Element Model For Numerical Simulation Research Articles

Effects of the embedding depth on the interfacial bond performance of horizontally NSM CFRP strips to concrete structures

Horizontally NSM CFRP strip reinforcing concrete structures are a new type of reinforcing method, as they require a small groove depth compared with that of the traditional NSM strengthening method. In order to explore the effect and mechanism of the embedding depth of horizontally NSM CFRP strip on interfacial bond performance, the single shear pull-out test was used to compare and analyze the bond properties of concrete specimens reinforced with horizontally NSM CFRP strips, EB CFRP strips, and NSM CFRP strips, and explore the effect of horizontally NSM reinforcement methods. Then, the influence of the embedding depth on interface bonding was studied. Finally, the finite element software was used to establish a finite element model for numerical simulation to verify the test results of horizontally NSM CFRP strips. The results show that the specimens reinforced with horizontally NSM CFRP strips have better bonding capacity and interface bonding stiffness. The embedding depth of the CFRP strip affects the bond efficiency between the CFRP strip and concrete, and the interfacial bonding performance is the best when the embedding depth is 12 mm. The maximum bond capacity, strain distribution, and load-end slip curve of CFRP strip under finite element numerical simulation are in good agreement with the experimental results. This indicates that the bonding performance between the horizontally NSM CFRP strip and concrete can be analyzed by the finite element method. This provides a theoretical basis for the application of horizontally NSM CFRP strip reinforcement technology in practical engineering.

Strut formation control and processing time optimization for wire arc additive manufacturing of lattice structures

Lightweight aluminum alloy lattice structures have broad application prospects in energy absorption, heat insulation, vibration isolation, etc. Additive manufacturing (AM) has been increasingly applied to fabricating lattice structures due to its efficient and flexible technical characteristics. Wire arc additive manufacturing (WAAM), featuring high productivity and low cost, is gradually considered a desirable choice for rapid prototyping of medium to large-scale freeform metallic lattice structures. However, due to the higher thermal conductivity of aluminum alloys, the forming of struts is more easily affected by the interlayer temperature. The control and prediction of strut formation during the fabricating process is the challenge facing the current industry. Simultaneously, there is also an urgent need to improve its processing efficiency. Therefore, this paper describes the strut-based finite element model for numerical simulation of the WAAM thermal process of the ER 4043 aluminum alloy lattice structure. The FE model is calibrated and validated through temperature measurements with thermocouples and a thermal imager. The calibrated FE model was employed to simulate the manufacturing process of the lattice structure. A novel fabrication sequence planning strategy was proposed to make the interlayer temperature distribution uniform so as to optimize the processing time while ensuring stable strut formation.

Experimental and Numerical Study on the Protective Behavior of Weldox 900 E Steel Plates Impacted by Blunt-Nosed Projectiles

To demonstrate the importance of incorporating Lode angle into fracture criterion in predicting the penetration resistance of high-strength steel plates, ballistic tests of blunt-nosed projectiles with a diameter of 5.95 mm impacted 4 mm thick Weldox 900 E steel plates were conducted. Impacting velocity range was 136.63~381.42 m/s. The fracture behavior and the ballistic limit velocities (BLVs) were obtained by fitting the initial-residual velocities of the projectiles. Subsequently, axisymmetric finite element (FE) models parallel to the tests were built by using Abaqus/Explicit software, and the Lode-independent Johnson–Cook (JC) and the Lode-dependent ASCE fracture criterion were incorporated into the finite element model for numerical simulation. Meanwhile, to verify the sensitivity of the mesh size in the numerical simulation, different mesh sizes were used in the shear plug area of the target. It can be found that Weldox 900 E steel has obvious mesh size sensitivity by comparing the experimental results and numerical simulation, and the JC fracture criterion and the ASCE fracture criterion predicted similar BLV for the same mesh size.

Numerical Simulation of Catenary Effect of (RC) Frame Structure Based on MSC.Marc

Since the collapse of Ronan point apartment in 1960s, progressive collapse has become a research hotspot in civil engineering. In order to study and verify the catenary effect on the resistance of the reinforced concrete frame structure to the progressive collapse. Based on MSC.Marc software, a single-story plane frame structure of reinforced concrete frame structure was selected to establish a finite element model for numerical simulation, and the numerical simulation results was compared with the experimental data.

Multiorgan motion tracking in dynamic magnetic resonance imaging for evaluation of pelvic system mobility and shear strain

AbstractFemale pelvic disorders have a large social impact; the diagnosis of which relies on a key indication: pelvic mobility. The normal mobility is present in a healthy patient, meanwhile the hypermobility can be a sign of female pelvic prolapse and the hypomobility for endometriosis. The evaluation of pelvic mobility is based on medical image analysis. However, the latter does not provide precise values of these indicators directly. Moreover, suspension devices play an important role in pelvic organ function but can hardly be observed on medical images. Our objective is to propose an image‐based analysis tool for the quantitative evaluation of pelvic mobility and the shear strain which has an impact on suspension devices. Hence, this paper introduces a such tool based on an efficient and semiautomatic motion tracking of multiple pelvic organs: the bladder, vagina, and rectum presented in dynamic magnetic resonance imaging sequences. The method was validated on prototypical images and applied to different mobility cases. The computed displacement and shear strain fields provide important information on the quality of suspension devices between organs for a fine diagnosis in the clinical context, for example, the early diagnosis of female pelvic prolapse and the localization of possible lesion areas before surgery. Meanwhile, the predicted mobility can be used to compare with the finite element model for numerical simulation.

