Papers by Keyword: Thermomechanical

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Authors: Guo Ming Zhu, Yong Lin Kang, Wei Chen, Guang Ting Ma
Abstract: In the H-beam rolling process, the deformations and temperature field of workpiece significantly influence the mechanical properties due to the change of product microstructure. Prediction of them is important for the groove design and passes sequences. To get the deformation behavior and the temperature field of workpiece, commercial FEM program LS-DYNA has been used to analyze the whole process of H-beam rolling. The approach is based on 3D thermal mechanical coupled finite element method. The rolling process is divided into several units for calculation. The mesh of workpiece is rebuilt in the simulation for reducing the influence of element distortion. The result shows that, the temperature at the wed to flange position maintains the highest during the whole rolling process, while area of the web the lowest. After the rolling, temperature difference is above 150K between the web’s surface and flange’s inside surface, approximate 130K on the flange’s outside surface and 200K in the cross section. The simulation results show good agreement with the measured temperature data.
Authors: A. Margossian, Sylvain Bel, Luciano Avila Gray, R. Hinterhölzl
Abstract: The ability of a draping simulation to accurately predict the outcome of a forming process mainly depends on the accuracy of the input parameters. For pre-impregnated composites, material must be characterised in the same conditions as forming occurs, i.e. in temperature regulated environment. Given the issues encountered while testing specimens enclosed in a thermal chamber and mounted on a tensile testing machine, new test methods have to be developed. A new approach using a Dynamic Mechanical Analysis system is presented for the investigation of tensile properties perpendicular to fibre direction of unidirectional pre-impregnated composites. Analyses are focused on a unidirectional carbon fibre thermoplastic tape reinforced polyamide 6 in its molten state. Quasi-static tests are performed at forming temperature for different loading rates with specimens of different geometries in order to assess the reproducibility of the test method.
Authors: Robert A. Shanks, Ahmad Asadinezhad
Abstract: Mechanical testing is foremost a means to measure material performance, however it provides a probe into the complex elastic, viscoelastic and viscoplastic behavior of polymer morphologies. The techniques in this work utilize variables of time/frequency, temperature, stress and strain with emphasis on dynamic and modulated implementation. Several instruments were used since a particular instrument does not provide all of the capabilities. The material response is complex and it has been resolved into typically instantaneous and time-dependent components. Some of the techniques are widely used and these have been extended, while other techniques introduce control over alternate variables. Polycarbonate was chosen as the main example with support from similar polymers, though the techniques are applied to many polymer types.
Authors: S. Msolli, Olivier Dalverny, Joël Alexis, Moussa Karama
Abstract: Solder materials are critical packaging compounds and due to usually weakest melting temperature among packaging constitutive materials, thus, they are frequently subjected to a multitude of physical phenomena: creep, fatigue and combined hardening effects. The complexity and interaction of such factors must be considered in suitable way in the mechanical behavior modeling using the appropriate material behavior laws. The choice of the mechanical model depends on several factors such as the complexity of constitutive equations to be integrated, the availability and suitability of implementation in the FE codes, the number of parameters to be identified, the capability of the model to represent the most common physical features of the material… Following these observations and in order to deal with these critical remarks, comparisons between the most common unified viscoplastic models should be done in the local and finite element levels for the decision upon the most efficient model. That is the aim of this paper with application to a tin based solder token as the test material.
