Pseudoelastic Multi-Flexure Payload Isolation for Shock Loads
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Solution Overview
Problem
Current multi-axis flexures and rotational isolators used in sensor mounts and other payloads fail frequently due to high rotational stiffness and reduced tensile strength when scaled up, leading to increased costs and downtime, as they are unable to effectively absorb and mitigate vibrations and impact loads without failure.
Innovation Solution
The use of pseudoelastic shape-memory alloy radial supports in a multi-axis payload isolation device, which provides improved rotational isolation and shock absorption by allowing temporary stretching under impact loads while maintaining sufficient tensile strength for translational positioning, utilizing a configuration with frustoconical flexures and anchoring rings to support the payload.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the size of a flexure is increased to support larger payloads, then the load-bearing capacity increases, but the rotational stiffness increases by approximately a power of three or four while tensile strength only increases by approximately a power of two
Solution Approach 1:
The patent applies parameter changes by utilizing pseudoelastic shape-memory alloy material properties to fundamentally alter the mechanical behavior of the flexure. This material enables the flexure to exhibit nonlinear stress-strain characteristics with plateau regions that provide constant force over displacement ranges, effectively decoupling the scaling relationships between strength and rotational stiffness that plague traditional materials. The pseudoelastic behavior allows the flexure to maintain low rotational stiffness while supporting increased payload weights through material-level property optimization rather than geometric scaling.
Solution Approach 2:
The patent employs composite materials by combining pseudoelastic shape-memory alloy with traditional structural materials in the flexure design. This composite approach leverages the unique properties of shape-memory alloys—their ability to undergo large reversible deformations and exhibit force plateaus—while integrating them with conventional materials to achieve the desired combination of high tensile strength and low rotational stiffness. The composite structure enables simultaneous optimization of multiple mechanical properties that are traditionally mutually exclusive.
2Strength
If the size of a flexure is increased, then the load-bearing capacity increases, but the system mass increases approximately with the power of three
Solution Approach 1:
The patent utilizes parameter changes through pseudoelastic material properties to achieve high load-bearing capacity without proportional increases in mass. The force plateau behavior of pseudoelastic materials allows the flexure to support large loads during impact events while maintaining a compact, lightweight structure. This material-level parameter optimization enables the system to achieve superior strength-to-weight ratio compared to traditional flexure designs that would require geometric scaling and consequently cubic mass increases.
3Reliability
If traditional flexures are used to isolate sensors from vibrations and impact loads, then rotational isolation is provided, but the flexures fail semi-regularly under high impact loads
Solution Approach 1:
The patent applies parameter changes by exploiting the pseudoelastic stress-strain curve characteristics, particularly the plateau regions where material transformation occurs. During impact events, the flexure enters these plateau regions where it can undergo large deformations while maintaining relatively constant force levels, effectively absorbing impact energy without structural failure. This material behavior fundamentally changes how the flexure responds to harmful impact loads, transforming from a brittle failure mode to a energy-absorbing, self-healing response that dramatically improves reliability.
Solution Approach 2:
The patent converts the harmful impact loads into beneficial energy absorption through the pseudoelastic material response. The impact energy that would traditionally cause failure is instead utilized to drive the material through its stress plateau regions, where reversible phase transformation absorbs the energy. This transforms the harmful factor (impact load) into a beneficial effect (energy dissipation through reversible deformation), enabling the flexure to withstand and mitigate vibrations and impact loads without failure.
4Measurement precision
If multi-axis flexures are designed with high translational stiffness for positioning, then positioning accuracy is maintained, but rotational flexibility is reduced leading to failure under impact
Solution Approach 1:
The patent applies parameter changes through the nonlinear pseudoelastic stress-strain behavior to achieve decoupled stiffness characteristics. The force plateau regions in the stress-strain curve enable the flexure to provide high effective stiffness in translational directions for positioning accuracy while simultaneously allowing large rotational excursions during impact events. This nonlinear material behavior allows the flexure to adapt its effective stiffness based on the type and magnitude of loading, maintaining positioning accuracy during normal operation while providing rotational flexibility under impact conditions.
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 solution significantly reduces the failure rate of flexure mounts by offering enhanced rotational flexibility and translational stiffness, allowing for effective absorption of shock loads and vibrations without permanent deformation, thereby improving the reliability and longevity of sensor mounts and other payloads.
Implementation Method 1
a first plurality of radial supports made of a pseudoelastic shape-memory alloy anchored to the housing and configured to support the payload from the housing through a first opening in the housing
Implementation Method 2
allowing temporary stretching under impact loads while maintaining sufficient tensile strength for translational positioning
Data Source
AI summary
A multi-flexure payload isolation device for isolating a payload from outside forces. The device can include a housing comprising an interior cavity configured to receive and support the payload. The device can further include a first flexure and a second flexure, each including a plurality of spokes made of a pseudoelastic shape-memory alloy anchored to the housing and configured to support the payload from the housing through an opening in the housing. The first and second flexures can each further include a common hub attached to a side of the payload and disposed in the opening in the housing wherein the each of the pluralities of spokes are anchored to the respective common hub.