Showing papers in "Strain in 1999"
TL;DR: In this article, the theory of thermoelastic stress analysis is reviewed and the assumptions in developing the theory are assessed, and the equipment for thermo-elastic analysis is based on infra-red detection systems.
Abstract: The theory of thermoelastic stress analysis is reviewed and the assumptions in developing the theory are assessed. The equipment for thermoelastic stress analysis is based on infra-red detection systems. The commercially available systems are described and appraised. Techniques for calibrating the output from the detectors are also provided.
87 citations
TL;DR: A comprehensive review of methods to determine the stress intensity factor at crack tips using thermoelastic stress analysis is given in this article, where a number of areas of experimental procedure need to be considered and these are discussed in detail.
Abstract: A comprehensive review is given of methods to determine the stress intensity factor at crack tips using thermoelastic stress analysis. In order to obtain accurate results a number of areas of experimental procedure need to be considered and these are discussed in detail. The paper concludes with a discussion on the future potential of the use of thermoelasticity for the analysis of cracks.
76 citations
TL;DR: A number of applied thermoelastic stress analysis (TSA) studies on composite components and assemblies are described, for the purpose of illustrating the potential of the technique for use with composite materials as mentioned in this paper.
Abstract: A number of applied thermoelastic stress analysis (TSA) studies on composite components and assemblies are described, for the purpose of illustrating the potential of the technique for use with composite materials.
49 citations
TL;DR: In this paper, a technique is developed for determining the individual principal stresses by measuring experimentally the sum and the difference of the principal stresses over a surface of an engineering component, which is based upon the simultaneous use of thermoelastic stress analysis and automated photoelasticity.
Abstract: A technique is developed for determining the individual principal stresses by measuring experimentally the sum and the difference of the principal stresses over a surface of an engineering component. This application, which results from previous research on the thermoelastic response of polycarbonate coatings typically used in reflection photoelasticity, is based upon the simultaneous use of thermoelastic stress analysis and automated photoelasticity. Full field patterns of the individual principal stresses can be evaluated, even over complex geometric surfaces, by properly processing the data obtained by the independent experimental techniques.
16 citations
TL;DR: Using a monochromatic light source for illumination, a new approach which uses two different loads to get continuous isoclinic fringes is proposed in this article, and a new set of optical arrangements in a plane polariscope setup is proposed for this purpose.
Abstract: Using a monochromatic light source for illumination, a new approach is proposed which uses two different loads to get continuous isoclinic fringes A new set of optical arrangements in a plane polariscope setup is proposed for this purpose The intensity equations are obtained by Jones calculus The methodology is verified for the problem of a disc under diametral compression
14 citations
TL;DR: In this article, the inherent strain distribution along thickness z-direction is evaluated according to the elastic strain releases, assuming that the inherent strains (plastic strains resulting from the welding process) are the initial strains of the finite element method (FEM) analysis for the welded residual stresses, these are used further to evaluate the residual stress distributions along the thickness zdirection in the multi-layer explosive welding joint.
Abstract: In the multi-layer welded joint of titanium-tantalum (Ti-5Ta/ Ti-5Ta/Ta/substrate of stainless steel (SUS304) the second layer of plate Ti-5Ta is 4mm thick, and the third plate Ta is only 1 mm thick It is almost impossible to measure the stresses near the weld with cutting strip technique. Using a successive milling technique the inplane elastic strain releases normal to the thickness direction are measured. With the finite element method (FEM) inherent strain distribution along thickness z-direction is evaluated according to the elastic strain releases. Subsequently, assuming that the inherent strains (plastic strains resulting from the welding process) are the initial strains of the FEM analysis for the welded residual stresses, these are used further to evaluate the residual stress distributions along the thickness z-direction in the multi-layer explosive welding joint.
14 citations
TL;DR: In this paper, the effect of rigid body motion vibration on welding residual stresses was investigated using two different frequencies (50 Hz and 500 Hz), with no particular trend in the reduction of residual stresses in longitudinal or transverse direction.
Abstract: Previous studies suggested that the state of residual stress in a weld may be modified by vibration during and after the welding process. In this study, the effect of rigid body motion vibration on welding residual stresses was investigated. The specimens were welded while they were being vibrated in a rigid body motion mode. The specimens were vibrated using two different frequencies (50 Hz and 500 Hz). At the lower frequency vibration (50 Hz), small changes in the residual stresses were found, with no particular trend. At the high frequency vibration, no significant reductions in the residual stresses were observed in the longitudinal stresses or in the transverse direction. Some initial results are presented also regarding flexural vibration effects.
13 citations
TL;DR: In this paper, a whole field non-contact optical technique has been applied to the study of a dry human mandible under load, with the results viewed in real time as progressively greater forces were applied on the lower border of the chin, in the upwards (impact) direction with biting boundary conditions included in the experimental model.
Abstract: Orthognatic surgeons have a requirement for the measurement of stress distribution within the human lower jaw, in order to aid and improve surgical procedures. Validation of finite element modelling data describing mandible behaviour which has previously been attempted using holographic interferometry. Electronic speckle pattern interferometry (ESPI), a whole field non-contact optical technique has been applied to the study of a dry human mandible under load. This technique improves over previous methods by generating discrete quantitative displacement and strain components. The optical analysis of a dry mandible is described, with the results viewed in ‘real time’ as progressively greater forces were applied on the lower border of the chin, in the upwards (impact) direction with biting boundary conditions included in the experimental model. This has shown that the bone tissue holding the front teeth transmits the forces impacting on the chin, which are absorbed by the basal bone of the mandible.
10 citations
TL;DR: In this paper, the authors used the hole drilling technique applied on stone constructions as this is very common in architectural heritage and allowed both the deduction of the principal stress values and their directions.
