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題名 | 不同斷面沃斯回火球墨鑄鐵之低週疲勞性質=Effect of Cast Section Size on the Low-Cycle Fatigue Strength of Austempered Ductile Irons |
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作者 | 傅春祥; 林志光; | 書刊名 | 鑄工 |
卷期 | 23:4=95 1997.12[民86.12] |
頁次 | 頁21-42 |
分類號 | 472.2 |
關鍵詞 | 沃斯回火球墨鑄鐵; 低週疲勞; 應變控制; 斷面尺寸; Austempered ductile iron; Low-cycle fatigue; Strain control; Section size; |
語文 | 中文(Chinese) |
中文摘要 | 本研究主旨在探討球墨鑄(DI)斷面尺寸及各位置因凝固時間的不同,對沃斯回火球墨鑄鐵 (ADI)在應變控制下低週疲勞行為的影響。實驗材料共分兩批,分別在產生最佳延性、韌性與理想強 度、硬度的熱處理條件下進行疲勞試棒的熱處理。實驗結果顯示,ADI之低週疲勞強度隨鑄件斷面 的尺寸增加而降低,並且在厚斷面鑄件中越遠離砂模面的位置其低週疲勞性質越差。這是因為鑄造 澆鑄時凝固速率的降低,造成球黑數量減少、球黑形態惡劣、缺陷的增加及晶界間產生偏析所造成。 ADI的低週疲勞強度與基地的穩定性及對缺陷的敏成度有關,整體而言,以小斷面並經由理想強度、 硬度熱處理的ADI有較佳的低週疲勞性質。再就ADI的疲勞破裂而言,主裂縫大多起源於表面的 縮孔,然後沿著球墨聚集或晶包間的缺陷處成長,成長的方向與施加外力的方向垂直。 |
英文摘要 | This study investigated the relationship between low-cycle fatigue (LCF) strength of austempered ductile iron (ADI) and cast section size and position. Uniaxial LCF tests were conducted under strain control at several strain amplitudes in tension-compression cyclic loading. Results showed that as the cast section size increased, the fatigue strength decreased. The decrease in LCF strength is attributed to the increase in graphite nodule size and numbers of microshrinkage pores, the deterioration in nodule shape, and possibly the increase in the extent of cell boundary microseregation as the cast secton size is increased. LCF strength of ADIs with optimal strength is primarily affected by the defects while matrix stability is the major factor influencing LCF strength of ADIs with optimal toughness. In general , ADIs cut from the small-section castings and austempered for optimal strength showed the best LCF property. Fatigue cracks usually initiated from the surface irregular nodules and casting defects and propagated toward defects and highly distributed nodules in a direction perpendicular to loading direction. |
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