Seminar: Constitutive Modeling of Lightweight Materials

Abstract

The application of lightweight metals and polymer composites is fast becoming prevalent in automotive, defense, energy and other manufacturing industries. Using thinner sheet metals with high strengths is one of the most effective ways for automotive companies to make cars that meet the CAFÉ standard requiring an average of 54.5 MPG by 2025. In the defense industry lightweight metals and carbon fiber reinforced polymer composites are being used to make strong yet lightweight armor vehicles and protective gears for soldiers.  The complex microstructures of lightweight materials gives them their superb mechanical properties. The same complex microstructures, however, makes prediction of their behavior and failure limits more complicated, requiring the development and application of microstructure-sensitive constitutive models.

In the first part of my presentation, I will briefly review macroscopic and microstructure-sensitive material models. Phenomenological yield functions are suitable for modeling the macroscale anisotropic behavior of metals, and depending upon their formulation require anywhere from a few up to a dozen or more experimental data for parameter characterization.  The microstructure-sensitive crystal plasticity (CP) model requires for input the initial texture of the metal, the appropriate slip systems representing the type of metal (FCC, BCC, HCP, BCT), and the hardening parameters for each slip system. As output, the CP model predicts the total plastic deformation, shear rate for each slip system, and the texture evolution (anisotropy).  Some examples in which yield functions and the CP model were applied to predict the deformation of lightweight metals, such as 6061-T4 aluminum and AHSS (BAO QP980), will be discussed.

In the last part of my presentation, I will briefly introduce microstructure-sensitive material models for fiber-reinforced thermoplastic (FRT) composites and nanocomposites. The concept of anisotropy in FRT composites, their experimental characterization, and the phenomenological model developed to predict their mechanical properties will be briefly discussed.  For polymer nanocomposites, the steps required to develop a statistically equivalent representative volume element (RVE) for them will be briefly explained. The presentation will conclude by showing an example of the finite element simulation of forming FRT composite helmets, and predicting mechanical properties of nanocomposites.

About the Speaker

Dr. Farhang Pourboghrat joined the Ohio State University as Professor with joint appointments in the Integrated Systems Engineering (ISE) and the Mechanical and Aerospace Engineering (MAE) Departments to work closely with the Center for Design and Manufacturing Excellence (CDME). He earned his BS and MS degrees from the University of Iowa, and the PhD degree in Mechanical Engineering from the University of Minnesota. From 1990 to 1998, Farhang worked as a staff scientist at the Alcoa Technical Center. In 1998, he joined the Mechanical Engineering Department at Michigan State University as an assistant professor, and was promoted to the rank of Professor in 2009. Dr. Pourboghrat’s research interests are in the multi-scale characterization of engineered materials and modeling of advanced forming processes, including warm forming of sheet metals and tube hydroforming.  His research has a strong emphasis on the computational modeling of metal forming processes using crystal plasticity and advanced phenomenological yield functions. His current research involves characterization and modeling of aluminum alloys, niobium, tin, and third generation advanced high strength steel (3GAHSS). In addition, he develops multi-scale material models for the simulation of draping of polymer composite sheets reinforced with glass, bio and carbon fibers, clay nanotube, and graphene nano-platelets. His research has been extensively funded by NSF, DOE, DOD and automotive industry. He has published extensively in the International Journal of Plasticity, and his research work is internationally recognized. He currently holds 4 US patents and another one is under review. Dr. Pourboghrat is a member of the American Society of Mechanical Engineers (ASME), and the Sigma Xi technical honor society. He has served as a member of the steering and scientific committee for the Numerical Simulation of 3D Sheet Forming Processes (NUMISHEET) conference since 2005.

Hosted by Professor Tony Luscher.