Failure Analysis of HAZ Cracking in Low C–CrMoV Steel Weldment

This case study describes the failure analysis of steel nozzle in which cracking was observed after a circumferential welding process. The nozzle assembly was made from low C–CrMoV alloy steel that was subsequently single pass butt welded using gas tungsten arc welding. No cracks were found in visual inspection of the welds; however, X-ray radiography showed small discontinuous cracks on the surface in the area adjacent to weld bead, i.e. heat affected zone. The welding of nozzle parts made of same material was a routine process and this type of cracking did not occur in the past. Therefore, it became essential to determine the root cause of the failure. A detailed investigation including visual examination, non-destructive testing, optical microscopy, microhardness measurements and residual stress measurements were carried out to find out the primary cause of failure and to identify actions required to avoid its reoccurrence in future. Results of the investigation revealed that the principal cause of failure was the presence of coarse untempered martensite in the heat affected zone due to localized heating. The localized heating was caused by high welding heat input or low welding speed and resulted in the high transformation stresses. These transformation stresses combined with the thermal stresses and the constraint conditions to cause intergranular brittle fracture.     

Hydro-mechanical loading and compressibility of fibrous media for resin infusion processes

The modelling of composite manufacturing processes where hydro-mechanical coupling takes place depends on the validity of compressibility and permeability models. In this work, the computer code initially used to simulate the effect of coupled hydro-mechanical load on composite preform (Ouahbi et al. Composites Part A, 38:1646–1654, 2007) is integrated into an inverse method to predict the compaction behaviour of the reinforcements. An experimental device developed at Le Havre is used to apply hydro-mechanical loads to the preforms. Two ramps of stress are imposed to the preform and the thickness evolution is measured as a function of time. The speed of thickness reduction is not constant and varies in the range of 0.1 to 12 mm/min. The effect of compression speed upon the saturated fabrics is investigated. For a fixed fibre volume fraction, an increase in stress is observed in increasing compression speed. The experimental results are compared to the compressibility curves determined by an inverse method. The calculated curves correspond to the compressibility curves experimentally obtained with low compression speed (～0.25 mm/min). As a consequence, this suggests that a low compression speed should be applied when investigating the compressibility behaviour of composite preform with a view of modelling resin infusion processes.     

Wrinkle free plaited knitted fabrics without pre-heat setting

Wrinkle free fabric at low cost is always a desirable aesthetic property. Different type of resins/finishes and pre-heat setting prior to processing are applied to avoid wrinkles in woven and hosiery, respectively. Current study is proposed to produce wrinkle free circular plaited knitted fabric by the elimination of a pre-boarding step. In this achievement, yarn covering parameters and compatibility of yarns with knitting machines are examined. Sock samples were analyzed for improved physical appearance (wrinkles) after various processes (pre-tumbling, dyeing, bleaching, and washing). Yarn specifications (sheath yarn fineness, sheath yarn texture i.e. shrink/un-shrink, covering air-knots) impact on socks physical appearance were also analyzed. The results clearly showed that by decreasing number of yarn covering air knots and sheath yarn fineness leads to prevention of wrinkle formation. The results also prove to be supportive for cost effectiveness by eliminating the pre-setting stage.     

Short communication: Molecular characteristics,antimicrobial susceptibility,and pathogenicity of clinical Nocardia cyriacigeorgica isolates from an outbreak of bovine mastitis

The occurrence of nocardial mastitis, mostly in the context of outbreaks, has been reported in many countries. However, there is a paucity of reports regarding detailed characterization of Nocardia cyriacigeorgica from bovine mastitis. Thus, herein we report characteristics, antimicrobial susceptibility patterns, molecular identification, and pathogenicity of N. cyriacigeorgica isolated from an outbreak of clinical mastitis in a dairy herd in northern China. A total of 182 (80.2%) lactating cows had clinical mastitis with severe inflammation and firmness of the udder, reduced milk production, and anorexia, with no apparent clinical response to common antibiotics. Out of 22 mastitic milk samples submitted to our laboratory, 12 N. cyriacigeorgica were isolated and characterized using standard microbiological analysis, 16S rRNA gene sequencing, random amplified polymorphic DNA PCR analysis, biochemical assays, and antibiotic susceptibility testing. Additionally, in vivo experiments were done to determine pathogenicity of these clinical mastitis isolates. All isolates were resistant to ampicillin, amoxicillin-clavulanic acid, ciprofloxacin, minocycline, rifampicin, and aminoglycosides (type VI pattern). Additionally, intramammary inoculation of mice with N. cyriacigeorgica caused chronic inflammatory changes, including hyperemia, edema, and infiltration of lymphocytes and neutrophils, as well as hyperplasia of lymph nodules in mammary glands. Therefore, we concluded that N. cyriacigeorgica was involved in the current outbreak of mastitis. To our best knowledge, this is the first report to characterize N. cyriacigeorgica isolated from cases of bovine mastitis in China.     

