Providing learning opportunities by designing a split hopkinson pressure bar

Abstract

Senior students are always challenged to apply their engineering knowledge and research skills gained from an engineering curriculum toward design and implementation of challenging senior design projects. Split Hopkinson pressure bar is an apparatus that is used to study materials behavior under high speed deformation, where strain rate is very high. Hopkinson bars are usually custom made based on the needs of customers, who are mostly researchers in universities or research labs. In this work, the authors provided learning opportunities for engineering students to design a small size low cost split Hopkinson pressure bar in a form of senior design project. The objectives of this project are to engage a student: 1) to design a well-structured Hopkinson bar by means of fundamentals of mechanics and finite element simulation 2) to build a working prototype of the apparatus for future research activities; and 3) to develop high speed deformation experiments for instructional purposes. The designed Split Hopkinson bar consists of two metallic bars with a specimen placing in between, a striker assembly, an air compressor, an instrumentation and data acquisition system. The experiments for using the split Hopkins pressure bar are conducted as an impact is made by the striker on one of the bars, which generates stress wave through the specimen and the other bar. During the experiments, strain in specimen is determined by measuring strains on the bars using strain gauges mounted on the bars. The student implemented the fundamentals of mechanics to design the apparatus. The student also built the solid model of the apparatus using CAD software and validated the design by extensive finite element simulation. A working prototype was physically built and tested. Preliminary tests demonstrate that the performance of the apparatus is as desired. In this paper, the authors elaborate on how the student have utilized the extensive engineering knowledge acquired throughout the course to design and develop this Hopkinson pressure bar and thus the educational gains achieved. This work is supported by an NSF's CMMI (Civil, Mechanical and Manufacturing Innovation) program. © American Society for Engineering Education, 2013.