INFLUENCE OF DIE ANGLES ON THE MICROHARDNESS OF ALUMINUM ALLOY PROCESSED BY EQUAL CHANNEL ANGULAR PRESSING

The die geometry has a massive effect on the plastic deformation behavior during pressing of material processed by equal channel angular pressing (ECAP) method; subsequently the properties of the processed material are strongly dependent on it. Two categories of designed and manufactured dies are used for equal channel angular pressing, a 1200 sharp angle and a 900 round –cornered (200) dies, that produce strain per pass through both dies of ~0.7 and ~1.05 respectively. The microhardness developed in Al-Si alloy during ECAP using route BC. The microhardness increased by a factor of >1.5, after only 1 pressing. Subsequently, the hardness increases slightly up to 8 pressings through the 1200 sharp angle die, while it is increased by a factor of ~2.6 after 5 passes by using the 900 round cornered die, comparing with that for the cast workpiece.

Certification of NIST Standard Reference Material 640d

The National Institute of Standards and Technology (NIST) certifies a variety of standard reference materials (SRM) to address specific aspects of instrument performance for divergent beam diffractometers. This paper describes SRM 640d, the fifth generation of this powder diffraction SRM, which is certified with respect to the lattice parameter. It consists of approximately 7.5 g silicon powder specially prepared to produce strain-free particles in a size range between 1 and 10 μm to eliminate size-broadening effects. It is typically used for calibrating powder diffractometers for the line position and line shape. A NIST built diffractometer, incorporating many advanced design features, was used to certify the lattice parameter of the silicon powder measured at 22.5 °C. Both type A, statistical, and type B, systematic, errors have been assigned to yield a certified value for the lattice parameter of a=0.543 159±0.000 020 nm.

Transverse-Isotropic Elastic and Viscoelastic Solids

A set of invariants are presented for transverse-isotropic materials whose gradients produce strain fields, instead of deformation fields as is typically the case. Finite-strain theories for elastic and K-BKZ-type viscoelastic solids are derived. Shear-free and simple shearing deformations are employed to illustrate the constitutive theory.

Effect of Plasticity on Fatigue Life of Welded Nuclear Component With Local Brittle Zone

The local brittle zone (LBZ), which has lower tensile properties as well as lower fracture toughness than base metal and weldment, can occur on the heat affected zone (HAZ) of some nuclear components made of low alloy steels due to the carbide coarsening by multi-pass welding and post-weld heat treatment. These variations of material strengths across the welds due to the LBZ can produce strain concentrations when the stress amplitude is large enough to cause cyclic plastic flow. But, it is difficult to find the previous researches about a relation between the fatigue life of LBZ on real nuclear components and plasticity. So, in this study, the microstructures and tensile properties of HAZ on nuclear components are predicted by using the semi-analytical method, and the fatigue lifetimes of welds on nuclear components with the LBZ are evaluated by the finite element method considering the local plasticity and the variations of tensile properties, and the fatigue analysis procedure of ASME B&PV Code Sec.III. Finally, the effect of LBZ on nuclear components on fatigue lifetime is reviewed.

Sinorhizobium fredii and Sinorhizobium meliloti Produce Structurally Conserved Lipopolysaccharides and Strain-Specific K Antigens

ABSTRACT Lipopolysaccharides (LPS) and capsular polysaccharides (K antigens) may influence the interaction of rhizobia with their specific hosts; therefore, we conducted a comparative analysis of Sinorhizobium fredii and Sinorhizobium meliloti, which are genetically related, yet symbiotically distinct, nitrogen-fixing microsymbionts of legumes. We found that both species typically produce strain-specific K antigens that consist of 3-deoxy-d-manno-2-octulosonic acid (Kdo), or other 1-carboxy-2-keto-3-deoxy sugars (such as sialic acid), and hexoses. The K antigens of each strain are distinguished by glycosyl composition, anomeric configuration, acetylation, and molecular weight distribution. One consistent difference between the K antigens ofS. fredii and those of S. meliloti is the presence of N-acetyl groups in the polysaccharides of the latter. In contrast to the K antigens, the LPS ofSinorhizobium spp. are major common antigens. Rough (R) LPS is the predominant form of LPS produced by cultured cells, and some strains release almost no detectable smooth (S) LPS upon extraction.Sinorhizobium spp. are delineated into two major RLPS core serogroups, which do not correspond to species (i.e., host range). The O antigens of the SLPS, when present, have similar degrees of polymerization and appear to be structurally conserved throughout the genus. Interestingly, one strain was found to be distinct from all others: S. fredii HH303 produces a unique K antigen, which contains galacturonic acid and rhamnose, and the RLPS did not fall into either of the RLPS core serogroups. The results of this study indicate that the conserved S- and RLPS of Sinorhizobiumspp. lack the structural information necessary to influence host specificity, whereas the variable K antigens may affect strain-cultivar interactions.

Job-Stress Worker-Strain Relationship Moderated by Off-the-Job Experience

The present study examined the role that off-the-job stressors play in the job-stress worker-strain relationship. A sample of 72 managers was administered a social readjustment scale for life-stress off the job, a job-stress rating scale, and measures of job satisfaction, depressed mood, psychosomatic complaints, and severity of physical illness. Analysis indicated that stressors combine in a multiplicative fashion to produce strain for workers; only the combined and interacting pressures of nonwork stress and work stress created strain in the worker. The application of these findings in the industrial setting is discussed; suggestions are made concerning the possibility that some factors in off-the-job experience buffer the individual from stress at work.

Strain Induced Potentials on a 'Dirty' Polycrystalline Surface

General considerations are given as to the nature of five mechanisms which can produce strain induced potentials on a metal surface. Some experimental evidence is included. This is of interest in the question of the strain dependence of contact potential, and may be of interest in the metallurgy of surfaces.