Search Results (15)

This paper presents the results of a numerical study on the influence of the tooth root fillet manufacturing method on the bending strength of spur gears with straight teeth. A mathematical model describing the gear tooth geometry was developed, in which the transition curve at the tooth root was directly related to the applied machining process—either rack-type gear shaping or pinion-type gear shaping. Based on this model, a numerical procedure for calculating the bending stresses at the tooth root was formulated and verified using the finite element method (FEM). The results demonstrated high consistency between the proposed approach and FEM analysis, confirming the accuracy of the developed mathematical model and numerical methodology. The study also examined the effect of the tool fillet radius on the stress distribution in the root region. It was found that increasing the tool radius leads to a reduction in bending stresses, while the differences between the two machining methods gradually diminish. The proposed methodology offers a reliable numerical framework for assessing the strength of spur gears and can be effectively used in the design of lightweight, high-performance gear transmissions for aerospace and automotive applications. Full article

Structural optimization focusing on the root fillet radius and the crown and band thicknesses was implemented to prevent rotor–stator interaction-induced resonance, with the objective of enhancing the frequency safety margin for the 4-nodal-diameter mode shape. An ultra-high-head pump–turbine runner is analyzed using an acoustic fluid–structure coupling method to investigate modal characteristics and identify effective design improvements. The results show that increasing the root fillet radius from 0 to 50 mm raises the frequency safety margin from 3.7% to 8.5%, thereby significantly reducing the resonance risk. Likewise, increasing the thickness of the crown, the band, or both leads to higher frequency safety margins, with simultaneous thickening of both components delivering the most improvement. Frequency safety margins continue to rise as the degree of thickening increases. When a runner’s natural frequency is only slightly higher than the corresponding excitation frequency, design measures such as enlarging the root fillet radius and jointly thickening the crown and band effectively expand the frequency safety margin. These findings can provide designers with both qualitative and quantitative references when modifying these structural parameters to mitigate resonance risk. Full article

In the oil and gas pipeline industry, numerous small-diameter branch pipe fillet welds exist, which are prone to stress concentration because of diverse geometric shapes. The internal welding defects within these welds pose severe hazards to safe production. Specifically, the irregular geometry often leads to internal root defects where the weld metal fails to fully penetrate the joint or fuse with the base material (referred to as incomplete penetration and incomplete fusion). This study developed a GF-CF-GF (CF is carbon fiber, GF is glass fiber) sandwich composite reinforcement structure for pipe fittings with these specific internal defects (main pipe: Φ323.9 × 12.5 mm; branch pipe: Φ76 × 5 mm) through a combination of finite element analysis (FEA) and burst test verification. The inherent correlation between structural factors and pressure-bearing capacity was revealed by analyzing the influence of defect sizes. Based on FEA, the repair layer coverage should be designed to be within 400 mm from the defect along the main pipe wall direction and within 100 mm from the defect along the branch pipe wall direction, with required thicknesses of 5.6 mm for incomplete penetration and 3.2 mm for incomplete fusion. Analysis of the actual burst test pressure curve showed that the elastic-plastic transition interval of the repaired pipes increased by approximately 2 MPa compared to normal undamaged pipes, and their pressure-bearing capacities rose by 1.57 MPa (incomplete penetration) and 1.76 MPa (incomplete fusion). These results demonstrate the feasibility of the proposed reinforcement design, which has potential applications in the safety and integrity of oil and gas transportation. Full article

This study highlights the potential of Fourier-transform near-infrared (FT-NIR) spectroscopy for the on-site, nondestructive detection of spoilage caused by bacterial action in raw salmon (Salmo salar) fillets. A stepwise multiple linear regression model with first-derivative spectrum transformation was combined with the standard normal variate and detrend preprocessing techniques. The model achieved correlation values of 0.97 in both the calibration and validation sample sets, with root mean square error values of 0.18 and 0.20 log CFU/mL, respectively. These accurate results reveal the precision of FT-NIR spectroscopy for assessing the spoilage caused by bacteria. The most informative wavelengths (885.27 nm, 1026.27 nm, 1039.93 nm, 1068.38 nm, 1257.55 nm, 1267.75 nm, and 1453.49 nm) related to the total bacterial count’s identification were obtained. The innovative, cost-effective, and feasible approach outlined in this article is a promising methodology for enhancing the safety and quality standards of various fishery products. Full article

