共查询到20条相似文献,搜索用时 15 毫秒
1.
Static Vickers indentation tests were performed on Homalite specimens with an intent to obtain the residual stress distribution beneath the indentation. The indented specimens were placed in a circular polariscope to view the fringe patterns corresponding to the induced residual stress. Similitude analysis was later employed to identify the functional relationship between the various parameters related to an indentation test. The analysis resulted in a unified relationship that can assist in the determination of residual stress in nontransparent materials subjected to similar geometric and loading conditions. The shear stress contours provided here can also be used as guidelines to verify constitutive models under complex three-dimensional loads. 相似文献
2.
J.M. Antunes J.V. Fernandes N.A. Sakharova M.C. Oliveira L.F. Menezes 《International Journal of Solids and Structures》2007,44(25-26):8313-8334
The main difficulty with the characterization of thin coatings using depth-sensing indentation tests is related to the determination of the contributions of the substrate and the film to the measured properties. In this study, three-dimensional numerical simulations of the Vickers hardness test are used in order to examine the influence of the elastic and plastic properties of the substrate and the film on the composite’s Young’s modulus results. The hardness of the film is equal to or higher than the substrate hardness. A study of the stress distributions and the indentation geometry of composites, film/substrate, was performed, taking into account the relative mechanical properties of the film and substrate. In addition, stress evolution during indentation was studied, in order to quantify the critical indentation depth under which the substrate is not elastically deformed. The accurate evaluation of the Young’s modulus of the films using weight functions is also examined: some of these have previously been proposed and one was introduced for this study. Two different fitting procedures were used to compare the results obtained from eight fictive film/substrate combinations using six weight functions. The first procedure, commonly used, considers the substrate’s modulus as a known parameter in the fitting process. In the second, the film and the substrate’s modulus are considered as unknown variables that are calculated simultaneously during the fitting process. The validity of the conclusions obtained using the fictive materials was checked by applying the weight functions to four real composites. 相似文献
3.
A method for measuring the stress tensor of liquids obeying the stress-optical rule is presented. In particular, the procedure makes it possible to determine the shear stress, and the first and second normal stress differences for rheometric flows. This technique is an extension of the procedure recently described by Burghardt and coworkers (Brown et al., 1995) wherein light is sent obliquely through a sample sheared between transparent plates. However, in the present development, the light is transmitted in the plane containing the velocity gradient and neutral directions, thereby reducing the necessary optical measurements by one. A polystyrene-tricresyl phosphate (TCP) solution is used as the test sample. The first and second normal stress differences in steady shear flow measured by this method show good agreement with the mechanical results measured by Madga et al. (1993) using a modified cone and plate rheometer. The transient behavior of the first and second normal stress differences following the start-up of shear flow is also presented. 相似文献
4.
提出一种基于霍普金森压杆装置的动态球形压痕实验方法,通过将硬质合金小球置于2个试件中间,实现加载过程中2个试件的同时压入,以得到准确的压痕力与位移的关系。利用有限元软件ABAQUS/Explicit对该实验方法进行了数值模拟,从实验结果的可行性、准确性等方面,对新实验方法与传统的动态压痕实验方法进行了比较;采用新方法对铝合金材料进行了实验,并得到了压入力-位移曲线等关系。研究结果表明:采用新实验方法能得到较准确的结果,能较真实地描述压痕过程。 相似文献
5.
Prediction of strength using flat cylindrical indentation method 总被引:2,自引:0,他引:2
Strength of structural components is predicted. Two cases have been studied to explore the possibility of determining the damage level of the materials by the flat cylindrical indentation method with the help of the finite element method (FEM). The first uses the Gurson model for analyzing the elastic–plastic damage. The second uses the Katchanov–Robotnov law to predict the creep damage. The analytical results show that the damage levels can be determined by the flat cylindrical indentation experimental method. 相似文献
6.
7.
8.
IntroductionCreepisthetimedependentplasticdeformationofmaterialswhichischaracterizedbyastrongdependenceofthecreepratefromstressσonconstanttemperatureT .Thesecondarycreeprate εdependsonstressσas ε=Cc·σnC, ( 1 )whereCcisaconstant,nCisthecreepstressexponent.Th… 相似文献
9.
The measurement of the yield stress of liquids 总被引:1,自引:0,他引:1
M. Keentok 《Rheologica Acta》1982,21(3):325-332
An analysis has been made of different methods of measuring the yield stress of liquids. In the experimental program, a comparison is made of measurements of the yield stress using an Instron 3250 Rheometer in several geometries (cone-plate, parallel plate and eccentric disk) in shear flow and stress relaxation, a laboratory vane and a cone penetrometer. Good agreement has been obtained between the shear flow data and the laboratory vane, while stress relaxation appears to underestimate the yield stress. 相似文献
10.
硅晶体纳米压痕试验与应力场分析 总被引:5,自引:1,他引:5
采用纳米压入法测量了4种硅晶体的微压痕特性,讨论了加载过程与卸载过程的特征,分析了硅晶体的纳米压入测量结果,同时计算了硅晶体中的应力分布,计算结果表明,剪应力为硅晶体微薄片剥落失效的原因。 相似文献
11.
Analytical solutions of the creep and stress-relaxation boundary-value problems of a plate loaded externally along the contour of a circular hole are obtained using an unsteady creep model based on nonclassical representations for elastic and viscous properties of materials. It is assumed that one force component and one displacement component are specified at the boundary.__________Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 46, No. 4, pp. 146–153, July– August, 2005. 相似文献
12.
