Detailed Finite Element Analysis Research Articles

Effect of high-strength spirals on eccentric compression behavior of square CFST columns

In this study, the eccentric compressive performance of square CFST columns with high-strength internal spirals (HSS) was systematically investigated. First, an eccentric compression test was conducted on spiral-confined CFST columns with influential parameters of yield strength and pitch of the steel spiral and load eccentricity. It was found that the strength and ductility of square CFST columns were significantly improved by incorporating the contribution of the confined HSS. The improvements were more pronounced for columns with lower load eccentricity ratios. Subsequently, detailed finite element analyses were conducted to investigate the performance and mechanisms of the HSS-CFST columns, i.e., the distributions of axial stress and confining pressure of concrete, the interaction between concrete and steel tube, and load versus deformation responses. It was observed that the internal spirals could not only enhance the axial stress of the concrete they confined but also improve the interaction between the concrete and steel tube. Moreover, a parametric study was performed to investigate the influence of confined steel spiral layouts on the mechanical performance of HSS-CFST columns. Decreasing the steel spiral pitch improved the strength and ductility of square CFST columns more effectively than increasing the diameter of the steel spiral. Finally, design recommendations for eccentrically loaded spiral-confined square CFST columns are provided.

Investigation of cyclic behavior of full-scale tree-like hollow structural section columns with infilled concrete

The cyclic behavior of tree-like hollow structural section (HSS) columns with infilled concrete was experimentally and numerically investigated. A full-scale column, with the height of 3.7 m and the treetop plan dimension of 4 m × 3 m, was designed and manufactured according to a practical engineering prototype. The column was composed of a petal-shaped trunk using a concrete-filled steel tubular (CFST) section, four primary branches using a circular CFST section, and twelve secondary branches using a circular HSS. The column with a capacity protected reinforced concrete foundation was tested under combined constant axial compression and cyclic lateral loading through a specifically designed setup. The cracking and spalling of the reinforced concrete foundation were observed initially, followed by yielding of the bottom end of the primary branches when the story drift ratio reached 1.00%. The specimen failed by fracture of the full penetration groove welded splices in the petal-shaped trunk embedded in the foundation when the story drift ratio reached 3.00%. A detailed finite element analysis model for the tree-like column was then established and verified. Parametric studies were conducted to investigate the influence of the axial load level (0.016–0.3), filling range of concrete (including no filling, partial filling, and overall filling), steel yield strength (235–460 MPa), and the height to width ratio of the petal-shaped trunk (0.75–3.14). The results showed that the higher the filling height of concrete was, the greater the lateral load-carrying capacity and stiffness of the specimen were, but the filling height after reaching the secondary branches hardly affected the mechanical properties of the specimen. With the increase of the axial load level, the load-carrying capacity and deformation capacity decreased. Both the filling range and the height to width ratio of the petal-shaped trunk could change the failure mode of the tree-like column. Finally, some design considerations were proposed.

Size effects and failure regimes in notched micro-cantilever beam fracture

Fracture tests using notched micro-cantilever (MC) specimens are increasingly being used to measure the fracture toughness of materials at the micro-scale. Detailed finite element analyses (FEAs) of loading of self-similar micro- and bulk cantilever beam fracture specimens using isotropic, elastoplastic constitutive models, are conducted to critically examine the validity of the toughness data obtained using MC specimens. From the simulated normalized load versus load point displacement and the corresponding normalized energy release rate versus load curves, the transition of the failure regimes from crack propagation to plastic collapse of the uncracked notch ligament are identified. While the crack propagation regime allows for the estimation of valid fracture toughness of the probed material, the plastic collapse regime does not. The effects of specimen aspect ratios, material hardening, and yield criteria on the master curves and transition point are examined. A method to interpret the failure regimes, assess the validity and size effects in micro-cantilever fracture tests is proposed. An expression is derived for the minimum size requirements of MC fracture specimens in order to get a valid fracture test. The data reported in the literature from fracture tests on bulk metallic glasses, nano-crystalline materials and ultra-fine grained materials are assessed using the proposed methodology. The present work has important implications for specimen design, interpretation of failure regimes, and potential size effects in MC fracture tests.

