Key Engineering Materials Vols. 554-557

Abstract: In this Paper an Innovative Multistage Metamodeling Technique is Proposed for Linking Datacoming from Two Different Sources: Simulations and Experiments. the Model is Hierarchical, in Thesense that One Set of Data (the Experiments) is Considered to be more Reliable and it is Labeled as“high-Resolution” and the other Set (the Simulations) is Labeled as “low-Resolution”. the Results Ofexperiments is Obviously Fully Accurate, Except for the only Approximation due to the Measurementsystem and Given the Intrinsically Aleatory Nature of all Real Experiments. in the Proposed Approach,Gaussian Models are Used to Describe Results of Computer Experiments because they are Flexible Andthey can Easily Interpolate Data Coming from Deterministic Simulations. A Second Stage Model is Used,in Order to Link the Prediction of the First Model to the Real Experimental Data. for the Linkage Model,as in the First Stage, a Gaussian Process is Used. in this Second Stage a Random Parameter can be Addedto the Model, Known as Nugget, in Order to take into Account the Process Variability. this Kind Ofmetamodeling can have Different Purposes: Adjusting or Tuning the Simulations, Having a Better Tool Todrive the Design Process, Making an Optimization of a Parameter of Interest. in the Paper, its use Foroptimization of a Single Responsey with Two Design Variables x1 and x2 is Demonstrated. the Approachis Applied for Modeling the Crash Behavior in Three Point Bending of Metal Foam Filled Tubes.

Abstract: Improvements in parallel computing and adaptive remeshing have permitted to simulate a wide range of metal forming processes within few hours or days on modern multi-core workstations. However, they do not tackle the issues encountered in incremental forming processes, making them very challenging. Multi-mesh methods opens very interesting doors in this domain, making possible to take advantage of adaptive remeshing techniques (optimizing the ratio precision/cost) without its usual drawbacks (loss of information and diffusion issues).We present in this article a fully parallel Dual-Mesh implementation in the commercial FEA software FORGE®, compatible with a wide range of other FEM facilities. Speed-up larger than 4 are common for incremental forming simulations, and speed-up larger than 10 can be reached in favorable cases. Parallel efficiency is the same than for our standard computations (>80% for more than 2000 nodes per core).

Abstract: Metal flow inside the container and in the metal behind a butt-ended die bridge in idealized aluminum extrusion welding has been investigated by FEA and experiment with respect to the deformation of the material flowing around the bridge and into the layers close the extrusion seam weld. Along the mid-axis of the extrusion process the effective strain subjected to the extrusion material can be determined in three different ways. One way is to determine the strains from grid pattern experiments that reveal the real deformations. When it comes to FEA there are two options; the strains can be determined from the initial and final positions of a number of material points distributed along the mid-axis of the material, where after traditional theoretical strain-equations can be used to calculate the effective strain distribution along the axis. Another possibility is to use the post-processor of the software to calculate the strain distribution. In this work the effective strain distribution along the mid-axis of the billet inside the container volume were determined by all these three methods. The effective strain in the thin layer of the squeeze zone ahead of the dead zone in front of the die bridge determined from the experiments was found to be much larger than the strains elsewhere along this axis. The same was the case when effective strain was determined by FEA from the computed position of the points, but this strain value was predicted approximately 10% lower than the corresponding value from the experiments in the layer with the heaviest strains. However, when this effective strain distribution was calculated by the post-processor of the software the high-strain layer in the squeeze zone was not revealed at all, instead the effective strains were predicted rather even over the whole length of the mid-axis. Corresponding effective strain distributions were determined along the mid-axis of the extrusion material in the weld chamber also, and after outflow of this material into the extrusion seam weld of the resulting profile where no experimental information is available. When this effective strain distribution was computed by FEA, based on initial and final position of points, very different strain values were obtained as compared to when same strains were collected directly from the post-processor. It is believed that the first results, i.e., the effective strains computed from the points are quite accurate, while those values calculated by the post-processor are less reliable.