John Podhiny
Program Manager
Education
B.E., Mechanical Engineering, Villanova University, May 2000
M.E., Mechanical Engineering, Villanova University, December 2004
Ph.D. Student, Engineering, Villanova University, Anticipated Completion 2012
Experience
Mr. Podhiny has nearly nine years of experience in thermal-structural analysis and design, most recently with a focus on advanced finite element modeling. He joined MR&D in May of 1999 as a summer intern and accepted a position as a full-time engineer shortly after his graduation in May 2000. During his time at MR&D, he has worked on a variety of projects involving ceramic matrix composites (CMCs), carbon fiber composites, and oxide-oxide composites. These programs have involved advanced finite element modeling as well as calculation and correlation of composite material properties using fundamental micromechanics.
Mr. Podhiny’s primary current project is a finite element based integrated durability model that will provide life and failure predictions of C/SiC and SiC/SiC components based on operating stresses and the surrounding environment. Factors such as temperature, partial pressure of oxygen, and time history of these quantities will all be included to provide an estimate on the usable life of the CMC component. This model is being implemented within ABAQUS using a user-defined element subroutine UEL.
On another recent program, a finite-element-based mathematical model was developed to predict the thermal response and structural performance of Space Shuttle leading edge damage that has been repaired using NOAX. Mr. Podhiny was responsible for writing the thermal and structural material subroutines (UMATHT and UMAT) that define the material behavior. The thermal subroutine calculates the effective thermal properties of NOAX based on phase fractions, defines any required heat source terms, calculates the mass loss of each phase based on equations derived from TGA testing, and updates phase fractions accordingly. The primary output of interest from the thermal analysis includes transient temperature distributions and phase fractions for the entire NOAX repair. These results are entered directly into the subsequent structural analyses, where UMAT is used to calculate effective elastic properties and strengths, perform a linear elastic thermal stress analysis, and provide failure predictions for all NOAX elements. Failed elements are then plotted visually for assessment. Simulations of six arcjet test specimens showed temperature results and failure predictions that agreed well with measured data.
Mr. Podhiny is also currently working towards a Ph.D. in Engineering on a part-time basis, with a focus on thermal fluid sciences. He plans on completing this degree by the end of 2012.