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Liu C.,Tianjin University | Zhao Q.,Tianjin Special Equipment Inspection Institute | Liu Y.,Tianjin University | Wei C.,Tianjin Special Equipment Inspection Institute | Li H.,Tianjin University
Fusion Engineering and Design | Year: 2017

In this paper, the influence of compressive deformation in metastable austenite zone (at 700, 600 and 500. °C, respectively) on microstructural characteristics and martensitic transformation behavior for the high Cr ferrite/martensite steel is investigated by using high-resolution dilatometry and transmission electron microscopy (TEM) observation. The results show that compressive deformation in metastable austenite zone results in decrease of martensite lath width and increase of martensite starting temperature (Ms ) due to increase of defection density for martensitic nucleation. The martensitic transformation time is extended by the pre-stress loading above Ms , which is ascribed to decrease of interfacial migration rate during martensitic transformation by means of strain hardening. The results of tempering experiments indicate that decrease of deformation temperature leads to increase of recovery fraction. This is ascribed to that decrease of deformation temperature raises the residual strain energy and thus lowers the apparent activation energy for recovery. Hence, phenomenon of recovery occurs prematurely in the tempering specimen with the low deformation temperature. © 2017 Elsevier B.V.

Wei C.,Tianjin University of Technology | Wei C.,Tianjin Special Equipment Inspection Institute | Liu Y.C.,Tianjin University of Technology | Yu L.M.,Tianjin University of Technology | And 2 more authors.
Microelectronics Reliability | Year: 2010

Tensile testing of Sn-3.7Ag-0.9Zn-xAl (x = 0, 0.5 and 1.0 wt.%) solders have been performed and the failure mechanism was investigated. The results suggest that the addition of Al in the Sn-3.7Ag-0.9Zn solder decreases both the tensile strength and ductility. Moreover, a brittle fracture occurs instead of a ductile fracture with increasing Al content. The fractographs suggest that the fracture mechanism of Sn-Ag-Zn eutectic solder is microvoid coalescence fracture, and the Sn-3.7Ag-0.9Zn-xAl (x = 0.5 and 1.0) solder corresponds to quasi-cleavage crack and cleavage fracture respectively. © 2010 Elsevier Ltd. All rights reserved.

Qi Z.,Tianjin University of Technology | Lin B.,Tianjin University of Technology | Zhang Y.,Tianjin University of Technology | Liang X.,Tianjin special equipment inspection institute | Li X.,Tianjin University of Technology
Key Engineering Materials | Year: 2015

Traditional methods of roughness characterization cannot properly reflect the characteristics of engineering ceramics surface topography. Therefore, the composite characterization using combined fractal method and wavelet method is introduced in this paper. And they are used to describe the global and local characteristics of engineering ceramics ground surface, respectively. Furthermore, a concept called topography damage ratio is proposed to describe characteristic of the deep wave trough. Finally, 3-D measurement is used to verify this method. © (2015) Trans Tech Publications.

Gao L.-L.,Tianjin University of Technology | Zhang C.-Q.,Tianjin University of Technology | Yang Y.-B.,Tianjin Special Equipment Inspection Institute | Shi J.-P.,Tianjin University of Technology | Jia Y.-W.,Tianjin University of Technology
Materials Science and Engineering C | Year: 2013

It is significant to investigate the depth-dependent mechanical behaviors of articular cartilage under rolling load since considerable rolling occurs for cartilage joint in activities of daily living. In this study, the rolling experiments of articular cartilage were conducted by applying an optimized digital image correlation (DIC) technique for the first time and the depth-dependent normal strain and shear strain of cartilage were analyzed. It is found that the normal strain and shear strain values of different layers increase firstly and then decrease with rolling time, and they increase with increasing compressive strains. The normal strain and shear strain values decrease along cartilage depth with constant compressive strain. The normal strain values of different normalized depth decrease with increasing rolling rates. The shear strain values of superficial layer and middle layer decrease; however there are no major changes for the shear strain values of deep layer with increasing rolling rates. The normal strain values with different rolling time increase with increasing rolling numbers and the 30.6% increase in initial normal strain is observed from 1st to 99th cycle. The fitting relationship of the normal strain and normalized depth was obtained considering the effects of compressive strain and rolling rate and the fitting curves agree with the experimental results for cartilage very well. © 2013 Elsevier B.V.

Jiang B.,Tianjin University | Jiang B.,Tianjin Special Equipment Inspection Institute | Yang X.,Civil Aviation University of China | Niu W.,Tianjin Special Equipment Inspection Institute | And 3 more authors.
Scripta Materialia | Year: 2016

Ultralight monolithic Co/Ag composite foams were synthesized by a novel and facile method based on the traditional electroless plating. The resultant foams had remarkably low densities down to 12.7 mg/cm3 or 99.9% porosity. Morphology of the Co/Ag composite foams was studied and compressive properties of the foam were investigated in light of its relative density. The densification strain of the foam can reach 87% because of the ultralow density. The compressive yield strength was measured and found to be in agreement with the value predicted by the cellular solids theory. © 2016 Elsevier Ltd. All rights reserved.

