Revision as of 13:58, 25 April 2016

The damage model parameters for Magnesium AZ61A alloy were fitted using DMGfit_55p_v1p1. The original sources, the fitting procedure and results are detailed below.

Source Data

The source data was based on the digitization of AZ61A stress-strain curves. A compression and a tension stress-strain curves, respectively, were digitized.

Mg.009 AZ61A magnesium alloy forging compressive stress-strain curve. ^[1]

Composition: Mg-6Al-1Zn. UNS M11610

Mg.009 AZ61A magnesium alloy forging tensile stress-strain curve. ^[1]

Composition: Mg-6Al-1Zn. UNS M11610

Digitized data files:

• File:AZ61A-Mg-Compresion.txt
• File:AZ61A-Mg-Tension.txt

Fitting Procedure

We followed the general outline of the fitting procedure detailed on the DMGfit_55p_v1p1 page with some modifications to accommodate for the types of available data. For example, temperature dependence constants were not fitted because we did not have temperature dependent data.

First we preformed a rough manual fit, by adjusting several of the Cn constants as detailed below, followed by an automatic optimization for the same set of constants. The initial manual fit helped the goal seeking algorithm move in the right direction toward convergence and converge faster.

The following parameters were fitted manually the order listed below:

1. Fit C3, which is the yield stress.
2. Fit C9, C7
3. Fit C15, C13
4. Fit Cb
5. Readjust C9, C7, C15 and C13 after fitting Cb.

Finally, we performed an optimization procedure. To do this we unchecked the parameters mentioned above, while leaving the rest of the parameters checked and hit the 'optimize' button.

Results

Screenshot of the DMGfit UI after performing the fitting operations listed in AZ61A#Fitting_Procedure

References

1. ↑ ^{1.0 1.1} "Magnesium Design", Dow Chemical Co., 1957. As published in Aerospace Structural Metals Handbook, vol 3, Code 3603, CINDAS/USAF CRDA Handbooks Operation, Purdue University, 1995, p4