But still left a visible crack around the perimeter of the rectangle.

但这样还是会在矩形的边上留下一点缝隙。

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Removing visible surface corrosion before pitting begins (such as during a C-check) helps prevent conditions that can lead to crack initiation.

在出现斑点之前去除可见的表面腐蚀(诸如c -检)有助于预防发生裂纹。

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It is proved by the application that as long as the method is rational and the work is studied fully, the goal of prevention of crack visible by naked eyes can be reached.

实践证明，只要施工方法合理，事先进行充分研究工作，完全可以实现不出现肉眼可见裂缝的防裂目标。

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Rachel Lowe, from Network Rail, said a minor defect in the rail was identified in an inspection on 12 November, and again on 21 November, but there was "no visible crack in the rail at all and it was managing within normal standards".

BBC: York railway line gap risked tragedy - RMT

Its chimes were silenced for the next four years, until a way was found to make it peal again in 1863 (by turning it slightly), however, the crack is still visible.

CNN: SHARE THIS

When I next tapped on a blurry concrete-and-brick step in the background of the photo, it suddenly became sharp instead of the cup and a crack in the concrete that hadn't been visible appeared.

WSJ: Lytro Takes Fresh View on Picture Taking