PSI - Issue 2_B

G. La Rosa et al. / Procedia Structural Integrity 2 (2016) 2140–2147 G. La Rosa et al./ Structural Integrity Procedia 00 (2016) 000 – 000

2144

5

296,2 296,4 296,6 296,8 297 297,2 297,4 297,6 297,8

0 0,2 0,4 0,6 0,8 1 1,2 1,4 1,6

Load [kN]

Temperature [K]

Time [s]

0

50

100

150

200

250

P 1d Load Fig. 4. Comparison of the static and dynamic thermal differences for the specimen with 5.5 mm hole. P 1s

The differences in evaluating the yield point among the curves using the static or dynamic procedure can be estimated by the thermoelastic equation, expressed for plane stress as: = − 0 0 ( + ) (1) Then ( + ) = = − 0 0 (2) The thermoelastic constant K 0 can be calculated for PVC by the traditional formula: 0 = = 3.62 x 10 -5 MPa -1 (3) where the thermodynamic parameter can be deducted by the values presented in Table 3.

Table 3. PVC physical, mechanical and thermal properties Density (at 23 o C)

1.32 – 1.54 5 – 8 x 10 -5 0.13 – 0.18

kg/dm 3

 

Coefficient of linear thermal expansion

K -1

Thermal conductivity

C c p

W/m·K kJ/kg·K Shore D

0.9 – 1.3

Specific heat at constant pressure

Rockwell hardness Modulus of elasticity

HR

65 - 85

E

MPa

3000

At each time t, the ratio of the sum of the main stresses depends only on the ratio of the respective changes in temperature because the thermoelastic constant and the room temperature are the same for both points, and then: 1 1 = 1 1 (4) Table 4 shows the percent errors in elastic and plastic phases between the two evaluations, static and dynamic, in terms of average (e% ave ) and maximum (e% max ) errors, calculated as: e% = 1 − 1 1 x 100 (5)