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Xi Chen - One of the best experts on this subject based on the ideXlab platform.
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spherical Indentation Method for measuring local mechanical properties of welded stainless steel at high temperature
Materials & Design, 2013Co-Authors: Akio Yonezu, Hirotaka Akimoto, Shoichi Fujisawa, Xi ChenAbstract:Abstract Indentation Method was employed to evaluate the local mechanical properties of welded stainless steel at a high temperature of 320 °C. The welding process often changes the mechanical properties (in particular the plastic properties), and make the material property inhomogeneous. An Indentation Method was proposed to effectively evaluate the stress–strain relationship (approximated by the Ludwick-type hardening law) in the welded SUS316L at 320 °C. Functional relationship between the indention response and plastic property was established using finite element Method (FEM). The dimensional function was deduced based on sufficiently-deep Indentation, so that it can directly estimate plastic properties up to large uni-axial strain (about 20%). Spherical Indentation tests applied to welded SUS316L may enable the evaluation of the distribution of plastic properties, such as the yield stress, plastic strain and tensile strength. The properties around the welded area were estimated to be higher than the base material of SUS316L, owing to the local plastic deformation from welding-induced thermal expansion and construction. Parallel test was conducted to validate the model. The proposed Indentation technique can quantitatively evaluate the local mechanical properties at high working temperature, and supply useful information on inhomogeneous property distribution in materials.
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new sharp Indentation Method of measuring the elastic plastic properties of compliant and soft materials using the substrate effect
Journal of Materials Research, 2006Co-Authors: Manhong Zhao, Xi Chen, Nagahisa Ogasawara, Anghel Constantin Razvan, Norimasa Chiba, Dongyun Lee, Yong X GanAbstract:We propose a new theory with the potential for measuring the elastoplastic properties of compliant and soft materials using one sharp Indentation test. The Method makes use of the substrate effect, which is usually intended to be avoided during Indentation tests. For Indentation on a compliant and soft specimen of finite thickness bonded to a stiff and hard testing platform (or a compliant/soft thin film deposited on a stiff/hard substrate), the presence of the substrate significantly enhances the loading curvature which, theoretically, enables the determination of the material power-law elastic-plastic properties by using just one conical Indentation test. Extensive finite element simulations are carried out to correlate the Indentation characteristics with material properties. Based on these relationships, an effective reverse analysis algorithm is established to extract the material elastoplastic properties. By utilizing the substrate effect, the new technique has the potential to identify plastic materials with indistinguishable Indentation behaviors in bulk forms. The error sensitivity and uniqueness of the solution are carefully investigated. Validity and application range of the proposed theory are discussed. In the limit where the substrate is taken to be rigid, the fundamental research is one of the first steps toward understanding the substrate effect during Indentation on thin films deposited on deformable substrates.
Daining Fang - One of the best experts on this subject based on the ideXlab platform.
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high temperature fracture toughness and residual stress in thermal barrier coatings evaluated by an in situ Indentation Method
Ceramics International, 2018Co-Authors: Zhaoliang Qu, Qing He, Rujie He, Shixing Wang, Daining FangAbstract:Abstract High temperature fracture toughness and residual stress are important for the evaluation of TBCs. In this paper, an in-situ high temperature Indentation Method was originally developed to investigate the high temperature fracture toughness and residual stress in a typical TBC, nanostructured 8 wt% yttria partially stabilized zirconia (YSZ) coating. The cracks caused by in-situ high temperature Indentation tests were observed, and high temperature fracture toughness and residual stress were experimentally measured. The fracture toughness was measured to be 1.25, 0.91 and 0.75 MPa*m 1/2 at 25, 800 and 1000 °C, respectively. The residual stress was measured to be − 131.3, − 55.5 and − 45.5 MPa, correspondingly. Moreover, the residual stress and fracture toughness both decrease with increasing environmental temperature. It is also found that the fracture toughness without consideration of residual stress is significantly larger than the intrinsic fracture toughness, which may result from the compressive stress state.
Guozheng Kang - One of the best experts on this subject based on the ideXlab platform.
