Understanding low cycle fatigue and creep–fatigue interaction behavior of 316 L(N) stainless steel weld joint

The aim of this work is to study the time dependent effects on the low cycle fatigue (LCF) behavior of 316 L(N) stainless steel weld joint. Influence of strain rate, temperature, strain range, hold time and hold duration on fatigue life is evaluated. Occurrence of dynamic strain aging, creep damage, overall distribution of damage across the weld joint and the role of microstructure on the failure mode and failure location of the weld joint is discussed as a function of test parameters.     

Do new and relocating firms have different preferences for accessibility?

Accessibility is one of the most important factors in a location choice decision of a firm. However, new and relocated establishments can value accessibility differently. Research papers differences of accessibility preferences between creations and relocations are scarce. In this paper, we examine these differences in an intraurban setting, the Lyon urban area. We rely on discrete choice models and data for more than 43,000 creations and 11,000 relocations during 2005–2011 from eight economic sectors. Results demonstrate that the effect of accessibility differs between creations and relocations of the same economic sector. This difference depends on the type of the economic activity of the sector.     

Significantly reduced hysteresis in (Fe1/2Nb1/2)4+-modified 0.75Na1/2Bi1/2TiO3-0.25SrTiO3 lead-free piezoceramics with large strain

Aiming to get the NBT-based lead-free ceramic with high strain and low strain hysteresis for practical actuator applications, a solid solution of complex-ion (Fe_1/2Nb_1/2)⁴⁺doped 0.75Na_1/2Bi_1/2TiO₃-0.25SrTiO₃ ((Na_1/2Bi_1/2)_0.75Sr_0.25Ti_1-x(Fe_1/2Nb_1/2)_xO₃, abbreviated as NBST-100xFN) was designed and prepared, and its phase structure, micromorphology, ferroelectric, strain, dielectric and piezoelectric performances were systematically investigated. It was found that the incorporation of (Fe_1/2Nb_1/2)⁴⁺ causes a structure transition from the ferroelectric/relaxor (FE/RE) mixed phases to relaxor (RE) phase, increasing to a promising strain performance at x = 0.04 featured by not only a moderate strain value of 0.26%, corresponding normalized strain d₃₃* of 371 pm/V, but also a very small strain hysteresis of 22%. In addition, the NBST-4FN ceramic sample also exhibits an unexceptionable frequency-dependence of unipolar strain. This study provides a new understanding and design idea for the practical actuator application of high strain NBT-based lead-free ceramics with ultra-low hysteresis.     

Modal-based damage identification for the nonlinear model of modern wind turbine blade

In this paper, the modal-based indices are used in damage identification of the wind turbine blade. In contrast of many of previous researches, the geometric nonlinearity due to the large structural deformation of the modern wind turbines blade is considered. In the first step, the finite element model (FEM) of the rotating blade is solved to obtain the modal features of the deformed structure under operational aerodynamic loading. Next, the accuracy and efficiency of the various modal-based damage indices including the frequency, mode shape, curvature of mode shape, modal assurance, modal strain energy (MSE) and the difference of indices (between the intact and damaged blades) are investigated. To adapt the MSE index calculation in nonlinear modeling, a new approach is introduced to include the effects of the structural nonlinearity. Furthermore, the effect of the damage length, its location and severity and also the effect of rotational speed and amplitude of loading are studied. The generic 5-MW NREL blade is used for the simulation study. The results show enough sensitivity of the mode shape curvature and MSE indices to the local damages. Moreover, the importance of geometric nonlinearity in the damage detection of the modern wind turbines is demonstrated.     

Broadband circularly polarized patch antenna with gap‐coupled feed and resistor loading

A broadband circularly polarized patch antenna with suspended structure is proposed. The suspended patch has a bow‐tie structure and a gap‐coupled feed. By connecting a resistor load to another gap‐coupled feed port at the opposite position, a wide impedance and axial ratio (AR) bandwidths are obtained. The proposed design has a very simple antenna structure with an impedance bandwidth of 44.5% and a 3‐dB AR bandwidth of 33.8%, respectively. The results show that the bandwidth of the patch antenna is successfully broadened using the suspended configuration, gap‐coupled feed, and resistor loading. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:587–593, 2014.     

Modelling of heat flow and interdendritic crack formation in twin-roll strip casting of aluminium alloys

Preliminary mathematical analyses of different interdendritic cracks associated with variation of heat transfer and generation of interdendritic strain in horizontal twin-roll strip casting have been investigated. A 1-D transient finite difference model of heat flow, dendritic solidification and interdendritic thermo-metallurgical strain has been developed. The model contains two cracking criteria to predict qualitatively and quantitatively the tendency of interdendritic crack formation during dendritic solidification of pure aluminium and 6022 aluminium alloy. The model predictions are compared to available analytical methods and previous measurements. This is to verify and calibrate the model where good and reasonable agreements are obtained, respectively. The variations of heat transfer modes during different contact cooling zones and their effects on the generation of interdendritic thermo-metallurgical strain at the surface and central strip locations have been analysed. The model predictions point out that the different contact cooling zones of strip surface and surroundings control the stages of interdendritic crack formation in different mushy regions. The mechanism of interdendritic crack formation in twin-roll strip casting process with previous and present cracking criteria have been explained and discussed. These discussions show the importance of selection of mathematical treatment to predict the stages of interdendritic crack formation.     

Tensile flow behavior of ultra low carbon,low carbon and micro alloyed steel sheets for auto application under low to intermediate strain rate

This paper is concerned with tensile characteristics of auto grade low carbon, ultra low carbon and micro alloyed steel sheets under low to intermediate strain rates ranging from 0.0007 to 250 s⁻¹. Experimental investigation reveals two important aspects of these steels under intermediate strain rate deformation. Firstly, the yield stress increases with strain rate in all these steels. Of course yield stress increment is higher for low carbon and ultra low carbon steel sheets. Secondly, the strain hardening rate drastically decreases with strain rate for low carbon and ultra low carbon steel sheets, whereas it remains steady for micro alloyed steel sheets. Based on these observations, a constitutive model has been proposed which predicts the strain rate sensitive flow behavior of all these grades within the strain rate range of automotive crash event.     

Synthesis and characterization of CuO–SnO2 nanocomposite and its application as liquefied petroleum gas sensor

Present paper reports the synthesis of CuO–SnO₂ nanocomposite via sol–gel route as a sensing material for a liquefied petroleum gas (LPG). X-ray diffraction analysis confirmed the formation of CuO–SnO₂ nanocomposite. Crystallite size was found 5 nm. The optical band gap of the nanocomposite was found 4.1 eV. The thin/thick films were fabricated using spin coating and screen printing technology respectively and investigated with the exposition of LPG at room temperature (25 °C). Surface morphology of the thin film exhibits that it has a number of gas adsorption sites. The sensitivities of the thick and thin film sensors were found 4.1 and 42 respectively. The response and recovery times of the fabricated film sensor were 180 and 200 s respectively. Maximum sensor response of thin film sensor was found 4100. Better sensitivity and percentage sensor response, small response and recovery times, and good reproducibility and stability recognize the fabricated thin film of CuO–SnO₂ as a challenging material for the detection of LPG.