For great progress in heat pipe technology, a micro heat pipe has become an ideal heat dissipating device in high heat-flux electronic products, and capillary limit is the main factor affecting its heat transfer performance. Based on analyses of capillary limit and currently commonly-used groove structures, this paper built capillary limit models for micro heat pipes with dovetail-groove, rectangular-groove, trapezoidal-groove and V-groove wick structures respectively for theoretical analyses. The analysis results show that better heat transfer performances can be obtained in micro heat pipes with small-angle dovetail (i.e. a sector structure), rectangular and small-angle trapezoidal grooved wick structures when groove depth is 0.2-0.3mm and top-width-to-depth ratio is 1.2-1.5.
With increasing demands for product quality, and the performance of assembly equipment plays a decisive role for product quality, national experts and scholars conduct in-depth research on the performance of the assembly equipment. In this paper, a research simulation on hydrostatic bearing performance of heavy-duty vertical lathes DVT(digital vertical tool) 500 is carried out by using finite element software FLUENT to simulate the fluid pressure field and temperature field distribution of sector oil recess at different work platform rotational speed. The law of these field distributions is also obtained. The results show that: the rotational speed of the work platform has a greater impact on pressure field and temperature field of gap fluid flow. Numerical results can reflect the true hydrostatic bearing fluid movement, the actual simulation results provide a theoretical basis for optimization design of the Engineering hydrostatic bearing oil cavity.
The manufacturing process of micro-grooves inside thin-walled copper heat-pipe is always
complicated and difficult. Separately adopted GCr15 and W18Cr4V multi-tooth mandrel, a series of
experiments have been done to machine axially inner micro-grooves of micro-heat-pipe with oil-filled
steel-ball spinning technology to analyze the mandrel effect and failure mechanism. It was studied
how the tooth-shape of multi-tooth mandrel affects the inner micro-groove shape of the copper tube
and how the working position of multi-tooth mandrel affects groove-wall surface morphology and
groove path. The wear and fracture characteristics of multi-tooth mandrel are introduced. It is proved
that the form of GCr15 mandrel failure in machining micro-grooves is tooth-broken or
tooth-collapsed, and its service life is short. Differently, the form of W18Cr4V mandrel failure is felt
wear, and its service life is long.
Using the finite element analysis software ABAQUS, simulation experiments on physical nonlinearity, geometric nonlinear, nonlinear finite element, elastic-plastic in the cutting process are conducted, which realize the separation of chips and working piece combined with material failure criterion, shear failure, adaptive grid technique in ABAQUS. Meanwhile, the stress field, strain and temperature field and cutting force in the cutting simulation are obtained consistent with cutting theory.
Empirical mode decomposition (EMD) provides a powerful tool for the nonlinear and nonstationary signals. This paper presents an application of the signature analysis based on high-order spline interpolation. The time-frequency analysis method based on EMD is introduced. The series data are separated into intrinsic mode functions (IMFs) with different time scale using EMD. The spectrum of Hilbert transformation is obtained by applying Hilbert transformation to every IMF. Based on cubic spline interpolation, high-order spline interpolation is used to improve the precision of the algorithm. Furthermore some strategies for improving the computational efficiency are proposed. The simulation result shows that the precision of the time-frequency analysis can be improved effectively using the proposed new algorithm.
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