On the stress, strength, and deformability of corroded steel plates

由于腐蚀板在断裂过程中塑性变形的局部化，腐蚀板吸收的断裂能可能大大降低，但实验和数值研究尚未详细阐明这一行为。在目前的研究中，通过复制具有与实际腐蚀相似表面的钢板来进行实验研究，其中表面几何形状由CAD系统生成，钢板由CAM系统加工以模拟腐蚀表面。这种方法是可行的，因为极限强度和伸长率的降低主要是由波动表面几何形状的影响引起的，而不是由于腐蚀的化学过程。完成CAD/CAM系统后，可以非常高效地进行腐蚀板的模拟断裂试验，而无需进行腐蚀过程来制备试样。对腐蚀板的极限强度和变形能力进行了三种系列试验；2.点蚀相似度试验。2 .检查点蚀模式影响的试验；检验具有一般腐蚀的试验板的样品大小效应的试验。主要结论如下：1。对于有点蚀和一般腐蚀的板，变形能力显著降低。相同几何形状的不同尺寸试样的试验结果几乎相同，说明在试样尺寸一定范围内存在相似规律。与密集存在的凹坑相比，孤立的凹坑显示出相当大的伸长率降低。试件的尺寸效应表明，试件的极限强度和伸长率越小。这种明显的趋势表明，需要进一步研究找出适当的试验程序，以便估计实际船舶腐蚀板的机械性能。

Although the fracture energy absorbed by a corroded plate may be considerably reduced due to its localization of plastic deformation during the fracture process, experimental and numerical investigations have not clarified the behavior in details yet. In the present study, experimental investigations are made by reproducing steel plates having surfaces similar to those due to actual corrosion, where the surface geometries are generated by a CAD system and steel plates are machined by a CAM system to simulate corroded surfaces. This approach is possible because the reductions of ultimate strength and elongation are mainly caused by the effects of the undulated surface geometry, and not because of the chemical process of corrosion. Having completed the CAD/CAM system, simulated fracture tests of corroded plates can be carried out very efficiently without the corrosion process to prepare the test specimens.Three kinds of series tests have been carried out with regard to the ultimate strength and the deformability of corroded plates ;1.tests of similarity for pitting corrosion,2.tests to examine the effects of pitting patterns,3.tests to examine the sample-size effects of test plates with general corrosion.The main conclusions are as follows ;1.Considerable reduction of deformability is observed for plates with pitting and general corrosion.2.Different size coupons with the same geometries give almost the same results so that similarity law exists for a certain range of the size of test specimens.3.Isolatedpits show considerable reduction of elongation in comparison with those due to densely existing pits.4.With regard to the size effect of test specimen, smaller coupons exhibit higher ultimate strength and elongation. This clear tendency may suggest the needs of further research to find out the proper test procedure in order to estimate the mechanical properties of corroded plates of an actual ship.