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Showing papers in "Journal of Strain Analysis for Engineering Design in 2009"


Journal ArticleDOI
TL;DR: In this article, a method for obtaining good images of sample surfaces at high temperatures, suitable for strain measurement, by digital image correlation (DIC) without the use of surface markers or speckles is presented.
Abstract: A method is presented for obtaining good images of sample surfaces at high temperatures, suitable for strain measurement, by digital image correlation (DIC) without the use of surface markers or speckles. This is accomplished by suppressing black-body radiation through the use of filters and blue illumination. Using only relatively low levels of illumination the method is demonstrated to be capable of providing accurate DIC measurements up to 1100 °C, and the potential to monitor strains to 1400 °C is identified. The capability of the method is demonstrated by measuring the Young's modulus and coefficient of thermal expansion of a nickel-base superalloy at temperatures from ambient to 1000 °C; two parameters that are well established in the literature and that require high strain sensitivity for their reliable determination.

215 citations


Journal ArticleDOI
TL;DR: In this article, a finite element model was used to optimize the material properties to obtain the best match with the model data, and the results were obtained using a Hager-Zhang non-linear conjugate gradient solver.
Abstract: The mechanical properties of the skin are important in many applications, but are not well understood. This paper presents a method for measuring the mechanical properties of human skin in vivo using digital image correlation, with a finite element model that was used to optimize the material properties to obtain the best match with the model data. The skin was modelled as an Ogden hyperelastic membrane, with a tension field wrinkling model and an initial stretch identified as an additional material parameter, and the boundary conditions were the measured load and the displacements around the edge of the region of interest. Fast, reliable convergence was obtained using a Hager–Zhang non-linear conjugate gradient solver. A stochastic optimization procedure was used to identify the material parameters. Good estimates of the material parameters could be obtained from the displacement field at a single time point. Typical material parameters were μ = 10 Pa, α = 26, and an initial strain of 0.2. These parameters were not unique; the stochastic optimization procedure gave good global convergence and an indication of the overall uncertainty in the identification of the results. It is argued that the use of the DIC technique, which generates very large amounts of data, also gave a clearer picture of the overall uncertainty.

138 citations


Journal ArticleDOI
TL;DR: In this article, the residual stresses in Selective Laser Milling (SLM) specimens manufactured from AISI Marage 300 steel were investigated using the strain gauge hole drilling method.
Abstract: Selective laser melting (SLM) is one of the most interesting technologies used in rapid prototyping processes because of the possibility of building complex three-dimensional metal parts of nearly full density and with mechanical properties similar to those obtained with conventional manufacturing processes. This goal can be achieved using high-power lasers and low values of scan velocity. These conditions, together with an appropriate scanning strategy, allow full melting of the powders used in the process to be obtained.The aim of this paper is to investigate the residual stresses in SLM specimens manufactured from AISI Marage 300 steel. First, the strain gauge hole drilling method is utilized to determine residual stress profiles in a set of test samples of different thicknesses, placed in different positions on the building platform. Statistical analyses are performed in order to study the relationships between sample position on the platform, the distance from the specimen surface, and maximum/minimu...

110 citations


Journal ArticleDOI
TL;DR: In this article, the effect of temperature on the voltage output of the nanotube film under no load condition is investigated, and it is evident that MWCNT films exhibit a stable and predictable voltage response as...
Abstract: The effectiveness of multiwalled carbon nanotubes (MWCNTs) as strain sensors is investigated. The key contribution of this paper is the study of real-time strain response at the macroscale of MWCNT film under tensile load. In addition, real-time voltage change as a function of temperature is examined. MWCNT films attached to a brass specimen by epoxy using vacuum bonding have been studied. The brass specimen is subjected to tensile loading, and voltage output from the MWCNT film is obtained using a four-point probe and a sensitive voltage measurement device. Experimental results show that there is a linear change in voltage across the film when subjected to tension, and the MWCNT film both fully recovers its unstressed state upon unloading and exhibits stable electromechanical properties. The effect of temperature on the voltage output of the nanotube film under no load condition is investigated. From the results obtained it is evident that MWCNT films exhibit a stable and predictable voltage response as ...