To investigate the vibration properties in healthy and fault conditions of planetary gearboxes, a phenomenological model is constructed to present the vibration spectrum structure. First, the effects of the base deflection of the gear fillet and the flexibility between the root circle and the base circle on the time-varying meshing stiffness are considered in order to construct an equivalent model of time-varying mesh stiffness and broken tooth faults, exploring the law of variation for meshing stiffness when differently sized faults occur on the sun gear. Then, considering both the effect of the vibration transfer path and the meshing impacts, we establish phenomenological models of planetary gears under healthy and fault conditions. By comparing and analyzing the phenomenological model based on the cosine function to verify the effectiveness of the proposed model. The experimental results show that the error of the proposed model is 1.38% lower than that of the traditional phenomenological model, and the proposed model can accurately analyze the frequency, amplitude, and sideband characteristics of the vibration signals of sun gear with different degrees of broken tooth, which can be used for the local fault diagnosis of planetary gearboxes. Full article

Curvic couplings are used in applications demanding high positional accuracy and high torque transmission; therefore, improving their design and enhancing their load-carrying capacity is crucial. This study introduced the kinematic model Curvic3D, which was developed to produce the accurate geometry of both members of a curvic coupling using a CAD system. The model enabled the complete parametrization and customization of the coupling design using important geometric parameters. The couplings produced using Curvic3D were then imported into a finite element analysis model also developed as part of this study. A detailed analysis of the stresses developed on the teeth of the concave and convex parts provided information about the behavior of the coupling under different loading conditions. Finally, a series of geometric parameters, such as the number of teeth, the number of half pitches, the root fillet radius, and gable angle were examined as to their influence on the load-carrying capacity of the curvic coupling. The study concluded that all the examined parameters have a significant effect on the tooth flank and root area stresses. Full article

Due to machining techniques and dust deposition, gas turbine upstream slots and vane roots are always filleted, significantly affecting the cooling performance of the endwall. The effects of upstream slot fillet and vane root fillet on the cooling performance of the gas turbine endwall were investigated by solving the three-dimensional Reynolds-averaged Navier–Stokes (RANS) equations with the shear stress transport (SST) k–ω turbulence model. The results indicate that the velocity distribution of the slot coolant is effectively changed by introducing the upstream slot fillets. Among the four cases, the largest adiabatic cooling effectiveness was obtained for the case with two similar fillets, with a 42% increase in effective cooling area compared to the traditional slot. At MFR = 0.75%, the horseshoe vortex is weakened by the introduction of the vane fillet with a small radius, with a 53% increase in effective cooling area compared to the baseline. However, the vane fillet with a large radius makes the boundary layer flow separately prematurely, decreasing the cooling performance. The lateral coverage of the coolant jet from the filmhole embedded in the vane root fillet is greatly enhanced by increasing the vane root fillet radius. However, the streamwise coverage is decreased and the thermodynamic loss is increased. Full article

To solve the problem of fatigue failure in fillet welds of traction rod brackets on locomotive bogies of a given model, the cause for failure and the improvement method were studied. The results show that when there is maximum clearance at weld roots, maximum incomplete fusion of sidewalls, maximum incomplete fusion at weld roots, and maximum pores allowable in the ISO 5817 standard, the stress amplitude separately increases by 70~97%, 53~55%, 40~46%, and 19~34%. Despite this, when various types of defects of the maximum size are present in the weld alone, the static and fatigue strengths of fillet welds with a throat depth of 6 mm on the traction rod bracket can still meet the requirements in the UIC615-4 standard. In practical fillet welds, defects including clearance at weld roots, incomplete fusion, and pores are very likely to occur at the same time, which may induce fatigue failure in fillet welds of traction rod brackets within the original design life. According to the size of the frame and the traction rod brackets, a strengthening scheme for increasing the throat depth of fillet welds of traction rod brackets to 8 mm was designed. Calculation results of the strengthening scheme show that for new structures subjected to overall post-weld stress-relief thermal treatments, the maximum stress amplitude decreases by 5~29% when increasing the throat depth of fillet welds from 6 to 8 mm. For structures in service with the throat depth of fillet welds increased from 6 to 8 mm through repair welding, peak residual stress at the weld root after repair welding can reach 383 MPa. Because overall stress-relief thermal treatments cannot be performed on repair-welded structures, the fatigue strength of repair-welded fillet welds cannot meet the requirements of UIC615-4; therefore, local stress-relief treatments have to be performed in the welded zone. The results are of guiding significance for the treatment of locomotives in service and performance improvement of new locomotives and suggest that the current standard is relatively conservative. Full article

