The Phenomena and Criteria Determining the Cracking Susceptibility of Repair Padding Welds of the Inconel 713C Nickel Alloy

The creep-resistant casting nickel alloys (e.g., Inconel 713C) belong to the group of difficult-to-weld materials that are using for precise element production; e.g., aircraft engines. In precision castings composed of these alloys, some surface defects can be observed, especially in the form of surface discontinuities. These defects disqualify the castings for use. In this paper, the results of technological tests of remelting and surfacing by the Tungsten Inert Gas method (TIG) in an argon shield and TecLine 8910 gas mixture are presented for stationary parts of aircraft engines cast from Inconel 713C alloy. Based on the results of metallographic studies, it was found that the main problem during remelting and pad welding of Inconel 713C castings was the appearance of hot microcracks. This type of defect was initiated in the partial melting zone, and propagated to the heat affected zone (HAZ) subsequently. The transvarestraint test was performed to determine the hot-cracking criteria. The results of these tests indicated that under the conditions of variable deformation during the remelting and pad welding process, the high-temperature brittleness range (HTBR) was equal 246 °C, and it was between 1053 °C and 1299 °C. In this range, the Inconel 713C was prone to hot cracking. The maximum deformation for which the material was resistant to hot cracking was equal to 0.3%. The critical strain speed (CSS) of 1.71 1/s, and the critical strain rate for temperature drop (CST), which in this case was 0.0055 1/°C, should be used as a criteria for assessing the tendency for hot cracking of the Inconel 713C alloy in the HTBR. The developed technological guidelines and hot-cracking criteria can be used to repair Inconel 713C precision castings or modify their surfaces using welding processes.

PREPARATION AND NUMERICAL SIMULATIONS OF DRUG-LOADED HYDROXYAPATITE BIOMATERIALS

To meet the challenge of regenerating bone lost to disease or trauma, biodegradable scaffolds are being investigated as a way to regenerate bone without the need for an auto- or allograft. Herein, we prepared poly (lactic acid) (PLA)/chitosan(CS)/nano-hydroxyapatite biomaterials through solution polymerization and solvent volatilization. Cefadroxil was used as a model drug for loading on biomaterials using supercritical carbon dioxide. In addition, we investigated the in vitro drug release effect, and the in vitro release results showed that the drug could release more than 73% of the drug load within 48[Formula: see text]h. This excellent drug release property could allow continuous drug use at the wound site, further broadening its application in the medical field. A three-dimensional finite element (FE) model of bone screws was established, and the mechanical properties of the screws were numerically calculated. The stress and deformation of the bone screws under different external conditions were simulated. The bending simulation showed that the screw can withstand the maximum deformation of 0.418[Formula: see text]mm and equivalent stress of 566.94[Formula: see text]MPa at a force of 700 N. The maximum equivalent stress of the screw reached 321.84[Formula: see text]MPa, and the corresponding torque was 779.68 N[Formula: see text]mm when the torsion angle was gradually increased to 30[Formula: see text]. The fabricated material has excellent mechanical properties and can be used for bone repair. This study provides a new direction for preparing drug-loaded polymer biomaterials and developing new materials for bone repair.

Tensile Strength of Threaded Rods Made by 3D Printing of Polymeric Material

The extension of 3D printing processes for parts made of polymeric materials highlighted the possibility of manufacturing threaded surfaces through such processes. In principle, the operation of a threaded joint involves tensile forces in the threaded rod. The dimensional characteristics of the threaded surface and some input factors in the 3D printing process can influence the tensile strength of threaded rods made of polymeric materials. An experimental research aimed at the tensile behavior of a threaded joint was designed, using a plastic screw and a special steel nut. A factorial experiment was designed and implemented to identify an empirical mathematical model capable of highlighting the influence of the dimensional characteristics of the threaded surface and some of the input factors in the 3D printing process on tensile strength. The test samples from polymeric materials were manufactured by 3D printing, then subjected to tensile tests. The mathematical processing of the experimental results allowed the determination of a mathematical model that allows the inclusion of the ordering of the factors taken into account in terms of the intensity of the influence that these factors exert on the tensile strength of the threaded rods. It was found that the diameter of the threaded rod exerts the strongest influence on the tensile strength of the threaded rod obtained by 3D printing, increasing the diameter of the threaded rod causing an increase in the maximum deformation of the rod. Increasing the thread pitch leads to a decrease in the maximum deformation of the threaded rod.

