A comparative study of effect of the thermal treatments in the
mechanical behavior of the Ni-Ti wire with shape memory
effect
1
E. A.C. Pina1, C. A. N. Oliveira1, O. O. Araújo Filho1 S. L. Urtiga Filho1, C. H. Gonzalez1
Universidade Federal de Pernambuco, Centro de Tecnologia e Geociêcias,Departamento de
Engenharia Mecânica, Av Acadêmico Hélio Ramos, s/n, CDU, 50730 -540, Recice –PEBrazil
The shape memory alloys are used as actuators in mechanical engineering, medical area,
aerospace, because of their natural behavior known as shape memory alloys (SMA). The
SMA is known to be from the thermo-elastic martensitic transformation. The nature of
transformation is heavily dependent of the history thermo-mechanical alloy. The thermomechanical alloys answer with shape memory alloys suffers substantial changes with
variations in the chemical, metallurgical processing and thermo-mechanical cycling.
Recently the interest in their dynamic properties has been increasing due to its high damping
capacity. This potential is related to the material’s ability to absorb energy through the inner
movements of microstructure. The used wires are commercial and had been submitted to
different thermal treatments with the purpose of studying the thermo-mechanical process and
its influences in the thermo elastics properties of the form memory effect. The wire samples
had been cut in pieces, weighed and submitted to the thermal treatment at 400°C quenched in
water at 25°C.
In this work is has been carried out a comparative analysis between the damping capacity of a
Ni-Ti wire specimen with 1.27mm diameters and submitted to the thermal treatment at 400°C
for 2 hours followed by quench in water at 25ºC and shape memory springs (SMS) was
submitted to thermo-mechanical cycles in a mass-pulley-spring
Keywords: Thermal Treatments, R-phase Transformation, Ni-Ti Alloys, Damping capacity.
Work supported by CAPES and CNPq.
0,10
Spring 9 mm, 35 MPa
STT
TT 1 hour
TT 2 hours
TT4 hours
30
0,09
28
26
0,08
P2
24
0,07
20
0,06
18
Tan δ
Displacement (mm)
22
16
14
12
10
0,05
0,04
P1
0,03
8
0,02
6
4
0,01
2
0,00
0
20
30
40
50
60
70
80
90
100
110
120
Temperature (°C)
Fig.1 - Strain–temperature curves
40
50
60
70
80
90
100 110 120 130 140 150 160 170 180
Temperature (°C)
Fig. 2 – Percentage variation Tan δ
[1] K. Otsuka, C. M. Wayman, “Shape Memory Materials”, University Press, Cambridge,
(1998).
[2] Z. G. Wang, X. T. Zu, P. Fu, J. Y. Dai, W. Zhu, L. M. Wang, Two-way shape memory
effect of TiNi coil extension springs. Materials and engineering A360: 126-131 (2003).
[3] W. Cai, X. L. Lu, L. C., “Damping behavior of TiNi-based shape memory alloys”,
Materials Science and Engineering, A 394, pp. 78–82 (2005).
[4] F. M. Fernandes, “Ligas Com Memória de Forma”, Universidade Nova de Lisboa, 2006.
[email protected], Rua Prof. António Coelho, 548, apto 102, CDU, Cep 50740-020 - Recife