The Effect of Flow Lines on the Mechanical Properties in Hot-Rolled Bearing Steel

Hot rolling is an essential process for the shape-forming of bearing steel. It plays a significant role in the formation and distribution of flow lines. In this work, the effect of flow lines is investigated by analyzing the microstructure and mechanical anisotropy of hot-rolled bearing steel. It was found that carbides rich with Cr and Mn elements are distributed unevenly along the flow-line direction of the hot-rolled bearing steel. Moreover, the mechanical characterization indicates that ultimate tensile strength and yield strength do not have any significant difference in two directions. Nevertheless, an ultrahigh section shrinkage of 57.51% is obtained in the 0° sample that has parallel flow lines, while 90° sample shows poor section shrinkage. The uneven distributed carbides will affect the direction and speed of crack propagation during tensile deformation. Therefore, the 0° and 90° samples exhibit great difference in plastic property. Meanwhile, after tensile deformation, a delaminated texture is observed in the flow lines, which may be caused by different degrees of deformation of grains due to the uneven distribution of carbides. The results of this work may provide guidance for controlling and optimizing flow lines in the manufacturing of bearing rings.

STRUCTURAL REARRANGEMENT OF THE ORGANS OF THE NEUROIMUNOENDOCRINE SYSTEM IN CONDITIONS OF BURN DISEASE

The relevance of this study is due to the lack of special studies, the subject of which is the analysis of indicators of endogenous intoxication and structural changes in the histohematological barriers of the organs of the neuroimunoendocrine system in burn disease under conditions of its treatment by infusion of colloidal hyperosmolar solutions. It was found that changes in the permeability of the vascular wall and death of endothelial cells are of particular importance in the development of morphological changes in the adenohypophysis, adrenal cortex and thymus, which at the final stage of these reactions causes the appearance of intraorganic edema and hemorrhage characteristic of burn injury. It can be argued that there is a specific, but common for all studied organs, mechanism of transformation of histohematogenous barriers, which consists in the formation, under the influence of Lactoprotein-C, of a structured, branched, membrane-like complex in a certain way. Its components provide not only strengthening of the vascular wall, but also the isolation of cell clusters. So, the data obtained indicate not the restoration of the structure of histohematogenous barriers, but their structural transformation, which leads to the appearance of a new formation - a membranelike complex, which effectively provides the necessary barrier function. The leading factor of damage to histohematogenous barriers in the studied organs in burn disease is a wide range of morphofunctional changes in the vascular endothelium, which cause the formation of through transmural defects in the wall of blood vessels and the corresponding intraorgan intercellular expansions, the marker of which is the electron-dense Lactoprotein-C. Lactoprotein-C and HAES-LX-5% under conditions of burn disease develop cyto- and angioprotective effects, inhibit the development of hemorrhages, edema, prevent alteration of cells of the adenohypophysis, adrenal cortex and thymus and promote organ repair. Lactoprotein-C is characterized by the first described membrane-plastic property, which ensures the implementation of a specific mechanism of structural transformation of histohematogenous barriers, namely, the creation of a branched membrane-like complex.

A Partitioning Method for Friction Stir Welded Joint of AA2219 Based on Tensile Test

The partition of aluminum alloy welded joint often depends on microscopic methods such as scanning electron microscopy before. This paper provides a novel partitioning method, which can obtain the material properties and partition results at the same time based on tensile test. The mechanical properties of every point on the whole welded joint are first obtained by the digital image correlation (DIC) method. Then, the mechanical property function of the weld joint along the weld center is established due to the changes of plastic property and strain hardening exponent at each point and the boundary between different areas is then determined. Metallographic detection technology and nano-mechanical testing techniques are employed to validate this partitioning scheme. The partition result of the strategy proposed in this paper is consistent with the partitioning result of the classical method. Compared to classical method, the proposed partitioning method is more practical and effective, as it can obtain mechanical properties and partition boundary through a single tensile test and reduce the cost of metallographic test.

Numerical Study on Inelastic Seismic Design of Piping Systems Using Damping Effect Based on Elastic–Plastic Property of Pipe Supports

This study describes inelastic seismic design of piping systems considering the damping effect caused by elastic–plastic property of a pipe support which is called an elastic–plastic support. Though the elastic–plastic support is proposed as inelastic seismic design framework in the Japan Electric Association code for the seismic design of nuclear power plants (JEAC4601), the seismic responses of the various piping systems with the support are unclear. In this study, the damping coefficient of a piping system is focused on, and the relation between seismic response of the piping system and elastic–plastic behavior of the elastic–plastic support was investigated using nonlinear time history analysis and complex eigenvalue analysis. The analysis results showed that the maximum seismic response acceleration of the piping system decreased largely in the area surrounded by pipe elbows including the elastic–plastic support which allowed plastic deformation. The modal damping coefficient increased a maximum of about sevenfold. Furthermore, the amount of the initial stiffness of the elastic–plastic support made a difference in the increasing tendency of the modal damping coefficient. From the viewpoint of the support model in the inelastic seismic design, the reduction behavior for the seismic response of the piping system was little affected by the 10% variation of the secondary stiffness. These results demonstrated the elastic–plastic support is a useful inelastic seismic design of piping systems on the conditions where the design seismic load is exceeded extremely.

Investigation of Stress-Strain Constitutive Behavior of Intermetallic Alloys

The study aims to estimate the stress-strain constitutive behavior of intermetallic compounds (IMCs) observed in a solder interconnect from experimental nanoindentation responses through a modified analysis procedure for improved solution robustness based on Cheng and Cheng's and Dao et al.'s models. On the basis of parametric finite element nanoindentation simulation and dimensional analysis together with the concept of representative strain, a set of universal dimensionless functions are established, by which a forward and reverse analysis algorithm are created to predict nanoindentation responses from given elastoplastic properties and vice versa, respectively. The proposed analysis procedure is validated through comparison with the experimental nanoindentation responses and limited literature data. The results show that the proposed analysis procedure is an effective means for plastic property characterization of micro/nanoscale IMCs. The representative strain is found to be 0.056, which differs from the Dao et al.'s and Giannakopoulos and Suresh's estimate. Besides, though generally brittle and hard in nature, the IMCs in a micro/nanoscale thickness show high plasticity, and comprise a yield strength surpassing most typical engineering metals.