Hollow Connecting Rod Structure for Mass Reduction and Buckling Strength
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Solution Overview
Problem
Conventional metal or solid composite connecting rods used in aeronautical engines are heavy due to their solid cross-section, which increases significantly with distance between attachment points, making them costly and inefficient in terms of mass reduction.
Innovation Solution
A hollow connecting rod design with increasing external perimeter from ends to center, maintaining a constant cross-sectional area, and decreasing wall thickness, which enhances buckling resistance and vibration frequency, while reducing mass by up to 40%, and allowing for lighter materials or reduced wall thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If solid cross-section connecting rods are used, then strength and rigidity are maintained, but mass increases significantly with distance between attachment points
Solution Approach 1:
The patent transitions from a solid cross-section to a hollow cross-section, utilizing the dimensional space within the rod. By creating a hollow interior while maintaining or increasing the external perimeter, the design redistributes material to the outer regions where it provides maximum bending and buckling resistance, thereby reducing mass without compromising strength.
Solution Approach 2:
The patent applies varying wall thickness along the length of the connecting rod, with thicker walls at the ends and thinner walls toward the center. This local differentiation optimizes material distribution: thicker sections provide strength where loads are applied, while thinner sections reduce mass in regions experiencing lower stresses, resolving the contradiction between overall strength and total mass.
2Weight of moving object
If wall thickness is reduced to decrease mass, then mass reduction is achieved, but buckling resistance and structural integrity are degraded
Solution Approach 1:
By switching to a hollow cross-section with increased external perimeter, the patent compensates for reduced wall thickness. The larger outer dimensions provide greater moment of inertia and buckling resistance despite the thinner walls, allowing mass reduction without sacrificing structural integrity.
Solution Approach 2:
The varying wall thickness distribution (thicker at ends, thinner at center) strategically places material where it is most needed for buckling resistance. The thicker end sections maintain high local stiffness and strength, while the thinner central sections reduce overall mass, effectively resolving the contradiction between mass reduction and buckling resistance.
3Strength
If external perimeter is increased from ends to center, then buckling resistance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The patent employs a rotationally cylindrical hollow body with curved, smooth transitions in perimeter and wall thickness. This continuous curvature simplifies manufacturing compared to sharp corners or abrupt geometric changes, while still achieving the desired increasing perimeter from ends to center. The rotational symmetry also facilitates uniform material distribution and balanced mechanical properties.
Data Source
AI summary
A connecting rod includes a hollow body with a ring at each end and a centre, a thickness wall e, the wall defining an outer perimeter pe and an inner perimeter pi, a surface section s being contained between the outer and inner perimeters, wherein the outer perimeter pe increases from the ends of the hollow body to the centre of the connecting rod, the hollow body maintaining a constant surface section s, the thickness e decreasing from the end to the centre of the connecting rod.