Friction Stir Spot Welding Sequence for Low-Defect FRP Joints
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Solution Overview
Problem
Existing friction stir spot welding methods face challenges in effectively welding fiber reinforced plastic workpieces without causing excessive heating, resin flow, and defects such as recesses and burrs, particularly when dealing with materials like carbon fiber reinforced plastic.
Innovation Solution
A friction stir spot welding apparatus and method utilizing a pin and shoulder that rotate and advance/retreat in a controlled manner, with a controller managing pressing forces and rotational frequencies to minimize resin flow and prevent defects, ensuring precise contact and reduced tool average position to achieve strong and defect-free welds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the pin and shoulder are pressed firmly against the fiber reinforced plastic workpiece during friction stir spot welding, then welding strength is improved, but excessive resin flow and defect generation (recesses and burrs) occur
Solution Approach 1:
The patent applies dynamics by making the pressing force variable during the welding process. The control unit adjusts the pressing force in multiple stages: initially applying a first pressing force to prevent resin flow, then switching to a second pressing force (higher than the first) after a predetermined time to achieve proper material mixing and welding strength. This dynamic adjustment resolves the contradiction between preventing resin flow and achieving sufficient welding strength.
2Stability of the object's composition
If the rotational frequency of the pin and shoulder is increased during friction stir spot welding, then material mixing is improved, but excessive heating and resin flow occur
Solution Approach 1:
The patent applies periodic action by varying the rotational frequency in stages. The control unit sets an initial rotational frequency, then after a predetermined time period, switches to a different rotational frequency. This periodic variation allows controlled material mixing while managing heat generation, preventing excessive resin flow while achieving adequate material blending for strong welds.
3Strength
If the welding process is extended to ensure complete material mixing, then welding strength is improved, but production efficiency decreases
Solution Approach 1:
The patent applies preliminary action by pre-determining optimal welding parameters (pressing force, rotational frequency, timing) based on material properties and weld requirements. The control unit executes a predetermined sequence of parameter changes at optimized time points, ensuring complete material mixing and welding strength are achieved within a fixed, efficient time frame. This eliminates the need for extended welding times while maintaining high welding quality.
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
The solution effectively welds fiber reinforced plastic workpieces by controlling the pin and shoulder's movement and forces, preventing excessive resin flow and defect generation, resulting in high-quality welds with improved appearance and reduced void defects.
Implementation Method 1
a friction stir spot welding apparatus that partially stirs a welded workpiece including a first workpiece and a second workpiece to weld the first workpiece and the second workpiece to each other
Implementation Method 2
Known is a welding method of welding a metal workpiece and a resin workpiece made of a composite material, such as fiber reinforced plastic
Data Source
AI summary
A friction stir spot welding apparatus including a controller that (A) operates a rotary driver and a tool driver such that a pin and a shoulder are brought into contact with a welded workpiece; (B) operates, after the step (A), the rotary driver and the tool driver such that the pin separates from the welded workpiece; and (C) operates, after the step (B), the rotary driver and the tool driver such that the pin advances toward the welded workpiece. The controller controls the tool driver such that pressing force applied to the welded workpiece from the pin and the shoulder in the step (C) is smaller than that in the step (B) and/or controls the rotary driver such that rotational frequencies of the pin and the shoulder in the step (C) are lower than those in the step (B).