Reliability Analysis and Optimization for the Brake Drum

In order to research the static and dynamic characteristics of drum brake in the braking process and avoid resonance, it is necessary to carry out static analysis and modal analysis of drum brake. By establishing the three-dimensional model of the brake drum and imported to ANSYS for static analysis, the maximum equivalent stress and maximum deformation of the brake drum are obtained. The first, second and third natural frequencies and modal vibration shapes of the brake drum are obtained by modal analysis. Four dimensional parameters are selected as design variables, and the sensitivity is carried out by using experimental design. Taking the maximum deformation, first natural frequency, second natural frequency and mass of the brake drum as the objective function, the multi-objective optimization algorithm is used to optimize the design variables. Based on the optimization design, the six sigma reliability analysis of the brake drum is carried out, and the six sigma reliability analysis method is given in detail. The cumulative distribution graph of the maximum deformation, first natural frequency, second natural frequency and mass of the brake drum are obtained. The analysis results show that the reliability of the brake drum is close to 100%, and then it is judged that the brake drum has high reliability. The research results provide a reference basis for structural reliability analysis.

Analysis of Mechanical Characteristics of Impeller of Spray Duster Based on ANSYS Workbench

The spray dustless machine is an important environmental protection equipment for harnessing haze. The booster impeller of the spray dustless machine is one of the decisive factors of the booster capacity. The stability of the blade directly determines the reliability of the spray duster. In this paper, ANSYS Workbench is used to analyze the mechanical characteristics of a certain type of spray dustless blade. The results show that: under the rated condition, the maximum equivalent stress of the impeller is 55.6Mpa, which is far less than the allowable stress of the impeller material 415Mpa, the maximum deformation of the circumferential position at the bottom of the blade is 1.2mm, and other deformation positions are mainly the outer edge of the blade, which can be optimized later. The interference frequency is far away from the vibration frequency of the first two modes, so resonance will not occur.

Repeatability and comparison of Corvis ST parameters before and after accelerated transepithelial corneal cross-linking in keratoconus eyes

AIM: To evaluate the repeatability and comparison of corneal visualization scheimpflug technology (Corvis ST) parameters in keratoconus eyes before and after accelerated transepithelial corneal cross-linking (ATE-CXL). METHODS: Thirty eyes of 30 progressive keratoconus patients were included in the prospective study. Three repeated corneal biomechanical measurements were performed preoperatively and one month postoperatively by Corvis ST. The interclass correlation coefficient (ICC) and 95% confidence interval (CI), Cronbach’ α, repeatability coefficient (RC), and coefficient of variation (CV) were used to evaluate the repeatability of Corvis ST parameters. Paired t test or Wilcoxon rank test was used to evaluate the differences between preoperative and postoperative data. RESULTS: At preoperative, 26 of 39 (66.67%) parameters showed good to excellent repeatability, 6 (15.38%) showed moderate, and 7 (17.95%) showed poor repeatability. Similarly, 34 (87.18%) parameters showed good to excellent repeatability, 3 (7.69%) showed moderate, and 2 (5.13%) showed poor repeatability after ATE-CXL. After ATE-CXL 1mo, the intraocular pressure (IOP), biomechanical corrected IOP (bIOP), first applanation time (A1T), Radius, deformation amplitude at the first applanation (A1DA), deflection length at the maximum deformation (HCDLL) and stiffness parameter at first applanation (SP A1) parameters increased, while the steep keratometry (Ks), flat keratometry (Kf), mean keratometry (Kmean), second applanation time (A2T), DA Ratio Max (2 mm) and integrated radius parameters decreased (all P<0.05). CONCLUSION: The repeatability of the Corvis ST parameters before and 1mo ATE-CXL follow up were both acceptable, and the corneal stiffness was improved after 1-month ATE-CXL.

