Material Properties: Our referencies in the field of material data identification, Parsolve GmbH, Düsseldorf

The Parsolve GmbH is now working together with 8 of the 100 largest German companies as well as several medium-sized companies. At this point, you will see selected reference projects in which our method FEMCard Pro was successfully applied.

 

Crash simulation of a compact elastomer (Volkswagen AG)

An under both the experimental and the optimization aspect extremely challenging project was completed in 2012 for the Volkswagen AG in Wolfsburg. The material cards thus determined have been successfully validated and since then are used for the FEM crash simulation. This requires a high quality of the material parameters. This could be ensured with the use of our identification process.

 

On the experimental side, both tensile tests on perforated rectangular specimens were performed at three different speeds (quasistatic, 0.3 m/s and 5 m/s) as well as quasi-static compression tests on cylindrical specimens. There were achieved maximum local strains of about 100% and 50% respectively. By using this experimental program, all "component relevant" multiaxial stress states and strain rates are considered.

 

Tensile Tests

Compression Tests

Using simultaneous multi-parameter optimization the complete material data set of a suitable viscoelastic material model was determined  and verified. Thereby a material data set which can optimally image the full range of loading conditions and strain rates is estimated. In the following figures based on the comparison of local displacement curves is shown how well measurement and simulation agree for both coupled tensile and shear loads at high strain rates as well as coupled compression and shear loads in the quasi-static case. The images on the left show the results of the verification of a perforated tensile specimen, the pictures right next to it the results for the compression test. It is shown the position of verification nodes and the displacement curves from measurement and simulation respectively.

 

verification tensile test

verification compression test

Viscoelastic Behaviour of elastomeric foam (ABB AG)

An under both the experimental and the optimization aspect quite similar project like the project for the Volkswagen AG has been conducted for the ABB AG in 2012. The material cards thus determined have been successfully validated by means of compression tests at drop towers and since then are used for the FEM simulation at ABB AG. The main difference regarding the material behaviour is the compressibility of the foam which has to be taken into account by choosing a different viscoelastic material law.

 

Again both tensile tests on perforated rectangular specimens were performed at three different speeds (quasistatic, 0.3 m/s and 5 m/s) as well as quasi-static compression tests on cylindrical specimens. There were achieved maximum local strains of about 100% and 50% respectively. By using this experimental program, all "component relevant" multiaxial stress states and strain rates are considered. The following pictures show the experimental setup for high speed tensile tests and quasistatic compression tests.


Tensile Tests (High Speed)
Compression Tests (quasistatically)

The tensile and compression samples were provided with a pattern of gray values ​​and then measured with the optical measuring system ARAMIS at different load conditions. In the following figures the specimens as well as results of the optical analysis are shown.

 

Specimens

Optical Measurement

Using simultaneous multi-parameter optimization the complete material data set of a suitable viscoelastic material model was determined  and verified. Thereby a material data set which can optimally image the full range of loading conditions and strain rates is estimated. In the following figures based on the comparison of local displacement curves is shown how well measurement and simulation agree for both coupled tensile and shear loads at high strain rates as well as coupled compression and shear loads in the quasi-static case. The images on the left show the results of the verification of a perforated tensile specimen, the pictures right next to it the results for the compression test. It is shown the position of verification nodes and the displacement curves from measurement and simulation respectively.

 

Verification tensile test

Verification compression

Validation on drop tower

After successful verification of the material data validation measurements were carried out on a drop tower. For this, the compression specimens which were loaded quasistatically in the context of parameter identification were loaded with a fall velocity of 1.8 m/s and 5 m/s respectively. The measured global force response as well as two local displacements on the specimen surface were compared with the corresponding FE simulation results. In the following, the test stand, the test specimen together with the marks for the Motion Tracking and validation results are presented. Simulation results are shown in red. In the last diagram, the dotted lines are the displacements in the specimen center, the solid lines are the displacements on the top of the specimens. It is seen that the identified and verified material data set for a viscoelastic foam also lead to very good results in the simulation of the pressure behavior at high strain rates.

 

Test stand
Marked specimen
Validation of global force
Validation of local displacements

PBT in Automotive Engineering

One of the recently successful implemented Testing and Evaluation concepts is used for the determination of material data for Drucker Prager plasticity. To take into account the strong dependance of the material on the loading direction, compression tests on (perforated) cylinders are conducted additionally to tensile tests on perforated rectangular specimens.

 

Perforated Specimens for tensile and compression tests
Results of the optical measurement
,tensile and compression specimens

The colored pictures show on the one hand the vertical strains on the tensile specimen - one can clearly see the localization effects on the left and right of the hole - and on the other hand the characteristics of the strain in the principal axis system of the compression specimen. The following figures show the verification of the simulation model by comparing the local displacement values of the cylinder. Here all three spatial directions are considered, which is an absolute innovation in the field of validation of simulation models and related material parameters.

 

verification of a compression test

Aluminium die casting for gear housings

Together with the University of Kaiserslautern and the GM Powertrain GmbH, the material parameters for elasto-plasticity have been determined using 3 different specimen geometries, namely a conventional tension rod, a perforated specimen and a side-notched specimen. See below the perforated specimen with a stochastic grey scale pattern:

 

 

To accurately determine the fraction of plastic deformation the specimens were initially charged only up to about 85% of the breaking load and relieved again (see chart at right). The measurement and evaluation method described on the side   "material parameters" has been utilized. All experiments carried out, so all three specimen types and all retries have been considered within the global material data optimization. On the following animated GIF a verification of the calculated material data set can be seen; a comparison of the measured and simulated displacements of the individual differently loaded regions of a perforated specimen.

 

point-and-click to animate

 

One can clearly see the good overall correlation, especially during and after the process of load relieving. The permanent deformations are represented at all relevant points of different stress conditions very well. This becomes even clearer when you look at the displacement over time, and force over displacement curves in detail at 5 representative nodes:

 

 

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Elastomer in medical engineering

Together with the ECP Entwicklungsgesellschaft mbH, Berlin, the material data set for viscoelasticity was determined. Hereby the parameters for short term an long term relaxation were identified together with the parameters for the basic elasticity. Tensile tests have been conducted with perforated rectangular specimens. Hereby two different time domains have been considered. The following illustrations show the clamped specimen as well as the force-time curves of the two types of tests:

 

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If you look at the corresponding verification, again a very good correlation between the measured and simulated displacement curves at almost all points on the specimen surface, is achieved. A separate analysis of the tests for the short-term and long-time behavior makes an even better fit possible, depending on if the one or the other material behavior in the later application is dominating.

 

Point-and-click to animate

The performed FEM analysis using the determined material data set (18 material parameters for the elastic and viscous behavior) shows clearly how well the viscoelastic behavior can now be simulated. One can see the strain, the von Mises stress and the hydrostatic stress at maximum force (above) and at the end of the experiment (below).

Point-and-click to enlarge

 

 

 

 

 

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