A simplified finite element model for numerical simulation of temperature field and optimization of parameters in single crystal growth by optical floating zone technique

Optical floating zone (OFZ) is one of the most extensively used techniques to grow a variety of bulk crystals, especially single crystals of metal oxides. Although the growth parameters have been identified to be the nature of feed rod, lamp power, rotation rate, growth atmosphere and gas pressure, etc., few studies revealed the effects of these parameters on temperature field during crystal growth in image furnaces. It is well known that the temperature gradient is the driving force for float zone crystal growth. Therefore, it is essential to obtain the major growth parameters affecting OFZ temperature field. In this work, a simplified finite element (FE) model was developed for numerical simulation of temperature field during OFZ crystal growth. The effects of major growth parameters (i.e. lamp power, lamp filament, and molten zone geometry) on temperature field during OFZ crystal growth were hence identified theoretically and validated experimentally. According to the numerical calculation, the growth parameters were optimized and high-quality TiO2 single crystal was grown in practice. Prospectively, the FE model presented in this work can be applied to optimize growth parameters for other crystals as well as opens up new opportunities to understand the physical process of OFZ crystal growth in a simple and scientific way.

Numerical and experimental study of axial splitting of circular tubular structures

Among the different energy absorption mechanisms, axial splitting/curling is known as an efficient method due to its large stroke to length ratio. This paper presents a finite element model for numerical simulation of splitting of circular brazen tubes. Surface-based cohesive technique is employed for modeling fracture and cracks growth. The required material parameters are extracted from stress-strain diagram of simple tensile test. Some experimental tests were performed to validate the numerical results. For implementation of experimental procedure, the specimens were prepared by cutting the commercial brazen tube and some edge notches were created on one end side of tubes. The specimens were axially compressed between a rigid plate on top and a conical die at the bottom using Zwick universal testing machine. Good agreements were found between numerical simulations and experimental tests. The effects of several parameters such as number and length of initial notches, diameters and thickness of tubes and vertex angle of dies on energy absorption capacity of specimens are investigated, numerically.

Mode shape-based damage detection in plate structure without baseline data

In this paper, a mode shape curvature-based method for detection and localization of damage in plate-like structures is described. The proposed algorithm requires only the mode shape curvature data of the damaged structure. The damage index is defined as the absolute difference between the measured curvature of the damaged structure and the smoothed polynomial representing the curvature of the healthy structure. To examine the advantages and limitations of the proposed method, several sets of numerical simulations are carried out. Simulated test cases considering different levels of damage severity, measurement noise and sensor sparsity are studied to evaluate the robustness of the method under the noisy experimental data and limited sensor data. Applicability and effectiveness of the proposed damage detection method are further demonstrated experimentally on an aluminium plate containing mill-cut damage. The modal frequencies and the corresponding mode shapes are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer for the experimental study. Copyright © 2016 John Wiley & Sons, Ltd.

Damage Identification in Beam Structure using Spatial Continuous Wavelet Transform

In this paper the applicability of spatial continuous wavelet transform (CWT) technique for damage identification in the beam structure is analyzed by application of different types of wavelet functions and scaling factors. The proposed method uses exclusively mode shape data from the damaged structure. To examine limitations of the method and to ascertain its sensitivity to noisy experimental data, several sets of simulated data are analyzed. Simulated test cases include numerical mode shapes corrupted by different levels of random noise as well as mode shapes with different number of measurement points used for wavelet transform. A broad comparison of ability of different wavelet functions to detect and locate damage in beam structure is given. Effectiveness and robustness of the proposed algorithms are demonstrated experimentally on two aluminum beams containing single mill-cut damage. The modal frequencies and the corresponding mode shapes are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer with PZT actuator as vibration excitation source for the experimental study.

Tikhonov's regularization approach in mode shape curvature analysis applied to damage detection

In this paper an on-going research effort aimed at detecting and localizing damage in plate-like structures by using mode shape curvature based damage detection algorithm is described. The proposed damage index uses exclusively mode shape curvature data from the damaged structure. This method was originally developed for beam-like structures. In this paper, the method is generalized to plate-like structures which are characterized by two-dimensional mode shape curvature. To calculate mode shape curvatures from the measured mode shapes, three approaches are proposed: the first one is the well-known central difference approximation, the other two are classical approaches based on Tikhonov's regularization technique with smoothing functional. The applicability and effectiveness of the proposed damage detection algorithms are demonstrated experimentally on an aluminium plate containing mill-cut damage. The validity of the method is assessed by comparing the identification results of the experimental test case to the results obtained from the simulated test case. The modal frequencies and the corresponding mode shapes of the aluminium plate are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer (SLV) for the experimental study.

