（ZT）F-35：發動機葉片 bummer（圖）

  

噴氣機發動機葉片是在高溫和高壓的環境下工作的部件，因此不是一般的工程材料知識可以想當然滴，而且還有高速，還是旋轉的高速，因此噴氣機發動機葉片不僅經受壓力還要經受拉力，特別是還有震動，而且還都是周期性的。

其實這些都還不是問題，問題是為了盡量提高發動機的功能，還要盡可能的減小噴氣機發動機葉片的重量，因此葉片就做的盡可能的薄，有的部位甚至是空心的，減輕重量也便於降溫。

但是，機械畢竟是死的，因此一般機械設計的最佳運作條件或狀態不是它的最大指標的狀態，因為這時所有零部件都要承受最高的考驗，也不是它的比較低的指標的狀態，比如說汽車發動機，速度低就有燃燒不夠幹淨的問題，比較中速是比較理想最佳運作條件的狀態，其實人體也差不多，慢走有時更累人。

所以，大家可以想象，如果你推一下極限，設計指標還是可以提高滴，但是可靠性和壽命就會降低，也許F-35的發動機沒推極限，但是也可能是F-35的性能要求F-35的發動機經常作長時間和高強度的運行，F-35的“發動機葉片 bummer”的外號就出來。

“bummer”不好翻譯，我搜了一下，“bummer”的意思差不多就是“糟糕”、“壞消息”、“無賴”、“懶漢”等等。

不知道是F-35因為發動機的葉片不好而不好的，還是發動機的葉片因為F-35不好而不好的，唉，大家自己看吧

請看：

F-35：發動機葉片 bummer（圖）

這是2007年測試F-35發動機的葉片斷裂照片

  

F-35: Blade Bummer

The news that the Pentagon’s fleet of 51 F-35 fighters has been grounded because of a half-inch crack in one of its engine’s turbine blade is one of those problems that can truly be called a teething issue: it’s something that happens on most every high-tech jet engine that is pushing the engineering envelope.

Pentagon officials over the weekend suggested waiting for Pratt & Whitney, the maker of the F-135 powerplant that powers the F-35, could take a week to 10 days.

Sometimes such problems are natural; sometimes not.

All involved want to make sure that whatever caused the crack is unique to that particular blade and not a threat to all F-35 engines. A single-engine warplane like the F-35 could be doomed by a disintegrating turbine blade.

This isn’t a new problem with the F-35 powerplant; a similar blade cracked during testing in 2007. “Most likely root cause is resonant response to aerodynamic excitation by the upstream 54 vanes in STOVL operation,” an investigation into that earlier failure concluded. “No indication that defects in material properties or single crystal orientation significantly contributed to the failures.”

News of the grounding comes at a sensitive time, as F-35 advocates try to convince the Australian government this week to stick to its original plan to buy 100 of the jets. The grounding is only the latest in a series of problems for the program, which has been plagued by delays and cost overruns.

The U.S. military plans on spending $396 billion for 2,457 of the planes, making it the most costly weapons system in the history of the world (the planes, built by Lockheed Martin, are slated to cost $332 billion; Pratt’s price for the engines is projected to be $64 billion). But the program’s problems, and looming defense-spending cuts, are likely to cut the program, perhaps by as much as half, defense officials say privately.

The grounding affects the F-35s being built for the Air Force, the Marines and the Navy because all three variants use the same engine (“Putting all your engines in one basket,” one defense official says). There had been a plan to develop competing engines for the F-35 – as there were for the older F-15s and F-16s the F-35 is slated to replace – but the Pentagon and Congress agreed two years ago to scrap an alternative engine, saying it wouldn’t be worth the added investment.