scholarly journals An Estimation on Two Stroke Low Speed Diesel Engines' Shaft Fatigue Strength due to Torsional Vibrations in Time Domain

2007 ◽  
Vol 17 (7) ◽  
pp. 572-578 ◽  
Keyword(s):  
Fatigue Strength ◽  
Time Domain ◽  
Diesel Engines ◽  
Torsional Vibrations ◽  
Low Speed

scholarly journals Practical confirmation of mechanical balancers effectiveness to reduce vibration of marine main diesel engines

2021 ◽  
Vol 2061 (1) ◽  
pp. 012054
Author(s):  
VA Bashkatov ◽  
SA Khudyakov ◽  
AV Ignatenko
Keyword(s):  
Diesel Engines ◽  
Torsional Vibrations ◽  
Inertial Forces ◽  
Vibration Measurements ◽  
Low Speed ◽  
Shaft Line ◽  
Overturning Moment

Abstract The article discusses compensators of unbalanced moments from inertial forces of the second and variable components of the overturning moment of the main order and the elastic moment at the resonance of torsional vibrations of the shaft line of modern marine low-speed diesel engines. The efficiency of the diesel engine’s operation is analyzed based on the vibration measurements on ships and some problems caused by these devices.

Compensations of the Discontinuous Nonlinearities in the Independent Joints Control of an Articulated Robot

2013 ◽  
Vol 430 ◽  
pp. 135-142
Author(s):  
Danut Receanu
Keyword(s):  
Industrial Robot ◽  
Linear Control ◽  
Torsional Vibrations ◽  
Low Speed ◽  
Discontinuous Nonlinearities ◽  
Articulated Robot

The paper presents the nonlinear torsional vibrations control of the joints in an articulated industrial robot, in Simulink /MATLAB. In this case, it is considered the classical linear control combined with compensations of the natural discontinuous nonlinearities in a robot with low speed.

scholarly journals Modern marine low-speed diesel engines: state, prospects and problems

2020 ◽  
Vol 94 (1) ◽  
pp. 143-154
Author(s):  
Khudyakov S. A. ◽  
Ignatenko A.V.
Keyword(s):  
Diesel Engines ◽  
Low Speed

Analysis of Unsteady Flows Past Horizontal Axis Wind Turbine Airfoils Based on Harmonic Balance Compressible Navier-Stokes Equations With Low-Speed Preconditioning

2011 ◽  
Author(s):  
M. Sergio Campobasso ◽  
Mohammad H. Baba-Ahmadi
Keyword(s):  
Wind Turbine ◽  
Time Domain ◽  
Harmonic Balance ◽  
Stokes Equations ◽  
Unsteady Aerodynamics ◽  
Horizontal Axis ◽  
Navier Stokes ◽  
Horizontal Axis Wind Turbine ◽  
Low Speed ◽  
Computational Performance

This paper presents the numerical models underlying the implementation of a novel harmonic balance compressible Navier-Stokes solver with low-speed preconditioning for wind turbine unsteady aerodynamics. The numerical integration of the harmonic balance equations is based on a multigrid iteration, and, for the first time, a numerical instability associated with the use of such an explicit approach in this context is discussed and resolved. The harmonic balance solver with low-speed preconditioning is well suited for the analyses of several unsteady periodic low-speed flows, such as those encountered in horizontal axis wind turbines. The computational performance and the accuracy of the technology being developed are assessed by computing the flow field past two sections of a wind turbine blade in yawed wind with both the time- and frequency-domain solvers. Results highlight that the harmonic balance solver can compute these periodic flows more than 10 times faster than its time-domain counterpart, and with an accuracy comparable to that of the time-domain solver.

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.

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