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Calculation of residual stresses in injection molded products 总被引:3,自引:0,他引:3
Prof. dr. ir. F.P.T. Baaijens 《Rheologica Acta》1991,30(3):284-299
Both flow- and thermally-induced residual stresses which arise during the injection molding of amorphous thermoplastic polymers are calculated in the filling and post-filling stage. To achieve this, a compressible version of the Leonov model is employed. Two techniques to calculate flow-induced residual stresses are investigated. First, a direct approach is developed where the pressure problem is formulated using the viscoelastic material model. Second, generalized Newtonian material behavior is assumed in formulating the pressure problem, and the resulting flow kinematics is used to calculate normal stresses employing the compressible Leonov model. The latter technique gives comparable results, while reducing the computational cost significantly. 相似文献
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A general form for calculating residual stresses detected by using the holographic blind-hole method
A general form used for analyzing residual stresses measured using the holographic blind-hole method is introduced in this
paper. Adopting the general form presented, the residual stresses can be obtained using three relative displacements measured
from a single interference fringe pattern. Even for the case in which phase-shifting holographic interferometry is not employed,
interpolating calculations for determining the fringe orders are not needed, since the choice of data points becomes more
flexible when using this general form. Two experiments, the first one carried out by the authors and the second one published
previously, are used to illustrate the applicability and usefulness of this general form. Suggestions for the applications
of this general form are also established via the upper bound error estimations. 相似文献
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Mathieu Girinon Frédéric Valiorgue Habib Karaouni Éric Feulvarch 《Comptes Rendus Mecanique》2018,346(8):701-711
Drilling can affect the integrity of the surface of a mechanical component and reduce its fatigue life. Thus, drilling parameters such as lubrication or drilling velocity must be optimized to ensure a satisfactory residual mechanical state of the hole surfaces. Unfortunately, experimental tests are time consuming and it is not easy to observe the cutting process because of the confinement of the drill zone. The literature does not exhibit any numerical simulation capable of simulating 3D thermomechanical phenomena in the drill zone for large depth holes. Therefore, residual stresses cannot be easily simulated by means of the sole drilling parameters. The aim of this article is to propose a new numerical approach to compute drilling residual stresses for large-depth holes. A first simulation is developed to simulate heat transfer by means of a 3D thermoviscoplastic simulation in a new Rigid-ALE framework allowing the use of large calculation time steps. Then, a time interpolation and a spatial projection are implemented to rebuild the Lagrangian thermal history of the machined component. Finally, a thermo-elastoplastic simulation is carried out to compute residual stresses in the final workpiece. In this paper, the method is applied to a 316L austenitic stainless steel in the case of an unlubricated hole. The computed residual stresses are compared to experimental measurements. 相似文献
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The theoretical foundation of the photoelastic methods being presently used for measuring and analyzing residual stresses in glass is insufficient for studying development of transient viscoelastic stress states in glass plates during tempering process and for an explanation of the actual material behavior. It is shown that the basic knowledge of photoviscoelastic effect in glass over a wide range of electromagnetic radiation and temperature is necessary for such on analysis. Some photoelastic properties of plate glass are presented. 相似文献
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搅拌摩擦焊接残余应力及残余变形数值分析 总被引:1,自引:0,他引:1
建立了搅拌摩擦焊接顺序热力耦合有限元模型,用移动热源模拟搅拌头的作用,对搅拌摩擦焊接进行数值模拟.瞬态温度场及残余应力场与试验结果吻合良好,从而验证了该模型的正确性.本文研究了焊接过程中应力变化过程,指出应力场的不均匀分布引起板的弯曲变形.建立了不同尺寸有限元模型,研究板的尺寸对残余变形的影响.板的宽度对纵向残余变形曲率影响较大,长度对变形曲率影响较小.当焊接长度足够长,模型宽度相同时,不同模型远离端部区域纵向弯曲曲率相同.板的横向残余变形主要由焊缝区域变形引起,远离焊缝区域几乎没有弯曲变形发生,且板的尺寸对变形曲率影响很小. 相似文献
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An acoustoelastic method for residual stress measurement in slightly orthotropic materials by using ultrasonic longitudinal and shear waves is presented. A shear transducer with small vibrator 2 × 2mm2 is developed and described, and the measurement of 2-D residual stresses in a seam welded plate was carried out by this method with the shear transducer developed.This project was supported by National Natural Science Fundation of China 相似文献
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A general model for predicting the total residual stresses generated during filling and cooling stages of injection-molded parts has been developed. The model takes into account the phenomena associated with non-isothermal stress relaxation. The main hypothesis in our approach is to use the kinematics of a generalized Newtonian fluid at the end of the filling stage as the initial state for the calculation of residual flow stresses. These stresses are calculated using a single integral rheological model (Wagner model). The calculation of stresses developed during the cooling stage is based on a thermoviscoelastic model with structural relaxation. Illustrative results emphasizing the effect of both the melt temperature and the flow rate during the filling stage are presented. 相似文献
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The same shot-peening treatment was applied to five steels with different mechanical properties. The induced residual stress profiles were analyzed using X-ray diffraction and incremental hole drilling (IHD). The results of both techniques showed that IHD can still be successfully used for measuring shot-peening residual stresses, even if these exceed the yield strength of the bulk material. Expected errors due to the plasticity effect are reduced by the strain hardening of the surface. For an assessment of the reliability of IHD data, strain-hardening variation was quantified by microhardness measurements to estimate the yield strength of the plastified layer. All the main calculation methods for IHD were applied. The results were compared and discussed with respect to the characteristics of each method. 相似文献
