Estimation Scheme of Residual Lives for elevated Temperature Components Using Total Information of Nano and Macro Sizes

为了评估构件在高温下的蠕变寿命，研制了一种直接对非常小的盘状试件施加恒定载荷的试验装置：小冲头蠕变试验装置。由于结构构件的失效主要发生在最大损伤部位，而严重损伤的构件在结构系统的剩余寿命中占主导地位，因此需要一种评估蠕变温度下构件局部损伤和剩余寿命的方法。然而，常规的单轴蠕变试件需要一定的体积，这往往造成在对单轴蠕变试件取样后对特定装置进行维修的困难。这里使用的圆盘型样品的尺寸非常小：直径10 mm，厚度0.5 mm。在设计和安装了新的SPC测试仪后，使用超硬铝进行了一系列的SPC测试。结果表明，蠕变变形主要以一次蠕变和二次蠕变为主，三次蠕变发生在断裂前。此外，SPC试验获得的蠕变断裂寿命与单轴蠕变试验得到的蠕变断裂寿命有很好的相关性。由于最初的SPC装置没有专门的容器来防止铁素体钢在蠕变温度范围内被氧化，因此在第二财年开发了一种新的SPC试验装置，其中安装了一个薄壁管道和一个小容器，以进行很少的氧化气氛。不幸的是，由于缺乏或不充分的Ar气体流动，在圆盘样品的表面形成了约20μm厚的氧化膜。然而，SPC试验中的载荷与蠕变试验中的应力之间的关系被描述为幂低函数。

A new testing apparatus where constant load is directly applied to a very small disc-type specimen is developed to evaluate creep lives of components at elevated temperatures : Small Punch Creep (SPC) testing apparatus. Since failure of structural components mainly breaks out around maximum damaged portion, and heavily damaged components dominate the residual life of structural systems, a methodology to assess the local damage and residual life in components under creep temperature have been required. However, conventional uni-axial creep specimens need a certain amount of volume, and this often causes a difficulty to repair specific devices after sampling uni-axial creep specimens. Dimensions of the disc-type specimen here employed are very small : 10 mm in diameter and 0.5 mm in thickness. After designing and installing the new SPC testing apparatus, as series of SPC tests are conducted using super duralumin. It is clarified that the primary and the secondary creep regimes occupy most of the creep deformation, and that the tertiary creep appears just before fracture. Furthermore it is shown that creep rupture lives obtained in the SPC test have a good correlation with those from uni-axial creep tests.Since the initial SPC apparatus has not had a specific vessel to prevent oxidation for ferritic steels over the creep temperature regimes, in the second fiscal year a new SPC testing apparatus was developed where a thin walled pipe and a small vessel were attached to perform little oxidation atmosphere. Unfortunately oxide scale about 20μm in thickness was formed on the surface of disc specimens due to either a lack of the flow of Argon gas or inadequate. However a relation between the load in the SPC test and the stress in the creep test is described as a power low function.