The developments of constitutive models for shape memory polymer (SMP) have been motivated by its increasing applications. During cooling or heating process, the phase transition which is a continuous time-dependent process happens in semi-crystallize SMP and the various individual phases form at different temperature and in different configuration. Then, the transformation between these phases occurred and shape memory effect will emerge. In addition, stress applied on SMP is an important factor for crystal melting during phase transition. In this theory, an ideal phase transition model considering stress or pre-strain is the key to describe the behaviors of shape memory effect. So a normal distributed model was established in this research to characterize the volume fraction of each phase in SMP during phase transition. Generally, the experiment results are partly backward (in heating process) or forward (in cooling process) compared with the ideal situation considering delay effect during phase transition. So, a correction on the normal distributed model is needed. Furthermore, a nonlinear relationship between stress and phase transition temperature Tg is also taken into account for establishing an accurately normal distributed phase transition model. Finally, the constitutive model which taking the stress as an influence factor on phase transition was also established. Compared with the other expressions, this new-type model possesses less parameter and is more accurate. For the sake of verifying the rationality and accuracy of new phase transition and constitutive model, the comparisons between the simulated and experimental results were carried out.
Shape memory alloy (SMA) tube is an perfect candidate used to design the torsion actuator in the self-adaptive wings.
In this paper, the thermo-mechanical property of SMA torsion thin-walled tube is investigated based on Zhou's threedimensional
constitutive model of SMA, which include the three-dimensional phase transformation equation and the
three-dimensional mechanical constitutive equation, and material mechanics. The phase transformation equation
describing the relationship between torque and martensitic volume fraction of SMA torsion thin-walled tube is
established based on Zhou's three-dimensional phase transformation of SMA. The mechanical equation is established to
express the relationship of torque, temperature and torsion angle of the SMA torsion thin-walled tube based on Zhou's
three-dimensional mechanical constitutive equation and material mechanics. The thermo-mechanical behaviors of SMA
torsion thin-walled tube are numerically simulated by using the established mechanical equation and phase
transformation equation together. Numerical results show the established mechanical equation and phase transformation
equation well predict the thermo-mechanical behaviors of SMA torsion thin-walled tube.
As a novel smart material, shape memory polymer possesses the special thermo-mechanical property of shape memory
effect. Its shape memory effect is closely related to the glass transitions between the glass state and rubber state induced
by temperature changing. It is of engineering and theoretical meaning to investigate and describe the glass transition
behaviors of shape memory polymer. In this study the glass transition behaviors of an epoxy-based shape memory
polymer containing linear epoxy monomer are investigated using the tests of dynamic mechanical analysis. Results show
both glass transition critical temperatures and storage modulus at rubber state of the epoxy-base shape memory polymer
decrease as the content of linear monomer in such material increases. However the transition temperature width increases
as the linear monomer content increases. A new glass transition model is supposed to describe the glass transition
behaviors of epoxy-based shape memory polymer based on the experimental results. Numerical simulations show that
the new glass transition model well predicts the glass transition behaviors of the epoxy-based shape memory polymer
containing linear epoxy monomer.
Dynamic mechanical analysis (DMA) tests are conducted on the styrene-based shape memory polymer (SMP) to
investigate its state transition behaviors. Tensile tests at various constant temperatures are carried out to reveal the stressstrain-
temperature relationship of the styrene-based SMP. A new mechanical constitutive equation is developed to
describe the stress-strain-temperature relationship of the styrene-based SMP. Numerical calculations illustrate the
proposed theory well describes the thermo-mechanical cycle of shape memory of styrene-based SMP, such as
deformation at high temperature, shape fixity, unloading at low temperature and shape recovery.
Dynamic mechanical analysis(DMA) tests are conducted on styrene-based fiber reinforced shape memory polymer (SMP)
to investigate its glass transition behaviors. Results show the properties of stiffness, damping and energy dissipation of
the reinforced SMP are obviously better than that of the pure SMP during the process of glass transition. Static threepoint
bending tests are performed on the reinforced SMP to determine its stiffness and strength. Results show the
reinforcement in the reinforced SMP improve the material properties of stiffness and strength at the room temperature.
Cyclic three-point bending tests are operated to study the material training effect of the reinforced SMP. A training
evolutional equation is established to describe the material training effect of the reinforced SMP. Numerical results
show the training evolutional equation is able to predict the material training effect of the reinforced SMP effectively.
The stress-strain relationship and phase transformation behavior of shape memory alloy (SMA) in pure shear state are
investigated by using Zhou's SMA micromechanical constitutive equation of 3-dimension and Zhou's SMA phase
transformation equation of 1-diemsion respectively. Then thermo-mechanical model describing thermo-mechanical
behaviors of SMA torque thin-walled tube is established based on the stress-strain relation and phase transformation
model of SMA in pure shear state. The relations of torque vs. rotation, recovery rotation vs. temperature and recovery
torque vs. temperature of the torque tube are numerically simulated by using the thermo-mechanical model.
Two types of plasma shutters which can achieve pulse shaping of transversely excited atmospheric-pressure (TEA) CO2 laser are presented. We have designed two optical devices, which are plasma shutter and laser triggering spark gas (LTSG). The pulse forming network circuit used for precise triggering control is designed. In experiment, optical triggering gas free-breakdown plasma shutter and electrical triggering plasma shutter controlled via LTSG are researched for pulse shaping of the TEA CO2 laser. The collimated laser beam is focused at the center of two ZnSe lenses, producing an intensity of approximately 7x 1O'°W/cm2. In order to optimize truncated laser pulses, some operating parameters which include gas types filled in plasma shutter, gas pressure, LTSG 's voltage, and so on, are investigated via experiments. Using this technique, the nitrogen "tail" of the TEA CO2 laser pulse can be clipped, thus shortening the output laser pulse from the duration ~60ns to ~30ns.
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