【薄板激光焊接过程中焊接缺陷的诊断原理和技术】骆红.pdf

Dissertation Submitted to HluazhongUniversityofScienceandTechnology for theDegree of Doctor of PhilosophyinEngineering ThePrinciplesandTechnologiesof DefectDiagnosis in LaserWelding of Thin Sheets Ph.D.Candidate:Luo Hong Major:Material ProcessingEngineering Supervisor:Prof.HuangShuhuai Ass.

华中理工大学博士学位论文在错边量不大的情况下,光、声信号强度的变化都不是很明显,但对应的频谱分布的变化却比较显著,说明由于熔池和小孔的形状变化,会使等离子体及熔池的振荡状态发生变化,从而导致信号的频谱发生明显改变.在出现烧穿前的一瞬间,等离子体光、声信号的强度有明显的提高,但其频谱反映出信号主要集中在低频区,接着在焊缝中出现孔洞,信号强度急剧降低.由此可以看出,通过检测等离子体光、声信号的平均强度就可以实时监测激光焊接过程的稳定性。要进一步对出现的缺陷进行识别,则必须利用等离子体光、声信号的频谱特征。

华中理工大学博士学位论文 acousticsignalswhenthereappeareddefectsinlaserweldingwerediscussed.When a magnetic restrained discharge laser was used, the plasma has an obvious cycling period(emerging-disappearing-reemerging)with the same frequency the plasma was not stable.