Safran Electronics (Canada)

This study deals with the development of a predictive tool to estimate the fatigue life of adhesively bonded assemblies submitted to mixed-mode loading. This numerical approach is based on an energy-based criterion. The use of this fatigue criterion requires the adhesive behaviour model to calculate the dissipated energy per cycle. An epoxy-based adhesive was investigated using modified Scarf specimens, under mixed-mode loading, and a generalised viscoelastic Maxwell-type model was first identified by performing multi-level creep tests. In addition, a finite element model of Scarf specimens was developed to identify the parameters of the behaviour law and of the energy-based criterion. Then, finite element calculations were post-processed to produce S-N curves under mixed-load loading. Parallelly, fatigue tests were performed for three load ratios (−1, −0.2 and 0.2) and three loading frequencies (1, 5 and 10 Hz) to build a strong database. It was found that the fatigue lifetime was especially influenced by the load ratio R, but no significant frequency effect was observed within the studied range, excepted for R = 0.2. The fatigue criterion accurately reproduces the effects observed experimentally and the numerical fatigue lifetimes, given by the model, were in good agreement with the experimental results.

This paper highlights the effectiveness of noise-reduction devices on an 8%-scale, detailed four-wheel main landing gear model based on NASA’s design for the high-lift common research model (CRM-HL). This project is a collaborative effort between JAXA and Safran Landing Systems to reduce landing gear noise from commercial airplanes. The study investigates three types of noise-reduction devices that utilize porous plates: a truck beam porous plate with forward-bent edges, main strut porous plates, and brace porous plates. Although the main landing gear is a generic research model, the noise-reduction devices were designed to be structurally practical while considering the landing gear’s retractability and clearance margins. Far-field noise measurements were conducted at a freestream wind speed of 80 m/s on the stand-alone main landing gear model, both with and without noise-reduction devices. Additionally, computational simulations were performed to validate results against experimental data and to enhance understanding of the noise-reduction effects by visualizing flowfields. The noise-reduction configuration using the three devices significantly reduced noise by over 2 dB at all four microphone locations in a wind-tunnel test.

In this study, test samples were prepared from CLT, wooden materials and wooden laminated materials, and bending strength and elasticity modulus values were determined. All samples were prepared using Scots pine (Pinus sylvestris L.) timber as the wood species and PVAc glue as the adhesive. Four-point bending test was applied to the test samples in two different directions, vertical and parallel to the glue line. Flexural and elastic modulus values were examined. The highest bending strength and elasticity modulus values were found in wood laminated material and the lowest in solid wood material. The average values of bending strength and modulus of elasticity were found to be higher in the direction parallel to the glue line than in the direction vertical to the glue line. As a result of the study, it can be said that CLT and wooden laminated materials can be used as an alternative to solid materials, which are frequently used as building and frame construction furniture materials.

High-temperature proton exchange membrane fuel cells (HT-PEMFCs) are interesting alternatives to fossil fuel-based technologies for power generation. Their higher operating temperature compared to classic low temperature (LT) PEMFCs is highly beneficial regarding the total system complexity and weight, especially for applications which cannot involve bulky/heavy cooling systems, like aeronautics. However, at the current state-of-art of the technology, the membrane electrode assembly performance in HT-PEMFC does not reach that of LT-PEMFCs and needs to be improved; this requires better catalyst material, catalyst layer structure and membrane doping [1], [2]. A given catalyst performance is largely influenced by phosphoric acid electrolyte poisoning [3], [4] and some studies have already evaluated such poisoning level on various catalysts toward oxygen reduction reaction [5], [6]. The current study further addresses this issue and specifically aims to understand the impact of various parameters which should impact the catalyst activity in H3PO4 electrolytes (loading, nano-particle size and shape, chemistry of the catalyst particles (Pt vs PtNi), density of aggregates, nature of the carbon support) and to evaluate the poisoning effect whether at low potential (anode) or at high potential (cathode).The effect of different parameters was unveiled thanks to a catalyst library (Figure a), analyzed comparatively in 1 M HClO4 and 1 M H3PO4 electrolytes at room temperature with a classic rotating disk electrode set-up and a gas diffusion electrode set-up. Pseudo CO-Stripping voltammetry, Hupd and CO-stripping voltammetry enable to shed light on the poisoning of the Pt surfaces: the electrochemical surface area (ECSA) is divided by a factor around 2 in H3PO4 electrolyte compared to HClO4 and varies according to the catalyst properties. The impact on hydrogen oxidation reaction is then noticeable. The poisoning at high potential (> 0.6 VvsRHE) was mainly evaluated thanks to the ORR activity (Figure b): the Pt nanoparticle size/shape, their loading on the carbon support and alloying with Ni do impact their ORR activity. All the catalysts exhibit significantly lower activity in H3PO4 than in HClO4 (by a factor ca 10). The mechanisms of H3PO4-induced poisoning and potential strategies to mitigate it will be detailed.[1] S. S. Araya et al., “A comprehensive review of PBI-based high temperature PEM fuel cells,” Int J Hydrogen Energy, vol. 41, no. 46, pp. 21310–21344, Dec. 2016, doi: 10.1016/j.ijhydene.2016.09.024.[2] R. E. Rosli et al., “A review of high-temperature proton exchange membrane fuel cell (HT-PEMFC) system,” Int J Hydrogen Energy, vol. 42, no. 14, pp. 9293–9314, Apr. 2017, doi: 10.1016/j.ijhydene.2016.06.211.[3] B. F. Gomes et al., “Effect of phosphoric acid purity on the electrochemically active surface area of Pt-based electrodes,” Journal of Electroanalytical Chemistry, vol. 918, Aug. 2022, doi: 10.1016/j.jelechem.2022.116450.[4] N. Sugishima et al., “Phosphorous Acid Impurities in Phosphoric Acid Fuel Cell Electrolytes: I . Voltammetric Study of Impurity Formation,” J Electrochem Soc, vol. 141, no. 12, pp. 3325–3331, Dec. 1994, doi: 10.1149/1.2059334.[5] Q. He et al, “Influence of phosphate anion adsorption on the kinetics of oxygen electroreduction on low index Pt(hkl) single crystals,” Physical Chemistry Chemical Physics, vol. 12, no. 39, pp. 12544–12555, Oct. 2010, doi: 10.1039/c0cp00433b.[6] K. ‐L. Hsueh et al, “Effects of Phosphoric Acid Concentration on Oxygen Reduction Kinetics at Platinum,” J Electrochem Soc, vol. 131, no. 4, pp. 823–828, Apr. 1984, doi: 10.1149/1.2115707. Figure 1

