Gridded circle
An alternate approach based on Digital Image Correlation (DIC), where a camera tracks the movement of a random speckle pattern applied prior to forming, W-26, H-22, M-21 follows the strain evolution which occurs during forming and is not affected by non-linear strain paths.Īlthough DIC strain analysis is more accurate and informative, it is a higher-cost approach best suited for laboratory environments. These approaches determine only the strains after forming, and are constrained to assume linear strain paths. Similarly, forming changes the regular dot pattern, allowing for calculation of the strains. Forming turns the squares into rectangles, and the camera/computer measures the expansion or contraction of the nodes at the corners of the squares to determine the strains. Instead of circles, most camera-based measurement techniques for analysis after forming use a regular grid pattern of squares or dots. Techniques and caveats are highlighted in Citations S-59 and S-60. Typically, these are viewed through magnifiers, making it easier to discern the critical dimensional differences. Conventional measurement occurs after forming, and involves a calibrated Mylar™ strip marked with gradations indicating the expansion or contraction relative to the initial circle diameter. Forming turns the circles into ellipses, with the dimensions related to the major and minor strains. Keeler was the Technical Editor of these AHSS Guidelines through Version 6.0, released in 2017.Īs the name suggests, a flat blank is covered with a grid of circles of precisely known diameter, typically applied by electrochemical etching. Stuart Keeler as its primary evangelist for nearly 50 years. The earliest method is known as Circle Grid Strain Analysis (CGSA), with Dr. Several methods are available to measure the strains on formed parts. When paired with the strains generated during forming of an engineered part, the associated Forming Limit Diagram (FLD) provides guidance on which areas of the part might be prone to necking failures during production stamping conditions that replicate those used in the analysis. The FLC is dependent on the metal grade and the specific methods used in its creation.
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Improvement of Delayed Cracking in Laser Weld of AHSS and 980 3rd Gen AHSS.Hot cracking investigation in HSS laser welding with multi-scale modelling approach.Hybrid Laser-Arc Welding (HLAW) Pore Formation and Prevention.Adding Colloidal Graphite to Al-Si-Coated PHS.Laser Welding Processes and Applications.Role of Coatings in Defect Formation AHSS welds.Analyze Hydrogen Induced Cracking Susceptibility.Additive Mfg for Sheet Metal Forming Tools.Coil Processing:Straightening & Leveling.Non-Linear Strain Paths (Stress-Based FLCs).Delayed Cracking (Hydrogen Embrittlement).Improvement by Metallurgical Approaches.Once you have a forming problem, chances are circle grid analysis won’t be able to help you, unless it’s intermittent enough to form a “good” part from time to time. The goal of using circle grid strain analysis is to predict potential problems before they become problems. By measuring the longest part of the ellipse (called the “major strain”) and the shortest part of the ellipse (called the “minor strain”), it is possible to determine how close any stamped part is to splitting or fracturing. After the part is formed, the circles have been stretched into ellipses. Literally, a grid of circles of known diameter is etched to the surface of the sheet metal to be formed.
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The name itself is a fairly accurate description of the process. JSTOR ( October 2009) ( Learn how and when to remove this template message)Ĭircle grid analysis ( CGA), also known as circle grid strain analysis, is a method of measuring the strain levels of sheet metal after a part is formed by stamping or drawing.Unsourced material may be challenged and removed.įind sources: "Circle grid analysis" – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.