月度狗中有关glass的，是这篇吗？请狗主人确认下咯~~

zhu8809

Flawed Beauty:. the problem with toughened glass

On 2nd August 199.9, a particularly hot day in the town of Cirencester in the UK, a large pane of toughened glass in the roof of a shopping centre at Bishops Walk shattered without warning and fell from its frame. When fragments were analysed by experts at the giant glass manufacturer Pilkington, which had made the pane, they found that minute crystals of nickel sulphide trapped inside the glass had almost certainly caused the failure.

'The glass industry is aware of the issue,' says Brian Waldron, chairman of the standards committee at the Glass and Glazing Federation, a British trade association, and standards development officer at Pilkington. But he insists that cases are few and far between. 'It's a very rare phenomenon,' he says.

Others disagree. 'On average I see about one or two buildings a month suffering from nickel sulphide related failures,' says Barrie Josie, a consultant engineer involved in the Bishops Walk investigation. Other experts tell of similar experiences. Tony Wilmott of London-based consulting engineers Sandberg, and Simon Armstrong at CIadTech Associates in Hampshire both say they know of hundreds of cases. 'What you hear is only the tip of the iceberg,' says Trevor Ford, a glass expert at Resolve Engineering in Brisbane, Queensland. He believes the reason is simple: 'No-one wants bad press.'

Toughened glass is found everywhere, from cars and bus shelters to the windows, walls and roofs of thousands of buildings around the world. It's easy to see why. This glass has five times the strength of standard glass, and when it does break it shatters into tiny cubes rather than large, razor-sharp shards. Architects love it because large panels can be bolted together to make transparent walls, and turning it into ceilings and floors is almost as easy.

It is made by heating a sheet of ordinary glass to about 620°C to soften it slightly, allowing its structure to expand, and then cooling it rapidly with jets of cold air. This causes the outer layer of the pane to contract and solidify before the interior. When the interior finally solidifies and shrinks, it exerts a pull on the outer layer that leaves it in permanent compression and produces a tensile force inside the glass. As cracks propagate best in materials under tension, the compressive force on the surface must be overcome before the pane will break, making it more resistant to cracking.

The problem starts when glass contains nickel sulphide impurities. Trace amounts of nickel and sulphur are usually present in the raw materials used to make glass, and nickel can also be introduced by fragments of nickel alloys falling into the molten glass. As the glass is heated, these atoms react to form tiny crystals of nickel sulphide. Just a tenth of a gram of nickel in the furnace can create up to 50,000 crystals.



These crystals can exist in two forms: a dense form called the alpha phase, which is stable at high temperatures, and a less dense form called the beta phase, which is stable at room temperatures. The high temperatures used in the toughening process convert all the crystals to the dense, compact alpha form. But the subsequent cooling is so rapid that the crystals don't have time to change back to the beta phase. This leaves unstable alpha crystals in the glass, primed like a coiled spring, ready to revert to the beta phase without warning.


When this happens, the crystals expand by up to 4%. And if they are within the central, tensile region of the pane, the stresses this unleashes can shatter the whole sheet. The time that elapses before failure occurs is unpredictable. It could happen just months after manufacture, or decades later, although if the glass is heated - by sunlight, for example - the process is speeded up. Ironically, says Graham Dodd, of consulting engineers Arup in London, the oldest pane of toughened glass known to have failed due to nickel sulphide inclusions was in Pilkington's glass research building in Lathom, Lancashire. The pane was 27 years old.


Data showing the scale of the nickel sulphide problem is almost impossible to find. The picture is made more complicated by the fact that these crystals occur in batches. So even if, on average, there is only one inclusion in 7 tonnes of glass, if i you experience one nickel sulphide failure in your building, that probably means you've got a problem in more than one pane. Josie says that in the last decade he has worked on over 15 buildings with the number of failures into double figures.


One of the worst examples of this is Waterfront Place, which was completed in 1990. Over the following decade the 40 storey Brisbane block suffered a rash of failures. Eighty panes of its toughened glass shattered due to inclusions before experts were finally called in. John Barry, an expert in nickel sulphide contamination at the University of Queensland, analysed every glass pane in the building. Using a studio camera, a photographer went up in a cradle to take photos of every pane.
These were scanned under a modified microfiche reader for signs of niclrel sulphide crystals. 'We discovered at least another 120 panes with potentially dangerous inclusions which were then replaced,' says Barry. 'It was a very expensive and time-consuming process that took around six months to complete.' Though the project cost A$1.6 million (nearly £700,000), the alternative - re-cladding the entire building - would have cost ten times as much.

zhu8809

长时长了些  GMAT一般没有这么长的吧~~  呵呵

只是觉着 内容跟狗狗描述的有些像~\(≧▽≦)/~

文章来自于 《剑桥雅思第五册》P89  

主要是讲“钢化玻璃”的~~

toughened glass为钢化玻璃
当钢化玻璃破碎时，它的碎片不像普通玻璃一样。 钢化玻璃有时会突然破碎，“热胀冷缩”，外层比内层先收缩，天暖和的时候才会膨胀。

Brian Waldron在英文原文中一共出现了三次。第一次出现：“‘The glass industry is aware of the issue,’ says Brian Waldron.”意思是：“Brian Waldron说：‘整个玻璃行业已经意识到了这个问题（在没有任何征兆的情况下，一种硫化镍微型晶体可以导致钢化玻璃破碎）。’”第二次出现：“But he insists that cases are few and far between.”意思是：“但他坚持认为这种案例只不过是沧海一粟罢了。”第三次出现：“‘It’s a very rare phenomenon,’ he says.”意思是：“他说：‘这是一个非常罕见的现象。’”

Trevor Ford在原文中一共出现了两次。第一次出现：“‘What you hear is only the tip of the iceberg, ’ says Trevor Ford”意思是：“Trevor Ford说：‘你所听到的只是冰山一角（言外之意，实际上，硫化镍导致钢化玻璃破裂这类问题发生了很多次，但被我们听到的很少）。”第二次出现：“He believes the reason is simple: ‘No-one wants bad press.’”意思是说：“他认为（上述这件事的）原因很简单：‘没有人喜欢坏消息。’”

Graham Dodd在原文中只出现了一次：“Ironically, says Graham Dodd … the oldest pane of toughened glass known to have failed due to nickel sulphide inclusions … was 27 years old.”意思是：“Graham Dodd说，具有讽刺意味的是，由于含有硫化镍而导致破裂的钢化玻璃中，使用时间最长的一块用了27年。”（原文中出现了“最”这样含义，原文中“使用时间最长”和选项中“出事时间最晚”是一个意思。）

　　John Barry在原文中一共出现了三次。第一次出现：“John Barry, an expert in nickel sulphide contamination at the University of Queensland, analysed every glass pane in the building.”意思是：“Queensland大学硫化镍方面的专家 John Barry检查了这栋大楼中的每一块玻璃。”第二次出现：“‘We discovered at least another 120 panes with potentially dangerous inclusions which were then replaced,’ says Barry.”意思是：“Barry说：‘我们发现还有另外的120块玻璃也存在同样的危险，后来将它们换掉了。’”第三次出现：“‘It was a very expensive and time-consuming process that took around six months to complete.’”意思是说：“（替换存在危险的玻璃）是一个昂贵而又费时的过程，它花了大约整整六个月的时间。”

gzpeva

阅读原文比这个枯燥一些，有些术语用到了。这篇较长

zhu8809

呵呵~~  那就当背景材料看好了~~

谢咯