278 research outputs found
Computational modeling of indentation of materials
Get PDFThis thesis focusses on computational modeling of several different indentation problems involving the microindentation, nanoindentation and reference point indentation (RPI). The goal of this thesis is to develop better understanding of indentation processes in different materials utilizing numerical methods.
Indentation has been used for a long time for characterizing hardness of materials. Nanoindentation is a technique where a micron scale indenter is forced into a material of interest while monitoring load and displacement. Indentation techniques can be used to measure elastic modulus, hardness and viscoelastic properties of materials. The RPI technique uses a reference probe which sits on the surface of substrate and defines datum for test probe. The test probe indents the substrate multiple times using a cyclic load and computes nine different RPI outputs. The RPI outputs are not completely understood and there is a need for more research.
This thesis presents four different studies.
The first study deals with experimental and numerical investigation of indentation on Cr(Mo)-NiAl eutectic alloy. More specifically, the depth dependent strain partitioning between the layers of NiAl layered structure was measured using X-Ray microdiffraction. Finite element simulations were conducted to evaluate thermal strains due to cooling. Results from this simulation were further utilized to model microindentation of the eutectic composite. Strain data from simulations were compared with experimental results confirming experimentally observed trends.
The second study deals with simulation of RPI on bone. Bone was modeled as a material that exhibits elastic, plastic, viscous and continuum damage behaviors. The RPI process was simulated as a cyclic indentation process using a finite element package Abaqus®. Effects of changing material properties, indentation force and number of cycles on the RPI outputs were evaluated computationally and compared with experimental works of similar nature and good coherence was demonstrated.
Third study presents a statistical approach to study the RPI outputs. Various mechanical tests (compression tests, stress relaxation test, tensile tests) were conducted on multiple 3D printed polymers and properties were obtained. These properties were analyzed against the RPI data of polymers in order to find correlations. The study is currently ongoing and data collected till date is presented in this thesis.
Fourth study presents a fast and efficient way of characterizing viscoelastic properties of soft materials based on experimental nanoindentation data and viscoelastic indentation tool on Nanohub. PMMA (polymethyl methacrylate) was subjected to nanoindentation to obtain experimentally time-displacement data. This data along with experimental parameters (loading time, force and indenter radius) serve as inputs to the Nanohub viscoelastic simulation tool. This tool can provide 3 or 5 viscoelastic constants for materials, assuming a Standard Linear Solid model for solids. Numerical data from simulations was matched against experimental data for two different loading rates and good match was observed.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2017-05-01The student, Vineet Agarwal, accepted the attached license on 2015-04-29 at 16:12.The student, Vineet Agarwal, submitted this Thesis for approval on 2015-04-29 at 16:16.This Thesis was approved for publication on 2015-05-01 at 12:56.DSpace SAF Submission Ingestion Package generated from Vireo submission #8195 on 2015-07-22 at 14:26:36Made available in DSpace on 2015-07-22T22:46:08Z (GMT). No. of bitstreams: 3
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Previous issue date: 2015-05-01Embargo set by: Seth Robbins for item 80039
Lift date: 2017-07-22T22:46:21Z
Reason: Author requested closed access (OA after 2yrs) in Vireo ETD systemLimited Restriction Lifted for Item 80039 on 2017-07-23T09:15:12Z
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Citizen-led Work using Social Computing and Procedural Guidance
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Method and system for managing a technical installation
No full textA method (300) and system (101) for managing a technical installation (108) are disclosed. In one aspect of the invention, an event associated with at least a portion of the technical installation (108) is detected based on sensor data associated with the portion of the technical installation (108). In another aspect of the invention, a representative view (1101) of the portion of the technical installation (108) is rendered on at least one wearable device (107a-c), wherein the representative view (1101) displays information associated with the detected event in conjunction with the multi-dimensional view of the portion of the technical installation (108). In yet another aspect of the invention, a predictive time series analysis of the sensor data associated with the detected event is generated. In another aspect of the invention, the predictive time series analysis in conjunction with the representative view (1101) of the at least one portion of the technical installation (108) is displayed.Interactive Intelligenc
Nanoparticles mediated folic acid enrichment
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Crop-Growth Driven Forward-Modeling of Sentinel-1 Observables Using Machine-Learning
No full textThis paper presents an approach to implement a forward model for Sentinel-1 copol and crosspol backscatter and coherence using crop bio-geophysical parameters namely leaf area index, biomass, canopy height, soil moisture and root zone moisture as inputs for the maize. These required input parameters are generated using Decision Support System for Agrotechnology Transfer (DSSAT), one of the state-of-the-art crop growth models. The predicted SAR signal is generated using Support Vector Regression (SVR) over all the maize fields in an agricultural region, Flevoland, Netherlands. The correlation between simulated signal and observed signal is evaluated.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Mathematical Geodesy and Positionin
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