93 citations


Journal ArticleDOI
TL;DR: In this paper, the authors deal with online controlled propagation and vibration-based detection of fatigue cracks in metal beams constituted of two different materials: 6082-T651 aluminium alloy and Fe430 steel.
Abstract: This paper deals with online controlled propagation and vibration-based detection of fatigue cracks in metal beams constituted of two different materials: 6082-T651 aluminium alloy and Fe430 steel....

78 citations


Journal ArticleDOI
TL;DR: In this paper, a methodology for predicting the residual stress within three-dimensional parts caused by laser peening treatment is presented, where the inputs to the model are the elastic material properties an...
Abstract: This paper presents a methodology for predicting the residual stress within three-dimensional parts caused by laser peening treatment. The inputs to the model are the elastic material properties an...

70 citations


Journal ArticleDOI
TL;DR: In this paper, the authors propose a residual stress-admissible (RSadmissible) field, which is a divergence-free stress field that satisfies stress equilibrium conditions everywhere in the object to the greatest possible level of detail.
Abstract: Experimental stress evaluation procedures often rely on the measurement of some component(s) of elastic strain followed by point-wise calculation of stress based on continuum elasticity assumptions. Such point-wise assessments are, however, incomplete and not entirely satisfactory, as calculations conducted for different points can easily give rise to values that may not satisfy requirements of global force balance. The real purpose of experimental data interpretation is in fact to obtain a reasonably internally consistent description of the state of stress everywhere in the object to the greatest possible level of detail. What is usually being sought is a residual-stress-admissible (RS-admissible) field, i.e. such that would satisfy boundary conditions imposed both in terms of tractions and displacements, and would correspond to a divergence-free stress field (i.e. such that satisfies stress equilibrium conditions everywhere). Note, however, that elastic strains are no longer required to be compatible. T...

65 citations


Journal ArticleDOI
TL;DR: In this article, a ring-type small-specimen creep test method was proposed to obtain accurate creep strain data, which can be used to estimate the creep strain of small specimens.
Abstract: This paper describes a novel, high-sensitivity, ring-type of small specimen creep test method, which can be used to obtain accurate creep strain data. A full theoretical description of the test tec...

58 citations


Journal ArticleDOI
TL;DR: In this paper, the authors presented an analytical framework, built upon the combined utilization of membrane analysis and ductile damage mechanics, that is capable of modelling the fundamentals of single-point incremental forming (SPIF) of metallic sheets.
Abstract: In a previously published work, the current authors presented an analytical framework, built upon the combined utilization of membrane analysis and ductile damage mechanics, that is capable of modelling the fundamentals of single-point incremental forming (SPIF) of metallic sheets. The analytical framework accounts for the influence of major process parameters and their mutual interaction to be studied both qualitatively and quantitatively. It enables the conclusion to be drawn that the probable mode of material failure in SPIF is consistent with stretching, rather than shearing being the governing mode of deformation. The study of the morphology of the cracks combined with the experimentally observed suppression of neck formation enabled the authors to conclude that traditional forming limit curves are inapplicable for describing failure. Instead, fracture forming limit curves should be employed to evaluate the overall formability of the process.The aim of this paper is twofold: (a) to compare the mechan...

57 citations


Journal ArticleDOI
TL;DR: In this article, the effects of the L/D ratio (length L divided by diameter D) along with specimen shape (cylindrical versus square prismatic) on split Hopkinson pressure bar (SHPB) testing were investigated.
Abstract: The results from an experimental and computational study on the effects of specimen size and shape on split Hopkinson pressure bar (SHPB) testing are presented. The effects of the L/D ratio (length L divided by diameter D) along with specimen shape (cylindrical versus square prismatic) were investigated. Even though specimens having a circular cylindrical cross-section are traditionally used in SHPB testing, a square cross-section specimen has advantages associated with in situ imaging of the specimen side surfaces during stress wave propagation. The results presented here show a strong correlation in specimen response between the two types of specimens. Different ranges of L/D ratios are recommended for obtaining stiffness and strength data at near constant strain rates.

