Fatigue analysis of railway wheel using a multiaxial strain‐based critical‐plane index

A fatigue damage model to assess the development of subsurface fatigue cracks in railway wheels is presented in this paper. A 3‐dimensional finite element model (FEM) is constructed to simulate repeated cycles of contact loading between a railway wheel and a rail. The computational approach includes a hard‐contact over‐closure relationship and an elastoplastic material model with isotropic and kinematic hardening. Results from the simulation are used in a multiaxial critical‐plane fatigue damage analysis. The employed strain‐based critical‐plane fatigue damage approach is based on Fatemi‐Socie fatigue index that takes into account the non‐proportional and out‐of‐phase nature of the multiaxial state of stress occurs when a railway wheel rolls on a rail. It predicts fatigue‐induced micro‐crack nucleation at a depth of about 3.7 mm beneath the wheel tread, as well as the crack plane growth orientation which indicates the possible failure pattern. Additionally, the influence of various factors such as contribution of normal stresses, higher wheel load, and material model have been investigated.     

Application of the adjoint multi-point and the robust optimization of shock control bump for transonic aerofoils and wings

A shock control bump (SCB) is a flow control method which uses a local small deformation in a flexible wing surface to considerably reduce the strength of shock waves and the resulting wave drag in transonic flows. Most of the reported research is devoted to optimization in a single flow condition. Here, both equally and variably weighted multi-point optimization and a robust adjoint optimization scheme are used to optimize the SCB. The numerical simulation of the turbulent viscous flow and a gradient-based adjoint algorithm are used to find the optimum location and shape of the SCB for two benchmark aerofoils. A multi-point optimization method under a constant-lift-coefficient constraint is implemented to find the optimum design of a two-dimensional (2D) SCB and it is observed that the general results are similar to other optimization algorithms. To show that these results are extendable to real three-dimensional (3D) cases, a 3D bump model with 11 parameters is introduced, and it is optimized using both single- and multi-point optimization procedures. Although the 3D flow structure involves much more complexity, the overall results are shown to be similar to the 2D case.     

Immunogenicity of MultiTEP-Platform-Based Recombinant Protein Vaccine,PV-1950R,Targeting Three B-Cell Antigenic Determinants of Pathological α-Synuclein

Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) are characterized by the aberrant accumulation of intracytoplasmic misfolded and aggregated α-synuclein (α-Syn), resulting in neurodegeneration associated with inflammation. The propagation of α-Syn aggregates from cell to cell is implicated in the spreading of pathological α-Syn in the brain and disease progression. We and others demonstrated that antibodies generated after active and passive vaccinations could inhibit the propagation of pathological α-Syn in the extracellular space and prevent/inhibit disease/s in the relevant animal models. We recently tested the immunogenicity and efficacy of four DNA vaccines on the basis of the universal MultiTEP platform technology in the DLB/PD mouse model. The antibodies generated by these vaccines efficiently reduced/inhibited the accumulation of pathological α-Syn in the different brain regions and improved the motor deficit of immunized female mice. The most immunogenic and preclinically effective vaccine, PV-1950D, targeting three B-cell epitopes of pathological α-Syn simultaneously, has been selected for future IND-enabling studies. However, to ensure therapeutically potent concentrations of α-Syn antibodies in the periphery of the vaccinated elderly, we developed a recombinant protein-based MultiTEP vaccine, PV-1950R/A, and tested its immunogenicity in young and aged D-line mice. Antibody responses induced by immunizations with the PV-1950R/A vaccine and its homologous DNA counterpart, PV-1950D, in a mouse model of PD/DLB have been compared.     

A fast-locking low-jitter digitally-enhanced DLL dynamically controlled for loop-gain and stability

Conventional structure of delay locked loops (DLLs) is modified to achieve better jitter and smaller lock time. In the proposed structure, analog charge pump is eliminated, to remove the problems of leakage current on output capacitance, and is replaced by combination of a digital accumulator (ACC) and a digital-to-analog converter. A programmable ACC is also proposed, to dynamically control the loop gain and lock time. When the loop enters to lock region at the first time, a lock detector block disables ACC and equivalent digital code is stored on a latch array. So, a fixed control voltage controls delay elements and the systematic jitter, due to periodic discharge of control voltage. RMS jitter of less than 33.5 and 1.6 ps are achieved at 20 and 625 MHz operating frequencies, respectively, when the supply is subject to 110 mV random noise and also 40 mV periodic noise, related to generated clock signals. Lock time is reduced from 38 to 2 µs at 20 MHz, and also from 900 to 45 ns at 600 MHz, when the proposed dynamic control mechanism is applied on the loop. Total power consumption for the main core of DLL is 7.85 mW at 1.8 V supply in 0.18 µm CMOS process.     

