Additive-Manufactured Spark Plug Electrode for Thermal Stress Relief
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Solution Overview
Problem
Spark plug electrodes face erosion and corrosion due to harsh engine conditions, and traditional joining techniques like welding between dissimilar materials lead to thermal stresses and potential cracking.
Innovation Solution
A spark plug electrode design featuring an electrode base, an electrode tip formed via additive manufacturing with laser deposition layers, and an intermediate layer with a coefficient of thermal expansion between the base and tip, eliminating the need for welded joints between dissimilar materials and reducing thermal stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If traditional welding techniques are used to join dissimilar materials (electrode base and electrode tip), then the electrode components can be connected, but thermal stresses and cracking occur due to different coefficients of thermal expansion
Solution Approach 1:
The patent introduces an intermediate layer made of a nickel-based superalloy between the nickel-based electrode base and the precious metal electrode tip. This intermediate layer acts as a mediator that bridges the two dissimilar materials, providing a gradual transition in material properties and reducing the thermal stress concentration that would otherwise occur at the direct interface between dissimilar materials.
Solution Approach 2:
The patent employs composite material structure consisting of three distinct layers: nickel-based electrode base, nickel-based superalloy intermediate layer, and precious metal electrode tip. Each layer is designed with specific material properties to optimize performance, creating a composite structure that combines the advantages of different materials while mitigating their individual weaknesses, particularly regarding thermal expansion mismatch.
2Reliability
If precious metals are used throughout the entire electrode body, then corrosion and erosion resistance is improved, but the cost increases significantly
Solution Approach 1:
The patent applies precious metals only to the electrode tip portion where they are most needed for corrosion and erosion resistance during the sparking process. The electrode base uses a more cost-effective nickel-based material. This local quality approach concentrates the expensive material in the critical high-stress zone while using economical materials in less critical areas, optimizing both performance and cost.
Solution Approach 2:
The electrode is segmented into distinct functional zones: the nickel-based electrode base for structural support, the nickel-based superalloy intermediate layer for thermal management and bonding, and the precious metal electrode tip for sparking and corrosion resistance. This segmentation allows each portion to be optimized for its specific function while minimizing overall material cost.
3Adaptability or versatility
If dissimilar materials are joined together, then different material properties can be utilized, but substantial thermal stresses occur during operation
Solution Approach 1:
The patent changes the material parameter gradient by introducing an intermediate layer with properties that transition between the electrode base and electrode tip. The nickel-based superalloy intermediate layer has thermal expansion and mechanical properties that fall between those of the nickel base and precious metal tip, creating a gradual parameter transition that reduces thermal stress while maintaining the benefits of dissimilar materials.
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 design enhances the durability and service life of spark plug electrodes by minimizing thermal stresses and preventing cracking, while using precious metals efficiently for improved corrosion and erosion resistance.
Implementation Method 1
an electrode tip that is formed on the electrode base and includes a precious metal-based material and a plurality of laser deposition layers
Implementation Method 2
the intermediate layer has a coefficient of thermal expansion (CTE) that is between that of the electrode base and the electrode tip
Data Source
AI summary
A spark plug electrode with an electrode tip formed on an electrode base using an additive manufacturing process, such as a powder bed fusion technique. The spark plug electrode includes an intermediate layer located between the electrode tip and the electrode base, where the intermediate layer has a coefficient of thermal expansion (CTE) that is between that of the electrode base and the electrode tip and includes a whole area connection. In some examples, the whole area connection is non-uniform in thickness so that it is thicker in one section than it is in another section.