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MATERIAL FRACTURE TOUGHNESS DETERMINATION FOR POLYETHYLENE PIPE MATERIALS USING SMALL SCALE TEST RESULTS

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Acta Mechanica Sinica 1997年第1期13卷 63-80页

作者：庄茁 Department of Engineering Mechanics Tsinghua UniversityBeijing 100084China

The Small-Scale Steady State (S4) test has been recently developed in order to assess the fracture behaviour of polyethylene (PE) gas distribution pipe material during rapid axial crack propagation. Based on an investigation of the S4 test, a simulation model of S4 test has been developed. This paper describes the use of the results obtained from the S4 test and program modified from PFRAC (Pipeline Fracture Analysis Code) to evaluate the fracture toughness of the material, G(d), which could not be directly obtained from the test, and to predict critical pressure, p(c), for rapid crack propagation (RCP) in a full scale PE pipe. The algorithms for contact conditions are developed to consider the opening pipe wall impact against a series containment rings and the capabilities of PFRAC are also extended. When G(d) is evaluated, investigations are made on the effect of temperature, wall thickness and crack velocity. In addition, procedures to evaluate the critical pressure for the S4 test pipe are also discussed.

关键词： fracture mechanics pipeline experiment finite element simulation fracture toughness critical pressure

Rapidly Estimating Natural Gas Compressibility Factor

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Journal of Natural Gas Chemistry 2007年第4期16卷 349-353页

作者： Alireza Bahadori Saeid Mokhatab Brian F.Towler Department of Chemical Engineering Curtin University of Technology GPO Box 1987PerthWA 6845Australia Process Technology Department Tehran Raymand Consulting Engineers TehranIran Chemical and Petroleum Engineering Department University of Wyoming Laramie.WYUSA

Natural gases containing sour components exhibit different gas compressibility factor （Z） behavior than do sweet gases. Therefore, a new accurate method should be developed to account for these differences. Several methods are available today for calculating the Z-factor from an equation of state. However, these equations are more complex than the foregoing correlations, involving a large number of parameters, which require more complicated and longer computations. The aim of this study is to develop a simplified calculation method for a rapid estimating Z-factor for sour natural gases containing as much as 90% total acid gas. In this article, two new correlations are first presented for calculating the pseudo- critical pressure and temperature of the gas mixture as a function of the gas specific gravity. Then, a simple correlation on the basis of the standard gas compressibility factor chart is introduced for a quick estimation of sweet gases＇ compressibility factor as a function of reduced pressure and temperature. Finally, a new corrective term related to the mole fractions of carbon dioxide and hydrogen sulfide is developed.

关键词： natural gas compressibility factor sour gas critical pressure critical temperature

Modeling of Stress Distribution During Strip Coiling Process

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Journal of Iron and Steel Research International 2012年第8期19卷 6-11页

作者： WANG Yong-qin, LI Li, YAN Xing-chun, LUO Yuan-xin, WU Liang (The State Key Laboratory of Mechanical Transmission, Chongqing University, Chongqing 400030, China) The State Key Laboratory of Mechanical Transmission Chongqing University Chongqing 400030 China

Many strip materials are coiled after rolling process. The stresses are imposed on the material wound on the automatically controlled collapse mandrel under the coiling tension. The coiling process can be described by three typical cases: winding without automatic adjustment, winding with automatic adjustment and after mandrel removal. A new model of equations for predicting the stresses during the strip coiling process is built by consideration of the three cases respectively. By solving the equations of different typical cases, the radial stresses and tangential stress of the layers of coil can be calculated. Also, the coiling parameters, such as strip thickness, coiling tension and necking critical pressure, affecting the coil performance are investigated. It is believed that the present model can be used for design and control of the automatically controlled collapse mandrel.

