CN-117341937-B - Ship structure fatigue strength analysis method and system

CN117341937BCN 117341937 BCN117341937 BCN 117341937BCN-117341937-B

Abstract

The invention provides a ship structure fatigue strength analysis method and a system, which are characterized in that a host vibration load and a wave load born by a ship structure are calculated based on ship data, characteristic data of the ship structure and global sea state data, then a stress response process under the combined action of the wave load and the host vibration load, a spectral density function of the stress response process, each step of spectral moment of the stress response process and zero crossing rate of the stress response process are calculated, then stress response and stress response peak value of the ship structure under the action of sinusoidal vibration load are calculated, the stress cycle times of the ship structure are calculated based on the stress response and combined with a fatigue life S-N curve, further fatigue damage of the host vibration load is calculated, finally total coupling fatigue damage under the long-term sea state is calculated, and further the fatigue damage of the ship structure under the combined action of high-low frequency load is calculated, so that the accuracy and the reliability of the ship structure fatigue strength calculation are effectively improved.

Inventors

ZHANG FUJIE
FAN JIE
GUO YULONG
LI JIANPENG

Assignees

上海船舶运输科学研究所有限公司

Dates

Publication Date: 20260512
Application Date: 20231017

Claims (10)

1. The method for analyzing the fatigue strength of the ship structure is characterized by comprising the following steps of: acquiring ship data, characteristic data of a ship structure and global sea state data, calculating a vibration load of a host according to the vibration frequency and the vibration amplitude of the host in the characteristic data, and calculating the wave load born by the ship structure by adopting wave load calculation software, wherein the ship data comprises the ship sailing life and the ship sailing time; Calculating a stress response process under the combined action of the wave load and the host vibration load based on a Gaussian narrow-band process of the wave load and a Gaussian narrow-band process of the host vibration load, calculating a spectral density function of the stress response process according to a spectral density function of the Gaussian narrow-band process of the wave load and a spectral density function of the Gaussian narrow-band process of the host vibration load, calculating each order of spectral moment of the stress response process according to the spectral density function of the stress response process, and calculating the zero crossing rate of the stress response process based on each order of spectral moment of the stress response process; Setting the vibration form of the vibration load of the host machine as sinusoidal vibration to obtain sinusoidal vibration load, respectively calculating stress response of the ship structure under the action of the sinusoidal vibration load and stress response peak value under the action of the sinusoidal vibration load according to the sinusoidal vibration load, respectively calculating the stress cycle times of the ship structure and the stress cycle times of the ship structure when the ship structure is damaged during the sailing life of the ship based on the stress response and combining with the fatigue life S-N curve, and further calculating the fatigue damage under the action of the vibration load of the host machine; And calculating a stress response peak value of the ship structure under the combined action of the wave load and the host vibration load according to the wave load and the host vibration load, calculating a stress peak probability density function under the combined action of the wave load and the host vibration load under a certain short-term sea condition according to the zero-order moment of the stress response process, the stress response peak value under the action of the sinusoidal vibration load and the stress response peak value under the combined action of the wave load and the host vibration load, calculating the coupling fatigue damage under the certain short-term sea condition according to the stress peak probability density function, the stress response peak value under the combined action of the wave load and the host vibration load, the sailing time, the zero crossing rate of the stress response process and the wave direction in the global sea condition data, calculating the total coupling fatigue damage under the long-term sea condition according to the coupling fatigue damage under the short-term sea condition, and calculating the fatigue damage under the combined action of the wave load and the host vibration load.
2. The method according to claim 1, wherein in the step of obtaining and calculating the data, the ship data further includes a ship movement service identification code, a ship name, ship longitude and latitude position information, a navigation state, a time stamp, a speed to ground, a draft, a departure port, a destination port, and a pre-determined time, and the global sea state data includes wave direction, global typhoon data, and global marine meteorological data.
3. The method for analyzing fatigue strength of a ship structure according to claim 1, wherein in the step of calculating zero crossing rate, each order of the moment of the gaussian narrowband process of the wave load is calculated according to a spectral density function of the gaussian narrowband process of the wave load, each order of the moment of the gaussian narrowband process of the host vibration load is calculated according to a spectral density function of the gaussian narrowband process of the host vibration load, and the zero crossing rate of the stress response process is calculated according to each order of the moment of the gaussian narrowband process of the wave load and each order of the moment of the gaussian narrowband process of the host vibration load.
