3D Photoelasticity Research Articles

Quantification of full-field stress in continuously loaded fractured rocks using 3D printing and digital photoelasticity

Accurately characterizing stress fields in fractured rocks is crucial for understanding fracture propagation and rock failure mechanisms. However, existing methods struggle to quantify stress fields in continuously loaded fractured rocks with complex fracture networks. In this study, we propose a novel method that utilizes 3D printing and digital photoelasticity to quantify full-field stress in complex fractured rocks under continuous loading. Our method incorporates three key components: a modified global fringe thinning technique for automatic extraction of fringe skeletons, a proposed algorithm for automatic identification of near-zero-order fringe regions, and an optimized phase calculation process for efficient phase unwrapping. The effectiveness and accuracy of our method are validated through theoretical analysis and comparison with results obtained from the ten-step phase shifting method. Furthermore, our proposed method can also be applied to quantify stress fields in fractured rocks under static loading.

Photo-Elastic Investigation of Worm Gear

Worm & worm wheel is used in the gearbox of the hoisting machine. The worm wheel failed during its operational state and a crack was perceived in the central breadth of the gear tooth. This failure persisted with worm & worm wheels produced in a particular lot. This paper aims to analyze this worm wheel using theoretical analysis, the experimental stress analysis technique, and simulation. Lewis Equation is employed to perform the numerical analysis, the experimental analysis is conducted using 3D photo-elasticity technique and simulation is performed in ANSYS software. The results obtained from each analysis are equated to accomplish the investigation.

Masticatory System Biomechanical Photoelastic Simulation fot the Comparision of the Conventional and Uni-Lock Systems in Mandibular Osteosynthesis

The biomechanical consequences of the interaction between titanium trauma plates and screws and the fractured mandible are still a matter of investigation. The mathematical and biomechanical models that have been developed show limitations and the experimental studies are not able to reproduce muscle forces and internal stress distributions in the bone-implant interface and mandibular structure. In the present article we show a static simulator of the masticatory system to demonstrate in epoxy resin mandibular models, by means of 3D (three-dimensional) photoelasticity, the stress distribution using different osteosynthesis methods in the mandibular angle fractures. The results showed that the simulator and 3D photoelasticity were a useful method to study interactions between bone and osteosynthesis materials. The “Lock” systems can be considered the most favourable method due to their stress distribution in the epoxy resin mandible. 3D photoelasticity in epoxy resin models is a useful method to evaluate stress distribution for biomechanical studies. Regarding to mandibular osteosynthesis, “lock” plates offer the most favourable stress distribution due to being less aggressive to the bone

A CAE approach for the stress analysis of gear models by 3D digital photoelasticity

The use of numerical and experimental methods to determine the stress field of mechanical components is well known. In particular, 3D photoelasticity can be considered the only experimental technique for the complete stress state evaluation of 3D components. The advent of rapid prototyping techniques has allowed the manufacturing of complex models in a matter of hours by using birifrangent materials. The present paper is focused on the description of a Computer Aided Engineering (CAE) approach which combines Finite Element (FE) simulations and automatic photoelastic investigations for the stress analysis of face gear drives, made by stereolithography. Computer Aided Design (CAD) geometries, used to manufacture the stereolithographic models, are directly used to perform FE analyses, thus allowing the stress analysis process to become simpler and easier. The substantial agreement observed between experimental and numerical results proved the potentialities of the adopted approach and the usefulness of FE simulations to optimize photoelastic analyses through cost- and time-effective experiments even for complex 3D shapes.

Comparación biomecánica entre los sistemas convencionales y uni-lock en osteosíntesis del ángulo mandibular. Estudio fotoelástico

IntroductionThe biomechanical effects of the interaction between titanium plates and screws and the fractured mandible are not well known. The mathematical models that have been developed to date show limitations and the experimental studies fail in reproducing muscle forces and internal stress distributions in the bone-implant interface with the mandibular structure. Material and methodsIn the present study we use a static simulator of the masticatory system to show, in epoxy resin mandibular models, by means of 3D (three-dimensional) photoelasticity, the stress distribution using different osteosynthesis methods in mandibular body fractures. ResultsThe results showed that the simulator and 3D photoelasticity were useful for studying interactions between bone and osteosynthesis materials. The “Lock” system displayed the most favourable stress distribution in the epoxy resin mandible. Conclusions3D photoelasticity in epoxy resin models is a useful method to evaluate stress distribution for biomechanical studies. In terms of mandibular osteosynthesis, “lock” plates show the most favourable stress distribution due to being less aggressive to the bone.

Experimental validation of a numerical simulation on a ballscrew system by 3D photoelasticity

The Trimmable Horizontal Stabilizer Actuator (THSA system) equips the whole airbus line. One component of this system is a ball-screw system on which spalling problems appear on the balls. This phenome non is mostly due to local high pressures and reduces the service life of the syste m. 3D numerical simulations are usually used to tackle this kind of problems but ar e subjected to assumptions. As the aim of the project is to build a numerical model able t o predict pressure distribution, these assumptions need to be experimentally assessed to b e perfectly relevant of the real load distribution in the ball screw system. Due to the 3 D geometry of the specimen, a 3D measurement technique, Scattered Light Photoelasticity (SLP), has been chosen to perform experimental measurements,. Because of complexity of the geometry, the study is divided in three steps; the present paper is dea ling with the second one where a demonstrator ball-screw system is manufactured in c asted epoxy to perform the SLP. This technique gives information on 3D stress field s inside the epoxy specimen from the analysis of photoelastic fringes. They are compared to numerical ones and indicate whether numerical boundary conditions are relevant of the experimental ball-screw system behaviour.