Estimating thin-film thermal conductivity by optical pump thermoreflectance imaging and finite element analysis

We introduce a noncontact experiment method to estimate thermal conductivity of nanoscale thin films by fitting high spatial resolution thermoreflectance images of surface spot heating to a finite element simulated temperature distribution. The thin-film top surface is heated by a 1μm diameter focused, 825 nm wavelength laser spot. The surface temperature distribution in the excited sample is imaged by thermoreflectance microscopy with submicrometer spatial resolution and up to 10 mK temperature resolution. Thin-film thermal conductivity is extracted by fitting a measured surface temperature distribution to a 3D finite element temperature model. The method is demonstrated by estimating thermal conductivity for an isotropic thin-film metal (nickel, 60–260 nm) on a glass substrate. The fitted Ni thermal conductivity was 50 ± 5 W/m K, which is in good agreement with the literature. Also, we present a detailed finite element analysis for an anisotropic thin-film semiconductor sample to show how the method could be extended to estimate thermal conductivity of anisotropic thin films. Advantages of the new method are easy sample preparation (no top surface transducer film or integrated heater required), rapid in situ measurement, and application to a broad range of thin-film materials.

Performance of steel beams with replaceable buckling restrained fuses under cyclic loading

A new type of steel beam system with replaceable buckling restrained fuses was proposed. The replaceable fuse consists of flange connecting plates and web connecting plates as energy dissipation devices, and cover plates to prevent local buckling of the fuses. A total of seven specimens were tested to investigate the influence of cover plates and moment capacity ratio of fuses followed by a detailed finite element analysis to evaluate the performance of specimens at higher drift levels. The tests results showed that the specimens with buckling restrained fuses exhibited stable hysteretic behavior without experiencing strength degradation. Multi-wave buckling instead of first mode buckling was observed in the flanges connecting plates up to 4% drift. The seismic performance before and after the replacement of the damaged fuses was almost identical which indicated the seismic resilient ability of the proposed steel beam system. The strength and failure mode of the steel beam system was mainly controlled by the moment capacity ratio of fuses, and a limiting moment capacity ratio of 0.69 was recommended to remain the beam segments in elastic state with the maximum drift of 6%. Further, an idealized load-displacement relationship was established which can be adopted in the design of the proposed beams.

Development of composite cold-formed steel-rubberised concrete semi-rigid moment-resisting connections

This paper presents the development of a composite cold-formed steel (CFS)-rubberised concrete (RuC) semi-rigid moment-resisting connection suitable for framed building structures. The connection comprises built-up tubular cold-formed steel beam and column sections connected using side-plate screwed fasteners and infilled with rubberised concrete. A detailed finite element analysis validated against physical tests is employed to model both bare steel and composite beam-to-column connections subjected to lateral and gravity loadings. The governing design limit states are characterized as local buckling in bare steel beams, connection screw shear failure, and side plate plasticity. It is shown that the strength and ductility capacity of composite connections could be increased by up to 1.44 and 3.46 times, respectively, compared with those of the bare steel connections. The connection rigidity of both bare steel and composite connections can be classified as a semi-rigid joint.

Assessment of the tensile behaviour of post-installed screw anchors in early age concrete

This study investigates the tensile behaviour of post-installed screw anchors in early-age concrete. The investigation included an experimental study including testing of 38 screw anchors at 6 different hydration ages. The experimental program aimed to investigate: (i) the effect of early-age installation on the 28 day behaviour; (ii) and performance when screw anchors are installed and tested in early-age concrete. The experimental results demonstrated the capability of the concrete capacity method model in capturing the behaviour of screw anchors in early-age concrete with reasonable accuracy. Further, early-age installation of screw anchors did not impact the performance of the anchors when tested in tension at 28 days. This study also included a detailed finite element analysis of screw anchors in early-age concrete to further understand the behaviour of this type of anchors and the failure mechanism governing the capacity under pure tension loading.

FINITE ELEMENT ANALYSIS OF FEMORAL PROSTHESIS UNDER TRANSIENT LOADING FOR MULTIPLE ACTIVITIES OF DAILY LIVING

The femoral prostheses experience versatile loading during the activities of daily living (ADL) and subsequently encounter a variety of stresses. This paper presents a detailed finite element analysis (FEA) of the femoral implant under transient loading. The distinct loading patterns corresponding to the most commonly occurring ADL are utilized for simulating the different scenarios. The CT reconstructed CAD model of the human femur bone assembled with a femoral implant is utilized for this study. The loading scenarios for walking, stair ascent, stair descent, standing up, sitting down, standing on one leg and knee bending are simulated by using the joint reaction forces and moments, corresponding to a body weight of 750 N, for the FEA. The results of this study are validated using a preliminary in-house built experimental setup comprising a fixture for a stainless steel femoral implant with sensors attached at three locations on the implant. The results indicate that the highest stresses are generated in case of the stair descent, stair ascent and standing on a single leg type of activities. These activities that generate high stresses on the implant surfaces are not suitable for the longevity of the implant and are therefore not advisable for post-operative patients.

