scholarly journals Experimental Validation of Finite Element Models of Intact and Implanted Composite Hemipelvises Using Digital Image Correlation

2012 ◽  
Vol 134 (8) ◽  
Author(s):  
Rajesh Ghosh ◽  
Sanjay Gupta ◽  
Alexander Dickinson ◽  
Martin Browne
Keyword(s):  
Finite Element ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Orthopedic Implants ◽  
Image Correlation ◽  
Fe Model ◽  
Acetabular Cup ◽  
Full Field ◽  
Strain Rosette

A detailed understanding of the changes in load transfer due to implantation is necessary to identify potential failure mechanisms of orthopedic implants. Computational finite element (FE) models provide full field data on intact and implanted bone structures, but their validity must be assessed for clinical relevance. The aim of this study was to test the validity of FE predicted strain distributions for the intact and implanted pelvis using the digital image correlation (DIC) strain measurement technique. FE models of an in vitro hemipelvis test setup were produced, both intact and implanted with an acetabular cup. Strain predictions were compared to DIC and strain rosette measurements. Regression analysis indicated a strong linear relationship between the measured and predicted strains, with a high correlation coefficient (R = 0.956 intact, 0.938 implanted) and a low standard error of the estimate (SE = 69.53 με, 75.09 με). Moreover, close agreement between the strain rosette and DIC measurements improved confidence in the validity of the DIC technique. The FE model therefore was supported as a valid predictor of the measured strain distribution in the intact and implanted composite pelvis models, confirming its suitability for further computational investigations.

Finite element model updating from full-field vibration measurement using digital image correlation

2011 ◽  
Vol 330 (8) ◽  
pp. 1599-1620 ◽  
Author(s):  
Weizhuo Wang ◽  
John E. Mottershead ◽  
Alexander Ihle ◽  
Thorsten Siebert ◽  
Hans Reinhard Schubach
Keyword(s):  
Finite Element ◽  
Digital Image Correlation ◽  
Finite Element Model ◽  
Digital Image ◽  
Model Updating ◽  
Element Model ◽  
Image Correlation ◽  
Vibration Measurement ◽  
Finite Element Model Updating ◽  
Full Field

scholarly journals Acetabular Component Deformation under Rim Loading Using Digital Image Correlation and Finite Element Methods

2010 ◽  
Vol 24-25 ◽  
pp. 275-280 ◽  
Author(s):  
H. Everitt ◽  
S.L. Evans ◽  
C.A. Holt ◽  
Rob Bigsby ◽  
Imran Khan
Keyword(s):  
Finite Element ◽  
Digital Image Correlation ◽  
Wall Thickness ◽  
Digital Image ◽  
Image Correlation ◽  
Acetabular Cup ◽  
Simple Method ◽  
Press Fit ◽  
Outside Diameter ◽  
Cobalt Chrome

Total hip replacement is a highly successful operation; restoring function and reducing pain in arthritis patients. In recent years, thinner resurfacing acetabular cups have been introduced in order to preserve bone stock and reduce the risk of dislocation. However concerns have been raised that deformation of these cups could adversely affect the lubrication regime of the bearing; leading to equatorial and edge contact, possibly causing the implants to jam. This study aims to assess the amount of deformation which occurs due to the tight peripheral fit experienced during press-fit by applying rim loading to three different designs of acetabular cup: a clinically successful cobalt chrome resurfacing cup, a prototype composite resurfacing cup and a clinically successful polyethylene monobloc cup. Digital Image Correlation (DIC) was used to measure the deformation and to validate Finite Element (FE) models. DIC provided a non-contacting method to measure displacement; meaning the load could be increased continuously rather than in steps as in previous studies. The physical testing showed that the cobalt chrome cups were significantly stiffer than the composite prototype and polyethylene cups. The FE models were in good agreement with the experimental results for all three cups and were able to predict the deformation to within 10%. FE models were also created to investigate the effect of cup outside diameter and wall thickness on stiffness under rim loading. Increasing outside diameter resulted in a linear reduction in stiffness for all three materials. Increasing the wall thickness resulted in an exponential increase in cup stiffness. Rim loading an acetabular shell does not accurately simulate the in vivo conditions; however it does provide a simple method for comparing cups made of different materials.

scholarly journals Comparative Analysis of the Biomechanical Behavior of two different design metaphyseal-fitting short stems using digital image correlation; Finite Element Modelling and Analysis Validation

2020 ◽  
Author(s):  
Irini Tatani ◽  
Panagiotis Megas ◽  
Andreas Panagopoulos ◽  
Ioannis Diamantakos ◽  
Photis Nanopoulos ◽  
...  
Keyword(s):  
Finite Element ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Stress Shielding ◽  
Image Correlation ◽  
Shielding Effect ◽  
Fe Model ◽  
Biomechanical Behavior ◽  
Short Stems ◽  
Femoral Implants

