An energy-based dynamic loss hysteresis model for giant magnetostrictive materials

This paper addresses the development of a magneto-elastic coupling dynamic loss hysteresis model for giant magnetostrictive materials (GMMs). Considering the eddy current loss and anomalous loss, a dynamic constitutive model is proposed to predict the dynamic hysteresis behavior of GMMs. The model is validated by comparing the predicted results with experiments. At first, the frequency effect and anisotropy effect on the domain distribution can be obtained. Moreover, the magnetostriction cannot return to the initial value near the coercive field as the magnetization does with the increasing frequency. It can be explained that the domain distribution changes with the increasing energy loss. The model is benefit for the design and control of GMMs actuators. (c) 2012 Elsevier Ltd. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000314015200006&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701MechanicsSCI(E)EI12ARTICLE5672-6795

A novel 3D geometrical reconstruction method for aluminum foams and FEM modeling of the material response

A novel method for modeling cellular materials is proposed based on MATLAB image processing and synchrotron X-ray computed tomography scanning to obtain an accurate calculation result of aluminum foam based on finite element model. The maximum entropy algorithm is employed to obtain the binarization image, and the median filtering algorithm is used to reduce the noise after binarization. The external contour and internal pores boundary is extracted by the “edge” function in MATLAB, and the geometrical model is reconstructed. A two-step mesh algorithm is adopted to mesh the reconstructed geometrical model. Accordingly, the finite element model of aluminum foam is established by the proposed method based on reconstruction geometrical model. The compression behavior of aluminum foam is obtained at 25°C, 100°C, 200°C by ABAQUS, and good agreements with experiments are achieved by applying the present reconstruction algorithm and modeling method

Analytical modeling of thermal residual stresses and optimal design of ZrO₂/(ZrO₂+Ni) sandwich ceramics

The joining of ceramics with metals have been extensively used in applications requiring high strength and excellent heat insulation. However, evaluating the residual stress generated inevitably due to the mismatch in coefficients of thermal expansion of ceramic and metal is challenging, which is very important for fabrication and characterization of layered inhomogeneous material. A simplified analytical model considering the overall deformation compatibility is established to compute the interlaminar residual stresses of the ZrO2/(ZrO2+Ni) sandwich ceramics, which agrees well with the results obtained by the commercial finite element package. The effects of the thickness ratio of the transitional layer to the middle layer, and the number of transitional layers on the properties of the ZrO2/(ZrO2+Ni) sandwich ceramics are researched to obtain the optimal structure. ? 2015 Elsevier Ltd. and Techna Group S.r.l. All rights reserved.SCI(E)[email protected]; [email protected]

Load distribution in threads of porous metal-ceramic functionally graded composite joints subjected to thermomechanical loading

Metal-ceramic functionally graded materials (FGMs) have been extensively used in aerospace engineering where high strength and excellent heat insulation materials are desired. In this paper, load distribution in threads of the Thermal Protection System used bolted joint made up of porous ZrO2/(ZrO2 + Ni) FGMs is investigated by ABAQUS codes. The bolted joint is subjected to reentry heating corresponding to the Access to Space Vehicle. Effects of bolt-nut parameters including thread tooth profile, thread pitch, and modulus ratio of bolt to nut on load distribution in threads are analyzed in detail. It is found that uneven load distribution in threads occurs at elevated temperature, which mainly focuses on the first two threads closest to the nut bearing surface, with the first thread carrying 74% of the total load. Bolt-nut parameters have great effects on load distribution in threads, with trapezoidal thread, extra fine thread and greater modulus ratio of bolt to nut leading to more evenly distributed load. Further studies show that nut shape has significant effects on load distribution in threads, the optimized nut is designed to make the maximum load bearing ratio of the thread decrease to 30.21%, and thus the service reliability of the bolted joint is greatly improved. (C) 2015 Elsevier Ltd. All rights reserved.National Natural Science Foundation of China [11090330, 11090331, 11102003, 11472038]; National Basic Research Program of China (973 Program) [2010CB832701, 2011CB610303]; Foundation of the Author of National Excellent Doctoral Dissertation of China [201029]SCI(E)[email protected]

Preparation and thermodynamic analysis of the porous ZrO₂/(ZrO₂+Ni) functionally graded bolted joint

Ceramic-metal functionally graded materials (FGMs) have been extensively used in aerospace engineering where high strength and excellent heat insulation materials are desired. In this paper, the thermodynamic behavior of the Thermal Protection System (TPS) used bolted joints made up of porous ZrO2/(ZrO2 + Ni) FGMs is investigated by finite-element (FE) modeling. The bolted joint is subjected to reentry heating corresponding to the Access to Space Vehicle. Thermodynamic simulations are carried out to yield the transient response of the porous ZrO2/(ZrO2 + Ni) functionally graded bolted joint (FGBJ). The effects of the preload on the thermomechanical behavior and service reliability of the bolted joint are numerically analyzed in detail by ABAQUS codes. It is found that the preload relaxation of the bolted joint occurs at elevated temperature, and the preload has significant influence on service reliability of the bolted joint under transient thermomechanical circumstances. With the increase of the preload, stress concentration which occurs at the root of the first thread of the bolt increases rapidly and predominates in service reliability. Proper preload is thus defined to balance the service reliability and tightness of the bolted joint. Further studies show that the shape of the nut has a great effect on the stress concentration of the thread, the optimized nut is designed to reduce the stress concentration of the thread, and thus the reliability of the bolted joint is also improved. (C) 2015 Elsevier Ltd. All rights reserved.National Natural Science Foundation of China [11090330, 11090331, 11102003, 11472038]; National Basic Research Program of China (973 Program) [2010CB832701, 2011CB610303]; Foundation of the Author of National Excellent Doctoral Dissertation of China [201029]SCI(E)[email protected]; [email protected]