Numerical and Experimental Study on the Application of Mode Shape Curvature for Damage Detection in Plate-Like Structures

The paper describes on-going research effort at detecting and localizing damage in plate-like structures using mode shape curvature based damage detection algorithm. The proposed damage index uses data on exclusively mode shape curvature from the damaged structure. This method was originally developed for beam-like structures. The article generalizes the method of plate-like structures characterized by two-dimensional mode shape curvature. To examine limitations of the method, several sets of simulated data are applied and the obtained results of the numerical detection of damage are validated by comparing them with the findings of the case of the experimental test. The simulated test cases include the damage of various levels of severity. In order to ascertain the sensitivity of the proposed method for noisy experimental data, numerical mode shapes are corrupted with different levels of random noise. Modal frequencies and corresponding mode shapes of an aluminium plate containing mill-cut damage are obtained via finite element models for numerical simulations and by using a scanning laser vibrometer (SLV) for the experimental study.

Behavior of FRP Sandwich Panels under Synergistic Effects of Low Temperature and Cyclic Loading I: Experiment and Numerical Simulation Method

The paper is concerned with using experiments and numerical simulations to study the mechanical performance of a Honeycomb Fiber-Reinforced Polymer (HFRP) sandwich panel at different temperatures, especially at low temperatures coupled with cyclic loadings. All physical tests were performed in a temperature controlled room and used a three-point bending setup where the applied load gradually increased from zero to 36kN. Experimental results show that the stiffness of the panel becomes softer at some lower temperatures. In order to eliminate the influence of the initial conditions, an incremental method was introduced to process the experimental results. This method treated all displacements and strains as zero when applying a load of 4.5kN. Furthermore, the change in stiffness of the panel was obtained through the use of a special equivalent stiffness which involved measuring the change of the stiffness of the panel. After comparing different methods, the composite shell method was used to build finite element models for numerical simulations in ABAQUS. Reduction of moduli and Random Mesh Size Method (RMSM) were employed to simulate microcracking between fibers and matrix and debonding between the core and face sheets, respectively.

A hybrid discrete–finite element model for numerical simulation of geomaterials

A hybrid discrete–finite element model is introduced for simulation of mechanical behavior of geomaterials. The soil or rock is modeled as a system of discrete balls that interact through normal and shear springs. The balls can be bonded at the contact points to withstand the applied deviatoric stresses. The important feature of this model is that the confining walls that can be imagined for example as the surrounding membrane or the mold in a physical test are modeled by deformable finite elements. This allows simulation of laboratory test features more realistically compared to the situations where the surrounding walls are rigid. The relationships between micro- and macro-properties are investigated in this paper as well. These relationships and the corresponding curves are helpful tools in calibration of the numerical model for the macroscopic elastic properties.

A general finite element model for numerical simulation of structure dynamics

A finite element model used to simulate the dynamics with continuum and discontinuum is presented. This new approach is conducted by constructing the general contact model. The conventional discrete element is treated as a standard finite element with one node in this new method. The one-node element has the same features as other finite elements, such as element stress and strain. Thus, a general finite element model that is consistent with the existed finite element model is set up. This new model is simple in mathematical concept and is straightforward to be combined into the existing standard finite element code. Numerical example demonstrates that this new approach is more effective to perform the dynamic process analysis in which the interactions among a large number of discrete bodies and continuum objects are included.

Some advances and applications in quadratic programming method for numerical modeling of elastoplastic contact problems

This paper reviews briefly some advances and applications in parametric quadratic programming (PQP) method for numerical modeling of elastoplastic contact problems. The parametric variational principle (PVP) and the corresponding finite element model for numerical simulation of 3D elastoplastic frictional contact problems with isotropic/anisotropic (orthotropic) friction law are presented. The finite element software JIFEX is then developed with the application-oriented concept for nonlinear analysis of complex structures in general purposed engineering. Some typical engineering applications such as compressor impeller and the railway wheel/rail contact analysis are shown to illustrate the potential of the software developed.

A finite element model for numerical simulation of thermo-mechanical frictional contact problems

Two kinds of variational principles for numerical simulation of heat transfer and contact analysis are respectively presented. A finite element model for numerical simulation of the thermal contact problems is developed with a pressure dependent heat transfer constitutive model across the contact surface. The numerical algorithm for the finite element analysis of the thermomechanical contact problems is thus developed. Numerical examples are computed and the results demonstrate the validity of the model and algorithm developed.

NUMERICAL SIMULATION OF CONTINUOUS CHIP FORMATION DURING NON‐STEADY ORTHOGONAL CUTTING

A finite element model for numerical simulation of non‐steady but continuous chip formation under orthogonal cutting conditions is described. The problem is treated as coupled thermo‐mechanical. A velocity approach has been adopted for the proposed solution. The computational algorithm takes care of dynamic contact conditions and makes use of an automatic remeshing procedure. The results of simulation yield complete history of chip initiation and growth as well as distributions of strain rate, strain, stress and temperature. The paper includes a detailed presentation of computational results for an illustrative case.