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Technical Paper

Combined Synchrotron X-Ray Diffraction and Digital Image Correlation Technique for Measurement of Austenite Transformation with Strain in TRIP-Assisted Steels

The strain-induced diffusionless shear transformation of retained austenite to martensite during straining of transformation induced plasticity (TRIP) assisted steels increases strain hardening and delays necking and fracture leading to exceptional ductility and strength, which are attractive for automotive applications. A novel technique that provides the retained austenite volume fraction variation with strain with improved precision is presented. Digital images of the gauge section of tensile specimens were first recorded up to selected plastic strains with a stereo digital image correlation (DIC) system. The austenite volume fraction was measured by synchrotron X-ray diffraction from small squares cut from the gage section. Strain fields in the squares were then computed by localizing the strain measurement to the corresponding region of a given square during DIC post-processing of the images recorded during tensile testing.
Technical Paper

Effects of Condenser Two-Phase Flow Characteristics on a Capillary Pumped Loop

One of the intrinsic characteristics found in CPL operation is the oscillatory behavior of the pressure drop, even noted under seemingly steady operation. This study focused on the role of the condensing process and its intrinsic instabilities upon the differential pressure oscillations recorded in the CPL. Through an analytical study of condensing instabilities and an experimental study based on the correlation between pressure records and condensing flow visualization, the impact of slug flow phenomenon occurring in the condensing path was investigated. High amplitude oscillations were seen to be linked with liquid slug phenomena in the way that slug striking the final vapor-liquid interface generated pressure pulses.
Technical Paper

Detection of Presence and Posture of Vehicle Occupants Using a Capacitance Sensing Mat

Capacitance sensing is the technology that detects the presence of nearby objects by measuring the changes in capacitance. A change in capacitance is triggered either by a change in the dielectric constant, area of overlap or the distance of separation between the electrodes of the capacitor. It is a technology that finds wide applications in touch screens, proximity sensing etc. Drawing motivation from such applications, this paper investigates how capacitive sensing can be employed to detect the presence and posture of occupants in vehicles. Compared to existing solutions, the proposed approach is low-cost, easy to deploy, and effective. The sensing system comprises a capacitance-sensing mat which is embedded with copper foils that are arranged in rows and columns to form several touch-nodes across its surface. The system segregates row and column capacitances from each other and computes their tensor product to generate a grayscale capacitance-sensing image.
Technical Paper

Modeling and Learning of Object Placing Tasks from Human Demonstrations in Smart Manufacturing

In this paper, we present a framework for the robot to learn how to place objects to a workpiece by learning from humans in smart manufacturing. In the proposed framework, the semantic event chain (SEC) is implemented to identify the general object-action-location relationships. The Generalized Voronoi Diagrams (GVD) is used to determine the relative position and orientation between the object the corresponding mount. In the learning phase, we keep tracking the image segments in the human demonstration. For the moment when a spatial relation of some segments are changed in a discontinuous way, the state changes are recorded by the SEC, while the relative position and orientation of the object and the corresponding mount are presented by GVD. When the object or the relative position and orientation between the object and the workpiece are changed, the GVD, as well as the shape of contours extracted from the GVD, are also different.
Technical Paper

Strain Rate Effect on Martensitic Transformation in a TRIP Steel Containing Carbide-Free Bainite

Adiabatic heating during plastic straining can slow the diffusionless shear transformation of austenite to martensite in steels that exhibit transformation induced plasticity (TRIP). However, the extent to which the transformation is affected over a strain rate range of relevance to automotive stamping and vehicle impact events is unclear for most third-generation advanced high strength TRIP steels. In this study, an 1180MPa minimum tensile strength TRIP steel with carbide-free bainite is evaluated by measuring the variation of retained austenite volume fraction (RAVF) in fractured tensile specimens with position and strain. This requires a combination of servo-hydraulic load frame instrumented with high speed stereo digital image correlation for measurement of strains and ex-situ synchrotron x-ray diffraction for determination of RAVF in fractured tensile specimens.