Search

To accurately evaluate the probabilistic characteristics of the fatigue properties of materials with small sample data under different stress ratios, a data fusion method for torsional fatigue life under different stress ratios is proposed based on the energy method. A finite element numerical modeling method is used to calculate the fatigue strain energy density during fatigue damage. Torsional fatigue tests under different stresses and stress ratios are carried out to obtain a database for research. Based on the test data, the Wt-Nf curves under a single stress ratio and different stress ratios are calculated. The reliability of the models is illustrated by the scatter band diagram. More than 85% of points are within ±2 scatter bands, indicating that the fatigue life under different stress ratios can be represented by the same Wt-Nf curve. Furthermore, P-Wt-Nf prediction models are established to consider the probability characteristics. According to the homogeneity of the Wt-Nf model under different stress ratios, we can fuse the fatigue life data under different stress ratios and different strain energy densities. This data fusion method can expand the small sample test data and reduce the dispersion of the test data between different stress ratios. Compared with the pre-fusion data, the standard deviations of the post-fusion data are reduced by a maximum of 21.5% for the smooth specimens and 38.5% for the notched specimens. And more accurate P-Wt-Nf curves can be obtained to respond to the probabilistic properties of the data.

The thermal protection system (TPS) represents one of the most critical subsystems for vehicle re-entry. However, due to uncertainties in thermal loads, material properties, and manufacturing deviations, the thermal response of the TPS exhibits significant randomness, posing considerable challenges in engineering design and reliability assessment. Given that uncertain aerodynamic heating loads manifest as a stochastic field over time, conventional surrogate models, typically accepting scalar random variables as inputs, face limitations in modeling them. Consequently, this paper introduces an effective characterization approach utilizing proper orthogonal decomposition (POD) to represent the uncertainties of aerodynamic heating. The augmented snapshots matrix is used to reduce the dimension of the random field by the decoupling method of independently spatial and temporal bases. The random variables describing material properties and geometric thickness are also employed as inputs for probabilistic analyses. An uncoupled POD Gaussian process regression (UPOD-GPR) model is then established to achieve highly accurate solutions for transient heat conduction. The model takes random heat flux fields as inputs and thermal response fields as outputs. Using a typical multi-layer TPS and thermal structure as two examples, probabilistic analyses are conducted. The mean square relative error of a typical multi-layer TPS is less than 4%. For the thermal structure, the averaged absolute error of the radiation and insulation layer is less than 25 °C and 6 °C when the maximum reaches 1200 °C and 150 °C, respectively. This approach can provide accurate and rapid predictions of thermal responses for TPS and thermal structures throughout their entire operating time when furnished with input heat flux fields and structural parameters.

The forced responses of bladed disks are highly sensitive to inevitable random mistuning. Considerable computational efforts are required for the sampling process to assess the statistical vibration properties of mistuned bladed disks. Therefore, efficient surrogate models are preferred to accelerate the process for probabilistic analysis. In this paper, four surrogate models are utilized to construct the relation between random mistuning and forced response amplitudes, which are polynomial chaos expansion (PCE), response surface method (RSM), artificial neural networks (ANN) and Kriging interpolation, respectively. A bladed disk with 2-degrees-of-freedom (2-DOF) each sector is used to validate the effectiveness of the surrogate models. The effects of number of training samples on the surrogate model accuracy are discussed. The responses results of one blade (single output) and maximum response of all blades (multi-output) indicate that PCE and Kriging interpolation could yield accurate and stable predictions of the statistical characteristics of the forced responses. PCE is recommended for the mistuned response predictions due to its accuracy and efficiency. [ABSTRACT FROM AUTHOR]

Angiographically silent cystoid macular edema (CME) is a rare complication from nab-paclitaxel. Here we report a 45-year-old woman with breast cancer who developed CME after several months of treatment with albumin-bound paclitaxel (nab-paclitaxel). Her visual acuity did not improve significantly with the cessation of nab-paclitaxel and intravitreal ranibizumab treatment. Then, brinzolamide eye drops were prescribed. One month later, her vision improved, with the macular edema significantly subsided. Finally, we reviewed other cases of CME induced by nab-paclitaxel that have been reported in the literature and discussed the underlying pathogenesis of nab-paclitaxel-induced CME.

Objective To present our experience in managing calcified lumbar disc herniation (cLDH) using a surgical decompression procedure. Methods Patients who had low back pain radiating to the leg, were preoperatively diagnosed with cLDH by computed tomography and/or magnetic resonance imaging, and were treated with a surgical decompression procedure were studied. Those without cLDH or who were treated with a method other than decompression were excluded. The treatment outcome was analyzed using the visual analog scale (VAS) score, Oswestry Disability Index, and modified Macnab criteria. Results Thirty-seven patients aged 60.5 ± 9.6 years were evaluated. The VAS scores were significantly decreased 1 day after surgery and remained low at the 3-month and 1-year follow-ups. The Oswestry Disability Index was also significantly lower at the 3-month and 1-year follow-ups. Ninety-four percent of patients rated the results as “excellent” or “good” according to the modified Macnab criteria at the 3-month follow-up. The patients developed few postoperative complications and no recurrence during 1 year of follow-up. Conclusion Our data suggest that the decompression approach is effective for management of cLDH at least in the short term (1 year) with respect to reducing pain and improving patient satisfaction with few complications.

Thermal protection system (TPS) is one of the most important subsystems for vehicle reentry. Because of the uncertainties in thermal loads, material properties, and manufacture tolerances, the thermal response of TPS has strong randomness, which brings great challenges to the engineering design and reliability evaluation. Because the uncertain aerodynamic heating loads are stochastic processes in time history, it is difficult to model them in the conventional surrogate models that usually take scalar random variables as input. This paper thus proposes an effective characterization method that can represent the uncertainties of aerodynamic heating by a set of random variables using Karhunen-Loève expansion. The random variables that describe the uncertainty of thermal loads, material properties, and geometric thickness are taken as inputs for probabilistic analyses. A kriging surrogate model is constructed to solve the transient heat conduction with high accuracy. Taking a typical multilayer TPS as an example, the probabilistic thermal analyses are carried out considering different degrees of heat rate uncertainties. The results show that the uncertainties of aerodynamic heating intensify the randomness of the thermal response of TPS, and thus have a great impact on the thermal reliability. The sensitivities of temperature response to various uncertain parameters are investigated as well, which provide a reference for system design and reliability improvement. [ABSTRACT FROM AUTHOR]

To remove the calculations of inverse and/or exponential of large-scale matrix in the precise time integration (PTI) method for transient response analysis of structures, new PTI methods equipped with the restarted Krylov subspace method and real Leja points interpolation method to calculate exp(A)b are presented in this paper. In both kinds of methods, only the multiplications of sparse matrix and vectors are involved. The theories and implementations of the improved PTI methods are introduced. The transient responses of a cantilever beam and an aeroengine bladed disk are used as numerical examples to validate the accuracy and efficiency of the proposed methods. The effects of tunable parameters of both kinds of algorithms on the numerical efficiency are also discussed. It has been demonstrated that the improved PTI methods are accurate and insensitive to integration step length and, more importantly, are highly efficient for large-scale structures subjected to high-frequency excitations, which greatly extend the applicability of PTI methods. [ABSTRACT FROM AUTHOR]