OBJECTIVES The present investigation evaluated the step stress accelerated test (SSALT) load profiles on the survival probability of a glass ceramic under two surface conditions (polished or roughened). METHODS Suprinity-ZLS blocks (Vita Zhanfabrik) were shaped into cylinders, cut in a sawing machine, and crystalized according to the manufacturer's instructions. 60 discs were obtained (Ø=12mm, thickness=1.2mm) and randomly assigned into two surface conditions: "p" polished surface (400-1200-grit SiC papers), and "r" roughened surface (200-grit SiC papers). Profilometry was performed in all discs to evaluate average surface roughness prior to flexural fatigue strength testing. 3 discs of each group were submitted to biaxial flexural strength in an universal testing machine (0.5mm/min) and the mean load to failure (N) was calculated to determine SSALT profiles. 27 specimens per surface condition were assigned into three profiles - Mild (n=9), Moderate (n=9), and Aggressive (n=9), and submitted to the fatigue test (60-320N, 140,000 cycles at 1.4Hz). The results were analyzed using the Kaplan-Meier and Wilcoxon tests (5%), 2-way ANOVA and Tukey test (α=5%). RESULTS Kaplan-Meier and generalized Wilcoxon showed (P=0.002) that polished groups showed higher survival probability than roughened condition (P<0.05). A rough internal surface impacted deleteriously on the fatigue strength and reliability of ZLS ceramic. Both surface conditions were more sensitive to the aggressive profile than the other profiles, even worst for the roughened group. Regardless the load profile, 0% survival probability was observed at 384MPa for polished condition. While for roughened, aggressive tested specimens did not survived 147MPa followed by moderate at 312MPa and mild at 384MPa. The failure modes showed fracture marks originating from superficial grooves for both surface conditions. SIGNIFICANCE Polished specimens are sensitive to the load profile variation, confirming the effect of surface morphology on the fatigue results.

中文翻译：

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氧化锆增强硅酸锂陶瓷的存活概率：表面条件和疲劳试验载荷曲线的影响。

目的本研究评估了在两个表面条件（抛光或粗糙）下玻璃陶瓷的存活概率的阶梯应力加速试验（SSALT）负载曲线。方法将Suprinity-ZLS块（Vita Zhanfabrik）成型为圆柱体，在锯床中切割，然后根据制造商的说明进行结晶。获得了60个圆盘（Ø= 12mm，厚度= 1.2mm），并随机分为两个表面条件：“ p”抛光表面（400-1200粒度的SiC纸）和“ r”粗糙表面（200粒度的SiC纸） 。在所有圆盘上进行轮廓测量，以评估弯曲疲劳强度测试之前的平均表面粗糙度。每组3个圆盘在万能试验机中进行双轴弯曲强度测试（0。5mm / min）和平均破坏载荷（N）计算以确定SSALT曲线。每个表面条件下的27个试样被分为三个轮廓-轻度（n = 9），中度（n = 9）和激进（n = 9），并进行了疲劳测试（60-320N，在1.4Hz下进行140,000次循环） 。使用Kaplan-Meier和Wilcoxon检验（5％），2通ANOVA和Tukey检验（α= 5％）分析结果。结果Kaplan-Meier和广义Wilcoxon表明（P = 0.002），与粗糙条件相比，抛光组的生存率更高（P <0.05）。粗糙的内表面会对ZLS陶瓷的疲劳强度和可靠性产生不利影响。与其他轮廓相比，两种表面条件对侵蚀性轮廓都更敏感，对于粗糙的组甚至更差。不管负载情况如何 在抛光条件下，在384MPa下观察到0％的存活概率。对于粗糙化，侵蚀性测试样品不能幸存147MPa，其次是312MPa的中等和384MPa的中等。在两种表面条件下，破坏模式均显示出源自表面沟槽的断裂痕迹。重要性抛光的试样对载荷分布变化敏感，证实了表面形态对疲劳结果的影响。