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

尽管腐蚀板在断裂过程中由于塑性变形局部化而使其吸收的断裂能大大减少，但实验和数值研究尚未详细阐明其行为。在本研究中，实验调查是通过复制钢板具有类似的表面，由于实际腐蚀，其中的表面几何形状是由CAD系统和钢板加工的CAM系统，以模拟腐蚀的表面生成的。这种方法是可能的，因为极限强度和伸长率的降低主要是由起伏表面几何形状的影响引起的，而不是因为腐蚀的化学过程。完成了腐蚀板的CAD/CAM系统后，可以很有效地进行腐蚀板的模拟断裂试验，而不需要腐蚀过程来制备试件。1.孔蚀相似性试验，2.孔蚀图形影响试验，3.对一般腐蚀试板的试样尺寸效应进行了试验研究，主要结论如下：1.对于点蚀和一般腐蚀的板，变形能力显著降低。2.对于相同几何形状的不同尺寸试样，结果表明，在一定的试样尺寸范围内，存在相似律; 3.与密集凹坑试样相比，孤立凹坑试样的延伸率显著降低; 4.在试样尺寸效应方面，试样尺寸越小，其极限强度和延伸率越高。这一明显的趋势表明，需要进一步的研究，以找出适当的测试程序，以估计实际船舶的腐蚀板的力学性能。

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.