共查询到20条相似文献,搜索用时 15 毫秒
1.
Attempts have been made to alter the solidification microstructures of fiber reinforced aluminum composites by cooling the
ends of the fibers extending out of the mold. Experimental observations indicate that cooling the extended ends of the reinforcement
results in finer microstructures in the matrix and changes the nature of the interface. In this paper, numerical simulation
is performed on a two-dimensional axi-symmetric model to investigate the solidification process of metal matrix composite
(MMC) with the extended ends of the fibers cooled by a heat sink. The numerical simulation is based on the source-based enthalpy
method with finite volume discretization. The temperature profiles obtained by simulation are compared to the cooling curves
measured experimentally in order to validate the current mathematical model. It is found that the simulation result matches
the experimental data with reasonable agreement. 相似文献
2.
Metal matrix composite (MMC) has been well known for its superior material properties compared with traditional composite.
A new method is introduced to improve the properties of MMC in the sense that the ends of the reinforcement phase of the composite
are allowed to extend out of the mold and cooled by a heat sink in order to promote the rate of heat transfer through the
fibers and promote the formation of primary alpha phase around the reinforcement. This paper presents the experimental results
obtained from the foundry in the University of Wisconsin-Milwaukee and some numerical simulation results of the solidification
process in the cast mold. 相似文献
3.
A numerical simulation for predicting the axial creep-rupture lifetime of continuous fiber-reinforced metal matrix composites is proposed, based on the finite element method. The simulation model is composed of line elements representing the fibers and four-node isoparametric plane elements representing the matrix. While the fibers behave as an elastic body at all times, the matrix behaves as an elasto-plastic body at the loading process and an elasto-plastic creep body at the creep process. It is further assumed in the simulation that the fibers are fractured not only in stress criterion but time-dependently with random nature. Simulation results were compared with the creep-rupture lifetime data of a boron-aluminum composite with 10% fiber volume fraction experimentally obtained. The simulated creep-rupture lifetimes agreed well with the averages of the experimental data. The proposed simulation is further carried out to predict a possibility of creep-rupture for the composite without time-dependent fiber breakage. It is finally concluded that the creep-rupture of a boron-aluminum composite is closely related with the shear stress relaxation occurring in the matrix as well as time-dependent fiber breakage. 相似文献
4.
Binxin Yang Jie Ouyang Xuejuan Li 《ournal of non Newtonian Fluid Mechanics》2011,166(19-20):1129-1136
A dynamic simulation of fiber reinforced composite materials mold filling process with double inlets is presented based on the gas–solid–liquid model proposed by Yang et al. [B.X. Yang, J. Ouyang, J. Tao, C.T. Liu, Modeling and simulation of fiber reinforced polymer mold filling process by level set method, CMES – Computer Modeling in Engineering and Sciences 63 (3) (2010) 191–222]. Numerical results show that the fibers far away from the melt interface are in skin-core-skin structure, while those near the interface are almost parallel to the arc of the interface. When the two streams of melts meet, the weld line will be formed, where the orientation of fibers is perpendicular to the flow direction. The orientation of fibers of the numerical result shows well agreement with the experimental results. Finally, the mechanical properties of fiber reinforced composite materials are analyzed. The composite materials with skin-core-skin structure are regarded as laminated orthogonal plywood and the elastic modulus, the shear modulus and Poisson’s ratio are predicted under different slenderness ratios and fiber volume fractions. 相似文献
5.
In order to obtain the inter-yarn friction coefficient in aramid fibers, a new methodology is developed. Experimental yarn pull-out test and 3D numerical model have perfomed in Kevlar®129 (K129) aramid. An optimization of classic numerical models in order to simulate pull-out tests and obtain the inter-yarn friction is carried out. Numerical simulation results were compared to experimental yarn pull-out curves and based on linear dependence of the pull-out load with the friction coefficient, the inter-yarn friction coefficient of K129 aramid has been obtained. 相似文献
6.
Hamdy Hassan Nicolas Regnier Guy Defaye 《International Journal of Heat and Fluid Flow》2009,30(6):1218-1229
Injection molding is one of the most widely used plastic part processing. The quality of the injection molded part is a function of plastic material, part geometry, mold structure and process conditions. Gate location is among the most critical factors in achieving dimensionally accurate parts and high productivity of the molding process. To investigate the effect of the gate location on the cooling of polymer by injection molding, a full three dimensional time-dependent analysis is carried out for a mold with cuboids-shape cavity having two different thicknesses. The cooling of the polymer material is carried out by cooling water flowing inside six horizontal circular channels. Three gate locations are assumed, normal to the cavity surface, normal to the small thickness of the cavity, and normal to the large thickness of the cavity. A numerical model by finite volume is used for the solution of the physical model. A validation of the numerical model is presented. The results show that the gate location normal to the small thickness of the cavity achieves the minimum time required to completely solidify the product and minimum solidification of the product during the filling stage. They also indicate that the temperature distribution through the output product is greatly affected by the position of the injection gate location. 相似文献
7.
