Contact-free measurement and non-linear finite element analyses of strain distribution along wood adhesive bonds

Holzforschung ◽  
2005 ◽  
Vol 59 (6) ◽  
pp. 641-646 ◽  
Author(s):  
Erik Serrano ◽  
Bertil Enquist
Keyword(s):  
Finite Element ◽  
Measurement Technique ◽  
Strain Distribution ◽  
Wood Adhesive ◽  
Load Level ◽  
Image Correlation ◽  
Large Strains ◽  
Adhesive Bonds ◽  
Non Linear ◽  
Contact Free

Abstract The strain distribution along wood adhesive bonds was studied using a contact-free measurement system based on a white-light digital image correlation (DIC) technique. Two different specimen geometries and three different adhesives were investigated. The specimen geometries were according to the standards EN302-1 and ASTM D905. The adhesives tested were a phenolic resorcinol (PRF), a one-component polyurethane (PUR) and an epoxy (EPX). In addition to the experimental investigation, a finite element study using a non-linear fracture mechanics model for the adhesive bond line was carried out, aimed at investigating whether deformation measurements could predict differences in the mechanical behaviour of the adhesives. The measurement technique was found to be capable of distinguishing, in terms of their strain distributions at a given load, adhesives that differed markedly from one another. For example, the brittle PRF adhesive showed more localised strains than the more ductile EPX and PUR adhesives did at the same load level. Another conclusion from this study is that the measurement technique used is applicable to situations in which large strains occur. Thus, the technique used here is of great interest for use in the calibration of finite element models and constitutive theories and for the design of test set-ups.

Comparison of femur strain under different loading scenarios: Experimental testing

2020 ◽  
Vol 235 (1) ◽  
pp. 17-27
Author(s):  
Ievgen Levadnyi ◽  
Jan Awrejcewicz ◽  
Yan Zhang ◽  
Yaodong Gu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Strain Distribution ◽  
Element Model ◽  
Surface Strain ◽  
Image Correlation ◽  
Loading Conditions ◽  
Bone Implant ◽  
Bone Stiffness

Bone fracture, formation and adaptation are related to mechanical strains in bone. Assessing bone stiffness and strain distribution under different loading conditions may help predict diseases and improve surgical results by determining the best conditions for long-term functioning of bone-implant systems. In this study, an experimentally wide range of loading conditions (56) was used to cover the directional range spanned by the hip joint force. Loads for different stance configurations were applied to composite femurs and assessed in a material testing machine. The experimental analysis provides a better understanding of the influence of the bone inclination angle in the frontal and sagittal planes on strain distribution and stiffness. The results show that the surface strain magnitude and stiffness vary significantly under different loading conditions. For the axial compression, maximal bending is observed at the mid-shaft, and bone stiffness is also maximal. The increased inclination leads to decreased stiffness and increased magnitude of maximum strain at the distal end of the femur. For comparative analysis of results, a three-dimensional, finite element model of the femur was used. To validate the finite element model, strain gauges and digital image correlation system were employed. During validation of the model, regression analysis indicated robust agreement between the measured and predicted strains, with high correlation coefficient and low root-mean-square error of the estimate. The results of stiffnesses obtained from multi-loading conditions experiments were qualitatively compared with results obtained from a finite element analysis of the validated model of femur with the same multi-loading conditions. When the obtained numerical results are qualitatively compared with experimental ones, similarities can be noted. The developed finite element model of femur may be used as a promising tool to estimate proximal femur strength and identify the best conditions for long-term functioning of the bone-implant system in future study.

Study of Mode I-II Mixed Crack Propagation in Electrofusion Joint of Polyethylene Pipe

2018 ◽  
Author(s):  
Yue Zhang ◽  
Jianfeng Shi ◽  
Jinyang Zheng
Keyword(s):  
Finite Element ◽  
Crack Propagation ◽  
Strain Distribution ◽  
Axial Stress ◽  
Propagation Direction ◽  
Image Correlation ◽  
J Integral ◽  
Full Field ◽  
Crack Propagation Direction ◽  
Finite Element Numerical Simulation

Electrofusion joint plays an important role in connecting polyethylene (PE) pipe. In our previous study, penetrating crack failure through the fitting with an angle of about 70° was observed, and axial stress was found to be an important factor in the crack propagation. In this paper, experiments were carried out to study the crack propagation phenomena of the electrofusion joint of PE pipe. Digital Image Correlation (DIC) method was used to measure the displacement on specimen’s surface, as well as full-field strain distribution, based on which the J-integral of the crack tip was calculated. Besides, a finite element numerical simulation was conducted, and its accuracy was verified by experimental J-integral value. Through combination of experimental observations and finite element method, the phenomenon that the angle between crack propagation direction and tube axial is about 70° is detailed analysed. By comparison and analysis of the testing results, critical J-integral value during crack propagation is determined. Furthermore, critical J-integral value of crack propagation in electrofusion joint is predicted.

