COBEM99

S5 Controle Ativo de Vibrações e Estruturas Inteligentes

Title:

COMPARISON BETWEEN THE ELECTRICAL AND THERMAL RESPONSES OF ACTUATOR WIRES WITH SHAPE MEMORY EFFECT

Summary :

ABSTRACT. WIRES FABRICATED WITH SHAPE MEMORY ALLOYS PRESENTS AN IMPORTANT POTENTIAL FOR APPLICATIONS IN INTELLIGENT AND/OR ADAPTABLE SYSTEMS AND ROBOTIC DEVICES. IN THESE CASES, THE DISPLACEMENT BY SHAPE MEMORY EFFECT (SME) CAN BE OBTAINED BY ELECTRICAL (JOULE EFFECT) OR THERMAL ACTUATION (FORCED CONVECTION, FOR EXAMPLE). THIS PAPER IS ESPECIALLY DEDICATED TO A COMPARATIVE ANALYSIS OF THE PERFORMANCES OF THESE TWO ACTUATION MODES WHICH ARE ALTERNATIVELY APPLIED ON A SAME ACTUATOR WIRE, FOR DIFFERENT VALUES OF TENSILE LOADS. A SIMPLE ELECTRO-THERMAL ACTUATOR FORMED ESSENTIALLY OF TI-NI-CU WIRES LOADED IN UNIAXIAL TENSION BY WEIGHTS WAS DESIGNED. THE OBTAINED RESULTS SHOW THAT, FOR ALL EXTERNAL LOAD LEVELS, THE DISPLACEMENT BY SME IS MORE LARGE WHEN THE HEATING OF THE WIRE IS PERFORMED BY FORCED CONVECTION INTO A LIQUID ENVIRONMENT IN COMPARISON WITH THE DISPLACEMENT MEASURED DURING ELECTRICAL HEATING. IN FACT, FOR EXTERNAL LOADS BETWEEN 75MPA AND 400MPA, THE SME UNDER LOAD OBTAINED BY JOULE EFFECT IS BETWEEN 70% AND 90% OF THE ONE MEASURED BY FORCED CONVECTION. THESE RESULTS ARE DISCUSSED IN TERMS OF THE HEAT TRANSFER DIFFERENCES BETWEEN THE TWO ACTUATION MODES AND THE PHYSICAL ASPECTS RELATED TO THE MARTENSITIC TRANSFORMATION ASSOCIATED TO THE SME PHENOMENON. KEYWORDS: WIRES, SHAPE MEMORY EFFECT, ACTUATORS.

Author :

de Araujo, Carlos Jose
Morin, Michel 0

Paper View :