniaxial and biaxial tension tests with Al-6022-T4 show inconsistent stress-strain responses that cause differing force measurements of up to 8[%] between opposing load cells. The inconsistencies were attributed to the mechanical design of the current frame of the testing machine. Corresponding mechanical, hydraulic, and software/control design improvements are suggested, and plans for the future of the project are discussed.

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