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You searched for subject:(Vibration mechanisms). Showing records 1 – 2 of 2 total matches.

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University of North Texas

1. Rose, Kyle. Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate.

Degree: 2020, University of North Texas

An in-depth study of Al2W3O12 negative thermal expansion (NTE) ceramic was performed, focused on synthesis, phase mappings, and the underlying mechanisms shown to be responsible for NTE. Review of the literature has shown inconsistencies in reported values of the dilatometry measured coefficients of thermal expansion, and the temperature for the known monoclinic to orthorhombic phase transition. Two synthesis techniques are introduced: an ionic-liquid non-hydrolytic sol-gel synthesis route; and a low temperature solid state reaction synthesis for Al2W3O12. X-ray diffraction, Raman spectroscopy, and attenuated total reflectance Fourier-transform infrared spectroscopy (ATR-FTIR) were used to verify the techniques. Two differential scanning calorimetry (DSC) experiments (high and low temperature) were performed on the material showing the transition between -5 and -20 °C and no other phase changes until a reported degradation above 1100 °C. Extensive dilatometry on the material led to the discovery of elastic transitions occurring in the polycrystalline sample capable of explaining the inconsistencies in reported dilatometry results. This is further developed into a proposed model defining the regions between these transitions. Each region has a different thermal expansion as well as a direct effect on the reaction of the material upon cooling. This proposed model may allow more consistent reporting of dilatometry results for NTE materials. Raman spectroscopy was performed from 25-725 °C on the material showing both a joining in the tungsten-oxygen bending modes as well as a broadening in the tungsten-oxygen stretching modes. This is consistent with Al-O-W angle changes along the same temperature range reported in literature as well as the transverse vibrational modes responsible for NTE. Advisors/Committee Members: Reidy, Rick, Scharf, Thomas, Du, Jincheng.

Subjects/Keywords: Negative Thermal Expansion; Synthesis; Dilatometry; High Temperature Raman; Al2W3O12; A2M3O12; Vibration mechanisms

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Rose, K. (2020). Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate. (Thesis). University of North Texas. Retrieved from https://digital.library.unt.edu/ark:/67531/metadc1703275/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16th Edition):

Rose, Kyle. “Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate.” 2020. Thesis, University of North Texas. Accessed October 30, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703275/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Rose, Kyle. “Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate.” 2020. Web. 30 Oct 2020.

Vancouver:

Rose K. Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate. [Internet] [Thesis]. University of North Texas; 2020. [cited 2020 Oct 30]. Available from: https://digital.library.unt.edu/ark:/67531/metadc1703275/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Rose K. Synthesis, Phase Development, and the Mechanism for Negative Thermal Expansion in Aluminum Tungstate. [Thesis]. University of North Texas; 2020. Available from: https://digital.library.unt.edu/ark:/67531/metadc1703275/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation


University of Toronto

2. Mahmoodi, Masih. Structural Dynamic Modeling, Dynamic Stiffness, and Active Vibration Control of Parallel Kinematic Mechanisms with Flexible Linkages.

Degree: PhD, 2014, University of Toronto

This thesis is concerned with modeling of structural dynamics, dynamic stiffness, and active control of unwanted vibrations in Parallel Kinematic Mechanisms (PKMs) as a result of flexibility of the PKM linkages. Using energy-based approaches, the structural dynamics of the PKMs with flexible links is derived. Subsequently, a new set of admissible shape functions is proposed for the flexible links that incorporate the dynamic effects of the adjacent structural components. The resulting mode frequencies obtained from the proposed shape functions are compared with the resonance frequencies of the entire PKM obtained via Finite Element (FE) analysis for a set of moving platform/payload masses. Next, an FE-based methodology is presented for the estimation of the configuration-dependent dynamic stiffness of the redundant 6-dof PKMs utilized as 5-axis CNC machine tools at the Tool Center Point (TCP). The proposed FE model is validated via experimental modal tests conducted on two PKM-based meso-Milling Machine Tool (mMT) prototypes built in the CIMLab.For active vibration control of the PKM linkages, a set of PZT transducers are designed, and bonded to the flexible linkage of the PKM to form a "smart link". An electromechanical model is developed that takes into account the effects of the added mass and stiffness of the PZT transducers to those of the PKM links. The electromechanical model is subsequently utilized in a controllability analysis where it is shown that the desired controllability of PKMs can be simply achieved by adjusting the mass of the moving platform. Finally, a new vibration controller based on a modified Integral Resonant Control (IRC) scheme is designed and synthesized with the "smart link" model. Knowing that the structural dynamics of the PKM link undergoes configuration-dependent variations within the workspace, the controller must be robust with respect to the plant uncertainties. To this end, the modified IRC approach is shown via a Quantitative Feedback Theory (QFT) methodology to have improved robustness against plant variations while maintaining its vibration attenuation capability. Using LabVIEW Real-Time module, the active vibration control system is experimentally implemented on the smart link of the PKM to verify the proposed vibration control methodology. Advisors/Committee Members: James, K. Mills, Mechanical and Industrial Engineering.

Subjects/Keywords: Active Vibration Control; CNC Machine Tool; meso-Milling; Parallel Kinematic Mechanisms; Piezoelectric Actuators; Structural Dynamic; 0548

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Mahmoodi, M. (2014). Structural Dynamic Modeling, Dynamic Stiffness, and Active Vibration Control of Parallel Kinematic Mechanisms with Flexible Linkages. (Doctoral Dissertation). University of Toronto. Retrieved from http://hdl.handle.net/1807/68268

Chicago Manual of Style (16th Edition):

Mahmoodi, Masih. “Structural Dynamic Modeling, Dynamic Stiffness, and Active Vibration Control of Parallel Kinematic Mechanisms with Flexible Linkages.” 2014. Doctoral Dissertation, University of Toronto. Accessed October 30, 2020. http://hdl.handle.net/1807/68268.

MLA Handbook (7th Edition):

Mahmoodi, Masih. “Structural Dynamic Modeling, Dynamic Stiffness, and Active Vibration Control of Parallel Kinematic Mechanisms with Flexible Linkages.” 2014. Web. 30 Oct 2020.

Vancouver:

Mahmoodi M. Structural Dynamic Modeling, Dynamic Stiffness, and Active Vibration Control of Parallel Kinematic Mechanisms with Flexible Linkages. [Internet] [Doctoral dissertation]. University of Toronto; 2014. [cited 2020 Oct 30]. Available from: http://hdl.handle.net/1807/68268.

Council of Science Editors:

Mahmoodi M. Structural Dynamic Modeling, Dynamic Stiffness, and Active Vibration Control of Parallel Kinematic Mechanisms with Flexible Linkages. [Doctoral Dissertation]. University of Toronto; 2014. Available from: http://hdl.handle.net/1807/68268

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