Boom Foot Protruding Flanges Eliminate Weld Root Cracking
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Solution Overview
Problem
Traditional boom foot designs in machinery, such as excavators, face issues with twisting and cracking due to large torsional and axial loads, often requiring additional welds and thicker sections to mitigate stress concentrations at the weld root.
Innovation Solution
The design incorporates a single-piece boom foot casting with protruding flanges that extend beyond a bulkhead, allowing for internal and external groove welds without a weld root, providing full fusion and eliminating stress concentrations at the joint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional boom foot designs with separately welded bulkhead plates and backer strip joints are used, then the boom foot can resist twisting, but weld roots exist from which cracks can originate under large axial and bending loads
Solution Approach 1:
The bulkhead plate and side sheets are merged into a single integrally cast boom foot structure, eliminating the need for separate welding operations. This integration removes the weld roots that serve as crack initiation sites while maintaining the structural integrity and twisting resistance through the unified design.
Solution Approach 2:
The harmful weld roots are extracted/eliminated from the design by using an integral casting approach. The bulkhead and side sheets are cast as one piece, removing the welded joints that create stress concentrations and crack pathways under loading conditions.
2Reliability
If thicker sections or external doublers are used at the boom foot, then stresses at the weld root are reduced to prevent crack propagation, but the device complexity and manufacturing cost increase
Solution Approach 1:
Instead of adding external doublers or increasing section thickness through multiple components, the solution merges the bulkhead and side sheets into a single integrally cast structure. This simplifies the overall design while inherently eliminating the weld root problem that necessitated the thicker sections or doublers in the first place.
3Ease of manufacture
If separately welded bulkhead plates and backer strip joints are used, then the boom foot can be manufactured with standard processes, but additional welds increase the risk of crack initiation and propagation
Solution Approach 1:
The welding process is extracted/eliminated from the boom foot construction by using an integral casting method. The bulkhead plate and side sheets are cast as one piece, removing all weld joints and their associated reliability issues while maintaining manufacturability through established casting processes.
Data Source
AI summary
A boom and boom foot section for connection to a machine, where the boom includes a center section and a box section extending between the foot and center sections. The box section includes first and second side walls. The foot section includes a machine connection for connecting the boom to the machine, and first and second protruding flanges. The first flange couples to the first side wall, and the second flange couples to the second side wall. The foot section can include a bulkhead. The machine connection, bulkhead, and flanges can be formed by a single piece of material. The flanges can be coupled to the side walls by weld joints that do not have weld roots. The flanges can extend beyond the bulkhead to allow internal welds in the weld joint. The flanges and side walls can have double-beveled edges for the weld joints formed by fused groove welds.