52 citations


Journal ArticleDOI
TL;DR: In this article, the authors present the production of strain measurements on porous concrete samples for use in triaxial compression and extension tests with a very high lateral confining pressure, where the porous characteristic of the material together with the high confine pressure require both developing a material protection device and building strain gauge-based instrumentation of unprecedented design for such confining pressures.
Abstract: This article presents the production of strain measurements on porous concrete samples for use in triaxial compression and extension tests with a very high lateral confining pressure. When a massive concrete structure is subjected to severe loadings (e.g. rock falls, near-field detonations, and ballistic impacts), the material undergoes triaxial loading at a high confining pressure. To reproduce high levels of stress with well-controlled loading paths, static tests are carried out on concrete using a high-capacity triaxial press, called GIGA. This press allows the testing of concrete specimens (7 cm in diameter and 14 or 15.5 cm long) for levels of confining pressure ranging up to 850 MPa and axial stresses of up to 2.35 GPa. The porous characteristic of the material together with the high confining pressure require both developing a material protection device and building strain gauge-based instrumentation of unprecedented design for such confining pressures. In addition, the effect of pressure and other...

Journal ArticleDOI
TL;DR: In this paper, a generalized spatial-gradient-based digital image correlation (DIC) method was proposed for subpixel-accuracy displacement and shape measurement, which overcomes the limitations in ex...
Abstract: A generalized spatial-gradient-based digital image correlation (DIC) method is proposed for subpixel-accuracy displacement and shape measurement. The proposed method overcomes the limitations in ex...

Journal ArticleDOI
TL;DR: In this paper, the crack-tip displacement field has been determined at 14 points within each cycle, despite noise in the inferred displacement fields, by least squares fitting the displacement field rather than the strain field to the Muskhelishvili's form crack-point stress field, the cracktip stress intensity inferred from the measured crack- tip displacement field was found to good accuracy (around 0.2 MPa m(1/2).
Abstract: Digital images Of fatigue crack behaviour have been acquired in real time at high cycle fatigue rates (77Hz) using a high-speed camera at 1000 frames/s. Digital image correlation has then been used to determine the crack-tip position and stress intensity variations (K-I and K-II) within selected cycles. This has been achieved for a pre-cracked aluminium compact tension (CT) specimen subjected to constant load amplitude fatigue crack cycling. The crack-tip displacement field has been determined at 14 points within each cycle. In this proof of concept study, despite noise in the inferred displacement fields, by least squares fitting the displacement field rather than the strain field to the Muskhelishvili's form crack-tip stress field, the crack-tip stress intensity inferred from the measured crack-tip displacement field was found to good accuracy (around 0.2 MPa m(1/2)). Furthermore, the observed sinusoidal variation was in excellent agreement with the nominal Delta K obtained from the applied fatigue amplitude confirming the accuracy of the method; a drift of around 0.42 MPa m(1/2) was observed in K-mean from cycle to cycle. No evidence Of Closure was observed at low K. In principle this method permits the identification of crack-tip Closure and crack growth, as well as the application of constant Delta K-eff cycling, through intermittent monitoring throughout the duration of a fatigue test. The current method is well suited to more complex cases where crack closure, residual stresses, or more complex geometries mean that it is difficult to predict Delta K-eff a priori and a number of potential applications of the method are identified.

Journal ArticleDOI
TL;DR: In this article, an element-free mesh-free Galerkin method using radial basis interpolation functions was developed to evaluate static and dynamic mixed-mode stress intensity factors, and the so-called enriched radial basis functions were introduced to capture accurately the singularity of stress at crack tip.
Abstract: Based on the variational principle of the potential energy, the element-free Galerkin method is developed using radial basis interpolation functions to evaluate static and dynamic mixed-mode stress intensity factors. For dynamic problems, the Laplace transform technique is used to transform the time domain problem to the frequency domain. The so-called enriched radial basis functions are introduced to capture accurately the singularity of stress at crack tip. In this approach, connectivity of the mesh in the domain or integrations with fundamental or particular solutions are not required. The accuracy and convergence of the mesh-free Galerkin method with enriched radial basis functions for the two-dimensional static and dynamic fracture mechanics are demonstrated through several benchmark examples. Comparisons have been made with benchmarks and solutions obtained by the boundary element method.

