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Chinese Journal of Aeronautics 2018年第6期31卷 1273-1286页

作者： Lulu LIU Zhenhua ZHAO Wei CHEN Gang LUO Jiangsu Province Key Laboratory of Aerospace Power System College of Energy and Power Engineering Nanjing University of Aeronautics and Astronautics

In this paper, ballistic impact tests on wrapped multi-layer Kevlar 49 woven fabric systems were carried out with a flat blade projectile to investigate the impact response during a fan blade out event. The influences of the number of Kevlar layers and pre-tension were discussed particularly. Test results were used to analyze failure modes and energy absorption characteristics of multi-ply Kevlar fabrics. Results show that there are two kinds of impact damage for fabrics： global deformation mainly involving stretching of yarns in the impact region and fabric wrinkle from both sides to the impact zone, and local damage characterized by yarn fracture, yarn pull-out, and yarn unraveling. The energy absorption capability of Kevlar 49 woven fabrics improves with the number of fabric layers. The energy absorbed by multi-layer fabrics increases slightly at the beginning and then decreases substantially with pre-tension. The work in this paper can provide guidance for designing light-weight multi-layer fabrics containment systems.

关键词： Energy absorption Fabrics Gas turbines Impact resistance Multi-layers pre-tension

Suppressing abnormal grain growth and switching precipitation behaviors in ZK60 Mg profile by inducing pre-tension

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Journal of Materials Science & Technology 2023年第24期155卷 89-101页

作者： Jianwei Tang Liang Chen Zhigang Li Biaohua Que Guoqun Zhao Cunsheng Zhang Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials(Ministry of Education) Shandong UniversityJinan 250061China

The pre-tension was induced to suppress the abnormal grain growth(AGG)of ZK60 Mg profile during solution *** effects of pre-tension on the microstructure evolution and mechanical properties were studied,and the suppressing mechanism was *** the pre-tension strain was larger than 10%,AGG during solution could be effectively inhibited,resulting in a sharp decrease in the grain *** suppression effects were realized by restricting the orientation dependent of AGG and promoting static *** pre-tension reset the distributions of stored energy and sizes of the grains with〈11–20〉and〈10–10〉orientations,and thus retarded the orientation dependent of ***,the pre-tension introduced a mass of dislocations,twins,and stacking faults,all of which promoted the occurrence of static recrystallization,and the grain structure was further *** pre-tension accelerated the precipitation kinetics during aging,resulting in fine and dense *** the increase of pre-tension strain,the strength of ZK60 Mg profile monotonically increased.

关键词： Mg alloy Abnormal grain growth pre-tension Microstructure Mechanical properties

Tailoring Texture to Highly Strengthen AZ31 Alloy Plate in the Thickness Direction via pre-tension and Rolling-Annealing

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Acta Metallurgica Sinica(English Letters) 2023年第2期36卷 266-280页

作者： Tianjiao Li Jiang Zheng Lihong Xia Haoge Shou Yongfa Zhang Rong Shi Liuyong He Wenkai Li International Joint Laboratory for Light Alloys(Ministry of Education) College of Materials Science and EngineeringChongqing UniversityChongqing400044China Shenyang National Laboratory for Materials Science Chongqing UniversityChongqing400044China College of Mechanical Engineering Chongqing Technology and Business UniversityChongqing400067China Zhejiang Provincial Engineering Center of Integrated Manufacturing Technology and Intelligent Equipment Zhejiang University City CollegeHangzhou310015China

Conventional wrought Mg alloys,such as AZ31 and ZK60 rolled plates,usually exhibit significantly low tensile yield strength in the thickness *** can be attributed to the high activity of{10-12}tension twinning due to the strong basal texture(//ND,normal direction).In this work,the tensile yield strength in the ND of the as-rolled(AR)AZ31 plate increased from 50 to 150 MPa(increased by 200%)via simple processing,i.e.,pre-tension and rolling-annealing(PTRA)*** strong basal texture(//ND)of the AR plate was changed into a weakened fiber texture(⊥ND).The evolution of microstructures during PTRA treatment and the activated deformation modes during uniaxial tension were studied quantitatively and statistically by the means of intergranular misorientation(IM)and in-grain misorientation axes(IGMA)*** results indicate that various twin variants,as well as{10-12}-{10-12}secondary twins,were activated during pre-tension and rolling,and most residual matrix was consumed by twins after *** dominated deformation modes in tension changed from{10-12}tension twinning(the AR sample)to prismatic slip(the PTRA sample)in the early tensile *** underlying formation mechanism of the fiber texture and corresponding strengthening mechanism were discussed.

关键词： pre-tension Annealing Tailoring texture Texture strengthening Deformation modes

Safety Limits for pre-tension of Membrane Roofs on Closed Structure in Air Flow

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Applied Mathematics 2024年第11期15卷 818-827页

作者： Weiju Song Heyuan Yang Heding Yu School of Civil Engineering Tianjin University Tianjin China Huaheng Construction Group Ningbo China School of Civil Engineering Hebei University of Engineering Handan China

The stiffness required for the normal operation of membrane roof comes from the application of pre-tension. When the pre-tension is too small, it is easy to cause instability under the action of wind load, which leads to excessive deformation of the roof and local or overall damage. In order to ensure that the membrane roof is always in normal use state in the airflow field, this paper takes the membrane pretension as the control parameter to study the value of safety pretension of closed membrane roof. According to the theory of large deflection of membrane and Galerkin method, the nonlinear vibration differential equation of membrane roof under static wind is established, and the critical state of safe working of membrane roof is determined by judging the stability of the solution of the equation, and the expression of critical wind speed is obtained. By establishing the inequality relationship between local design wind speed and critical wind speed, the safety pretension limit of membrane roof under specific site can be obtained. The research shows that the safety pretension limits of closed membrane roofs are different in different areas under different design return periods. In addition, the value of safety pretension is related to the film geometry.

