Creo Simulate > Modeling Structure and Thermal Problems > Structure Loads > Load Basics
Load Basics
Although each load type requires a slightly different definition method, there are several factors that govern all loads. As you prepare to add loads to your model, bear the following points in mind:
When you apply loads, Creo Simulate associates the loads with part geometry. In the case of compressed geometry, Creo Simulate can automatically transfer some loads from an original surface to a compressed edge. However, it is preferable to assign loads directly to curves if you know that you will compress the geometry.
Creo Simulate supports a variety of loads. In terms of how you apply these loads to your model, there are two basic load categories—entity loads and body loads.
An entity load is a load that you define for specific geometric entities in your model, such as curves or surfaces. Forces and moments are examples of entity loads.
A body load is a load that you apply to your model as a whole. Gravity is an example of a body load. Typically, you can only use one body load per load set.
For assemblies, you may have several independent bodies in your model. When applying a body load to an assembly, Creo Simulate places the load on all bodies in the model. When loading an assembly, be aware that you must load all independent bodies in the assembly if the analysis you plan to run requires loads. If you do not add loads for all bodies in the model, Creo Simulate is unable to run the analysis.
You can apply a load to a single geometric entity or to multiple entities. When you apply a load to multiple entities, Creo Simulate does not allow you to mix entity types. For example, if you specify a point as the first entity, all remaining entities in the load must also be points.
In the case of multiple entities, Creo Simulate associates the entities by virtue of the fact that they share a load. Thus, you cannot modify or delete the load for each entity individually. Further, deleting any of the entities associated with the load eliminates the load for the other associated entities.
In general, you should plan the placement of your loads according to the model type. For example, if you are working with a solid model, you should try to place your loads on surfaces or surface regions rather than points or curves. With shell models, you should try to place your loads on curves, surfaces, or surface regions, depending on the load type. Although you can place loads on other entity types, this placement is not always optimal.
Creo Simulate assumes the load values you enter are consistent with your principal system of units.
Creo Simulate places many loads using coordinate locations. The way Creo Simulate expresses coordinate directions depends on the current coordinate system's type, whether that coordinate system is the WCS or one you selected during load definition. The following is a chart that defines the coordinate nomenclature for each coordinate system type:
When entering load values in Creo Simulate, use real numbers. You use the sign of the value to express directionality relative to the coordinate axis for which you are defining a load component. For heat loads, you use the sign to indicate whether a loaded entity is a heat source or heat sink.
If you do not enter a value for a load component, magnitude, or direction, Creo Simulate assumes a default of 0 for that aspect of the load. For example, if you leave the Force X field blank for a force load, Creo Simulate assumes the load has no X component.
You can also use expressions as load values. Your expression can include real numbers, arithmetic operators, and Creo Parametric parameter names.
If you apply a load to a surface by selecting the surface with Box Select or Part Boundary, and Creo Simulate later creates a new surface due to a parameter change, the software does not automatically apply the existing load to the new surface.
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