Finite Element Method Analysis Research Articles

A comprehensive finite element framework for modeling of PEX-Al-PEX composite pipes

While PEX-Al-PEX composite pipes are widely used in various applications, suitable tools and models for simulating their performance under different working conditions have not been made available. Therefore, the present study aims to develop a comprehensive finite element model to study the behavior of PEX-AL-PEX pipes at different temperatures and strain-rates. To achieve this, the properties of the pipe layers have been obtained for different temperature and strain-rate values through experimental tests. To assess the accuracy of the developed finite element model, the lateral compression and the split-disc tension tests have been performed under different conditions using both experimental and finite element analysis methods, and their results have been compared. The proposed model can be used to study the behavior of PEX-AL-PEX pipes with different materials and geometries in various conditions and applications, as well as for optimizing the design and manufacturing of these pipes.

Evaluation of the Biomechanical Effects and Stability of Titanium and Carbon Fiber-Reinforced Polyetheretherketone Mini Plates in Le Fort I Advancement Osteotomy Fixation Using Finite Element Analysis.

This study aimed to investigate the biomechanical properties of 60% carbon fiber-reinforced polyetheretherketone (Cfr-PEEK), which exhibits high mechanical strength and can address the limitations of titanium mini plates used in Le Fort I osteotomy. Models were created using the FEA method based on tomography images of adult individuals. A 5 mm maxillary advancement was applied to the models following Le Fort I osteotomy. Mini plates made of titanium and 60% Cfr-PEEK were used. Support was provided by the nasomaxillary and zygomaticomaxillary buttresses to fix a total of four L-shaped mini plates. Oblique loads of 125 N, directed from palatal to buccal, and a total of 250 N compression loads were applied to the central fossa of the premolar and molar teeth in the maxillary model at a 30° angle relative to the long axis of the teeth. Displacement values at the osteotomy line, Von Mises stresses in the mini plate-screws, and principal stresses in the bone were compared. Examination of stress values in the fixation systems of the models revealed higher stress values in the Cfr-PEEK model compared to the titanium model. However, these stresses did not reach levels that would deform the Cfr-PEEK fixation systems. Stress and displacement values in the bone were lower in the Cfr-PEEK model compared to the titanium model. According to the findings of our study, Cfr-PEEK represents a viable alternative to titanium for mini plate material in Le Fort I osteotomy, offering biomechanical advantages.

The mixed displacement method to avoid shear locking in problems in elasticity

AbstractThe mixed displacement (MD) method was initially developed to mitigate geometrical locking effects in beams, plates, and shells with the intention of having intrinsically locking‐free characteristics while using equal‐order interpolation for all degrees of freedom. In other words, it is an unlocking scheme that works independent of the element shape, polynomial order, and discretization scheme. It includes additional degrees of freedom that adhere to a carefully designed differential relation that can be interpreted as a kinematic law, incorporated in a mixed sense. Certain constraints are to be enforced on these additional degrees of freedom to obtain a well‐posed system of equations. In this work, the MD method is extended for problems in solid mechanics. We present the underlying variational formulation, followed by its application to 2D solid elements. Additionally, we showcase an idea to enforce the additional constraints in a general sense. Various numerical examples, within the framework of the finite element method and isogeometric analysis, are outlined to demonstrate the performance of the MD method in the geometrically linear and geometrically nonlinear cases.

A DIC-FEM hybrid method for measuring strains near fiber-matrix interface of CFRP cross section

A DIC-FEM hybrid method is proposed to capture micro-scale deformation behavior near the fiber-matrix interface by combining displacement distributions measured using digital image correlation (DIC) with finite element method (FEM) analysis. Images of CFRP cross section with fine random pattern before and after deformation are taken with a laser microscope. The in-plane displacement components near the interface of fiber and matrix are obtained using digital image correlation and they are used as the input of the hybrid method. Not only the displacement distributions but the strain fields are determined using the proposed hybrid method, based on the superposition principle, so that the same distributions are obtained as those obtained by the measurement. The proposed DIC-FEM hybrid provides the strains near the interface between fiber and matrix, compensating for the insufficient resolution of microscope images.

