A View on the General Practice in Engineering Failure Analysis

Analysis of engineering failures is a complex process that requires information from personnel having expertise in many areas. From the information gathered, a failure analyst tries to discover what was fundamentally responsible for the failure. This fundamental cause is termed the “root cause” and helps in the determination of the sequence of events that led to the final failure. Root cause analysis also helps in finding solutions to the immediate problem and provides valuable guidelines as to what needs to be done to prevent recurrence of similar failures in future. However, experience suggests that most failure analyses fall short of this goal. A significant number of failure analysts incorrectly use the term “root cause” when what they really establish is the primary cause of failure or simple physical cause. This paper examines a few service failures to demonstrate that the term root cause is not adequately understood.     

Decoupling Capacitor Estimation and Allocation using Optimization Techniques for Power Supply Noise Reduction in System-on-Chip

Journal of Electronic Testing - This article examines the signal integrity problem arising due to resistive drop, inductive noise and electro- migration, causing voltage fluctuations known as...     

Temperature-dependent index of refraction of monoclinic Ga2O3 single crystal

We present temperature-dependent refractive index along crystallographic b[010] and a direction perpendicular to (100)-plane for monoclinic phase (β) Ga(2)O(3) single crystal grown by the optical floating zone technique. The experimental results are consistent with the theoretical result of Litimein et al.1. Also, the Sellmeier equation for wavelengths in the range of 0.4-1.55 μm is formulated at different temperatures in the range of 30-175 °C. The thermal coefficient of refractive index in the above specified range is ~10(-5)/°C.     

A study on the structural and mechanical properties of nanocrystalline CuS thin films grown by chemical bath deposition technique

We report a chemical route for the deposition of nanocrystalline thin films of CuS, using aqueous solutions of Cu(CH₃COO)₂, SC(NH₂)₂ and N(CH₂CH₂OH)₃ [triethanolamine, i.e. TEA] in proper concentrations and ratios. The films were structurally characterized using X-ray diffraction technique (XRD), field emission scanning electron microscopy (FESEM) and optical analysis [both photo luminescence (PL) and ultraviolet-visible (UV-vis)]. Optical studies showed a large blue shift in the band gap energy of the films due to quantum confinement effect exerted by the nanocrystals. From both XRD and FESEM analyses, formation of CuS nanocrystals with sizes within 10-15 nm was evident. A study on the mechanical properties was carried out using nanoindentation and nanoscratch techniques, which showed good mechanical stability and high adherence of the films with the bottom substrate. Such study on the mechanical properties of the CuS thin films is being reported here for the first time. Current-voltage (I-V) measurements were also carried out for the films, which showed p-type conductivity.     

Using electrochemical impedance spectroscopy to predict the corrosion resistance of unexposed coated metal panels

The goal of the current work was to determine if electrochemical impedance spectroscopy (EIS) testing of a series of coated but unexposed metal panels could predict the corrosion results of other sections of the same coated panels that were subjected to both continuous and cyclic corrosion testing. Variables included metal, pretreatment, primer, and topcoat. EIS results were shown to be strongly dependent upon the time-of-residence in the electrochemical cell prior to commencement of testing, and to the choice of electrolyte used in the cell. Good correlations between EIS and corrosion testing were seen for topcoat effects, but not for pretreatment effects. EIS results appear to relate mostly to barrier properties rather than electrochemical properties of coatings. It is suggested that the variation seen in EIS solution resistance values (R_s) can be utilized to quantify total system error. Total error was estimated by three techniques: total R_s variation, panel replicate variation, and EIS reading replication. The three approaches yielded similar results: total error for equivalent circuit components expressed in log₁₀ form was on the order of 50%, expressed as percent standard deviation.     

Failure analysis of oxygen hose of the lance equipment in LD shop of Tata steel

The hose of the oxygen lancing equipment in LD shop # 2 has failed at the weld–bellows interface by reverse bending fatigue. The bending stresses were resulted due to inclined fitting of the hose at the fixed flange end. No metallurgical abnormalities or weld defects or mechanical damages were responsible for the fatigue crack initiation. It is recommended that if inclined fitment of the hose is not a process requirement, the original design be restored to realize the expected life of the component. On the other hand, if inclined fitment cannot be avoided, additional support may be provided for the hose at the fixed flange end to avoid reverse bending at the weld–bellows interface. A detailed analysis of the failure is presented in this report.     

New mesoporous titanium–phosphorus mixed oxides having bifunctional catalytic activity

New mesoporous titanium–phosphorus mixed oxides templated by non-ionic triblock copolymer Pluronic F127 under evaporation induced self-assembly (EISA) method and using unconventional phosphorus source trimethylphosphite have been reported. Powder XRD, TEM and N₂ sorption studies are employed to characterize the mesophases. TPD-NH₃ experiments suggested an increase in surface acidity with the increase in the molar ratio of Ti/P in these mesoporous mixed oxides from 1 to 2. Interestingly these mesoporous materials showed excellent bifunctional catalytic activity in acid catalyzed Friedel–Crafts benzylation of bulky aromatics and partial oxidation of styrene to benzaldehyde with dilute H₂O₂ oxidant under mild liquid phase conditions.     

Attacks and Remedies in Collaborative Recommendation

Collaborative-filtering recommender systems are an electronic extension of everyday social recommendation behavior: people share opinions and decide whether or not to act on the basis of what they hear. Collaborative filtering lets you scale such interactions to groups of thousands or even millions. Publicly accessible user-adaptive systems such as collaborative recommender systems introduce security issues that must be solved if users are to perceive these systems as objective, unbiased, and accurate.