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The Problem – Stress Measurements on Ship Hull Building a ship is a very long and expensive process. You can’t wait until the ship is built and at sea to find out if the hull is strong enough or streamlined enough to perform as expected. Finding the best design for speed and strength cannot be a trial and error process. How can the design be tested and optimized?
The Solution Ship designers use models and a long towing tank to simulate the final design. A model of the ship hull is instrumented and then towed through water at simulated speeds and sea conditions. By measuring the stress levels in the model, changes in the design can be made at a very early level, before the expensive process of building the full-size ship. To determine stress levels in a ship model, strain gages are affixed to the key structural elements. Strain gages sense the force applied and produce a very small change in resistance. Strain gages require signal conditioning: they must be given excitation current, be wired as a Whetstone bridge (using completion resistors), and the small changes in signal due to stress amplified for data logging as the ship model is towed through the water. Because the tow tanks are often several hundred yards long, a self-contained signal conditioning and data acquisition system is used.
Validyne Products The Validyne MC170L provides all the requirements for a self-contained system. The compact MC170L module case accepts up to 16 SG297A strain gage amplifiers. The SG297A provides precision +5 Vdc excitation, provision for completion resistances and high gain amplification for strain gage measurement. The MC170L connects to the 16-channel, 16-bit PCM862 A/D card for a laptop PC. Data acquisition software is provided so that the data can be collected from several channels at rates up to 50 Hz. The laptop can be connected via Ethernet cable and the data acquisition software operated remotely using PC Anywhere. In this way the rugged, compact MC170L and the laptop can be mounted on the towing bridge as it moves along the several hundred-yard tank. The data can then be retrieved over the network using standard file transfer commands from a stationary control station.
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| Phone: 818.886.2057 || Email: Sales@validyne.com |
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