Dr. Mason conducts his research in the Solid Mechanics Laboratory at Fitzpatrick Hall of Engineering.

Current Research

Biomechanics and Biomaterials in Orthopaedics Website

Development and Characterization of Orthopedic Biomaterials

Minimally invasive orthopedic implants, (MIOI), place new demands on orthopedic biomaterials and, thus, will generate the need for many new materials that can perform under high loading conditions in the human body, such as in the spine or at a hip joint, but can be adapted to minimally invasive procedures. In this work, we are examining traditional orthopedic materials, such as PMMA bone cement, as well as composite materials and hydrogels for use in orthopedic implants. The work focused on several aspects of these materials and their use in MIOI. While strength and stiffness are of primary interest, so are curing temperatures and viscosity. A broad range of materials characterization and modelling techniques are used to examine and optimize newly formulated materials.

Mechanisms and Effects of Heat Generation During High Speed Machining

Under dynamic loading conditions, such as those seen in high speed machining, most of the plastic work in metals is converted to heat. Given the short loading times involved, however, the materials are not cooled by any of the usual cooling mechanisms (conduction, convection or radiation), and, consequently, a significant temperature rise in the material results. At higher temperatures most materials soften, and an instability can occur when softened material deforms more rapidly than the bulk material leading to a shear localization. The objective of this work is to investigate the mechanics and materials aspects of shear localization mechanisms in high speed machining using split Hopkinson bar and high speed infrared temperature measurement. The ultimate goal is to provide better understanding of heat generation and shear localization in high speed orthogonal cutting so that chip formation in such processes may be controlled through alloy design.

Thermomechanical Solder Fatigue under Complex Loading Conditions

It is well known that in harsh environments, such has those experienced near the drive train of an automobile, the solder joints in printed circuit boards can experience a combination of thermal AND mechanical cycling. However, the mechanical component of the cycling, which comes from thermal expansion of the mounting device, buckling of the constrained board or loading of nearby small components by larger components, is often ignored. Standard testing utilizes pure thermal cycling alone to assess the reliability of the solder joints. In this study, we examine combined mechanical and thermal cycling to examine the effects of the additional mechanical load on the expected cyclic life and reliability of the solder-joint/component assembly. This work is in close collaboration with Delphi Automotive in Kokomo, IN.

Selected Recent Publications

Y. Zhou, C.Li, J.E. Renaud, and J. J. Mason, "Improvement of Mechanical Properties of Bone Cement by Shape Optimization of Short Fibers," to appear in Engineering Optimization.

Jennifer L. Schriefer, Alexander G. Robling, Stuart J. Warden, Adam J. Fournier, James J. Mason, Charles H. Turner, "A comparison of mechanical properties derived from multiple skeletal sites in mice," to appear in J. Biomechanics.

S.P. Kotha, C. LI, S.R. Schmid, and J. J. Mason, "Fracture Toughness of Steel Fiber Reinforced Bone Cement," to appear in J. Biomedical Materials Research Part A.

C. Li, S.R. Schmid, J. J. Mason, "Effects of Pre-cooling and Pre-heating Procedures on Cement Polymerization and Thermal Osteonecrosis in Cemented Hip Replacements," Medical Engineering and Physics, 25, no. 7, pp. 559-564, 2003.

K. Vernaza-Peña, J.J. Mason and M. Li, "High-Speed Temperature Measurements in Orthogonal Cutting of Aluminum," Experimental Mechanics, 42, no. 2, pp. 221-229, 2002.

Direct comments, questions, and corrections to amedept@nd.edu