We have tried to compile many of the common materials used in steel stack construction, but it's difficult to have them all. In Steel stack design we have a unique problem, we don't just need the material properties at ambient temperatures, we need the properties at Elevated temperatures as well. As the temperature increases, the yield stress, modulus of elasticity and the ultimate tensile stress decrease. Even the Coefficient of Thermal Expansion changes with temperature. All of these are a consideration for Stack design because we usually have temperatures above grade.
Pressure vessels have a similar problem, and so we have relied heavily upon the material data provided in ASME Sec II, which is used for pressure vessels. They have a very extensive table of material properties at elevated temperatures. Many non-vessel materials are not in this database, and that's where we have problems. You can usually find the ambient properties, but finding sufficient data for elevated is a problem.
There are a couple of options when you need material that is not in the database:
1) Manually enter the properties, this is the simplest solution
On the material screen you don't have to use the lookup option, you can simply click the override checkbox and then manually specify the properties. You may not know what these properties are, and that's where you have to apply Engineering judgement.
2) Add it to a custom database if you plan on using the material repeatedely
If you plan on using the material more than once, it may be worthwhile to spend a little extra time and add it to your Material Database. Follow these steps:
a) Click Geometry/Material/Database:
b) This brings up the Material Database screen. Now click the button "Add New Material".
c) Now enter the specification for the new material:
Now you select the basis, and there are 3 options:
1) Manual - Here just just manually enter all of the properties. Please note that the boxes below that are Green can be edited. You modify all of these boxes to match your material. Down at the bottom is a table with material properties for a temperature. MecaStack allows you to specify a temperature for the material, and so you must at a minimum enter two entries for temperature such that the lower and upper temperatures entered cover the temperatures which you are going to be specifying. For example, if your design temperature is 350 °F, then it stands to reason that you will need to enter a temperature at ambient and then also at 350 °F or greater. If you don't, the software doesn't know what properties to use.
2) Copy Existing Material - The easiest option is to use the "Copy and Existing Material" option. This will allow you to select a "Similar Material" and then use that material properties.
The table will then be populated with all of the properties from the material that you chose to copy. The green fields can then be modified to be whatever is necessary for your New Material.
3) Meca Custom Addition - This is a combination of the other two options. It is difficult to find material properties at elevated temperatures. Properties at ambient are available frequently, but trying to find the reduced strength at higher temperatures is sometimes impossible. When selecting this option the screen looks like this:
Enter your material, and then specify the Minimum and Maximum temperatures for the material as well as the increment that you want properties. For example if you entered a 20 °C increment, then properties are calculated every 20 °C.
Now you have some choices to make on how the Yield, Tensile and Modulus of elasticity are going to be determined. You have 2 options on each of these:
Euro - The Eurocode EN 1993-1-2 Table 3 ahs values to factor the elevated temperature based upon the ambient properties.
Similar Material - If you select this option, then you also select a "Similar" Material. It will then use this "Similar" property to project the property at a given temperature assuming that it follows the same rate of decline as the "Similar" material. For example, if your similar material decreases 10% in yield strength for a temperature increase from 100 to 200 °F, ten using the ambient properties you specified the same rate of decline would be assumed for the new material.
4) Have Meca Add it to the Master Database
This option is only available if you can supply us with sufficient documentation to provide the properties we need at elevated temperatures. Most likely if this data was readily available then we would have already added it.