Compression test at different strain rates how to add flow curves for various rates other than in built rates in material properties

Hi,

 

we know two different approaches for flow curves in Simufact Material: "Tables" and "Analytical". You need to select which one to use. There is no better or worse between them.

 

Tables have the advantage that the measured or collected data points can be used more or less directly. "less" is useful to eliminate spread and runaway values of the measurements. In our database Simufact Material define the temperatures and the strain rates you want to use first and after this add the data points. See the Infosheets (linked in the lower right of the dialogues) and the tutorial (linked in the help menu) for details. There are some restrictions on the data used, for example all flow curves need to use the same plastic strain values.

 

Analytical approaches have the advantage that they smooth and extrapolate the available data and allow missing data points. You need to pick one approach (Cold Forming, Hot Forming, Hensel Spittel, GMT, ...) based on the data you have and the judgement which one may be suitable for the material (check the literature) or - very pragmatically - which one works best in the next step. Each approach uses the formula shown in Simufact Material. You have to determine the parameters of the used formula to fit to your data. This is done using external 3rd party applications. There are many data fitting applications around, I tend to use the Solver Add-On of Microsoft Excel. Once you have determined the parameters, enter them in Simufact Material. Note: Most formulas result in a flow stress of 0 for a strain of 0. This is not physically possible and will not work numerically. You need to define a minimum strain reflecting the minimum yield stress.

 

We never extrapolate the flow curves given in the material during the simulation. If outside the definition range, the last value is used. Thus take care to use a reasonable definition range.

 

When taking data from experiments or literature, please check whether the data is true strain and true stress (thus based on the current geometry) or engineering strain and stress (thus based on the initial geometry). Flow curves are true stress strain curves without the elastic strains, only with the plastic strains. See out Infosheet for how to convert stresses and strains if needed.

 

I hope this helps,

 

Christian

 

 

 

 

Hi,

 

we know two different approaches for flow curves in Simufact Material: "Tables" and "Analytical". You need to select which one to use. There is no better or worse between them.

 

Tables have the advantage that the measured or collected data points can be used more or less directly. "less" is useful to eliminate spread and runaway values of the measurements. In our database Simufact Material define the temperatures and the strain rates you want to use first and after this add the data points. See the Infosheets (linked in the lower right of the dialogues) and the tutorial (linked in the help menu) for details. There are some restrictions on the data used, for example all flow curves need to use the same plastic strain values.

 

Analytical approaches have the advantage that they smooth and extrapolate the available data and allow missing data points. You need to pick one approach (Cold Forming, Hot Forming, Hensel Spittel, GMT, ...) based on the data you have and the judgement which one may be suitable for the material (check the literature) or - very pragmatically - which one works best in the next step. Each approach uses the formula shown in Simufact Material. You have to determine the parameters of the used formula to fit to your data. This is done using external 3rd party applications. There are many data fitting applications around, I tend to use the Solver Add-On of Microsoft Excel. Once you have determined the parameters, enter them in Simufact Material. Note: Most formulas result in a flow stress of 0 for a strain of 0. This is not physically possible and will not work numerically. You need to define a minimum strain reflecting the minimum yield stress.

 

We never extrapolate the flow curves given in the material during the simulation. If outside the definition range, the last value is used. Thus take care to use a reasonable definition range.

 

When taking data from experiments or literature, please check whether the data is true strain and true stress (thus based on the current geometry) or engineering strain and stress (thus based on the initial geometry). Flow curves are true stress strain curves without the elastic strains, only with the plastic strains. See out Infosheet for how to convert stresses and strains if needed.

 

I hope this helps,

 

Christian