【摘要】 用激光显示焊接气流是近几年发展起来的一种新的显示方法。由于其图象条纹的复杂性,有必要对其成象原理进行研究。本文对折射率在成象中的作用进行了试验研究。研究指出,这一显示方法对折射率突变区敏感,能清晰地显示气流界面,从而构成气流形态,判明流场性质。文中研究了气流衍射条纹的分布特征。结果表明,在气流界面上折射率较大的一侧出现亮条纹;折射率较小的一侧出现暗条纹,因而有可能判断哪一侧是什么气体。从这些原理出发,对自由喷流、冲击流和电弧冲击流的图象特征进行了分析判读。在研究拍摄距离对成象影响的基础上,提出了最佳拍摄距离一般可选1.5～2m。更多还原

【Abstract】 Displaying welding gas flow by laser is a new method developed in recent years.Study on the principle of image formation is necessary because of the complexity of the image fringes.In this paper the effect of the refractive index on image formation has been studied with experimental method,and shown that this display method issensitive in the abrupt region of the refractive index.Interface of the gas flow is clearlydisplayed,thus a gas flow pattern is formed,and the flow field behavior can be de-termined.The characteristics of the distribution of gas flow diffractive fringes havealso been studied.Bright fringe appears on the side of the larger refractive index ofthe gas flow interface,while dark one appears on the side of smaller refractive index.Hence it is possible to determine the gas on either side.Guided by these principles,analysis and determination have been made of the image characteristics of free jetflow,impact flow and electric arc impact flow.On the basis of the study of theeffect of the phototaking distance on image formation,the optimum phototaking distance of 1.5—2 m is recommended.更多还原