The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Jürgen Rödel - One of the best experts on this subject based on the ideXlab platform.
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Temperature dependent Fracture toughness of KNN-based lead-free piezoelectric ceramics
Acta Materialia, 2019Co-Authors: Yi-xuan Liu, Paul-erich Öchsner, Daniel Isaia, Yichi Zhang, Ke Wang, Kyle G. Webber, Jürgen RödelAbstract:Abstract The Fracture toughness of unpoled and electrically poled lead-free KNN-based piezoelectric ceramics with the composition of 0.92KNN-0.02Bi0.5Li0.5TiO3-0.06BaZrO3 was investigated. Results reveal that at room temperature, the intrinsic Fracture toughness (KI0) of the unpoled samples, evaluated by the near-tip Crack opening displacement (COD) technique, is the lowest with a value of 0.70 MPa ⋅ m0.5; the long (through-thickness) Crack Fracture toughness (KIvnb), obtained by the single edge V-notch beam (SEVNB) technique, is the highest, with a value of 0.95 MPa ⋅ m0.5; intermediate short surface Crack Fracture toughness (KIsc) of 0.86 MPa ⋅ m0.5 was determined by the surface Crack in flexure (SCF) technique. These results were rationalized by the toughening behavior of the material combined with the Crack geometry-dependent stress intensity evolution during Crack propagation. With increasing temperature, KIvnb and KIsc decrease, and become nearly identical at 350 °C, suggesting an absence of toughening. For electrically poled samples, their room temperature Fracture toughness was characterized by both SCF and SEVNB techniques, with values of 0.88 MPa ⋅ m0.5 and 0.99 MPa ⋅ m0.5, respectively, slightly larger than the values measured for unpoled samples. Nonlinear electric field-strain and stress-strain analysis of the material was also employed during electric field loading, mechanical compression and four-point bending in order to quantify Crack tip shielding by domain switching and the actual stress at the point of instable Crack propagation.
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short Crack Fracture toughness in 1 x na1 2bi1 2 tio3 xbatio3 relaxor ferroelectrics
Journal of the American Ceramic Society, 2017Co-Authors: Sarah Marie Denkhaus, Malte Vogler, Nikola Novak, Jürgen RödelAbstract:The Fracture toughness in the lead-free relaxor ferroelectric (1-x)(Na1/2Bi1/2)TiO3-xBaTiO3 was investigated utilizing the surface Crack in flexure method. To allow a comprehensive assessment, unpoled and poled samples from the rhombohedral, the tetragonal, and the morphotropic phase regime were considered. It was found that the Fracture toughness is up to 23% higher for the poled state. In order to cover the transition from ferroelectric to relaxor phase, the temperature dependence of 0.97(Na1/2Bi1/2)TiO3-0.03BaTiO3 was studied as well. Fracture toughness values of up to 2 MPam1/2 were determined, which are considerably above data for lead zirconate titanate materials. The results are rationalized using a simple transformation toughening-type model in conjunction with investigations into the ferroelastic behavior. The presented model can be applied without fitting parameters but utilizes measurements of the coercive stress and remanent strain as well as the elastic modulus. This article is protected by copyright. All rights reserved.
Hongyang Jing - One of the best experts on this subject based on the ideXlab platform.
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Surface Crack Fracture toughness and HRR fields of ultra-high strength steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Jiquan Zou, Hongyang JingAbstract:Abstract In present, due to continuous increasing of the Fracture toughness and continuous reduction of steel plate thickness for ultra-high strength steel used in the aerospace solid rocket motor, it is difficult to measure its Fracture toughness of surface Crack using the linear elastic Fracture mechanics method. In this paper, the tensile test was used to achieve the conditional load when the surface Crack initiation occurred. Then, the finite element method (FEM) was conducted to calculate the ductile Fracture toughness J IC under the conditional load. Lastly, the surface Crack Fracture toughness, K Ie , can be computed from J IC based on the Fracture mechanics method. In addition, the analysis on validity of J -integral showed that K Ie converted from J IC was able to evaluate the Fracture toughness of ultra-high strength steel. These are important technical parameters for design of aerospace solid rocket motor.
