Large Deformation Conditions Research Articles

Multi-Objective Optimization of a Large-Span Wing Analog Beam with Variable Cross-Sections

Aiming at the difficulty with structure and parameter design for a wing analog beam under a large deformation condition, a large-span cantilever truss model with Pro/e is designed. Then a mathematical model of the wing beam based on the Multi-objective Genetic Algorithm is proposed. Thereby the sizing optimization and shape optimization for the wing analog beam are conducted with the finite element analysis and meanwhile two main objectives minimizing the maximum von Mises stress and the mean-square error of the deformation displacement curve fitting are satisfied. A Pareto optimal solution aggregate is obtained after the optimization. Finally an optimal structure is concluded via the multi-objective optimization design, which improves the curve fitting accuracy of the wing and satisfies the stress strength requirement as well.

SU-E-J-109: Accurate Contour Transfer Between Different Image Modalities Using a Hybrid Deformable Image Registration and Fuzzy Connected Image Segmentation Method.

To develop and evaluate a tool that can improve the accuracy of contour transfer between different image modalities under challenging conditions of low image contrast and large image deformation, comparing to a few commonly used methods, for radiation treatment planning. The software tool includes the following steps and functionalities: (1) accepting input of images of different modalities, (2) converting existing contours on reference images (e.g., MRI) into delineated volumes and adjusting the intensity within the volumes to match target images (e.g., CT) intensity distribution for enhanced similarity metric, (3) registering reference and target images using appropriate deformable registration algorithms (e.g., B-spline, demons) and generate deformed contours, (4) mapping the deformed volumes on target images, calculating mean, variance, and center of mass as the initialization parameters for consecutive fuzzy connectedness (FC) image segmentation on target images, (5) generate affinity map from FC segmentation, (6) achieving final contours by modifying the deformed contours using the affinity map with a gradient distance weighting algorithm. The tool was tested with the CT and MR images of four pancreatic cancer patients acquired at the same respiration phase to minimize motion distortion. Dice's Coefficient was calculated against direct delineation on target image. Contours generated by various methods, including rigid transfer, auto-segmentation, deformable only transfer and proposed method, were compared. Fuzzy connected image segmentation needs careful parameter initialization and user involvement. Automatic contour transfer by multi-modality deformable registration leads up to 10% of accuracy improvement over the rigid transfer. Two extra proposed steps of adjusting intensity distribution and modifying the deformed contour with affinity map improve the transfer accuracy further to 14% averagely. Deformable image registration aided by contrast adjustment and fuzzy connectedness segmentation improves the contour transfer accuracy between multi-modality images, particularly with large deformation and low image contrast.

On visco-elastic modelling of polyethylene terephthalate behaviour during multiaxial elongations slightly over the glass transition temperature

The mechanical response of Polyethylene Terephthalate (PET) in elongation is strongly dependent on temperature, strain and strain rate. Near the glass transition temperature Tg, the stress–strain curve presents a strain softening effect vs strain rate but a strain hardening effect vs strain under conditions of large deformations. The goal of this work is to propose a visco hyperelastic model to predict the PET behaviour when subjected to large deformations and to manage the identification of the material properties from the experimental data by an original method. To represent the non-linear effects, an elastic part depending on the elastic equivalent strain and a non-Newtonian viscous part depending on both viscous equivalent strain rate and cumulated viscous strain are tested. The model parameters can then be accurately obtained through a comparison with the experimental uniaxial and biaxial tests. The influence of the temperature on the viscous part is also modelled and an evaluation of the adiabatic self heating of the specimen is compared to experimental results.

On the Deduction and the Application of Dynamic Similarity Criteria of Steel Structure under Large Deformation Condition

Dynamic similarity criteria for large deformation of huge steel structure were derived according to Dimensional Matrix Analysis of the Buckingham Pi theorem and the similarity relations that must be satisfied by the physical quantities of model and prototype in huge steel structure model test are obtained. The 1/50 scale model of TC power is designed and made based on the similarity theory and the dynamic experiment is done. The calculation data with similarity theory are in agreement with that of experiment. So the model test can substitute for prototype test when they satisfy the similarity relations. A new way to solve dynamic analysis problem of huge steel structure is explored.

