2008 Dr. Alex Hills Engineering Research Award
Alex Bergeron - BSE, Mechanical Engineering: "Spinal Rod Fatigue Testing and Analysis"
Facutly Mentor: Anthony Paris, Engineering
Abstact: The objectives of the proposed study are to measure and compare the fatigue behavior of titanium and stainless steel alloys used for surgically implanted spinal rods and to publish the results for possible use by physicians, patients, engineers, and scientists. Orthopedic surgeons Andres Munk, M.D., is a collaborating researcher on the proposed study.
Medical patients with spinal injuries or conditions such as scoliosis, degenerative disc disease, spinal trauma or hernia(s) may require surgery to implant spinal rods to give the vertebra and spine needed structural support and to ensure proper bone growth. With movement, these rods are subjected to cyclical loading and fatigue, the primary cause of spinal rod failure. A person with a low intensity level of daily activity can easily walk one million steps and subject a spinal rod to one million loading cycles in six months. Over time, the cyclic loading can lead to fatigue crack initiation and gwoth and even fracture of the rod. For the physicians and patients considering spinal rod implants, there are three different metallic alloy rods available: titanium, stainless steel and vitallium. However, little has been published on the behavior of the alloys of their relative merits. By using fatigue crack growth rate testing, this study will provide a basis for the comparison of the fatigue behavior or the titanium and stainless steel rods.
The fatigue process will be initiated by introducing a circumferential pre-crack to the rod. Rotating bending fatigue will imitate the loading that a spinal rod experiences while implanted. One rotation will be considered to be one cycle and will simulate one walking step of a spinal rod patient. The load and number of cycles will be applied, and the amount of crack growth will be measured. To accurately measure crack growth, a technique called heat tinting will be used - when the alloy is heated to a moderately high temperature, the external surfaces of the alloy oxidize and change color. This will mark the initial crack length. After cycling, the specimen will be broken, and both the initial and final crack lengths will be measured. The amount of crack growth will be determined from the difference between the initial and final crack lengths. Testing will consist of varying the magnitude of the load and number of cycles.
The surgical spinal rods are expensive. To reduce costs, the rotating bending fatigue test protocol will be refined using common round bar stock specimens - the actual surgical spinal rod specimens will not be used until the test method is sufficiently refined to ensure the successful testing of each surgical spinal rod sample.
The fatigue crack growth rate will be correlated with the load, number of cycles, and crack length for each material. It is anticipated that the fatigue behavior will depend upon the metallic alloy. The results of the study will be useful to surgeons and patients considering spinal rod implantation and to engineers and scientists working in biomedicine.
2007 Dr. Alex Hills Engineering Research Award
Samantha Kay Tanner - BS, Geomatics: "An Evaluation of Undergraduate Surveying Education in Alaska"
Group Members: Melinda Willman (Geomatics) and Krysta Wojnowski (Geomatics)
Faculty Mentor: R.A. Curley, Geomatics
Abstract: An Associate Applied Sciences Degree in Surveying and Mapping was introduced at the University of Alaska in 1971 and a four year Bachelor of Science Degree in Surveying and Mapping was added in 1991. These programs were changed to an Associate Applied Science degree in Geomatics and a Bachelor of Science Degree in Geomatics in 1996 and a Certificate in Geographic Information Systems added in 2001. Since the introduction of the Geomatics offerings in 1996 there have been 375 declared majors in Geomatics but only 18% of the declared majors have successfully completed the program. The programs currently being offered are accredited by the Accreditation Board for Engineering and Technology (ABET) and are essential for students wishing to enter the profession of land surveying in the state of Alaska. There is currently a shortage of Professional Land Surveyors in the state of Alaska and the average age of the Professional Land Surveyor in Alaska is 58 years. Unless the retention and completion of the Geomatics programs can be improved there is likely to be a severe shortage of qualified land surveyors which will impede development and growth within the state.
This research seeks to determine the reasons for the low retention and completion rates and to suggest changes to the program that might bring an improvement in the rates, so the needs of the geospatial sciences industry in Alaska can be met to facilitate the growth in this sector of the economy.
2006 Dr. Alex Hills Engineering Research Award
Paul Bilodeau - BS, Mechanical Engineering: "Design of Compliant Mechanism for Planar Motion Amplification"
Faculty mentor: Nicolae Lobontiu
Abstract:
The project proposes to model, design and experimentally test several planar compliant mechanisms that are aimed at amplifying the input mechanical motion. Such compliant mechanisms use flexure hinges (which are slender, flexible portions that can bend and enable relative rotation between two adjacent rigid links) instead of classical rotation joints. They are modern devices being applied in precision positioning as well as in micro/nano electromechanical systems (MEMS/NEMS). The focus of this project will be on compliant mechanisms that have two stages of motion amplification wand which have double symmetry, realizing thus an amplified output motion which is parallel to the input one. Various flexure hinges (such as right-circular, corner-filleted and elliptic) will be implemented in these compliant mechanisms. Two models will be developed to assist with the subsequent design process. One simplified model will consider the flexure as being point-like, whereas the second model will be precise and will be based on the real dimensions and shape of the flexure hinges. Each model will predict the mechanical amplification (or advantage). Several compliant mechanisms will be selected from the model/analysis pool and execution drawings will be produced and sent via email to the company which will fabricate these mechanisms by electric discharge machining (EDM). The fabricated mechanisms will then be tested in the School of Engineering’s labs at UAA. A first round of testing will apply simple mechanical actuation and measuring of the input/output motion, whereas in a second testing set actuation by linear actuators (voice coils) will be used. The experimental results are going to be compared with the model data and conclusions will be derived with respect to the obtained results. The specific aims of this project are:
(a) Formulation of a simple model predicting the motion amplification by the two-stage flexure-based planar compliant mechanisms in the case the flexure hinges are considered point-like
(b) Formulation of an exact model for the motion amplification of these mechanisms by using real flexure hinges of various configurations (right-circular, corner-filleted, elliptic)
(c) Identification of a set of compliant mechanisms to be designed and tested, and production of execution drawings
(d) Experimental testing of the fabricated devices by using simple mechanical actuation and then electro-mechanical linear actuation through voice-coils
(e) Evaluation of model and experimental results and identification of causes for possible differences between the two methods
Jennifer Lane Jemison – BS Civil Engineering: "Tidal Basin Power Generator Project"
Faculty Mentor: Nyree McDonald
Abstract:
The world’s most predictable energy resource comes in the form of the ebbing and flooding of the tides. Every 12.5 hours the cycle repeats. It is this predictability that makes the concept of harnessing energy from the tides attractive. In recent years, the study of the energy of waves and tides has come to the forefront of energy engineering. Many methods have been designed and developed to change the mechanical energy of the moving water into electrical power. Some systems use the action of the waves, while others focus on the potential energy from the difference in the height of the tides. The Knik Arm has a 48ft difference in tidal heights, one of the larges in the world. This makes it a perfect place to pilot a system that exploits the potential energy locked within the tides. Before this can become a reality, a thorough study must be completed to determine the capacity and efficiency of a tidal basin power generation system for the Knik Arm near Anchorage, Alaska. First, a design must be completed to theoretically maximize electrical output. Second, a lab scale model should be built to experiment with the theoretical design. And last, the testing should be done to determine the potential output and efficiency of a tidal basin power generator.
