FATIGUE ASSESSMENT OF BILGE KNUCKLEJOINT OF VLCC ACCORDING TO JTP/JBP RULES 1. DESCRIPTION OF TEST AND EXPERIMENTAL RESULTS The model was a bilge knuckle section for a double hull VLCC in approximately 1/3 scale, Ship Research Panel 245 (2001). The model was about 6m in length, 5m in width, 3.6m in height and 20tons in steel weight. To make stress distributions of the model similar to those of the actual ship, a three-floor space in the longitudinal direction was modelled. The model was fixed to a rigid wall at the double hull side, with the ship’s bottom being upside and the inner bottom being downside. The load was applied by three syncronised hydraulic jacks on the centreline of the double bottom, see Fig. 1. The model was built from mild steel in accordance with NK rules. In order to initiate cracks only at the bilge knuckle section of the centre floor, the weld leg length at the bilge knuckle section at the other floors was increased, and the weld toes were ground smooth. Fig. 1. Bilge knuckle model. The fatigue loading was constructed from a block loading simulating variable amplitude loading conditions during sea-going service. The typical mean stress alternation for a VLCC is a tensile mean stress in full load condition and a compressive mean stress in ballast condition. The applied load cycles were therefore composed of five blocks with a tensile mean stress and five similar block with a compressive mean stress. The load history is shown in Table 1 and Fig. 2. One loading set consisted of 10 blocks, and the number of cycles in each block was 10,000, i.e., the number of cycles of each set was 10 5 . Fig. 2. Block program loading. 3-1
5
Embed
FATIGUE ASSESSMENT OF BILGE KNUCKLEJOINT OF VLCC ACCORDING ... · FATIGUE ASSESSMENT OF BILGE KNUCKLEJOINT OF VLCC ACCORDING TO JTP/JBP RULES 1. DESCRIPTION OF TEST AND EXPERIMENTAL
This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Transcript
FATIGUE ASSESSMENT OF BILGE KNUCKLEJOINT OF VLCC
ACCORDING TO JTP/JBP RULES
1. DESCRIPTION OF TEST AND EXPERIMENTAL RESULTS
The model was a bilge knuckle section for a double hull VLCC in approximately 1/3 scale, Ship Research
Panel 245 (2001). The model was about 6m in length, 5m in width, 3.6m in height and 20tons in steel weight. To
make stress distributions of the model similar to those of the actual ship, a three-floor space in the longitudinal
direction was modelled.
The model was fixed to a rigid wall at the double hull side, with the ship’s bottom being upside and the
inner bottom being downside. The load was applied by three syncronised hydraulic jacks on the centreline of
the double bottom, see Fig. 1. The model was built from mild steel in accordance with NK rules.
In order to initiate cracks only at the bilge knuckle section of the centre floor, the weld leg length at the
bilge knuckle section at the other floors was increased, and the weld toes were ground smooth.
Fig. 1. Bilge knuckle model.
The fatigue loading was constructed from a block loading simulating variable amplitude loading conditions
during sea-going service. The typical mean stress alternation for a VLCC is a tensile mean stress in full load
condition and a compressive mean stress in ballast condition. The applied load cycles were therefore composed
of five blocks with a tensile mean stress and five similar block with a compressive mean stress. The load history
is shown in Table 1 and Fig. 2. One loading set consisted of 10 blocks, and the number of cycles in each block
was 10,000, i.e., the number of cycles of each set was 105.