Finite element analysis of plastic deformation in twist extrusion

Twist extrusion (TE), a promising severe plastic deformation (SPD) technique for grain refinement down to ultrafine/nanocrystalline microstructures, was introduced as an attempt to provide large plastic deformation conditions similar to those in high pressure torsion while allowing large workpiece dimensions for industrial applications. As a relatively new SPD technique, TE requires in-depth investigation of its plastic deformation characteristics. The present study investigates the influence of process parameters such as backward pressure and friction on the loading history, the stress/strain states, and the final shape of processed workpieces using the finite element method. The results provide a basis for reasonable decision of processing conditions and also identify prerequisites for studies in formability and fracture of metals subjected to TE.

Composite Structure Stress Analysis of Row Posture Micro-Piles on Slope Protection

The composite structure of row posture micro-piles is a light-weight protection structure for slope, which has the advantages of safe and quick construction, high adaptability to some special environment, and is suited to small size slope protection, especially in the emergency project. The design theory research of this composite structure is obviously deficient comparing to the engineering application. The basic requirement of the elastic foundation-beam theory application is that the foundation should be stable. Because of the row posture micro-piles composite structure improved the stability of slope, the resistant force in front of different location micro-piles is different. On the basis of the elastic foundation-beam theory, using the idea of the general micro-piles horizontal bearing capacity calculation method, the row posture micro-piles advantage have been revealed during the different calculated values of “m” and limited conditions of pile top large deformation. The computational formula of row posture micro-piles composite structure has been established on three basic calculation models, and the special response to seismic force has been calculated and analyzed in a practical case, which will provide certain reference for the micro-piles design.

Composite Structure Stress Analysis of Row Posture Micro-Piles on Slope Protection

The composite structure of row posture micro-piles is a light-weight protection structure for slope, which has the advantages of safe and quick construction, high adaptability to some special environment, and is suited to small size slope protection, especially in the emergency project. The design theory research of this composite structure is obviously deficient comparing to the engineering application. The basic requirement of the elastic foundation-beam theory application is that the foundation should be stable. Because of the row posture micro-piles composite structure improved the stability of slope, the resistant force in front of different location micro-piles is different. On the basis of the elastic foundation-beam theory, using the idea of the general micro-piles horizontal bearing capacity calculation method, the row posture micro-piles advantage have been revealed during the different calculated values of “m” and limited conditions of pile top large deformation. The computational formula of row posture micro-piles composite structure has been established on three basic calculation models, and the special response to seismic force has been calculated and analyzed in a practical case, which will provide certain reference for the micro-piles design.

Friction Stir Processing for the Modification of Laser Claded Microstructure

According to the microstructure defects of laser claded nickel alloy, such as crack and nets brittle phase, the friction stir processing (FSP) method is utilized in this paper to modify microstructure defects by the coupled effect of thermal and stress of FSP. For this purpose, two key scientific problems of large deformation condition and microstructure evolution theory during FSP, are proposed in this paper. Based on this, the following issues are highlighted in this work. Firstly, obtain the friction condition of larger deformation by continuous dirved friction experiment. Secondly, study on the temperature (T), stress (σ), and strain velocity under different processing parameters via self-developed physical simulation apparatus. Thirdly, disclose the effects of T、σ、 on the microstructure evolution and then obtain the microstructure evolution equation by dynamic re-crystallization. The above work could provide theory support for the new technique of laser cladding and FSP for preparing high performance coating.

Analysis on Stress of Inner Steels of Isolator with Large Diameter and Low IRHD Rubber under the Condition of Large Horizontal Deformation

One LNR-D1100 isolator at the stage of large horizontal deformation was analysed by FEM program in this paper, which was applied by press-shear load. The maximum S.Mises stress about inner steels of isolator have been researched. The maximum S.Mises stress will occur in the core upload area, with horizontal shear strain increasing. The core upload area will be diminution with horizontal shear deformation increasing, but the maximum S. Mises stress will be larger and larger. When large horizontal deformation of isolator occurs, there is some out-plane deformation at parts of inner steels near the upmost and downbottom of isolator. Vertical pressure will lend inner steels themself to yield when horizontal shear strain of isolator being loaded.When there is 0 MPa vertical pressure on the isolator, no vertical displacement between the top and the bottom of isolator may be helpful for the maximum S.Mises stress value of inner steels of isolator to decrease.

