Shanghai Research Institute of Materials

Shanghai, China

Shanghai Research Institute of Materials

Shanghai, China
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Yu M.,Shanghai JiaoTong University | Zhu P.,Shanghai JiaoTong University | Ma Y.,Shanghai Research Institute of Materials
Composites Science and Technology | Year: 2013

For multi-phase composites, it is increasingly being recognized that the interface region between the filler and the matrix plays a critical role in defining the bulk mechanical properties. However, compared with the constituent components, the interface effect is not easy to measure by experiment, especially for the composites reinforced by spherical fillers. This paper deals with the problem of parameter identification of the interface properties by means of numerical techniques. Hollow spheres filled syntactic foams are taken as research materials. The elastic properties of syntactic foams in terms of Young's modulus and Poisson's ratio were first experimentally investigated by uniaxial tensile test. A microstructure based three-phase FE model with interface simulated by cohesive elements was then developed to predict the elastic mechanical behaviors of syntactic foams. Combining the macroscopic experimental data with the microscopic numerical simulations, an inverse strategy based on Kriging metamodel was proposed to identify the interface elastic properties associated to the studied syntactic foams. Benefiting from the identification procedure, more reliable input parameters can be extracted for the interface modeling, and thus yielding more accurate predictions of the bulk properties of syntactic foams through finite element simulations. © 2012 Elsevier Ltd.


Lai G.-Y.,Shanghai Research Institute of Materials | Zhu L.-K.,Shanghai Research Institute of Materials | Li M.-Y.,Shanghai Research Institute of Materials | Wang J.,Shanghai JiaoTong University
Journal of Prosthetic Dentistry | Year: 2013

Statement of problem Secondary caries is considered to be the most important and common reason for the replacement of all types of restorations. Purpose The purpose of the study was to evaluate in vitro both the anticaries efficacy and marginal integrity of amalgam, glass ionomer cement, and composite resin restorations in a cariogenic condition. Material and methods Class II cavities were prepared on 60 extracted teeth, which were assigned to 3 groups and restored either with amalgam, glass ionomer, or composite resin. After thermal cycling and sterilization, the teeth were set in an artificial carious environment for 10 days. The bacteria from the margin of the restorations were then collected, and microleakage was evaluated by means of dyeing. According to the locations, the demineralization of tooth tissue around the restoration was divided into 3 parts: artificial outer lesion, artificial enamel wall lesion, and artificial dentin wall lesion. The depths of the artificial outer lesion and the areas of the artificial enamel and dentin wall lesions were investigated with a confocal laser scanning microscope after all the specimens had been stained with 0.1 mM Rhodamine B. Statistical analyses consisted of 1-way ANOVA and Kruskal-Wallis tests (α=.05). Results No significant difference was noted in terms of the number of bacteria around the restorations for the 3 materials; the microleakage of amalgam was the least among the 3 types of restorations; the outer enamel lesion depth around the glass ionomer cement was the lowest, and the wall lesion area around the amalgam was the smallest. Conclusions No definite inhibitory effect of fluoride releasing restorative materials (glass ionomer) was apparent on Lactobacillus acidophilus in this study. The amalgam restorations showed the best marginal integrity and the smallest artificial wall lesion among the 3 types of restorations.


Yu M.,Shanghai JiaoTong University | Zhu P.,Shanghai JiaoTong University | Ma Y.,Shanghai Research Institute of Materials
Computational Materials Science | Year: 2012

Tensile properties are critical to the engineering applications of hollow spheres filled syntactic foams. The potential of such composites cannot be fully realized unless their fracture modes and failure mechanisms under tension are fully understood, and appropriate modeling strategies for failure prediction are developed and verified. In this study, both experimental and numerical methods were employed to investigate the tensile behaviors of epoxy-ceramic microspheres syntactic foams with different volume fractions of filler phase. The experimental results indicate that mechanical behaviors of syntactic foams are dominated by brittle fracture mechanism under tensile load. To predict the mechanical properties of syntactic foams in terms of tensile strength and associated failure modes, a three-dimensional microstructure based finite element model was developed by means of a representative volume element (RVE). Cohesive elements were introduced into the finite element model to capture the progressive damage behavior of the microsphere-matrix interface. Complex failure modes of syntactic foams including microspheres fracture, interfacial debonding and the interaction of both features were well characterized according to the simulation results. The proposed model interprets the entire failure process from damage to fracture under tension and provides predictive capabilities for the strength properties of hollow spheres filled syntactic foams. By comparison, the simulation results and the experimental data are found to be in good agreement. © 2012 Elsevier B.V. All rights reserved.