Synthesis and characterization of PVAm/SBA-15 as a novel organic–inorganic hybrid basic catalyst

Composite polyvinyl amine/SBA-15 (PVAm/SBA-15) in various amounts of SBA-15 were prepared and characterized. The physical and chemical properties of PVAm/SBA-15 were investigated using FT-IR, XRD, BET, SEM and TGA techniques. The catalytic performance of each material was determined for the Knoevenagel condensation reaction between carbonyl compounds and ethyl cyanoacetate in the presence of ethanol as solvent. The effects of reaction temperature, solvent and the amounts of catalyst as well as recyclability of the catalyst were investigated. The catalyst used for this synthetically useful transformation showed a considerable degree of reusability besides being very active.     

Divergence and flutter instabilities of nanobeams in moving state accounting for surface and shear effects

Transverse vibrations of elastically rested moving beam-like nanostructures accounting for surface effect are of high concern. The role of nonlocality on the free dynamic response of moving nanobeams has been revealed in recent years; nevertheless, the influence of the surface energy on the mechanical behavior of such elements has not been explained yet. In this paper, equations of motion of rested nanoscaled beams in the moving state are derived carefully via surface energetic-shear deformable beam models. Subsequently, the transverse vibrations of the nanostructure are evaluated using Galerkin-based assumed mode method. The explicit expressions of divergence velocities are obtained analytically, and these are successfully verified with the results of a numerical approach. The roles of crucial parameters on the first divergence velocity are addressed in some detail. Additionally, the stable and unstable regions are determined systematically and the influence of both surface energy and shear energy on the stability of moving nanostructure is discussed.     

A multiple observers and dynamic weighting ensembles scheme for diagnosing new class faults in wind turbines

This paper presents an incremental way to design the decision module of a diagnostic system by resorting to dynamic weighting ensembles of classifiers. The method is applied for sensor fault detection and isolation in a doubly fed induction generator for wind turbine application. Three sets of observers are combined to generate residuals that are robust to operating point changes. These signals are progressively fed into a dynamic weighting ensembles algorithm, called Learn⁺⁺.NC, for fault classification. The algorithm incrementally learns the residuals–faults relationships and dynamically classifies the faults including multiple new classes. It resorts to a dynamically weighted consult and vote mechanism to combine the outputs of the base-classifiers.     

The effects of the micrometric and nanometric iron (Fe) additives on the mechanical and thermal dehydrogenation of lithium alanate (LiAlH4), its self-discharge at low temperatures and rehydrogenation

LiAlH₄ containing 5 wt.% of nanometric Fe (n-Fe) shows a profound mechanical dehydrogenation by continuously desorbing hydrogen (H₂) during high energy ball milling reaching ∼3.5 wt.% H₂ after 5 h of milling. In contrast, no H₂ desorption is observed during low energy milling of LiAlH₄ containing n-Fe. Similarly, no H₂ desorption occurs during high energy ball milling for LiAlH₄ containing micrometric Fe (μ-Fe) and, for comparison, both the micrometric and nanometric Ni (μ-Ni and n-Ni) additive. X-ray diffraction studies show that ball milling results in a varying degree of the lattice expansion of LiAlH₄ for both the Fe and Ni additives. A volumetric lattice expansion larger than 1% results in the profound destabilization of LiAlH₄ accompanied by continuous H₂ desorption during milling according to reaction: LiAlH₄ (solid) → 1/3Li₃AlH₆ + 2/3Al + H₂. It is hypothesized that the Fe ions are able to dissolve in the lattice of LiAlH₄ by the action of mechanical energy, replacing the Al ions and forming a substitutional solid solution. The quantity of dissolved metal ions depends primarily on the total energy of milling per unit mass of powder generated within a prescribed milling time, the type of additive ion e.g. Fe vs. Ni and on the particle size (micrometric vs. nanometric) of metal additive. For thermal dehydrogenation the average apparent activation energy of Stage I (LiAlH₄ (solid) → 1/3Li₃AlH₆ + 2/3Al + H₂) is reduced from the range 76 to 96 kJ/mol for the μ-Fe additive to about 60 kJ/mol for the n-Fe additive. For Stage II dehydrogenation (1/3Li₃AlH₆ → LiH+1/3Al + 0.5H₂) the average apparent activation energy is within the range 77–93 kJ/mol, regardless of the particle size of the Fe additive (μ-Fe vs. n-Fe). The n-Fe and n-Ni additives, the latter used for comparison, provide nearly identical enhancement of dehydrogenation rate during isothermal dehydrogenation at 100 °C. Ball milled (LiAlH₄ + 5 wt.% n-Fe) slowly self-discharges up to ∼5 wt.% H₂ during storage at room temperature (RT), 40 and 80 °C. Fully dehydrogenated (LiAlH₄ + 5 wt.% n-Fe) has been partially rehydrogenated up to 0.5 wt.% H₂ under 100 bar/160°C/24 h. However, the rehydrogenation parameters are not optimized yet.