Reference no: EM133005145

Question 1). For a 30 wt% Sn-70 wt% Pb alloy at 250 oC shown in Figure 1, answer the questions below:
(a) What phase(s) is (are) present?
(b) At what temperature does the first liquid phase form?
(c) What is (are) the composition(s) of the phase(s)?
(d) What is the weight fraction of the phase(s)?

Figure 1.

Question 2). Figure 2 shows a shape memory alloy (SMA) spring system where the spring is required to provide a constant force of 7N giving a stroke length of 15 mm. Assume that the spring index c is 5 and the maximum shear stress τc, of the SMA spring is 110 MPa. The low temperature (<Ms temperature) shear strain is limited to 0.010. The shear moduli of the SMA spring at temperatures Mf and Af are 3700 MPa and 25400 MPa, respectively. The spring constants KH and KL of the SMA spring at high temperature (Af) and low temperature (Mf) are respectively given as 1.381 N/mm and 0.152 N/mm.

(a) Determine the wire diameter, average diameter and active turns of the SMA spring.

(b) Determine the reset force required for SMA spring system at low temperature.

Figure 2.

Question 3. Figure 3 shows how a clogged artery is expanded to allow blood to pass. Suggest a SMA is used. Briefly explain the working principle of this advanced material in this application.

Figure 3.