The constitutive relation and electromechanical stability of Varga-Blatz-Ko-type compressible isotropic dielectric
elastomer is investigated in this paper. Free-energy in any form, which consists of elastic strain energy and electric
energy, can be applied to analyse the electromechanical stability of dielectric elastomer. The constitutive relation and
stability is analyzed by applying a new kind of free energy model, which couples elastic strain energy, composed of
Varga model as the volume conservative energy and Blatz-Ko model as the volume non-conservative energy, and electric
field energy with constant permittivity. The ratio between principal planar stretches m(t0) (λ2 = m(t0)λ1), the ratio
between thickness direction stretch and length direction stretch 0 n(t0) (λ3 = n(t0)λ1 ), and power exponent of the
stretch k(t0) are defined to characterize the mechanical loading process and compressible behavior of dielectric
elastomer. Along with the increase of material parameters m(t0) , n(t0) , k(t0) and poison ratioV , the nominal
electric field peak is higher. This indicates that the dielectric elastomer electromechanical system is more stable.
Inversely, with the increase of the material parameter α , the nominal electric field peak, critical area strain and the
critical thickness strain increase, coupling system is more stable.
Cutting heat is one of the important physical subjects in the cutting process. Cutting heat together with cutting
temperature produced by the cutting process will directly have effects on the tool wear and the life as well as on the
workpiece processing precision and surface quality. The feature size of the workpiece is usually several microns. Thus,
the tiny changes of cutting temperature will affect the workpiece on the surface quality and accuracy. Therefore, cutting
heat and temperature generated in micro-milling will have significantly different effect than the one in the traditional
tools cutting. In this paper, a two-dimensional coupled thermal-mechanical finite element model is adopted to determine
thermal fields and cutting temperature during the Micro-milling process, by using software Deform-2D. The effect of
tool edge radius on effective stress, effective strain, velocity field and cutting temperature distribution in micro-milling
of aluminum alloy Al2024-T6 were investigated and analyzed. Also, the transient cutting temperature distribution was
simulated dynamically. The simulation results show that the cutting temperature in Micro-milling is lower than those
occurring in conventional milling processes due to the small loads and low cutting velocity. With increase of tool edge
radius, the maximum temperature region gradually occurs on the contact region between finished surfaced and flank face
of micro-cutter, instead of the rake face or the corner of micro-cutter. And this phenomenon shows an obvious size
effect.
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