Factors That Affect the Fatigue Strength of Power Transmission Shafting and Their Impact on Design

1986 ◽  
Vol 108 (1) ◽  
pp. 106-114 ◽  
Author(s):  
S. H. Loewenthal
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Stress Concentration ◽  
Power Transmission ◽  
Design Method ◽  
Surface Condition ◽  
Operational Reliability ◽  
Torsional Loading ◽  
Variable Amplitude ◽  
Limited Life

A long-standing objective in the design of power transmission shafting is to eliminate excess shaft material without compromising operational reliability. A shaft design method is presented which accounts for variable amplitude loading histories and their influence on limited life designs. The effects of combined bending and torsional loading are considered, along with a number of application factors known to influence the fatigue strength of shafting materials. Among the factors examined are surface condition, size, stress concentration, residual stress, and corrosion fatigue.

Fatigue Strength Assessment of a Butt-Welded Joint in Ship Structures Based on Time-Domain Strain Approach

2020 ◽  
pp. 1-16
Author(s):  
Yan Dong ◽  
Yordan Garbatov ◽  
Carlos Guedes Soares
Keyword(s):  
Residual Stress ◽  
Fatigue Strength ◽  
Time Domain ◽  
Welded Joint ◽  
Stress Strain ◽  
Ship Structures ◽  
Strength Assessment ◽  
Variable Amplitude ◽  
Notch Stress ◽  
Fatigue Strength Assessment

Fatigue strength assessment of a butt-welded joint in ship structures based on a time-domain strain approach is performed in this study. The service life load histories applied to the butt-welded joint located on the deck of a bulk carrier are generated, accounting for the still-water and wave-induced loads. The rainflow counting method is applied to analyze the load histories, and the long-term distributions of the load range are compared with those based on the conventional spectral fatigue analysis. An approach of converting the load history to a series of closed notch stress-strain hysteresis loops and several open notch stress-strain hysteresis curves is proposed and demonstrated under variable amplitude loading. The approach is based on analytical notch stress-strain estimations and consists of several steps to consider the material memory effect, overcoming some limitations of the existing methods. To determine the fatigue damage for the variable amplitude loading, a design fatigue curve is derived considering the uncertainty in the fatigue lives and load sequence effects. The intrinsic fatigue limit concept is used to filter the small amplitude cycles that do not have a damaging effect. The fatigue strength of the butt-welded joint is analyzed, taking the weld-induced residual stress and misalignment effects into account explicitly. The notch mean stresses or strain amplitudes of the cycles are significantly enhanced because of the presence of a high level of weld-induced tensile residual stress or misalignment, resulting in highly severe fatigue damage. 1. Introduction Complex ship structures containing geometrical and material discontinuities are prone to fatigue because of cyclic loads. Therefore, fatigue strength assessment has been an important criterion in the ship structural design (Guedes Soares & Moan 1991). Various fatigue design concepts for the assessment of welded joints, where fatigue failures mostly originate, are applied (Xu 1997; Radaj et al. 2006), and they can be classified into two types. The first one is based on S-N curves in combination with the Palmgren-Miner rule, and the second one is based on the crack propagation models and failure criteria.

Effects of Stress Concentration and Reinforcement on the Fatigue Strength of Rectangular Openings

1985 ◽  
Vol 22 (04) ◽  
pp. 339-350
Author(s):  
Pin Yu Chang
Keyword(s):  
Fatigue Life ◽  
Fatigue Strength ◽  
Stress Concentration ◽  
Maximum Stress ◽  
Design Method ◽  
Reduction Factor ◽  
Strength Reduction Factor ◽  
Approximate Methods ◽  
New Methods ◽  
Current Design

Large rectangular openings on the strength deck are a major concern of the designers of commercial and military ships. Currently used methods are inaccurate for the prediction of stress concentration factor (SCF). There is no commonly accepted criterion for the maximum stress. The current design method cannot be used to explain the behaviors of the structure when the stress at a small area is calculated as greater than the ultimate strength of the metal. Nor can it explain the failures that occur at relatively low nominal stress. All these problems can be better explained and analyzed by the concept of fatigue strength and fatigue life. This paper proposes some new methods for the prediction of SCF, approximate methods for the prediction of fatigue strength reduction factor due to stress concentration, and fatigue life of openings. Validation of the new method is also included.

Research of Fault Monitoring and Early Warning Technology of Optical Cable

2014 ◽  
Vol 986-987 ◽  
pp. 1549-1553
Author(s):  
Gang Zhang ◽  
Chuan Liu ◽  
Jie Ren ◽  
Zeng Hua Zhang ◽  
Wei Chen
Keyword(s):  
Network Management ◽  
Electric Power ◽  
Transmission Lines ◽  
Management System ◽  
Power Transmission ◽  
Design Method ◽  
Operational Reliability ◽  
Stable Operation ◽  
Network Management System ◽  
Application Systems

Electric power optic cables, as infrastructure facilities of the power communication system, are commonly affiliated to primary towers and poles of power transmission lines. And their safe and stable operation is one of important factors to guarantee the reliable power supply. At present, there are many kinds of professional application systems for equipment management in the field of Power System, so the level of their automation and intelligence is relatively high. But Management and Monitoring of outdoor lines are still staying the same as traditional methods, becoming a vulnerable part in smart grid. This paper introduces a network management system of electric power optic cables based on GIS and referred to the design method of Transmission Network Management System (TNMS). Its aims and several main developing technologies are also discussed. This system will play an important role in improving maintenance management and operational reliability for the power communication network.

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