Advanced Materials Research Vols. 532-533

Abstract: Metal vapor plume and spatters are the important phenomena in the process of high power disk laser welding, and there exists a close relationship with the welding stability. The images of metal vapor plume and spatters which captured by a high speed camera during high power disk laser welding were analyzed in this experiment. Image processing techniques such as median filtering, Wiener filtering, gray level threshold and lightness transform were used to process the images so that the image characteristic parameters such as the area and number of spatters in an image, the average gray, mean value, variance and entropy of a spatter gray level image and the coordinate ratio of the centriod of plume and the welding point can be extracted. To reflect the actual welding results obviously by those characteristic parameters, K-L transform method was used to get a new set of characteristic parameters. Experimental results showed that this new set of characteristic parameters could reflect the actual welding effectively.

Abstract: In this study, a 14×6JJ a-alloy automobile wheel was used as the object, the fatigue strength and lifetime of the wheel suffered from varying amplitude load were predicted with a cumulative damage theory (the modified Miner theorem), which was considered to be accurate and secure, based on the analysis of load spectrum. The predicted lifetime was verified using a reliability theory. The results showed that, the modified Miner theorem was reliable in the prediction of the lifetime of an automobile a-alloy wheel.

Abstract: This paper studied the mechanical behavior of composite yarn fabrics and pure cotton yarn fabrics with the conditions of small deformation, then making some comparison. KES-F (Kawabata Evaluation System for Fabric) system was used in the research process. The study shows that the fabric samples made of composite yarn exhibit noticeable improvement on mechanical property after using composite yarn. The results lay a solid foundation for the application and extension of composite yarn fabrics.

Abstract: It is well known that weld pool geometry plays a critical role in laser welding. In this study, an IPG YLR-10000 device was used to capture a series of molten pool images during high power fiber laser welding process. Then an extraction method of the geometric characteristics of these images was developed. This method could be applied to monitor the configuration of a molten pool and keyhole which was related to welding quality. The experimental results showed that this method was a reliable inspection method for monitoring the configuration of molten pool during high power fiber laser welding.

Abstract: Organizations can significantly reduce defects in single crystal nickel-based alloys and plastic creep life, with the creep for the alloy in the near crack region γ' bent along the direction of applied stress axis was 45° angle to form raft-like structure, the circular hole defects Elongated along the stress axis into an oval, and the formation of cracks in the holes on both sides and along the direction perpendicular to the stress axis expansion. During the high temperature creep, the stress near the crack contour region with the disc distribution, along with the applied stress axis orientation angle of 45° have greater value, the stress distribution is converted to γ' phase angle of 45° Raft-like structures of the main reasons. γ' Phase directional coarsening. In this paper, wavelet transform and finite element analysis to simulate the change

Abstract: In this paper, the distribution of surface wind pressure and wind speed of Hangzhou bay bridge, offshore platform and sightseeing tower is numerically simulated based on Fluent. Two turbulence models, standard k ε model and Realizable k ε model, are used. The influence of the wind pressure distribution of the offshore platform and sightseeing tower by Hangzhou bay bridge is also analyzed. And the detailed comparison between numerical simulation and wind tunnel test is given. Results show that the impact of Hangzhou bay bridge on platform and sightseeing tower occurs mainly with the angle of the wind less than 450. When the angle of the wind is more than 450, the impact is little. The upper of the sightseeing tower does not almost suffer the effect of other buildings. The surface pressure of the platform changes from 5% to 15% between under bridge and under non-bridge condition. The surface pressure of sightseeing tower changes from 0.05% to 3%. The influence on the platform by the bridge is significant but not significant on the sightseeing tower. The simulation results of the tower and mast structure given by both standard k ε model and Realizable k ε model find that the windward side is ideal; the crosswind side is the best; the leeward side is less than ideal. By contrast, the Realizable k ε model is a closer correlation with wind tunnel test than standard k ε model.

Abstract: Recycled coarse aggregates obtained by crushed concrete were used for concrete production in this study. Four different recycled aggregate concretes were produced; made with 50% of recycled coarse aggregates of four intensity levels. The damage of the recycled concrete is the bond failure of the interface of aggregate and mortar, which is basically the same as the damage process and damage mechanism of the natural concrete. The strength of recycled concrete was influenced by matrix concrete. When the strength grade of matrix concrete is less than C35, the recycled strength of concrete will be inferior to that of natural concrete basically. But when the strength grade of matrix concrete is higher than C35, the recycled concrete strength will be higher than that of natural concrete.

Abstract: Different contents of epoxy functionalized polyhedral oligomeric silsesquioxane (POSS-Ep) were used to modify cyanate ester resin. The dynamic mechanical properties of the hybrids were studied dynamic mechanical analysis (DMA). DMA results showed that POSS-Ep tended to decrease E’ of the hybrids at the glassy state but to increase E’ of the hybrids at the rubbery state.

Abstract: The secondary throttling pipelines are adopted to improve their cavitation erosion resistance. With the aid of the finite element methods, under the conditions of the inlet velocity of 9 m/s and outlet pressure of zero, it has been calculated that compared to the ordinary throttling pipeline, the secondary throttling pipeline makes the maximum velocity decreased from 43.972 to 39.575 m/s, and the minimum negative pressure increased from -19.39 to -16.04 MPa. The secondary structure of the throttling pipeline has some good effect on the cavitation erosion resistance.

Abstract: Currently, laser ultrasonic nondestructive testing is the best application prospect of nondestructive testing methods. This paper expounds the mechanism and the qualitative analysis of the common defects of the laser ultrasonic inspection and introduces the application of matching pursuit algorithm guided wave testing technology in signal processing. This paper focuses on the laser ultrasonic detection system and analysis of the detected data using the finite element method.