Circle Grid Analysis and Thickness Strain Analysis

Thinning and Circle Grid (Surface) Strain Analyses are Engineering Quality tools that can help determine where trouble spots could develop during the production processing of your parts.  The forming limit of a given steel is based on the thickness and the strain hardening exponent (n-value). The forming limit for other alloys must be determined experimentally. Knowing these parameters, and their minimum values likely to be encountered in production, it is possible to assess if the stamping process is inherently robust enough to withstand the normal variation in material properties.

Engineering Quality Solutions team members have been conducting circle grid analysis for over twenty years.   Our experience enables us to not only perform at a high level, but also teach circle grid analysis to companies and individuals who are interested in understanding the strains produced during the forming process.

For more information on circle grid strain analysis and thickness strain analysis click HERE.

Tooling Buyoff and Launch Support

Engineering Quality Solutions is an active participant in the iterative process that occurs when a tool is close to buyoff.  We’ve participated in buyoffs around the world, lending support to automotive and non-automotive manufacturers.

Whether you call it FLD (forming limit diagram), EVI (early vendor involvement), ESI (early supplier involvement), or CGSA/TSA (circle grid strain analysis / thinning strain analysis), EQS (Engineering Quality Solutions) has the experience and expertise to guide your die engineers on the types of corrective actions necessary to address formability concerns.

Sheet Metal Formability Analysis Training

Engineering Quality Solutions provides training on how you can do formability analysis on your own – we’ll come right to your location or you can learn through our sister company 4M Partners. We also provide training on what makes one steel or aluminum grade different from another – and why you should care.

Forming Limit Curve Generation

You can measure the major strain, minor strain, and thickness strain in the formed part, but what to you compare those values against to say if you have a good, robust stamping?  The strain values that mark the forming limit is called the forming limit curve (FLC).

The shape and placement of the forming limit curve for low carbon steels have been known for decades thanks to the pioneering work of Dr. Stuart Keeler.  All you need are the sheet metal thickness and strain hardening exponent (also known as the n-value).

But what about different types of sheet metal?

Unfortunately, it’s not as simple.  Both the shape and the placement of the FLC must be determined through detailed testing.

Fortunately, Engineering Quality Solutions has both the experience and equipment to do this testing.

We’ve developed forming limit curves for sheet aluminum, zirconium, nickel, brass, and titanium alloys, as well as numerous stainless steel and Advanced High Strength Steel (AHSS) grades.

Let us know how we can help solve your challenges!

Forming Limit Diagram Generation

With your forming limit curve (FLC), you know how much deformation you can subject your sheet metal to before it necks/splits. But just what type of deformation are you doing to your sheet metal? Using the techniques of surface strain analysis (either circle grid or square grid) and thinning strain analysis, you can quantitatively determine the strains your forming process imparts on the sheet. Plotting these strains along with the metal’s forming limit curve creates what is called a Forming Limit Diagram (FLD).

If your forming strains are sufficiently below the metal’s FLC, congratulations, you have a “safe part”, and your forming conditions are sufficiently robust to handle the normal and expected variation in sheet metal properties. If your forming strains are not below the FLC, then at least you now have a graphical representation of where trouble can occur if “low end” properties are shipped in. How do you attack these issues before they turn into problems?

Contact EQS for help!

CAE Computer Simulation

Engineering Quality Solutions has the expertise in providing computer simulations for a wide range of applications including sheet metal forming, tube hydroforming, springback prediction, dent test simulation, structural analysis, and component crash test simulation.  Incremental and one-step approaches are available.

Strain Analysis Reporting Program

This single computer program creates forming limit diagrams and a full engineering report of the analysis. You enter the base data, and the program does all the calculating, plotting, formatting, and presenting of the results.

Contact EQS for help!


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