Stresses in square slabs,with different edge geometries,when bonded on one face to a rigid plate and shrunk

An approximately square epoxy slab (≈14 in. ×≈14 in. ×1 in.) with four different edge geometries was bonded to a rigid plate on one of its faces. In the process of “freezing” photoelastic effects, a state of restrained shrinkage developed. Slices removed from the slab were used to determine the concentration factors corresponding to the four geometries.     

A shadow-moiré method with continuously variable sensitivity

This paper presents a shadow moiré method whereby the isostathmics (contours of surface depth) can be studied with continuously variable sensitivity. In the method the sensitivity is varied by simply rotating the grating in front of the object surface. Equations interpreting the isostathmics are derived, and an experimental demonstration is included.     

Identification of isochromatic fringes

In simple cases of static-photoelastic analysis, the numbering of the isochromatic fringes does not present unusual difficulties. In more complex cases, in particular wave propagation, the problem may be so difficult that few investigators attempt the analysis. In this paper guidelines to number the isochromatic fringes are presented. Advantage is taken of some topological properties as well as of the time and space derivatives of these isochromatic fringes. Several examples are discussed to illustrate the use of the guidelines. It is observed that under most conditions the guidelines are sufficient to number the whole field of isochromatics on photographs taken with the commonly used monochromatic light.     

Temperature and time influence in the stress freezing of the epoxy Hysol 4290

Disks of the photoelastic epoxy known as Hysol 4290 have been subjected to constant load at various temperature levels and the birefringence has been recorded as time elapsed (creep test). Also disks of the same material were loaded at the critical temperature and then cooled, each to a different temperature level and, after they reached thermal equilibrium, the loading was removed while the temperature was maintained constant (recovery test). The effect of time on the fringe value is given for both groups of tests using the temperature as a parameter. Finally, tensile specimens have been subjected to various loads at the critical temperature and fringe response and failure recorded. The results obtained may be useful for the design of experiments and, in some cases, to shorten the time required to conduct a three-dimensional photoelasticity investigation using the “freezing” method.     

Constant-acceleration stresses in a composite body

This paper is a contribution to the experimental stress analysis of composite structures subjected to gravitational forces. It is proved, generally, that the immersion analogy can be used to analyze these stresses in composite bodies provided all the materials of such bodies have the same weight per unit volume. Applications are described in two-dimensional problems immersing urethane-rubber models bonded to epoxy shells in a thallium-formate solution. Photoelasticity is used to determine stresses. The method increases the response obtained and will have application in the solution of problems where constant-acceleration stresses are important, as in dams and solid-propellant rocket grains.     

Experimental stress analysis of loaded boundries in two-dimensional second-boundary value problems

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.     

Numerical continuation of degenerate homoclinic orbits in planar systems

In this paper we develop numerical algorithms for the continuationof degenerate homoclinic connections in planar systems. We considerthe case where the equilibrium point has zero trace and twocases of higher-order degeneracies. The method we propose isable to continue homoclinic connections of order up to codimension-four.Application of the algorithm to four examples supports its validityand demonstrates its usefulness.     

Gas-phase deprotonation of arylalkylamines. A collision-induced dissociation study

The collision-induced dissociation (CID) of deprotonated arylalkylamines of general formula R(1)C(6)H(4)CHR(2)CH(2)NR(3)(2) (where R(1) = H, OH, F or NO(2); R(2) = H or OH; R(3) = H or CH(3)) generated by negative chemical ionization with H(2)O and D(2)O as ionizing reagents, is discussed. The negative chemical ionization mass spectra show that, in the absence of a hydroxy group in the aromatic ring, deprotonation takes place at the benzylic position whereas the proton is lost from the OH group when present. The nitro compound forms only M(-.) ions. The CID spectra of the deprotonated molecules show that fragmentations are strongly dependent on the structural features of the molecules, namely the presence or absence of substituents in the aromatic ring or aliphatic chain. Copyright 1999 John Wiley & Sons, Ltd.