Journal ArticleDOI
TL;DR: A novel method of analysing the resulting images is presented, to provide an overview of the strain environment throughout the tendon sample, which highlighted widely variable strains within the matrix during stress relaxation, with strains far greater than those applied to the sample.
Abstract: Tendon is a multilevel fibre composite material, which generates complex variable local strains in response to gross loading. The tendon cells are located in long rows between collagen fibres, where they respond to the local strain environment with the initiation of mechanotransduction pathways, to control matrix maintenance and remodelling. Knowledge of the local strain environment is thus an important component in understanding tenocyte mechanotransduction. Confocal microscopy has previously been utilized to visualize the tendon matrix during loading, to investigate local strains. Using the cells as strain markers, their response during quasi-static loading or stress relaxation can be monitored. This study presents a novel method of analysing the resulting images, to provide an overview of the strain environment throughout the tendon sample. The cell markers are used as nodes in a mesh of triangular elements and the mathematical approach adopted in the finite element method is used to find the strain di...

Journal ArticleDOI
TL;DR: A computational model for the evolution of a saccular cerebral aneurysm of the internal carotid artery is developed and provides the foundations for the development of more sophisticated models of cerebral anuerysm evolution.
Abstract: A computational model for the evolution of a saccular cerebral aneurysm of the internal carotid artery is developed. The artery is modelled as a two-layered non-linear elastic cylindrical membrane using a physiologically realistic constitutive model. It is subject to a constant systolic pressure and a physiological axial prestretch. The development of the aneurysm is assumed to be a consequence of the growth and remodelling of its material constituents. The elastinous constituents are prescribed to degrade in a localized circular patch. Microstructural recruitment and fibre concentration variables for the collagen fibres enable the growth and remodelling of collagen fabric to be simulated. The model predicts realistic saccular aneurysm geometries that stabilize in size. It provides the foundations for the development of more sophisticated models of cerebral aneurysm evolution.

Journal ArticleDOI
TL;DR: In this paper, a worn British railway rail using neutron diffraction was used to quantify the residual stresses that evolve under repeated rolling contact between wheel and rail, showing the asymmetry and complexity of distributions that arise from the non-uniform plastic deformation.
Abstract: Accumulation of residual stresses in rails during service can contribute to crack initiation and fracture and may result in serious accidents. It is therefore necessary and important to quantify the residual stresses that evolve under repeated rolling contact between wheel and rail. In the present study, triaxial residual strain measurements were performed in a worn British railway rail using neutron diffraction. Localized stress is observed close to the region of contact, showing the asymmetry and complexity of distributions that arise from the non-uniform plastic deformation. Contact-induced plasticity is revealed by the broadening (increase in the full width at half-maximum (FWHM)) of the diffraction peaks.

Journal ArticleDOI
TL;DR: This paper demonstrates that combining regression trees with the finite element method (FEM) may be a good strategy for modelling highly non-linear mechanical systems.
Abstract: This paper demonstrates that combining regression trees with the finite element method (FEM) may be a good strategy for modelling highly non-linear mechanical systems. Regression trees make it possible to model FEM-based non-linear maps for fields of stresses, velocities, temperatures, etc., more simply and effectively than other techniques more widely used at present, such as artificial neural networks (ANNs), support vector machines (SVMs), regression techniques, etc. These techniques, taken from Machine Learning, divide the instance space and generate trees formed by submodels, each adjusted to one of the data groups obtained from that division. This local adjustment allows good models to be developed when the data are very heterogeneous, the density is very irregular, and the number of examples is limited. As a practical example, the results obtained by applying these techniques to the analysis of a vehicle axle, which includes a preloaded bearing and a wheel, with multiple contacts between components...

Journal ArticleDOI
TL;DR: In this article, a model based on a simplification of the non-linear kinematic and isotropic hardening model of Chaboche and Lemaitre is presented.
Abstract: A previously published model for plasticity assessment in rolling contact, based on a simplification of the non- linear kinematic and isotropic hardening model of Chaboche and Lemaitre, is discusse...

Journal ArticleDOI
TL;DR: In this article, a general analytical strategy is presented to study not only these processes, but also to formulate in such a way that it may also be extended to other thermomechanical processes.
Abstract: This paper dwells on the nature of the highly non-linear interactions occurring during heat treatments with the aim of developing an improved understanding of the process and of the residual strains and stresses formed in heat-treated components during processing. As an example, two industrial quench processes are analysed. A general analytical strategy is presented to study not only these processes, but is formulated in such a way that it may also be extended to other thermomechanical processes. This strategy may therefore serve as a roadmap for industrial designers to analyse thermomechanical processes for optimization. Results in the broad framework of thermomechanical processing indicate that careful characterization and correct representation of the heat transfer conditions leads to significant improvements in accuracy over the current quench modelling techniques. In addition to this, the nature of the thermomechanics involved in spray and bath quench processes is analysed. Neutron diffraction experi...