关键词： automatically controlled collapse mandrel coiling process critical pressure radial stress tangential stress

Elastoplastic Analysis of Circular Tunnel in Saturated Ground Under Different Load Conditions

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Computers, Materials & Continua 2020年第1期62卷 179-197页

作者： Panpan Zhai Ping Xu College of Water Conservancy&Environmental Engineering Zhengzhou UniversityZhengzhou450001China National Local Joint Engineering Laboratory of Major Infrastructure Testing and Rehabilitation Technology Zhengzhou450001China

When a tunnel is excavated below the groundwater table,groundwater flows in through the excavated wall of the tunnel and seepage forces act on *** forces significantly affect the ground reaction curve,which is defined as the relationship between the internal pressure and radial displacement of the tunnel *** study investigates analytical solutions for seepage forces acting on the lining of a circular tunnel under steady-state groundwater *** the tunnel’s construction or service period and boundary conditions,the direction of maximum principal stress changes,and the input stress of the Mohr-Coulomb criterion *** stress distribution and yield range of the surrounding soils and linings are *** first,second,and third critical inner pressures are defined and *** influence of the seepage field on the plastic radius,first critical pressure,and stress distribution of the tunnel is *** is shown that during the construction period,the seepage force promotes the expansion of the yield area,whereas during the service period,the opposite is the *** first critical pressure increases nearly linearly with the distant water *** radial stress distribution decreases clearly in comparison with that when the seepage force is not considered,and the reduction is more prominent when internal pressure *** tangential stress distribution increases clearly compared with that when the seepage force is not considered.

关键词： Tunnel lining surrounding soils elastoplastic analysis critical pressure plastic radius seepage force

critical and Impeding pressures of Al Evaporation during ISM Processing of NiAl

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Journal of Materials Science & Technology 2003年第6期19卷 571-575页

作者： Guizhong LIU, Jingjie GUO, Yanqing SU, Jingzhe GUO, Jun JIA and Hengzhi FUSchool of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, China Sch. of Mat. Sci. and Eng. Harbin Inst. of Technol. Harbin 150001 China

In this paper, the critical pressure pcrit and impeding pressure pimpe of the elemental evaporation were defined and studied based on the calculation of the relationship between the evaporation loss rate Nm and the chamber pressure p during melting of NiAl alloys. When the chamber pressure is lower than pcrit or higher than Pimpe Nm tends to be the maximum or minimum value and remains almost unchanged. However, declines sharply with the increase of the chamber pressure when pcrit

关键词： ISM process Al evaporation critical pressure Impeding pressure

Determination of critical Parameters of Carbon Dioxide+Butyraldehyde System with Different Compositions

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Chemical Research in Chinese Universities 2005年第6期21卷 687-691页

作者： ZHANG Jing-chang GAO Xi-xin CAO Wei-liang Key Laboratory of Science and Technology of Controllable Chemical Reactions of Ministry of Education Institute of Modern Catalysis Beijing University of Chemical Technology Beijing 100029 P. R. China

Supercritical carbon dioxide（SC-CO2 ） is considered in green chemistry as a substitute for conventional solvents in chemical reactions due to its environmentally benign character. Recently we have reported the homogeneous hydroformylation of propylene in supercritical carbon dioxide（ SC-CO2 ） , which is an example of this kind of application of carbon dioxide. The determination for the critical parameters of carbon dioxide ＋ butyraldehyde mixtures is necessary for this reaction design which is the focus of the present paper. The critical parameters of the binary systems were determined via the static visual method at a constant volume with the molar fraction of butyraldehyde ranging from 1.0% to 2. 2% and the pressure ranging from 5 to 10 MPa. The experimental results show that the critical pressure and temperature increased with increasing the molar fraction of butyraldehyde. The bubble（dew） temperatures and the bubble （dew） pressures for the binary systems were also determined experimentally. The p-T Figures at different compositions of the binary systems were described. In addition, the critical compressibility factors Zc of the binary systems at different concentrations of n-butyraldehyde were calculated. It was found that the critical compressibility factor values of the binary systems decreased with increasing the molar fraction of n-butyraldehyde in the experimental range.

