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1.
The maximum stresses in a plane-stressed component typically occur on the boundary. However, it is generally difficult to obtain reliable experimental data at an edge and thermoelastic stress analysis is no exception. The inability to measure reliable edge isopachic stresses has caused many previous thermoelastic stress analyses to be more qualitative than quantitative. This paper develops and implements an effective iterative least-squares method for calculating reliable edge isopachic stresses from measured interior values. The method is based upon the plane-stress isotropic compatibility equation. A regularization scheme is employed to minimize the sensitivity to measurement error and to improve the stability of the algorithm by controlling the rate of convergence. An illustrative example with actual measured thermoelastic data is included. The processes thermoelastically determined results compare well with those obtained using strain gages.Paper was presented at the 1994 SEM Spring Conference held in Baltimore, MD on June 6–8. 相似文献
2.
This paper describes the verification of the accuracy of residual stress measurement by the hole-drilling method. The strain measurement is simulated by the use of the indirect fictitious-boundary integral method. As an example, a finite rectangular plate subjected to initial stress is treated, and a simulated measurement of the residual stress is made using the strain relieved during hole drilling. The accuracy of residual stress measurement is estimated by comparing the simulated measured residual stress with the actual residual stress, i.e., the given initial stress. The results are shown for various distances and angles of strain gages. Also, the influences of the eccentricity of the hole from the center of the strain gages and the effect of a boundary near the hole are examined. 相似文献
3.
The hole-drilling method is a residual-stress measurement technique in which a blind hole (usually 1.6 mm or 3.2 mm in diameter) is drilled into a material and the strain perturbances around the hole are measured by surfacemounted strain gages. The conventional hole-drilling-method procedure is to analyze the net strain changes due to the drilling of the full-depth hole (usually about 100 percent of hole diameter) and to interpret the resulting stress calculations insofar as they represent the average stresses through the hole depth. It has been determined that this procedure may lead to significant errors, particularly where there are large stress variations through the hole depth. Such errors may be difficult to detect simply by observing the strain data. This paper describes a finite-element procedure which was used to develop calibration constants to allow measurements of residual-stress variation with depth to be routinely performed by the hole-drilling method. 相似文献
4.
Experimental and finite-element analyses are presented for the anisotropic states of stress, strain and fracture of a glass-epoxy plate containing a circular hole and subjected to uniaxial tension. Strains were experimentally measured using foil gages, moiré and birefringent coating. Stresses are computed in the linear range from the measured strains. While the hole reduces the plate strength by a factor of two, the maximum tensile strain at fracture is greater than the ultimate strain in a plate without a hole. Fracture consists of crack initiation at the hole boundary but off the horizontal axis. Away from the hole, failure is accompanied by considerable delamination. Discontinuous crack propagation is present. 相似文献
5.
6.
S.-J. Lin S. Quinn D. R. Matthys A. M. New I. M. Kincaid B. R. Boyce A. A. Khaja R. E. Rowlands 《Experimental Mechanics》2011,51(6):797-814
Thermoelastic data are combined with an Airy stress function to determine the individual stresses on and near the boundary
of a circular hole which is located below a concentrated edge-load in a plate. Coefficients of the stress function are evaluated
from the measured temperatures and the local traction-free conditions are satisfied by imposing srr = trq = 0 {\sigma_{r{\rm{r}}}} = {\tau_{r\theta }} = 0 analytically on the edge of the hole. The latter has the advantage of reducing the number of coefficients in the stress function
series. The method simultaneously smoothes the measured input data, satisfies the local boundary conditions and evaluates
individual stresses on, and in the neighbourhood of, the edge of the hole. Attention is paid to how many coefficients to retain
in the stress function series. Although the presence of high stress concentration factors, together with a hole-diameter-to-plate-thickness
ratio of only two, result in some three-dimensional effects, these are relatively small and the agreement between the thermoelastic
values, those from recorded strains and FEM-predicted surface stresses is good. 相似文献
7.
Realistic Cold Expansion Finite Element Model and Experimental Validations for Aluminium Alloys 总被引:1,自引:0,他引:1
Maxime Lapalme Majid Hoseini Philippe Bocher Alain R. Colle Martin Lévesque 《Experimental Mechanics》2014,54(5):841-855
Accurate understanding of the residual stresses produced by cold expansion (CX) of rivet holes is required for fatigue considerations, as well as for better addressing the loading problems in aerospace parts. This paper presents a physically based finite element (FE) model for predicting the residual stresses in aluminium parts submitted to CX. The model relies on experimental measurements for both construction and validation purposes. The model predictions were compared against the experimental results delivered by three different complementary techniques: Digital Image Correlation (DIC) (provided strain fields on the surface of the workpiece); X-Ray Diffraction (XRD) (provided residual stresses measurements on the surfaces); Microscopy measurements (measured the out-of-plane displacement on the hole bore). The FE model proves to be in good agreement with the experimental data. Further considerations on the simulation method regarding geometries, boundary conditions and friction effect are also discussed. 相似文献
8.
