Critical failure was observed in the shear web of a wind turbine blade during a full‐scale testing. This failure occurred immediately before the ultimate failure and was partly caused by buckling and non‐linear cross‐sectional strain. Experimental values had been used to compare and validate both numerical and semi‐analytical results in the analysis of the shear webs in the reinforced wind turbine blade. Only elastic material behaviour was analysed, and attention was primarily focused on the Brazier effect. The complex, geometrically non‐linear and elastic stress–strain behaviour of the shear webs and the cap in compression were analysed using a balance of experimental, numerical and analytical approaches. It was noted that the non‐linear distortion was caused by the crushing pressure derived from the Brazier effect. This Brazier pressure may have a significant impact on the design of new blades, and an optimized box girder had been studied to show the importance of including Brazier pressure in the design process for future wind turbine blades. Copyright © 2011 John Wiley & Sons, Ltd.

Geraniaceae seeds represent a role model in soft robotics thanks to their ability to move autonomously across and into the soil driven by humidity changes. The secret behind their mobility and adaptivity is embodied in the hierarchical structures and anatomical features of the biological hygroscopic tissues, geometrically designed to be selectively responsive to environmental humidity. Following a bioinspired approach, the internal structure and biomechanics of Pelargonium appendiculatum (L.f.) Willd seeds are investigated to develop a model for the design of a soft robot. The authors exploit the re‐shaping ability of 4D printed materials to fabricate a seed‐like soft robot, according to the natural specifications and model, and using biodegradable and hygroscopic polymers. The robot mimics the movement and performances of the natural seed, reaching a torque value of ≈30 µN m, an extensional force of ≈2.5 mN and it is capable to lift ≈100 times its own weight. Driven by environmental humidity changes, the artificial seed is able to explore a sample soil, adapting its morphology to interact with soil roughness and cracks.

Energy consumption, environmental impact, and sustainability have risen fast through the ranks, achieving the first places in driving investments, policies, and concerns of all countries at any developmental stage. Energy transformation, though, must cope with nonunitary efficiency of devices and processes, which results in a distributed production of waste heat. A reduction of emissions, implying a conversion of waste heat to more noble forms of energy and a concurrent increase in efficiency of the same devices and processes, is of paramount importance. In view of the enthalpy content and distribution of the different sources of waste heat, low‐grade/low‐enthalpy sources below 200 °C are considered the most fertile field for research and development, with an impressive industrial growth rate. Thermodynamic cycles and thermal conversion devices based on the most relevant physical effects are herein introduced and briefly described, including both solutions that already achieved industrial maturity and less developed systems and devices whose study is still in progress. A specific focus on three application domains, selected due to their economic relevance, is done: industrial processes for the vast energy and capital availability, automotive sector for its permeation, and wearable devices for the market size. Limits and opportunities are critically discussed.

Abstract

Although it has long been recognized that all long thin-walled hollow structures exhibit a nonlinear response to bending moments, the majority of analytical research has focused on circular cross sections. A method of predicting the nonlinear behavior of multibay airfoil sections is presented. Although the approach is simple, the algebraic complexity lends itself toward a solution using algebraic manipulation software. Comparison of the analytical models with finite element analysis shows good correlation and demonstrates the ability of the model in predicting the nonlinear bending response of smooth orthotropic two-bay airfoils. Nomenclature[a] = shell in-plane compliance matrix C = overall curvature [D] = shell bending stiffness matrix E = Young's modulus G = shear modulus h = height I = second moment of area l = section Y dimension M = longitudinal bending moment m = cross-sectional bending moment p = cross-sectional reaction force S = wall length U = energy w = cross-section displacement z α = cos(β) β = horizontal wall angles to midplane ε = strain κ = cross-sectional curvature λ = element length correction factor µ = I correction factor ν = Poisson's ratio ψ = distributed Brazier crushing force

Nowadays, energy-related issues are of paramount importance. Every energy transformation process results in the production of waste heat that can be harvested and reused, representing an ecological and economic opportunity. Waste heat to power (WHP) is the process of converting the waste heat into electricity. A novel approach is proposed based on the employment of liquid nano colloids. In this work, the triboelectric characterization of TiO2 nanoparticles dispersed in pure water and flowing in a fluorinated ethylene propylene (FEP) pipe was conducted. The idea is to exploit the waste heat to generate the motion of colloidal TiO2 through a FEP pipe. By placing an Al ring electrode in contact with the pipe, it was possible to accumulate electrostatic charges due to the triboelectric effect between the fluid and the inner pipe walls. A peristaltic pump was used to drive and control the flow in order to evaluate the performances in a broad fluid dynamic spectrum. The system generated as output relatively high voltages and low currents, resulting in extracted power ranging between 0.4 and 0.6 nW. By comparing the power of pressure loss due to friction with the extracted power, the electro-kinetic efficiency was estimated to be 20%.

The modeling of electromagnetically-operated fluids represents a technologically relevant domain, yet a scientifically challenging study. In particular, real fluids typically fall between existing consolidated models, such as hydrodynamics, electrohydrodynamics, magnetohydrodynamics and ferrohydrodynamics. A key element for the description of dynamic phenomena is the so called magnetic body force, whose role is that of shaping electromagnetic forces under simplified schemes and capturing the broadest phenomena possible. In this study a simple model equation is proposed and justified in light of existing literature, and the benefits of decoupling the effects of temperature and external magnetic field are discussed making reference to the advantages gained in numerical simulations.

No abstract