Multi-Pass Weld Toe Geometry for Fatigue Crack Resistance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multi-pass welds created by existing methods are susceptible to fatigue cracking, particularly in the toe region, due to stress concentrations and residual stresses, and current methods to improve resistance are labor-intensive or impractical.
Innovation Solution
An electric arc welding method that includes applying a stand-alone toe weld on one construction element before positioning, which forms the toe of the weld and is connected only during the welding process, allowing for better control and quality of the welding bead, and optionally a stand-alone base weld to improve the root area, both of which are made under controlled conditions to reduce residual stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multi-pass welds are created by existing methods, then the welding process can be completed, but the weld is susceptible to fatigue cracking due to stress concentrations and residual stresses
Solution Approach 1:
A stand-alone toe weld is applied to the first construction element before positioning it relative to the second construction element. This preliminary welding action creates an optimized toe geometry that reduces stress concentrations before the main multi-pass welding process begins, thereby improving fatigue resistance without requiring additional post-weld operations.
Solution Approach 2:
The welding process is divided into distinct segments: a stand-alone toe weld applied separately before positioning, and then the main multi-pass weld. This segmentation allows the toe weld to be optimized independently for fatigue resistance while the root pass and filling beads address connection strength, resolving the contradiction between fatigue resistance and connection integrity.
2Reliability
If methods are used to increase resistance against fatigue cracking (such as shot peening or hammering), then fatigue resistance improves, but the process becomes labor-intensive
Solution Approach 1:
The stand-alone toe weld is designed to automatically provide the stress-reducing geometry that would otherwise require labor-intensive post-weld operations like shot peening or hammering. The welding process itself creates the beneficial compressive stresses and optimized geometry, making the system self-sufficient and eliminating the need for additional manual treatments.
3Reliability
If the weld surface is made as smooth as possible to reduce stress concentrations, then fatigue resistance improves, but this requires very skilled welders and is often hard to achieve
Solution Approach 1:
The stand-alone toe weld is applied as a preliminary step with controlled parameters to create an optimized surface geometry. This preliminary action establishes the smooth toe region before the main welding process, reducing the skill requirement for achieving smooth surfaces during the subsequent root pass and filling bead operations.
Solution Approach 2:
The stand-alone toe weld uses specific welding parameters (lower heat input, controlled bead geometry) that are optimized for creating smooth surfaces with minimal stress concentrations. By changing the welding parameters for this specific preliminary step, the process achieves high fatigue resistance without requiring exceptional welding skill during the main connection process.
4Manufacturing precision
If a stand-alone toe weld is applied before positioning, then the toe geometry and quality can be better controlled, but an additional welding step is required
Solution Approach 1:
The welding process is segmented into a stand-alone toe weld step and a main multi-pass weld step. This segmentation, while adding a step, allows each step to be optimized for its specific purpose: the toe weld for geometry control and fatigue resistance, and the main weld for connection strength. The segmentation enables automated or semi-automated processes that can maintain precision without proportionally increasing overall complexity.
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 method enhances the fatigue resistance of the multi-pass weld by improving the geometry and reducing residual stresses in the weld area, leading to a more robust and durable joint with increased resistance to cracking.
Implementation Method 1
electric arc welding method for creating a multi-pass welded joint between a first metal construction element and a second metal construction element
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
The invention pertains to an electric arc welding method for creating a multi-pass welded joint comprising the following steps: - a first stand-alone toe weld (41) on a first construction element (10), - then, arranging the first construction element (10) and a second construction element (20) in a joining position, with a distance (42) being present between the first stand-alone toe weld (41) and a root area (32) of the welded joint to be created, - while maintaining the joining position, making a first weld connection between the first construction element and the second construction element by applying a root pass (43) at the root area, - then, applying one or more filling beads (44), wherein the first stand-alone toe weld, the root pass and the one or more filling beads together form part of the welded joint, wherein the first stand-alone toe weld forms the toe of said welded joint at the side of the first construction element.