Pyramidal Frustum Core Sandwich Structures Deep Drawing
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Solution Overview
Problem
Formed core sandwich structures used in engines face challenges with thinning and fracturing under large tensile forces during formation, limiting the depth to which core materials can be drawn and affecting their ability to withstand extreme temperatures and vibrations.
Innovation Solution
The use of pyramidal frustum bases with convex regular polygon nodes and cylindrical transition regions reduces stress and allows deeper depths of draw by distributing tensile forces and minimizing contact with the die, enabling the formation of regions of negative Gaussian curvature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If conventional forming techniques are used to form core sheets, then the desired core shapes can be achieved, but the core sheet experiences thinning and fracturing due to large tensile forces
Solution Approach 1:
The core sheet is divided into multiple cells with pyramidal frustum bases arranged in a grid pattern. This segmentation allows the structure to distribute tensile forces across multiple discrete elements rather than concentrating stress in continuous regions, reducing the likelihood of fracture while maintaining the overall desired shape.
Solution Approach 2:
The core structure uses pyramidal frustum bases with asymmetric geometry - a square base at the bottom transitioning to a smaller square base at the top with sloped faces. This asymmetric shape creates favorable stress distribution patterns during forming, with the sloped faces redirecting tensile forces away from critical thin regions, thereby preventing fracture while achieving the target configuration.
2Length of moving object
If the core sheet is drawn to greater depths, then the desired sandwich structure depth is achieved, but the thinning and fracturing risk increases
Solution Approach 1:
The pyramidal frustum bases incorporate curved transition regions between the square base and the apex, replacing sharp corners with smooth curved surfaces. This curvature reduces stress concentration points that would otherwise initiate fractures during deep drawing, enabling the core sheet to be drawn to greater depths while maintaining structural integrity and reliability.
Solution Approach 2:
The forming process utilizes controlled changes in material parameters (temperature, pressure, strain rate) combined with the pyramidal frustum geometry to enable deep drawing. The specific geometric parameters of the frustum bases (side lengths, face angles, transition region radii) are optimized to distribute strains evenly, allowing depths to be increased without proportionally increasing fracture risk.
3Weight of moving object
If the core material is made thinner to reduce weight, then the weight requirement is met, but the structure becomes more susceptible to failure under tensile loads
Solution Approach 1:
By segmenting the core into discrete pyramidal frustum cells, the structure achieves high strength-to-weight ratio. The segmentation creates a cellular configuration where material is distributed efficiently throughout the volume, providing both weight reduction and structural reinforcement through the geometric arrangement of cells that resist tensile loads collectively.
Solution Approach 2:
The core structure functions as a composite system combining the base material with the pyramidal frustum geometric configuration. This composite approach - integrating material properties with structural geometry - enables thin materials to achieve enhanced tensile strength through the load-distributing pyramidal cell architecture, offsetting the strength loss from reduced material thickness.
4Ease of manufacture
If conventional forming methods are used, then the forming process is simple, but the depth of draw is limited due to material failure
Solution Approach 1:
The pyramidal frustum base geometry is designed in advance with pre-calculated optimal dimensions and transition region characteristics. This preliminary design of the geometric parameters allows the forming process to proceed without complex real-time adjustments, maintaining simplicity while achieving greater depths of draw by preventing material failure through the predetermined stress-distributing structure.
Data Source
AI summary
A formed core comprising a first and second plurality of pyramidal frustum bases, the first plurality of pyramidal frustum bases extending in a first direction and the second plurality of pyramidal frustum bases extending in a second direction, and wherein each pyramidal frustum base comprises: a node comprising a convex regular polygon, the convex regular polygon comprising a plurality of sides oriented in a first plane and wherein each side of the polygon of the node of each of the first plurality of pyramidal frustum bases is parallel to a side of the polygon of the node of at least one of the second plurality of pyramidal frustum bases; a plurality of faces extending from each of the sides of the polygon of each node of the first plurality of frustum bases to a side of the polygon of each of the second plurality of frustum bases.