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Howard Price, Technologist - Metallic Materials
Chemistry lesson comes to life
Did you know that the Universal Gas Equation helped our engineers find the best way to produce parts for the Typhoon?
Using a special process called super plastic forming and diffusion bonding, heat and pressure are used to transform a series of metal sheets into complex parts for military aircraft.
You see, the universal gas equation describes the relationships between the pressure, volume and temperature of a gas provided all of the measurements use absolute units.
This allowed us to work out a safe pressure to use in our process and to accurately predict what would happen when the temperature increased. It also allows us to calculate how much argon gas we will use and, indirectly, how much oxygen (a trace impurity in the argon that contaminates titanium). Without having understood how gases behave, we might waste millions of pounds experimenting with the unknown.
From textbook to Typhoon
Did you know that the Stefan-Boltzmann law helped our engineers ensure we got things right first time and at the right temperature?
Another important formula that makes its way from the textbook to Typhoon is the Stefan-Boltzmann law which defines how much heat is given off from a radiating body.
Working in an environment where we are heating metal up to temperatures as high as 950 degrees Celsius (over 1220 Kelvin) means that the Stefan-Boltzmann formula is a hot topic for us. The law states that the total radiant heat emitted from a surface is proportional to the fourth power of its absolute temperature. Just like with any good recipe, you need to cook your ingredients at the right time and at the right temperature.
Tick Tock
Timing is important to achieve the correct aerodynamic shape tolerance.
The nature of radiant heat at these very high temperatures means that metal at 700 degrees Celsius cools at half the rate than it would from 950 degrees.
So, to ensure parts don’t distort once out of the oven, we were able to determine the best removal strategy which involves a short initial pre-cooling inside the oven before final removal. The cooler parts are before final removal, the slower they will then cool and the stronger they will be.
This knowledge was fundamental to achieving the correct aerodynamic shape tolerance for the Typhoon foreplanes.
