The paper reviews the roots, the state-of-the-art and perspectives of multibody system dynamics. Some historical remarks show that multibody system dynamics is based on classical mechanics and its engineering applications ranging from mechanisms, gyroscopes, satellites and robots to biomechanics. The state-of-the-art in rigid multibody systems is presented with reference to textbooks and proceedings. Multibody system dynamics is characterized by algorithms or formalisms, respectively, ready for computer implementation. As a result simulation and animation are most important. The state-of-the-art in flexible multibody systems is considered in a companion review by Shabana.

https://hosting.umons.ac.be/html/mecara/grasmech/PaperSchiehlen.pdf

Multibody System Dynamics: Roots and Perspectives

As a key component in the wind turbine system, the power electronic converter and its power semiconductors suffer from complicated power loadings related to environment, and are proven to have high failure rates. Therefore, correct lifetime estimation of wind power converter is crucial for the reliability improvement and also for cost reduction of wind power technology. Unfortunately, the existing lifetime estimation methods for the power electronic converter are not yet suitable in the wind power application, because the comprehensive mission profiles are not well specified and included. Consequently, a relative more advanced approach is proposed in this paper, which is based on the loading and strength analysis of devices and takes into account different time constants of the thermal behaviors in power converter. With the established methods for loading and lifetime estimation for power devices, more detailed information of the lifetime-related performance in wind power converter can be obtained. Some experimental results are also included to validate the thermal behavior of power device under different mission profiles.

Thermal Loading and Lifetime Estimation for Power Device Considering Mission Profiles in Wind Power Converter

Cumulative damage during fatigue is studied analytically. Extensive reviews are per formed on the published damage models. Three different cumulative damage models are defined using several physical variables such as fatigue modulus and resultant strain. Proposed model I is defined using fatigue modulus, while models II and III are defined using resultant strains. Proposed models are derived as functions of nor malized applied stress level, r, and number of fatigue cycle, n. It is verified that the proposed cumulative damage model III has better agreement with the two stress level fatigue experimental data than other models.

Cumulative Damage Models and Multi-Stress Fatigue Life Prediction:

https://www.torsten-wichtmann.de/paper/journal/2005-CG-a-high-cycle-model.pdf

A high-cycle accumulation model for sand

The purpose of this paper is to provide a comprehensive state of the art of fatigue and cyclic loading of natural rock materials. Papers published in the literature are classified and listed in order to ease bibliographical review, to gather data (sometimes contradictory) on classical experimental results and to analyse the main interpretation concepts. Their advantages and limitations are discussed, and perspectives for further work are highlighted. The first section summarises and defines the different experimental set-ups (type of loading, type of experiment) already applied to cyclic/fatigue investigation of rock materials. The papers are then listed based on these different definitions. Typical results are highlighted in next section. Fatigue/cyclic loading mainly results in accumulation of plastic deformation and/or damage cycle after cycle. A sample cyclically loaded at constant amplitude finally leads to failure even if the peak load is lower than its monotonic strength. This subcritical crack is due to a diffuse microfracturing and decohesion of the rock structure. The third section reviews and comments the concepts used to interpret the results. The fatigue limit and S–N curves are the most common concepts used to describe fatigue experiments. Results published from all papers are gathered into a single figure to highlight the tendency. Predicting the monotonic peak strength of a sample is found to be critical in order to compute accurate S–N curves. Finally, open questions are listed to provide a state of the art of grey areas in the understanding of fatigue mechanisms and challenges for the future.

/pdf/cyclic-and-fatigue-behaviour-of-rock-materials-review-1wp1rdhrth.pdf

Cyclic and Fatigue Behaviour of Rock Materials: Review, Interpretation and Research Perspectives

A method is described which uses changes of apparent dynamic modulus and damping during fatigue cycling, for estimating accurately the fatigue lives of stainless steel (Rex 535) specimens This technique for estimating well in advance of failure the fatigue lives of individual specimens avoids the usual difficulties caused by scatter of fatigue results, and has enabled a more precise quantitative investigation to be made of cumulative fatigue damage (ie damage due to multi-level loading) than would have been possible using conventional experimental methods By estimating the remaining life of a specimen at one stress amplitude before measuring the equivalent remaining life at a second stress amplitude by cycling to failure, it was possible to determine lines of equal damage on a plot of stress amplitude versus remaining fatigue life These lines of equal damage were used to predict the fatigue lives of specimens subjected to programmes of multi-level loading, and the accuracy of these estimates, when co

R. H. W. Brook

Papers

Cumulative Damage in Fatigue: A Step towards Its Understanding: