Resumo em Inglês:

Abstract Motor bearings are prone to different degrees of performance degradation, fatigue damage and failure undergoing complex and harsh environments. Vibration signal analysis is a mature method for diagnosing motor bearing faults, while it is not applicable for installing additional vibration sensors on many occasions. Practically, the fault of motor bearings changes the air gap flux between the rotor and stator, which leads to harmonic fluctuations in the stator current. The current signals can be used to diagnose the motor bearing faults without additional sensors. Inevitably the harmonics caused by the motor bearing faults will be coupled with the original signals. This paper combines bi-spectrum and Convolution Neural Network (CNN) to analyze the current signals of motor bearing faults. The CNN diagnosis model is trained based on the local bi-spectrum of current, and the CNN parameters are optimized. Diagnose and analyze motor bearing faults with different fault implantation methods, working conditions, fault degrees and fault locations. The diagnostic accuracy reaches more than 80%.

Resumo em Inglês:

Abstract This work focuses on the comparative evaluation of the buckling capacity of steel spherical shells subjected to external pressure with existing design codes. The recorded experimental data of buckled spherical shells are compared with the calculated buckling pressure using design codes such as (i) European Convention for Constructional Steelwork (ECCS), (ii) Det Norske Veritas (DnV), (iii) British Standard (PD 5500) and (iv) American Bureau of Shipping (ABS). The selected experimental data are widely used in industrial applications. The experimental data are categorised as 'thin-shell', 'moderate-shell' and 'thick-shell' and reviewed against selected design codes. The comparative analysis clearly shows that the DnV design code with a deviation of 3.6% is well suited to estimate the buckling capacity of 'thick shells", while PD 5500 with a deviation of 9% to 50% is better suited for "medium and thin' shells. On the other hand, statistical analysis shows that PD 5500 is close to 1.0 with the value of COV (i.e., 1.281 and 9.383%). Further analysis of 28 steel spherical shell test data is performed and compared with the plotted curves in the format of PD 5500 and ECCS. The result shows that 3 test data are below the lower limit curve specified in the design guideline for ECCS, indicating that PD 5500 is the more conservative design guideline.