On Tue, 11 Nov 2025 at 01:07, andy pugh <[email protected]> wrote: > I think they may be bending beams and strain gauges.
For once the AI on Google is spot on (and better than the web results) I made a lot of these when working in the field described. (fatigue testing of CTS specimens). Despite being extremely simple, they are very accurate and surprisingly linear. -----------------begin-AI------------------------------ "Clip gauges" generally refers to clip-on extensometers used in materials testing, specifically for measuring crack mouth opening displacement (CMOD) or large strains in specimens. Fabricating one involves installing strain gauges on a simple flexure device, which requires specific materials and careful procedures. Materials Needed for a Basic Clip Gauge Spring steel strips for the main body of the gauge. Strain gauges (e.g., EP-series for high elongation measurements). Terminals for wiring connections. Connecting block for fixing the strips. Cyanoacrylate (CN) glue for bonding the strain gauges. Cleaning agents: sandpaper, cotton, acetone, iso-propyl alcohol (IPA). Tools: Tweezers, low-tack cellophane tape, light scribing tool or 4H pencil, soldering iron and wires (for connecting wires). Calibration tools: A system for applying known displacements and measuring the output (e.g., a comparator bar). Step-by-Step Fabrication Process Prepare the spring steel strips: Clean and abrade the areas where the strain gauges will be installed using sandpaper. The position should be as close as possible to the region of maximum bending stress. Clean thoroughly: Remove all abrading debris using cotton and acetone, then clean again with IPA. Avoid touching the prepared surface with your fingers afterward. Mark alignment lines: Use a light scribing tool or 4H pencil to mark alignment lines for the gauges. Position gauges and terminals: Use tweezers to place the strain gauges and terminals against the alignment lines. Secure their relative position with low-tack cellophane tape, ensuring the metal foil grid faces up. Bond the gauges: Roll one end of the tape back to expose the backing sheet. Apply a small drop of CN glue to the backing sheet and stick the tape back in place, applying even pressure. Wire the gauges: Solder the connecting wires to the terminals. The gauges are typically wired into a half or full Wheatstone bridge configuration to maximize the signal. Mount the gauge "feet": Design the device so that it can be mounted to the test specimen by bonding or spot welding, depending on the material. Calibrate the finished gauge: The clip gauge is a nonlinear device and requires calibration against known displacements before use. Monitor the "zero" reading during calibration to check for permanent offsets, which may indicate localized yielding. For a detailed guide on the design and calibration, academic resources like the paper on the "Optimum Design of a Ring-Shaped Clip Gauge" provide an analytical framework. --------------------------------------------- https://link.springer.com/article/10.1007/s40799-020-00417-1#:~:text=To%20design%20a%20gauge%20with,available%20in%20commercial%20mathematical%20software. This video shows a completed one, but is otherwise not as good as one might hope. https://www.youtube.com/watch?v=5ry-7iqQIEw -- atp "A motorcycle is a bicycle with a pandemonium attachment and is designed for the especial use of mechanical geniuses, daredevils and lunatics." — George Fitch, Atlanta Constitution Newspaper, 1912 _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