Abstract: When structural damage appears in architecture, as in civil engineering, one of the first things to do is to analyse the level of stresses supported by the structural elements of the building. In most of the cases, the deduction of these stresses is carried out by means of one verification of the “design loads”, using analytic methods based (or not) on standardised computer assisted applications. Nowadays, there is not one experimental method close enough to deduce the loads really supported by the structural elements. This article deals precisely about the resolution of this problem by means of the hole drilling technique applied on stone constructions as this is very common in architectural heritage. The particular use of the hole drilling technique in architectural heritage is named Donostia method by the authors, and allows both the deduction of the principal stress values and their directions. This is a very important aspect when the structural damages are generated by anomalous loads.
8 citations
8 citations
TL;DR: In this article, the electron moire method is used to measure the thermal deformation of electronic packages, where a holographic grid was replicated on the cross section of the BGA type package at 150°C.
Abstract: In this paper, electron moire method is used to measure the thermal deformation of electronic packages. In order to observe the electron moire fringe, a holographic grid was replicated on the cross section of the BGA type package at 150°C. This grid was fabricated on a glass plate using a moving point holographic system, and was replicated to measured area at high temperature. Under SEM, the holographic grid(specimen grid) and a programmed electron beam scan(master grid) interfere and form electron moire patterns. The shear strain measurement technique using electron moire method is described. Using the electron moire method, the shear strains in the different solder joints were measured and analysed. Some useful results were obtained.
TL;DR: In this article, the authors describe the work carried out by Rover's Experimental Analysis Department on developing the thermoelastic stress analysis technique for use with rapid prototype models, and discuss the business issues which drove the research into a new "rapid" design validation technique, and detailed work required to ensure the validity of the stress results.
Abstract: This paper describes the work carried out by Rover's Experimental Analysis Department on developing the thermoelastic stress analysis technique for use with rapid prototype models. The paper discusses the business issues, which drove the research into a new “rapid” design validation technique, and the detailed work required to ensure the validity of the stress results.
TL;DR: In this paper, a typical catalogue of virtual photoelastic isochromatic fringes around the hole of a biaxially loaded infinite plate for two problems is presented, one relates to an infinite plate in which the circular hole is drilled first and then the loads are applied.
Abstract: This paper presents a typical catalogue of “virtual” photoelastic isochromatic fringes around the hole of a biaxially loaded infinite plate for two problems. Problem 1 relates to an infinite plate in which the circular hole is drilled first and then the loads are applied. Problem 2 is the residual stress problem in which the hole is drilled after the biaxial load is applied to the infinite plate. Use of this catalogue allows visualisation of the stress distribution around the hole, and a first approximation to the solution of the inverse problem using photoelasticity.
TL;DR: In this article, an inverse problem solution for the case of photoelastic isochromatic fringes around the hole of a biaxially uniformly loaded infinite plate for two problems is presented.
Abstract: This paper presents an inverse problem solution for the case of photoelastic isochromatic fringes around the hole of a biaxially uniformly loaded infinite plate for two problems. Problem 1 relates to an infinite plate in which the circular hole is drilled first and then the loads are applied. Problem 2 is the residual stress problem in which the hole is drilled after the biaxial load is applied to the infinite plate. This “hole method” solution may be used for all cases of biaxial, far field uniform loading conditions.
TL;DR: In this article, the authors proposed two new concepts, i.e., shape errors of the cylindrical surfaces and deflection errors of a bent calibration beam, in accordance with the features of the forces acting on the beam, and the geometric shape and dimensions of the beam in operation, to analyse and classify the various accidental and systematic errors involved.
Abstract: For the appraisal of accuracy of strain gauge factor testing apparatus based on pure bending moment beams, the common means adopted since the 1960s and still in use internationally today are by application of the strain definition to measure directly the strain on the calibration beam surfaces. However, because of the imperfect measuring principle and inadequate resolution and accuracy of instruments available, etc., this problem has not been solved satisfactorily. This paper proposes a unique way by introducing two new concepts, i.e. the shape errors of the cylindrical surfaces and deflection errors of the bent calibration beam, in accordance with the features of the forces acting on the beam, and the geometric shape and dimensions of the beam in operation, to analyse and classify the various accidental and systematic errors involved. Through the two concepts, the task of appraisal of accuracy is simplified as the appraisal of the cylindricality of the cylindrical surfaces of the bent calibration beam and the appraisal of the three main parameters in the strain formula.
TL;DR: In this paper, a rapid method has been developed for calculating the stress distribution along an axis of symmetry in a two-dimensional photoelastic model and an example is given to show that the results are sufficiently accurate for engineerng design purposes.
Abstract: Obtaining the individual stress components at internal points in a two dimensional photoelastic model is time consuming and requires considerable expertise. A rapid method has been developed for calculating the stress distribution along an axis of symmetry. An example is given to show that the results are sufficiently accurate for engineerng design purposes.
TL;DR: In this article, the authors applied the moire interferometry method to study the strain concentration factor of a carbon fiber composites plate with a central hole, and determined the rules of strain concentration factors under different loads.
Abstract: In this paper, using a 1200 lines/mm replicated grating, the moire interferometry method was applied to study the strain concentration factor of a carbon fibre composites plate with a central hole. The rules of strain concentration factors were determined under different loads.
TL;DR: In this article, a method has been developed for precision casting phoroelastic models of tube intersections to the finished shape, and models made in this way have been tested under internal pressure, axial tension and transverse load.
Abstract: A method has been developed for precision casting phoroelastic models of tube intersections to the finished shape. Models made in this way have been tested under internal pressure, axial tension and transverse load. These tests illustrate the difficulty of predicting the location and magnitude of the critical stresses at the intersection.