Validation and Parametric Investigations of an Internal Permanent Magnet Motor Using a Lumped Parameter Thermal Model

Abstract One of the key challenges for the electric vehicle industry is to develop high-power-density electric motors. Achieving higher power density requires efficient heat removal from inside the motor. In order to improve thermal management, a multiphysics modeling framework that is able to accurately predict the behavior of the motor, while being computationally efficient, is essential. This paper first presents a detailed validation of a lumped parameter thermal network (LPTN) model of an Internal Permanent Magnet synchronous motor within the commercially available motor-cad modeling environment. The validation is based on temperature comparison with experimental data and with more detailed finite element analysis (FEA). All critical input parameters of the LPTN are considered in detail for each layer of the stator, especially the contact resistances between the impregnation, liner, laminations, and housing. Finally, a sensitivity analysis for each of the critical input parameters is provided. A maximum difference of 4%—for the highest temperature in the slot-winding and the end-winding—was found between the LPTN and the experimental data. Comparing the results from the LPTN and the FEA model, the maximum difference was 2% for the highest temperature in the slot-winding and end-winding. As for the LPTN sensitivity analysis, the thermal parameter with the highest sensitivity was found to be the liner-to-lamination contact resistance.

Analytical and Experimental Investigation into Pre-Stressed Carbon Fiber Reinforced Polymer (CFRP) Fatigue Retrofits for Steel Waterway Lock-Gate Structures

Lock gates are an important part of the transportation infrastructure within the United States (US). Unfortunately, many existing lock gates have reached or exceeded their initial design lives and require frequent repairs to remain in service. Unscheduled repairs often increase as gates age, having a local economic impact on freight transport, which can create economic ripples throughout the nation. Metal fatigue is a key cause of unscheduled service interruptions, degrading lock gate components over time. Additionally, because lock gates are submerged during operation, crack detection prior to component failure can be difficult, and repair costs can be high. This paper presents an analytical and experimental investigation into fatigue damage within common lock gate geometries, as well as fatigue mitigation strategies with a focus on extending gate service lives. Detailed finite element analyses are combined with fatigue and fracture mechanics theories to predict critical fatigue regions within common gate details and develop retrofit strategies for mitigating fatigue cracking. Full-scale experimental fatigue testing of a critical lock gate component is conducted to provide a baseline for the evaluation of retrofit strategies. Retrofit strategies and issues in using carbon fiber reinforced polymer (CFRP) plates having optimized pre-stress levels are discussed.

A Quantitative Weld Sizing Criterion and Applications in Load Capacity Evaluation of Hollow Structural Section Joints

Existing weld sizing procedures for hollow structural section (HSS) connections in Codes and Standards are empirical in nature, often resulting in oversized welds. There is a growing interest in quantitative weld sizing for ensuring both structural safety and cost-effective construction of lightweight hollow section structures. In this study, a mesh-insensitive traction stress method is introduced for evaluating strength of fillet-welded HSS joints. The results are then generalized into a closed-form expression with a clearly defined mechanics basis. This expression relates weld throat shear stress to fillet weld size and remote load, with its dimensional geometric parameters being determined through a detailed parametric finite element analysis (FEA) of circular hollow section (CHS) and rectangular hollow section (RHS) connections with various dimensions. The effectiveness of the closed-form expression is demonstrated by comparing the predicted failure loads with those measured from a large number of HSS test data available from literature. Furthermore, the proposed quantitative weld sizing criterion can lead to as much as 20% weld size reduction from those determined using existing empirical-based weld sizing criteria, which can be very beneficial for welding-induced distortion control in construction of lightweight thin-walled structures.

Finite element analysis of the performance of additively manufactured scaffolds for scapholunate ligament reconstruction.

