Large-stroke and high-strength actuator materials for adaptive structures

Kari Ullakko

doi:10.1117/12.237169

26 April 1996 Large-stroke and high-strength actuator materials for adaptive structures

Kari Ullakko

Proceedings Volume 2779, 3rd International Conference on Intelligent Materials and 3rd European Conference on Smart Structures and Materials; (1996) https://doi.org/10.1117/12.237169
Event: 3rd International Conference on Intelligent Materials, 1996, Lyon, France

Abstract

The most important actuator materials in adaptive structures are shape memory alloys, piezoelectric and magnetostrictive materials and electrorheological fluids. However, no such material is available which would produce rapid and large strokes with high forces. Shape memory alloys exhibit large strokes and forces but their response is slow. Piezoelectric materials and magnetostrictive intermetallics are rapid, but the strokes are small. In the present study, employment of magnetic control of shape memory effect as a principle for rapid large stroke actuator materials is discussed. In such materials, detwinning is controlled by an external magnetic field. Twins in favorable orientation to the magnetic field grow at the expense of other twins and cause a shape change of the actuator. Strokes can be as high as those in shape memory alloys, but response times are short due to magnetic control. Another method which may be applied in actuators is inducing the martensitic transformation and controlling the growth of the martensite plates by magnetostrictive distortions of giant magnetostrictive particles embedded in the shape memory alloy matrix. Magnetostrictive inclusions can also be used as stress sensors in shape memory materials. In pre-stressing and fastening applications, materials which exhibit large strokes and high recovery stresses are required. Nitrogen alloyed shape memory steels, developed for actuators for those applications, is the second topic of this study. In nitrogen alloyed shape memory steels, yield strengths over 1100 MPa and tensile strengths even 1600 MPa were attained. Recoverable strains can be over 4% and recovery stresses 330 MPa. Stresses over 700 MPa were achieved in fasteners at room temperature. Nitrogen alloyed shape memory steels possess good corrosion properties, machinability and weldability (even the welds exhibit shape memory effect). They are economical to manufacture and use and they are expected to have applications in many fields of engineering.

Citation Download Citation

Kari Ullakko "Large-stroke and high-strength actuator materials for adaptive structures", Proc. SPIE 2779, 3rd International Conference on Intelligent Materials and 3rd European Conference on Smart Structures and Materials, (26 April 1996); https://doi.org/10.1117/12.237169

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available