关键词： Carbon dioxide + butyraldehyde binary system critical temperature critical pressure p-T Figure critical compressibility factor

Orifice plate cavitation mechanism and its influencing factors

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Water Science and Engineering 2010年第3期3卷 321-330页

作者： Wan-zheng AI Tian-ming DING Marine College of Zhejiang Ocean University Zhoushan 316000 P. R. China

The orifice plate energy dissipater is an economic and highly efficient dissipater. However, there is a risk of cavitaion around the orifice plate flow： In order to provide references for engineering practice, we examined the cavitation mechanism around the orifice plate and its influencing factors by utilizing mathematical analysis methods to analyze the flow conditions around the orifice plate in view of gas bubble dynamics. Through the research presented in this paper, the following can be observed： The critical radius and the critical pressure of the gas nucleus in orifice plate flow increase with its initial state parameter r0 ; the development speed of bubbles stabilizes at a certain value after experiencing a peak value and a small valley value; and the orifice plate cavitation is closely related to the distribution of the gas nucleus in flow. For computing the orifice plate cavitation number, we ought to take into account the effects of pressure fluctuation. The development time of the gas nucleus from the initial radius to the critical radius is about 107-10-5 s; therefore, the gas nucleus has sufficient time to develop into bubbles in the negative half-cycle of flow fluctuation. The orifice critical cavitation number is closely related to the orifice plate size, and especially closely related with the ratio of the orifice plate radius to the tunnel radius. The approximate formula for the critical cavitation number of the square orifice plate that only considers the main influencing factor was obtained by model experiments.

关键词： orifice plate cavitation gas nucleus critical radius critical pressure pressure fluctuation critical cavitation number

Pressurization, intercalation, doping, and elements: An empirical study of superconductivity near perturbation onsets

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Superconductivity 2024年第2期10卷 29-37页

作者： Shermane M.Benjamin The National High Magnetic Field Laboratory 1800 E.Paul Dirac DriveTallahasseeFL 32310USA

Superconductivity is a phenomenon arising from cooperative electron ***,correlations among(1)the minimum tuning parameter required for emergence,(2)the superconducting transition temperature resulting from minimal tuning,and(3)the host’s physical/chemical properties still elude the scientific *** empirical investigations,such as those revealing ideal gas-like correlations at the onset of superconductivity in intercalated superconductors,motivate this *** investigation reports similar findings in systems(>170 compounds)exhibiting superconductivity through other perturbative means,such as single-element *** general,statistical measures,including distance correlation analyses(≠linear regression fit)of thermodynamic variables,indicate the presence of empirical relationships near the superconducting onset of systematically tuned *** relations involve unit cell volume(V),the number of valence electrons(N),and the superconducting transition temperature(T_(c)).Note:The author’s primary aim is not to validate or challenge BCS theory;it is instead to focus on leveraging methodology led by available data to enhance the exploration and development of innovative and cost-effective superconductors.

关键词： Superconductivity Ideal gas law Empirical Doping Intercalation critical pressure Phenomenological theory Predicting T_(c)

Hydrodynamic deep drawing of double layered conical cups

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Transactions of Nonferrous Metals Society of China 2016年第1期26卷 237-247页

作者： Alireza JALIL Mohammad HOSEINPOUR GOLLO M.Morad SHEIKHI S.M.Hossein SEYEDKASHI Faculty of Mechanical Engineering Shahid Rajaee Teacher Training University School of Mechanical Engineering University of Birjand

Hydrodynamic deep drawing assisted by radial pressure is an advanced sheet forming technology with great advantages such as higher drawing ratio, good surface quality and higher dimensional accuracy. In this process, both the bottom surface and the peripheral edge of sheets are under hydrodynamic pressure, so that the forming procedure is more uniform with low failure probability. Multi-layered sheets with complex geometries could be formed more easily with this technique compared with other traditional methods. Rupture is the main irrecoverable failure form in sheet forming processes. Prediction of rupture occurrence is of great importance for determining and optimizing the proper process parameters. In this research, a theoretical model was proposed to calculate the critical rupture pressure in production of double layered conical parts with hydrodynamic deep drawing process assisted by radial pressure. The effects of other process parameters on critical rupture pressure, such as punch tip radius, drawing ratio, coefficient of friction, sheet thickness and material properties were also discussed. The proposed model was compared with finite element simulation and validated by experiments on Al1050/St13 double layered sheets, where a good agreement was found with analytical results.

关键词： hydrodynamic deep drawing radial pressure double layered sheet conical cup critical pressure