In this experimental setup a NiTinol wire of 0.5mm diameter is stretched and it’s both ends are fixed at vertical column equidistant from the cantilever beam such that if passes through the later. NiTinol wire is to be stretched to make a strain 2% of its length by using cable adjusting screws in the vertical column. The Shaker is fixed in a free end of a cantilever beam which acts as a vibrating source and vibration sensors(accelerometer) attached the in the cantilever beam which senses the vibration and generate respective electrical signal which are fed to CPU through PCI6201 DAQ. By analysisng the signal the natural frequency and modes can be determined.
By supplying required current, the temperature of NiTinol wire is increased uniformly to induced martensite phase transformation. Due to the phase transformation, NiTinol wire generates retaining force to regain back its initial position. When the retaining force acts on cantilever beam structure, stiffness of the cantilever beam structure increased. Hence the vibration of the cantilever can be controlled by supplying required current to Shape memory alloy wire.
- Cantilever beam
- Cantilever beam (500 x 25 x 3) mm
- Load cell – 10N
- Shape Memory Alloy wire (0.5 mm)
- Superelastic spring (0.5 mm)
INTRODUCTION TO LabVIEW
LabVIEW is a graphical programming language that uses icons instead of lines of text to create applications. In contrast to text-based programming languages, where instructions determine program execution, LabVIEW uses dataflow programming, where the flow of data determines execution.
In LabVIEW, you build a user interface with a set of tools and objects. The user interface is known as the front panel. You then add code using graphical representations of functions to control the front panel objects. The block diagram contains this code. In some ways, the block diagram resembles a flowchart.
You can purchase several add-on software toolsets for developing specialized applications. All the toolsets integrate seamlessly in LabVIEW.
INTRODUCTION TO VIRTUAL INSTRUMENTS
Lab VIEW programs are called virtual instruments, or VIs, because their appearance and operation imitate physical instruments, such as oscilloscopes and multimeters. Every VI uses functions that manipulate input from the user interface or other sources and display that information or move it to other files or other computers.
A VI contains the following three components:
- Front panel—Serves as the user interface.
- Block diagram—Contains the graphical source code that defines the functionality of the VI.
- Icon and connector pane—Identifies the VI so that you can use the VI in another VI. A VI within another VI is called a subVI. A subVI corresponds to a subroutine in text-based programming languages.
BLOCK DIAGRAM REPRESENTATION AND DESCRIPTION
The outputs from the sensors (ACCELEROMETER and THERMOCOUPLE 1& 2) are given to the DATA CARD (PCI6201) and the output of data card is compared with the set value, if its greater than the set value it is given to the PID controller with the temperature sensed by the thermocouple in wire. The current is supplied as per the increase of vibration in the cantilever beam to produce a retaining force in SMA to control the oscillation of the cantilever beam.
EXPERIMENTAL SETUP ON VIBRATION TESTING
The simple arrangement of cantilever beam has been made with a vibration source. The SMA wire was stretched to make a strain 2% (6.5mm)of its length.
The shape memory alloy wire of 0.5mm is connected to the ends of the beam as shown in the experimental arrangement, and once again the beam is subjected to vibration
The vibration signals of simple cantilever beam has been captured with the help of accelerometer and fed to control system and analyzed via LABVIEW software.
A theoretical calculation was formulated for the cantilever beam and in natural frequency was calculated.
Finite Element Analysis was carried out and its natural frequencies at various condition are obtained
From the experimental result it is to be concluded that the vibration of cantilever beam is controlled by 20% by using shape memory effect.
Hence from this work it is concluded that shape memory alloy wire (NiTinol) have good damping characterisitic against vibrations which can be used for controlling the vibration in various machine tools.