Abstract: By incorporating the Taylor-based nonlocal theory of plasticity, the finite element
method (FEM) is applied to investigate the effect of particle size on the deformation behavior of the
metal matrix composites. In the simulation, the two-dimensional plane strain and random
distribution multi-particles model are used. It is shown that, at a fixed particle volume fraction,
there is a close relationship between the particle size and the deformation behavior of the
composites. The yield strength and plastic work hardening rate of the composites increase with
decreasing particle size. The predicted stress-strain behaviors of the composites are qualitative
agreement with the experimental results.
Abstract: To improve the strength-toughness and heat-resistance of die cast magnesium alloy, the
ZA85 alloy has been prepared by adding proper amount of spherical quasicrystals containing master
alloy. The results indicate that the solidification microstructure is inlaid with quasicrystal particles,
which is a new phase i(Mg45Zn47Y5Mn3), co-existing with the α-Mg, Φ(Al2Mg5Zn2) phase and
τ(Mg32(AlZn)49) phase. Mechanical properties of ZA85 alloys have been dramatically improved
owing to the obvious grain refinement of the matrix microstructure. While adding 1.7 wt %
spherical quasicrystal containing master alloy, macro-hardness of ZA85 magnesium alloy reaches
75HB; meanwhile, impact toughness reaches the peak value 18.4Jcm-2, which is about 202% of
ZA85 base alloy. Due to the pinning effect of quasicrystal particles on grain boundaries, the
strengthened ZA85 alloys would have excellent heat-resistance.
Abstract: Curved panels can bear more lateral load than flat plates because they can transmit the
external load along curved surface in addition to load-carrying capacity by the bending stiffness. For
curved panels, however, there is a critical point of the lateral load that structure can endure before it
buckles. On the other hand, composites are known to have more advantages in specific strength and
stiffness than conventional metal materials. The present paper proposes a semi-analytical method to
predict the initial buckling loads of slightly curved panels composed of thin orthotropic composite
layers under general boundary conditions. Based on the Donnell type theory, the potential strain
energy is evaluated as a sum of stretching energy, stretching-bending coupling energy and bending
energy, and the external work done by uniform external pressure is included in the functional. The
eigenvalue equation is derived by the Ritz method to yield such initial buckling load parameters as
eigenvalues. Numerical examples include a list of buckling loads and the corresponding buckling
patterns for typical panels with simply supported and clamped edges.
Abstract: SiCw/Al-18Si composites were prepared by squeeze casting technique. SiCw/Al-18Si
composites were remelted before solidification. The effects of volume fraction of SiC whisker on
solidification behavior of SiCw/Al-18Si composites were investigated by means of differential
scanning calorimetry (DSC) technique and microstructure observation. DSC results indicated that the
start solidification temperature and primary silicon peak temperature decreased gradually and the
degree of supercooling increased with the increasing of SiC whisker content. SiC whisker and Sr
decreased the average size of Si phases and improved the mechanical properties of the composites.
Abstract: Extrusion experiments have been carried out on Bi2O3-coated Al18B4O33 whisker
reinforced aluminum matrix composite. The effects of the extrusion temperature on the
microstructures, the formability and the mechanical properties of ABOw reinforced aluminum
(ABOw/Al) composites with and without Bi2O3 coating were investigated. The results show that the
steady-state extrusion load and the probability of whisker fracture of the extruded two composites
decrease with the extrusion temperature increasing. The mechanical properties of the composites
attain highest values at extrusion temperature of 673K.
Abstract: The effect of temperature on strain softening behavior of composites with small
misaligned whiskers is investigated. The results show that the temperature affects the matrix and
whisker mechanical behavior and corresponding composite deformation behavior. With increasing
temperature, the whisker rotation angle increases, but their breakage decreases. Meanwhile
elevating temperature not only reduces the matrix flow stress and work hardening rate, but also
decreases load transfer from the matrix to the whiskers and stress induced by the whisker rotation
and breakage.It is found that during hot compression, strain softening behavior of composites
decreases as temperature increases.
Abstract: Thermal barrier coating (TBC) was carried out on Ni based super-alloy specimens, and edge
indent tests were carried out at 1073K under different displacement rate. In addition, the specimens were
heated and held at 1273K for long time, and the edge-indent tests of the specimens were performed both
at 1273K and at room temperature. The results showed that the delamination load Pd and the
delamination energy Ed measured at 1073K after short time holding were larger than those measured at
room temperature, and the Pd and Ed slightly decreased with increasing displacement rate at 1073K while
they slightly increased at 293K. The Pd and Ed at 1273K increased with increasing holding time and
reached a maximum at 1400ks. With further increase in holding time, the Pd and Ed largely decreased.
The Pd and Ed measured at 1273K were smaller than those at room temperature.
Abstract: The residual stresses induced in functionally graded medium (FGM) with inhomogeneity
cooling down from the processing temperature are determined with concentric cylinder model and
analytical solutions of the inhomogeneous governing equations for displacement components. The
analytical solutions derived here are general for power-law variations of the elastic moduli of the
FGM. With a power exponent, analytical expressions for the residual stresses of FGM with
inhomogeneity can be obtained. By changing the power exponent and the coefficient of the power
terms, the solutions obtained here could be applied to different properties of FGM with
inhomogeneity. The results show that the huge difference exists between FGM with inhomogeneity
and homogeneous medium with inhomogeneity. The variations of FGM and inhomogeneity size
have a great deal of effect on the residual stresses in FGM.
Abstract: Electrical resistance change method has been applied to monitor a delamination crack of
a thin CFRP laminate. For a thick CFRP laminate, multiple delamination cracks are made with
many matrix cracks, and the electric current in the thick CFRP laminate may not flow in the
thickness direction due to the strong orthotropic electrical conductivity. The present study employs
an electric impedance change method for the identification of damage location and dimension of the
damaged area; applicability of the method is investigated experimentally using thick beam-type
specimens fabricated from cross-ply laminates of 36 plies. After making the damage, electrical
impedance was decreased. A residual stress relief model was proposed to explain the decrease.
From the measured electrical impedance changes, the relationships between the electrical
impedance changes and damages are obtained by means of response surfaces. The response surfaces
estimated the damage location and dimension of the damaged area exactly even for the thick CFRP
laminates. The electrical impedance change method can be used as an appropriate sensor for
measurement of residual stress relief due to damages of thick CFRP laminates.