MO-FF-A4-03: A Parallel and Robust Image Registration Algorithm of Consecutive Stained Prostate Specimens for Ultrasound Tissue Characterization of Prostate Cancer

Purpose: To develop a robust and accurate image registration algorithm for the hymatoxylin stained pathology specimens for ultrasoundtissue characterization of prostate cancer.Method and Materials: A landmark based nonlinear image registration algorithm is proposed. It was shown to be effective and robust under conditions of large deformations. In landmark based registration, the most important step is establishing the correspondence among the selected landmark points. This usually requires an extensive search which is often computationally expensive. We introduced a non‐regular data partition algorithm using the K‐means clustering algorithm to group the landmarks based on the number of available processing cores. The step optimizes the memory usage and data transfer. We have tested our method using IBM Cell Broadband Engine platform. Results: This technology was tested and evaluated on hymatoxylin stained pathology specimens for prostate cancer. The tested data sets consisted of ten patients and each patient had more than 3 sets of image slices: 3‐D in vivo and ex vivoultrasoundimages, and 3‐D pathologyimages. The 3‐D ultrasound data had a 2mm step size while the 3‐D pathology step size was 4mm. Successful register was demonstrated with consecutive slices even though they exhibited significant slice cutting induced deformation and tissue missing. The ex vivoultrasoundimages served as a verification of our registration technique. Moreover, the parallel algorithm, which is implemented on IBM cell broad band engine, helps us to achieve 10 fold speed‐up. Conclusion: We have introduced a parallelization of an accurate image registration algorithm. The method is implemented on a IBM Cell/B.E. We have achieved approximately 10 fold speed up compared with its sequential implementation. Our proposed data partitioning approach and the parallelization schema are independent of the parallel platforms and are generic by design, therefore it can be extended to other applications on other parallel platforms.

On the interpretation of results from small punch creep tests

The small punch creep testing method is highly complex and involves interactions between a number of non-linear processes. The deformed shapes that are produced from such tests are related to the punch and specimen dimensions and to the elastic, plastic, and creep behaviour of the test material, under contact and large deformation conditions, at elevated temperature. Owing to its complex nature, it is difficult to interpret the small punch test creep data in relation to the corresponding uniaxial creep behaviour of the material. One of the aims of this paper is to identify the important characteristics of the creep deformation resulting from ‘localized’ deformations and from the ‘overall’ deformation of the specimen. Following this, the results of approximate analytical and detailed finite element analyses of small punch tests are investigated. It is shown that the regions of the uniaxial creep test curves dominated by primary, secondary, and tertiary creep are not those that are immediately apparent from the displacement versus time records produced during a small punch test. On the basis of the interpretation of the finite element results presented, a method based on a reference stress approach is proposed for interpreting the results of small punch test experimental data. Future work planned for the interpretation of small punch tests data is briefly addressed.

An Experimental Method for the In-Plane Deformation Measurement in a Sample of Transparent Polymeric Material

With the increasing development of polymeric materials, it becomes important for research on mechanical properties of polymeric materials under large deformation conditions. To know displacement distributions in the polymeric structures could help us to better understand the deformation characteristics of polymeric structures in fracture analysis. In this paper, an experimental digital moiré method for the in-plane deformation measurement in a sample of transparent polymeric material, which is a non-contact method for full-field, large deformation and real-time measurement, is presented. The measurement principles and the basic procedures of the method are explained in detail. In order to demonstrate this method, a cross grating is generated and put into a transparent polymeric specimen. The subsequent fringe and displacement analysis is carried out using the method developed by the authors.

