Crystal plasticity model calibration for 316l stainless steel single crystals during deformation

Type 316L austenitic stainless steel is an important structural material used for the in-core components and pressure boundaries of light water reactors. In order to study degradation mechanisms in such a steel, like crack initiation and propagation, it is crucial to develop reliable crystal plasticity models at microscale that would account for anisotropic nature of the material and realistic modelling of grain topology. In this work we present a procedure for calibrating material properties of a slip-based crystal plasticity finite element model and investigate its suitability as a constitutive model for single-crystal tensile test simulations. The material properties include the anisotropic elastic and crystal plasticity material parameters that are calibrated against experimental tensile test curves for 316L stainless steel single crystals at selected crystallographic orientations. For the crystal plasticity material parameters a systematic sensitivity study using Bassani and Wu hardening law is performed

An Integrated Procedure for the Structural Design of a Composite Rotor-Hydrofoil of a Water Current Turbine (WCT)

This paper shows an integrated structural design optimization of a composite rotor-hydrofoil of a water current turbine by means the finite elements method (FEM), using a Serial/Parallel mixing theory (Rastellini et al. Comput. Struct. 86:879–896, 2008, Martinez et al., 2007, Martinez and Oller Arch. Comput. Methods. 16(4):357–397, 2009, Martinez et al. Compos. Part B Eng. 42(2011):134–144, 2010) coupled with a fluid-dynamic formulation and multi-objective optimization algorithm (Gen and Cheng 1997, Lee et al. Compos. Struct. 99:181–192, 2013, Lee et al. Compos. Struct. 94(3):1087–1096, 2012). The composite hydrofoil of the turbine rotor has been design using a reinforced laminate composites, taking into account the optimization of the carbon fiber orientation to obtain the maximum strength and lower rotational-inertia. Also, these results have been compared with a steel hydrofoil remarking the different performance on both structures. The mechanical and geometrical parameters involved in the design of this fiber-reinforced composite material are the fiber orientation, number of layers, stacking sequence and laminate thickness. Water pressure in the rotor of the turbine is obtained from a coupled fluid-dynamic simulation (CFD), whose detail can be found in the reference Oller et al. (2012). The main purpose of this paper is to achieve a very low inertia rotor minimizing the start-stop effect, because it is applied in axial water flow turbine currently in design by the authors, in which is important to take the maximum advantage of the kinetic energy. The FEM simulation codes are engineered by CIMNE (International Center for Numerical Method in Engineering, Barcelona, Spain), COMPack for the solids problem application, KRATOS for fluid dynamic application and RMOP for the structural optimization. To validate the procedure here presented, many turbine rotors made of composite materials are analyzed and three of them are compared with the steel one

Reconfigurable Flood Wall Inspired by Architected Origami

Recent interest in the art of origami has opened a wide range of engineering applications and possibilities. Shape changing structures based on origami have had a large influence on the drive for efficient, sustainable engineering solutions. However, development in novel macro-scale utilization is lacking compared to the effort towards micro-scale devices. There exists an opening for environmentally actuated structures that improve quality for life of humans and the natural environment. Specifically, resilient infrastructure systems could potentially benefit from the tailorable properties and programmable reconfiguration of origami-inspired designs. The realm of flood protection and overall water resources management creates a unique opportunity for adaptable structures. A flood protection system, or flood wall, is one application of the origami technique. In many situations, flood protection is visually displeasing and hinders an otherwise scenic natural environment within a cityscape. By applying a permanent, adaptable protection system in flood-prone areas, not only will general aesthetics be conserved, but quick deployment in disaster situations will be ensured. With a rapidly changing climate and an increase in storm disaster events, an efficient flood-protection system is vital. In this study, simple rigid flood barriers are compared to adaptable wall systems that utilize multi-stable configurations. The flood event is characterized by a surcharge of water that is suddenly introduced–like that of a flash flood–and sustained at steady-state. Small-scale prototypes are tested in a hydraulic flume and compared to a numerical simulation for validation.Ohio State University College of Engineering Undergraduate Research ScholarshipNo embargoAcademic Major: Civil Engineerin

Investigating dimensional and geometrical accuracy of isothermally forged blades

Compressor blades are one of the well-known products made of titanium alloys. They are usually manufactured by a forging process followed by a sequence of machining processes. Precision forging eliminates a considerable amount of machining; however, due to the close tolerances, the process should be designed in a manner to meet dimensional and geometrical tolerances as well as the desired mechanical and metallurgical properties. In this paper, effects of two main process parameters, the process temperature and strain rate, on the dimensional and geometrical accuracy of the isothermally forged blades are investigated experimentally. The results are analyzed by the response surface method (RSM). In order to justify the results and have a tool for further studies, a coupled thermo-mechanical finite element method model is developed and verified by the experimental results. The results show that the process temperature and pressing speed and their interaction have a meaningful effect on the thickness error; however, the interaction effect of the process temperature and pressing speed on the twist error is not considerable and moreover the bow error of the forged blades is not significant. Finally, the results show that for a given geometry, by selection of appropriate process parameters, a sound workpiece with acceptable dimensional and geometrical aspects can be manufactured without any need for a die shape compensation