Active-passive radial-additive friction stir repairing of mechanical hole out of dimension tolerance of AZ31 magnesium alloy

In order to avoid the depth increasing of repaired hole and eliminate the super-fine grain band in stir zone by radial-additive friction stir repairing(R-AFSR), a solid-state repairing technique of active-passive radial-additive friction stir repairing(AP-RAFSR) assisted by the truncated cone-shaped filling material was proposed in this study. The mechanical hole out of dimension tolerance of AZ31 magnesium alloy was chosen as the repaired object. The results indicated that the AP-RAFSR process rather than the R-AFSR process avoided the kissing bond in the bottom of the repairing interface under the condition of the tool pin length equal to the height of the standard mechanical hole.The continuously-distributed and large-length super-fine grain bands were eliminated in the stir zone by AP-RAFSR. The maximum tensile and compressive-shear strengths of repaired hole by AP-RAFSR reached 190.6 MPa and 138.9 MPa at 1200 rpm respectively, which were equivalent to 97.7% and 89.6% of those of the standard mechanical hole. This AP-RAFSR process assisted by the truncated cone-shaped filling material provides a new technique to obtain a no-depth-increasing, defect-free and high-strength repaired mechanical hole.

Adaptive luminance adjustment and neighborhood spreading strength information based view synthesis

View synthesis is an important building block in three dimension（3D） video processing and communications.Based on one or several views,view synthesis creates other views for the purpose of view prediction（for compression） or view rendering（for multiview-display）.The quality of view synthesis depends on how one fills the occlusion area as well as how the pixels are created.Consequently,luminance adjustment and hole filling are two key issues in view synthesis.In this paper,two views are used to produce an arbitrary virtual synthesized view.One view is merged into another view using a local luminance adjustment method,based on local neighborhood region for the calculation of adjustment coefficient.Moreover,a maximum neighborhood spreading strength hole filling method is presented to deal with the micro texture structure when the hole is being filled.For each pixel at the hole boundary,its neighborhood pixels with the maximum spreading strength direction are selected as candidates;and among them,the pixel with the maximum spreading strength is used to fill the hole from boundary to center.If there still exist disocclusion pixels after once scan,the filling process is repeated until all hole pixels are filled.Simulation results show that the proposed method is efficient,robust and achieves high performance in subjection and objection.

Radial Additive Friction Stir Repairing of Mechanical Hole Out of Dimension Tolerance of AZ31 Magnesium Alloy Assisted by Stationary Shoulder:Process and Mechanical Properties

Radial additive friction stir repairing(R-AFSR)assisted by stationary shoulder was put forward in the present study,which can be employed to repair the mechanical hole out of dimension tolerance of AZ31 magnesium alloy sheet.The results show that the stationary shoulder has sealed-barrier,heat-sink and extra-forging effects.The heat-sink effect improves the microstructure uniformity along the stir zone(SZ)thickness and the surface appearance of repaired hole,and the sealedbarrier and extra-forging effects eliminate the super-fine grain band in the SZ.Therefore,these three effects improve the formation quality of repaired region,thereby enhancing the mechanical properties of repaired mechanical hole compared with conventional R-AFSR.The tensile and compressive shear strengths of the repaired hole by stationary shoulder R-AFSR both increase first and then decrease when the rotating speed changes from 1200 to 1800 rpm,and these maximum values,respectively,reach 190±3 MPa and 64.5±2 MPa at 1400 rpm.The addition of stationary shoulder during R-AFSR can obtain a higher-quality repaired hole and broaden the repairing process window.

Structure formation dynamics in drawing silica photonic crystal fibres

The special features of photonic crystal fibres（PCFs）are achieved by their air hole structures.PCF structure is determined and formed by its origin preform design and drawing process.Therefore,structure formation dynamics in drawing PCF is important for the fabrication of PCF achieving desirable structure and thus the intended feature.This paper will investigate structure formation dynamics of PCF drawing in relation to key parameters and conditions,such as hole dimension,temperature,pressure,etc.