Zhao Q.,Tianjin Special Equipment Inspection Institute | Jiang B.,Tianjin Special Equipment Inspection Institute | Wang J.,Tianjin University
Jinshu Rechuli/Heat Treatment of Metals | Year: 2016

High temperature aging method was used to accelarate the aging process of 20G steel which is mainly used for pressure vessel, steam pipes and so on. The evolution of the microstructure and mechanical properties (hardness) was systematically investigated under the acceleration of the aging process. The results show that during the aging process, pearlite is spheroidized gradually and carbide is gathered in the grain boundary. The rate of pearlite spheroidization gradually is reduced with the high temperature aging time increasing. The formula of the grain size changing with the aging time is established. Based on the hardness measurement and the analysis of the microstruture, the service life of the material is predicted through the combination of the hardness value and the Larson-Miller parameters. © 2016, Editorial Office of "Jinshu Rechuli". All right reserved.

Tan W.,Tianjin University | Liu X.,Tianjin University | Liu Y.,Tianjin University | Bu Y.,Tianjin University | Wang Z.,Tianjin Special Equipment Inspection Institute
Journal of Loss Prevention in the Process Industries | Year: 2011

Computational Fluid Dynamics (CFD) approach has been successfully applied to simulate the small-scale instantaneous flashing release experiment by Pettitt. A model for dispersion of the release event is provided based on relevant theories and existing experimental data. An application of the CFD method to the dispersion simulation is illustrated. Furthermore, a new methodology based on discrete phase model for setting computational initial conditions is provided. An initial expansion and subsequent turbulence dispersion can be characteristically identified from both volume and temperature variation of the cloud obtained by the simulation. The possible mechanism for these phenomena has also been discussed and analyzed. The study deepens the understanding of the physical process of this event and provides one more reliable tool for relevant safety systems. © 2011 Elsevier Ltd.

Liu X.,Tianjin University | Tan W.,Tianjin University | Bu Y.,Tianjin University | Liu Y.J.,Tianjin University | Wang Z.J.,Tianjin Special Equipment Inspection Institute
Advanced Materials Research | Year: 2011

An accident instantaneous release of LPG can results in a rapidly expanding two-phase flammable cloud, which is the medium of potentially disastrous consequences. In this paper, CFD (Computational Fluid Dynamics) method was applied for instantaneous LPG release in an open environment in order to analysis the expansion process of two-phase cloud. The results from simulation are compared with the published experimental data to validate the model. Statistical analysis of experimental data is used to set the initial conditions and computational inlet in the model. The mass and heat transfer is calculated in eulerian-lagrangian method. The features in expansion process are studied by the analyses of the variation of size, temperature, volume averaged rate of evaporation of the cloud and entropy of the whole flow field. © (2011) Trans Tech Publications.

PubMed | Illinois Institute of Technology, Tianjin University and Tianjin Special Equipment Inspection Institute
Type: | Journal: Scientific reports | Year: 2015

Ultralight (<10mg/cm3) cellular materials are desirable for thermal insulation; battery electrodes; catalyst supports; and acoustic, vibration, or shock energy damping. However, most of these ultralight materials, especially ultralight metal foams, are fabricated using either expensive materials or complicated procedures, which greatly limit their large-scale production and practical applications. Here we report a simple and versatile method to obtain ultralight monolithic metal foams. These materials are fabricated with a low-cost polymeric template and the method is based on the traditional silver mirror reaction and electroless plating. We have produced ultralight monolithic metal foams, such as silver, nickel, cobalt, and copper via this method. The resultant ultralight monolithic metal foams have remarkably low densities down to 7.4mg/cm3 or 99.9% porosity. The metal foams have a long flat stress-train curve in compression tests and the densification strain D of the Ni/Ag foam with a porosity of 99.8% can reach 82%. The plateau stress pl was measured and found to be in agreement with the value predicted by the cellular solids theory.

Dai G.-Y.,Tianjin Special Equipment Inspection Institute | Sun L.-X.,Tianjin Special Equipment Inspection Institute
Proceedings - 2015 Chinese Automation Congress, CAC 2015 | Year: 2015

Based on the energy conservation related to elevator's load, motor power, elevator's velocity and machinery efficiency, a mathematical model for solving the elevator equilibrium coefficient was proposed in detail. In order to realize the proposed method, through real-Time sampled data including the operating power in no-load mode and speed of the elevator, test results of the equilibrium coefficient were collected and calculated automatically by central processing device to avoid being complex loaded operation. Besides, it would take just ten minutes or less to complete the whole operation due to convenient installation. © 2015 IEEE.

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