Open Stent Design

Page 51

3.3. MATERIAL PROPERTY INPUTS

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EAf,high is the elastic modulus of the austenite phase having an Af temperature of Afhigh . EAf,high = 34, 000 MPa

(3.17)

Afhigh is the second Af temperature at which the austenite elastic modulus is defined. Afhigh = 37◦ C

(3.18)

Afinf lection is the temperature at which the Af vs E relationship transitions from the low temperature curve to the high temperature curve, as shown in Figure 3.3. Afinf lection = 19◦ C

(3.19)

The calculated value of E, the austenite elastic modulus for a material having the specified Af , depends on the Af temperature. For Af less than Aflow :

Ecase1 = EAf,low

(3.20)

For Af between Aflow and Afinf lection , the green curve of Figure 3.3 applies:

Ecase2 = EAf,low − 1.9 · (Af − Aflow )3

(3.21)

For Af between Afinf lection and Afhigh , the orange curve of Figure 3.3 applies:

Ecase3 = EAf,high + 5.9 · (Afhigh − Af )3

(3.22)

For Af equal to or above Afhigh :

Ecase4 = EAf,high

(3.23)

In this example, with Af = 27, Ecase3 applies. E = Ecase3 for Af = 27◦ C E = 34059 MPa

(3.24)


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