It has been demonstrated that polyphenols have the potential to extend the shelf life of fish products. Thus, the effects of phenolic extracts from grape seed (GSE), lotus seedpod (LSPC), and lotus root (LRPE) were investigated in this study, focusing on the physicochemical changes and bacterial community of refrigerated channel catfish fillets during storage at 4 °C, using ascorbic acid (AA) as reference. As a result, GSE, LSPC, LRPE and AA inhibit the reproduction of microbials in catfish fillets during storage. According to the microbial community analysis, the addition of polyphenols significantly reduced the relative abundance of Proteobacterial in the early stage and changed the distribution of the microbial community in the later stage of storage. After 11 days of storage, the increase in total volatile base nitrogen (TVB-N) in fish was significantly reduced by 25.85%, 25.70%, 22.41%, and 39.31% in the GSE, LSPC, LRPE, and AA groups, respectively, compared to the control group (CK). Moreover, the lipid oxidation of samples was suppressed, in which thiobarbituric acid-reactive substances (TBARS) decreased by 28.77% in the GSE group, compared with the CK. The centrifugal loss, LF-NMR, and MRI results proved that GSE significantly delayed the loss of water and the increase in immobilized water flowability in catfish fillets. The polyphenol-treated samples also showed less decrease in shear force and muscle fiber damage in histology, compared to the CK. Therefore, the dietary polyphenols including GSE, LSPC, and LRPE could be developed as natural antioxidants to protect the quality and to extend the shelf life of freshwater fish. Full article

Gears are one of the the most widespread mechanical components and their design is supported by standard calculation methods. Among all the possible failure modes of gears, tooth root bending is the most critical and could lead to catastrophic failures. In this regard, different surface treatments could be exploited to improve the gear strength. Among them, shot peening is the most common. The aim of this study is to evaluate the effectiveness of shot peening on improving the tooth root bending resistance. This is achieved by exploiting the Finite Element Method (FEM) in combination with advanced multiaxial fatigue criterion based on the critical plane concept. A standard Single Tooth Bending Fatigue test was reproduced numerically via FEM. Beside the wrought gears, shot peened ones were also simulated. The state of stress induced by the shot peening was obtained numerically by simulating the surface treatment itself with non-linear dynamic analyses. The results have shown quantitatively how the residual stresses promote an improvement in the resistance and how the local hardening could lead to different early paths of nucleation and propagation of cracks on the tooth fillet. Full article

The potential of Fourier transform infrared (FT-IR) spectroscopy, multispectral imaging (MSI), and electronic nose (E-nose) was explored in order to determine the microbiological quality of gilthead sea bream (Sparus aurata) fillets. Fish fillets were maintained at four temperatures (0, 4, 8, and 12 °C) under aerobic conditions and modified atmosphere packaging (MAP) (33% CO₂, 19% O₂, 48% N₂) for up to 330 and 773 h, respectively, for the determination of the population of total viable counts (TVC). In parallel, spectral data were acquired by means of FT-IR and MSI techniques, whereas the volatile profile of the samples was monitored using an E-nose. Thereafter, the collected data were correlated to microbiological counts to estimate the TVC during fish fillet storage. The obtained results demonstrated that the partial least squares regression (PLS-R) models developed on FT-IR data provided satisfactory performance in the estimation of TVC for both aerobic and MAP conditions, with coefficients of determination (R²) for calibration of 0.98 and 0.94, and root mean squared error of calibration (RMSE_C) values of 0.43 and 0.87 log CFU/g, respectively. However, the performance of the PLS-R models developed on MSI data was less accurate with R² values of 0.79 and 0.77, and RMSE_C values of 0.78 and 0.72 for aerobic and MAP storage, respectively. Finally, the least satisfactory performance was observed for the E-nose with the lowest R² (0.34 and 0.17) and the highest RMSE_C (1.77 and 1.43 log CFU/g) values for aerobic and MAP conditions, respectively. The results of this work confirm the effectiveness of FT-IR spectroscopy for the rapid evaluation of the microbiological quality of gilthead sea bream fillets. Full article

