Sheet Metal Skin Stretch Forming for Convex-Concave Curvature
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing sheet metal skins for aircraft engine thrust reverser assemblies, such as composite layup and metal bonding, are costly, complex, and require expensive insulation due to the complex shapes and proximity to hot engine components, leading to increased weight, assembly complexity, and maintenance costs.
Innovation Solution
A stretch forming process that plastically stretches sheet metal into convex and concave shapes using a mandrel and dozer blocks to form thin metal skins with convex and concave curvatures, reducing the need for multiple pieces and splice joints, and minimizing the requirement for expensive insulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If composite layup or metal bonding methods are used to produce inner fixed structures, then the structural integrity and acoustic attenuation are improved, but the production cost and assembly complexity increase significantly
Solution Approach 1:
The patent divides the complex inner fixed structure into multiple sheet metal skin panels that can be individually formed and then assembled. Each panel is formed separately using stretch forming, allowing for simplified manufacturing of individual components that are later joined together to create the complete complex structure.
Solution Approach 2:
The patent changes the material parameter from composite materials or thick metal sections to thin sheet metal skins (0.005 to 0.063 inches thick). This parameter change allows the structure to achieve sufficient strength through geometric configuration and assembly rather than material thickness, reducing production cost and assembly complexity.
2Weight of moving object
If composite layup is used for inner fixed structures, then lightweight and noise attenuation are achieved, but insulation requirements increase due to proximity to hot engine components
Solution Approach 1:
The patent uses thin sheet metal skins that can be directly exposed to hot engine environments without requiring expensive protective insulation blankets. The thin metal panels serve as both structural elements and thermal protection, eliminating the need for separate insulation layers that would be required for composite materials.
Solution Approach 2:
The patent creates a composite structure by assembling multiple thin sheet metal panels with honeycomb core assemblies, achieving both lightweight properties and thermal resistance through the layered metal construction rather than requiring thermal insulation materials.
3Shape
If metal bonding with multiple pieces is used, then complex shapes are achieved, but splice joints increase weight and reduce acoustic attenuation area
Solution Approach 1:
The patent performs preliminary stretch forming of each sheet metal panel to achieve the required complex three-dimensional shapes before assembly. By pre-forming the panels to their final shapes, the need for additional shaping operations and splice joints at assembly is minimized, reducing weight and preserving acoustic attenuation area.
Solution Approach 2:
The patent uses stretch forming over mandrels to create curved and contoured sheet metal panels that match the complex aerodynamic shapes required. This curvature achievement through forming rather than assembly eliminates the need for multiple flat panels joined by heavy splice joints.
4Ease of manufacture
If traditional forming methods are used for thin metal skins, then manufacturing is simpler, but achieving both convex and concave curvatures without additional features is difficult
Solution Approach 1:
The patent introduces dozer blocks as intermediary tools during the stretch forming process. These blocks are placed on the mandrel at specific locations to force the formation of concave curvatures in the sheet metal skin, enabling the creation of complex double-curved surfaces that would otherwise require multiple forming operations or specialized tooling.
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 process reduces production costs, simplifies assembly, maintains acoustic attenuation benefits, and decreases weight by forming complex shapes efficiently without the need for costly insulation, thus providing a more effective and time-efficient method for producing sheet metal skins for thrust reverser assemblies.
Implementation Method 1
plastically stretching a sheet of metal into a substantially convex shape about a chordwise central first axis
Implementation Method 2
plastically stretching a portion or portions of the substantially convex shape into a substantially concave shape about an axis that is substantially parallel to the chordwise central first axis
Data Source
AI summary
A method of forming sheet metal skins of the inner fixed structure of a blocker door thrust reverser assembly having convex and concave curvatures. The method includes plastically stretching a sheet of metal about a mandrel having a chordwise central first axis to form a substantially convex shape. The method further includes the addition of features after the substantially convex shape is formed to facilitate plastically stretching a portion or portions of the substantially convex shape into a substantially concave shape about an axis that is substantially parallel to the chordwise central first axis.