Solving stress problems in metal constructions

In most cases too highly loaded members as being part of a construction are made thicker to overcome too high stresses. Also if the parts of this construction are welded togehter welds are also made thicker. Practical Solution chooses another approach. By reducing the thickness of a steel plate a stress redistribution can take place lowering the unfavourable peak stresses. With this trick it was possible to lower peak stresses by 40%. This can be seen in the pdf. Read more on the page workexperiance / killn construction.

By adding small machining to a steel product stresses and or tensions in materials or constructions can be diverted. With this you strengthen your design and can direct peak tensions and spread them over a wider area or send them where the construction can take these tensions. With a good design maximum stresses can be reduced in a large amount. Soem examples can be seen underneath.

  1. One way to lower peak stresses for on decks of ships welded rear towing eyes is drilling a hole in the right location of the eye. Critical stresses in the welds lower. Changing the design of the eye is a more expensive option to overcome high stresses in the welds
  2. By machining a groove in a rotor axis and by using bigger rounding off in corners of a rotor axis its fatigue load could be lowered for quite an amount. A rotoraxis has a big span between the bearings, is heavy and can rotate at 25 RPM. Fatigue can then be a problem. More you can read here.
  3. By finding a new concept for connecting blastwalls to the decks of a ship or oil platform Practical Solution was able to reduce the stresses in the critical welds by 80%. The showed existing solutions like “curve limitor” and “insert plate”  were much more expensive. By optimising the leg thickness of the diagonal deformations could be send to places were these defomations could be taken. Strain reduction in the welds were found with a finite element method using von mises tensions. You can see this picture here.

Stress concentrations in jack ups: By leaving some more movements to the legs of the jack ups stress concentrations near the connection between leg and movable deck can be reduced. You just give the leg some more movement possibility towarss the stiff horizontal deck. Off course a good and strong connection is needed otherwise the jack up would collapse in heavy seas. An inflatable bag can make this possible. Duringlifting of the jack up less air is in th einflatable bag giving the leg more freedom towards the deck. This lowers the tensions during lifting of the jack. When the jack is in position air can be added to the bag and a strongerconnection arises.

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