共查询到20条相似文献,搜索用时 15 毫秒
1.
2.
3.
Yoshio Ohashi 《Experimental Mechanics》1973,13(7):287-293
In the photo-rheologic method used in this paper, the time-dependent creep strain rate and the instantaneous elastic-plastic strain rate are considered. Unlike ordinary photoplasticity, the strain history and the time dependence are accounted for in this stress analysis by characteristic values independent of strain rate. This method is also suitable for analyzing finite deformations. Using this method, the time-dependent deformations and stresses in a body can be analyzed with the same accuracy as photoelasticity from the instant of loading to the static-equilibrium state during plastic flow or creep. Fundamental concepts and procedures are described. Two examples are used to demonstrate possible applications of this method. 相似文献
4.
Douglas G. Ritchie 《Experimental Mechanics》1977,17(9):327-332
Immense steel and concrete platforms are being used for offshore oil production. Loads in these fixed-rigs, in floating-rig components and in production pipelines are being measured with strain gages and transducers. Certain of these offshore structures and typical testing which has been performed are discussed, including some using environmentally protected weldable strain gages. 相似文献
5.
B. L. Greenstreet F. J. Witt J. E. Smith R. L. Maxwell L. R. Shobe 《Experimental Mechanics》1963,3(6):129-139
The stresses from internal pressure in a nuclear-reactor pressure vessel were investigated using both strain-gaged and photoelastic models. The methods used in obtaining complete stress distributions along the nozzles from strain-gage data are described, and comparisons are made between the distributions obtained from the photoelastic model and those derived from strain-gage data. The effects of nonradial attachment of a nozzle to a spherical shell upon the stresses in the nozzle and in the shell are shown. Finally, comprisons are made between the experimental results and those for simplified analytical models. 相似文献
6.
安里千 《应用数学和力学(英文版)》1994,15(4):359-364
CCDAUTOMATEDPOLARISCOPESYSTEMANDTHESTRESSANALYSISMETHODSAnLi-qian(安里千)(PekingGraduateSchool.ChinaUniversityofMining)Beijing(R... 相似文献
7.
Wan-Ji Chen 《Acta Mechanica Solida Sinica》1990,3(3):301-306
A new functional which forms the basis of an improved hybrid element formulation is proposed. The variables for the functional include stresses, strains and displacements, and the displacements and stresses are further decomposed into two parts respectively. The proposed new formulation appears to be particularly suitable for improving conforming models.The relationship between the new hybrid elements and the conventional displacement elements are also explored in this paper. 相似文献
8.
A method is presented that determines photoelastic isochromatic values at the nodal points of a grid mesh which in turn is
generated by a computer program that accepts digitized input. Values of σ1 - σ2 are computed from the digitized fringe orders. The Laplace equation is solved to separate the principal stresses at each
nodal point. The method is extended to digitize isoclinics. Subsequently, σ
x
- σ
y
and τ
xy
are calculated to be used as starting values for the solution of the pertaining partial differential equations to enhance
convergence. For further accelerating the rate of convergence, superfluous boundary conditions are added from the digitized
data; significant improvement is demonstrated. Estimated values of σ
x
- σ
y
from the digitized data are further used in conjunction with the solution of the Laplace equation to determine the state
of stress without solving the boundary value problems.
Paper was presented at the 1988 SEM Spring Conference on Experimental Mechanics held in Portland, OR on June 5–10. 相似文献
9.
Displacement pattern matching and boundary-element methods for elastic-plastic stress analysis 总被引:1,自引:0,他引:1
A two-dimensional hybrid experimental-numerical technique for elastic-plastic stress analysis is presented. This technique results from merging two relatively new technologies in engineering mechanics: boundary-element methods and image processing. A syntactic pattern recognition scheme, termed displacement pattern matching (DPM), determines the displacement boundary conditions which are used in an elasticplastic boundary-element method (EPBEM) code. The result is an automated stress-analysis tool.Displacement pattern matching is a process where displacements are measured by tracking an arbitrary array of black spots on a white specimen. The digitized images of the specimen are compared in a double-exposure format to determine displacements. Displacement pattern matching is a full-field technique, with spatial resolution on the order of. 1 pixels.Displacement pattern matching supplies the actual specimen displacement increments to the EPBEM code which is based on a von Mises, isotropic work-hardening constitutive model. Given these displacements and free surface conditions, EPBEM is able to incrementally calculate the internal state of stress at selected locations. Results obtained for a variety of geometries and loading conditions compared well with ANSYS finite-element solutions and selected published experimental solutions and therefore are encouraging. 相似文献
10.
11.
E. K. Lynn 《Experimental Mechanics》1962,2(12):19A-23A
A design optimization of the cross section of a high-speed rotor to pump liquid hydrogen was accomplished by means of photoelastic evaluations and model tests. The photoelastic models were rotated in the field of a polariscope with stroboscopic light synchronized to this rotation to evaluate the stresses. Differential radial growths were measured from model tests. 相似文献
12.