The analysis of plane-stress conditions using strain gages is feasible even when the deformations of the materials are in the elasto-plastic range. The calculation of stresses from the measured strain values is based on an analysis which requires knowledge of the stress-strain curve of the material as obtained from a uniaxial tensile test. In this paper, the practical procedure of such an analysis is described together with the application of a nomograph to allow a simplified evaluation to be made of the results of measurements. A numerical example is also given. 相似文献
9.
Jia-yong Wang 《Experimental Mechanics》1988,28(4):355-358
When a hole is drilled at any position with respect to the gages in a thin plate, a general relationship of relieved strain as a function of residual stress is presented. A simple and explicit solution for the principal residual stresses and their directions is also presented. This solution is available for the center or off-center hole-drilling cases and for the case of which the array of gages is arbitrary. 相似文献
10.
Alois L. Schlack Jr. 《Experimental Mechanics》1968,8(2):69-74
Experimentally determined critical loads are presented for simply supported square plates with a circular central hole under the action of uniform edge displacements for hole diameters varying up to seventenths the dimension of the plate. The critical load is defined as the inflection point on the load-deflection curve as measured by a set of dial gages at the edge of the hole. Least-squares-curve fitting techniques are used for reducing all experimental data and the entire set of computations is carried out on the electronic digital computer. Finally, it is shown that the experimental results agree well with the theoretical critical loads as determined by the Ritz energy method. 相似文献
11.
Austenitic stainless steel cylinders and rings are spray water quenched to create residual stresses at or greater than the yield strength. The residual stresses are measured using neutron diffraction, and two mechanical strain relaxation methods: deep hole drilling and incremental centre hole drilling. This paper compares the measurements with predictions of quenching using finite element analysis. Also finite element analysis is used to mimic deep hole and incremental centre hole drilling methods and to reconstruct residual stresses as if they have been measured. The measurements reveal similar trends to the predictions but there is only limited agreement between their magnitudes. However, there is better agreement between the reconstructed stresses and the measurements. Both the two mechanical strain relaxation methods reveal that large discrepancies occur between measurements and predictions arise because of plasticity. Irrespective of this and surprisingly there is good agreement between deep hole drilling and neutron diffraction measurements. 相似文献
12.
G. U. Oppel 《Experimental Mechanics》1961,1(3):65-73
New photoelastic strain gages are described which are self-contained and give an accurate direct indication of magnitudes and directions of principal stresses. Large numbers of gages may be observed simultaneously and critical areas of members may be readily located. Various types of gages are applicable to high-termperature problems, dynamic measurements or direct photographic recording. 相似文献
13.
14.
A theoretical approach is presented that uses multiple strain gages to accurately measure complicated strain distributions.
The technique is based on the method of weighted residuals in conjunction with measured strain data and is applicable for
arbitrary in-plane strain distributions. Conventional measurements using strain gages are shown to represent a particular
case of the approach presented. The experimental characterization of unidimensional strain fields is discussed in detail.
Two approaches are presented; these are based on linear and quadratic approximations of the strain field. The strain distribution
for two important practical problems is evaluated assuming ideal conditions to assess the performance of the proposed approach.
In both cases, the simulated results demonstrate that measurement error resulting from the finite size of a strain gage may
be reduced. That is, a larger strain gage may be used for a given maximum admissible error. The method also allows a minimal
error of measured nonlinear strains. 相似文献
15.
This paper presents measurements of the bulk residual stresses in 100-mm (4-in.) and 250-mm (10-in.) diam Schedule 80 piping weldments using strain-relief techniques. Both laboratory-welded specimens and field-welded specimens from reactors in service were studied. Axial bulk residualstress distributions were obtained at 45-deg intervals around the circumference. At each azimuthal position, the residual stresses were measured at seven axial positions: on the weld center line and 13, 20 and 25 mm to either side of the weld center line, on both the inside and outside surface. The specimens were parted out using a wire-feed electric-discharge machine, and the resulting strain relief was measured with electrical-resistance strain gages (120-deg rosettes). The bulk residual stresses obtained on the inside surface of the 100-mm weldments exhibit an oscillatory distribution with peak values above 275 MPa (40 ksi) and stress gradients normal to the weld on the order of 35 MPa/mm (127 ksi/in.). 相似文献
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17.