4. The method for analyzing fatigue strength of a ship structure according to claim 1, wherein in the data acquiring and calculating step, the ship structure is a ship main frame base structure.
5. The method of claim 4, wherein the characteristic data of the ship structure includes a host vibration frequency, an amplitude, a rotational speed, and a power.
6. A ship structure fatigue strength analysis system is characterized by comprising a data acquisition and calculation module, a zero crossing rate calculation module, a host vibration fatigue damage calculation module and a coupling fatigue damage calculation module which are connected in sequence, The data acquisition and calculation module acquires ship data, characteristic data of a ship structure and global sea state data, calculates a host vibration load according to host vibration frequency and amplitude in the characteristic data, and calculates wave load born by the ship structure by adopting wave load calculation software, wherein the ship data comprises ship sailing life and sailing time; the zero crossing rate calculation module calculates a stress response process under the combined action of the wave load and the host vibration load based on a Gaussian narrow-band process of the wave load and a Gaussian narrow-band process of the host vibration load, calculates a spectral density function of the stress response process according to a spectral density function of the wave load and a spectral density function of the host vibration load, calculates each order of the moment of the stress response process according to the spectral density function of the stress response process, and calculates the zero crossing rate of the stress response process based on each order of the moment of the stress response process; The main machine vibration fatigue damage calculation module is used for setting the vibration mode of the main machine vibration load as sinusoidal vibration to obtain sinusoidal vibration load, respectively calculating stress response of the ship structure under the action of the sinusoidal vibration load and stress response peak value under the action of the sinusoidal vibration load according to the sinusoidal vibration load, respectively calculating the stress cycle times of the ship structure and the stress cycle times of the ship structure when the ship structure is damaged in the ship navigation life period based on the stress response and the fatigue life S-N curve, and further calculating the fatigue damage under the action of the main machine vibration load; The coupling fatigue damage calculation module calculates a stress response peak value of the ship structure under the combined action of the wave load and the host vibration load according to the wave load and the host vibration load, calculates a stress peak probability density function under the combined action of the wave load and the host vibration load under a certain short-term sea condition according to a zero-order spectral moment of the stress response process, the stress response peak value under the action of the sinusoidal vibration load and the stress response peak value under the combined action of the wave load and the host vibration load, calculates coupling fatigue damage under a certain short-term sea condition according to the stress peak probability density function, the stress response peak value under the combined action of the wave load and the host vibration load, sailing time, the zero crossing rate of the stress response process and the wave direction in the global sea condition data, calculates total coupling fatigue damage under a long-term sea condition according to the coupling fatigue damage under the short-term sea condition, and calculates fatigue damage of the ship structure under the combined action of the wave load and the host vibration load according to the fatigue damage under the action of the total coupling fatigue damage and the host vibration load.
7. The ship structure fatigue strength analysis system according to claim 6, wherein the ship data further comprises a ship movement service identification code, a ship name, ship longitude and latitude position information, a sailing state, a time stamp, a speed to ground, a draft, a departure port, a destination port, and a pre-time, and the global sea state data comprises wave directions, global typhoon data, and global marine meteorological data.
8. The ship structure fatigue strength analysis system according to claim 6, wherein in the zero crossing rate calculation module, each order of the spectral moment of the gaussian narrowband process of the wave load is calculated according to a spectral density function of the gaussian narrowband process of the wave load, each order of the spectral moment of the gaussian narrowband process of the host vibration load is calculated according to a spectral density function of the gaussian narrowband process of the host vibration load, and the zero crossing rate of the stress response process is calculated according to each order of the spectral moment of the gaussian narrowband process of the wave load and each order of the spectral moment of the gaussian narrowband process of the host vibration load.
9. The marine structure fatigue strength analysis system of claim 6, wherein the marine structure is a marine host base structure.
10. The marine structure fatigue strength analysis system of claim 9, wherein the characteristic data of the marine structure includes host vibration frequency, amplitude, rotational speed, and power.