出于局部控制和健康安全监测的需要,为检测结构的损伤提供可能性,应用回传射线矩阵法,对方波脉冲作用下的有损伤连续梁进行损伤检测研究。连续梁结构的局部损伤用减小单元的杨氏模量来模拟。结果表明,当方波脉冲斜向作用时,通过结构上接收点处轴向速度波能准确判断损伤存在,确定损伤区域,估测损伤程度。 相似文献
13.
14.
The non-uniqueness of the atomistic stress tensor is a well-known issue when defining continuum fields for atomistic systems. In this paper, we study the non-uniqueness of the atomistic stress tensor stemming from the non-uniqueness of the potential energy representation. In particular, we show using rigidity theory that the distribution associated with the potential part of the atomistic stress tensor can be decomposed into an irrotational part that is independent of the potential energy representation, and a traction-free solenoidal part. Therefore, we have identified for the atomistic stress tensor a discrete analog of the continuum generalized Beltrami representation (a version of the vector Helmholtz decomposition for symmetric tensors). We demonstrate the validity of these analogies using a numerical test. A program for performing the decomposition of the atomistic stress tensor called MDStressLab is available online at http://mdstresslab.org. 相似文献
15.
We present a stress intensity factor (SIF) measurement method of cracks using a piezoelectric element and electrostatic voltmeter.
In the method, an isotropic piezoelectric element is first adhered near the crack tip. Then, the surface electrodes are attached
to the three different positions on the piezoelectric element. The electric potentials of the surface electrodes, which are
proportional to the strain sum (ɛx+ɛy) on the structural member, are measured by an electrostatic voltmeter during load cycling. Mode I and mode II SIFs of the
crack are estimated using the relationship between the SIF and (σx+σy). The applicability of the proposed method is examined through experiments and numerical analysis. 相似文献
16.
The present study deals with the development and the application of the through-hole drilling method for the residual stress
analysis in orthotropic materials. Through a systematic theoretical study of the stress field present on orthotropic plates
with a circular hole, the relationships between the relaxed strains measured by a rectangular strain gauge rosette and the
Cartesian components of the unknown residual stresses are obtained. The theoretical formulas of each influence coefficient
allow the user an easy application of the method to the analysis of uniform-residual stresses on a generic homogeneous orthotropic
material. Furthermore, to extend the method to the analysis of the residual stresses on orthotropic laminates, caused by initial
in-plane loadings, an alternative formulation is implemented. The accuracy of the proposed method has been assessed through
3D numerical simulations and experimental tests carried out on unidirectional, cross-ply and angle-ply laminates. 相似文献
17.
Railroad car wheels develop residual stresses both in their manufacture and once in service. Knowledge of residual stress
distribution and its variation over time is necessary for the prediction of wheel service life and possible catastrophic failure.
It is vital for the safety of railway transportation. Although a theoretical solution is possible, it remains complex. Alternatively,
the solution may be also obtained by using the experimental measurements assisted by the theory of mechanics. An approach
known as “physically based enhancement of experimental data” formulated, subsequently developed and tested provides the most
accurate results for the reconstruction of acquired residual hoop stress component in railroad car wheels. The paper presents
the formulation, solution approach and results of the analysis performed on experimental data registered in investigations
of the passenger and freight wheels during their saw-cutting process. The task has been formulated and solved as a nonlinear
constrained optimization analysis. The discussion on the results precision has been included. 相似文献
18.
AbstractThe article addresses development of the Transfer Matrix Method (TMM) for free vibration of cracked continuous Timoshenko beam made of Functionally Graded Material (FGM). The governing equations of free vibration are established for the beam based on the power law of material grading, actual position of neutral plane and double spring model of crack. There is conducted frequency equation of the beam with intermediate rigid supports using the TMM after the transverse displacements at rigid supports have been disregarded. Therefore, the frequency equation is simplified and becomes more useful to compute natural frequencies of continuous FGM Timoshenko beam with a number of cracks. The obtained numerical results show the essential effect of cracks, material properties and also number of spans on natural frequencies of the beam. 相似文献
19.
This paper presents repeated slitting method measurements of the residual stress versus depth profile through the thickness
of identically prepared samples, which were made to assess repeatability of the method. Measurements were made in five 17.8 mm
thick blocks cut from a single plate of 316L stainless steel which had been uniformly laser peened to induce a deep residual
stress field. Typical slitting method techniques were employed with a single metallic foil strain gage on the back face of
the coupon and incremental cutting by wire EDM. Measured residual stress profiles were analyzed to assess variability of residual
stress as a function of depth from the surface. The average depth profile had a maximum magnitude of −668 MPa at the peened
surface. The maximum variability also occurred at the surface and had a standard deviation of 15 MPa and an absolute maximum
deviation of 26 MPa. Since measured residual stress exceeded yield strength of the untreated plate, microhardness versus depth
profiling and elastic–plastic finite element analysis were combined to bound measurement error from inelastic deformation. 相似文献
20.
薄板坯连铸结晶器中铸坯凝固壳应力发展的有限元分析 总被引:9,自引:0,他引:9
对薄板坯连铸结晶中铸坯凝固壳应力的发展过程建立了有限元分析模型。在计算铸坯温度场和凝壳厚度分布的基础上用热弹粘性模型数值模拟了凝固壳中的应力发展过程,同时得到了凝壳断面从结晶器液池顶面到结晶器出口处的移支过程中各部位裂纹产生倾向的大小。模型中考虑了钢水静压力的作用和结晶器锥度,计算结果合理。 相似文献