Sustainability through disassembly modeling, planning, and leveling: a case study

The increasing environmental and economic pressures have contributed to the practice of recycling and remanufacturing. Product disassembly is a vital strategy of industrial recycling and remanufacturing which retrieves the desired parts and/or subassemblies by separating a product into its constituents. In this context, decision for disassembly gains importance. Disassembly modeling and planning is a critical activity rather than assembly, because the terminal goal is not vitally fixed, but depends on the product usage and market demands for used parts and recycled materials. Disassembly involves more uncertainties in system structures and components rather than in assembly. This article applies the recent methods for modeling and process planning the disassembly to an industrial product, i.e., rotary switch. The disassembly approach has been practically validated in industrial scenario.     

Corrosion behaviour and characterisation of Ni–Nb<Subscript>2</Subscript>O<Subscript>5</Subscript> composites prepared by pulse electrodeposition

The Ni–Nb₂O₅ composites were prepared by pulse electrodeposition method. Operating variables were optimized for getting a good deposit. The quantity of Nb₂O₅ particles in the coating was analyzed by an energy-dispersive X-ray diffraction spectrometer. X-ray diffraction and scanning electron microscopy were used to analyze the structure and surface morphology of the coatings. Texture coefficient and hardness of the deposits were determined and discussed. The corrosion behavior of the coatings was analyzed by traditional weight loss and electrochemical methods. Comparisons of the corrosion behaviour of coatings obtained by direct current (DC) and pulse current (PC) were investigated.     

Critical Assessment of Short-Term Stress-Relaxation Studies for the Prediction of Creep Properties of P91 Steel

An attempt has been made to interrelate the predicted creep-rupture properties using stress relaxation tests (SRT) with those obtained from uniaxial monotonic creep tests in P91 steel. Stress-relaxation tests were performed at specified total strain levels of 1.3 and 2.5% for fixed duration of 24 h at 873 K. The results from SRT have been used to predict the rupture life using Monkman–Grant relation and Gill–Goldhoff correlation for the steel. Further, the observed stress-relaxation behaviour has been described appropriately using an analytical model with suitable parameter values related to activation volume and activation energy.     

A simple and efficient XFEM approach for 3-D cracks simulations

In this work, a simple and efficient XFEM approach has been presented to solve 3-D crack problems in linear elastic materials. In XFEM, displacement approximation is enriched by additional functions using the concept of partition of unity. In the proposed approach, a crack front is divided into a number of piecewise curve segments to avoid an iterative solution. A nearest point on the crack front from an arbitrary (Gauss) point is obtained for each crack segment. In crack front elements, the level set functions are approximated by higher order shape functions which assure the accurate modeling of the crack front. The values of stress intensity factors are obtained from XFEM solution by domain based interaction integral approach. Many benchmark crack problems are solved by the proposed XFEM approach. A convergence study has been conducted for few test problems. The results obtained by proposed XFEM approach are compared with the analytical/reference solutions.     

Multi-walled carbon nanotube modified carbon paste electrode as an electrochemical sensor for the determination of epinephrine in the presence of ascorbic acid and uric acid

A biocompatible electrochemical sensor for selective detection of epinephrine (EP) in the presence of 1000-fold excess of ascorbic acid (AA) and uric acid (UA) was fabricated by modifying the carbon paste electrode (CPE) with multi-walled carbon nanotubes (MWCNTs) using a casting method. The electro-catalytic activity of the modified electrode for the oxidation of EP was investigated. The current sensitivity of EP was enhanced to about five times upon modification. A very minimum amount of modifier was used for modification. The voltammetric response of EP was well resolved from the responses of AA and UA. The electrochemical impedance spectroscopic (EIS) studies reveal the least charge transfer resistance for the modified electrode. The AA peak that is completely resolved from that of EP at higher concentrations of AA and the inability of the sensor to give an electrochemical response for AA below a concentration of 3.0 × 10^? 4 M makes it a unique electrochemical sensor for the detection of EP which is 100% free from the interference of AA. Two linear dynamic ranges of 1.0 × 10^? 4–1.0 × 10^? 5 and 1.0 × 10^? 5–5.0 × 10^? 7 M with a detection limit of 2.9 × 10^? 8 M were observed for EP at modified electrode. The practical utility of this modified electrode was demonstrated by detecting EP in spiked human blood serum and EP injection. The modified electrode is highly reproducible and stable with anti fouling effects.     

