The cure of unsaturated polyester resins (UPR) is accompanied with a high degree of polymerization shrinkage of about 7-10%, which can generally be reduced by adding thermoplastics as low profile additive (LPA). Here the design of a dilatometer was presented for the measurement of the volume change of unsaturated polyester resin system containing low profile additives. According to experimental results, the shrinkage of the UPR system used during cure was not only related to temperature, LPA type, the molecular weight and the concentration of LPA, but also linked strongly with the competition between the shrinkage induced by resin polymerization and the volume compensation by LPA. PVAc was more effective for volume compensation than other LPAs (Polystyrene, Polymethyl methacrylate) and there existed an optimal concentration of LPA for shrinkage control, as were demonstrated in the paper.
Nanomachining tests have been conducted on single-crystal Al using atomic force
microscope to simulate single-blade machining process of single gain. The influences of
nanomachining experimental parameters (lateral feed and velocity) on the properties of engineering
surface, material removal and chip formation were studied. Results indicated that the cutting depth
of nanomachined surface increased as the lateral feed decreased. Insensitivity of cutting depth to
velocity at same normal load was revealed. The different chip behaviors of nanomachined surface
were investigated through scanning electron microscope (SEM). Results indicated that different
lateral feeds caused different chip behaviors. Three typical chip behaviors were characterized as the
lateral feed increased. In addition, the chip behavior and the volume of material removed were
observed having no evident linear transformation with the evolution of the velocity by SEM
graphics. Furthermore, it was concluded from the chip behaviors in nanomachining process that the
material at high loads was removed by plastic deformation with no fracture or crack happened.
In this paper, mechanical characteristics of KDP crystal anisotropy are analysed
theoretically. Vickers indentation experiments are adopted to validate the variation rule of hardness
and fracture toughness in different orientation of KDP crystal plane (100), and a model to calculate
critical cutting thickness of brittle-ductile transition is proposed for the KDP crystals. The result
shows that, on the crystal plane (100), the minimum value of critical cutting thickness of KDP
crystal in brittle-ductile transition appears in the direction [110], but the maximum appears in the
direction [010]. Finally, the ultra-precision machining of KDP crystal is performed, and the results
agree well with the theoretical conclusions. Super-smooth surface with a roughness RMS of 6.6nm
is reached as machined in the crystal direction [010], and 11.2nm to the direction [110].
The method of single point diamond turning is used to machine KDP crystal. A regression analysis is adopted to construct a prediction model for surface roughness and cutting force, which realizes the purposes of pre-machining design, prediction and control of surface roughness and cutting force. The prediction model is utilized to analyze the influences of feed, cutting speed and depth of cut on the surface roughness and cutting force. And the optimal cutting parameters of KDP crystal on such condition are acquired by optimum design. The optimum estimated values of surface roughness and cutting force are 7.369nm and 0.15N, respectively .Using the optimal cutting parameters, the surface roughness Ra, 7.927nm, and cutting force, 0.19N, are obatained.
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