Research on Damage Detection of Dual-Rotor Synchronous Excitation Mine Screen Beams Based on Strain Mode Difference Vibration Mode Analysis

The frame beam structure of the mine screen, subjected to various excitations, is a critical component of mining machinery. Its stress is intricate, the operational environment is severe, and damage can lead to catastrophic failures resulting in machinery destruction and fatalities. Based on the characterization of the vibration response of mine screen frame beams with varying degrees of damage at the same location and with the same degree of damage but at different locations, this paper develops a method of strain modal difference vibration pattern analysis and damage feature extraction for the detection of structural damage in beams. This method is based on the sensitivity of the sudden change in vibration strain modal difference to small deformations. This method solves the problem of using the conventional structural finite element analysis or experimental modal analysis methods to obtain the displacement mode, intrinsic frequency, and other characteristics, which make it difficult to effectively identify the actual engineering, with the damage conditions of the damage state and damage location of the mine screen frame beam problems. The feasibility and validity of the engineering application of the concept are demonstrated through instances.

Research on the design and thermal performance of vacuum insulation panel composite insulation materials

This study introduces a novel design methodology for composite insulation material aimed at reducing the operational energy consumption of buildings. Vacuum Insulation Panels (VIPs) are recognized for their excellent insulating properties due to their vacuum-sealed nature that minimizes thermal transmittance. However, VIPs are susceptible to damage from temperature stress and abrasion, which can compromise vacuum integrity and degrade performance over time. To mitigate this, a protective layer of rock wool board is adhered to the exterior of the VIP to create a composite insulation material. The thermal conductivity characteristics of the composite insulation materials are experimentally measured and then corroborated with simulations using ANSYS software to affirm the precision of finite element analysis methods. A composite Insulation wall model is constructed using ANSYS to analyze the impact of varying the thickness of the composite insulation materials and the pressure within the VIP on thermal performance. The findings demonstrate that the thermal transmittance coefficient of the composite insulated wall diminishes with increased insulation material thickness and rises with increased pressure within the VIP. Additionally, rock wool boards significantly enhance the durability of the composite insulation material.

Optimization of high performance hybrid composite under ballistic test and performance of the hybrid composite under IED blast

Abstract In this investigation a novel material has been developed comprising of Silicon Carbide (ceramic), Aluminium honeycomb (metal) and Poly Ether Ketone (PEK)—Poly Phynelene Benzobisoxaole (PBO) fiber based blast proof composite. The experimental results proved that this polymeric composite is highly suitable for 9 mm pistol bullet with 430 m s−1 at distance of 5 m as well as for improvised explosive devices blast to absorb the sharpnels/splinters. This investigation also highlights an efficient back layer for a blast-proof sandwich composite. Layer optimization was carried out by finite element method (FEM) analysis of blast effect on the multi-layer polymer composite panel by ANSYS Explicit Dynamics (LS DYNA Solver). The resultant optimal layers of PEK-PBO composites then tested to validate results of FEM analysis. Experimentally it is proved that polymeric composite with 10 layers of PBO fabric when test fired under 9 mm pistol bullet with 430 m s–1 at distance of 5 m, the bullet penetrates, however, when the polymeric composite is made with a total of 20 layers of PEK-PBO fabric, all the test fired bullets are stopped. Therefore, under SNANAG 4569 blast test, the polymeric composite was essentially made with 20 layers of PBO fabric and it is experimentally proved that PEK-PBO composite is highly efficient as the back layer of hybrid composite and all the sharpnels of IED blast are completely absorbed.

Numerical and analytical study on the punching shear capacity prediction for eccentrically loaded flat slabs with openings

The punching shear behavior of interior flat slab was examined in this study in the absence of shear reinforcement using numerical and analytical techniques. The effect of sensitive parameters was investigated and their influence was examined and reported including the opening existence and location, loading eccentricity, and slab height. The effect of the reinforcement ratio is neglected in most of the literature models and code provisions with the influence of loading eccentricity being addressed inappropriately. Therefore, this study adopted the nonlinear finite element analysis (NLFEA) method for the numerical part where the flat slab punching shear behavior was studied in detail. Results were compared in their behavior at both cracking and ultimate stages, absorbed energy, elastic and plastic stiffnesses, and general trend lines were provided. The effect of the reinforcement ratio was assessed indirectly with slabs of similar reinforcement area and different slab effective depths (65, 95, 125, and 155) mm where a 25 mm concrete cover was used. In addition, the NLFEA punching shear capacity results were compared with three international codes (American Concrete Institute (ACI318-119), EuroCode (EC2), and Model Code (MC2010)) to highlight their potential predictability and weakness points. It was found that the MC2010 has the most conservative prediction, followed by the EC2 and the ACI318-19 predictions. Therefore, two modification parameters were proposed for the ACI318-19 punching shear capacity calculation with R2 value of 0.98. The modified version of the ACI318-19 was validated using experimental data from the literature proving a high prediction capability.