Journal ArticleDOI
TL;DR: In this article, the shape of the redesigned geometry of the specimen was analyzed using the finite element (FEQUS) program ABAQUS to minimize undesired stress concentrations at the die radius.
Abstract: Development of a new sheet-metal-forming technology in a digital environment demands accurate and reliable mechanical properties and forming limits of the selected material. It is essential to determine the forming limits for thin sheets and foils. Implementation of the Marciniak procedure with strip-shaped specimens defining the left-hand side of the forming limit diagram (FLD) results in tearing outside the observed area of the specimen. Therefore, new shapes of test pieces were designed with a strip-shaped central area and enlarged outer areas, which were in contact with the die during the forming process. The radius of the specimen enlargement enabled a co-axial contact of its edge and direction of the material flow over the die radius during the forming process. The shape of the redesigned geometry of the specimen was analysed using the finite element (FE) program ABAQUS to minimize undesired stress concentrations at the die radius. Finally, strain paths variations due to shape change were analysed. ...

Journal ArticleDOI
TL;DR: In this paper, soft tissue deformation is modelled using incompressible non-linear elasticity, with solutions computed using the finite element method, and a range of options available when using the...
Abstract: Soft tissue deformation is often modelled using incompressible non-linear elasticity, with solutions computed using the finite element method. There are a range of options available when using the ...

Journal ArticleDOI
TL;DR: In this paper, a bimaterial specimen with interface edge cracks subjected to heating along an edge is analyzed by refined three-fringe photoelasticity (RTFP) combined with color adaptation.
Abstract: Transient thermal stresses of a bimaterial specimen with interface edge cracks subjected to heating along an edge is analysed by refined three-fringe photoelasticity (RTFP). Whole-field, noise-free, fringe order estimation using a single colour image is made possible using RTFP combined with colour adaptation. The stress intensity factors (SIFs) of the interface crack are determined through a multiparameter overdeterministic system of equations by a least-squares approach using experimental data collected automatically. The transient SIFs are found to peak to a higher value than in steady state, and the opening mode is found to be dominant. An increase in thermal load causes the crack to propagate, and this is easily visualized on the basis of quantitative fringe order data available for the whole field. The SIFs of a propagating crack are found to be low. The study shows that the crack propagates easily when the opening mode is dominant.

Journal ArticleDOI
TL;DR: In this paper, a destructive, sectioning method for measuring residual stress in welded panels, using electric strain gauges, is described, and a more thorough analysis of the method is performed.
Abstract: The current paper describes a destructive, sectioning method for measuring residual stress in welded panels, using electric strain gauges. Since this method is carried out rather simply, it has a wide range of possible applications. For this reason, a more thorough analysis of the method is performed. The potential limits of its application are investigated, together with the parameters that can influence the obtained results. The sectioning method is verified by determining residual stress in welded panels numerically. The results show it is possible to estimate the residual stress field in a welded structure rapidly and accurately, by using reasonably priced equipment.

Journal ArticleDOI
TL;DR: A novel indentation method was used to investigate the response of articular cartilage in the non-directly loaded region and suggests an added complexity to the overall permeability in the deformed tissue matrix.
Abstract: A novel indentation method was used to investigate the response of articular cartilage in the non-directly loaded region. The indenter contained a relief channel that allowed a tissue bulge to develop within it under load. Healthy bovine tissue samples were statically loaded at a nominal compressive stress of 3.6 MPa. The tissue's equilibrium deformed state was chemically fixed. Differential interference contrast microscopy was used to obtain high-resolution images of the deformed microstructure in the region of the tissue bulge.At the submicro-level, the fibrillar resistance to load is highly complex such that regions of relative compression and tension coincide along a single radial direction. This fibrillar level response is manifested as large-scale matrix shear effects within the bulge region. Further, the surface layer, besides being strain-limiting in the tangential direction, has an intrinsic resistance to axial load. Finally, the pattern of load-induced fluid flow is seen to traverse zonal depths...