Tadashi Nishitani 《Experimental Mechanics》1979,19(3):102-108
The proposed photoviscoplasticity is a method for determining the stress distribution in nonsteady inelastic deformation during creep. The governing fundamental relations are derived by considering the effect of time as involved in the viscoplastic strain rate and the stress rate, and by considering the distinctive deformation properties of celluloid as model material. The validity of the fundamental relations are evaluated according to calibration test by using celluloid. The proposed method is applied for two practical applications of the compression of blocks by elastic punches and the compression of strip having a circular hole or semicircular notches. The time-dependent variation of stress states can be analyzed with the same accuracy as in the photoelasticity. 相似文献
13.
The application of in-plane displacements to the boundaries of two-dimensional specimens is frequently associated with out-of-plane restraints. The state of strain developed at the boundaries when the displacements are applied mechanically, or thermally, is analyzed for several typical cases. The stresses associated with a knife-edge device used to eliminate out-of-plane restraints are also analyzed. 相似文献
14.
Donald G. Berghaus 《Experimental Mechanics》1991,31(1):36-41
Photoelastic data are combined with the finite-element method for stress solutions over regions partially bounded by free surfaces and axes of symmetry. Least-squares solutions are obtained without presumed values of applied forces at element nodes and without isoclinic data. Varied example problems are used to compare the results to independent photoelastic and finite-element solutions and to theoretical stress values.Paper was presented at the 1989 SEM Spring Conference on Experimental Mechanics held in Cambridge, MA on May 28–June 1. 相似文献
15.
Determination of stress intensity factors using shadow optical method of caustics attracts increasing attention. However, the reliability and ranges of applicability of this method are seldom discussed. This paper presents such an analysis regarding the reliability and predictive power of caustic method in fracture mechanics. This analysis is performed according to the accepted methodology of testing any analytical, numerical, or experimental procedure, namely by testing its theoretical bases. The following four basic assumptions of the shadow optical method of caustics in fracture mechanics, and their consequences, are analyzed: assumption of a generalized plane stress state near crack tip; assumption that the radiant energy used to produce shadow images propagates rectilinearly inside a stressed body; assumption that the light velocity inside a stressed body depends only on stress components in planes normal to wave normals; assumption that there is no alteration in state of polarization of radiation impinging upon a stressed plate at oblique incidence.The first two basic assumptions are tested using results obtained by means of three analytical-experimental procedures, namely isodynes, gradient index method, and classical strain gages. It is known that the inaccuracies of the fourth assumption are within the noise level only when the angles of incidence are small.It is shown that the magnitudes of the effects caused by the geometric lens effect and the gradient index lens effect are comparable, and that the stress states near crack tips and bottoms of notches, which produce the geometric lens effect, are clearly three-dimensional.It is also indicated that the gradient index lens effect is caused jointly by the stress/strain-induced alteration of the optical path and by the bending of the light path caused by strain gradient.Obtained empirical evidence shows the existence of a particular relationship between the observed gradient index lens effect and the order of singularity in a particular singular solution of linear fracture mechanics, with the exception of the vicinity of the crack tip where singularities are inadmissible. 相似文献
16.
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.
A. N. Guz 《International Applied Mechanics》2011,46(11):1213-1220
Results of the justification, development, and application of nondestructive ultrasonic methods of stress analysis are briefly
outlined (summarized). These are the results of cooperative research by the S. P. Timoshenko Institute of Mechanics and the
E. O. Paton Institute of Electric Welding. The nondestructive ultrasonic methods are intended to determine triaxial (including
biaxial and uniaxial) stresses in structural members and biaxial (including uniaxial) stresses in near-surface layers of materials 相似文献
19.
Application of X-ray diffraction, micromagnetic and hole drilling methods for residual stress determination in a ball bearing steel ring 总被引:1,自引:0,他引:1
C. O. D. Martins Ph.D. T. R. Strohaecker A. S. Rocha T. K. Hirsch 《Experimental Mechanics》2005,45(4):344-350
A basic understanding of distortion problems requires the analysis of a complete manufacturing process including an almost
complete overview of residual stress states in the component during each production step. To reduce the measurement time in
the future, three measurements methods (X-ray diffraction, micromagnetic and blind hole drilling methods) have been used to
analyze residual stress states in machined AISI 52100 ball bearing rings. X-ray diffraction was used as a state-of-the-art
method for machining induced residual stresses with pronounced gradients. The ring exhibited a complex residual stress state
with high tensile residual stresses at the surface, a strong gradient in depth, and also showed some variation along the outer
circumference due to a superimposition of machining induced residual stresses and effects from the clamping device process.
Due to this surface state, micromagnetic signals depend on the analyzing frequency. A calibration of the signals was only
possible with the X-ray diffraction data. The results of the three different measurement methods correlate reasonably well. 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