Fluid and Structure Analysis of Wind Turbine Blade with Winglet

One of the succeeded methods to enhance the performance of horizontal axis wind turbine (HAWT) is an attaching a winglet to the blades tip. The current paper study the effect of four key parameters that are used to describe the winglet on the performance of wind turbine which are winglet height H%R, cant angle θ, twist angle β, and taper ratio Λ. A five design cases for each geometric parameters were numerically investigated using computational fluid dynamics (CFD) by ANSYS18.1 software, which totally give a twenty different response. A validation of present computational model with reference experimental results successfully carried out with maximum inconsistency of 3%. A mathematical correlation was established from the CFD results and being used in predicting the turbine power for the different winglet geometric parameters. From CFD and mathematical correlation response, the effect of H and θ were greater than β and Λ on the turbine power. The epoxy E-glass unidirectional material was selected for current study to investigate the effect of winglet on blade structure. The power increases by 2% to 30% due to adding winglet to a wind turbine blade. The maximum power increment corresponds to the design case of W6 with H= 8%R, =30°, β = 3°, and Λ = 0.8. Form the structural analysis the addition of winglet changes the stress distribution over the blade, increasing stresses at the blade root, and achieved the transfer of the maximum deformation from the blade tip to the winglet tip.

Axial Force Analysis of the Support Bracket of Pumped Storage Unit

During operation, the support bracket is the main part to withstand the axial loads of the pumped storage unit. Moreover, the effects of axial loads including the hydraulic thrust of runner flow and the weight of runner body may cause the support bracket deformation and fatigue damage. For the safe and stable operation, the simulation of the axial force and the structural analysis of the support bracket of a pumped storage unit was carried out in this paper. The CFD simulation result has revealed the variation rule of the axial force in different operating conditions. Using ANSYS Mechanical, the static stresses and deformation of support bracket with axial loads were calculated. The results release the location and variations of maximum stress and maximum deformation caused by the axial loads. By comparing the predicted maximum axial force with the admission force calculated by the structural analysis, it is found that the axial force of the researched machine is within the safe range. This study provides the reference for the safety and stable operation of the pumped storage unit.

Investigation of Twin Tunnel Deformation with Umbrella Grouting Protection & NATM Tunneling using 3D Finite Element: Case Study Cisumdawu Tunnel

Cisumdawu Tunnel is a twin tunnel 472 m long located in Sumedang. Twin tunnel construction can cause additional ground settlement and tunnel deformation. The tunnel construction method used is the New Austrian Tunneling Method (NATM) and umbrella grouting protection system. The principle of NATM is to maximize surrounding soil capacity to support its weight and balance the stresses around the tunnel. Investigation of tunnel deformation is important to know tunnel structure behavior and avoid possible failure. This research aims to know tunnel deformation and the effect of twin tunnel construction on the deformation and ground settlement. The data used such as tunnel geometry, monitoring data, pressuremeter test, and the drilling test. The 3D analysis will be performed for a single tunnel and twin tunnel using Midas GTS-NX, and monitoring data will be used for verification analysis. The 3D FEM help to model the soil condition and construction stage according to the actual condition. The analysis results show the maximum tunnel deformation that occurs from the beginning of the tunnel construction is 12.64cm. If the deformation starts to be calculated following the monitoring reading time, after the excavation at the monitoring point, the maximum deformation of the analysis results is 3.3&4.4cm, where the monitoring shows maximum deformation of 3.3&4.3cm. Through the results, it can be said that the analysis using 3D FEM with pressuremeter test parameter represents actual conditions. Twin tunnel construction side-by-side increases ground settlement and lateral tunnel deformation significantly. Hence, it shows that tunnel analysis using 3D FEM recommends for future investigation of tunnel deformation.

Analysis of Asymmetrical Deformation of Surface and Oblique Pipeline Caused by Shield Tunneling along Curved Section

The deformation of existing pipelines caused by the tunneling of a shield machine along curved sections has not been sufficiently researched, and a corresponding theoretical prediction formula is lacking. This paper derives a prediction formula for the deformation of an existing pipeline caused by shield machine tunneling along a curved section. Further, a finite difference model (FDM) corresponding to an actual project is built. Finally, the deformation of the surface and existing pipelines caused by shield machine tunneling along the curved section is analyzed. The research results show that the results of theoretical prediction, FDM calculation, and field monitoring data are consistent. In addition, the deformation of the surface and the existing pipeline are asymmetrically distributed when the shield machine tunnels along the curve section instead of symmetrically distributed (for straight line segment). When the pipeline is perpendicular to the tunnel axis, the maximum deformation position of the existing pipeline deviates from the tunnel axis by about 0.5 times the tunnel radius. In addition, as the angle β between the pipeline axis and the tunnel axis increases, the maximum deformation position of the pipeline gradually approaches the tunnel axis.