Description

Ship structure fatigue strength analysis method and system Technical Field The invention relates to the technical field of fatigue analysis of ship structures, in particular to a fatigue strength analysis method and system of a ship structure under the combined action of high-frequency load and low-frequency load. Background Ships play an extremely important role in shipping as the primary water transport means in the sea and in the inland river. In this case, the strength to which the ship is subjected is very high in various marine environments which are operated at sea for a long period of time and are exposed to the rapid change in the sea. The hull is continuously eroded by seawater in navigation, structural fatigue of the ship can be caused after long-term accumulation, so that the problem of structural quality of the ship is caused, and fatigue damage is considered as one of main damage forms of the ship and marine engineering structures. In addition to the fact that the ship structure is subjected to the continuous action of wave loads during normal sailing, it should be noted that the local structure of the ship is subjected to other loads of different types, which is particularly evident for the local main foundation structure of the ship. Under the condition of long-term high-strength operation of the ship, the ship main engine is continuously operated, and vibration load is generated when the main engine is operated for a long time, so that the load is needed to be considered to be calculated on fatigue damage caused to the main engine base structure. The wave load is a low-frequency load, the vibration load is a high-frequency load, the coupling effect can be generated under the combined action of the two high-frequency load and the low-frequency load, and a method is deduced for calculating the fatigue damage under the coupling effect of the load. In the existing fatigue strength calculation method of the ship structure under the action of high-low frequency load or combined load, the calculation object is mainly focused on the marine structure, the attention on the ship structure, particularly the main machine base structure is less, the calculation load is mainly wave load and wind load which are considered, the wave load and flow load and the like, and the wave load and the main machine vibration load are rarely considered in a combined way. The processing method for the two loads mainly comprises a simple addition method, a load addition method and the like, wherein the simple addition method is simple and direct in calculation process, the calculation result is generally dangerous, the calculation result of the constant amplitude load method in the load addition method is generally conservative, and the application process is complex. Therefore, for fatigue damage calculation under the combined action of two long-term distributed combined loads, no efficient and absolute reliable calculation method exists. Therefore, there is a need for a method for analyzing fatigue strength of a ship structure, which considers the wave load and the vibration load of a main machine, and has high calculation speed and high accuracy. Disclosure of Invention In order to solve the problems of low accuracy, safety, economy, reliability and the like in fatigue strength calculation of high-low frequency load, particularly vibration load and wave load coupling in the existing ship structure fatigue strength analysis process, the invention provides a ship structure fatigue strength analysis method, which is used for calculating host vibration load and wave load based on ship data, characteristic data of a ship structure and global sea state data, calculating fatigue damage of the ship structure under the combined action of the wave load and the host vibration load based on the wave load and the host vibration load by adopting a specific calculation method, and effectively improving the accuracy and reliability of fatigue strength calculation of the ship structure under the combined action of the high-low frequency combined load. The invention also relates to a ship structure fatigue strength analysis system. The technical scheme of the invention is as follows: The method for analyzing the fatigue strength of the ship structure is characterized by comprising the following steps of: acquiring ship data, characteristic data of a ship structure and global sea state data, calculating a vibration load of a host according to the vibration frequency and the vibration amplitude of the host in the characteristic data, and calculating the wave load born by the ship structure by adopting wave load calculation software, wherein the ship data comprises the ship sailing life and the ship sailing time; Calculating a stress response process under the combined action of the wave load and the host vibration load based on a Gaussian narrow-band process of the wave load and a Gaussian narrow-band process of the host vibration load, c