Скачать или смотреть Magic metal springs to life from heat! But how??

Nickel Titanium alloy, commonly referred to as Nitinol, exhibits a distinctive characteristic known as the shape memory effect. To induce this effect, nitinol is initially heated to temperatures exceeding 500 degrees Celsius (932 degrees Fahrenheit) while maintained in a predetermined shape. Precise temperature control, timing, and quenching are essential for achieving an effective shape memory effect. Once properly trained, nitinol can be deformed into any desired shape at room temperature. Subsequently, upon heating above a specific temperature (in this case, close to the boiling point of water), it undergoes a spring-back to the shape it was originally trained to retain. In this demonstration, two nitinol-based objects, pre-trained to adopt two distinct shapes, are showcased. When heated, the nitinol wire is trained to extend straight, while the nitinol spring is trained to return to its initial spring-like shape. The underlying physics behind the shape memory effect is attributed to a phase transformation within the crystal structure, transitioning between the Martensite and Austenite states.

To construct a nitinol based heat engine, we utilize a 0.5mm thick nitinol wire that has been pre-trained to maintain a straight orientation when heated above 80 degrees Celsius. This wire is soldered at its ends to form a loop that encircles wheels with varying radii, as depicted in the video. When the lower (and smaller) wheel is partially immersed in hot water exceeding 80 degrees Celsius, the portion of the wire that encircles the wheel attempts to align itself in a straight line, resulting in a tension. The torques exerted on the wheel on two sides by the wire are inevitably unbalanced due to various factors, including imperfect even contact with hot water and the wheel not being perfectly circular, among others. This eventually leads to the wheels rotating in a specific direction. Alternatively, it is possible to direct the rotation of the system by submerging the lower wheel in hot water at an angle.

This demo was built and presented by a Texas A&M University ‪@tamu‬ student in #TAMUDEEP program.

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