An interaction potential based lattice Boltzmann method with adaptive mesh refinement (AMR) for two-phase flow simulation

The lattice Boltzmann method (LBM) for two-phase flow simulation is often hindered by insufficient resolution at the interface. As a result, the LBM simulation of bubbles in bubbling flows is commonly limited to spherical or slightly deformed bubble shapes. In this study, the adaptive mesh refinement method for the LBM is developed to overcome such a problem. The approach for this new method is based on the improved interaction potential model, which is able to maintain grid-independent fluid properties in the two-fluid phases and at the interface. The LBM–AMR algorithm is described, especially concerning the LBM operation on a non-uniform mesh and the improved interaction potential model. Numerical simulations have been performed to validate the method in both single phase and multiphase flows. The 2D and 3D simulations of the buoyant rise of bubbles are conducted under various conditions. The agreement between the simulated bubble shape and velocity with experiments illustrates the capability of the LBM–AMR approach in predicting bubble dynamics even under the large bubble deformation conditions. Further, the LBM–AMR technique is capable of simulating a complex topology change of the interface. Integration of LBM with AMR can significantly improve the accuracy and reduce computation cost. The method developed in this study may appreciably enhance the capability of LBM in the simulation of complex multiphase flows under realistic conditions.

Research on influence of rolling parameters on the rolling process based on numerical simulation

Rolling process involves geometric non-linearity, material non-linearity and boundary non-linearity, which is a complex and highly non-linear problem. It is impossible to obtain analytical solution in terms of trying to roll or physical experiment because of high cost, waste time and venture. Finite element method (FEM) is an effective one that can resolve large plastic deformation, thermo-mechanical coupling and complex boundary conditions between rollers and billet in the rolling process. FEM models of the rollers and billet are built by three-dimensional elastic?plastic FEM. The two-pass hot continuous rolling process of high-speed wire has been simulated accurately based on thermo-mechanical coupling condition. The equivalent of stress, equivalent of total strain and rolling force are computed for different initial rolling temperatures 1000°C and 1100°C. Furthermore, stress, strain, temperature and rolling force are also discussed for different gaps 8 mm and 12 mm, rolling velocities 1317 mm/s and 1379 mm/s and diameters of rollers 385 mm and 400 mm. The results of simulation supplied theoretical foundation for improvement of process plan, optimisation of process parameters, change of microstructure were also useful for practical manufacture.

Tensile properties of shape memory alloy chiral honeycombs

AbstractThe tensile properties of hexachiral honeycomb made of shape memory alloy (SMA) material are modelled and verified experimentally at different tensile loading and ambient temperature conditions. The numerical models describe the temperature‐pseudoelastic behaviour of the shape memory alloy materials constituted by Ni48Ti46Cu6 alloy. Parametric analysis on the Poisson's ratio effects over large strain deformation and temperature conditions are performed, as well as the analysis of the dependence of the honeycomb stress‐strain behaviour under uniaxial loading with temperature varying through the shape memory alloy phase transformation. Chiral SMA honeycomb samples are manufactured and tested under similar environmental conditions. The experimental results are compared with the numerical one, showing good convergence in terms of trends and overall quantitative values. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Integration of Geometrical Boundary Conditions on Soft Tissue Characterization under large deformation

Soft tissue characterization with finite element (FE) modeling is important to develop a realistic model for medical simulation, since it is possible to display complex tool-tissue interactions during medical interventions. However, it is difficult to integrate large deformation and geometrical boundary conditions to the FE computations. In this paper, the force responses and surface deformation fields of the tissues against the indentation were measured by a force transducer and three-dimensional optical system. Large indentation experiments on porcine liver were performed to estimate the radius of influence from the indented point up to 8 mm indentation and to measure the force response for 7mm indentation. The radius of influence region was plotted against various indentation depths and indenter shapes, and it could be used to determine the model size for the characterization. The tissue behavior of large deformation considering influence of the boundary conditions was characterized with FE modeling via hyperelastic and linear viscoelastic model.

Application of digital image correlation to the study of planar anisotropy of sheet metals at large strains

The aim of this work is to measure and model the planar anisotropy of thin steel sheets. The experimental data have been collected using the digital image correlation technique. This is a powerful tool to measure the strain field on differently shaped specimens subjected to large plastic deformations. In this manner, it is possible to observe the material behaviour under different stress-strain states, from small to large deformation conditions, on the entire specimen surface. The experimental results on smooth and notched samples have been used to characterize the flow stress curve after necking and a nonassociated plastic flow rule is proposed to describe the anisotropic behaviour of the material. To compare the experimental data with the predictions of the adopted constitutive model, a novel method, based on the image correlation results, has been implemented.