Carbon nanotubes based strain sensors

This paper presents the design, fabrication and experimental results of carbon nanotubes (CNTs) based strain sensors. The sensors were fabricated by pressed CNTs tablets and elastic polymer beam. The diameter of multiwalled nanotubes (MWNTs) varied between 10 and 30 nm. The tablets of multiwalled CNTs having nominal thickness of 1.0 mm were pressed at a pressure of 200 and 300 MPa. The inter-electrodes distance (length) and width of the surface-type samples were in the range of 10–12 mm and 5–6 mm respectively. The DC resistance of the sensors having the strain sensitivity in the range of 50–80 in average increased under tension and decreased under compression.     

MRT Letter: Guided filtering of image focus volume for 3D shape recovery of microscopic objects

In this letter, a shape from focus (SFF) method is proposed that utilizes the guided image filtering to enhance the image focus volume efficiently. First, image focus volume is computed using a conventional focus measure. Then each layer of image focus volume is filtered using guided filtering. In this work, the all‐in‐focus image, which can be obtained from the initial focus volume, is used as guidance image. Finally, improved depth map is obtained from the filtered image focus volume by maximizing the focus measure along the optical axis. The proposed SFF method is efficient and provides better depth maps. The improved performance is highlighted by conducting several experiments using image sequences of simulated and real microscopic objects. The comparative analysis demonstrates the effectiveness of the proposed SFF method. Microsc. Res. Tech. 77:959–963, 2014. © 2014 Wiley Periodicals, Inc.     

Root Zone Moisture Routing and Water Demand Calculations in the Context of Integrated Hydrology

An important issue that integrated hydrologic models (IHMs) for river basins can address is the management of water resources in heavily inhabited and cultivated basins. To address this issue, these models need to simulate water demands and root zone flows in a basin. Irrigation scheduling models (ISMs) have been widely used by professionals to compute farm level water demands and root zone flows. Available ISMs are neither suitable for use at basin scale nor can they be easily linked to IHMs. This paper describes a new model that utilizes methods used by ISMs to compute root zone flows and water demands in river basins and can be linked to IHMs. The model was applied to a basin in California, and the simulated water demands were compared with data compiled for the basin. The differences in the results were attributed to differences in input potential evapotranspiration rates. The paper demonstrates that simulated water demands for rice are very sensitive to saturated soil hydraulic conductivity, whereas demands for other crops are sensitive to the pore size distribution index.     

Thermal properties,adhesive strength,and optical transparency of cyclolinear poly(aryloxycyclotriphosphazenes)

Four cyclolinear poly(aryloxycyclotriphosphazenes) derived from poly[4,4′‐(isopropoylidene)diphenoxytetrachlorocyclotriphosphazene] and poly[4,4′‐(hexafluoroisopropylidene)diphenoxytetrachlorocyclotriphosphazene] were synthesized from the reaction of hexachlorocyclotriphosphazene (HCP) with 4,4′‐(isopropylidene)diphenol (bisphenol A) or 4,4′‐(hexafluoroisopropylidene)diphenol (bisphenol AF) in molar ratio 1 : 1 via a one‐step condensation polymerization. Subsequent reaction of the resulted chlorine‐bound polymers with adequate amount of the sodium salts of 4‐methoxycarbonylphenoxide or 4‐propoxycarbonylphenoxide yielded the corresponding chlorine‐free polymers, [poly(tetra‐4‐methoxycarbonylphenoxy)‐4,4′‐(isopropoylidene)diphenoxy cyclotriphosphazene] (MBACP), [poly(tetra‐4‐propoxycarbonylphenoxy)‐4,4′‐(isopropoylidene)diphenoxycyclotriphosphazene] (PBACP), [poly(tetra‐4‐methoxycarbonylphenoxy)‐4,4′‐(hexafluoroisopropylidene)diphenoxycyclotriphosphazene] (MBAFCP), [poly(tetra‐4‐propoxycarbonylphenoxy)‐4,4′‐(hexafluoroisopropylidene)diphenoxycyclotriphosphazene] (PBAFCP), respectively. The chemical structures were characterized by Fourier transformer infrared, ¹H, and ¹³C‐NMR. Thermal properties of polymers were investigated using DSC and TGA analysis. The obtained polymers were thermoplastic, having moderate T_g values in the range of 26–78°C and good thermal stability up to 350°C in N₂ and O₂ gases. The thermal decomposition of the isopropylidene‐containing polymers is a one‐step process, while that of hexafluoroisopropylidene‐containing polymers is a two‐step process. However, presence of the latter group in the polymers backbone showed negligible effects on the thermo‐oxidative stability. The adhesive strength was measured by lap‐shear strength test on glass–glass bonded joint and found to be in the range of 1.78–2.62 MPa, this property may be attributed to the physical interactions between glass–glass interfaces and the polar‐pendant units present at the polymers backbone. The products showed high optical transparency when they applied between two glass surfaces, the adhesive layers were colorless, with the UV cut‐off wavelength of 300–302 nm, and the maximum transparency of about 90% was observed within the wavelengths range of 400–700 nm. Because of their properties, the cyclolinear poly(aryloxycyclotriphosphazenes) synthesized in this study are recommended as potential candidates for high thermally stable, transparent adhesives required in industrial applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.