Application of Moire Methods to the Determination of Transient Stress and Strain Distributions

1962 ◽  
Vol 29 (1) ◽  
pp. 23-29 ◽  
Author(s):  
W. F. Riley ◽  
A. J. Durelli
Keyword(s):  
Strain Distribution ◽  
Stress And Strain ◽  
Two Dimensional ◽  
Distribution Problem ◽  
Principal Stresses ◽  
Transient Stress ◽  
Optical Phenomenon ◽  
Moiré Effect ◽  
Fringe Patterns

When two arrays of lines are superimposed an optical phenomenon known as the moire effect is observed under certain conditions. This moire effect is used by the authors to determine the distribution of transient strains on the surface of two-dimensional bodies. The method can be used to solve completely the strain-distribution problem or it can be used in combination with photoelasticity to separate the principal stresses. The methods used in interpreting the moire fringe patterns and the techniques used to produce the patterns are described in the paper. Two applications are discussed.

Experiments for the Determination of Transient Stress and Strain Distributions in Two-Dimensional Problems

1957 ◽  
Vol 24 (1) ◽  
pp. 69-76
Author(s):  
A. J. Durelli ◽  
W. F. Riley
Keyword(s):  
Wave Propagation ◽  
Modulus Of Elasticity ◽  
Impact Load ◽  
Dynamic Properties ◽  
Circular Disk ◽  
Stress And Strain ◽  
Two Dimensional ◽  
Low Velocity ◽  
Transient Stress ◽  
Fringe Patterns

Abstract The object of this investigation was to develop a method utilizing photoelasticity for determining transient stress and strain distributions in two-dimensional problems. Numerous investigators have approached this problem using the common photoelastic materials which have a relatively high modulus of elasticity and correspondingly high velocity of wave propagation. However, many difficulties were encountered in photographically recording data, and only a few reliable stress patterns were obtained. In order to avoid these difficulties, a material with a low modulus of elasticity and a correspondingly low velocity of wave propagation was developed. As a result the 8-mm. Fastax camera is capable of recording precise fringe patterns. The material used was a member of the epoxy-resin family, modified to give the desired properties. Both its static and dynamic properties were determined as accurately as possible. It was found that the strain-fringe value of the material is approximately constant, but the modulus of elasticity and stress-fringe value are different for static and dynamic loadings. Preliminary studies were conducted to develop the method using a circular disk under a radially applied concentrated impact load as the model. A simply supported beam under central impact was then studied, and deflection curves obtained were compared with curves theoretically predicted by Saint Venant and Flamant. The comparisons showed good agreement. An analysis of the formation of the fringe pattern for various times after impact also was made.

scholarly journals Microscopic Stress and Strain Evolved in a Twinning-Induced Plasticity Fe-Mn-C Steel

2014 ◽  
Vol 996 ◽  
pp. 135-140
Author(s):  
Shigeru Suzuki ◽  
Shigeo Sato ◽  
Koji Hotta ◽  
Eui Pyo Kwon ◽  
Shun Fujieda ◽  
...  
Keyword(s):  
Strain Distribution ◽  
Crystal Orientation ◽  
Fem Simulation ◽  
Tensile Loading ◽  
Stress And Strain ◽  
X Ray Diffraction ◽  
Principal Stresses ◽  
Orientation Data ◽  
Tensile Direction ◽  
X Ray

White X-ray diffraction with micro-beam synchrotron radiation was used to analyze microscopic stress evolved in coarse grains of a twinning-induced plasticity Fe-Mn-C steel under tensile loading. In addition, electron backscatter diffraction (EBSD) was used to determine the crystal orientation of grains in the polycrystalline Fe-Mn-C steel. Based on these orientation data, the stress and strain distribution in the microstructure of the steel under tensile loading was estimated using FEM simulation where the elastic anisotropy or the crystal orientation dependence of the elasticity was taken into account. The FEM simulation showed that the strain distribution in the microstructure depends on the crystal orientation of each grain. The stress analysis by the white X-ray diffraction indicated that the direction of the maximum principal stresses at measured points in the steel under tensile loading are mostly oriented toward the tensile direction. This is qualitatively consistent with the results of by the FEM simulation, although absolute values of the principal stresses may contain the effect of heterogeneous plastic deformation on the stress distribution.