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oliver pharr Indentation Method in determining elastic moduli of shape memory alloys a phase transformable material
Journal of The Mechanics and Physics of Solids, 2013Co-Authors: Guozheng KangAbstract:Instrumented Indentation test has been extensively applied to study the mechanical properties such as elastic modulus of different materials. The Oliver–Pharr Method to measure the elastic modulus from an Indentation test was originally developed for single phase materials. During a spherical Indentation test on shape memory alloys (SMAs), both austenite and martensite phases exist and evolve in the specimen due to stress-induced phase transformation. The question, “What is the measured Indentation modulus by using the Oliver–Pharr Method from a spherical Indentation test on SMAs?” is answered in this paper. The finite element Method, combined with dimensional analysis, was applied to simulate a series of spherical Indentation tests on SMAs. Our numerical results indicate that the measured Indentation modulus strongly depends on the elastic moduli of the two phases, the Indentation depth, the forward transformation stress, the transformation hardening coefficient and the maximum transformation strain. Furthermore, a Method based on theoretical analysis and numerical simulation was established to determine the elastic moduli of austenite and martensite by using the spherical Indentation test and the Oliver–Pharr Method. Our numerical experiments confirmed that the proposed Method can be applied in practice with satisfactory accuracy. The research approach and findings can also be applied to the Indentation of other types of phase transformable materials. & 2013 Elsevier Ltd. All rights reserved.
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oliver pharr Indentation Method in determining elastic moduli of shape memory alloys a phase transformable material
Journal of The Mechanics and Physics of Solids, 2013Co-Authors: Qianhua Kan, Guozheng Kang, Wenyi Yan, Qingping SunAbstract:Abstract Instrumented Indentation test has been extensively applied to study the mechanical properties such as elastic modulus of different materials. The Oliver–Pharr Method to measure the elastic modulus from an Indentation test was originally developed for single phase materials. During a spherical Indentation test on shape memory alloys (SMAs), both austenite and martensite phases exist and evolve in the specimen due to stress-induced phase transformation. The question, “What is the measured Indentation modulus by using the Oliver–Pharr Method from a spherical Indentation test on SMAs?” is answered in this paper. The finite element Method, combined with dimensional analysis, was applied to simulate a series of spherical Indentation tests on SMAs. Our numerical results indicate that the measured Indentation modulus strongly depends on the elastic moduli of the two phases, the Indentation depth, the forward transformation stress, the transformation hardening coefficient and the maximum transformation strain. Furthermore, a Method based on theoretical analysis and numerical simulation was established to determine the elastic moduli of austenite and martensite by using the spherical Indentation test and the Oliver–Pharr Method. Our numerical experiments confirmed that the proposed Method can be applied in practice with satisfactory accuracy. The research approach and findings can also be applied to the Indentation of other types of phase transformable materials.
Qingping Sun - One of the best experts on this subject based on the ideXlab platform.
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oliver pharr Indentation Method in determining elastic moduli of shape memory alloys a phase transformable material
Journal of The Mechanics and Physics of Solids, 2013Co-Authors: Qianhua Kan, Guozheng Kang, Wenyi Yan, Qingping SunAbstract:Abstract Instrumented Indentation test has been extensively applied to study the mechanical properties such as elastic modulus of different materials. The Oliver–Pharr Method to measure the elastic modulus from an Indentation test was originally developed for single phase materials. During a spherical Indentation test on shape memory alloys (SMAs), both austenite and martensite phases exist and evolve in the specimen due to stress-induced phase transformation. The question, “What is the measured Indentation modulus by using the Oliver–Pharr Method from a spherical Indentation test on SMAs?” is answered in this paper. The finite element Method, combined with dimensional analysis, was applied to simulate a series of spherical Indentation tests on SMAs. Our numerical results indicate that the measured Indentation modulus strongly depends on the elastic moduli of the two phases, the Indentation depth, the forward transformation stress, the transformation hardening coefficient and the maximum transformation strain. Furthermore, a Method based on theoretical analysis and numerical simulation was established to determine the elastic moduli of austenite and martensite by using the spherical Indentation test and the Oliver–Pharr Method. Our numerical experiments confirmed that the proposed Method can be applied in practice with satisfactory accuracy. The research approach and findings can also be applied to the Indentation of other types of phase transformable materials.
Pavol Sajgalik - One of the best experts on this subject based on the ideXlab platform.
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thermal shock resistance and fracture toughness of liquid phase sintered sic based ceramics
Journal of The European Ceramic Society, 2009Co-Authors: Alexandra Kovalcikova, Jan Dusza, Pavol SajgalikAbstract:Abstract The effect of the heat treatment on the toughness and thermal shock resistance of the silicon carbide–silicon nitride composites prepared by liquid-phase-sintering was investigated. The fracture toughness has been estimated using the Indentation Method and the thermal shock resistance was studied using the Indentation-quench Method. The results were compared to those obtained for a reference silicon carbide material, prepared by the same fabrication route. The Indentation toughness increased from 2.88 to 5.39 MPa m1/2 due to the toughening mechanisms (crack deflection, mechanical interlocking and crack branching) occurring in the heat-treated materials during the crack propagation. Similarly the thermal shock resistance increased after the heat treatment of the experimental materials.
