Shape Memory Alloy Active Spars for Rotor Blade Twist

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Solution Overview

Problem

Existing structural spars in aircraft wings and rotor blades require complex and weight-additive mechanical or electrical actuation systems to change shape, which is inefficient and undesirable.

Innovation Solution

The use of shape memory alloy strips with a temperature control system to twist or bend structural spars, allowing for shape change without the need for complex actuation systems, by exploiting the thermal and mechanical properties of shape memory alloys to transition between martensite and austenite phases.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If mechanical or electrical actuation systems are used to change the shape of structural spars, then the shape can be changed, but the system becomes complex, takes up space and adds weight

Engineering Contradiction:

Improveshape of structural sparVSAvoidcomplexity of actuation system

Core Design Contradiction:

ShapeVSDevice complexity

Solution Approach 1:

The patent replaces complex mechanical or electrical actuation systems with shape memory alloy strips that change shape in response to temperature changes. The SMA strips are integrated into the spar structure itself, eliminating the need for separate actuation mechanisms. When heated, the SMA strips transform from martensite to austenite phase, causing the spar to twist or bend, thereby achieving shape change without complex mechanical systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The invention changes the physical state of the shape memory alloy material by varying temperature. By heating the SMA strips above their transformation temperature, the material transitions between martensite and austenite phases, which directly changes the shape of the structural spar. This parameter-based control (temperature) replaces complex mechanical control systems.

Inventive Principle:

Principle #35Parameter changes

2Shape

If mechanical or electrical actuation systems are used to change the shape of structural spars, then the shape can be changed, but weight increases

Engineering Contradiction:

Improveshape of structural sparVSAvoidweight of actuation system

Core Design Contradiction:

ShapeVSWeight of moving object

Solution Approach 1:

The shape memory alloy strips are merged with the structural spar itself, forming an integrated active structure. The SMA strips are positioned within or alongside the spar flanges, combining the structural function with the actuation function. This eliminates the need for separate, weight-additive actuation systems while maintaining the ability to change the spar's shape for aerodynamic optimization.

Inventive Principle:

Principle #5Merging (Combining)

3Shape

If shape memory alloy strips are heated to change the shape of structural spars, then aerodynamic optimization is achieved, but energy is consumed

Engineering Contradiction:

Improveaerodynamic shape of sparVSAvoidenergy for heating SMA strips

Core Design Contradiction:

ShapeVSUse of energy by moving object

Solution Approach 1:

The shape memory alloy strips are heated periodically or intermittently rather than continuously, corresponding to when aerodynamic shape changes are needed. The SMA strips can be heated to trigger phase transformation, hold the shape, and then cooled to return to original configuration, enabling periodic aerodynamic optimization without continuous energy input. This on-demand heating reduces overall energy consumption compared to continuous actuation systems.

Inventive Principle:

Principle #19Periodic action

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

This solution enhances the performance and endurance of spars by enabling aerodynamic optimization and cost savings through shape manipulation, such as twisting rotor blades for improved lift capacity and fuel efficiency.

Implementation Method 1

Shape memory alloys can exist in one of several distinct temperature-dependent phases. The most commonly utilized of these phases are the so-called martensite and austenite phases. Upon heating a shape memory alloy through a transformation temperature, the shape memory alloy changes from the martensite phase into the austenite phase.

Methodology Applied

Scientific EffectShape memory alloy phase transformation: Shape Memory Alloy

Implementation Method 2

The rate of return to the original shape depends upon the amount and rate of thermal energy applied to the component.

Methodology Applied

Scientific EffectThermal energy transformation: Thermal Energy Storage

Implementation Method 3

at least one heating element positioned each of said shape memory alloy strips to change a temperature of said shape memory alloy strips

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Data Source

PatentEP3636541B1Shape memory alloy active spars for blade twist

Publication Date: 2023.07.05 THE BOEING CO

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AI summary

A system for changing a shape a structural spar (44) includes, in an exemplary embodiment, a plurality of adjoining structural strips (52, 54) axially aligned to form the structural spar (44). At least one of the structural strips (52, 54) is formed from a shape memory alloy. The system also includes a temperature control system (56) to control a temperature of the at least one shape memory alloy strip (54). Heat applied to the at least one shape memory alloy strip (54) causes the structural spar (44) to twist or bend.