The service life increasing of bushings by electro-acoustic spraying

The control of obtaining the predicted physico-mechanical properties of protective coatings of machine parts in a complex acoustic field by the method of electroacoustic spraying is carried out through the use of highly concentrated sources of electrical energy. The prediction of the physico-mechanical properties of the hardened surface of machine parts is made on the basis of the experiment planning methodology with non-orthogonal planning matrices. The adequacy of the obtained mathematical models was carried out using the criterion of adequacy of Fisher. Physical fundamentals of mass transfer of materials to a substrate in a complex acoustic field, realized through the transformation of longitudinal vibrations, to longitudinal-torsional, have been developed, while the amplitude of oscillation of the acoustic system is 5 to 15 micrometers. The use of longitudinal-torsional ultrasonic waveguides in this process and ultrafast cooling temperatures make it possible to form elements such as carbides, carbonitrides, and intermetallic compounds on the surface of a conductive material. The subsequent impact with a shift against the surface produced by the waveguide - electrode leads to irreversible microplastic deformations of the surface layer, which provide the specified parameters of surface quality and its physico-mechanical properties.

THE STRUCTURE FORMATION OF RAPIDLY SOLIDIFIED FOIL OF THE EUTECTIC ALLOY SN-8,8 WT. % ZN

Представлены результаты исследования микроструктуры быстрозатвердевшей фольги эвтектического сплава Sn - 8,8 мас.% Zn поверхностей A и B, определены параметры микроструктуры. Проведено исследование текстуры выделений твёрдых растворов олова и цинка в фольге, представлены полюсные плотности дифракционных линий данных фаз. Изучено влияние сверхбыстрого охлаждения на распределение углов разориентации соседних и случайно выбранных зёрен для поверхностных слоёв фольги, контактирующих с подложкой () и атмосферой () соответственно. The results are presenred of a study of the microstructure of rapidly solidified foil of the eutectic alloy Sn - 8,8 wt.% Zn A and B surfaces, microstructure parameters are determined. The texture of the precipitates of tin and zinc solid solutions in the foil was studied, and the pole densities of the diffraction lines of these phases are presented. The effect is studied of ultrafast cooling on the distribution of misorientation angles of neighboring and randomly selected grains for surface foil layers in contact with surfaces A and B .

Ultrafast Hypothermia Selectively Mitigates the Early Humoral Response After Cardiac Arrest

Background Total liquid ventilation (TLV) has been shown to prevent neurological damage though ultrafast cooling in animal models of cardiac arrest. We investigated whether its neuroprotective effect could be explained by mitigation of early inflammatory events. Methods and Results Rabbits were submitted to 10 minutes of ventricular fibrillation. After resuscitation, they underwent normothermic follow‐up (control) or ultrafast cooling by TLV and hypothermia maintenance for 3 hours (TLV). Immune response, survival, and neurological dysfunction were assessed for 3 days. TLV improved neurological recovery and reduced cerebral lesions and leukocyte infiltration as compared with control (eg, neurological dysfunction score=34±6 versus 66±6% at day 1, respectively). TLV also significantly reduced interleukin‐6 blood levels during the hypothermic episode (298±303 versus 991±471 pg/mL in TLV versus control at 3 hours after resuscitation, respectively), but not after rewarming (752±563 versus 741±219 pg/mL in TLV versus control at 6 hours after resuscitation, respectively). In vitro assays confirmed the high temperature sensitivity of interleukin‐6 secretion. Conversely, TLV did not modify circulating high‐mobility group box 1 levels or immune cell recruitment into the peripheral circulation. The link between interleukin‐6 early transcripts (<8 hours) and neurological outcome in a subpopulation of the previously described Epo‐ACR‐02 (High Dose of Erythropoietin Analogue After Cardiac Arrest) trial confirmed the importance of this cytokine at the early stages as compared with delayed stages (>8 hours). Conclusions The neuroprotective effect of hypothermic TLV was associated with a mitigation of humoral interleukin‐6 response. A temperature‐dependent attenuation of immune cell reactivity during the early phase of the post–cardiac arrest syndrome could explain the potent effect of rapid hypothermia. Registration URL: https://www.clinicaltrials.gov ; Unique identifier: NCT00999583.

Microstructure and Strengthening/Toughening Mechanisms of Heavy Gauge Pipeline Steel Processed by Ultrafast Cooling

Heavy gauge pipeline steels experience a low qualification in drop-weight-tear test properties because of the low cooling capability of conventional thermomechanical controlled processing. To solve this problem, a new-generation thermomechanical-controlled processing technology based on ultrafast cooling was applied to prepare heavy gauge pipeline steels. The microstructure, strengthening and toughening mechanisms of 25.4 mm X70 and 22 mm X80 pipeline steels that were processed by ultrafast cooling were studied. The microstructures of the 25.4 mm X70 and 22 mm X80 pipeline steels consisted of bainitic ferrite, M-A island and acicular ferrite with a large fraction above 85%. The grain size and high-angle grain boundary fraction of X70 pipeline steel were 2.7 μm and 43%, respectively, whereas those of the X80 pipeline steel were 2.4 μm and 45%, respectively. The strengthening and toughening mechanisms were studied for the ultrafast cooling method. The main strengthening mechanism for 25.4 mm X70 pipeline steel was solution and grain-refining strengthening and precipitation strengthening with contributions of ~456 MPa and ~90.5 MPa, respectively. In the 22 mm X80 pipeline steel, the main strengthening mechanism was the solution and grain-refining strengthening, and dislocation strengthening with contributions of ~475 MPa and ~109.8 MPa, respectively.