Large deformation finite element analysis of non-linear viscoelastic membranes with reference to thermoforming

1993 ◽  
Vol 28 (1) ◽  
pp. 31-51 ◽  
Author(s):  
S Shrivastava ◽  
J Tang
Keyword(s):  
Finite Element ◽  
Relaxation Function ◽  
Time Dependent ◽  
Large Strains ◽  
Element Analysis ◽  
Contact Conditions ◽  
Non Linear ◽  
Linear Viscoelastic ◽  
Finite Element Formulations ◽  
Good Agreement

This paper reports on the development of finite element formulations and computer programs for modelling free and constrained inflation of thin polymeric sheets in the context of thermoforming of plastic articles. In recognition of the generally time-dependent viscoelastic behaviour of polymers, and the large strains encountered in thermoforming applications, the material is modelled as non-linear visoelastic. For this purpose the constitutive relation proposed by Christensen (1)† is adopted, assuming the relaxation function to be exponential. Most of the published work on non-linear viscoelastic membranes deals with simple axisymmetric geometries, while the finite element formulations presented in this work are for both axisymmetric and non-axisymmetric membrane inflations, including contact against constraining surfaces. Both frictionless and slipless idealizations of contact conditions are studied. The finite element solutions of free and constrained inflations of circular membranes serve as illustrative examples for the axisymmetric case, while those for elliptical membranes demonstrate the non-axisymmetric cases. Comparison of the finite element results with the analytical solutions obtained (Appendix 1) for some simple free and constrained inflation problems shows good agreement.

scholarly journals Determination of bond model for 7-wire strands in pretensioned concrete beam

2021 ◽  
Vol 61 (6) ◽  
pp. 740-748
Author(s):  
Vadzim Parkhats ◽  
Rafał Krzywoń ◽  
Jacek Hulimka ◽  
Jan Kubica
Keyword(s):  
Finite Element ◽  
Strain Distribution ◽  
Concrete Beam ◽  
Bond Stress ◽  
Image Correlation ◽  
Finite Element Models ◽  
Bond Model ◽  
Comparison Results ◽  
Pretensioned Concrete

A correct choice of a bond model for prestressing tendons is crucial for the right modelling of a structural behaviour of a pretensioned concrete structure. The aim of this paper is the determination of an optimal bond model for 7-wire strands in a prestressed concrete beam produced in a precast concrete plant of Consolis Poland. ATENA 3D is used to develop finite element models of the beam that differ only in a bond stress-slip relationship of tendons. The bond stress-slip relationships for modelling are taken from the results of bond tests carried out by different researchers in previous years. Moreover, for comparison purposes, a simplified 2D model of the beam is created in Autodesk Robot. The strain distribution at the time of the strand release is found for each of the finite element models. The determined strain distributions are compared with the strain distribution in the beam established by an experimental test using a measuring system based on a digital image correlation. On the basis of the comparison results, the most appropriate bond models for 7-wire strands used in the beam are identified.

Integration of Laser Surface Scanning and Non-Linear Finite Element Analysis for the Assessment of Volumetric Corrosion in Pipeline Fittings

2014 ◽  
Author(s):  
Robert M. Andrews ◽  
Matthew Hadden ◽  
Paul Casson ◽  
Tamsin Kashap ◽  
Steven A. Johnstone
Keyword(s):  
Finite Element ◽  
Surface Profile ◽  
Initial Study ◽  
Large Strains ◽  
Fe Model ◽  
Element Analysis ◽  
Artificial Defect ◽  
Failure Pressure ◽  
Numerical Predictions ◽  
Non Linear

