Failure Analysis of Cracked Reducer Flange

A cracked reducer flange was analyzed for the cause of the failure. The flange was carefully cut to obtain samples for metallographic, X-ray, and scanning electron microscopy (SEM) Examinations. The examinations revealed that the introduction of chloride ions in the operational service led to pitting corrosion in the inner surface of the flange. Chloride ion inclusions were probably the result of chemical contaminations, i.e., cleaning chemicals’ contamination during shutdown of the operation. The introduction of corrosion pits caused unexpected load stress intensification and cracking of the flange. Consequently, stress corrosion cracking emanated from the pits under the influence of chloride attack and operational pressure. Then the cracks propagated in a transgranular manner, in the radial direction of the flange, until the final failure occurred.     

A comparative study on the identification of the dynamical model of multi-mass electrical drives using wavelet transforms

This paper deals with dynamical modelling and modal identification of a special class of electromechanical systems: the multi-mass electrical drives. The aim of the work is to investigate the usefulness and the performance of the continuous wavelet transform (CWT) for the estimation of modal parameters, such as damping ratios and natural frequencies of these electromechanical systems. For this investigation, two models of elastic drive systems are considered: the two-mass and the three-mass models. The modal analysis identification using CWT is compared to the Hilbert–Huang transform technique and evaluated in terms of accuracy and ability to estimate modal parameters with different inputs, aptitude to distinguish several modes especially in the case of closely spaced modes and resistance to noisy conditions. In view of the results of the study, the advantages and shortcomings of each technique are presented and discussed.     

Shear Strengthening of RC T-Beams Using Mechanically Anchored Unbonded Dry Carbon Fiber Sheets

This research studies the feasibility and effectiveness of a new method of strengthening existing RC T-beams in shear by using mechanically anchored unbonded dry carbon fiber (CF) sheets. This method eliminates the debonding of epoxy-bonded carbon-fiber-reinforced polymer (CFRP) sheets and utilizes the full capacity of dry CF sheets. In this method, dry CF sheets are wrapped around and bonded to two steel rods. Then the rods are anchored to the corners of the web-flange intersection of the T-beam with mechanical bolts. This makes a U-shaped dry CF jacket around the web which increases the shear strength of the T-beam using the privilege of higher tensile strength and modulus of elasticity of dry CF compared to composite CFRP. A total of three RC T-beams with shear span-to-depth ratio of 2.0 were tested under increasing monotonic load till failure. The pilot tests were done as a proof-of-concept of the effectiveness of the proposed method in increasing the shear capacity of the RC T-beams. The first T-beam, which was tested as the control beam, failed in shear. The second beam was strengthened by using a U-shaped CFRP sheet that was externally bonded to the web of the beam in the shear zones. The third beam was strengthened by using anchored U-shaped dry CF sheet. The test results showed that the beam strengthened by the new mechanically anchored dry CF had about 48% increase in shear capacity as compared to the control beam and 16% increase in shear capacity as compared to the beam strengthened by CFRP epoxy-bonding method.     

Monitoring corrosion and corrosion control of iron in HCl by non-ionic surfactants of the TRITON-X series - Part I. Tafel polarisation, ICP-AES and EFM studies

The corrosion inhibition characteristics of non-ionic surfactants of the TRITON-X series, known as TRITON-X-100 (TX-100), TRITON-X-165 (TX-165) and TRITON-X-305 (TX-305), on iron in 1.0 M HCl solution were studied. Measurements were conducted in 1.0 M HCl solutions without and with various concentrations of the three selected surfactants using chemical (ICP-AES method of analysis of dissolved cations) and electrochemical (Tafel polarisation and EFM) techniques at 25 °C. These measurements were complemented with SEM and EDX examinations of the electrode surface. Polarisation data showed that the non-ionic surfactants used in this study acted as mixed-type inhibitors with cathodic predominance. The protection efficiency increased with increase in surfactant concentration. Maximum protection efficiency of the surfactant was observed at concentrations around its CMC. From their molecular structure, these surfactants may adsorb on the metal surface through two lone pairs of electrons on the oxygen atoms of the hydrophilic head group.     

A priori parallel machines scheduling

We address the probabilistic generalization of weighted flow time on parallel machines. We present some results for situations which ask for “long-term robust” schedules of n jobs (tasks) on m parallel machines (processors): on any given day, only a random subset of jobs needs to be processed. The goal is to design robust a priori schedules (before we know which jobs need to be processed) which, on a long-term horizon, are optimal (or near optimal) with respect to total weighted flow time. The originality of this work is that probabilities are explicitly associated with data such that further classical properties of a task (processing time and weight) we consider a probability of presence. After motivating this investigation we analyze the computational complexity, analytical properties, and solution procedures for these problems. Special care is also devoted to assess experimentally the performance of a priori strategies.     

Characterisation and accumulation of squalene and n‐alkanes in developing Tunisian Olea europaea L. fruits

The present investigation was carried out for the analysis of hydrocarbon compounds of Tunisian Meski olives. The hydrocarbon fraction of the oils was found to contain twelve n‐alkanes (C₂₂–C₃₆) and squalene. Results from the quantitative characterisation of the oils revealed that squalene was the most abundant hydrocarbon compound, at all development stages of Meski olive, accounting for more 92% of total hydrocarbons. Pentacosane (C₂₅), heptacosane (C₂₇) and tricosane (C₂₃) represented the major compounds of n‐alkanes. The highest accumulation of n‐alkanes and squalene was observed at early stages of olive development [before 21st week after the flowering date (WAFD)]. The greatest decrease of these components occurred between 21st and 26th WAFD of the olives. At complete maturity of the fruit, the level of squalene and total n‐alkanes was 126.52 and 9.13 mg per 100 g oil, respectively. Hence, the content of n‐alkanes and squalene was remarkably influenced by the ripeness process of olive.     

Privacy-preserving and tokenless chaotic revocable face authentication scheme

With the large-scale proliferation of biometric systems, privacy and irrevocability issues of their data have become a hot research issue. Recently, some researchers proposed a couple of schemes to generate BioHash, e.g. PalmHash, however, in this paper, we point out that the previous schemes are costly in terms of computational complexity and possession of USB tokens to generate pseudorandom numbers. To overcome the problems, we propose a novel chaotic FaceHashing scheme which preserves privacy of a biometric user. The presented scheme does not need users to posses USB tokens in generating pseudorandom sequences, which is a cost-effective solution. Besides, our scheme minimizes the system complexity with simple operations to attain the FaceHash. Experimental results show that the proposed scheme is efficient, secure, and revocable in case FaceHash is theft or compromised.