科学家利用声波在桥梁和飞机寻找隐蔽的裂缝

Scientists Use Sound Waves to Find Hidden Cracks in Bridges, Airplanes 科学家利用声波在桥梁和飞机寻找隐蔽的裂缝

On August 1, 2007, a steel bridge in Minneapolis, Minnesota, collapsed², sending people and vehicles into the Mississippi River. Thirteen people died and more than 140 others were injured.

The bridge collapse¹ took place during rush hour -- when a lot of cars and trucks were on the road. Investigators³ found that undersized metal parts of the bridge simply could not support the heavy load.

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.

Anthony Croxford leads the team of scientists at Bristol University. They begin their research by sending hundreds of different ultrasonic⁴ waves into a structure. Then, Mr. Croxford says, they listen and study echoes of the sound waves to identify the smallest cracks.

"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."

Anthony Croxford says this method is unlike a purely⁵ 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.

"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."

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 rivet⁶ openings. Openings that large would create one big echo.

"By using this novel approach we can now pick up a crack close to a hole, which is directly relevant, to say, aerospace⁷ applications, where they're worried about cracks growing from rivet holes, things like that."

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

The technology could help safety inspectors⁸ get more detailed⁹ estimates of damage in materials like aircraft parts and bridge supports. The damaged materials could then be replaced before they fail.

Words in This Story

crack – n. a very small space or opening between two things or two parts of something

rivet – n. a special kind of metal bolt or pin that is used to hold pieces of metal together

rush hour – n. a time during the day early in the morning or late in the afternoon when many people are traveling on roads to get to work or to get home from work

ultrasonic – adj. used to describe sounds that are too high for human beings to hear

1 collapse   

vi.累倒；昏倒；倒塌；塌陷

参考例句：

• The country's economy is on the verge of collapse.国家的经济已到了崩溃的边缘。
• The engineer made a complete diagnosis of the bridge's collapse.工程师对桥的倒塌做了一次彻底的调查分析。

2 collapsed   

adj.倒塌的

参考例句：

• Jack collapsed in agony on the floor. 杰克十分痛苦地瘫倒在地板上。
• The roof collapsed under the weight of snow. 房顶在雪的重压下突然坍塌下来。

3 investigators   

n.调查者，审查者( investigator的名词复数 )

参考例句：

• This memo could be the smoking gun that investigators have been looking for. 这份备忘录可能是调查人员一直在寻找的证据。
• The team consisted of six investigators and two secretaries. 这个团队由六个调查人员和两个秘书组成。 来自《简明英汉词典》

4 ultrasonic   

adj.超声的；n.超声波

参考例句：

• It was very necessary for people to take type-B ultrasonic inspection regularly.定期进行B超检查是十分必要的。
• Sounds are classified into two kinds: sonic and ultrasonic.声波分为两类，即普通声波与超声波。

5 purely   

adv.纯粹地，完全地

参考例句：

• I helped him purely and simply out of friendship.我帮他纯粹是出于友情。
• This disproves the theory that children are purely imitative.这证明认为儿童只会单纯地模仿的理论是站不住脚的。

6 rivet   

n.铆钉；vt.铆接，铆牢；集中(目光或注意力)

参考例句：

• They were taught how to bore rivet holes in the sides of ships.有人教他们如何在船的舷侧钻铆孔。
• The rivet heads are in good condition and without abrasion.铆钉钉头状况良好，并无过度磨损。

7 aerospace   

adj.航空的，宇宙航行的

参考例句：

• The world's entire aerospace industry is feeling the chill winds of recession.全世界的航空航天工业都感受到了经济衰退的寒意。
• Edward Murphy was an aerospace engineer for the US Army.爱德华·墨菲是一名美军的航宇工程师。

8 inspectors   

n.检查员( inspector的名词复数 )；（英国公共汽车或火车上的）查票员；（警察）巡官；检阅官

参考例句：

• They got into the school in the guise of inspectors. 他们假装成视察员进了学校。 来自《简明英汉词典》
• Inspectors checked that there was adequate ventilation. 检查员已检查过，通风良好。 来自《简明英汉词典》

9 detailed   

adj.详细的，详尽的，极注意细节的，完全的

参考例句：

• He had made a detailed study of the terrain.他对地形作了缜密的研究。
• A detailed list of our publications is available on request.我们的出版物有一份详细的目录备索。