Search

Conventional drilling is widely adopted to manufacture holes in difficult-to-cut materials such as superalloys. However, as a newer hole processing technology, helical milling possesses several advantages including low cutting forces, reduced tool wear, and improved hole quality. In this study, different hole-making processes like conventional drilling and helical milling were conducted on the superalloy (MSRR7197). Combining the deformation mechanism of the hole wall material, the influence of both hole-making processes on the processing quality of the MSRR7197 were investigated. The experimental results demonstrate that the axial force for the helical milling is about 1/10 of that for the drilling. Compared with drilling, the flank wear, rake wear, and wear of tool tip for the helical milling are smaller. The hole wall quality such as surface morphology and roughness of helical milling is better than that of the drilling. Last but not least, the helical milling can get a higher machining accuracy such as circularity and aperture. Hence, helical milling remains the favorable and alternative to conventional drilling.

The effect of temperature on scratching forces for 16% SiC/Al and 45% SiC/Al composites was investigated in this article. The results showed that the mean normal forces for 16% SiCp/Al and 45% SiCp/Al decreased by 80% and 68% at 300°C compared with 25°C, and the average tangential force decreased by 67% and 66%, respectively. The reason was that the strength of composites was reduced with the increasing temperature, which results in a reduction of flow stresses in the primary shear zones. There are three stages occurring in the scratching process according to the cutting tool interacting with different phases with the increasing temperature. The temperature and the particle contents have an obvious effect on the deformation mechanism by influencing the ratio value of the elastic modulus and hardness. It is founded that the friction coefficient increased fast when the temperatures increased from 25° to 300°C for both 16% SiCp/Al and 45% SiCp/Al composites, and the temperature provided a bigger influence compared with the particle contents. Furthermore, two distinct regions of the hardness variation with the increasing temperature for both two composites were observed: (1) a gradual decrease with the temperature up to 285°C and (2) an abrupt dropping above 285°C. Finally, a physical model representing the deformation process considering the elastic recovery and piles up in high temperature has been developed.

We report on a sequential control scheme to realize a steady, quasi-continuous output of squeezed vacuum states, which eliminates the influence of the seed beam on the squeezing strength. The scheme, originating from time-division multiplexing, separates the generation process from the locking process. We confirm that the sequential control scheme does not reduce the squeezing strength and that the setup operates stably for a 3-h running test, with a duty ratio of 80% and cycle time of 5 s. Therefore, the sequential control scheme opens up a new path of manipulating squeezed vacuum states.

Increasing the conversion efficiency of second harmonic generation (SHG) is an area of interest in research. We report a high-efficiency 532 nm laser generation, with a conversion efficiency of 94.04 ± 0.115% from the pump depletion of 98.1% ± 0.1%, by accurately quantifying the round-trip loss and the transmissivity of the input mirror using our proposed scheme. The optimal conversion efficiency of the cavity-enhanced frequency doubling process is independent of the waist and is determined by the pump depletion, round-trip loss, and transmissivity of the input mirror. These results show that the cavity-enhanced frequency doubling process is not necessary to set the focusing parameter at the optimal single-pass conversion. These results provide a guide for future research on high-efficiency SHG.

The field of squeezed state is an important quantum resource in the study of quantum optics. In the application of quantum information, the spectrum bandwidth of the squeezed light field is an important index to limit the information transmission capacity. Currently, the optical parametric oscillator (OPO) is one of the most efficient ways to generate high squeezed non-classical optical fields. In this paper, the degenerate singly-resonant and doubly-resonant OPO structures are introduced. Both OPOs are composed of concave mirrors and periodically poled potassium titanyl phosphate crystals (PPKTP). The length of PPKTP crystal is 10 mm. The curvature radius of the curved surface is 12 mm, and it has high reflectivity at 1550 nm and 775 nm. The plane surface is coated with anti-reflection coating. The air gap length is 21 mm. The concave mirror is an output coupling mirror, and its radius of curvature is 25 mm. In the singly-resonant OPO, only the signal light resonates in the cavity, and the pump light passes through the nonlinear crystal twice and then outputs out of the cavity. The reflectivity of OPO output coupling mirror to the wavelength of 1550 nm is 88%. The linewidth of the corresponding fundamental frequency wave is 77.4 MHz. For doubly-resonant OPO, both the signal light and the pump light resonate simultaneously in the cavity. The reflectivity of OPO output coupling mirror to 1550 nm and 775 nm is 85% and 97.5%, respectively. The linewidth of the corresponding fundamental frequency wave and harmonic is 97.1 MHz and 15.6 MHz, respectively. Then the threshold of OPO is calculated. The threshold pump power of OPO increases with signal light transmittance increasing, but the threshold value of doubly-resonant OPO is obviously smaller than that of singly-resonant OPO. After that, the variation of the squeezing bandwidth of the squeezed light field generated by OPO with the transmittance of the signal is analyzed. Finally, we complete the design of quantum squeezer with low threshold (18 mW), broadband (84.2 MHz) and high stability (the standard deviation of locking baseline is 0.32 MHz) experimentally. The results show that compared with the singly-resonant optical parametric oscillator, the doubly-resonant cavity has the characteristics of low threshold and high stability, which is more suitable for the preparation and practical application of broadband squeezed light field.