Cyclic work hardening and formation of dislocation substructures during low-cycle fatigue of tempered dual-phase steels

A C-Mn-Si dual-phase steel, containing 33.8% lath martensite of 0.45% C content (called steel 1), was tempered at 200, 460 and 650°C and designated steels J, K and L, respectively. Sheet specimens of 3 mm thickness and 10 mm gauge length pertaining to steels I, J, K and L were subjected to tensile and low cycle fatigue testing at room temperature. The steels I, K and L show cyclic softening while the steel J exhibits a small cyclic hardening. The cyclic stress response varies significantly at higher and lower applied strain amplitudes for each of the steels which has been discussed in terms of competing processes of hardening and softening during strain cycling. The value of the cyclic strain hardening exponent decreases continuously in the order steels I>J>K>L. Varied dislocation substructures form at higher and lower strain amplitudes during cyclic deformation.     

Processing map for controlling microstructure in hot working of hot isostatically pressed powder metallurgy NIMONIC AP-1 superalloy

The hot deformation behavior of hot isostatically pressed (HIP) NIMONIC AP-1 superalloy is characterized using processing maps in the temperature range 950 °C to 1200 °C and strain rate range 0.001 to 100 s^•1. The dynamic materials model has been used for developing the pro-cessing maps which show the variation of the efficiency of power dissipation given by [2m/ (m + 1)] with temperature and strain rate, withm being the strain rate sensitivity of flow stress. The processing map revealed a domain of dynamic recrystallization with a peak efficiency of 40 pct at 1125 °C and 0.3 s^•1, and these are the optimum parameters for hot working. The microstructure developed under these conditions is free from prior particle boundary (PPB) de-fects, cracks, or localized shear bands. At 100 s^•1 and 1200 °C, the material exhibits inter-crystalline cracking, while at 0.001 s^•1, the material shows wedge cracks at 1200 °C and PPB cracking at 1000 °C. Also at strain rates higher than 10 s^•1, adiabatic shear bands occur; the limiting conditions for this flow instability are accurately predicted by a continuum criterion based on the principles of irreversible thermodynamics of large plastic flow.     

Transient acoustic cavitation in gallstone fragmentation: a study of gallstones fragmented in vivo

The mechanism of gallstone fragmentation by shock waves in vivo is uncertain. We used scanning electron microscopy to study 9 partially fragmented stones obtained from 6 patients who underwent lithotripsy and subsequently had surgery because of incomplete fragmentation. Surface characteristics of the stone were studied using scanning electron microscopy and compared to gallstones fragmented in degassed water in vitro and to control stones obtained from patients with uncomplicated cholelithiasis. Characteristic damage caused by transient acoustic cavitation was visible in all stones fragmented in vivo and in vitro as pits 10-100 microns diameter. In these pits, cholesterol crystals were fractured, and the symmetry of crystal boundaries was damaged. In areas of more severe damage, individual pits coalesced to form craters on the stone surface. High magnification of the pit walls revealed cracks, which in some instances radiated out onto the unpitted surface of the stone. We conclude that transient acoustic cavitation plays a role in gallstone fragmentation in vivo through the mechanism of surface pitting and the formation of cracks that radiate outward from the surface pits. Measures to enhance cavitation may improve the results of gallstone lithotripsy.     

Influence of pulsating magnetic field on softening behaviour of cold rolled AISI 4340 steel at room temperature

Thus it may be summarised that hardness of the cold rolled AISI 4340 steel is lowered due to exposure in alternating magnetic field of 942 Oe, at room temperature. The results are discussed in terms of vibrational effect and increased mobility of dislocations and their consequent rearrangement to offer less resistance to deformation.     

Optimization of Oxidation Temperature for Commercially Pure Titanium to Achieve Improved Corrosion Resistance

Thermal oxidation of commercially pure titanium (cp-Ti) was carried out at different temperatures, ranging from 200 to 900 °C to achieve optimum corrosion resistance of the thermally treated surface in simulated body fluid. Scanning electron microscopy, x-ray diffraction, Raman spectroscopy and electrochemical impedance spectroscopy techniques were used to characterize the oxides and assess their protective properties exposed in the test electrolyte. Maximum resistance toward corrosion was observed for samples oxidized at 500 °C. This was attributed to the formation of a composite layer of oxides at this temperature comprising Ti₂O₃ (titanium sesquioxide), anatase and rutile phases of TiO₂ on the surface of cp-Ti. Formation of an intact and pore-free oxide-substrate interface also improved its corrosion resistance.     

