Possibilities to Use Physical Simulations When Studying the Distribution of Residual Stresses in the HAZ of Duplex Steels Welds

Dual phase steels combine very good corrosion resistance with relatively high values of mechanical properties. In addition, they can maintain good plastic properties and toughness at both room temperature and lower temperatures as well. Despite all the advantages mentioned above, their utility properties can be reduced by technological processing, especially by the application of the temperature cycles. As a result, in the material remain residual stresses with local stress peaks, which are quite problematic especially during cyclic loading. Moreover, determining the level and especially the distribution of such residual stresses is very difficult for duplex steels both due to the structure duality and in light of the very small width of the heat-affected zone (HAZ). This is why the paper presents the possibilities of using physical simulations to study the effect of temperature cycles in residual stresses’ magnitude and distribution, where it is possible to study the HAZ in more detail as well as on a much larger sample width due to the utilization of special samples. In the thermal–mechanical simulator Gleeble 3500, temperature-stress cycles were applied to testing samples, generating stress fields with local peaks in the testing samples. In addition, the supplied steel X2CrMnNiN21-5-1 had different phase rations in the individual directions. Therefore, as the residual stresses were measured in several directions and at the same time, it was possible to safely confirm the suitability of the used measurement method. Moreover, the effect of the stress and strain on the change of partial phases’ ratios was observed. It has been experimentally confirmed that annealing temperatures of at least 700 °C are required to eliminate local stress peaks after welding. However, an annealing temperature of 550 °C seems to be optimal to maintain sufficient mechanical properties.

Engineering of defects in fast neutron irradiated synthetic diamonds

Chemical vapor deposited (CVD) diamonds have been irradiated with fast reactor neutrons at fluencies F = 1·1018 and 3 · 1018 cm-2 and then heated at temperatures up to 1600 °C. The processes of annealing in and annealing out of various complexes of intrinsic defects responsible for vibrational and electron-vibrational bands in the IR absorption spectra have been studied in detail. Some tens of local vibrational modes and zero-phonon lines with rather small width caused by numerous complexes of intrinsic defects were observed in the 400-11000 cm-1 range.

THE INFLUENCE OF THE STABILITY OF BAND SAWS ON THE QUALITY INDICATORS OF SAW PRODUCTS

The main drawback of circular sawing machines is the presence of broken teeth in the cut. In case of vibrations, violation of the saw plane, mismatch of the feed direction with the saw planes, and rebasing, these teeth spoil the processing surface. Belt sawing allows you to ensure high quality of lumber on the roughness of their surface at high feed rates; increase productivity by 1.5-2 times due to mechanization and automation of technological operations. One of the most important advantages of band saws is the small width of the cut, which is 1.5-2 times smaller than that of the sawmill; the small thickness of the saw ensures low consumption of wood in sawdust and high volume output of lumber. Sawing wood on band saws, in the vast majority of cases, is characterized by face cutting. Of the 3 forms of chip formation when cutting into the end, for band saws, the most characteristic is the formation of the chip element by chipping it with the stratification of wood along the bottom of the cut. The quality of the surface, in terms of its roughness, in addition to the formation of the chip element, is affected by its location in the interdental space, the presence and degree of compression and transportation of the chip element. The quality of the surface, in terms of its roughness, in addition to the formation of the chip element, is affected by its location in the interdental space, the presence and degree of compression and transportation of the chip element. As a result of studies of the initial conditions for the development of the teeth sharpening scheme, the orientation of the active elements of the blade relative to the middle plane of the saw can be identified as the main ones.

The SWISS IOL Technique (Small-Width Incision Scleral Suture): A Mini-Invasive Technique

Purpose. To evaluate the outcomes and safety of a minimally invasive technique for sutured IOL scleral fixation in case of compromised capsular and iris support. Materials and Methods. In this retrospective study, we explain our mini-invasive technique and assess the outcomes in terms of visual acuity, pre- or postoperative complications, and IOL position (Sensar AR40e, AMO) in a case series of three patients. Results. The expected best corrected visual acuity could be achieved after one month. Surgeries were uneventful with a stable eye. No postoperative complications occurred except for one patient who had a conjunctival disinsertion. Neither postoperative hypotony nor raised IOP was found. Additionally, no patient experienced corneal edema at one week control, IOL dislocation, vitreous hemorrhage, or new pupil’s irregularity. Conclusions. In conclusion, each scleral technique has its own advantages and its inherent postoperative complications. To date, there is no evidence of superiority of any single technique. By improving our scleral sutured lens techniques, we could improve peroperative ocular stability, potentially decrease postoperative complication rate, and offer a rapid recovery with a stable visual acuity within a month.

