Crashworthiness and High Strain Rate Material Testing Test Development for Vehicle Crash Conditions Motivation: The current vehicle design approaches result in overdesigned components in order to compensate for the uncertainties in the crush deformation and failure mechanisms. Reducing uncertainties in component design greatly improves the overall vehicle system reliability. The improvement in system reliability then directly translates into weight savings, especially for new materials. Research Objectives: Provide enabling technologies for use of lightweight materials in automobiles by development of: High rate experiments Methods for characterization of material properties during crash Databases of material properties Constitutive models for FEM simulations Technology transfer to OEM and part suppliers Material Characterization and Technology Transfer Vehicle Crashworthiness Progressive crush of high strength steel and magnesium alloy tubes. The crush modes are completely different and require entirely different approaches for material characterization and modeling. Crash tests and simulations are used for all vehicle classes to optimize design and safety performance. Tests at crash train rates (10/s to 1000/s) result in multiple wave reflections in the system which are difficult to control. Tests have not been standardized yet. Digital Imaging System for 3D Full field strain measurements for strains from 50 μeps to 2000% Up to 1,000,000 fps Versatility and convenience Combined with contact measurements Conventional technology New system Material testingComponent testing We have developed unique expertise for material and component testing at automotive crash speeds. Hydraulic equipment with tight control. We combine multiple measurement techniques for the same data. Tests are combined with simulations to verify measurements and design tests. Tension test at 500/s strain rate Tension test at 100/s strain rate Tension test with data measurement in the localization area. Optical and electronic microscopes are used to characterize internal structures and property deterioration with strain and strain rate. Test data is used to develop material parameters and constitutive models. Interpretation is enabled by modeling and computational data processing. Internal structure evolution with loading. AHSS Mg alloy Measurement of porosity in the material. Porosity is used as a parameter in the constitutive model. Project data is distributed to industrial collaborators and general public via World Wide Web interactive databases.

Computational Modeling of Materials and Structures Structural Modeling and Optimization Development of Parallel Computer Codes for Simulation of Coupled Physics Phenomena Composite Materials Modeling Large scale crash simulations were used to optimize design of new stainless steel bus design that is 50% lighter than the conventional designs. The prototype has been built by Autokinetics, Inc. We have developed constitutive models for glass and carbon fiber composites and implemented them into FEM crash codes. The material models are used for design of vehicle prototypes. Composite vehicle crash test verification Area under curves is proportional to crash energy dissipation. Applications in fibers and fabrics, elctrospinning We have developed programs to simulate composite manufacturing process and fibrous 3-D structure. Code computes distribution of contacts, voids, segment lengths, fiber undulation, layers, etc. The program can simulate fiber deposition patterns, orientations, fiber types, layers, network densities, and thicknesses. We focus on development of testing and modeling technologies for high strain rate deformation of advanced materials. Research includes partnering with industry and academia and utilization of High Performance Computing resources at NCCS. We are developing collaboration tools for material systems analysis, interpretation and synthesis of experiments and modeling. Optimization of material distribution in lightweight steel vehicle A new multi-lab effort on the development of the next generation nuclear fuel code. The code couples thermo-mechanics, neutronics, chemistry, chemical species transport, reactor fluid thermodynamics, and provides mechanisms for integration with detailed multiscale models. The code is applicable to general material processing and performance modeling. The code uses parallel computing to enable coupled multi-physics simulations at the spatial and time resolutions of interest. Coarse resolution (100 μm) simulation Coarse resolution (100 μm) simulation Fine resolution (10 μm) simulation Fine resolution (10 μm) simulation Number of cores 330M problem Scaling up to 6000 cores of XT4 at 20% peak efficiency (> 6 TFlops) Coupled thermal-chemistry model