Fatigue life prediction of materials can be modeled by deterministic relations, via mean or median S-N curve approximation. However, in engineering design, it is essential to consider the influence of fatigue life scatter using deterministic-stochastic methods to construct reliable S-N curves and determine safe operation regions. However, there are differences between metals and composites that must be considered when proposing reliable S-N curves, such as distinct fracture mechanisms, distinct ultimate strengths under tension and compression loading, and different cumulative fatigue damage mechanisms including low-cycle fatigue. This study aims at conducting a review of the models used to construct probabilistic S-N fields (P-S-N fields) and demonstrate the methodologies applied to fit the P-S-N fields that are best suited to estimate fatigue life of the selected materials. Results indicate that the probabilistic Stüssi and Sendeckyj models were the most suitable for composite materials, while, for metals, only the probabilistic Stüssi model presented a good fitting of the experimental data, for all fatigue regimes.7

A new, bio-inspired printed monopole antenna (PMA) model is applied to monitor partial discharge (PD) activity in high voltage insulating systems. An optimized sensor was obtained by designing a PMA in accordance with the characteristics of the electromagnetic signal produced by PD. An ultra-wideband (UWB) antenna was obtained by applying the truncated ground plane technique. The patch geometry was bio-inspired by that of the Inga Marginata leaf, resulting in a significant reduction in size. To verify the operating frequency and gain of the PMA, measurements were carried out in an anechoic chamber. The results show that the antenna operating bandwidth covers most of the frequency range of PD occurrence. Moreover, the antenna presented a good sensitivity (mean gain of 3.63 dBi). The antenna performance was evaluated through comparative results with the standard IEC 60270 method. For this purpose, simultaneous tests were carried out in a PD generator arrangement, composed by an oil cell with point-to-plane electrode configurations. The developed PMA can be classified as an optimized sensor for PD detection and suitable for substation application, since it is able to measure PD radiated signals with half the voltage levels obtained from the IEC method and is immune to corona discharges.

A novel family of composite laminates with a simplified stacking sequence and double-double layup [±ϕ/±ψ] _n has significant potential to reduce weight and increase strength, while facilitating design optimization and simplifying the manufacturing process. In this study, the low-velocity impact response of a double-double (DD) laminate and a quadriaxial (Quad) laminate of equivalent stiffness and thickness were compared. Carbon/epoxy laminates were produced with stacking sequences of [±0/±50]₁₀ and [0₃/90/±45/0₂/±45]_2S corresponding to double-double and quadriaxial varieties, respectively. Low velocity impact tests were conducted at 74 J of energy and damage areas were examined using X-ray computed tomography. Compressive strength and compression after impact (CAI) strength were equivalent for the two laminates. However, differences in impact damage morphology were observed and are discussed.

In this paper, we present the design, fabrication and calibration of a passive UHF RFID tag based soil moisture and environment temperature sensor. The inter-digital double-sided capacitive sensor developed modifies its capacitance as the soil moisture changes, due to modification of the soil permittivity. The implemented smart tag includes an external sensor front-end that is capable to process analog sensors and send digitized measurements to the reader. In order to obtain reliable readings, a process of calibration was performed and described. The used RFID chip also includes a built-in temperature sensor. The developed sensor tag presented a 6.95 ADC LSB variation per soil water content percentage and the capability to measure temperatures in a range of 0.3-59.6 °C with a 0.058°C resolution.