Yu M.,Shanghai JiaoTong University | Zhu P.,Shanghai JiaoTong University | Ma Y.,Shanghai Research Institute of Materials
Computational Materials Science | Year: 2012

An accurate prediction of the bulk properties of syntactic foams, even for the elastic properties, is difficult due to the microstructure being composed of constituents with strong distinctions in mechanical properties. Moreover, it is very costly and time-consuming to characterize the influence of various parameters on the bulk properties of syntactic foams by experiments. In this study, a microstructure-based finite element simulation approach was developed to predict the elastic mechanical behaviors of hollow spheres filled syntactic foams. Three-dimensional cubic unit cell model with interface simulated by cohesive elements was constructed to capture the microstructure and stress/strain fields in mesoscale. The effective elastic properties of syntactic foams in terms of Young's modulus and Poisson's ratio were calculated by means of homogenization method. To get an enhanced understanding of property-structure relations, a global sensitivity analysis was performed based on the high dimensional model representation (HDMR) method. Ten parameters, including geometry and mechanical properties of constituent phases, were selected as input parameters. Independent and cooperative effects of the input parameters on the elastic properties of syntactic foams were investigated by first- and second-order sensitivity indices, respectively. An importance ranking of the input parameters for Young's modulus and Poisson's ratio could then be obtained. The procedure proposed in this work provides a powerful tool for design and optimization of syntactic foams. © 2012 Elsevier B.V. All rights reserved.


Yu M.,Shanghai JiaoTong University | Zhu P.,Shanghai JiaoTong University | Ma Y.,Shanghai Research Institute of Materials
Materials and Design | Year: 2013

Particle clustering originated from manufacturing process is thought to be one of the critical factors to the mechanical performance of hollow spheres filled syntactic foams. Although experimental evidence provides a qualitative understanding of the effects of particle clustering on the mechanical properties of syntactic foams, a quantitative assessment cannot be made in the absence of an appropriate micromechanical modeling strategy. In this study, three-dimensional microstructures of syntactic foams with different degrees of particle clustering were reconstructed based on random sequential adsorption (RSA) method. Three-phase finite element models considering the progressive damage behavior of the microsphere-matrix interface were accordingly developed by means of representative volume element (RVE) to quantitatively investigate the effects of particle clustering on the tensile properties and failure mechanisms of syntactic foams. The simulation results indicate that the elastic behavior of syntactic foams is insensitive to the degree of particle clustering, but the strength properties as well as the failure mechanisms are significantly influenced by the degree of particle clustering. From the micromechanical viewpoint, the clustered regions containing higher concentration of microspheres than the average volume fraction would serve as crack initiation sites due to stress concentration, and consequently lead to a negative effect on tensile strength, fracture strain, and interfacial damage of syntactic foams. © 2012 Elsevier Ltd.


Zhou W.,East China Normal University | Deng H.,Shanghai Research Institute of Materials | Yang P.,East China Normal University | Chu J.,East China Normal University
Applied Physics Letters | Year: 2014

Structural phase transition, narrow band gap (Eg), and room-temperature ferromagnetism (RTFM) have been observed in the [KNbO3]1-x[BaNi1/2Nb1/2O3-δ]x(KBNNO) ceramics. All the samples have single phase perovskite structure, but exhibit a gradual transition behaviour from the orthorhombic to a cubic structure with the increase of x. Raman spectroscopy analysis not only corroborates this doping-induced change in normal structure but also shows the local crystal symmetry for x 0.1 compositions to deviate from the idealized cubic perovskite structure. A possible mechanism for the observed specific changes in lattice structure is discussed. Moreover, it is noted that KBNNO with compositions x = 0.1-0.3 have quite narrow Egof below 1.5 eV, much smaller than the 3.2 eV band gap of parent KNbO3(KNO), which is due to the increasing Ni 3d electronic states within the gap of KNO. Furthermore, the KBNNO materials present RTFM near a tetragonal to cubic phase boundary. With increasing x from 0 to 0.3, the magnetism of the samples develops from diamagnetism to ferromagnetism and paramagnetism, originating from the ferromagnetic-antiferromagnetic competition. These results are helpful in the deeper understanding of phase transitions, band gap tunability, and magnetism variations in perovskite oxides and show the potential role, such materials can play, in perovskite solar cells and multiferroic applications. © 2014 AIP Publishing LLC.


