Initial stress for warp in 2nd principal direction result

The Initial stress for warp in second principal direction result shows the total of all stresses that contribute to warp in the direction perpendicular to the first principal direction.

This result is generated by a Pack analysis using Midplane or Dual Domain analysis technologies.

Note: This result is not generated if the Residual Strain shrinkage model is selected for the material used in the analysis. View the material properties data for the specified material on the Thermoplastics material dialog (Select Material > Details > Shrinkage Properties tab).

Using this result

The stress inputs to warp are created as a result of:

shear stresses generated during mold filling or packing,
the thermal stresses created by the part cooling to room temperature after solidification,
the compensating effect of packing pressure present at the time of solidification.

Variations in the initial stresses throughout the part can be caused by:

different areas of the part cooling at differing rates due to variations in thickness and part surface temperatures,
variations in packing pressure distribution in the cavity.

To minimize these variations, uniform cooling and packing are required.

Note: The initial stress for warp is calculated by the Pack analysis and represents the total stresses influencing warp. This includes the thermal stress which would be created if the part cooled to room temperature while still constrained in the mold. In reality, this total aggregation of stresses does not usually exist in the part at one time because warp deformation and cooling to room temperature occur concurrently after ejection. This result is best used to understand the causes of warpage deflection or as an input to warp and stress analyses in external structural FEA software.

Things to look for

Positive values on the plot indicate tension and negative values indicate compression.

Initial stresses for warp are almost always positive because the compensation effect of packing pressure is usually less than the thermal stress caused by cooling to room temperature.
Negative values indicate overpacking has occurred.

For an indication of which portions of the part are under tension and which are under compression after deformation, use the Warp stress results.