On the determination of the sum of the principal stresses in two-dimensional problems

1966 ◽  
Vol 6 (9) ◽  
pp. 19A-28A ◽  
Author(s):  
A. J. Durelli ◽  
V. J. Parks ◽  
A. Mulzet
Keyword(s):  
Two Dimensional ◽  
Principal Stresses

Comparative two- and three-dimensional finite element modelling techniques for tibial fractures

2001 ◽  
Vol 215 (2) ◽  
pp. 255-258 ◽  
Author(s):  
S Mishra ◽  
T N Gardner
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Stress And Strain ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Principal Stresses ◽  
Two Dimensional Model ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

Often the choice of a two-dimensional modelling approach over a three-dimensional approach is made on the basis of available resources, and not on task appropriateness. In the case of simulating the mechanical behaviour of irregular anatomical structures in biomedical engineering, the authenticity of two-dimensional model behaviour and the interpretation of model solutions is of particular concern since little comparable two-dimensional and three-dimensional data have been published. As part of a research programme, a comparison was made between two-dimensional and three-dimensional finite element models (FEMs) that examine the stress-strain environment of a clinical bone fracture and callus. In comparison with the three-dimensional model, the two-dimensional model substantially underestimated peak compressive principal stresses in the callus tissue and peak equivalent strains. This was a consequence of geometrical and structural asymmetry in a plane perpendicular to the two-dimensional model. However, the two-dimensional model predicted similar patterns of stress and strain distribution to the corresponding mid-longitudinal plane of the three-dimensional model, and underestimates of peak stress and strain were much reduced. This confirmed that despite the irregular geometry and structure of the subject, the two-dimensional model provided a valid mechanical simulation in the plane of the fracture that it represented.

Effect of Corner Shape on Elastic Stress and Strain Concentration in Plates With an Oblique Hole

1973 ◽  
Vol 95 (1) ◽  
pp. 151-157 ◽  
Author(s):  
F. Ellyin ◽  
U. M. Izmiroglu
Keyword(s):  
Strain Distribution ◽  
Elastic Stress ◽  
Steel Plates ◽  
Stress And Strain ◽  
Plate Model ◽  
Strain Concentration ◽  
Controlling Variables ◽  
Stress And Strain Distribution ◽  
Insight Into

The effect of the corner cut on the elastic stress and strain concentration in plates containing an oblique hole is studied. Fourteen steel plates with different corner break configurations and varying angles of inclinations are tested. This study has resulted in the determination of the effective range of the controlling variables for a “radius tip” or a “vertical cut”. An investigation of this nature is of interest in the design of oblique nozzle connections in pressure vessel heads and shells. It provides an insight into the nature of stresses in skewed holes and nozzle attachments. Previous works [3, 8] have shown the applicability of the plate model to the oblique nozzle connection, and present study fills the gap with regards to the effect of acute corner cut on the stress and strain distribution.

Photoelastic Separation of Principal Stresses by Oblique Incidence

1943 ◽  
Vol 10 (3) ◽  
pp. A156-A160
Author(s):  
D. C. Drucker
Keyword(s):  
Oblique Incidence ◽  
Three Dimensional ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Fringe Order ◽  
Principal Stresses ◽  
Significant Magnitude ◽  
Oblique Position ◽  
Theoretical Evidence

Abstract Rotation of a two-dimensional model about an axis in its plane is suggested as a simple and quite rapid means of obtaining p and q separately. A determination of retardation (fringe order) in an oblique position is all that is required in addition to the usual photoelastic measurements. Experimental and theoretical evidence is presented to show that accurate results can easily be obtained when the principal stress is of significant magnitude. The method can also be applied in three-dimensional studies.

Elastoplastic Stress and Strain Distribution in a Finite Plate With a Circular Hole Subjected to Unidimensional Load

1963 ◽  
Vol 30 (1) ◽  
pp. 115-121 ◽  
Author(s):  
A. J. Durelli ◽  
C. A. Sciammarella
Keyword(s):  
Experimental Determination ◽  
Circular Hole ◽  
Strain Distribution ◽  
Stress And Strain ◽  
Hardening Material ◽  
Finite Plate ◽  
Elastoplastic Stress ◽  
Moire Method ◽  
Stress And Strain Distribution

This paper deals with the experimental determination of the elastoplastic stress and strain distribution around an empty circular hole in a finite aluminum plate subjected to a unidimensional load as the deformation increases from the elastic far into the plastic field. The strains were measured using the moire method. The stresses were computed by means of the Prandtl-Reuss stress-strain relationships presented in a convenient form for the case of a strain-hardening material.

Calculation of Elastic Displacements From Photoelastic Curves

1953 ◽  
Vol 20 (3) ◽  
pp. 375-380
Author(s):  
H. Poritsky ◽  
R. P. Jerrard
Keyword(s):  
Principal Stress ◽  
Beam Theory ◽  
Dimensional Case ◽  
Stress Difference ◽  
Two Dimensional ◽  
Principal Stresses ◽  
Fringe Patterns

Abstract A method of utilizing photoelastic fringe patterns for purposes of calculating elastic displacements of stressed members is developed. This method utilizes only the lines of constant principal stress difference and does not require knowledge of the directions of the principal stresses. The method developed should prove useful in many cases where measurements of elastic displacements cannot be carried out conveniently but photoelastic fringe patterns are readily available. As an example, the two-dimensional case of a beam in bending with a change in thickness is treated. The correction that must be applied to simple beam theory is determined.

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