Phillip Cornwell

Enhancing Power Harvesting using a Tuned Auxiliary Structure

Future, self-contained sensors and processing units will need onboard, renewable power supplies to be truly autonomous. One way of supplying such power is through energy harvesting, a process by which ambient forms of energy are converted into electricity. One energy harvesting technique involves converting kinetic energy, in the form of vibrations, into electrical energy through the use of piezoelectric materials. This study examines the use of auxiliary structures, consisting of a mechanical fixture and a lead zirconate/lead titanate (PZT) piezoelectric element, which can be attached to any vibrating system. Adjusting various parameters of these structures can maximize the strain induced in the attached PZT element and improve power output.

Teaching dynamics using interactive tablet PC instruction software

Is there an advantage of using interactive tablet PC software as opposed to more traditional teaching methods? This work is an innovative use of tablet PC technology to teach an introductory dynamics course. Each student in the classroom used a tablet PC as did the instructor. In addition to using the tablet PCs, each lecture was recorded using screen capture and made available on-line. The first goal of this project was to provide students with better resources outside of class. The second goal was to try to better engage students using active learning exercises on the tablet PCs during class. A post course survey was used to help assess the effectiveness of the new teaching media.

Peri-prosthetic fracture vibration testing

The purpose of this study was to establish a test setup and vibration analysis method to predict femoral stem seating and prevent bone fracture using accelerometer and force response data from an instrumented stem and impactor. This study builds upon earlier studies to identify a means to supplement a surgeon’s tactile and auditory senses by using damage identification techniques normally used for civil and mechanical structures. Testing was conducted using foam cortical shell sawbones prepared for stems of different geometries. Each stem was instrumented with an accelerometer. Two impactor designs were compared: a monolithic impactor and a twopiece impactor, each with an integrated load cell and accelerometer. Acceleration and force measurements were taken in the direction of impaction. Comparisons between different methods of applying an impacting force were made, including a drop tower and a surgical hammer. The effect of varying compliance on the data was also investigated. The ultimate goal of this study was to assist in the design of an integrated portable data acquisition system capable of being used in future cadaveric testing. This paper will discuss the experimental setup and the subsequent results of the comparisons made between impactors, prosthetic geometries, compliances, and impact methods. The results of this study can be used for both future replicate testing as well as in a cadaveric environment.

Fiber Optic Strain Gage Verification and Polyethylene Hip Liner Testing

To optimize stability in total hip arthroplasty, the use of larger femoral heads necessitates a polyethylene liner of reduced thickness. An understanding of the mechanical properties, particularly resistance to fatigue failure, of highly-crosslinked polyethylene is critical to determine the optimal parameters for clinical use. The primary purposes of this study were to characterize the X3TM highly cross-linked polyethylene (HCLPE) liner peripheral face strain field in multiple orthopaedic acetabular shell constructs under physiological loading and to evaluate the usefulness of fiber optic strain gages in this type of biomedical application. The first phase of this study involved measuring X3 HCLPE material properties in tension and compression using uniaxial fiber optic strain gages and resistance based uniaxial and multi-axial (rosette) strain gages to gain greater insight into the complexities and limitations of the use of fiber optic strain gages with X3 HCLPE. In the second phase, physical testing was used to evaluate the effect of HCLPE thickness on the hoop strain field of liner samples of three different thicknesses at three inclination angles and three head offsets that simulate potential in vivo clinical scenarios occurring in hip replacement. The results from these studies will be presented in this paper.

Fast Forward-an adventure in engineering for 7th and 8th grade girls

Fast Forward is an exciting program that has been developed at Rose-Hulman Institute of Technology to address the problems of the disproportionately high number of girls who lose interest in science during middle school and the low number of women who enroll in college prep science and math courses in high school. Fast Forward is an intensive four day immersion into the world of science and technology. Thirty young women attended the pilot program during the summer of 1994. The program included exciting and educational technical sessions in which the primary pedagogical technique was active learning. There were hands on chemistry and physics experiences and in several sessions the students used computers as a tool to solve problems. The cornerstone of Fast Forward was a project that required the young women to design, construct and test a solar powered vehicle. The student response from the pilot program was overwhelmingly positive. The details of the program, the program content, and the results of the assessment are presented.

Advances in hands-on experiments and simulations for an introductory Dynamics Course

The Mechanical Engineering faculty of Rose- Hulman Institute of Technology have devised a series of virtual and hardware experiments designed to enhance student confidence in kinematic and kinetic models, to reduce reliance on intuition, and to show the strengths and weaknesses of computer based models. By leveraging precisely instrumented mechanical systems intended for controls education, we are able to provide brief but significant experiences in experimental mechanics. In this paper, these laboratory experiences will be described, and assessment results will be presented.

Implementing a program to motivate math and science grade school classrooms

Mechanical engineering students from Rose-Hulman Institute of Technology have been visiting elementary school classes, grades 4-6, to expose the children to engineering as a career option, to motivate the use of math and science, and to emphasize the importance of a good education. The 1993-94 school year will be the third year for this program. In the programs first two years, mechanical engineering students made presentations to approximately 80 elementary school classes each year, reaching several thousand students. The presentations consist of demonstrations and hands-on activities. The first two years of the program were administered by the faculty advisor to the Rose-Hulman student section of the American Society of Mechanical Engineers, but the administration of the program is to be turned over to the students for the 1993-94 school year.<<ETX>>