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目的 研究酸碱度对纯钛铸造卡环疲劳强度的影响.方法 于2010年5月至2010年11月,在哈尔滨工业大学航天材料与力学系研究室将20个铸造的纯钛卡环随机分为4组,分别在空气中和pH值分别为4.0、6.8和8.0的人工唾液中进行加载-形变测试,计算机自动记录初始载荷和疲劳失效时的载荷循环次数.应用扫描电子显微镜观察卡环在加载后的腐蚀形貌和疲劳裂纹.结果 纯钛卡环在不同测试条件下的初始载荷差异无统计学意义(P＞0.05).在pH值分别为4.0、6.8和8.0的人工唾液中的载荷循环次数与空气中的比较均明显减少,差异均有统计学意义(P＜0.01);但pH值为6.8和8.0的人工唾液中的载荷循环次数差异无统计学意义(P＞0.05),这两组与pH值为4.0的人工唾液中的载荷循环次数差异有统计学意义(P＜0.05).结论 纯钛卡环的疲劳强度在不同pH值的人工唾液都受影响而降低,且pH值呈酸性的人工唾液对试件的疲劳强度影响更大.

Effect of different pH on the fatigue strength of pure titanium clasp

Objective To study the effect of different pH on the fatigue strength of pure titanium clasp. Methods Twenty casting clasp specimens made of pure titanium were divided into 4 groups.Specimens were tested in the air and in the artificial saliva of pH equal to 4.0, 6.8 and 8.0, and the load-deformation test was carried on them. Initial loading force and loading cycle while breaking were registered automatically. Corrosion appearance and fracture flaws were examined with SEM. Results The initial loading forces of pure titanium were not different among four test conditions （P 〉 0.05 ）.Compared with in the air, the artificial saliva of different pH reduced the loading cycles and had a significant difference （P 〈 0.01 ）.However, the loading cycles in the artificial saliva of pH equal to between 6.8 and 8 were the same （P 〉 0.05）, while both of them were significantly different with in the artificial saliva of pH equal to 4.0 （P 〈 0.05）. Conclusion The results suggest that all artificial saliva reduce the fatigue strength of pure titanium clasp, and the artificial saliva whose pH is acid affects pure titanium clasp more significantly.