10 Jul 2024

A Study of Phased-Array Ultrasonic Testing (PAUT) for Detecting, Sizing, and Characterizing Flaws in the Welds of Existing Hydraulic Steel Structures (HSS)

Abstract: Hydraulic steel structures (HSS) are components of navigation, flood control, and hydropower projects that control or regulate the flow of water. Damage accumulates in HSS as they are operated over time, and they must be inspected periodically. This is often accomplished using nondestructive testing (NDT) techniques. If damage is detected, the structure’s fitness for continued service must be evaluated, which requires information on the location and size of discontinuities. This information can be obtained using ultrasonic testing (UT) techniques. However, there is limited information on the reliability of UT techniques with respect to detecting, sizing, and characterizing flaws in HSS. This study addresses this gap. Round-robin experiments were carried out using phased-array ultrasonic testing (PAUT) to scan weld specimens representing a variety of HSS geometries. The results of the round-robin experiments were analyzed to estimate the probability of detection (POD) and to assess the influence of factors potentially affecting POD. Uncertainty in estimates of flaw length and height were described, and partial safety factors were derived for use in fitness-for-service analyses. These results demonstrate the importance of the technician as a factor influencing the reliability of NDT techniques applied to HSS.

18 Sep 2023

Accelerated Corrosion of Infrastructural Seven-Strand Cables via Additively Manufactured Corrosion Flow Cells

Purpose: The purpose of this project was to generate an accelerated corrosion methodology capable of producing seven-strand cables with simulated corrosive defects for calibration of nondestructive analysis (NDA) techniques. An additively manufactured accelerated corrosion cell was motivated and designed. Previous attempts at accelerated electrochemical corrosion used a large cable area with a current density that was too low (i.e., 1 A/m²)* to effectuate efficient corrosion. The accelerated corrosion cell presented here takes advantage of the restricted area within the corrosion flow cell to maximize the corrosion rate in a consistent and calibrated manner (i.e., 2,000 A/m²).

1 Oct 2021

Acoustic Nondestructive Testing and Measurement of Tension for Steel Reinforcing Members

Abstract: Many concrete structures contain internal post-tensioned steel structural members that are subject to fracturing and corrosion. The major problem with conventional tension measurement techniques is that they use indirect and non-quantitative methods to determine whether there has been a loss of tension. We have developed an acoustics-based technology and method for making quantitative tension measurements of an embedded, tensioned steel member. The theory and model were verified in the laboratory using a variety of steel rods as test specimens. Field tests of the method were conducted at three Corps of Engineers dams, located in Oklahoma, Georgia, and Illinois. Measurements of the longitudinal and shear velocity were able to be made on rods up to 50 ft long. Not all rods of this length were able to be measured and the quality and consistency of the signal varied. There were fewer problems measuring the longitudinal velocity than shear velocity. While the tension predictions worked in the laboratory tests, the tension could not be accurately calculated for any of the field sites. This is because we were not able to obtain the longitudinal or shear velocities in an unstressed state or precise measurements of the longitudinal and shear velocities due to the lack of knowledge of the precise length of the rods in the tensioned state.