Ultrasonic Residual Stress Calculation in Pipeline Weld Seam Metal
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Solution Overview
Problem
Conventional methods for calculating residual stresses in welded pipeline joints are destructive and unable to accurately assess the quality of welds or determine the maximum residual stresses in the seam metal, as they only measure differences between longitudinal and hoop stresses in the base metal adjacent to the weld, which are lower than those in the seam metal.
Innovation Solution
The method involves measuring the propagation times of ultrasonic waves along and across the pipe axis using the ultrasonic echo method, applying numerical modeling to determine balancing sections where hoop stresses in the base metal are minimal, and using acoustoelasticity equations to calculate the maximum residual longitudinal and hoop stresses in the seam metal by defining a balancing coefficient based on the ratio of stresses in the seam and base metal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional ultrasonic method is used to measure residual stresses, then the measurement can be performed non-destructively in the base metal adjacent to the weld, but the method cannot obtain the maximum residual stress values in the seam metal itself
Solution Approach 1:
The patent uses the base metal as an intermediary to indirectly determine seam metal stresses. By measuring stresses in the accessible base metal and applying a balancing coefficient (k) derived from numerical modeling, the method transfers stress information to the inaccessible seam metal region, solving the problem of无法直接测量焊缝金属应力
Solution Approach 2:
The patent performs preliminary numerical modeling and finite element analysis to determine the balancing coefficient k before actual measurements. This pre-established relationship between base metal and seam metal stresses allows direct calculation of seam stresses from base metal measurements, eliminating the need for direct seam metal measurement
2Measurement precision
If the mechanical probing hole method is used to calculate residual stresses, then the calculation can be performed based on elastic unloading, but the method requires violating the integrity of the controlled product
Solution Approach 1:
The patent replaces the mechanical probing hole method with an ultrasonic wave-based measurement system. Instead of mechanically drilling holes to induce elastic unloading, the method uses ultrasonic wave propagation characteristics to non-destructively determine residual stresses, maintaining product integrity while achieving stress measurement
Solution Approach 2:
The patent changes the measurement parameter from mechanical deformation (probing hole method) to ultrasonic wave propagation time. By measuring the time of flight of ultrasonic waves through the material, the method indirectly determines stress state without mechanical intervention, preserving product integrity
3Device complexity
If the conventional method measures only the difference between longitudinal and hoop stresses, then the measurement procedure is simplified, but the results cannot be used to assess weld quality or perform strength calculations
Solution Approach 1:
The patent extends the measurement from a single stress difference value to a multi-dimensional stress state characterization. By measuring ultrasonic wave propagation in multiple directions (along and across the pipe axis) and applying numerical modeling, the method reconstructs the complete biaxial stress state, providing independent longitudinal and hoop stress values needed for comprehensive weld assessment
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for non-destructive, independent calculation of longitudinal and hoop residual stresses in the seam metal, enabling accurate assessment of weld quality and strength calculations by correlating stresses between the seam and base metal, even after the weld is completed.
Implementation Method 1
measuring the propagation times of ultrasonic waves along and across the pipe axis using the ultrasonic echo method
Implementation Method 2
using acoustoelasticity equations to calculate the maximum residual longitudinal and hoop stresses in the seam metal
Data Source
AI summary
Methods for non-destructive testing of engineering materials. In one aspect, a method can be used to calculate residual longitudinal and annular welding stresses in welded joints and can be used to assess the quality of pipeline welds according to the criterion of the level of residual stresses and to determine the initial parameters for the pipeline strength calculation. In some aspects, the method enables independent calculation of the longitudinal and hoop residual stresses. Thus, the stresses can be calculated in the seam metal of the pipelines welds, where they reach their maximum values. The method can be used to test a pipeline section using an ultrasonic echo method to measure the propagation time for longitudinal waves and transverse waves polarized along and across the pipe axis. The measurement results define the distinguishing features of the stress state of a welded joint for a specific type of pipe by numerical modeling.