When the strain in a part exceeds the elongation a material can withstand, a failure can occur resulting in cracking throughout the part or supports. This is a common issue that can affect parts built with additive manufacturing. The Additive application allows you to quickly look at the design and process settings that would alleviate potential cracking. The High Strain Areas feature allows you to identify regions of the part that may be prone to forming cracks during or after the build process by highlighting critical strain values. Required inputs for this output type include the Support Strain Threshold, Part Strain Threshold, and Strain Warning Factor.

Strain threshold values should be entered as a percent for the support and part material respectively. (Engineering strain can be calculated as the change in length divided by the original length. For example, a 3.0" titanium bar that has been stretched to 3.3" is said to have experienced a tensile strain of 0.1, or 10 percent.) The default values of 10 and 20 percent strain are simply sample values, and you should adjust these values as needed for different materials or other factors that may affect the total elongation of your build material. When a calculated strain exceeds these threshold values, it will be labeled as “Critical.”

The Strain Warning Factor allows you to establish a “Warning” range, to identify further areas where strain is approaching the critical range.

Support Strain Threshold (%)

Percentage strain in the supports above which strain will be considered critical. Defaults to 10%.

Part Strain Threshold (%)

Percentage strain in the part above which strain will be considered critical. Defaults to 20%

Strain Warning Factor

This value is multiplied by each of the strain thresholds above to define limits where strain is labeled as a warning. Defaults to 0.8.

Using default values for all inputs, strains in the supports between 8 and 10 percent will be in the warning range, while strains over 10 percent will be considered critical. Strains in the part between 16 and 20 percent will be in the warning range, while strains over 20 percent will be considered critical.

The output of High Strain Areas can be viewed as part of the On-plate stress/displacement .vtk and .avz files and the Layerwise .vtk files, as well as a High strain regions .csv file. When viewed through the On-plate stress/displacement output, critical strain locations are given a value of 2 and warning locations are given a value of 1. All other locations retain a value of 0 to show low risk. The High strain regions .csv file consists of strain values for all points with strains at or above the warning threshold. Information about each point includes the x, y, and z locations along with the strain value and the deposit layer. The deposit layer represents the actual powder layer during a build. When using the Assumed Strain analysis type, a layer thickness of 50 μm is used to identify the deposit layer of each location.