利用声音图像发现设施上裂纹（在线收听）

利用声音图像发现设施上裂纹

Finding hidden cracks in large structures, such as bridges and airplanes, can be the difference between life and death, if the flaw leads to a catastrophic collapse. Scientists at Bristol University in Britain say they have discovered a new way of looking inside crucial metal parts to identify cracks before they fail, using sound imaging.

On August 1, 2007, an eight-lane steel bridge over the Mississippi River in Minneapolis, Minnesota, collapsed during rush hour, killing 13 people and injuring 145.

2007年8月1日，明尼苏达州明尼阿波利斯市密西西比河上一座八车道钢桥在交通高峰时倒塌，导致13人丧生，145人受伤。

An investigation concluded that the main cause of the collapse were undersized elements of the bridge that simply gave way under the heavy load.

调查结果表明，倒塌的主要原因是大桥上的小部件在重载下坍塌。

Metal fatigue like that starts with microscopic cracks that form at points of concentrated stress.

像这样的金属疲劳是从集中应力点的微小裂口开始的。

A group of scientists at Bristol University, led by senior lecturer Anthony Croxford, discovered that sending hundreds of different ultrasonic waves into a structure, and then listening and analyzing their echoes can be used to detect the tiniest cracks.

布里斯托大学一群科学家在安东尼·柯瑞福的率领下发现，向一个结果发送数百个不同的超声波，然后聆听并分析其回声，就能诊断出最微小的裂纹。

“It lets you see smaller cracks, closed cracks, cracks that, so when I say closed cracks, imagine if you have a crack in a piece of metal, it could be a bit open like that, it could have a gap in between it. If you have a gap in between it, you get reflections off the edge of it, but you don't really know how big it is," said Croxford.

“这样就能看到很小的裂纹和闭合裂纹，我说到闭合裂纹，想象下一段金属上有个裂纹，其小裂口像这样，其中有空隙。如果之间有空袭，那么在边缘上就会有回音，但并不知道这个空隙究竟有多大。”

Croxford says unlike purely linear systems, which create echoes of the same frequency sent into the material, his ‘phased array’ of sound-sending units returns harmonics - echoes of different frequencies.

柯瑞福说，与向材料发送同样频率回声的纯粹线性系统不同，他的声音发送器“相控阵”能发回谐频，也就是不同频率的回声。

“The nonlinear approach means that you can actually hear something from them, you're listening to different effects, rather than listening for just that echo from the crack," he said.

“非线性方法意味着你能听到一些回声，能听到不同的效果，而不是只听到从裂纹发出的回声。”

Using an array of attached sensors, Croxford is testing a seemingly perfect part of a wing from an Airbus A320. A linear system would not be able to discover cracks forming around the rivet holes, because a hole would create one big echo.

使用一组连接起来的感应器，柯瑞福对一架空客A320机翼上一段看似完美无瑕的地方进行测试，线性系统不能发现铆钉孔周围的裂纹，因为这种孔能制造出巨大的回音。

“By using this novel approach we can now pick up a crack close to a hole, which is directly relevant, to say, aerospace applications, where they're worried about cracks growing from rivet holes, things like that," said Croxford.

“使用新的方法，我们现在就能找到孔周围的裂纹，这与航空上的应用直接有关，比如人们担心铆钉孔周围有裂纹时，如此等等。”

Croxford says the phased array system uses only one piece of equipment to get both a nonlinear and linear image.

柯瑞福说这种相控阵系统只是用一种设备就能同时得到非线性和线性图像。

The technology could allow inspectors to get more accurate assessments of damage in materials such as crucial aircraft parts, so they can be replaced before they fail.

这种技术能让检查员对飞机上关键部位等材料上的破损做出更精确的评估，这样就能在出问题之前进行替换