Analysis of metothods determining the value of the flow’s speed when entering the lock chamber

The purpose of this work is to compare the results of calculating the velocities of the flow around the ship's hull when it enters the lock chamber using various methods. The article presents the mathematical dependences obtained by various authors in the course of their research depending on the coefficient of constraint of the lock chamber by the ship's hull. An attempt to determine the influence of the height of the wave that arises in front of the stem in the process of entry which creates a slope of the water surface and the effect of this factor on the speed of the flowing stream is made. It was found that the values ​​of the flow velocities calculated by various methods have discrepancies. And the methods themselves do not allow determining the speed of the flow around when large-tonnage vessels enter the lock chamber of an extremely small width. The authors proposed a simple technique for calculating the flow velocity for cases of large values ​​of the constraint coefficient using an auxiliary graph.

Transpedicular fixation of the spine with two-level navigation templates for narrow pedicles

Objective. To assess the correctness of transpedicular screw insertion in thoracic and lumbar vertebrae using two-level navigation templates for narrow pedicles.Material and Methods. Two-level navigation templates were used in surgical treatment of four patients aged 14–17 years with scoliotic deformity and multiple pedicles of small width (less than 4.35 mm). In each patient, the least favorable zones were selected for implantation using navigation templates. The rest of planned pedicle screws were inserted using free-hand technique. All patients underwent CT scanning postoperatively. Screws inserted to pedicles less than 4.35 mm in width were classified as correctly placed if they did not extend beyond the medial cortical layer by more than 2 mm.Results. Out of 68 pedicles planned for screw placement, 42 were narrower than 4.35 mm. In the pedicles difficult for implantation, 29 screws were inserted using navigation templates and 13 by free-hand technique. Screws classified as correctly placed were 28 from those inserted with navigation templates and 9 from those implanted by free-hand technique. Difference in results of screw placement in narrow pedicles with navigation templates and by free-hand technique was statistically significant (exact Fisher test, p < 0.05).Conclusion. Transpedicular screw placement with two-level navigation templates in narrow pedicles is more correct than insertion by free hand technique.

Influence of surgically assisted rapid maxillary expansion on the interdental papilla height of maxillary central incisors

Purpose To evaluate the influence of orthodontic treatment with surgically assisted rapid maxillary expansion (SARME) on the interdental papilla height of maxillary central incisors. Methods In this retrospective study, patients who completed orthodontic treatment including SARME at the Radboud University Medical Center Orthodontic Department before December 2019 were included. Frontal intraoral photographs taken before (T1) and after completion of treatment (T2) were examined to determine the papilla height between the maxillary central incisors using the Jemt classification. The difference between the Jemt classification at T1 and T2 (∆Jemt) was defined as the primary outcome variable. Secondary outcome variables were gender, age, treatment duration, type of expansion appliance, maximal central diastema during expansion, pretreatment overlapping between the central incisors, gingival biotype, crown morphology and the distance between the bone crest and incisal contact point. Kappa statistics and paired t‑tests were used to determine reliability of the measurements. Pearson’s Χ2 test and independent t‑tests were used to compare the variables between the groups of patients with and without papillary recession. Finally, multiple logistic regression analysis was performed. Results In all, 93 patients fulfilled the inclusion criteria and were included in the study. The Jemt score worsened for 30 patients (32%) between T1 and T2, indicating the occurrence of papillary recession. Incisal overlapping, crown morphology, small width to length ratio, increasing age and an increasing distance between crestal bone and the incisal contact point were factors associated with papillary recession. Conclusion After orthodontic treatment including SARME, one third of patients exhibited recession of papilla height of the maxillary central incisors.

Flow in groovy curved channels with thin gap

A pressure-driven viscous flow through groovy curved channels of small width compared to the groove wavelength is studied. The Reynolds number is assumed to be very small, such that the flow is dominated by the viscous and the pressure-gradient forces. The effects of the channel geometry on the inertial free flow are analyzed. Two distinct flow directions are considered: (i) flow transverse to the grooves and (ii) flow longitudinal to the grooves. The velocities for both flow directions are obtained, and their distributions are found to be significantly affected by the grooves and channel curvature. The axial pressure gradient for the transverse flow is examined as a function of the amplitude and the phase difference. The results further indicate that the flow rate can be increased by the grooves for longitudinal flow, irrespective of the phase difference, unlike transverse flow This is because the latter is more affected by grooves for the same radius of curvature and phase difference.