Allowable Load Envelopes are a way to quantify the capability of a particular design in any combination of loading in 3D space. This is done per panel, per failure criteria (including customer-specific Analysis Plugins). It also takes into account all objects and object-specific failure (i.e. hat crowns, spacing spans, etc.).
Note
If the Allowable Envelope completely contains the Design-To Envelope, the Structure's current design will satisfy all load cases, and therefore has a positive margin of safety.
Notice
Must have HyperX Solver license in order to generate Allowable Load Envelopes. See HyperX Solver for more information.
The amount of load a panel design can sustain – or the allowable – depends on the structural concept chosen for that panel. HyperX optimizes these structural concepts per panel during Sizing. HyperLoads offers an alternative approach to understanding these allowable loads for each Zone.
Using the two panels below as an example - the root panel has been sized as a composite hat to the Max Strain 1 failure criterion, while the panel near the engine pylon has been sized as a metal plate to the Von Mises failure criterion.
Similar to the Design-to Loads, HyperLoads is able to generate three 2D allowable envelope planes based on each design and corresponding Failure Mode.
Combining these three planar views into one 3D surface envelope provides the engineer a way to inspect the allowable combinations of Nx, Ny, Nxy in one plot.
This is done per panel, per failure criteria (including Plugins). It also takes into account all objects and object-specific failure (i.e. hat crowns, spacing spans, etc.). The more complicated the cross-section and failure criteria setup, the more difficult it is to visualize the allowable envelope. HyperLoads eases this burden.
The Idealized Allowable Loads option uses uniformly-spaced Nx, Ny, Nxy unit load load ratios to generate the allowable surface. The result, therefore, is a complete 3D surface. While these loads aren't necessarily representative of the exact loads in selected Zone(s), full allowable surface provides a clearer picture of the total capability of a design in all directions.
To better understand this process, we'll focus on a 2D case in the Nx, Ny plane. First, a unit Nx load is applied (represented by the grey arrow below).
A corresponding margin of safety is calculated using HyperX - in this case, for Von Mises strength.
Adding 1 to the calculated margin of safety gives the corresponding allowable load. This becomes a point on the Allowable Load Envelope.
A full allowable envelope surface is generated by repeating this process for different orientations of unit load vectors.
The amount of unit load vectors used in this process depends on the Resolution setting on the Ribbon. The higher the resolution, the more unit load vectors are used, and the smoother the allowable envelope surface is. But, as a trade off, the higher the resolution, the longer the Allowable Envelope surface takes to generate, as there are simply more calculations to be performed and points to be drawn.
The Actual Allowable Loads option can be used to plot the allowable load - taken directly from HyperX results - for each corresponding Design-to Load in 3D space. In other words, the selected Zone(s)' actual FEA Loads are used to generate this plot. This provides the ability to view the exact loads, allowables, and margin vectors corresponding to the current HyperX Sizing/Analysis result. Due to the sporadic nature of the Design-to Load points, this option does not generate a full 3D surface and can therefore only be plotted as points or vectors.