Dinesh K. Shetty - One of the best experts on this subject based on the ideXlab platform.
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Short‐Crack Fracture Toughness of Silicon Carbide
Journal of the American Ceramic Society, 2009Co-Authors: Sarbjit Kaur, Raymond A. Cutler, Dinesh K. ShettyAbstract:The Fracture toughness of four different silicon carbides was measured using single-edge preCracked beam (SEPB) and indentation/strength techniques. Two were development grades with similar microstructures and chemistries, and yet exhibited different Fracture modes. The grade that exhibited a predominantly intergranular Fracture had an SEPB Fracture toughness (6.4 MPaOm) 88% higher than the one that showed primarily a transgranular Fracture (3.4 MPaOm). The higher Fracture toughness was associated with a modest increase in average strength (25%), although there was a significant increase in the Weibull modulus (11–32). Fracture toughness at short Crack lengths was assessed by an indentation method that used Fracture strengths, Crack lengths at Fracture, and a new method of estimating the constant d that characterizes the residual driving force of the plastic zones based on the stable growth of the indentation Cracks from the initial (c0) to the instability (c ) lengths. The results showed a rising Crack-growth-resistance behavior for the grade exhibiting intergranular Fracture, while the grade showing transgranular Fracture had a flat Crackgrowth resistance. Tests on two commercial grades of silicon carbide showed similar behaviors associated with the respective Fracture modes.
Jiquan Zou - One of the best experts on this subject based on the ideXlab platform.
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Surface Crack Fracture toughness and HRR fields of ultra-high strength steel
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2006Co-Authors: Jiquan Zou, Hongyang JingAbstract:Abstract In present, due to continuous increasing of the Fracture toughness and continuous reduction of steel plate thickness for ultra-high strength steel used in the aerospace solid rocket motor, it is difficult to measure its Fracture toughness of surface Crack using the linear elastic Fracture mechanics method. In this paper, the tensile test was used to achieve the conditional load when the surface Crack initiation occurred. Then, the finite element method (FEM) was conducted to calculate the ductile Fracture toughness J IC under the conditional load. Lastly, the surface Crack Fracture toughness, K Ie , can be computed from J IC based on the Fracture mechanics method. In addition, the analysis on validity of J -integral showed that K Ie converted from J IC was able to evaluate the Fracture toughness of ultra-high strength steel. These are important technical parameters for design of aerospace solid rocket motor.
Sarbjit Kaur - One of the best experts on this subject based on the ideXlab platform.
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Short‐Crack Fracture Toughness of Silicon Carbide
Journal of the American Ceramic Society, 2009Co-Authors: Sarbjit Kaur, Raymond A. Cutler, Dinesh K. ShettyAbstract:The Fracture toughness of four different silicon carbides was measured using single-edge preCracked beam (SEPB) and indentation/strength techniques. Two were development grades with similar microstructures and chemistries, and yet exhibited different Fracture modes. The grade that exhibited a predominantly intergranular Fracture had an SEPB Fracture toughness (6.4 MPaOm) 88% higher than the one that showed primarily a transgranular Fracture (3.4 MPaOm). The higher Fracture toughness was associated with a modest increase in average strength (25%), although there was a significant increase in the Weibull modulus (11–32). Fracture toughness at short Crack lengths was assessed by an indentation method that used Fracture strengths, Crack lengths at Fracture, and a new method of estimating the constant d that characterizes the residual driving force of the plastic zones based on the stable growth of the indentation Cracks from the initial (c0) to the instability (c ) lengths. The results showed a rising Crack-growth-resistance behavior for the grade exhibiting intergranular Fracture, while the grade showing transgranular Fracture had a flat Crackgrowth resistance. Tests on two commercial grades of silicon carbide showed similar behaviors associated with the respective Fracture modes.