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Angular-based spatially resolved laser-induced breakdown spectroscopy: a new technique for the effective enhancement of signals without an external time delay system 被引量:3
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作者 Qingyu Lin Xu Wang +5 位作者 guanghui niu Hongjun Lai Xiaoqin Zhu Kunping Liu Tao Xu Yixiang Duan 《Chinese Science Bulletin》 SCIE EI CAS 2014年第27期3377-3384,共8页
In this study, we developed a novel angularbased spatially resolved laser-induced breakdown spectroscopy(ABSR-LIBS) technique. This new method allows the spatially resolved spectroscopic properties of laserinduced pla... In this study, we developed a novel angularbased spatially resolved laser-induced breakdown spectroscopy(ABSR-LIBS) technique. This new method allows the spatially resolved spectroscopic properties of laserinduced plasma to be investigated using different angles and polar distances with a spatially adjustable fiber optics probe. The experimental evaluations suggested that the intensity of the Al signal distributions in the ‘‘side-view''depended greatly on the angle of the collection probe. The location of a collection probe at 50° would facilitate efficient spectral collection and minimize the disturbance of the plasma plume. The spectral signals in the plasma emissions had different distribution at various polar distances using the same collection angle, and the highest signal intensity was observed between 15 and 35 mm polar distances. This ABSR-LIBS technique improved both the LIBS signal and the maximum emission intensity of Al atoms by several times at the best spatial position in our experimental conditions. Furthermore, we successfully obtained well-resolved line emission spectroscopy signals without any external time delay using a nongated spectrometer based on the ABSR-LIBS system. We consider that the ABSR-LIBS technique has great potential for obtaining new insights with laser-induced plasma instruments and it could facilitate the development of a low-cost instrument. 展开更多
关键词 激光诱导等离子体 空间分辨 光谱性质 时滞系统 信号分布 技术 击穿 等离子发射
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T形件-钢管螺纹锚固单边螺栓连接受拉性能试验研究
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作者 刘闵 张越 +3 位作者 牛广慧 袁健 王培军 袁昊天 《钢结构(中英文)》 2022年第4期14-24,共11页
钢结构框架柱采用闭口截面具有截面承载效率高、抗扭模量大等优势。利用螺纹锚固单边螺栓可以解决钢梁-钢管柱无法采用普通高强螺栓直接连接的问题。螺纹锚固单边螺栓是通过在柱壁上加工带有螺纹的螺栓孔,直接将高强螺栓拧紧在柱壁的螺... 钢结构框架柱采用闭口截面具有截面承载效率高、抗扭模量大等优势。利用螺纹锚固单边螺栓可以解决钢梁-钢管柱无法采用普通高强螺栓直接连接的问题。螺纹锚固单边螺栓是通过在柱壁上加工带有螺纹的螺栓孔,直接将高强螺栓拧紧在柱壁的螺纹孔上来代替传统螺母,实现在钢管柱外侧安装和拧紧。在螺纹锚固单边螺栓双T形节点模型研究的基础上,进一步研究了螺纹锚固单边螺栓连接T形件-钢管的受力机理和破坏模式。对10个采用螺纹锚固单边螺栓连接T形件-钢管节点进行了受拉试验研究,分析和对比了不同节点破坏模式、承载力机理、位移-荷载曲线、屈服承载力和极限承载力等。试验发现:节点共发生了四种破坏,分别为螺纹剪切破坏、管壁局部屈服伴随螺纹剪切破坏、螺栓杆拉断破坏和管壁屈服破坏。当钢管壁厚度较小时,节点发生螺栓孔内螺纹剪切破坏,当管壁较厚,螺栓直径相对较小时,发生螺栓杆拉断破坏,但螺纹孔内螺纹保持完好,表明当螺栓孔内螺纹长度足够时,钢管壁螺栓孔内螺纹具有足够的承载力,螺纹锚固方式可行。同时对比分析了螺栓间距、螺栓直径及管壁厚度对节点承载力的影响。试验结果表明:增大螺栓直径、管壁厚度、螺栓间距等,均可以提高节点的承载力;螺栓间距对节点承载力的影响与钢管壁在螺栓拉力作用下屈服线的形状有关,当螺栓间距较小时,各受拉螺栓对钢管壁的屈服线相互叠加,随着螺栓间距增大,节点承载力明显提高;但当螺栓间距较大,各受拉螺栓对钢管壁屈服线为长圆形,随螺栓间距的增加,节点承载力将保持不变;随着螺栓直径的增加,节点的破坏模式逐渐从螺杆拉断破坏改变为钢管壁螺栓孔螺纹破坏或钢管壁屈服破坏,节点承载能力增加;管壁厚度增加显著提高钢管壁屈服承载力,其增长率与壁厚的增长率近似呈平方的关系。为了避免钢管壁较薄时,管壁螺栓孔内螺纹锚固力不足的问题,进一步研究了钢管内设垫板对螺纹锚固单边螺栓T形件-钢管连接节点受力性能的影响。试验结果表明:垫板增加了螺纹锚固长度,加强后的节点承载力显著提高,有效地避免螺纹剪切破坏,但初始刚度变化不大。 展开更多
关键词 螺纹锚固单边螺栓 螺栓连接节点 破坏模式 受拉屈服承载力
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