Ni-Ti合金中双程形状记忆速动相变的研究

利用应力对双程形状记忆合金中相变驱动力的制约作用,在Ni-Ti合金中实现了不需附加机构的速动相变和速动双程形状记忆效应。

Numerical analysis of 3D spot continual induction hardening on curved surface of AISI 1045 steel

In order to investigate and predict the material properties of curved surface AISI 1045 steel component during spot continual induction hardening(SCIH),a 3D model for curved surface workpieces which coupled electromagnetic,temperature and phase transformation fields was built by finite element software ANSYS.A small size inductor and magnetizer were used in this model,which can move along the top surface of workpiece flexibly.The effect of inductor moving velocity and workpiece radius on temperature field was analyzed and the heating delay phenomenon was found through comparing the simulated results.The temperature field results indicate that the heating delay phenomenon is more obvious under high inductor moving velocity condition.This trend becomes more obvious if the workpiece radius becomes larger.The predictions of microstructure and micro-hardness distribution were also carried out via this model.The predicted results show that the inductor moving velocity is the dominated factor for the distribution of 100% martensite region and phase transformation region.The influencing factor of workpiece radius on 100% martensite region and phase transformation region distribution is obvious under relatively high inductor moving velocity but inconspicuous under relatively low inductor moving velocity.

Solid−solid phase transition of tungsten induced by high pressure:A molecular dynamics simulation

The phase transition of tungsten(W)under high pressures was investigated with molecular dynamics simulation.The structure was characterized in terms of the pair distribution function and the largest standard cluster analysis(LSCA).It is found that under 40−100 GPa at a cooling rate of 0.1 K/ps a pure W melt first crystallizes into the body-centred cubic(BCC)crystal,and then transfers into the hexagonal close-packed(HCP)crystal through a series of BCC−HCP coexisting states.The dynamic factors may induce intermediate stages during the liquid−solid transition and the criss-cross grain boundaries cause lots of indistinguishable intermediate states,making the first-order BCC−HCP transition appear to be continuous.Furthermore,LSCA is shown to be a parameter-free method that can effectively analyze both ordered and disordered structures.Therefore,LSCA can detect more details about the evolution of the structure in such structure transition processes with rich intermediate structures.

Properties of Phase Transition of Traffic Flow on Urban Expressway Systems with Ramps and Accessory Roads

In this paper, we develop a cellular automaton model to describe the phase transition of traffic flow on urban expressway systems with on-off-ramps and accessory roads. The lane changing rules are given in detailed, the numerical results show that the main road and the accessory road both produce phase transitions. These phase transitions will omen be influenced by the number of lanes, lane changing, the ramp flow, the input flow rate, and the geometry structure.

Close-Contact Melting Around a Hot Sphere

A more general model describing PCM close-contact melting outside a hot sphere is devel0ped withthe aid of introducing a parameter a and presenting a supplementary equation for the first time in thispaper. The governing integral-differential equations are solved by numerical method. The melt-filmthickness variation along the surface of sphere is obtained reasonably due to the consideration of theinterface shape more precisely. The calculation results of Peclet number, heat transferred and pressuredistribution are also compared with that in literature. The model presented in this paper can describethe whole close-contact region and the whole contact melting process. Closeeontact melting in spher-ical or cylindrical capsules to which the model can be extended is also discussed brielly.