航空材料学报

Characterization of DSC curves of the two-way shape memory effect induced by thermo-mechanical training in TiNiCu alloy

WANG Zhi-guo, ZU Xiao-tao, FENG Xiang-dong, DENG Jiong, DAI Jing-yi, FU Ping

2004, 24(3): 1-4.

[Abstract](1549) [PDF 515KB](303)

Abstract:
Transformation characters of TiNiCu two-way shape memory(TWSM)spring were investigated by differential scanning calorimetry DSC measurement during thermo-mechanical training.The results showed that before training the profile of endothermic peaks were composed of several small peaks.With training the amount of the small peaks decreased.After the stabilized TWSME induced into the TiNiCu alloy,there was only one sharp peak appear.This can attribute to the dislocations structures creates an anisotropic stress field,which guides the orientation of martensite variants very similar.And the dislocations also leads to the decrease of As and Af.Annealing induced the small peaks merge into one peak which resulted from the annihilation of the dislocation introduced by thermo-mechanical training.

Study on overlay coating of Ni₃Al based alloy IC6

SU Xi-kong, LI Shu-suo, HAN Ya-fang, XIAO Cheng-bo, SONG Jin-xia

2004, 24(3): 5-9.

[Abstract](1467) [PDF 255KB](293)

Abstract:
Three kinds of MCrAlX overlay coatings,NiCrAlY,NiCoCrAlY and NiCoCrAlYHf were deposited on alloy IC6 by arc PVD method.The combination between substrate and coating is good.All coatings were comprised of γ,γ prime,β and α-Cr phases.After diffusion treatment,alloying elements diffused into each other between the substrate and coating.All coating can make oxidation resistance and corrosion resistance properties improved obviously,and the effect of NiCoCrAlYHf coating is better than other coatings.NiCoCrAlY and NiCoCrAlYHf.coatings have no big effect in mechanical properties,but NiCrAlY coating made the stress rupture life of alloy IC6 decease at a bigger extent,thus it was not applicable for alloy IC6.

Numerical simulation on the damping characteristic of fiber reinforced composite

ZHANG Shao-hui, CHEN Hua-ling, LIANG Tian-xi

2004, 24(3): 10-14.

[Abstract](1586) [PDF 1066KB](289)

Abstract:
The present investigation is concerned with the utilization of the strain energy based finite element method and the damping properties of the unidirectional lamina for predicting the modal loss factor of fiber reinforced composite structure.The results for the vibration and damping analysis of laminated plates obtained by the present method are compared with the results obtained by other authors to verify the reasonability of the present method.Contributions of 3-D stress components to damping can also be studied by this method.The modal loss factor of an orthogrid-stiffened composite panel is studied using the present method and particular attention is paid to the effect of ribs on damping.

Computation simulation of EM parameters of LDT-epoxy disperse systems

CAO Mao-sheng, GAO Zheng-juan, ZOU Gui-zhen, ZHAO Yu-na

2004, 24(3): 15-20.

[Abstract](1516) [PDF 261KB](271)

Abstract:
The electromagnetic parameters of DT-50/exopy composite system are discussed.Considering the effect of radius,conductance and penetration of ultra-fine absorbent,extended Maxwell-Garnett theory to which the function A(a,σ,εi,ω)is introduced can simulate the electromagnetic properties of the composite system.Maxwell-Garnett formula and extended M-G applies to most composite systems embedded in metal particles but can't calculate the effective EM parameters of uneven system.Extended M-G formula is more accurate.

Study on mechanical properties and dielectric properties of cyanate/epoxy resin system

YANG Jie-ying, LIANG Guo-zheng, REN Peng-gang, WANG Jie-liang, FANG Hong-qiang, GONG Zhao-he

2004, 24(3): 21-25.

[Abstract](1496) [PDF 245KB](376)

Abstract:
Epoxy resin(E-51)was used to improve mechanical properties of cyanate ester resin by copolymerization with bisphenol A dicyanate ester.The influence of epoxy resin concentration,post cure temp-erature,hydrothermal aging and ultraviolet radiation aging on mechanical properties and dielectric properties of modified system was studied.The fracture surfaces of the broken specimens were examined by scanning microscopy(SEM).The modified system showed much higher fracture toughness.Inclusion of 30wt% epoxy resin led to 100% and 50% increase in the impact strength and flexural strength,respectively.The impact strength and flexural strength were found to increase with enhanced concentration of epoxy resin,and modified resin system put up typical toughness rupture.The resin system possessed the best dielectric properties after post cure for 2h at 200℃.Addition of epoxy resin concentration,hydrothermal aging and ultraviolet radiation aging caused increase of the dielectric constant and dielectric loss.However,the modified system belongs to excellent dielectric material,with epoxy resin concentration below 30wt%.

Analytical study of the equivalent elastic parameters for a honeycomb core

LIANG Sen, CHEN Hua-ling, CHEN Tian-ning, LIANG Tian-xi

2004, 24(3): 26-31.

[Abstract](1612) [PDF 296KB](652)

Abstract:
To overcome the drawback of Bernoulli-Euler beam method,the 3D finite element model(FEM)for equivalent analysis has been set up and the equivalent elastic parameters of regular hexagonal honeycomb core with different materials and dimensions have been successfully simulated.The formulas that can calculate equivalent elastic parameters and the new design ideals for honeycomb core plate have been provided.The curves of Nomex equivalent elastic parameters with different geometric dimensions have been plotted and the important results that cannot get in Bernoulli-Euler beam method have been gained by means of numerical simulation.It is fouud that Young's modulus in the y direction is 1.5 times larger than that one in the x direction,and equivalent Poisson's ratio has only relation to geometric parameters etc.Finally the simulative method and the accuracy of the partial formulas have been verified by the compressing experiments with aluminum honeycomb core in the literature [11].The conclusions will have significant reference for the study of a honeycomb sandwich structure.