Volume estimation in dialysis patients: The concordance of brain‐type natriuretic peptide measurements and bioimpedance values

Correct estimation of the dialysis patients' hydration status remains an important clinical challenge. Bioimpedance measurements have been validated by various physiological tests, and the use of brain‐type natriuretic peptide (BNP) has been validated by inferior vena cava diameter measurements. This is an observational cohort study that evaluated the correspondence between bioimpedance‐measured overhydration percentage (OH%) and BNP. We measured predialysis OH% by bioimpedance apparatus (Body Composition Monitor) and BNP by microparticle enzyme‐linked immunoassay in 41 prevalent stable hemodialysis patients, 19 (46%) women, aged 58.9 ± 14.5 years. The cohort's average BNP was 2694 ± 3278 pg/mL and 10 (24.4%) of these 41 patients had BNP < 500 pg/mL (average 260.7 ± 108.5). The OH% was 8.5 ± 7.0% among those with a BNP < 500 pg/mL, while the rest of the population had an OH% of 21.4 ± 8.0%, corresponding to excess volumes of 1.6 ± 1.3 and 4.4 ± 3.8 L, respectively. The OH% vs. BNP relationship was best described by the exponential regression of y = 216.4e^0.097x, predicting a BNP of 216.4 pg/mL at 0% overhydration status (r 0.61). Receiver‐operating curves revealed an area under the curve of 0.885 for BNP when the OH% was set ≥15% of overhydration and an area under the curve of 0.918 for OH% when the BNP was set ≥500 pg/mL for being abnormal. We conclude that in our cohort there was a high degree of correspondence between these two tests with an exponential relationship between the measurements.     

Failure Analysis of Spline Shaft in Beco Lathe

The failure of Heavy Duty Facing Lathe has been systematically investigated using fractographic, metallographic, and analytical stress analysis methods. Failure occurred during machining of a large flange, the tool post had a collision with jaw of the rotating chuck and the spline shaft inside headstock was broken into two pieces. A detailed analysis of the fracture surfaces revealed partial damage of the surfaces due to their rubbing in operation and cleavage fracture in the remaining part of the surfaces. The stress analysis indicates that sudden reversing of the spindle had resulted in the stresses exceeding the fatigue limit of the shaft material. These stresses led to the formation of microcracks at the circlip groove. The collision accelerated the sudden failure of shaft. This failure analysis has led to identification of root cause and its elimination with corrective measures undertaken.     

Phase Evolution and Densification Behavior of Nanocrystalline Multicomponent High Entropy Alloys During Spark Plasma Sintering

In the current study, the phase evolution of multicomponent equiatomic CoCrCuFeNi, CoCuFeNi, CoCrCuNi, and CoCrFeNi alloys synthesized by mechanical alloying (MA) followed by annealing was studied. From the phase evolution studies, CoCrFeNi, CoFeMnNi, CoCuFeNi, and CoFeNi were chosen to correlate the densification together with phase evolution during spark plasma sintering (SPS). MA resulted in a major face centered cubic (fcc) phase and a minor body centered cubic (bcc) phase in Cr-containing alloys, and a single fcc phase in all other alloys. After SPS, CoFeMnNi and CoFeNi remained as single fcc phase. However, CoCuFeNi transformed to two fcc phases, and CoCrFeNi had a major fcc phase with minor sigma phase. From densification studies, it was evident that CoCrFeNi showed delayed densification, albeit maximum final densification in comparison to other alloys. This behavior was attributed to distinctly different phase evolution in CoCrFeNi during SPS as compared to other alloys. Detailed phase evolution studies were carried out on CoCrFeNi by annealing the powders at different temperatures followed by conventional x-ray diffraction (XRD) and in situ high-temperature XRD of mechanically alloyed powders. The results obtained from the annealing and in situ high-temperature XRD studies were correlated with the densification and alloying behavior of CoCrFeNi alloy.