ASTM E837 – Residual Stress Measurement by Center Hole Drilling
Residual stresses present after fabrication, welding, forming, and other industrial processes can be dangerous if they are too high, because they combine with the operating stresses. G2MT Labs offers high-precision surface residual stress analysis using the ASTM E 837 practice via hole drilling with rosette strain gauges. In this method, a very carefully drilled hole is surrounded by strain gauges that measure the change in strain in three axes as the hole is drilled. Center hole drilling allow for very accurate determination of surface residual stress at depths up to 1-2 millimeters. At G2MT Labs, we developed and perfected our own internal practice because we needed these measurements ourselves, and now we are proud to offer them commercially. In cases when it’s a rush, the tests can be performed within a few hours and we can rapidly provide the residual stress data you need!
Benefits of Hole Drilling for Residual Stress Measurement
- Rapid preparation: Samples can be prepped and ready in just a few minutes.
- Trusted and Reliable: The ASTM E 837 methodology and equipment from Vishay Measurement Group provide highly accurate data that has been proven reliable time and again.
- Speed: Depth profiles available within an hour.
- Expertise: Our team includes metallurgists, fracture mechanics experts, and FEA capabilities to help you understand and implement the data.
- Versatile: the hole drilling method is applicable to a wide range of metals and materials (almost anything you can successfully drill into!)
- Portable: due to the relatively small size, we offer in-field testing of components. Our on-site team can head your way within hours when time is of the essence.
How Does Hole Drilling Measure Residual Stress?
The hole drilling method works by removing layer after layer from a small hole surrounded by strain gauges. As the hole is drilled, stresses within the part change the shape of the hole and influence the strain gauges, leading to slight distortions of the hole. These slight distortions are read by the strain gauges and can be converted into residual stress analyses through the methods described in ASTM E 837-13A. The hole drilling procedure starts with careful alignment and positioning of the drilling tool tip via a precision milling guide with a microscope.
Drilling is performed in layers and measurements are made at staggered depths, typically up to a depth equal to the diameter of the drilling bit. Each drilling increment is recorded by strain gauges, enabling a calculation of strains in three-dimensions through your component. The entire process, including the calculations for determining residual stress levels, is described in ASTM E 837.
References for Hole-Drilling in General
- ASTM E837 – 13A Standard Test Method for Determining Residual Stresses by the Hole-Drilling Strain-Gage Method
- Good Practice Guide No. 53 – The Measurement of Residual Stresses by the Incremental Hole-Drilling Technique, P V Grant, J D Lord and P S Whitehead, The National Physical Laboratory
- G. S. Schajer and E. Altus, “Stress calculation error analysis for incremental hole-drilling residual stress measurements”, Journal of Engineering Materials and Technology, Vol. 118, No. 1, pp. 120–126, (1996).