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

尽管由于断裂过程中塑性变形的局部化，腐蚀板吸收的断裂能可能会大大降低，但实验和数值研究尚未详细阐明该行为。在本研究中，实验研究是通过复制具有与实际腐蚀相似的表面的钢板来进行的，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状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，无需腐蚀过程来制备试件。对腐蚀板的极限强度和变形能力进行了三种系列试验：1.点蚀相似性试验，2.检验点蚀图案影响的试验，3.检验一般腐蚀试验板样品尺寸效应的试验。主要结论如下： ;1.对于有点蚀和全面腐蚀的板材，变形能力显着降低。2.具有相同几何形状的不同尺寸的试样得到几乎相同的结果，因此对于一定尺寸范围的试样，存在相似规律。3.与密集存在的凹坑相比，孤立的凹坑的伸长率显着降低。4.从试样的尺寸效应来看，较小的试样表现出较高的极限强度和伸长率。这种明显的趋势可能表明需要进一步研究以找出适当的测试程序，以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.