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Autodesk advances weld-line strength prediction

Issue: November 2017

Autodesk has developed new software that works with its Moldflow Insight flow-simulation program to predict the weld-line strength of plastic parts.

Helius PFA takes into account a wider spectrum of material behaviors and properties than those previously generated by the Moldflow Insight software, which results in a more accurate representation of the plastic part. With it, more accurate characterizations of material properties can be transferred into a finite element analysis (FEA) program, said Matt Jaworski, senior technical specialist for Moldflow simulation. PFA stands for progressive failure analysis.

Helius PFA software can determine the orientation of fibers in a polymer.

The advancement allows flow-simulation results from Moldflow Insight to be more accurately mapped or transferred to FEA software for structural analysis, such as Autodesk’s Nastran In-CAD, Abaqus or Ansys.

Previously, users of Moldflow Insight utilized Moldflow’s Structural Alliance software or its scripting software to transfer the results from the simulation into FEA software for structural analysis.

Helius PFA can define and account for nonlinear material properties of unfilled or reinforced materials. The ability of the software to determine the orientation of fibers in a polymer provides for a better representation of the stress/strain behavior of the material, resulting in more accurate modeling of part deflection and strength, Jaworski said.

The software can automatically vary its calculations of the stiffness and strength of a material at various points in a part to reflect the influence of fiber orientations and weld lines, and predict where a part will experience stress due to compression. Areas where stress is likely due to fiber orientations and weld lines can then be accounted for, providing greater insight into the integrity of the part, Jaworski said.

The software yields detailed information regarding the temperature and pressure of the melt fronts as they come into contact with each other. Each point on the weld line can have a different strength due to the manufacturing process. How a weld line is formed, as well as the movement and final location of the weld line, can be simulated.

The software can determine if fibers in a reinforced material are able to bridge the boundary where the melt fronts come together in a weld line and can indicate areas along the weld line where the bond is strong or weak. Weld-line strength impacts the integrity of the part. This capability shows the user the weakest point of a weld line, and improves the accuracy of the FEA strength analysis, Jaworski said.

Helius PFA also allows users to run dissimilar mesh geometries for the flow simulation and for the FEA software. Previously, the Moldflow software and an FEA solver had to use the same type of mesh geometry. This allows the user to select the ideal mesh type, which can improve solve time and accuracy.

The software has an alignment tool that accounts for different coordinate systems of each mesh, overlaying one with the other. This capability also gives the user the flexibility to have different geometric features in the FEA (for example, holes, or trimming back a portion of the part) that the Moldflow Insight geometry does not have. Aligning the separate meshes keeps each mesh and model-building workflow autonomous.

The software also allows multiple parts to be combined into a single assembled structure to be run together in a structural analysis program. Previously, Jaworski said, an assembled structure had to be analyzed according to its constituent parts, rather than all at once.

Autodesk developed Helius PFA for users who are replacing metallic parts with advanced plastic materials and composites for lightweighting. The Helius PFA software suite includes the Advanced Material Exchange user interface for mapping manufacturing data from Moldflow Insight to a structural simulation, Jaworski said.

Overall, Helius PFA improves the accuracy of the material model, shows how the nonlinear, anisotropic behavior of advanced materials influences product performance, and accounts for weld-line formation/movement and how the strength of the weld line varies based on the injection molding process.

Helius PFA is included in the license for users of Autodesk’s Moldflow Insight Ultimate subscriptions, its highest level of the flow simulation software in the Insight line. Users with the Premium or Standard level of Moldflow Insight can add a license for Helius PFA.

Mikell Knights, senior staff reporter



Autodesk Inc.,
San Rafael, Calif., 415-507-5000, www.autodesk.com