On August 1, 2007, a steel bridge in Minneapolis, Minnesota, collapsed, sending people and vehicles into the Mississippi River. Thirteen people died and more than 140 others were injured.
2007年8月1日，明尼苏达州明尼阿波利斯市的一座钢桥坍塌，使桥上的人和车辆坠入了密西西比河。事故造成13人遇难，还有140多人受伤。
The bridge collapse took place during rush hour -- when a lot of cars and trucks were on the road. Investigators found that undersized metal parts of the bridge simply could not support the heavy load.
这座桥在交通高峰期坍塌，当时有很多轿车和卡车在桥面上。调查人员发现，这座桥上金属部件尺寸过小无法支撑这一沉重负荷。
Finding hidden cracks and other weak areas in large structures can be the difference between life and death. Researchers in Britain say they have discovered a new way to identify cracks inside metal parts before they fail. Their method involves using sound imaging.
发现大型建筑物上的裂纹和薄弱环节可能生死攸关。英国研究人员表示，他们发现了一种新方法可以在金属部件失效前探测到它们内部的裂纹。他们的方法包括使用声成像技术。
Anthony Croxford leads the team of scientists at Bristol University. They begin their research by sending hundreds of different ultrasonic waves into a structure. Then, Mr. Croxford says, they listen and study echoes of the sound waves to identify the smallest cracks.
安东尼·克劳斯福德(Anthony Croxford)负责布里斯托大学的一个科学家团队。他们通过向建筑物内部发出数百种不同的超声波开始了他们的研究。克劳斯福德随后表示，他们监听并分析了这些声波的回声来探测最细微的裂纹。
"It lets you see smaller cracks, closed cracks, so when I say closed cracks, you can magine 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."
“它能让你发现很小的、闭合的裂纹。说到闭合的裂纹，你可以想象一块金属有裂纹，它可能是像这样裂开一点点，中间有间隙。如果有空隙，我们就能监听到间隙边缘反射过来的回声，但是我们无法知道间隙大小。”
Anthony Croxford says this method is unlike a purely linear system. A linear system creates echoes, or similar versions, of the sound wave sent into the material. In other words, you would hear the same frequency coming back from the object. Mr. Croxford says his ‘phased array' system of sending out sound waves returns harmonics -- echoes of different frequencies.
克劳斯福德表示，这跟纯线性系统不同。纯线性系统产生的回声跟向材料发出的声波是同一种形式。换句话说，你听到物体反射回来的声音是同一种频率。克劳斯福德先生表示，他的“相位排列”设备发出声波后返回的是谐波，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."
“这种非线性方法意味着我们可以确实听到一些声音，听到不同的效果的声音，而不是只听到裂纹反射的回声。”
Mr. Croxford tested the system on part of a wing from a passenger airplane, an Airbus A320 aircraft. A linear system would not be able to identify cracks forming around the rivet openings. Openings that large would create one big echo.
克劳斯福德利用一架空客A320客机的机翼部分测试了这套系统。线性系统不能发现铆钉孔周围形成的裂纹。大的铆钉孔会产生很强的回声。
"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."
“通过使用这种新方法，我们可以找到铆钉孔周围的裂纹，它和航空应用直接关联，人们担心铆钉孔会产生裂纹之类的。”
He says the phased array system uses only one piece of equipment to get both a linear and nonlinear image.
他说，相位排列系统仅使用一台设备就能同时获得线性和非线性图像。
The technology could help safety inspectors get more detailed estimates of damage in materials like aircraft parts and bridge supports. The damaged materials could then be replaced before they fail.
这种技术可以帮助安全检查人员更加精确地评估飞机零件和桥梁支撑物等材料的损伤。然后在失效前更换掉这种损伤材料。