In this study, the vertical soil reaction acting on a driven wheel was measured by strain gages bonded to the left rear axle of a 2WD tractor driven under steady-state condition on different soil surfaces, tractor operations, and combinations of static wheel load and tire inflation pressure. In addition, the measurements of radial and tangential stresses on the soil–tire interface were made simultaneously at lug’s face and leading side near the centerline of the left rear tire using spot pressure sensors. The experimental results indicate that the proposed method of vertical soil reaction measurement is capable of monitoring the real-time vertical wheel load of a moving vehicle and provides a tool for further studies on vehicle dynamics and dynamic wheel–soil interaction. Furthermore, the measured distributions of soil stresses under tractor tire could provide more real insight into the soil–wheel interactions. 相似文献
18.
Isaac M. Daniel 《Experimental Mechanics》1980,20(1):1-8
An experimental investigation was conducted to study the behavior under biaxial tensile loading of quasiisotropic graphite/epoxy plates with circular holes and to determine the influence of hole diameter on failure. The specimens were 40 cm×40 cm (16 in.×16 in.) laminates of [0/±45/90] s layup. Four hole diameters, 2.54 cm (1.00 in.), 1.91 cm (0.75 in.), 1.27 cm (0.50 in.) and 0.64 cm (0.25 in.), were investigated. Deformations and strains were measured using strain gages and birefringent coatings. Equal biaxial loading was introduced by means fo four whiffle-tree grip linkages and controlled with a servohyraulic system. Initially, the circumferential strain is uniform around the boundary of the hole. Subsequently, with increasing load, regions of high strain concentration with nonlinear response develop at eight characteristic locations 22.5 deg off the fiber axes. Failure in the form of cracking and delamination initiates at these points. Maximum strains at failure on the hole boundary reach values up to twice the ultimate strain of the unnotched laminate. The effect of hole diameter on strength was described satisfactorily using an average biaxial-stress criterion. Good correlation was also obtained with theoretical predictions based on a tensor-polynomial failure criterion for the lamina and a progressive degradation model. 相似文献
19.
The elastoplastic state of thin spherical shells with an elliptic hole is analyzed considering that deflections are finite.
The shells are made of an isotropic homogeneous material and subjected to internal pressure of given intensity. Problems are
formulated and a numerical method for their solution with regard for physical and geometrical nonlinearities is proposed.
The distribution of stresses (strains or displacements) along the hole boundary and in the zone of their concentration is
studied. The results obtained are compared with the solutions of problems where only physical nonlinearity (plastic deformations)
or geometrical nonlinearity (finite deflections) is taken into account and with the numerical solution of the linearly elastic
problem. The stress—strain state in the neighborhood of an elliptic hole in a shell is analyzed with allowance for nonlinear
factors
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Translated from Prikladnaya Mekhanika, Vol. 41, No. 6, pp. 95–104, June 2005. 相似文献
20.
J. C. P. Pina A. M. Dias P. F. P. de Matos P. M. G. P. Moreira P. M. S. T. de Castro 《Experimental Mechanics》2005,45(1):83-88
In this paper we present the methods of determination and the stress obtained at the periphery of a cold expanded hole in
a 2024-T3 Alclad aluminum alloy sheet. The measurements in the aluminum clad were performed by the sin2Ψ method, taking experimental precautions to deal with the texture effects. In the core aluminum a special method had to be
implemented to determine the stress values in a direction not accessible to the X-ray diffraction. The strains were measured
in sample orientations selected according to the texture characteristics and stress factorsF
ij
were used to calculate the stress tensor. TheF
ij
values were determined assuming a quasi-isotropic material behavior, after concluding that the stress results were not significantly
affected by factors calculated for textured material. The residual stress profile, both in the clad and in the sheet, shows
a nearly axisymmetric stress state. Compressive stresses were observed near the periphery of the hole, with values that are
higher on the exit than on the entrance face. Residual stresses were also higher in the hoop direction than in the radial
direction. They decreased with the radial distance to the hole and affected the previous stress state over a distance of 6
mm. The plastic deformation induced by the cold expansion is well evidenced by the FWHM values, which in the affected zone
decrease with increasing distance from the hole edge. 相似文献