Microstructural analysis of AA8079 alloy sheets formed by friction stir incremental forming

Friction Stir Incremental Forming (FSIF) is an innovative solid-state metal-forming technique that uses frictional heat and mechanical deformation to create complex shapes without dyes. It has found applications in industries like aerospace, automotive, and consumer goods. In this study, FSIF was applied to AA8079 alloy sheets to form cone and pyramid geometries. A detailed investigation of process parameters such as spindle speed, table feed, step size, and coatings was conducted to assess their effects on surface roughness and forming forces. Optimal parameters were identified using the Taguchi L27 orthogonal array and the TOPSIS method, which determined the best settings as a wall angle of 20°, a step size of 1 mm, a spindle speed of 1500 rpm, and a table feed of 2400 mm/min. Scanning electron microscopy was employed to study surface roughness, texture, and defects, revealing the influence of these parameters on surface quality. Additionally, Finite Element Method (FEM) analysis, performed using ABAQUS software, was used to predict formability and stress distribution during the forming process. Key results showed successful formation of cone and triangular pyramid shapes on AA8079 sheets, with FEM accurately predicting stress levels. This comprehensive study provides valuable insights into optimizing FSIF for improved material performance and structural integrity. The findings emphasize the importance of fine-tuning FSIF parameters to enhance surface finish and reduce defects, offering potential improvements for various industrial applications.

UV ozone‐modified Fe3O4‐PDMS film for solvent‐driven soft actuators with controlled and multi‐stable deformations

AbstractIn recent years, solvent‐driven actuators have been capable of controlling deformations in response to external stimuli. However, a magnetic polydimethylsiloxane (PDMS) composite film with magnetic properties is traditionally developed using the micro‐electro‐mechanical system process. Although it has general actuation deformation, the composite film suffers from the problems of actuation and control. Here, this is done by co‐mixing PDMS and ferrosoferric oxide (Fe3O4) then waiting for curing and then undergoing ultraviolet‐ozone (UVO) surface treatment. By adjusting the time and orientation of the UVO treatment, a series of solvent‐driven actuators with multiform steady‐state structures (e.g., mono/bistable helix) is proposed. In addition, the deformation of the composite film under different geometrical parameters and surface constraints was visually predicted by incorporating finite element analysis methods. In addition, the controlled deformations of the composite film (such as box‐like, folded, and so on) are carried out by self‐morphing design. Finally, four bionic applications are also proposed to demonstrate the practical use of soft actuators based on Fe3O4‐PDMS films in bionic robots. This work provides new strategies for designing and fabricating programmable and controllable soft actuators and lays the foundation for a wide range of smart material applications.

Superconvergence analysis of low order nonconforming finite element method for coupled nonlinear semiconductor device problem

Superconvergence analysis of low order nonconforming finite element method for coupled nonlinear semiconductor device problem

Numerical and experimental analysis of Al/GFRP joint for optimization of adhesive bonding strength using response surface method by considering surface patterning of the joints

Nowadays, adhesive bonding of metals and composites is widely used in the aerospace, automotive and military industries. In the present research, the finite element analysis (FEA) and response surface method (RSM) are used to optimize adhesive bonding strength between aluminum (Al) and glass fiber reinforced polymer (GFRP). For this purpose, the influence of the parameters of joint type, groove shape, groove number, and groove angle was investigated on the bonding strength. The joint type includes Al/Al, Al/GFRP and GFRP/GFRP, the groove shape includes V-shape, square and concave, the groove number includes 1, 3 and 5 grooves, and the groove angle includes 0, 45 and 90º. In order to model the crack growth in the simulation of adhesive bonding, the cohesive zone model was applied. Finally, the optimal sample is fabricated to examine its strength in temperature-humidity environmental conditions. The results of simulation and optimization indicated that the bonding strength improved in Al/Al mode with one square groove at 0° groove angle. The stress-strain diagram obtained from the simulation and optimization results was in good agreement with the sample made under optimal conditions. Moreover, the tensile strength of the optimal sample at temperature-humidity conditions was higher than the tensile force of the sample without groove.