This paper presents the design of a 6-bit active phase shifter in 0.13µm SiGe technology, designed for Ka-band beamforming front ends (28-30 GHz). The circuit consists of three main stages: an active balun, a second-order RC polyphase filter (I/Q generator), and four digitally controlled Variable Gain Amplifiers (VGAs). Measurement results show a root mean square (RMS) phase error of less than 1.3° at 29 GHz and less than 3° between 28-30 GHz. The average insertion loss is better than-7.2 dB around 29 GHz. The RMS gain error is below 1.02 dB at 29 GHz and as low as 1.14 dB across the 28-30 GHz range. The power consumption is under 74 mW, and the layout covers a core area of 0.67 mm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>.

ABSTRACT This paper analyses the transition temperature and duration of the cooling regimes (film boiling, transition boiling, nucleate boiling, and convection) during quenching by immersion of specimens covering a range of Biot numbers from 0.70 to 1.32. Test data were acquired under an industrial environment, thus capturing the in situ conditions, information that is rarely available in the literature. The experimentally acquired cooling curves were processed to determine characteristic points, in the form of time, temperature, and cooling rate, representing the transition between cooling regimes. These points were precisely identified as per the peaks of the cooling curve derivatives with respect to time. The results show that transition temperatures tend to decrease with the number following a linear behavior. Correlation models between the duration of each regime and the number were developed following the nonlinear behavior of the regimes. The duration of boiling phases and convection evolve inversely; the former prevails as the number decreases, while the latter drives the cooling time for larger numbers. The models provide reference points for time and temperature that constitute the basis for a more comprehensive thermal modeling of immersion quenching.

Abstract Aircraft engine manufacturers develop new combustion technologies to comply with stricter regulations on pollutant emissions, such as nitrous oxides or soot. Staged systems coupled with lean premixed combustion show promising prospects to reduce these emissions through correct mixing of the fuel ahead of the combustion chamber, but are more prone to thermo-acoustic instabilities. Hence, guaranteeing the stability over the entire operating range is more challenging. The thermo-acoustic behavior of lean staged systems is investigated experimentally on the laboratory-scale BIMER combustor, an atmospheric pressure test rig composed of a two-stage swirled injector reminiscent of industrial systems and fueled with liquid dodecane. It uses a simplex atomizer in the pilot stage, multipoint injection in the main stage, and can be externally forced using a siren device located upstream of the injector. This study focuses on the thermo-acoustic behavior of the pilot stage of the BIMER combustor. Flame response to acoustic perturbations at different preheating temperatures (ranging from 383 to 473 K) is assessed. To this end, flame describing functions (FDF) are measured using acoustic forcing, a photomultiplier with an OH* filter for heat release rate fluctuation measurements and the multimicrophone method to determine acoustic velocity fluctuations. An acoustic network model of the combustor using the L-ζ model for the injector is used to compute acoustic velocity fluctuations at the base of the flame. This model is parameterized using only the burner geometrical configuration, with no tuning to fit reference experimental data. The accuracy of the model prediction is discussed. Measurements also display flame shape bifurcations from V to Tulip-shape flames generated by acoustic forcing at certain frequencies and amplitudes. High-speed imaging of flame chemiluminescence in the visible range is used to describe these bifurcations. The role of acoustic forcing is highlighted through phase-averaging.