Stress field tomography based on 3D photoelasticity

A tomographic method for identification of stress fields based on 3D photoelasticity has been developed. A second order tensor field tomographic method based on the general inverse problem of 3D photoelasticity, previously developed by the authors, is found to be highly sensitive to errors in photoelastic observations. In this study a new tomographic method for stress field with fairly high robustness to errors in photoelastic observations has been developed by introducing both equilibrium condition and linear elasticity to the previously developed general tensor field tomographic method. This new stress field tomographic method expands unknown 3D stress distributions as a linear combination of independent set of basis functions and a new inverse problem is posed: identify the amplitudes of basis functions based on photoelastic observations. Just as the inverse problem of 3D photoelasticity, this newly posed inverse problem is also nonlinear and ill posed. Unlike conventional approaches to 3D photoelasticity, both these nonlinearity and ill-posedness are properly treated using a load incremental approach. Load incremental approach chops the nonlinear solution space into segments with unique solutions by conducting photoelastic observations at sufficiently small increments in external load. Validating both numerically and experimentally, it is shown that this new stress field tomographic method has sufficient robustness against errors in photoelastic observations and is applicable to experimental stress measurements.

Crystal Optical Properties of Inhomogeneous Plates and the Problems of Polarization Tomography of Photoelastic Materials

Abstract Using the Jones matrix formalism, crystal optical properties of inhomogeneous material consisting of a pile of weakly birefringent plates are analysed in relation to the cell model adopted in polarization tomography of 3D dielectric tensor field in photoelastic media. It is shown that the material manifests in general an “apparent” optical gyration caused by different orientations of the plates. Relations between the polarimetric parameters and the dielectric tensor components are ascertained for the case of weak optical anisotropy. Key words : photoelasticity, 3D tensor field tomography, birefringence, gyration, Jones matrices. PACS: 07.60.Fs, 42.25.Lc, 42.30.Wb Introduction Photoelasticity has been remaining one of extensively explored topics within the physical optics during the last decades (see, e.g., [1-4]). Its problems become enormously complicated if external (or internal) mechanical stresses are arbitrarily and inhomogeneously distributed inside a sample under test, thus transforming initially isotropic, macroscopically uniform material into anisotropic and homogeneous one. This field is often referred to as a 3D photoelasticity. In case of weakly anisotropic, weakly inhomogeneous materials possessing none or slight absorption, the stressed state manifests itself mainly in a notable effect on the polarization of probing light wave. Then the 3D spatial distribution of stresses (or, equivalently, that of dielectric parameters at the optical frequencies) might be clarified, using the methods of polarization optical tomography of 3D tensor fields (see [1,3]). In spite of essential current progress, those methods have not yet succeeded in solving the problem in its most general form. Considerable analytical difficulties of the tensor field tomography have stipulated a number of approximate approaches, e.g., a “discretely inhomogeneous” (or “cell”) model of the stressed material (see [2,5]), in which the sample is divided into many identical uniform cells. For a given propagation direction, the light beam probes a pile of anisotropic cells characterised by different parameters. This situation reminds a canonical problem of crystal optics, propagation of light through the so-called composite retardation plates [6,7]. Hence, elaboration of the latter would contribute to a better understanding of principles, techniques Ukr. J. Phys. Opt. 2005, V6, №3 87

Boundary Condition Identification Based on 3D Photoelasticity

Boundary Condition Identification Based on 3D Photoelasticity

Tensor field tomography based on 3D photoelasticity

A new method for non-destructive measurement of arbitrary 3D stress state using photoelasticity has been developed. The new approach, namely, load incremental approach, is an attempt to solve the non-linear inverse problem of 3D photoelasticity by considering change in stress state for a load increment and linearizing the non-linear governing equation. As long as the applied load increment is small and photoelastic images are taken with high resolution in load increment, this method works and can reconstruct arbitrary 3D stress state. Numerical simulations clarify the effect of (i) the material sensitivity, (ii) the number of the observations and (iii) the constraint on the observation directions on the performance of the proposed method. These results provide the fundamental data for designing the experimental setup for 3D photoelasticity.

Digital Photoelasticity: Advanced Techniques and Applications

Digital Photoelasticity: Advanced Techniques and Applications

光弾性を用いた三次元応力場計測のための逆解析手法の開発

A new method for non-destructive measurement of arbitrary 3D stress state using photoelasticity has been developed. The new approach proposed here, namely, load incremental approach, is an attempt to solve the nonlinear inverse problem of 3D photoelasticity by the linearization of the governing equation based on high resolution in load increment. As long as the applied load increment is small enough, this method works and can reconstruct arbitrary 3D stress state.Results from numerical simulations show the effect of i) the number of the observations, ii) the independency of the observation directions, and iii) the material sensitivity on the performance of the proposed method.