On-Axis Shear Hinge for Controlled Detachment at a Set Angle
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Solution Overview
Problem
Existing hinges for aerodynamic bodies, such as missiles and drones, face reliability issues due to thermal heating, corrosion, and manufacturing tolerances in asymmetric ball and socket configurations, and external stoppage elements can cause breakage in critical flow paths, affecting airflow and increasing the size of the detachable hinge, which complicates the outer mold line (OML) of the aerodynamic body.
Innovation Solution
An on-axis hinge design with internal stopping mechanisms that shear and break at a predetermined angle using a torsional load applied to a weakened region, minimizing the impact on the aerodynamic body's OML and reducing Foreign Object Debris (FOD) risks by integrating the stopping features and load transfer interfaces within the hinge's compact footprint.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If external stoppage elements are used to limit rotation angle, then the hinge can achieve controlled detachment, but the effective size of the hinge increases and affects the outer mold line of the aerodynamic body
Solution Approach 1:
The stopping mechanism is nested within the hinge structure itself. The stop feature is formed as an integral part of the hinge body, with a complementary stop feature positioned within the hinge's internal geometry. This eliminates the need for external stoppage elements and reduces the overall hinge footprint while maintaining controlled detachment functionality.
Solution Approach 2:
The stopping mechanism utilizes the axial dimension of the hinge rather than requiring external radial or lateral elements. By positioning the stop feature along the hinge's rotation axis and using axial engagement between complementary features, the design achieves angle limitation without increasing the hinge's external dimensions.
2Reliability
If external stoppage elements are used to limit rotation angle, then the hinge can achieve controlled detachment, but the breakage point is placed in the primary flow path creating FOD risk
Solution Approach 1:
The stopping and detachment mechanism is extracted from the external flow path and repositioned within the hinge's internal structure. The breakage occurs at an on-axis weakened region that is shielded by the hinge plates and structural components, removing the detachment debris from the primary aerodynamic flow path and eliminating FOD risk to downstream components.
Solution Approach 2:
The hinge structure itself acts as an intermediary that contains and controls the detachment process. The weakened region is positioned such that the hinge plates and other structural elements serve as barriers between the breakage point and the external flow path, preventing debris from entering the aerodynamic stream.
3Stability of the object's composition
If asymmetric ball and socket configuration is used, then the hinge can achieve limited rotation, but reliability issues occur due to thermal heating, corrosion, or manufacturing tolerances
Solution Approach 1:
The hinge utilizes a symmetric on-axis configuration rather than an asymmetric ball and socket design. This symmetric geometry eliminates the stress concentrations and manufacturing tolerance sensitivities associated with asymmetric configurations. The load is distributed evenly along the on-axis member, improving reliability under thermal and corrosive conditions.
Solution Approach 2:
The hinge employs material property variations within the on-axis member to achieve both structural integrity and controlled detachment. The member includes a full diameter region with high strength for load bearing and a weakened region with reduced cross-section or altered material properties for predictable failure. This composite structure approach ensures reliability while enabling controlled detachment.
4Volume of moving object
If the hinge is designed with on-axis stopping mechanisms, then the impact on OML is minimized, but the hinge requires internal integration of stopping features and load transfer interfaces
Solution Approach 1:
The stopping features and load transfer interfaces are merged into the hinge structure as integral components rather than separate assemblies. The on-axis member includes both the load-bearing function and the stopping mechanism within a single integrated component, eliminating the need for additional internal parts and reducing overall complexity despite the compact design.
Solution Approach 2:
The on-axis member serves multiple functions simultaneously: it acts as the rotation axis, provides the stopping mechanism through its geometric features, and functions as the load transfer element. This multi-functionality reduces the number of separate components needed and simplifies the internal structure while achieving the compact on-axis configuration.
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 on-axis hinge design ensures reliable and controlled detachment of covers with minimal impact on the aerodynamic body's OML, reducing thermal effects and FOD risks while allowing precise load tailoring for detachment, maintaining aerodynamic efficiency and reducing the risk of damage to critical components.
Implementation Method 1
The complementary stopping feature is configured in the thru hole to engage the on-axis member's stopping feature at a predetermined angle of rotation to produce a torsional load on the on-axis member that creates torsional shear of the on-axis member at the weakened region
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
A hinge includes internal on-axis stopping mechanisms that cause the hinge to shear and break at an on-axis weakened region of the hinge when rotation of the hinge reaches a predetermined angle with a specified torsional load. The on-axis configuration is compact, has minimal impact on the outer mold line (OML) of the object to which it is mounted both pre and post detachment and allows for accurate tailoring of the torsional load that will detach the hinge.