PSI - Issue 24

10

Pierluigi Fanelli et al. / Structural Integrity Procedia 00 (2019) 000–000

Pierluigi Fanelli et al. / Procedia Structural Integrity 24 (2019) 949–960

958

⎡ ⎢⎢⎢⎢⎢⎢ ⎢⎢⎢⎢⎢⎢⎢⎢⎢ ⎢⎢⎢⎢⎢⎢⎢⎢⎢ ⎢⎢⎢⎢⎢⎢⎢⎢⎢ ⎣

⎤ ⎥⎥⎥⎥⎥⎥ ⎥⎥⎥⎥⎥⎥⎥⎥⎥ ⎥⎥⎥⎥⎥⎥⎥⎥⎥ ⎥⎥⎥⎥⎥⎥⎥⎥⎥ ⎦

ε 1 , HS ε 1 , HM ε 1 , TW ε 1 , S H ε 1 , NO γ 2 , HS γ 2 , HM γ 2 , TW γ 2 , S H γ 2 , NO γ 3 , HS γ 3 , HM γ 3 , TW γ 3 , S H γ 3 , NO γ 4 , HS γ 4 , HM γ 4 , TW γ 4 , S H γ 4 , NO ε 5 , HS ε 5 , HM ε 5 , TW ε 5 , S H ε 5 , NO ε 6 , HS ε 6 , HM ε 6 , TW ε 6 , S H ε 6 , NO γ 7 , HS γ 7 , HM γ 7 , TW γ 7 , S H γ 7 , NO γ 8 , HS γ 8 , HM γ 8 , TW γ 8 , S H γ 8 , NO

(5)

χ =

6.2. Second part - Measurements and reconstruction on CUV 40’ hull

The testing phase, which has been taken place at ”Cantieri del Mediterraneo” shipyards in Naples, consisted of towing tests, in which CUV 40’ hull has been trailed by another ship, with the aim of simulating an axial load on the hull itself. During the tests, the velocity has been maintained on a constant value of about 10 knots; referring to the sailing conditions, they can be considered of calm sea, both because of the closeness of the test area to the shipyard and for the absence of wind during the test day. Two tests have been performed; a 5 s sampling interval has been chosen, with the aim of acquire in constant speed conditions. Strain data have been acquired under a 2.5 kHz sampling frequency; the collected data have been lately processed through the above described reconstruction algorithm and the output data compared with reference ones. 6.2.1. Normal force The first part of the analysis concerns the reconstructed value of the normal force acting on the ship hull and its comparison with a reference value, obtained from shipbuilding standards. In particular, the N-force standard value calculation has been obtained by referring to the resistance (which consists of viscous resistance and wave resistance) related to 10 knots towing; the obtained value, with both the ITTC and DNV rules, is of 5 kN.

LQ`K H 6Q`+2

LQ`K H 6Q`+2

10 − 2

10 − 2

1 . 2 ·

1 . 2 ·

_272`2M+2 o Hm2 _2+QMbi`m+i2/ o Hm2 _2+QMbi`m+i2/ J2 M o Hm2

_272`2M+2 o Hm2 _2+QMbi`m+i2/ o Hm2 _2+QMbi`m+i2/ J2 M o Hm2

1

1

0 . 8

0 . 8

0 . 6

0 . 6

0 . 4

0 . 4

L (JL)

L (JL)

0 . 2

0 . 2

0

0

0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5 4 4 . 5 5 − 0 . 2

0 0 . 5 1 1 . 5 2 2 . 5 3 3 . 5 4 4 . 5 5 − 0 . 2

hBK2 (b)

hBK2 (b)

Fig. 9. Normal force reconstructed and reference values comparison (a) First test; (b) Second test.

Fig.9 resumes the obtained results. As it can be seen, the mean reconstructed value of the normal force is compa rable to the reference one. The latter is only an approximated esteem of the actual loads as a result of a simplified model corrected by equivalent coe ffi cients interpreting ideal conditions. The result is even more appreciable taking