Fatigue Life Assessment of Tower Crane Based on Neural Network to Obtain Stress Spectrum

In order to reduce the probability of crane safety accidents, a method based on radial basis neural network is proposed to quickly obtain the stress spectrum and calculate the remaining life of the crane. Firstly, taking an in-service tower crane as an example, an ANSYS finite element model is established based on actual parameters, and the finite element model is statically analyzed to obtain the location of the dangerous point. Secondly, the typical operating conditions of the crane are simulated. The position of the trolley and the lifting load are used as the input layer while the equivalent stress value at any point is used as the output layer to train the radial basis neural network model. Using the trained radial basis neural network model can obtain time-stress curve at any point quickly. Finally the remaining life is assessed based on the fracture mechanics method. The results show that this method that using the radial basis function neural network model to obtain the time-stress curve at any point can greatly save the cumbersome process and a lot of investment in the field measurement of the crane, and also provides a reliable basis for the long-term safe use and later maintenance of the crane.

Simulations of Helical Inflationary Magnetogenesis and Gravitational Waves

Using numerical simulations of helical inflationary magnetogenesis in a low reheating temperature scenario, we show that the magnetic energy spectrum is strongly peaked at a particular wavenumber that depends on the reheating temperature. Gravitational waves (GWs) are produced at frequencies between 3 nHz and 50 mHz for reheating temperatures between 150 MeV and 3 × 105 GeV, respectively. At and below the peak frequency, the stress spectrum is always found to be that of white noise. This implies a linear increase of GW energy per logarithmic wavenumber interval, instead of a cubic one. Both in the helical and nonhelical cases, the GW spectrum is followed by a sharp drop for frequencies above the respective peak frequency. In this magnetogenesis scenario, the presence of a helical term extends the peak of the GW spectrum and therefore also the position of the aforementioned drop toward larger frequencies compared to the case without helicity. This might make a difference in it being detectable with space interferometers. The efficiency of GW production is found to be almost the same as in the nonhelical case, and independent of the reheating temperature, provided the electromagnetic energy at the end of reheating is fixed to be a certain fraction of the radiation energy density. Also, contrary to the case without helicity, the electric energy is now less than the magnetic energy during reheating. The fractional circular polarization is found to be nearly 100% in a certain range below the peak frequency range.

Improved fatigue failure model for reliability analysis of mechanical parts inducing stress spectrum

To study the influence of random parameter on the reliability of the vehicle front stabilizer bar, the fatigue strength is analyzed according to the random fatigue strength prediction method, then the fatigue limit of the actual parts are estimated, a new fatigue failure model is improved by using the fatigue limit [Formula: see text] of actual parts. Through this model, the stress spectrum collected by real vehicle is introduced, Monte-Carlo simulation method is adopted to analyze the reliability and sensitivities of stabilizer bar under driving conditions. In addition, the influence of each basic random parameter on the failure probability is obtained. The results show that stabilizer bar diameter has a great influence on the failure probability, which provides certain reference for improving the reliability of the front stabilizer bar.

Investigation of fractures mechanisms of railway axles

The paper gives a systematic overview of literature sources who consider impacts critical damage of mechanical, corrosive and thermal nature which may occur on railway axles during operation and which may be the causes of their fracture. The results of the research of the mechanisms that cause cracks, crack propagation and final fracture of the railway vehicle axle, such as material fatigue and the appearance of localized notches caused by paint (coating) separation, damage from ballast impact and pitting corrosion are presented. The influence of high temperatures and overheating on the axles was analyzed and an excerpt from the research published in one research report was given. Some significant suggestions for optimizing the design of the axles are highlighted which would take into account the analysis of time-varying axle stresses, stress spectrum in operation, axle tolerance to damage and the existence of residual surface stresses. The reliefs of the fracture surfaces of the axle after the railway incidents and the derailment of the rail vehicle from the rails are presented and explained.