关键词： Membrane Roof pre-tension Aerodynamic Stability Critical Wind Speed

Fundamental principles of an effective reinforcing roof bolting strategy in horizontally layered roof strata and areas of potential improvement

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International Journal of Mining Science and Technology 2018年第1期28卷 67-77页

作者： Russell Frith Guy Reed Martin McKinnon Mine Advice Pty Ltd New South Wales 2282Australia

It is arguable that the development of reinforcing roof bolting systems has largely stagnated in recent times, primarily due to the prevailing industry view that few, if any, further improvements can be made to what currently ***, this paper contends that reinforcing roof bolting systems can be further refined by considering both the specific manner by which horizontally bedded roof strata loses its natural self-supporting ability and the specific means by which reinforcing roof bolts act to promote or retain this natural self-supporting *** Australian coal industry has insisted on minimising bolt-hole diameter to maximise load transfer and on targeting full-encapsulation by any means necessary for many *** has led to a significant, albeit unintended, consequence in terms of overall roof bolting effectiveness, namely increased resin pressures during bolt installation and the associated potential for opening bedding planes that may have, otherwise, remained closed during the bolt installation *** that the natural self-supporting ability of roof strata is strongly linked to whether bedding planes are open or closed, logically, minimising resin pressures should be a significant *** paper focuses primarily on three key issues that relate directly to the function of the roof bolting system itself:(1) the importance of proper resin mixing in the context of maximising load transfer strength and stiffness,(2) the importance of minimising resin pressures developed during bolt installation, and(3) the importance of maximising the effectiveness of the available bolt *** mine operators should be invested in improving the individual effectiveness of each installed roof bolt, even by relatively small incremental amounts, so this is an important topic for discussion within the mining community.

关键词： Roof bolts Strata reinforcement Partial-encapsulation pre-tension Resin mixing Improved bolt effectiveness

An alternative method to reduce process-induced deformation of CFRP by introducing prestresses

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Chinese Journal of Aeronautics 2022年第8期35卷 314-323页

作者： Zhendong LIU Xitao ZHENG Wenjing FAN Fei WANG Sohail AHMED Leilei YAN School of Aeronautics Northwestern Polytechnical UniversityXi’an 710072China Unmanned System Research Institute Northwestern Polytechnical UniversityXi’an 710072China

Process-induced deformation is an important limiting factor to the application of high performance composite *** alternative method to reduce process-induced deformation is proposed by introducing prestress to a single layer or part of the layers instead of all the applicable *** this method,the necessary prestress level that applied to the single layer was in the reasonable *** kinds of unsymmetric laminates are manufactured at varying prestress *** experimental results described that the curing deformation is changed rapidly with the growing prestress level and flipped after a certain prestress ***,there is a good linear relationship between prestress level and final curing deformation,which gives a convenient way to calculate the prestress level that can fully counteract the curing *** numerical model to predict the curing deformation was built.A good agreement between the numerical and the experimental results shows the effectiveness of the numerical *** predict the prestress level that can fully counteract the curing deformation,an analytical model is also ***,the prestress method can fully counteract the curing deformation of the specimens,while the experimental results show that the prestressing layer reduces more than 80%of the curing deformation.

关键词： Curing deformation prestressing pre-tension Process-induced deforamtion Residual stress

Fatigue Analysis of the Taut-Wire Mooring System Applied for Deep Waters

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China Ocean Engineering 2011年第3期25卷 413-426页

作者：黄维刘海笑单桂敏胡存 School of Civil Engineering Tianjin University

precisely predicting the fatigue life of taut-wire mooring systems has become an interesting and important problem for scientists and engineers since there are still difficulties in the inspection and maintenance of mooring lines in a rough sea environment especially in deep waters. In this paper, a comprehensive fatigue analysis is performed for a polyester taut-wire mooring system of an FPSO based on the time domain dynamic theory, rainflow cycle counting method and linear damage accumulation rule of Palmgren-Miner. Three influential factors in the fatigue analysis including the pre-tension, dynamic stiffness and T-N curve are investigated in detail. Two polyester T-N curves, one is from the DNV- 0S-E301 and the other is from the API-RP-2SM, are adopted in the calculation. The fatigue analysis of the mooting system after one-line failure is also carried out. The calculation results indicate that the fatigue life is significantly affected by the T-N curve. The fatigue life decreases with increasing pre-tension, and is largely reduced if taking into account the dynamic stiffness caused by cyclic loading. The analysis also proves that one-line failure has remarkable effects on the fatigue lives of other mooting lines. The present parametric and comparative study is believed to be meaningful to further understanding of the taut-wire mooting system for deepwater applications.

关键词： taut-wire mooring system fatigue analysis T-N curve dynamic stiffness pre-tension one-line failure