SMA Tension Member Active Damping via Frequency Modulation

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Solution Overview

Problem

Tension members such as ropes and cables experience resonance due to external forces like wind, leading to catastrophic oscillations, as existing damping mechanisms are inadequate to control resonance effectively, resulting in damage to structures like the World Trade Center and bridges.

Innovation Solution

Incorporating shape memory alloys (SMAs) into tension members, which can change their natural frequency through phase transitions induced by heating, using induction or resistance heating methods controlled by PID controllers to prevent resonance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If shape memory alloys are used to actively dampen oscillations by changing natural frequency, then resonance control is improved, but device complexity increases

Engineering Contradiction:

Improveresonance controlVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent changes the natural frequency parameter of the tension member by inducing phase transitions in the shape memory alloy core through heating, thereby altering the stiffness and damping characteristics of the member to prevent resonance

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent utilizes phase transitions in shape memory alloys (austenite-martensite transformation) to actively modify the mechanical properties of the tension member, enabling dynamic adjustment of natural frequency and damping ratio to control oscillations

Inventive Principle:

Principle #36Phase transitions

2Adaptability or versatility

If heating methods are used to induce phase transitions in SMAs, then natural frequency adjustment is improved, but energy consumption increases

Engineering Contradiction:

Improvenatural frequency adjustmentVSAvoidenergy consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The patent applies periodic or pulsed heating to the shape memory alloy core rather than continuous heating, inducing phase transitions only when needed to adjust natural frequency and dampen oscillations, thereby reducing overall energy consumption

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The patent replaces traditional mechanical damping mechanisms with a thermal-field-based phase transition mechanism in shape memory alloys, allowing for more efficient and controllable energy usage through electrical or induction heating

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 SMA-based tension members effectively dampen oscillations by altering their natural frequency, preventing destructive resonance and enhancing structural stability.

Implementation Method 1

shape memory alloys (SMAs) into tension members, which can change their natural frequency through phase transitions induced by heating

Methodology Applied

Scientific EffectPhase transition: Phase Change

Implementation Method 2

using induction or resistance heating methods controlled by PID controllers

Methodology Applied

Scientific EffectInduction heating: Induction Heating

Implementation Method 3

using induction or resistance heating methods controlled by PID controllers

Methodology Applied

Scientific EffectResistance heating: Joule Heating

Data Source

PatentUS8617325B2Actively damped tension member

Publication Date: 2013.12.31 THYSSENKRUPP ELEVATOR CORPORATION

AI summary

A system and method for actively damping tension members modulates the natural frequency of shape memory alloys incorporated into tension members, such as suspension ropes or cables. The frequency of the tension member can be modulated by heating the shape memory alloy, such modulation preventing potentially destructive resonance with natural exciting forces.