大型船舶桨舵安装平台同步控制

船舶舵叶和螺旋桨处于船艉,其安装位置空问相对封闭、狭窄.采用有效的可行走的安装台车安装舵叶和螺旋桨,是世界各国船厂通用方法,可以提高安装效率,大幅度缩短船坞周期.提出了一种带传感器构成的闭环液压系统设计,用以确保台车平台的四个升降驱动液压缸能作同步运动,使平台以稳定的状态升降,提高安装安全性.     

焊接电流和保护气体对大电流MAG焊焊缝成形的影响

在相同线能量下，研究了焊接电流与不同组元保护气体(Ar、He、CO2、O2)对大电流MAG焊焊缝成形的影响。结果表明，随着电流的增大，焊缝表面由光亮平滑变为发黑起皱；焊缝截面熔池形状由指状过渡为锥形。再发展为盆形。用无He保护气体，熔池形状大电流时为蘑菇形，小电流时为指状，都不理想；大电流情况下，含He的混合气体调节范围较宽，且焊缝熔池形状比较理想，这使大电流时选用气体配比比较容易，只要保证电弧形态和熔滴过渡稳定即可，所以含He的保护气体适合于大电流的MAG焊接。     

Analysis of arc physical property of pulsed tungsten inert gas welding based on Fowler-Milne method

Pulsed tungsten inert gas (TIG) welding is widely used in industry due to its superior properties, so the measurement of arc temperature is important to analyse welding process. Arc image of spectral line in 794.8 nm is captured by high speed camera; both the Abel inversion and the Fowler-Milne method are used to calculate the temperature distribution of the pulsed TIG welding. Characteristic of transient variation in arc intensity and temperature is analyzed. When the change of current happens, intensity and temperature of arc jump as well, it costs several milliseconds. The further the axial position from the tungsten is, the greater the intensity jumps, and the smaller the temperature changes.     

Modified gray level difference-based thresholding segmentation and its application in X-Ray welding image

Thresholding is a popular image segmentation method that often requires as a preliminary and indispensable stage in the computer aided image process, particularly in the analysis of X-ray welding images. In this paper, a modified gray level difference-based transition region extraction and thresholding algorithm is presented for segmentation of the images that have been corrupted by intensity inhomogeneities or noise. Classical gray level difference algorithm is improved by selective output of the result of the maximum or the minimum of the gray level with the pixels in the surrounding, and multi-structuring of neighborhood window is used to represent the essence of transition region. The proposed algorithm could robustly measure the gray level changes, and accurately extract transition region of an image. Comparisons with other approaches demonstrate the superior performance of the proposed algorithm.     

焊接线能量对12Ni19钢焊接接头中裂缝和夹杂物行为的影响

本文采用着色检查，光学显微镜观察，扫描电子显微镜观察和EDAX分析，研究了焊接线能量对TN－115焊条所焊的12Ni19钢角接 头和对接头中裂缝形貌及夹杂物形态组元的影响。结果表明，当线能量过小时，易在焊缝中形成夹渣，导致接头侧弯性能变差；若线能量过大，导致δ相转变成脆性σ相，严重时会在多层焊层间产生微裂缝。