Showing papers in "Strain in 1997"
TL;DR: In this paper, a new integral analysis technique in combination with finite element calibration data is introduced to resolve the triaxial residual stress profiles of measurements performed with the hole drilling or ring core method.
Abstract: A new integral analysis technique in combination with finite element calibration data is introduced to resolve the triaxial residual stress profiles of measurements performed with the hole drilling or ring core method. The new technique uses an inverse formulation with symmetrised trigonometric basis functions or wavelets.
15 citations
TL;DR: In this paper, a new analysis technique is introduced to resolve the triaxial residual stress profiles from measurements using the conventional strain gauges for the hole drilling or ring core method extended with a displacement transducer to measure the out of plane displacement.
Abstract: A new analysis technique is introduced to resolve the triaxial residual stress profiles from measurements using the conventional strain gauges for the hole drilling or ring core method extended with a displacement transducer to measure the out of plane displacement. The new technique uses an inverse formulation with wavelets.
14 citations
TL;DR: The use of a commercially available Handycam is shown to meet the requirement of image capturing for digital photoelastic analysis and fringe order variations for three arbitrary lines in a circular disc under diametral compression are obtained and compared with theoretical predictions.
Abstract: An optical arrangement for application of the phaseshifting technique to reflection photoelasticity is presented. The intensity equations for application of phaseshifting methodology are obtained by Jones' calculus. A new portable reflection polariscope is designed to effect the optical arrangement. The use of a commercially available Handycam is shown to meet the requirement of image capturing for digital photoelastic analysis. Fringe order variations for three arbitrary lines in a circular disc under diametral compression are obtained by the new methodology and compared with theoretical predictions. The comparison is found to be good.
12 citations
TL;DR: In this article, the authors present a technique by which it is possible to smooth thermo-elastically measured interior information and to enhance edge data from non-boundary measured values.
Abstract: This paper presents a technique by which it is possible to smooth thermoelastically measured interior information and to enhance edge data from non-boundary measured values. The methodology is based on the compatibility equation and an iterative procedure. The technique has been successfully applied to correctly quantify the stress concentration around a hole in an araldite plate.
5 citations
4 citations
TL;DR: In this paper, a single exposure moire interferometric technique is proposed that maps completely partial curvature contours in three different directions of laterally loaded specularly reflecting plate models.
Abstract: Most known moire methods need to be repeated three times for getting curvature information in three different in plane directions, for the complete analysis. To overcome this difficulty, a new single exposure moire interferometric technique is proposed that maps completely partial curvature contours in three different directions of laterally loaded specularly reflecting plate models. Converging HeNe laser light is diffracted by a lens plane cross grating. The 00, + 10 and the +01 diffraction orders are permitted through the Fourier transform (FT) plane and collimated to illuminate the plate model. The reflected light from the loaded model records the model with the inherent deformed interferometric cross grating superimposed on it. A posteriori Fourier filtering of the developed recording (moiregram) gives partial curvature contours pertaining to three different in plane directions from which the principal curvatures and the principal directions are obtained. Also, this technique, being a single exposure technique, has the potential for complete bending analysis of plates subjected to lateral impact loading and destructive loading applications, where the repeatability of the event may not be possible.
3 citations
TL;DR: A simple PC based device independent software for collection of photoelastic data from digitised fringe patterns is presented and validated by evaluating the near crack tip stress field parameters for a crack subjected to mode I and mode II loadings.
Abstract: The application of digital image processing (DIP) techniques to photoelasticity has greatly simplified data reduction and analysis. The softwares reported so far are hardware dependent and hence not portable. A simple PC based device independent software for collection of photoelastic data from digitised fringe patterns is presented. The software is validated by evaluating the near crack tip stress field parameters for a crack subjected to mode I and mode II loadings.
2 citations
TL;DR: In this article, a photoelastic method was used to determine the contact pressure distribution of a centrally loaded finite free-free beam resting on a partially reinforced (horizontally) elastic halfplane.
Abstract: This paper deals with an experimental study, using the photoelastic method, on the bending analysis of a centrally loaded finite free-free beam resting on a partly reinforced (horizontally) elastic halfplane. In the experimental study the interface between the beam and partly reinforced halfplane has been made both frictionless and fully bonded. An experimental-numerical hybrid method, developed earlier by the authors has been used to determine the contact pressure distribution. The contact pressure distribution thus obtained has been compared with the results obtained using an analytical-numerical procedure in which two different modellings have been used for the reinforced region viz., (i) equivalent orthotropic (composite approach); and (ii) layered system (discrete approach). Results of contact pressure distribution as well as bending stress distribution in the beam have been presented for several cases. The experimental procedure presented here is easy to apply to such complex practical problems and could be of interest to design engineers.
2 citations
2 citations
TL;DR: In this paper, a new method for producing high temperature gratings is put forward, with two deposited metal layers on the specimen, the oxidation resistant ability of this grating was improved and its applications were enlarged, to cover almost all metals.
