Assessment System of Remaining Life for Bridge Crane Based on the Internet of Things

In view of the highly randomness and uncertainty in the working condition of crane, take bridge crane as the research object. Firstly, based on the technology of the internet of things, the load capacity and the number of work cycles would be recorded, and the fatigue stress spectrum would be formed. Secondly, based on the Miners fatigue damage accumulation theory and the rain-flow algorithm, the equivalent stress amplitude would be obtained. Thirdly, curve regression model has been used to characterizing the relationship between the crack propagation and equivalent stress amplitude, and predicting the current crack size. Lastly, taking the predicted value of the crack size into the fracture mechanics formula, and estimated the remaining fatigue life of the bridge crane. The example demonstrated that, it is simple and practical to apply the techniques of the internet of things and the regression forecasting to the data collection and crack size prediction; it not only be able to estimate the remaining fatigue life quickly and accurately, but also be able to overcome the drawback of requiring the initial crack size in the fracture mechanics.

Thermal Fatigue Evaluation Method of Pipes by Equivalent Stress Amplitude

In recent years, reports have increased which are about failure cases caused by high cycle thermal fatigue both at light water reactors and fast breeder reactors. One of the biggest reasons of the cases is a turbulent mixing at a Tee-junction, where hot and cold temperature fluids are mixed, in a coolant system. In order to prevent thermal fatigue failures at Tee-junctions, The Japan Society of Mechanical Engineers (JSME) published the guideline S017-2003 (or JSME guideline) which is an evaluation method of high cycle thermal fatigue damage at a nuclear piping. It has some limitations in terms of its inconstant safety margin and its complexity in evaluation procedure, however. In order to solve these limitations, this paper proposes a new evaluation method of thermal fatigue damage with use of the “equivalent stress amplitude” which represents random temperature fluctuation effects on thermal fatigue damage. Because this new method makes methodology of evaluation clear and concise, it will contribute to improving the guideline for thermal fatigue evaluation.

Assessment of Error and Pressure Influence on Total Equivalent Stress Amplitude Calculation by WRC107

Bulletin WRC107 is most commonly used in attachment design, but still some uncertainties make it difficult to ensure safety in recent use. Two problems in fatigue evaluation were addressed here, first the bulletin is based on shell theory and some other assumption, and for various condition the calculation error is unknown; second pressure is not considered in calculation. To the first problem, an assessment was performed by comparing the total equivalent stress results of WRC107 and of finite element method (FEM). To the second problem, a method from Chinese standard HG20582-1998 Specification for Stress Calculation of Steel Chemical Vessels (HG method) was introduced as a supplement, and the reliability was studied. The results show that, total equivalent stress amplitude calculated by WRC107 may be underestimated, and its error mainly depends on parameters β and γ. Complemented by HG method, WRC107 could be used in calculation of shell under pressure and external loading.

Finite Element Analysis on the Fatigue Stresses of a Railway Vehicle Roller Bearing

The distributed fatigue stresses of 353130B roller bearing of China freight car with K5 type titling bogie are investigated using an elastic-plastic finite element (FE) analysis. Policy of two steps is applied. First, an integral FE analysis is performed on adapter-bearing-axle-wheel-track interactive system. Second, local analysis is applied to the local axle-bearing-adapter part, in which on the section of axle is with the bound condition obtained from the integral analysis. Wheel contact force spectrum on a curved railway line by on-line inspection is used for the present study. Previous proposed multivariate quadratic regression approach is applied for transferring the load spectrum to the dynamic stress spectrum at a special position of the bearing. Results reveal that the rollers, innerand outer-rings of bearing are subjected to distribute axially equivalent stress amplitude. The closer to axle side, the larger the equivalent stress amplitude. The equivalent stress amplitude of outer ring at the position close to the seal seat is relative larger to that of inner ring. The results are consistency with the shell failures of the bearings in production. Availability of present study is indicated.