Fourier transform infrared spectroscopy (FT-IR) and multispectral imaging (MSI) were evaluated for the prediction of the microbiological quality of poultry meat via regression and classification models. Chicken thigh fillets (n = 402) were subjected to spoilage experiments at eight isothermal and two dynamic temperature profiles. Samples were analyzed microbiologically (total viable counts (TVCs) and Pseudomonas spp.), while simultaneously MSI and FT-IR spectra were acquired. The organoleptic quality of the samples was also evaluated by a sensory panel, establishing a TVC spoilage threshold at 6.99 log CFU/cm². Partial least squares regression (PLS-R) models were employed in the assessment of TVCs and Pseudomonas spp. counts on chicken’s surface. Furthermore, classification models (linear discriminant analysis (LDA), quadratic discriminant analysis (QDA), support vector machines (SVMs), and quadratic support vector machines (QSVMs)) were developed to discriminate the samples in two quality classes (fresh vs. spoiled). PLS-R models developed on MSI data predicted TVCs and Pseudomonas spp. counts satisfactorily, with root mean squared error (RMSE) values of 0.987 and 1.215 log CFU/cm², respectively. SVM model coupled to MSI data exhibited the highest performance with an overall accuracy of 94.4%, while in the case of FT-IR, improved classification was obtained with the QDA model (overall accuracy 71.4%). These results confirm the efficacy of MSI and FT-IR as rapid methods to assess the quality in poultry products. Full article

Remote laser welding (RLW) has shown a number of benefits of joining 6xxx aluminium alloys such as high processing speed and process flexibility. However, the crack susceptibility of 6xxx aluminium alloys during RLW process is still an open problem. This paper experimentally assesses the impact of transverse micro cracks on joint strength and fatigue durability in remote laser welding of extruded AA6063-T6 fillet lap joints. Distribution and morphology of transverse micro cracks were acquired by scanning electron microscope (SEM) on cross-sections. Grain morphology in the weld zone was determined by electron backscatter diffraction (EBSD) while static tensile and dynamic fatigue tests were carried out to evaluate weld mechanical performance. Results revealed that increasing welding speed from 2 m/min to 6 m/min did not introduce additional transverse micro cracks. Additionally, welding at 2 m/min resulted in tensile strength improvement by 30% compared to 6 m/min due to the expansion of fusion zone, measured by the throat thickness, and refinement of columnar grains near fusion lines. Furthermore, the weld fatigue durability is significantly higher when fracture occurs in weld root instead of fusion zone. This can be achieved by increasing weld root angle with optimum weld fatigue durability at around 55°. Full article

In this work, the potential of spectroscopic techniques was studied to investigate heat-induced changes occurring during the application of thermal treatments on cod (Gadus morhua L.) fillets. Vacuum-packed samples were thermally treated in a water bath at 50, 60, 70 and 80 °C for 5 and 10 min, and further stored for one, four, and eight days at 4 ± 1 °C before analysis. Several traditional (including cooking loss, drip loss, texture, protein solubility, protein oxidation, and color) and spectroscopic (fluorescence and diffuse reflectance hyperspectral imaging) measurements were conducted on the same samples. The results showed a decrease in fluorescence intensity with increasing cooking temperature and storage time, while the impact of cooking time was only noticeable at low temperatures. Diffuse reflectance data exhibited a decrease in absorbance, possibly as a result of protein denaturation and increased scattering at higher cooking temperatures. Both fluorescence and diffuse reflectance data were highly correlated with color parameters, whereas moderate correlations were observed with most other traditional parameters. Support vector machine models performed better than partial least square ones for both classification of cod samples cooked at different temperatures and in prediction of the cooking temperature. The best classification result was obtained on fluorescence data, achieving an accuracy of 92.5%, while the prediction models resulted in a root mean square error of prediction of cooking temperature lower than 5 °C. Overall, the classification and prediction models showed good results, indicating that spectroscopic techniques, especially fluorescence hyperspectral imaging, have a high potential for monitoring thermal treatments in cod fillets. Full article

The effects of compressor aerodynamic parameters, such as pitch-chord ratio, aspect ratio, and fillet, on the cascade performance have been studied in this paper. Slot configuration at the root of the blade has been proved to be an efficient passive control method for the corner separation control in compressor cascade. The combined effects of the pitch-chord ratio, aspect ratio, and blade fillet with a slot configuration on the blade, have also been studied. Larger corner separation caused by the high pitch-chord ratio can be eliminated by the slot, which leads to fewer blades with almost the same or even better cascade performance. Various aspect ratios, together with the slot configuration, have been investigated and all of them have a positive effect on the cascade performance. For the blade with the blade fillet, the slot still has a positive effect on the control of the corner separation, while cascade performance with just a slot configuration is better than the slot configuration under the influence of the blade fillet. Full article