Abstract: In this paper, a new method for producing high temperature gratings is put forward. With two deposited metal layers on the specimen, the oxidation resistant ability of this grating was improved, and its applications were enlarged, to cover almost all metals. The procedure for producing a grating and the controlling factors of grating quality are discussed in detail.
2 citations
TL;DR: In this paper, the effects of cutouts on the buckling load of pipes were investigated using finite element and experimental techniques, and the results obtained were in reasonably good agreement with those obtained by the semi-empirical solution.
Abstract: In the fabrication of offshore structures, cutouts are often made on pipes to allow access to the interior of the pipes for maintenance and servicing. Thus, there is a necessity to investigate the effects of cutouts on the buckling load of pipes. Both the finite element and experimental techniques have been employed to investigate several series of pipes with and without cutouts. The results obtained were in reasonably good agreement with those obtained by the semiempirical solution.
TL;DR: In this paper, the authors adapted the classical solution to the stress concentration around an elliptical hole in an infinite plate under uniaxial stress by converting the slot into an equivalent thin ellipse of large major:minor axis ratio with its major equal to the length of the slot, and employed the principle of superposition to find the stress state on an axis of symmetry at near and far locations from the notch tip.
Abstract: The stress distributions around a straight blunt slot under biaxial stress are found by adapting the classical solution to the stress concentration around an elliptical hole in an infinite plate under uniaxial stress. Firstly, the slot was converted into an equivalent thin ellipse of large major:minor axis ratio with its major equal to the length of the slot. The principle of superposition was then employed to find the stress state on an axis of symmetry at near and far locations from the notch tip. Stress states were found for any ratio of remotely applied stresses in directions perpendicular and parallel to the notch axis. The solutions were verified experimentally for specific tensile stress ratios by bonding strain gauges to an aluminium plate under hydraulic pressure.
TL;DR: In this paper, the contact stress analysis for a strip footing interacting with a homogeneous orthotropic halfplane and a multilayered orthotropic medium (halfplane) is presented.
Abstract: This paper deals with the contact stress analysis for a strip footing interacting with (i) a homogeneous orthotropic halfplane and (ii) multilayered orthotropic halfplane . The contact stresses have been obtained using a combined approach(finite element method-analytical)in which the stiffness matrix for the footing has been obtained using the finite element method(F.E.M) while for the different cases oforthotropic medium(halfplane) considered here, suitable analytical solutions have been used. The halfplane needs to be discretised only along the contact length. Hence the solution can be obtained with a minimum input data and also the solution scheme is computationally efficient. Results have been presented for the contact stress distribution, displacement profile and bending stress distribution in the footing.
TL;DR: It is shown that some values of the force applied during speaking are of significance in corrective orthodontics, and a tendency was observed for a logarithmic dependence between the loads exerted by perioral muscles on teeth and the acoustic pressure level due to the voice.
Abstract: This paper deals with the “in vivo ” evaluation of the forces exerted by perioral muscles on dental arches and describes the relationship between these loads and the acoustic emission, during speech production. To carry out the research two miniaturised load cells were placed on the upper incisors’ vestibular surface of 12 patients (6 male, 6 female age ranging from 19 to 25 years) to monitor the contact forces generated during the pronunciation of three phonemes containing labio-dental sounds. The acoustic pressure was gathered by means of a capacitive microphone. From the obtained results it is shown that some values of the force applied during speaking are of significance in corrective orthodontics; in fact, the maxima of the recorded values were approximately 2.7N and I .ON for female and mule subjects, respectively. Also a tendency was observed for a logarithmic dependence between the loads exerted by perioral muscles on teeth and the acoustic pressure level due to the voice; in fact, the correlation coeficients R were, for some of the examined patients, >0.9, even if values of 0.4 also were observed.
TL;DR: In this article, a method to measure cyclic strain with no contact using metal foil gauges assisted by the laser speckle method is presented, which is intended to make a non-contacting strain measurement by the application of the laser specckle technique for the detection of the surface change.
Abstract: This paper presents a new method to measure cyclic strain with no contact using metal foil gauges assisted by the laser speckle method. When aluminium foil is pasted on a specimen and the specimen is loaded cyclically, slip bands are produced on the foil surface. There is a fixed relation between density of the slip bands and the strain amplitude or loading cycles depending on the foil material. Thus the fatigue strain of the base metal can be estimated by observing the surface change of the metal foil by the slip bands at a constant number of loading cycles. The method presented in this paper is intended to make a non-contacting strain measurement by the application of the laser speckle technique for the detection of the surface change. This method is based on observation of the changes in a laser speckle pattern depending on the surface roughness and surface property changes of the foil caused by fatigue. The laser speckle pattern can be analysed automatically and quantitatively using an image processing system.
TL;DR: In this paper, a grid method was used to measure the residual deformation of a loaded aluminium plate irradiated by CO 2 laser and the residual strain fields near the illuminated area at different irradiation times were obtained.
Abstract: In this paper, a grid method was used to measure the residual deformation ofa loaded aluminium plate irradiated by CO 2 Laser. The residual strain fields near the illuminated area at different irradiation times were obtained. The experimental results were discussed in detail.