• PDF / 2,029,053 Bytes
• 12 Pages / 595.276 x 790.866 pts Page_size
• 46 Downloads / 220 Views

DOWNLOAD

REPORT

---

(2020) 20:65

ORIGINAL ARTICLE

3D DIC‑assisted residual stress measurement in 316 LVM steel processed by HE and HPT Tomasz Brynk1   · Agnieszka Teresa Krawczyńska1 · Daria Setman2 · Zbigniew Pakieła1 Received: 1 March 2020 / Revised: 25 April 2020 / Accepted: 21 May 2020 © The Author(s) 2020

Abstract A method has been developed for determining residual stress based on displacement fields near drilled holes analyzed using 3D digital image correlation. Finite element modeling was used to determine corrections for analytical equations describing displacement fields near the blind holes, which made it possible to determine the residual stress distribution over a wide range of hole depth-to-hole diameter ratios and various areas of displacement field measurements using inverse method iterative calculations. The proposed method eliminates many drawbacks of traditional procedure based on strain gauges as hole eccentricity sensitivity and requirement of the relatively large span between holes. The method and testing setup, build-up of generally available components, were used to determine the residual stress distribution for 316 LVM samples processed by two methods from the large deformation group: hydrostatic extrusion (HE) and high-pressure torsion (HPT), by drilling 1.75 and 0.58-mm-diameter blind holes, respectively. In the case of the measurements performed on the surface of a HEprocessed 16 mm bar cut along its diameter, a gradual change was revealed—from a compressive to a tensile residual stress distribution (from ~ − 300 MPa in the center to 400 MPa in 4 mm distance from the edge) in the longitudinal direction, with near-zero values in the radial direction. Moreover, the method was also adapted to perform measurements on the outside surface of the bar, which gave results consistent with those taken along the radius profile (~ 600 MPa longitudinal stress). Measurements on the top surface of a cylinder 10 mm in diameter and 1 mm high processed by HPT showed a high compressive residual stress in the center and a dominant shear component for the holes drilled at different distances from the center. Keywords  Residual stress · 3D digital image correlation · Hydrostatic extrusion · High-pressure torsion · Severe plastic deformation · Austenitic steel

1 Introduction Residual stress may be introduced to materials during both production and service. The presence of residual stress may have a positive or negative influence on a material’s properties, depending on their distribution and magnitude. Knowledge of residual stresses is crucial in investigations related to fatigue life, corrosion resistance and dimensional stability [1]. Therefore, there is a need for accurate methods of measuring the development of residual stress, since the currently * Tomasz Brynk [email protected] 1



Faculty of Materials Science and Engineering, Warsaw University of Technology, Woloska 141, 02‑507 Warsaw, Poland



Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria

2

available methods feature certain