Ding N.,East China Normal University | Deng H.,Shanghai Research Institute of Materials | Yang P.,East China Normal University | Chu J.,East China Normal University
Materials Letters | Year: 2012

Multiferroic BiFe 1 - xZn xO 3 (0 ≤ x ≤ 0.10) thin films were prepared on LaNiO 3 coating Si substrates by pulsed laser deposition. X-ray diffraction data confirmed the substitutions of Zn into the Fe site. The films are the dominant orientation of (101). Three A 1 and five E modes are observed in Raman spectra. With increasing x, the position of the Raman active modes shift to higher wavenumber, and the full width at half maximum becomes smaller. At the photon energy of 2 eV, the refractive index is 2.71, and the extinction coefficient is close to zero. The band gap increases with the Zn amount, which may be caused by Burstein-Moss effect. © 2012 Elsevier B.V. All rights reserved.


Huang D.,East China Normal University | Deng H.,Shanghai Research Institute of Materials | Yang P.,East China Normal University | Chu J.,East China Normal University
Materials Letters | Year: 2010

Single-phase multiferroic BiFeO 3 thin films have been prepared on LaNiO 3/Si(100) and Si(100) wafer via sol-gel technique. The films are polycrystalline with preferring orientation of (101). The film has a conspicuous absorption in the blue and green light region, and band gap of 2.74 eV. The refractive index and the extinction coefficient of the film is about 2.36 and 0.06 at 600 nm, 2.26 and close to zero in the range of 800-1200 nm, respectively. The films also exhibit favorable ferroelectric and dielectric properties. A large photo induced open-circuit voltage was observed, indicating that the film exhibits photovoltaic behaviours. © 2010 Elsevier B.V. All rights reserved.


Ling L.,Shanghai Research Institute of Materials | Rong W.,Shanghai Research Institute of Materials
Engineering Failure Analysis | Year: 2014

The worm gear connecting bolts of refueling machines of a nuclear power plant, with implementing standard of ANSI/ASME B18.3 and ASTM A574-08 and strength grade of 10.9, fractured at the thread neck position after running for about 10 years, and means such as macro examination, chemical compositions analysis, hardness testing, metallographic examination and fracture analysis, were used to analyze the fracture property and reasons of the bolts. The results show that the fracture of the bolts is due to two-way bending fatigue fracture. Surface decarburization of the bolts and stress concentration at the bolt thread neck decreased the fatigue strength of this position and resulted in the initiation of fatigue cracks. By comprehensive analysis and stress estimating, it was concluded that the main reason for fracture of the bolts is that there was a big. gap between the bolts and the bolt holes, which resulted in fatigue fracture of the worm gear connecting bolts. © 2013 Elsevier Ltd.


Background: A connection between a low alloy steel pressure vessel nozzle and a stainless steel main pipe safe-end in a pressurized water reactor (PWR) nuclear power plant is a dissimilar metal weld, which is at key location of pressure boundary and serves in high temperature primary water environments. Since 1990, cracking failure incidents happened on the welds in the primary water coolant of several PWRs in the countries such as USA, Sweden and Japan. Purpose: This paper is to briefly review the typical cases involving this problem in engineering and relevant researches. Methods: Methods such as nondestructive testing, crack and microstructure observation, finite element analysis were used in the failure analysis. Results: The cause of the failure cases was primary water stress corrosion cracking (PWSCC). Conclusions: It is concluded that the welds of 600 Alloy type such as 82/182 are susceptible to PWSCC but those of 690 Alloy Type such as 52/152 have excellent resistance to the cracking, and more researches are necessary.

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