On the Transient Transverse Strength of a Torpedo Boat during Slamming

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It seems to the authors not being well discussed yet on the transverse strength of a torpedo boat during slamming which is on the transient state of forced vibration. In order to get an estimation of the transient transverse strength and to get the data of determining the method of its calculation suitable to actual data, the sea tests of a torpedo boat were carried out in rough seas. In this paper, although data obtained from tests are all presented for discussion, those of transverse stresses are discussed in detail especially. Finally, the damage of bottom shell panels is briefly discussed. In the first chapter are explained the outline of the sea tests which contains three items such as (1) general statements, (2) trial schedule and (3) test installation; in the second chapter, results obtained after analysing data such as (1) wave heights and wave lengths, (2) period encountered with waves, (3) ship bending due to wave during slamming and (4) maximum and minimum of recorded values; in the third chapter, the transient transverse stress distribution, the distribution of stress repetitions, and the damage of bottom shell panels. Among the results above obtained, the important results and phenomena concerning to the transient transverse stresses and damages are as follows: (1) In the case of head seas the relation between the accompanying bottom pressure and stress that occurs upon slamming has same tendencies of qualitative characteristics throughout all cases of different speed. Non-linearity, however, exists between the pressure and stress at each stage of boat's speed. One reason of those phenomena is that the position of the maximum pressures and their distribution are always changing from time to time. The another reason is due to the cause which the recorded stresses in certain side frames and bottom floors are the sum superimposed upon the direct stresses the indirect stresses induced by the transmission of the another transverse response due to water pressure through the hull girders and longitudinals. (2) In the case of following seas, the water pressure is generally low and always less than those in heading at each speed. It yields that the direct effect of pressure on the transverse stress in this case will not exist, but the hull girder response should be first taken into consideration, and the effect of bottom pressure becomes secondary and rather minor. (3) Corresponding to the increase of speed, the magnitudes of stress in both heading and following seas spread gradually to higher values further than lower values. And the peak of numbers of stress repetitions in head seas shift almost from the small to the large value of stress, but it doesn't in following seas. (4) From the permanent deformations developed in initially flat bottom panels after tests, the quantitative relation between the numbers of stress or load cycles and developed permanent sets of bottom shell plates is obtained, by which necessary informations of the solution to a bottom shell plate due to repetitive slam loads are given.
社団法人日本船舶海洋工学会の論文
1966-02-28

On the Transient Transverse Strength of a Torpedo Boat during Slamming

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