8.
The interfacial heat transfer coefficient (IHTC) is necessary for accurate simulation of the casting process. In this study,
a cylindrical geometry is selected for the determination of the IHTC between aluminum alloy casting and the surrounding sand
mold. The mold surface heat flux and temperature are estimated by two inverse heat conduction techniques, namely Beck’s algorithm
and control volume technique. The instantaneous cast and mold temperatures are measured experimentally and these values are
used in the theoretical investigations. In the control volume technique, partial differential heat conduction equation is
reduced to ordinary differential equations in time, which are then solved sequentially. In Beck’s method, solution algorithm
is developed under the function specification method to solve the inverse heat conduction equations. The IHTC was determined
from the surface heat flux and the mold surface temperature by both the techniques and the results are compared. 相似文献
9.
The problem of attenuating the noise from weapons firing is studied experimentally and numerically. As a possible method of attenuating the noise significantly, a silencer with no internal baffles is attached to the M242 cannon. The internal pressures inside the muffler are measured. The near-field overpressures outside the muffler at various polar angles are also measured. A numerical simulation of the flow through the muffler is performed, using Harten's shock-capturing method to solve the Euler equations of ideal compressible flow. The numerical simulation yields a detailed picture of the flow field as displayed by the pressure and Mach contours. Pressure–time curves at selected locations are obtained and compared with experimental data. There is good agreement, except that the numerical simulation generates more vigorous oscillations. 相似文献
10.
The objective of this study relates to the numerical simulation of the free surface during the two-dimensional flow and solidification
of aluminum in the horizontal cylinder and mold cavity of the high pressure die casting HPDC machine with cold chamber. The
flow is governed by the Navier–Stokes equations (the mass and the momentum conservations) and solved in the two phase’s liquid
aluminum and air. The tracking of the free surface is ensured by the VOF method. The equivalent specific heat method is used
to solve the phase change heat transfer problem in the solidification process. Considering the displacement of the plunger,
the geometry of the problem is variable and the numerical resolution uses a dynamic grid. The study examines the influence
of the plunger speed on the evolution of the interface aluminum liquid–air profile, the mass of air imprisoned and the stream
function contours versus time. Filling of a mold is an essential part of HPDC process and affects significantly the heat transfer
and solidification of the melt. For this reason, accurate prediction of the temperature field in the system can be achieved
only by including simulation of filling in the analysis. 相似文献
11.
为改善传统卡尔曼滤波KF(Kalman filter)算法在过程噪声方差和测量噪声方差未知的情况下响应重构精度降低甚至发散的问题,提出了一种基于新息自适应卡尔曼滤波IAKF(innovation-based adaptive Kalman filter)算法的多类型响应重构方法。首先根据新息统计特性对卡尔曼滤波增益和状态估计误差协方差矩阵进行实时自适应调整;然后利用有限测点的加速度传感器的测量数据,结合模态法对结构各个位置的加速度、速度、位移以及应变进行响应重构;最后对起重机桁架和简支梁分别进行数值模拟和试验分析。结果表明,该方法能够有效地调整过程噪声方差并估计测量噪声方差,未测点的重构响应时程曲线与计算响应或测量响应时程曲线吻合良好。 相似文献
12.
The effect of shock pressures on the inactivation of a marine Vibrio sp. was studied experimentally and numerically. In the experiment, an aluminum impactor plate accelerated by a gas gun was
used to induce shock waves in a sealed aluminum container with cell suspension liquid inside. The shock pressures in the container
were measured by a piezofilm gauge. Several 10–100 MPa of pressure were measured at the shock wave front. An FEM simulation,
using the Johnson–Cook model for solid aluminum and the Tait equation for the suspension liquid, was carried out in order
to know the generation mechanism of shock pressures in the aluminum container. The reflection, diffraction and interaction
of shock waves at the solid–liquid boundaries in the aluminum container were reasonably predicted by the numerical simulation.
The changes in shock pressures obtained from the computational simulation were in good agreement with those from the experiment.
The number of viable cells decreased with the increase of peak pressures of the shock waves. Peak pressures higher than 200 MPa
completely inactivated the cells. At this pressure, the cell structures were deformed like the shape of red blood cells, and
some proteins leaked from the cells. These results indicate that the positive and negative pressure fluctuations generated
by shock waves contribute to the inactivation of the marine Vibrio sp.
相似文献
13.
In the present work, shear-compression specimen was successfully employed to study the shear flow behavior of AZ31 magnesium alloy at high temperatures and in quasi-static regime. The loading process of shear-compression testing was simulated using ABAQUS software. This was carried out in the temperature range of 250–450°C and displacement rates of 1.5, 15 and 150 mm/min. In addition, to validate the numerical simulation results, the shear compression specimens were also compressed experimentally at the same conditions of numerical ones. Equivalent stress–strain curves obtained from numerical simulation results along with microstructural observations were utilized to investigate the effect of loading conditions on deformation behavior of the experimental alloy. The results indicated a homogenous distribution of shear strains within the gage and the high applicability of shear-compression specimen to study shear flow behavior of materials at hot deformation conditions. 相似文献
14.
