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

虽然受腐蚀的板在断裂过程中由于塑性变形的局部化而吸收的断裂能会大大降低，但实验和数值研究尚未详细阐明其行为。在本研究中，通过复制具有与实际腐蚀相似的表面的钢板进行了实验研究，其中表面几何由CAD系统生成，钢板由CAM系统加工以模拟腐蚀表面。这种方法是可能的，因为极限强度和延伸率的降低主要是由起伏的表面几何形状的影响造成的，而不是因为腐蚀的化学过程。在完成了CAD/CAM系统后，可以非常高效地进行腐蚀板材的模拟断裂试验，而不需要腐蚀过程来制备试件。对腐蚀板材的极限强度和变形能力进行了三种系列试验：1.点蚀相似试验；2.检验点蚀图形的影响；3.检验一般腐蚀试板的试件尺寸效应。主要结论如下：1.具有孔蚀和一般腐蚀的板材的变形能力显著降低。2.相同几何尺寸的不同尺寸试件的变形能力几乎相同，因此在一定的试件尺寸范围内存在相似规律。3.与密集存在的凹坑相比，孤立的凹坑具有显著的延伸率降低。4.考虑试件的尺寸效应，较小的试件具有更高的极限强度和延伸率。这一明显的趋势可能表明需要进一步的研究，以找出适当的测试程序，以便评估实际船舶的腐蚀板材的力学性能。

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.