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Assessing the effect of residual stresses on the fatigue behavior of integrally stiffened structures
G. Labeas I. Diamantakos Th. Kermanidis 《Theoretical and Applied Fracture Mechanics》2009,51(2):95-101
Residual stresses emerge quite often in real structures due to the various manufacturing processes such as, welding, forming, cutting, milling, etc. In such cases, development of cracks at regions influenced by manufacturing operations demand additional attention. In the present work a numerical methodology has been developed, based on three-dimensional Finite Element Analysis, for the calculation of Stress Intensity Factors at cracks in welded components. The residual stress fields, which are used in SIF calculations, have been computed by the numerical simulation of the thermo-mechanical process. A numerical algorithm based on interpolation principles is developed, in order to introduce the three-dimensional field in the computational model of the cracked structure. The SIF calculation methodology is initially validated for the case of a welded plate by comparison of numerical results with existing analytical solutions. A cracked stiffened panel is analysed afterwards and the calculated fatigue crack propagation results are compared to experimentally measured data. Finally, the numerical procedure is applied to study the effect of more complicated residual stress fields on SIF values developing at cracks located in stiffened panels. 相似文献
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Summary This paper outlines an analytical method for computing normal and shear stresses generated in a curved laminated beam under
bending loads. Each cross section is assumed to be symmetrical and loads are applied in the plane of symmetry. We build a
statically admissible stress field in order to plot normal and shear stress distributions.
Received 5 March 1997; accepted for publication 18 September 1997 相似文献
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J. F. Cárdenas-García S. Ekwaro-Osire J. M. Berg W. H. Wilson 《Experimental Mechanics》2005,45(4):301-313
The hole method problem relates to two inverse problems of interest: the first, most commonly addressed by practitioners,
is to obtain residual stresses; the other, generally neglected, inverse problem can be posed as either a stress separation
problem or a material elastic properties identification problem. In both this Paper I and Paper II, we pose and solve this
dual hole method problem in an orthotropic plate, using computer generated moiré isothetics, by means of a non-linear least-squares
approach. In Paper I we address the residual stress problem. In Paper II we pose the use of moiré isothetics as a means to
achieve separation of stresses, but we deal with the determination of the five orthotropic elastic constants, four of which
are independent. 相似文献
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A photoelastic study was conducted to examine the stress fields in the cutting process of fiber-reinforced plastics (FRPs). Force measurements were made and used in the analysis of the stress fields. Machined surfaces of workpieces with fibers oriented away from the cutting direction showed that the fibers were machined by shearing and tensile fracture; and when fibers were inclined towards the cutting tool, the fibers failed by shearing and bending. In addition, fiber-matrix debonding was observed to be maximum for fibers oriented at 45 deg towards the tool's path. Fiber orientation was shown to have an influence on the machining forces and stresses.Paper was presented at the 1994 SEM Spring Conference held in Baltimore, MD on June 6–9. 相似文献
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Hybrid experimental-numerical concept of residual stress analysis in laser weldments 总被引:1,自引:0,他引:1
The concept, methodology and instrumentation for hybrid experimental-numerical residual stress analysis in a laser weldment are presented. Grating interferometry and digital speckle photography are applied as complementary experimental methods for the determination of the initial model of residual strains and of the material properties at the various zones of a laser weldment. These data inserted into a finite element model enable one to analyze the formation of the residual stress state of the object, which is compared and modified by means of experimental data in a closed iterative loop. This full hybrid approach is tested successfully on a laser-welded steel specimen in uniaxial tensile tests. 相似文献
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Experimental Techniques - The analysis of residual stress in glass is usually carried out by means of photoelastic methods. This article considers the automation of the white light photoelastic... 相似文献
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This paper presents a numerical prediction of the formation of Goertler vortices on a concave surface with suction and blowing. Suction stabilizes the boundary layer flow on the surface, whereas blowing destabilizes the flow. The criterion on the position marking the onset of Goertler vortices is defined in the present paper. For facilitating the numerical study, the computation is carried out in the transformed x–η plane. The results show that the onset position characterized by the Goertler number depends on the local suction/blowing parameter, the Prandtl number and the wavenumber. The value of the critical Goertler number increases with the increase in suction, while the value of the Goertler number decreases with the increase in blowing. Both the experimental and the numerical data can be correlated by Gθ*=10.2(a′θ)*3/2 without suction and blowing and by a simple relation G*x=(G*x)γ=0 e−γ with suction and blowing. The obtained critical Goertler number and wavenumber are in good agreement with the previous experimental data. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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In this paper,a new elimination of finite differential equations has been discussed.It applies the numerical direct iteration to obtain the residual equations,in which the number of unknowns has been reduced greatly.The solution process is simple and efficient,and the solution is exact 相似文献