Submarine’s propellers and CAD/CAM in military shipbuilding
Firstly watch a Ohio class submarine in a dock here
Propellers for submarines are made out of beryllium bronze. It has very interesting physical properties like on of the highest melting point, flexural rigidity, thermal and acoustic conductions. Look at the article in Wikipedia about Beryllium to get more information. The point in submarine’s propellers is to manufacture them as thin as possible so that the submarine could produce low noise and as strong as possible so that the submarine can achieve speed. The manufacturing of propeller is quite complex and iterative. Firstly, you have to perform bronze continuous/industrial casting. Then quenching then milling and the last stage: most important: to lay a berillium layer on the bronze and perform milling once again. Over couple of iterations you get a propeller for submarine. That’s interesting, requires big knowledge and engineering experience, isn’t it? If you don’t have advanced milling technology you won’t produce them. You can read here that Back in the mid-1980s, the Japanese company Toshiba sold propeller milling machinery to the Soviets through the Norwegian Kongsberg firm; this and other submarine intelligence furnished by the Walker spy ring resulted in significantly quieter Soviet subs by the later part of the decade. As writer Neal Stevens wrote about the Akula-class Soviet boats, “The combined results generated a steep drop in broadband acoustic noise profiles.” .
The point is not only in materials, but also in milling. There many technologies of tool’s error compansation in 5C milling machines. This the the hot topic for the researchers and is quite complicated. Check CAGD to see some latest achievements in it. Generally you can classify them as geometrical compensation, force compensation and FEM compensation, thermal compensation. The accuracy of parts produced in milling has been studied for over 80 years right now. It’s crucial in high-precision industry. Errors in the ﬁnal dimensions of the machined part are determined by the accuracy with which the commanded tool trajectory is followed, combined with any deﬂections of the tool, part/ﬁxture, or machine caused by the cutting forces. As part accuracy demands have increased, these error sources have received signiﬁcant attention from researchers and machine tool builders alike. Due to these efforts, manufacturers now implement sophisticated error compensation algorithms to reduce the effect of geometric errors in the machine structure. Improved designs combined with software error compensation have reduced the effect of thermal error, although this can still be a major contributor. High performance axis drives coupled with modern control algorithms have improved trajectory following dramatically. Pre- or in-process compensation for milling force errors is less common. [Case study: A comparison of error sources in high-speed milling,Tony L. Schmitz, John C. Ziegert, J. Suzanne Canning, Raul Zapata, ScienceDirect, Elsevier]. Read this publication to get introductory insight into milling compensation methods.
Do you remember the disaster of Russian submarine Kursk? There many submarines going everywhere nowadays and there are many accidents with them. This is unbelievable how active they are how often some accidents happen. Read the following articles and see the dates to get preview on activity of submarines and importance:
- BRITISH and French nuclear submarines which collided deep under the Atlantic
- British and French nuclear submarines crash in Atlantic
- Chineese submarine collides with sonar array towed by U.S. Navy ship
- US navy vessels collide in Gulf
If you are a fan of military famous stories check the following links:
Some finally thoughts. There are many accidents with submarine’s crush. There are crushes between two modern submarines (even from the same country), and on the other hand, we have got quite powerful sonars and radars ( US can spot a submarine from Murmansk, Russia ). That’s a good question – why do the submarines collided? The advancement of technology is unbelievable. There are two cores of this: the knowledge about materials and the production technologies we have today (CAM). CAD/CAM is indispensable in developing new products. Better materials and better machining technologies and chemical technology are crucial not only in producing propellers for modern submarines, but also in aviation, automotive etc.