Abstract Background The progressive evolution in hip replacement research is directed to follow the principles of bone and soft tissue sparing surgery. Regarding hip implants, a renewed interest has been raised towards short uncemented femoral implants. A heterogeneous group of short stems have been designed with the aim to approximate initial, post-implantation bone strain to the preoperative levels in order to reduce the risk of stress shielding. This study aims to investigate the biomechanical properties of two distinctly designed femoral implants based on experiments and numerical simulations. Nevertheless, finite element models of implant–bone constructs should be evaluated for their validity against mechanical tests wherever it is possible. In this work, the validation was performed via a direct comparison of the FE calculated strain fields with their experimental equivalents obtained using the digital image correlation technique. Results Design differences between Trilock BPS and Minima S femoral stems conditioned different strain pattern distributions. A distally shifting load distribution pattern as a result of implant insertion and also an obvious decrease of strain in the medial proximal aspect of the femur was noted for both stems. Strain changes induced after the implantation of the Trilock BPS stem at the lateral surface were greater compared to the non-implanted femur response, as opposed to those exhibited by the Minima S stem. Linear correlation analyses of the FE model-predicted strains against corresponding experimentally-measured strains revealed a strong correlation indicating that the developed FE models can be used for the calculation of stresses and strains at the implanted femurs. Conclusion The study findings support the use of DIC technique as a preclinical evaluation tool of the biomechanical behavior induced by different implants and also identify its potential for experimental FE model validation. Furthermore, this study demonstrates that stress shielding effect cannot be avoided as proximal unloading of the femur was noted after the implantation of both short stem designs. Design specific variations in short stems were sufficient to produce dissimilar biomechanical behaviors, although their clinical implication must be investigated through comparative clinical studies.

Microscopic Measurement of Strain Fields with Digital Image Correlation and Comparison to Finite Element Modelling

2019 ◽  
Vol 809 ◽  
pp. 575-580
Author(s):  
Marco Korkisch ◽  
Markus G.R. Sause
Keyword(s):  
Finite Element ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Mechanical Load ◽  
Speckle Pattern ◽  
Image Correlation ◽  
Bending Test ◽  
Fiber Reinforced ◽  
Full Field ◽  
Fiber Reinforced Materials

Digital Image Correlation (DIC) has become more and more important in the field of material characterization and research, especially for strongly anisotropic fiber reinforced materials. Its big advantage over the conventional methods like strain gauges or point based video-extensometers is the full field strain and displacement measurement and the ability to analyze three-dimensional displacements. Although theoretically, the concept of the DIC as a pure image-based method allows it to work on every imaginable scale, its main field of application is in the range, where the region of interest (ROI) has a size between 10 −2 m to 10 −1 m. In this case, imaging is accomplished with the use of high-resolution black and white digital cameras. This work is focused on a smaller scale with ROI sizes between 10 −4 m to 10 −3 m, where a digital microscope is used to create the images. The innovative idea behind this work is using the natural surface structure of a polished carbon fiber reinforced Polyamide-6 sample, produced by automated fiber placement, as a statistical pattern instead of the usual speckle pattern applied to the area to be investigated. This way the stress and strain distributionin different regions of the investigated sample area can be evaluated and displayed, while the sample is exposed to an increasing mechanical load in form of a three-point bending test. The resulting strain and displacement fields are compared to finite element modeling of the ROI. To provide an accurate model, the image of the sample is first segmented into fiber, matrix and voids using “Trainable Weka Segmentation” and the resulting phases mapped with the corresponding material properties. To compute the resulting strains in the sample, the measured displacements from the DIC on the edges of the ROI were used as boundary conditions for the simulation. Simulation and experimental results clearly point out the inhomogeneity of the strain field in these samples. Due to the presence of fiber rovings and the presence of voids, local strain values exceed the global average by up to 4 %.

scholarly journals Investigation of anisotropy effects in glass fibre reinforced polymer composites on tensile and shear properties using full field strain measurement and finite element multi-scale techniques

2021 ◽  
pp. 002199832110542
Author(s):  
Hassan Gonabadi ◽  
Adrian Oila ◽  
Arti Yadav ◽  
Steve Bull
Keyword(s):  
Finite Element ◽  
Digital Image Correlation ◽  
Digital Image ◽  
Failure Modes ◽  
Correlation Method ◽  
Image Correlation ◽  
Full Field ◽  
Glass Fibre Reinforced Polymer ◽  
Glass Fibre Reinforced ◽  
Ply Orientation

Designing highly stressed offshore renewable energy composite structures (e.g. wind and tidal turbine blades) necessitates characterisation of woven fabric composite under off axial loading. In this work a combined method of finite element analysis, digital image correlation and microscopy is used to assess the effect of ply orientation on the tensile/shear properties and failure modes of woven glass fibre reinforced polymer composites. Full field strain maps obtained by the digital image correlation method were used to evaluate the damage development and the inhomogeneity of strain localisation. The development of finite element models of mechanical test specimens is based on the analysis of micro-mechanical models of representative volume elements using a homogenisation technique in order to calculate the effective orthotropic properties. The agreement between numerically and experimentally calculated strains obtained in the elastic regimes indicates that stress analysis conducted by numerical methods is useful when characterising the effect of ply orientation on mechanical behaviour. Strain measurement conducted by the digital image correlation method indicated that there is a strong relationship between the strain distribution and the microstructure/ply orientation. In addition, it was found that the levels of localised tensile strain are higher than the global strain indicating the structural heterogeneity of the composite material. Finally, microstructural analysis of tension and shear test specimens showed that the main failure modes are de-bonded fibres, fibre pull out, in-plane/inter-laminar shear cracks and delamination.

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