Journal ArticleDOI
TL;DR: In this article, the authors used thermal stress analysis (TSA) to estimate the real crack-driving force for fatigue crack growth, and found that the results showed a very good level of agreement, illustrating the ability of TSA to infer success.
Abstract: It has been demonstrated that thermoelastic stress analysis (TSA) can provide accurate information about the real crack-driving force for fatigue crack growth. Experiments were conducted using aluminium 2024 compact tension specimens which were initially pre-cracked to different crack lengths at a constant R (R = 0). Subsequently, thermoelastic images were captured at increasing R values from 0 to 0.5 and ΔK values from 3 to 6 MPa m0.5 were calculated. The images showed a dramatic change in the stress pattern ahead of the crack tip as R decreased which was always associated with an increase in phase difference (loss of adiabatic conditions) ahead of the crack tip. This indicates that the technique is able to account for the change in conditions that arise from contact between the crack faces. To support this observation, thermoelastic results have been compared with those obtained using compliance methods. The results showed a very good level of agreement, illustrating the ability of TSA to infer successf...

Journal ArticleDOI
TL;DR: In this paper, a mathematical model has been developed to describe steady-state creep in an isotropic functionally graded composite cylinder, where the cylinder is subjected to internal pressure and is made of functionally-grained composite containing linearly varying silicon carbide particles in a matrix of pure aluminium.
Abstract: In the present study, a mathematical model has been developed to describe steady-state creep in an isotropic functionally graded composite cylinder. The cylinder is subjected to internal pressure and is made of functionally graded composite containing linearly varying silicon carbide particles in a matrix of pure aluminium. The cylinder is assumed to creep according to a threshold stress-based creep law having a stress exponent 5. The effect of employing a linear gradient in the distribution of reinforcement has been observed on the variation of creep stresses and creep rates in the composite cylinder. It is observed that the radial stress in the cylinder decreases throughout with the increase in reinforcement gradient, whereas the tangential, axial, and effective stresses increase significantly near the inner radius but show significant decrease towards the outer radius. The strain rates in the composite cylinder could be reduced significantly by tailoring the distribution of reinforcement while maintain...

Journal ArticleDOI
TL;DR: In this paper, it was shown that the conventional sheet-by-sheet analysis of residual stress measurement by the deep hole drilling method is inaccurate when in-plane stress gradients exist.
Abstract: It is shown that the conventional ‘sheet by sheet’ analysis of residual stress measurement by the deep hole drilling method is inaccurate when in-plane stress gradients exist. The influence of the interfacial tractions is analysed by the distributed dislocation technique. Finite element modelling is used to provide data for an example residual stress field with radial variation.

Journal ArticleDOI
TL;DR: In this article, a procedure based on the least square method and genetic algorithms was proposed to choose the parameters of residual stress to reduce the effects of noise and uncertainty in experimental measurements, and the performance of the method was tested against finite element simulations for typical applications such as shot peening.
Abstract: The hole-drilling method, coupled with the influence functions method, is a versatile technique for measuring residual stresses. The latter determines a relationship between residual stress and measured relaxed strains for any experimental configuration and material. However, several parameters which describe the functional basis for the residual stress must be defined. This paper presents a procedure, based on the least squares method and genetic algorithms, optimally to choose these parameters to reduce the effects of noise and uncertainty in experimental measurements. The performance of the method was tested against finite element simulations for typical applications such as shot peening, showing that the method is flexible and accurate and allows the reconstruction of residual stress at deeper positions than other techniques.

Journal ArticleDOI
TL;DR: In this article, a new modulus imaging pathway is proposed in which the inverse problem of elasticity reconstruction has been converted into a global optimization problem involving an image similarity measure, which is applied to ultrasound images and the tissue elasti...
Abstract: The in vivo estimation of tissue elasticity parameters is important for realistic tissue deformation modelling and diagnosis tasks such as cancer mass detection and characterization. Elastography (strain imaging) provides non-quantitative information about tissue stiffness and is becoming well established clinically. Acoustic radiation force imaging, supersonic shear wave imaging and (Young's) modulus imaging are all evolving as quantitative methods. This paper concerns the latter. The established approach to Young's modulus reconstruction involves solving the so-called inverse elasticity problem of recovering elastic parameters by comparing the displacement field from the measurements and the theoretical tissue deformation modelling. In this paper, a new modulus imaging pathway is proposed in which the inverse problem of elasticity reconstruction has been converted into a global optimization problem involving an image similarity measure. This approach is applied to ultrasound images and the tissue elasti...