Basic Study on the Proposal of New Measures to Improve the Ductility of RC Bridge Pier and Their Effectiveness

To enhance the seismic performance of reinforced concrete (RC) elements, it is essential to consider both strength and ductility post-yielding. This study proposed a novel method to improve the ductility of RC piers by using preformed inward-bending longitudinal reinforcements at the plastic hinges. Two full-scale model tests of standard and ductility-enhanced (DE) RC piers and numerical simulations were conducted. The lateral reversed cyclic loading experiments were conducted to assess the effectiveness of this new approach. The performance was evaluated regarding failure mode, plastic hinge distribution, hysteretic properties, normalized stiffness degradation, normalized energy dissipation capacity, bearing capacity, and ductility. Non-linear finite element method (FEM) analyses were also carried out to investigate the usefulness of the proposed method by DIANA, and simulation was validated against the experiment results by hysteretic curves, skeleton curves, failure mode crack pattern, ductility coefficient, and bearing capacity. The results indicated that the proposed method enhanced bearing capacity, resistance to stiffness degradation, energy dissipation capacity, and ductility. Additionally, it was observed that the preformed positions and curvature of the main steel bars influenced the plastic hinge location and the buckling of longitudinal reinforcements. FEM analysis revealed that it might be reasonable to deduce the other factors that influenced the ductility of the specimens by using the same material parameters and models.

Permeation of per- and polyfluoroalkyl substances (PFAS)-laden leachate in landfills as an outcome of puncture failures of high-density polyethylene geomembranes

In response to growing environmental concerns regarding the presence of per- and polyfluoroalkyl substances (PFAS) in landfills, this study explores PFAS permeation through pinhole defects of high-density polyethylene (HDPE) geomembranes (GMs) experimentally. Specifically, this study aims to: (i) investigate the adsorption of PFAS onto HDPE GMs, (ii) evaluate the effectiveness of GMs experimentally in retaining PFAS-laden leachate in the event of a puncture failure, (iii) assess the critical conditions leading to puncture failure of GM using mechanical characterization testing with complementary finite element method (FEM) analyses with the input data from mechanical characterization. Our findings show limited intermolecular attractive interactions between PFAS and GMs, and surfactant properties of PFAS contribute to higher leachate permeation through pinholes. In general, highly fluorinated, short chain PFAS exhibit increased permeation rates, which was attributed to their size and greater propensity to align at the water-air interface. This study underlines the environmental implications of PFAS-laden leachates especially when there are no proper liner systems or leachate collection systems in place underscoring the necessity for modern landfill design and management practices to mitigate environmental risks associated with PFAS.

Finite element analysis method for the sliding cable analysis: The sliding variable method

A sliding cable structure is typically characterized by uncertainty of sliding and complexity of friction at the cable-strut joints, which makes accurate and efficient analysis difficult. In this study, we have proposed the sliding variable method, to simulate the cable sliding process considering friction equivalently and analyze the internal force and deformation response at the equilibrium state quickly and accurately. The sliding variable method takes the sliding vector of the cable at cable-strut joints as the basic variable, extracts the slippage stiffness matrix and establishes the cable force balance equation to solve the sliding vector, and simulates the change of cable original length and cable force by applying equivalent temperature load. In this paper, first, the basic principles and calculation procedures of the sliding variable method without considering friction, are discussed in detail to simulate frictionless slip of continuous cable, using with roller-type cable-stayed joints. as an example. On this basis, a calculation model incorporating the effects of friction is analyzed, a method to judge the sliding situation and balance relation of cable-forces is revealed, and the calculation principle and steps of the method are further deduced. Meanwhile, choosing a multi-joint cable–pulleys model as an example, the accuracy and rationality of the sliding variable method with and without considering friction are verified respectively. This method requires a conventional finite element calculation and second calculation alternately. Finally, to improve the practicability and computational efficiency of the sliding variable method, a macro document was compiled using the secondary development function of ANSYS parametric programming language (APDL) according to the basic framework of the sliding variable method. The frictional sliding behaviors in two typical engineering cases, a cable girder and a prestressed fish-belly girder on a foundation pit, are analyzed by using the compiled macro document in finite element program. The results show that the compiled macro document can be both accurate and efficient in calculating and analyzing cable sliding problems and can be easily popularized and applied in engineering practices.