Effects of probiotic and prebiotic supplementation on metabolic parameters,liver aminotransferases,and systemic inflammation in nonalcoholic fatty liver disease: A randomized clinical trial

This study aimed to evaluate the clinical efficacy of probiotic and prebiotic supplementation on the metabolic parameters, liver enzymes, and inflammation in patients with nonalcoholic fatty liver disease (NAFLD). In this study, patients with NAFLD were assigned to receive either probiotic capsule + placebo of prebiotic (probiotic group), oligofructose + placebo of probiotic (prebiotic group), or placebo of probiotic + placebo of prebiotic (control group) for 12 weeks. All participants followed a weight loss diet and physical activity recommendation during intervention. Anthropometric measurements decreased in all three groups, but there was no significant difference among groups. Probiotic supplementation was able to decrease triglyceride, alanine aminotransferase (ALT), aspartate aminotransferase (AST), γ-glutamyltransferase (GGT), and alkaline phosphatase compared to control group. The serum levels of triglyceride, total and low-density lipoprotein cholesterol, ALT, AST, and GGT differed significantly in prebiotic group in comparison to the placebo. High-sensitive C-reactive protein significantly decreased within all groups; however, there was no significant difference among groups after intervention. Probiotic and prebiotic may be beneficial in improving liver enzymes and lipid profile in patients with NAFLD.     

A Comparative Study of Ratcheting Fatigue Behavior of Modified 9Cr–1Mo Steel and Inconel 617 Alloy at Homologous Temperature of 0.42

The modified 9Cr–1Mo steel and Inconel (IN) 617 superalloy are high-temperature alloys of prime importance in several industrial applications. Both of these are used at elevated temperature for various piping and tubing components and undergo asymmetric cyclic loading; therefore, it is highly essential to assess their resistance to accumulation of inelastic strain (ratcheting) under asymmetric stress cycling. In this study, ratcheting behavior of these alloys is compared at the homologous temperature of 0.42, under uniaxial asymmetric stress loading with positive mean stress. Deformation behavior of the tested samples is analyzed by transmission electron microscope. While there is homogeneous deformation in the modified 9Cr–1Mo steel, there is intersection of slip bands and presence of dislocation tangles in the IN 617 alloy. Fracture surface of the modified 9Cr–1Mo steel, tested under asymmetric cyclic loading, reveals typical ductile fracture resulting from tensile loading, whereas there is characteristic fatigue fracture of the IN 617 alloy.     

A comparative evaluation of low cycle fatigue behavior of conventional and modified INCONEL 718

Structural stability of the Inconel 718 is reported to enhance at temperatures above 650°C, with increase in Al/Ti and Al + Ti/Nb atomic ratios. However, no report is available on low cycle fatigue behavior of the modified compositions of the Inconel 718. The present investigation deals with comparative study of LCF behavior of the conventional and modified 718 with Al + Ti/Nb ratios of 0.294 and 0.459 respectively at 650°C. It was observed that fatigue life of the modified alloy, in terms of Coffin-Manson relationship was higher than that of the conventional one.     

States,Cultures, and Community Organizing: Two Tales of Two Neighborhoods

How do differences between the United States and Canadian political systems affect community organizing? We compare case studies of two neighborhoods: the Drouillard Road neighborhood in Windsor, Ontario, Canada; and the Birmingham neighborhood in Toledo, Ohio, United States. Toledo and Windsor are similar in important ways, with both heavily dependent on Detroit‐based automotive industry, and relatively similar in ethnic and class makeup. The neighborhoods also have similar demographic profiles with a high proportion of Eastern European immigrants and Catholics. Both neighborhoods witnessed threats to their existence in the 1970s, developed an energetic community organizing response to those threats, and then went separate directions. Drouillard Road quickly moved into social services and community development. Birmingham expanded its community organizing across the east side of Toledo, but then was torn apart by internal conflict when it shifted to community development. Our analysis shows that the contrasting paths of the two organizations can be more fully understood in light of national differences in political structure and political culture between Canada and the United States.