Fatigue life evaluation on key components of high-speed railway catenary system

The fatigue load spectrum and operation life evaluation of key components in the catenary system under the high speed train running condition were investigated.Firstly,based on the catenary model and pantograph model,the couple dynamic equations of pantograph–catenary were built with the Lagrange’s method;then the dynamic contact force was obtained by the Newmark method at the train speeds of 250,280 and 300 km/h,respectively.Secondly,the finite element model(FEM)of one anchor section’s catenary was built to analyze its transient response under the contact force as train running;then the loading time history of messenger wire base,steady arm,registration tube,oblique cantilever,and straight cantilever were extracted.Finally,the key components’fatigue spectrum was carried out by the rain-flow counting method,and operation life was estimated in consideration of such coefficients,such as stress concentration,shape and dimension,surface treatment.The results show that the fatigue life of the catenary system reduces with the increasing of train speed;specifically,the evaluated fatigue life of the steady arm is shorter than other components.

Fatigue life evaluation of girth butt weld within welded cast steel joints based on the extrapolation notch stress method

The fatigue life evaluation of the girth butt weld within the welded cast steel joint was studied based on the extrapolation notch stress method.Firstly,the mesh sensitivity of the finite element model of the welded cast steel joint was analyzed to determine the optimal mesh size.Based on the stress field analysis of the finite element model of the welded cast steel joint at the weld toe and weld root,the sharp model of the extrapolation notch stress method was applied to derive the effective notch stress of the rounded model belonging to the effective notch stress method,in which the key problem is to calculate the extrapolation point C,and the extrapolation point C has an exponential function relationship with the geometric parameters of the welded cast steel joint.By setting different values of geometric parameters,the corresponding value of parameter C is calculated,and then the functional relationship between the extrapolation point C and the geometric parameters can be obtained by the multiple linear regression analysis.Meanwhile,the fatigue life evaluation of the girth butt weld within welded cast steel joints based on the effective notch stress was performed according to the guideline recommended by the IIW(International Institute of Welding).The results indicate that the extrapolation notch stress method can effectively simplify the process of calculating the effective notch stress and accurately evaluate the fatigue life of the girth butt weld within welded cast steel joints.

Finite Element Simplified Fatigue Analysis Method for a Non-tubular Joint of an Offshore Jacket Platform

This paper proposes the finite element simplified fatigue analysis method for fatigue evaluation of the composite non-tubular joint structure of an offshore jacket subjected to wave loads. The skirt pile sleeve of the offshore jacket, which had been in service, was taken as an example of the non-tubular joint structure. SACS software was used for global analysis of multi-directional wave loads for the jacket platform, and ALGOR software was used to build a finite element model, perform finite element analysis, post-process stress results for acquiring the stress range, and perform fatigue evaluation. The analysis results indicate that the extreme stress range is within the allowable stress range and meets the requirements of DNV code. That means the simplified fatigue analysis method is effective and can be used in fatigue design for the non-tubular joint structure of an offshore jacket.

AFC （AREVA Fatigue Concept）-An Integrated and Multi-disciplinary Approach to the Fatigue Assessment of NPP Components

The prevention of fatigue damages is a crucial issue for NPPs （nuclear power plants）. The AFC （AR.EVA fatigue concept） provides for a multi-step and mnlti-disciplinary process against fatigue during the design and operating phase of NPPs. The entire process of fatigne design is based on an installed FAMOS （fatigue monitoring system）. In this way, realistic load data are available to manage the component ageing and enable the optimization of operating modes. The measured temperatures are processed via a FFE （fast fatigue evaluation）. Thus, an online fatigue evaluation of the cumulative usage factor is performed after every operational cycle. This procedure gives a first fatigue status of the power plant. Furthermore, a DFC （detailed fatigue calculation） conforming to the code rules is carried out in order to determine the state of the plant at the highest loaded positions. These finite element analyses include determination of thermal transient and subsequent stresses and strains. Fatigue environmental factors are taken into account in these studies.

Fatigue damage reliability analysis for Nanjing Yangtze river bridge using structural health monitoring data

To evaluate the fatigue damage reliability of critical members of the Nanjing Yangtze river bridge, according to the stress-number curve and Miner’s rule, the corresponding expressions for calculating the structural fatigue damage reliability were derived. Fatigue damage reliability analysis of some critical members of the Nanjing Yangtze river bridge was carried out by using the strain-time histories measured by the structural health monitoring system of the bridge. The corresponding stress spectra were obtained by the real-time rain-flow counting method. Results of fatigue damage were calculated respectively by the reliability method at different reliability and compared with Miner’s rule. The results show that the fatigue damage of critical members of the Nanjing Yangtze river bridge is very small due to its low live-load stress level.

Evaluation of upper limb muscle fatigue based on surface electromyography

Fatigue is believed to be a major contributory factor to occupational injuries in machine operators.The development of accurate and usable techniques to measure operator fatigue is therefore important.In this study,we used a novel method based on surface electromyography (sEMG) of the biceps brachii and the Borg scale to evaluate local muscle fatigue in the upper limb after isometric muscle action.Thirteen young males performed isometric actions with the upper limb at different force levels.sEMG activities of the biceps brachii were recorded during the actions.Borg scales were used to evaluate the subjective sensation of local fatigue of the biceps brachii after the actions.sEMG activities were analyzed using the one-third band octave method,and an equation to determine the degree of fatigue was derived based on the relationship between the variable and the Borg scale.The results showed that the relationship could be expressed by a conic curve,and could be used to evaluate muscle fatigue during machine operation.

Research on the Dynamic Performance of Low-Yield-Strength Shear Panel Damper for Bridge Application

This study seeks to develop a scientific understanding of the effects of dynamic loading history on the low-yield-strength shear panel damper （LYSPD） mechanical properties and fatigue performance. The LYSPD model is supposed as perfect elastic-plastic without strength deterioration. By adjusting the damper strength with the above supposition in the DYMO software, the serial earthquake response waves of the LYSPD under different soil conditions are obtained firstly. Subsequently, several waves, the most prone to damage at each soil condition. are selected as dynamic loading waves to verify the LYSPD dynamic performances experimentally. The test re- sults suggest that the dynamic loading histories have no influence on the LYSPD strength or the supposed model while they affect the fatigue performance. The applicability and accuracy of three fatigue evaluation metbods, cumulative plastic shear strain, cumulative energy absorption and Miner rule, are also compared according t,o the test results.