SHAPE MEMORY ALLOYS (SMAS) EXHIBIT A PHASE TRANSFORMATION THAT IS DRIVEN BY TEMPERATURE AND STRESS. CHANGES…

Public award description

SHAPE MEMORY ALLOYS (SMAS) EXHIBIT A PHASE TRANSFORMATION THAT IS DRIVEN BY TEMPERATURE AND STRESS. CHANGES IN THESE FIELDS CAN BE USED TO EXPLOIT BEHAVIORS SUCH AS THE SHAPE MEMORY EFFECT (SME) AND PSEUDOELASTICITY. THE MICROSTRUCTURE AND BEHAVIOR OF SMA MATERIALS ARE QUITE COMPLEX. VARIOUS CONSTITUTIVE MODELS HAVE BEEN DEVELOPED OVER THE LAST TWENTY YEARS TO SIMULATE THEIR COMPLEX BEHAVIOR FOR DESIGN OF SYSTEMS INCORPORATING SMA COMPONENTS. SMAS HAVE BEEN SUCCESSFULLY IMPLEMENTED IN BIOMEDICAL APPLICATIONS FOR MANY YEARS BECAUSE THE PSEUDOELASTIC EFFECT IS USUALLY EMPLOYED EXCLUSIVELY, THEREBY SIMPLIFYING THE SMA MATERIAL BEHAVIOR AND RESULTING MECHANICAL SYSTEM CONSIDERABLY. MODELS FOR PSEUDOELASTIC BEHAVIOR ARE CORRESPONDINGLY SIMPLER THAN COMPREHENSIVE SMA CONSTITUTIVE MODELS. CONSEQUENTLY, IMPLEMENTATIONS OF PSEUDOELASTIC MODELS CAN BE FOUND IN COMMERCIAL STRUCTURAL ANALYSIS CODES, WHICH HAVE AIDED SIGNIFICANTLY IN THE IMPLEMENTATION OF SMA MATERIALS FOR BIOMEDICAL APPLICATIONS. SMAS ALSO HAVE GREAT POTENTIAL FOR MANY OTHER APPLICATION AREAS, SUCH AS AEROSPACE, WHERE ACTUATION AND THE ACCOMPANYING SME ARE DESIRABLE. THE MATERIAL BEHAVIOR IN THESE CASES IS MUCH MORE COMPLEX AND THE APPLICATION ITSELF OFTEN INVOLVES COMPLEX STRUCTURAL SYSTEMS WITH COUPLING BETWEEN THERMAL AND MECHANICAL RESPONSES. THE SCARCITY AND DELAY IN IMPLEMENTATION OF SMAS INTO APPLICATIONS INVOLVING ACTUATION IS LARGELY DUE TO THE COMPLEXITY OF SMA BEHAVIOR AS AN ACTUATOR. A COMPREHENSIVE SMA CONSTITUTIVE MODEL IS REQUIRED FOR HIGH-FIDELITY ANALYSIS AND DESIGN INCORPORATING SUCH COMPLEX BEHAVIOR. MODELS OF THIS TYPE HAVE NOT BEEN AVAILABLE IN COMMERCIAL STRUCTURAL ANALYSIS CODES, THEREBY EXACERBATING THE SLOW APPLICATION OF SMA ACTUATION TECHNOLOGY. RECENT ADVANCES IN SMA MATERIALS SYNTHESIS AND PROCESSING ARE ENABLING NEW APPLICATIONS FOR SMA MATERIALS, E.G., AT HIGHER TEMPERATURES, WHICH IS OFTEN ACCOMPANIED BY ADDITIONAL MICROSTRUCTURAL COMPLEXITY. THIS PARALLEL EFFORT IN MATERIAL SYNTHESIS UNDERSCORES THE NEED FOR COMPREHENSIVE SMA MODELS FOR ACTUATION. THE PURPOSE OF THIS TASK ORDER IS TO EXTEND THE SELECTED MODEL TO THERMO-MECHANICALLY COUPLED POLYCRYSTALLINE ACTUATOR BEHAVIOR UNDER MULTI-AXIAL LOADING AND IMPLEMENTATION OF THE EXTENDED MODEL IN ABAQUS. THE GOAL OF THIS TASK ORDER IS TO PERFORM THE IDENTIFIED MODEL EXTENSIONS AND REFINEMENTS AND VALIDATE THE NEW MODELS AGAINST BENCHMARK EXPERIMENTAL TEST DATA. ACCORDINGLY, THE CONTRACTOR SHALL EXTEND THE EXISTING CONSTITUTIVE MODEL FOR SMA MATERIALS IN TWO PHASES AS DESCRIBED SUBSEQUENTLY.