Authors: Cláwsio Rogério Cruz de Sousa, Wilson Acchar, Herval Ramos Paes, José Flávio Timoteo
Abstract: Doped lanthanum chromite has been the most common material used as interconnectors in solid oxide (SOFC) fuel cell, allowing for the stacking of the SOFC. Reducing the operating temperature, to around 800°C, the cells of solid oxide fuel have made the use of metal interconnectors possible as an alternative to ceramic LaCrO3. From the practical point of view for the material to be a strong candidate as an interconnector, it must have good physical and mechanical properties, such as resistance to oxidizing environments and reducers, facility to manufacture, and adequate thermomechanical properties. In this work, a study was conducted on the thermomechanical properties of metallic interconnectors (AISI 444) covered with La0,8Ca0,2CrO3 by way of deposition technique for pyrolysis spray for the intermediate temperature (IT-SOFC) fuel cell. The material was characterized by X-ray diffraction (XRD), oxidative test, flexural strength at room temperature and at 900°C, and scanning electron microscopy (SEM). The evaluation of the phases formed on metallic interconnectors coated with La0,8Ca0,2CrO3 on both the deposition and after oxidative assay was performed by XRD. The oxidative behavior showed increased resistance to oxidation of the metal substrate covered by La0,8Ca0,2CrO3. In the flexural strength of the coated metal substrate, it was noted only in the increasing temperature. With the aid of SEM, the formation of layers of Cr2O3 and (Cr, Mn)3O4 on the metallic substrate was seen, and confirmed stability of La0,8Ca0,2CrO3 ceramic film after oxidative test.
Authors: A. Baazaoui, T. Fourcade, Olivier Dalverny, Joël Alexis, Moussa Karama
Abstract: This paper deals with an identification methodology of the interfacial fracture parameters to predict the lifetime of a metallic brazed joint. The methodology is based on an experimental-numerical study whereby the optimal parameters are obtained. The experimental data, using the scanning electron microscope analysis, allowed approving that failure of the assembly based AuGe solder seems first to appear near the interfaces. These results were confirmed by micrographs analysis of the solder/insert and solder/substrate interfaces. Then, using shear test results and parametric identification coupled with a finite elements model (FEM) simulation, the damage constitutive law of the interfacial fracture based on a bilinear cohesive zone model are identified. The agreement between the numerical results and the experimental data shows the applicability of the cohesive zone model to fatigue crack growth analysis and life estimation of brazed joints.
Authors: Lei Zheng, Shan Gao
Abstract: The X70 grade and X80 grade pipeline steel strip with acicular ferrite microstructure have been researched and developed. The properties of the steel with acicular ferrite were studied by using tensile test, Charpy impact test, CTOD test and DWTT test, and compared to that of the steel with ferrite and pearlite. The microstructure of acicular ferrite was analyzed by using optical metallographic microscopy, scanning electron microscopy and transmission electron microscopy. It shows that the acicular ferrite pipeline steel has high strength, high toughness, low ductile-brittle transition temperature and high fracture-arrest toughness, the excellent properties are benefit from the uniform microstructure, clean steel, and the low carbon acicular ferrite in which consist of interaction of very fine precipitated particles and high-density dislocation.
Authors: Zheng Hu, Ming Han, Zhen Chuan Song, Ke Yan Ning
Abstract: In order to research the thermomechanical behavior of multidisc friction pairs system, three dimensional model is established for numerical simulation under simulated braking process. Based on some accurate boundary conditions, the temperature fields and thermal stress fields of friction discs and separator discs are simulated using finite element method. The temperature fields and contact stress fields of friction disc and separator discs are obtained, and their regularities of distribution are studied spatially and historically. To verify the simulation results, an experimental investigation is carried out. The results offered references for analyzing failure forms and causes of the wet multidisc friction pairs system.
Authors: Wan Masrurah Bt Hairudin, Mokhtar B. Awang
Abstract: In this paper, thermo mechanical modelling of cutting process has been developed using a commercially available finite element analysis software, ABAQUS. A 2-D orthogonal cutting has been modelled using Arbitrary Lagrangian-Eulerian (ALE) formulation. The Johnson-Cook plasticity model has been assumed to describe the material behaviour during the process. This study is aimed at temperature and stresses distributions during machining of AISI 1045 steel with different rake angles; α=0° and α= -10°. The results showed that the maximum stress for 0° and -10° are 963MPa and 967MPa while the maximum temperature results shown that 771°C and 347°C.
Authors: Z. Ayadi, S. Etienne, M. Nivoit, J.M. Fiorani, Ch. Cunat
Abstract: Thermal and thermomechanical stability of a crosslinked diacryl photopolymer is examined by means of various experimental techniques. Aging is observed and it is explained by the polymerization which is not completely achieved or/and by liquid glass transition manifestations related to the thermomechanical history of the material.
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