Effect of shear rate on microstructure and rheological properties of sheared wheat doughs

Structure formation in dough systems is the result of an interplay between processing conditions and subsequent interactions in the protein phase. These interactions can be both of a covalent (disulfide bonds) and physical nature and occur at all length scales. The aim of this work was to investigate the effect of simple shear deformation at various shear rates on wheat dough rheological properties, microstructure and GMP fraction. Shear processing was compared with a z-blade mixing. The contribution of disulfide bonds on different length scales was investigated using NEMI as SH-blocker agent. Dough strength and strain hardening decreased with the increase in shear rate leading to dough weakening. Sheared dough at low shear rate exhibited the highest strength among doughs under large deformation conditions. Mixing or shearing in the presence of NEMI strongly reduced fracture properties and GMP content of mixed and sheared doughs. Only the dough that was sheared at low shear rate still exhibited some strength and strain hardening. Large deformation results were integrated with linear viscoelastic properties using low shear rate–long time creep tests. Elastic compliance curves for reference doughs were lower than the dough containing NEMI. Shearing at low and intermediate shear rates gave similar elastic compliance. Dough rheological behaviour was interpreted in the context of polymer gels containing reversible cross-links and physical interactions. Shearing led to the formation of a heterogeneous structure. Very large protein domains were observed for dough at low shear rate, which became smaller upon higher shear rates suggesting that those structures are quite weak. When NEMI was present, large protein structures were lost more easily. The break-up of gluten domains during mixing and shearing was proposed to be a result from a different mechanism.

Numerical Simulations of Peristaltic Mixing

Numerical simulations of two-dimensional flow and species transport in a peristaltically driven closed mixer are performed as a function of the Reynolds number (Re⩽6288) and the normalized traveling wave amplitude (ε⩽0.3) at low to moderate Schmidt number (Sc⩽10) conditions. The mixer consists of a rectangular box with a traveling wave motion induced on its bottom surface. Flow and species mixing are produced by the surface motion. The numerical algorithm, based on an arbitrary Lagrangian–Eulerian spectral element formulation, is verified using the asymptotic solutions for small wave amplitude cases. Kinematics of large-deformation conditions are studied as a function of the Reynolds number. Species mixing is simulated at various Re and Sc conditions. Mixing index inverse (M−1) is utilized to characterize the mixing efficiency, where M−1∝exp(Pe−αt) is observed as the long-time behavior. Simulation data are utilized to determine the exponent α at various Re and Sc conditions. For all simulations, 0.28⩽α⩽0.35, typical of partially chaotic flows, have been observed. The effect of flow kinematics and species diffusion on mixing is interpreted.

Parallel computing for seismic response analysis of immersed tunnel with domain decomposition

PurposeTaking into account the long‐term influences of the non‐linear behavior of the material as well as the large deformation and contact conditions, the limiting factors of the computer simulation are the computer runtime and the memory requirement during solution of seismic response analysis for immersed tunnel. This research aims to overcome these problems.Design/methodology/approachThis research deals with parallel explicit finite element simulation with domain decomposition for seismic response analysis of immersed tunnel, which is the non‐linear and time‐dependent behavior of complex structures in engineering. A domain decomposition method based on parallel contact algorithm and dynamic‐explicit time integration procedure are used, and the latter is used for the solution of the semi‐discrete equations of motion, which is very suited for parallel processing. Using the high performance computer SGI Onyx3800, the seismic response analysis of the immersed tunnel in Shanghai is processed with more than 1.2 million nodes and more than 1 million elements in final finite element model.FindingsThe results show numerical scalability of this algorithm and reveal the dangerous joints in this immersed tunnel under Tangshan seismic acceleration, and it could also provide references for the antiseismic design of the immersed tunnel.Originality/valueWith the increasing demands in the scale, accuracy and speed of numerical simulation in geotechnical engineering, parallel computing has its great application in this area. This paper fulfils an identified method need, and it is believed more and more research work will be devoted to this research field in the near future.