Methods for assessing volumetric corrosion in fittings such as bends or branch connections are not well developed, although limited guidance is given in some codes. For other components and cases where the corrosion profile is complex or there are large external loads, these methods cannot be applied. In addition, detailed analysis of the actual corrosion shape and the applied loads may demonstrate significant additional margins compared with the code method. To do this, the actual profile of the corroded shape is required. This paper reports an initial study investigating methods of non-contact scanning a corroded fitting, constructing a finite element (FE) model of the corroded shape and prediction of the failure pressure. Two corroded welded branch connections which had been removed from a block valve installation were used. The surface profiles were measured using a laser scanner and the scans imported into a FE model generation system and detailed models of the damaged connections then developed. Non-linear analyses were carried out to predict the failure pressure using assumed and measured stress-strain curves. Failure was predicted to occur in the area of the weld between the forged connection and the header. Hydrostatic burst tests were carried out on the connections. In both tests failure initiated in the header pipe remote from the branch and the corroded area, and as a result the failure pressures were below those predicted by the FEA. However, the failures did occur at pressures about 20% higher than the original hydrostatic test pressure. Strain gauge data from the pressure tests were in reasonable agreement with the numerical predictions. Large strains were predicted and measured in the large artificial defect introduced in the second test. This program has demonstrated the feasibility of making detailed surface profile measurements of corroded components on site, and then using these profiles in a non-linear FEA to predict failure pressures. The development work needed for routine application is discussed, and the selection of a failure criterion for the FEA when analysing complex geometries where there may be substantial through wall bending is also considered.

Research on Crack Measurement Technique in Solids Material with Digital Image Correlation (DIC)

2007 ◽  
Vol 353-358 ◽  
pp. 2606-2610
Author(s):  
Jian Xin Zhu ◽  
Zeng Liang Gao
Keyword(s):  
Digital Image Correlation ◽  
Crack Propagation ◽  
Measurement Technique ◽  
Cross Correlation ◽  
Image Correlation ◽  
Solid Materials ◽  
Fatigue Characteristic ◽  
Correlation Algorithm ◽  
Contact Free ◽  
Measurement Approach

The measurement of crack propagation in solids is of vital importance for the research of the fatigue characteristic of solid materials. By analysis of the image based measurement technique, a contact-free crack measurement approach was proposed based on image cross correlation algorithm. Experiment was performed to verify the validity of this method and it was found that the method is of high precision. The approach distinguished itself from traditional methods by several characteristics: it has relatively high measuring accuracy, the crack propagation can be continuously measured with this method, the amount of information that the approach provide is much more abundant than that of other methods. The method is proved to be an efficient method for crack measurement and can be applied in fatigue induced material cracking researches.

scholarly journals Measurement of moisture-related strain in bonded ash depending on adhesive type and glueline thickness

Holzforschung ◽  
2016 ◽  
Vol 70 (2) ◽  
pp. 145-155 ◽  
Author(s):  
Markus Knorz ◽  
Peter Niemz ◽  
Jan-Willem van de Kuilen
Keyword(s):  
High Strain ◽  
Urea Formaldehyde ◽  
Wood Adhesive ◽  
Image Correlation ◽  
Adhesive Bonds ◽  
Mechanical Loads ◽  
Resorcinol Formaldehyde ◽  
Emulsion Polymer ◽  
Distinct Strain ◽  
Adhesive Type

Abstract Structural wood-adhesive bonds (WAB) have to be durable while subjected to considerable stresses caused by mechanical loads and moisture content changes. To better understand the moisture-related durability of WABs, knowledge is important of how moisture changes generate strain in the bond. In this paper, strain on end-grain surfaces of bonded ash specimens was analyzed by means of digital image correlation. Strains were generated by wood shrinkage, and the evaluation was focused on shear strain (SStr). The bond lines were studied depending on the adhesive type – phenol resorcinol formaldehyde (PRF), melamine urea formaldehyde (MUF), polyurethane (PUR), and emulsion polymer isocyanates (EPI). Moreover, three different glueline (GL) thicknesses of MUF were taken into consideration. Comparing the adhesive types, SStr distributions (SStrD) were strongly influenced by adhesive elasticity. MUF and PRF bonds were quite rigid and were associated with pronounced strain amplitudes in and close to the GL together with strain dissipation reaching deep in the wood. PUR and EPI adhesives were more elastic and therefore allowed for smoother strain transition showing less distinct strain peaks. GL thickness had significant impact on SStrD. A high strain level and direct strain transition between adherends was found for the 0.01 mm GL, whereas a pronounced strain decrease was observed in the 0.1 and 0.2 mm GLs. This indicates different stress levels in the wood-adhesive interface dependent on GL thickness.

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