Study on the mechanisms of electrochemical surface treatment of carbon fibers in H₃PO₄ solution

CAO Hai-lin, HUANG Yu-dong, ZHANG Zhi-qian

2004, 24(3): 32-35,57.

[Abstract](1416) [PDF 246KB](400)

Abstract:
The carbon fibers were electrochemical treated in H3PO4 solution.The treatment mechanisms were investigated using cyclic voltammetry,XPS,SEM and XRD measurements.The results indicated that the electro active substances on the fibers were reacted to produce new active carbon atom under the polarization current in initial stage,then the fibers were oxidized and etched more and more greatly under the couple action of polarization current and the electrolyzation of water.The content of oxygen element on the fiber surface were increased.The concentration of different functional groups which contained oxygen element were changed continuously during the surface treatment period.The carboxyl group and acid anhydride were increased with the treatment time extending.The surface morphology of carbon fibers was rougher and the grooves on the fiber surface were wider and deeper after treatment.Whereas the bulk structure of the fiber was not changed during treatment,the structure of micro crystallite on the fiber surface was changed slightly.

Interfacial bonding and strength of tungsten to copper or its alloy joints with Ti foil and Ti/Ni/Ti multiple interlayers

ZOU Gui-sheng, ZHAO Wen-qing, WU Ai-ping, ZHANG De-ku, HU Nai-jun, HUANG Geng-hua, REN Jia-lie

2004, 24(3): 36-42.

[Abstract](1459) [PDF 350KB](354)

Abstract:
Ti foil and Ti/Ni/Ti multiple interlayers were selected for the bonding of tungsten to copper or CuCrZr alloy with thermal-mechanical simulator Gleeble 1500D.The effects of technology parameters on the microstructures and shear strength of the joints were performed.The interfacial bonding mechanism was studied through microanalysis.When Ti foil was used for bonding of tungsten to pure copper but not transformed into liquid solution during the holding time,a reaction zone including multiple compound layers with brittleness was formed and the strength of the joints was lower.However,if the Ti foil was transformed into liquid solution and extruded mostly out of the bonding zone,the strength of the joints can reach 220MPa due to the chemical and mechanical interfacial bonding.The joint was formed through the diffusion and reaction among the Ti,Ni,Cu and W to form multiple compound layers and solid solution layers when Ti/Ni/Ti was used for bonding tungsten to CuCrZr alloy.Similarly,if Ti foil was transformed into liquid solution,a strong joint can be obtained,otherwise,the strength was relatively low.

Model of double partial transient liquid phase bonding with Si₃N₄ ceramic

ZOU Jia-sheng, CHU Ya-jie, XU Zhi-rong, CHEN Zheng

2004, 24(3): 43-47.

[Abstract](1175) [PDF 243KB](262)

Abstract:
A designed multi-interlayer principle of Ti/Cu/X(X is Ni,Pt,Au,Pd etc)is put forward on the basis of partial transient liquid phase bonding of Si3N4 ceramic.However,X and Cu have mutual solubility both in solid and in liquid.The process of double partial transient liquid phase bonding of Si3N4 ceramic is investigated.A model of double partial transient liquid phase bonding of Si3N4 ceramic is set up,by which the method of selecting parameters is shown.

Study on microstructure and fatigue fracture properties of TC2 titanium alloy welded joints

HUI Li, XIE Li-yang, LIU Jian-zhong, HE Xue-hong, CAO Zhi-tao

2004, 24(3): 48-51.

[Abstract](1503) [PDF 236KB](362)

Abstract:
The microstructure,microhardness,tensile and fatigue properties of TC2 titanium alloy welded joints were investigated.The results show that the welded joints do not have not uniform microstructure and properties.The weld is composed of weave structure with lamellar colonies and existence of martensite α' phases.The HAZ is composed of weave structure with needle α,α' and β phases.The base material is composed of equiaxed structure with α and β phases.The microhardness of the weld is the highest,about 50HV more than that of the base material while the plasticity poorer,The defects in the weld can not be eliminated,which are the main factor affecting the fatigue life.The microhardness and tensile strength of the HAZ is the lowest whereas the plasticity and fatigue property is the best.

Effect of welding processes on fatigue properties of 6061-T6 aluminum welded joints

LI Jing-yong, MA Jian-min

2004, 24(3): 52-57.

[Abstract](1625) [PDF 1049KB](679)

Abstract:
The effect of welding processes(MIG and TIG)on fatigue properties of 6061-T6 aluminum welded joints are analyzed based on fatigue testing.The results shows that the fatigue life of two kinds of joints can settle for the requests of applied objects when loads are under 90% of the tensile strength of welded joints.And the fatigue properties of MIG welded joints are better than those of TIG welded joints,especially under higher loading conditions.Fracture morphologies and microstructures of joints are comparatively fine in the MIG welds with high fatigue life opposed to the TIG welds having comparatively low fatigue life.Fracture morphologies also shows that the fatigue fracture occurred from porosities,inclusions,incomplete joint penetrations and other weld defects and nicks,ect.

A study of the creep stress and strain characteristics of smooth and notched bars

WANG Xin-mei, JANG Yun-peng, WANG Ya-fang, WANG Jian-fang, YUE Zhu-feng

2004, 24(3): 58-62.

[Abstract](1463) [PDF 785KB](286)

Abstract:
The creep stress and strain characteristics of smooth and notched bars are analyzed in the paper.Under net average tensile applied stress,the existence of notches(V-type and U-type)decreases the average Mises stress and axial stress along the minimum sections.Depending on the types of the notches,the maximum stress is not at the tip of notches,since there is creep relaxation in the high stress places.

2004 Vol. 24, No. 3