Abstract: In this paper, 3-dimension finite element model was applied to analyze the commercial
pure Ti billet subjected to four-pass equal channel angular extrusion process at 400°C with Bc route.
The effective strain distribution and the damage within up to four-pass were described with friction
conditions in 3D. The propensity for cracks was predicted, which did correlate approximately to the
Abstract: L10 phase FePt alloy is regarded as one of the most promising materials for ultra high
density magnetic recording media. However, structural point defects, which would reduce the media's
signal to noise ratio, are inevitable in non-stoichiometric L10 FePt alloy. Hence, possible types of
point defect (vacancy and anti-site defect) in non-stoichiometric ordered FePt alloy were fully studied
using density functional theory. Investigation over vacancy shows the formation energy of Fe and Pt
vacancy is respectively 2.58eV and 3.20eV. Geometry relaxation implies Fe vacancy has a stronger
deformation force upon the original lattice. Meanwhile, anti-site defect study shows that the
formation energy of Fe anti-site (Fe occupation in Pt sublattice) and Pt anti-site (Pt occupation in Fe
sublattice) is respectively 1.05eV and 0.66eV. Therefore, for Fe-rich and Pt-rich alloy, the preferred
structural point defects are both anti-site substitution rather than vacancy due to the much lower
Abstract: The goal of this work is to describe the cosmic micromechanics connection with
irreversible deformation processes in spatially extended polycrystalline systems, where the nature of
the crystalline structure of the universe in a relativistic framework at Max Plank scale and Edwin
Hubble scale play and important role. In this physical construction by applying the theoretical
model of Muñoz-Andrade the activation energy for irreversible deformation processes in spatially
extended polycrystalline systems is obtained. Consequently, the main results of this work are
analyzed in the context of the unified interpretation of Hubble flow, plastic flow and super plastic
Abstract: The mechanical, thermal and electronic properties of the nanoscale materials are studied
using an ab initio molecular dynamics (TBMD) method and statistical moment method (SMM). We
investigate the mechanical properties of nanoscale materials like carbon nanotubes (CNT), graphens
and nanowires in comparison with those of corresponding bulk materials. The electronic density of
states and electronic transports of the nanoscale materials, with and without the atomistic defects
are also discussed. We will show that the thermodynamic and strength properties of the nanoscale
materials are quite different from those of the corresponding bulk materials.
Abstract: Phase Field Method is combined with the Cluster Variation Method within the square
approximation, and the multiscale ordering behavior from atomistic to microstructural evolution
process of ordered domains in the two dimensional square lattice is investigated. The transition
temperature is determined at 1:1 stoichiometric composition and it is confirmed that the transition is
of the second order. The growth process of the ordered domains is visualized and it is revealed that the
sharp decrease of the free energy takes place during the process.
Abstract: In this paper, the thermodynamic and kinetic requirements of heterogeneous and
homogeneous nucleation of metallic melting were suggested. Based on the kinetic requirements of
nucleation, the mathematic model of wetting angle of heterogeneous nucleation was developed,
Based on the wetting angel model, it was predicted that the maximum undercooling of homogeneous
nucleation for melts is two thirds of melting temperature. With the wetting angel model, the wetting
angles of different catalysts in liquid iron were calculated, and calculation results are in agreement
with that of other researchers.
Abstract: The bending tool design of a cold roll-formed blank has been discussed in this paper. The
cold roll-formed blanks give a up and down bending line instead of a conventional straight line, The
problems of wrinkling and edge irregularity occured frequently in such bending operation. A die
design and blank pre-cutting methods are proposed in this paper to eliminate the edge irregularity.
The radii of die and punch, punch profile, the gap of tools are considered as the design factors. The
CAE method is adopted to obtain the measurements of the design of experiments (DOE). A
fourth-order Bezier curve is proposed to desing the pre-cutting curve systemtically and automaticaly.
The Golden section method is adopted to improve the pre-cutting curve design. The edge iregularity
of a cold roll-formed balnk can be minimised by the proposed method. The wrinkling defects can be
decreased but are not able to fuly elimiated.
Abstract: The conventional method of bending the large crankthrow was investigated by computer
simulation combined with manufacturing trial, and the typical forging defects, such as constricted
waist, folded cracks and horn mouth on forged blank were analyzed. On the basis of these results, a
novel forging shape of preformed blank was proposed using anti-transformation method by
computer simulation. The FEM simulated results show that all the above defects can be avoided by
carrying out the novel method, furthermore, the maximum resistance of the novel bending
deformation was reduced to 72% of conventional process, and the weight of forging blank can be
decreased by 15%. Finally, the optimum forging shape was applied to the actual process, the
simulation results were confirmed by manufacturing trial, and qualified forged piece was gained.
The FEM model established can be used for further optimization of other types of crankthrow.
Abstract: A physical model for austenite recrystallization of steel concerning TMCP is developed.
Dislocation density plays a key role as recrystallization driving force. The dislocation density change
is a result of competition between dislocation generation and dynamic recovery. Recrystallization is
described as a nucleation-growth process. An abnormal subgrain growth mechanism is introduced for
nucleation. A few subgrains fulfilling abnormal growth conditions will stand out and become nuclei
of recrystallization. The recrystallized grain grows to the deformed materials driven by the stored
energy. Oswald ripening occurs for grains surrounded by recrystallized grains. The models were
verified by laboratory simulation results for selected austenite stainless steels. It showed good
agreement between predicted and experimental results.
Abstract: Functionally gradient material (FGM) developed for heat-shielding structure is often used
in the very high temperature environment. Therefore, the material property parameters are not only
functions of spatial coordinates but also ones of temperature. The former leads to partial differential
equations with variable coefficients, the latter to nonlinear governing equations. It is usually very
difficult to obtain the analytical solution to such thermal conduction problems of FGMs. If the finite
element method is adopted, it is very inconvenient because material parameter values must be
imputed for each element. Hence, a semi-analytic numerical method, i.e., method of lines (MOLs)
is introduced. The thermal conductivity functions do not need to be discretized and remain
original form in ordinary differential equations. As a numerical example, the nonlinear steady
temperature fields are computed for a rectangular non-homogeneous region with the first, the
second and the third kinds of boundary conditions, where three kinds of functions, i.e. power,
exponential and logarithmic ones are adopted for the thermal conductivity. Results display the
important influence of non-linearity on temperature fields. Moreover, the results given here provide
the better basis for thermal stress analysis of non-homogenous and non-linear materials.