ZhangZhen WangJian ShenYapeng 《Acta Mechanica Solida Sinica》2003,16(4):334-344
A micromechanics method based on the High-Order-Theory developed by Aboudi et al. is used to predict the thermomechanical response of composites reinforced by shape memory alloy (SMA) fibers, and the non-uniform thermal distribution in composite arising from the process of heating or cooling is considered. The numerical development based on this model was coded to predict the thermomechanical response of shape memory alloy fiber/elastomer matrix composite subjected to thermal cycle loading. When the composite is heated, two heating ways, thermal gradients and heat source by passing an electric current through the SMA fibers are imposed on the composite respectively. Upon cooling, the first thermal boundary condition and the second thermal boundary condition are subjected to the composite respectively. A series of stress distributions and temperature distributions for different instants are calculated to reveal the interaction between the SMA material and matrix. It is useful to analyze and design the SMA actuator driven by heat source or the surface temperature. 相似文献
15.
M. Larsson A. Needleman V. Tvergaard B. Storåkers 《Journal of the mechanics and physics of solids》1982,30(3):121-154
Forlong, ductile, thick-walled tubes under internal pressure instabilities and final failure modes are studied experimentally and theoretically. The test specimens are closed-end cylinders made of an aluminum alloy and of pure copper and the experiments have been carried out for a number of different initial external radius to internal radius ratios. The experiments show necking on one side of the tubes at a stage somewhat beyond the maximum internal pressure. All tubes, except for one aluminum alloy tube, failed by shear fracture under decreasing pressure. The aluminum alloy tubes exhibited localized shear deformations in the neck region prior to fracture and also occasionally surface wave instabilities. The numerical investigation is based on an elastic-plastic material model for a solid that develops a vertex on the yield surface, using representations of the uniaxial stress-strain curves found experimentally. In contrast to the simplest flow theory of plasticity this material model predicts shear band instabilities at a realistic level of strain. A rather sharp vertex is used in the material model for the aluminum alloy, while a more blunt vertex is used to characterize copper. The theoretically predicted bifurcation into a necking mode, the cross-sectional shape of the neck, and finally the initiation and growth of shear bands from the highly strained internal surface in the neck region are in good agreement with the experimental observations. 相似文献
16.
17.
This paper reports an investigation of three-dimensional stresses in models of composite materials with discontinuous fibers using the scattered-light photoelastic method. A special scattered-light polariscope with loading system was designed and constructed for this research. Two models were used in this investigation. The first was a cylindrical tension model with a single discontinuous axially aligned aluminum fiber surrounded by a polyester matrix. The second was a five-fiber cylindrical compression model with a central discontinuous fiber surrounded by four continuous ones and polyester matrix. The experimentally determined stress distribution from each model along chosen lines was presented. The stress distribution on the same lines in the single-fiber case was calculated using the finite-element method. The calculated result showed fair agreement with the experimentally determined results. 相似文献
18.
19.
Predictions based on a numerical simulation of a natural draft dry cooling tower (NDDCT) has been compared with those obtained theoretically and experimentally. Experiments are conducted in a lab-scale NDDCT and are validated with a three-dimensional numerical simulation of the flow in and around the heat exchangers, which is modelled as a porous medium. Both vertical and horizontal arrangements of the heat exchangers are examined. The experimental, numerical and theoretical approaches lead to very close prediction for the air velocity and temperature at the exit of the cooling tower. Results of this study are expected to be useful for future work on the development of air-cooled condensers for geothermal power plants in Australia. 相似文献
20.
《International Journal of Solids and Structures》2006,43(17):5110-5131
The behaviour of a self-piercing riveted connection was investigated experimentally and numerically. An extensive experimental programme was conducted on elementary riveted joints in aluminium alloy AA6060 in two different tempers, T4 and T6. The experimental programme was focused on the influence of important model parameters such as thickness of the plates, geometry of the specimens, material properties of the plates and loading conditions. An accurate 3D numerical model of different types of riveted connections subjected to various loading conditions was generated based on the results of the numerical simulation of the riveting process. A new algorithm was generated in order to transfer all the information from the 2D numerical model of the riveting process to the 3D numerical model of the connection. Thus, the 3D model was initialized with the proper deformed shape and the current post-riveting stress–strain state. The residual stresses and the local changes in material properties due to the riveting process were an important factor in order to get the correct structural behaviour of the model. The simulations have been carried out using the explicit finite element code LS-DYNA. The model was validated against the experimental results in order to get the correct deformation modes and the force–displacement characteristics. The numerical force–displacement curves fitted the experimental ones with reasonable accuracy. Furthermore, the model seemed to be able to describe the correct structural behaviour and thus the failure mechanisms of the self-piercing riveted connections. 相似文献