Joule Heating Diffusion Bonding for Metallic Honeycomb Cores
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Solution Overview
Problem
The manufacturing of metal honeycomb cores, particularly titanium honeycomb cores, is costly and time-consuming due to diffusion bonding methods that require lengthy vacuum chamber processes, leading to potential strain and defects like crushing, disbonding, or buckling during additional forming operations.
Innovation Solution
A method involving the application of stop-off material patterns on metal sheets to prevent diffusion bonding in specific areas, followed by joule heating and pressing between conductive plates to bond the sheets, allowing for rapid diffusion bonding without the need for vacuum chambers and subsequent forming operations, enabling selective shaping and varying cell density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional diffusion bonding method in vacuum chamber is used, then metal honeycomb core can be manufactured, but manufacturing time is excessive (over eight hours) and equipment cost is high
Solution Approach 1:
The patent replaces the mechanical vacuum chamber system with a joule heating electrical system. Instead of using a complex vacuum environment for diffusion bonding, the invention applies electrical current directly through the metal sheets to generate heat and achieve bonding in atmospheric conditions, dramatically simplifying equipment requirements and reducing manufacturing time to under an hour.
Solution Approach 2:
The invention changes the bonding parameters by using joule heating (electrical resistance heating) instead of conventional thermal diffusion bonding. By controlling electrical current, voltage, and time parameters, the process achieves rapid diffusion bonding without requiring vacuum conditions, thus improving productivity while reducing equipment complexity.
2Shape
If additional forming or bending operations are performed after diffusion bonding, then desired shape and contour can be achieved, but core is subjected to further strain leading to crushing, disbonding, or buckling
Solution Approach 1:
The patent incorporates the desired shape and contour directly into the metal sheets before diffusion bonding. By pre-forming the sheets to the final geometry and then bonding them in that configuration, the structure achieves its desired shape without requiring post-bonding forming operations that would subject the bonded core to damaging strain.
Solution Approach 2:
The invention merges the forming operation with the diffusion bonding process. By forming sheets to the desired shape before bonding, the shaping and bonding operations are combined into a single integrated process sequence, eliminating the need for separate post-bonding forming steps that would compromise structural integrity.
3Adaptability or versatility
If stop-off material pattern is applied to sheets, then selective diffusion bonding locations are achieved, but additional process step is added
Solution Approach 1:
The patent uses stop-off material as an intermediary substance applied to specific areas of the metal sheets to prevent bonding in those regions. This intermediary layer allows selective control of diffusion bonding locations by blocking the bonding process where needed while permitting it where desired, providing adaptability for complex geometries.
Solution Approach 2:
The invention applies stop-off material selectively to specific local areas of the metal sheets based on the desired final geometry. This local application of the stop-off coating enables different bonding behaviors in different regions of the same sheet, achieving the desired shape and contour through localized control of the diffusion bonding process.
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 significantly reduces manufacturing time, eliminates the risk of strain-related defects, and allows for customized honeycomb core designs without the need for additional forming operations, thus saving time, cost, and material while enhancing structural stability and weight efficiency.
Implementation Method 1
applying electric current to the conductive material of the press plates. This allows current to flow through a thickness of the sheets of metal and the sheets of metal are thus diffusion bonded to each other
Implementation Method 2
the sheets of metal are thus diffusion bonded to each other at locations absent the stop-off material
Implementation Method 3
applying or printing a pattern of strips of a stop-off material to surfaces of a plurality of sheets of metal at locations where diffusion bonding is not desired
Data Source
AI summary
A joule-heating press and method for manufacturing a metallic honeycomb core via diffusion bonding. The method may include printing a pattern of strips of a stop-off material to surfaces of a plurality of sheets of metal at locations where diffusion bonding is not desired and stacking the sheets of metal together in a sequence for forming the honeycomb core. Then the method may include steps of pressing the sheets of metal together between two press plates made of conductive material and applying electric current to the conductive material of the press plates. This allows current to flow through a thickness of the sheets of metal and the sheets of metal are thereby diffusion bonded to each other via joule heating at locations absent the stop-off material. Finally, the method may include a step of expanding the sheets of metal into the honeycomb core.