(燕山大學(xué) 機(jī)械工程學(xué)院 結(jié)構(gòu)損傷與修復(fù)研究所，秦皇島066004)
摘 要: 利用自行研制的ZL?2型超強(qiáng)脈沖電流發(fā)生裝置對帶有單邊裂紋的Al-Mg合金試件進(jìn)行電磁熱止裂實(shí) 驗(yàn)，并對放電前后裂紋尖端的微觀組織進(jìn)行對比分析；采用熱?電?結(jié)構(gòu)耦合的數(shù)值分析方法求得放電后試件的電流密度場、溫度場及熱應(yīng)力場；從理論上計(jì)算放電后的電熱應(yīng)力強(qiáng)度因子。結(jié)果表明：放電電壓對止裂效果存在最優(yōu)值；在適當(dāng)?shù)膹?qiáng)脈沖電流作用下，裂紋尖端在小范圍內(nèi)被瞬間強(qiáng)化加熱，隨后在極大的熱壓應(yīng)力作用下快速冷卻，組織發(fā)生明顯變化，晶粒得到細(xì)化，并圍繞裂紋尖端形成等值壓縮熱應(yīng)力，對裂紋尖端有“夾緊”作用，進(jìn)而阻止裂紋擴(kuò)展。
關(guān)鍵字: Al-Mg合金；單邊裂紋；微觀組織；止裂；電磁熱效應(yīng)
（Institute of Structure Damage and Restore, School of Mechanical Engineering,
Yanshan University, Qinhuangdao 066004, China）
Abstract:Al-Mg alloys specimens with unilateral crack were used to perform electromagnetic heating crack arrest experiment using a self-made ZL?2 super pulse current generation equipment, and the microstructures around the crack tip were analyzed before and after discharge. The current density field, temperature field and thermal stress field were obtained at the moment of the pulse current discharge by the thermal?electrical?structure coupling numerical analysis method. The electrothermal stress intensity factors were theoretically calculated. The results show that there exists an optimal discharge voltage value for the effect of the crack arrest. Under the action of appropriate super pulse current, the crack tip around small-scale is instantly strengthen-heated, followed by rapid cooling under a great thermal compressive stress. The microstructure has an obvious change, and the grains are refined. And the equivalent heat compression stress generates around the crack tip, which has “clamping” role to the crack tip, and then prevents the crack expansion.
Key words: Al-Mg alloy; unilateral crack; microstructure; crack arrest; electromagnetic heating effect