Improving flexural performance of repaired C/C composites through Ti addition: Mechanism analysis

Ti-doped Ni-based solder was used as the repair agent to recover the flexural performance of the damaged carbon/carbon (C/C) composites. The effects of the contents of Ti on the microstructure, chemical compositions, and flexural strength were investigated. The thermal stress distribution and repair mechanism was studied by finite element analysis methods. The addition of an appropriate amount of Ti enhanced the wetting performance of the repair agent on the surface of C/C composites. Besides, the TiC hard particles formed at the interface provided strengthen effect, and form a gradient structure of coefficient of thermal expansion (CTE), thereby enhancing the interface bonding ability and improving the flexural performance of the repaired C/C composites. The flexural strength was the highest with a recovery rate of 92.6 % when the content of Ti was 5 wt%. This work provides a strategy for the engineering application and improving the damage repair of C/C composites.

Slope stability analysis of unsaturated colluvial slopes based on case studies of rainfall-induced landslides

Landslides in colluvial soils under rainfall have been identified as a significant problem due to their loose, heterogeneous nature and low shear strength. Evaluation of the stability of colluvial slopes under rainfall conditions is challenging. This study investigated two landslide failure case studies of colluvial soils to understand the failure patterns using finite element (FE) and limit equilibrium (LE) slope stability analysis methods under unsaturated conditions. Transient seepage conditions due to rainfall infiltration and failure were analysed using hydromechanical models. Here, a FE fully coupled hydromechanical model and a sequential coupling of a FE hydrological and LE mechanical model were used to evaluate the failure of variably saturated slopes. Results from the case studies revealed that the failure occurred due to the rise in the groundwater table in both cases. It was evident that there can be significant disparities in the pore water pressure profiles with the fully coupled and sequentially coupled analysis. The dynamic capability of the two models can also affect the interplay between the hydrological and mechanical aspects. When the thickness of the colluvium layer is large, the failure could potentially occur as a deep-seated failure along the boundary of overburden and the bedrock surface due to the large driving force. However, when the thickness is small, failure can occur along the colluvium-weathered rock surface. The outcomes from the study will contribute to mitigate the uncertainty of failure prediction of landslides in colluvial soils.

Analysis of divergence-preserving unfitted finite element methods for the mixed Poisson problem

In this paper we present a new H ( div ) H(\operatorname {div}) -conforming unfitted finite element method for the mixed Poisson problem which is robust in the cut configuration and preserves conservation properties of body-fitted finite element methods. The key is to formulate the divergence-constraint on the active mesh, instead of the physical domain, in order to obtain robustness with respect to cut configurations without the need for a stabilization that pollutes the mass balance. This change in the formulation results in a slight inconsistency, but does not affect the accuracy of the flux variable. By applying post-processings for the scalar variable, in virtue of classical local post-processings in body-fitted methods, we retain optimal convergence rates for both variables and even the superconvergence after post-processing of the scalar variable. We present the method and perform a rigorous a priori error analysis of the method and discuss several variants and extensions. Numerical experiments confirm the theoretical results.

Applicability evaluation technology for steel small diameter pipes containing external surface corrosion defects

With the continuous operation of oil and gas stations and petrochemical equipment, it has been found that steel small bore pipelines have different degrees of corrosion defects, which have led to pipeline cracking and medium leakage, and have increasingly attracted great attention of their oil and gas and chemical enterprises. In order to ensure the safe operation of the small diameter pipes with external surface corrosion defects, the influence law of the size of corrosion defects on the bearing capacity of the small diameter pipes were studied by finite element analysis and test simulation method, and the damage mechanism and failure form were analyzed, and the failure pressure prediction formula of the small diameter pipes with defects was fitted. It provides technical guidance for the applicability evaluation of corrosion-containing steel small diameter pipes in oil and gas chemical stations or installations.

An improved approach to compensating for cure‐induced deformation to manufacture composite aircraft skin accurately

AbstractThe purpose of this paper is to compensate for the cure‐induced deformation to manufacture composite aircraft skin with variable curvature accurately. Firstly, a finite element analysis (FEA) method appropriate for curing simulation was described. Then, the discrete curvature‐based displacement adjustment (DC‐DA) method for mold surface compensation was proposed. The DC‐DA method utilizes the discrete curvature of the section points to obtain a smooth compensated curve. Finally, a skin part was selected to prove its effectiveness. The experimental results showed that after the mold's surface was modified by the DC‐DA method with the FEA‐predicting deformation as input, the forming shape could meet the requirement of the part accuracy in one cycle. The DC‐DA method was also compared with the displacement adjustment (DA) method and proved to be more efficient for the compensation of composite skin with variable curvature.Highlights The FEA is appropriate for the calculation of the skin's curing deformation. The DC‐DA method is efficient for compensating for the skin's deformation. The shape of the case part could meet the requirement of accuracy in one cycle.