Rupture of the scapholunate interosseous ligament can cause the dissociation of scaphoid and lunate bones, resulting in impaired wrist function. Current treatments (e.g., tendon-based surgical reconstruction, screw-based fixation, fusion, or carpectomy) may restore wrist stability, but do not address regeneration of the ruptured ligament, and may result in wrist functional limitations and osteoarthritis. Recently a novel multiphasic bone-ligament-bone scaffold was proposed, which aims to reconstruct the ruptured ligament, and which can be 3D-printed using medical-grade polycaprolactone. This scaffold is composed of a central ligament-scaffold section and features a bone attachment terminal at either end. Since the ligament-scaffold is the primary load bearing structure during physiological wrist motion, its geometry, mechanical properties, and the surgical placement of the scaffold are critical for performance optimisation. This study presents a patient-specific computational biomechanical evaluation of the effect of scaffold length, and positioning of the bone attachment sites. Through segmentation and image processing of medical image data for natural wrist motion, detailed 3D geometries as well as patient-specific physiological wrist motion could be derived. This data formed the input for detailed finite element analysis, enabling computational of scaffold stress and strain distributions, which are key predictors of scaffold structural integrity. The computational analysis demonstrated that longer scaffolds present reduced peak scaffold stresses and a more homogeneous stress state compared to shorter scaffolds. Furthermore, it was found that scaffolds attached at proximal sites experience lower stresses than those attached at distal sites. However, scaffold length, rather than bone terminal location, most strongly influences peak stress. For each scaffold terminal placement configuration, a basic metric was computed indicative of bone fracture risk. This metric was the minimum distance from the bone surface to the internal scaffold bone terminal. Analysis of this minimum bone thickness data confirmed further optimisation of terminal locations is warranted.

The bond stress-slip full curve equation between the RAC and H-shaped: Experimental, theoretical and numerical simulation investigation

The steel reinforced recycled aggregate concrete (SRRAC) is a kind of composite building material, and the bond performance at the interface determine the mechanical properties of the composite material. The purpose of this paper is to explore the bond performance of SRRAC. First, 43 SRRAC push-out specimens were made, and push-out tests were conducted on them. It was found that the failure process has gone through four stages. The failure patterns were found by analyzing all cracks, and the mechanism of the cracks was analyzed from the mechanical level. The basic model of load-slip curve was proposed. Secondly, the basic model of bond stress-slip curve was proposed, which was divided into four segments by three key points. The bond strength and slip of the three key points were respectively defined, and their respective calculation formulas were obtained through statistical analysis methods, which were verified by the test. Then, this paper proposed the bond stress-slip full curve equation, which was well verified by the test. Finally, detailed finite element analysis was carried out on SRRAC specimens, and the reliability of the model and the bond stress-slip full curve equation was further verified by the test.

A hybrid experimental and numerical technique for evaluating residual strains/stresses in bonded lap joints

This paper investigates the processing-induced residual strains developed in the adhesive layer of a single lap joint consisting of glass-fiber reinforced polymer (GFRP) adherends bonded with a thermoplastic adhesive , Acrylonitrile Butadiene Styrene (ABS). High-resolution optical fiber sensors were embedded inside the adhesive for in-situ monitoring of strains and temperature during the processing and cooling cycle. The experimental fiber-optic strains are the total strains experienced by the fiber and do not represent the strains in the adhesive because of interfacial effects between the fiber and the adhesive. Hence, a detailed finite element analysis (FEA) model was developed that included the optical fiber within the bondline . The experimentally measured optical fiber strains were first used to calibrate the FE models at each cooling rate. These FE models were then used to predict residual strains and stresses in the bulk adhesive . The FE models showed that the strains calculated along the optical fiber provided a close approximation to the actual strains experienced by the ABS adhesive around it at the center of the overlap region. The experimental technique, with appropriate post-processing, can be used to get a reliable first-hand approximation of the residual strains induced in the bulk adhesive during curing/processing. A critical conclusion from the FE investigation is that, for all cooling rate cases, the von-Mises residual stresses generated inside the bulk ABS adhesive ranged between 65 and 80% of its tensile strength , which showcases the importance of processing-induced residual stresses and their effects on safety-critical components like bonded joints. The hybrid FE-experimental approach used in this work can be extended to other joint geometries and material configurations.

Finite Element Analysis of Overlapped Z-Purlins Restrained by Sheeting

Cold-formed steel Z-purlins with overlapping at the intermediate supports ensures the continuity of the bending moment. A continuous beam with two equal spans of 6 m is investigated under gravity loading using the finite element method. The numerical model includes the beneficial interaction between the Z-purlins and the trapezoidal sheeting. Finite element results show that the screw spacing and sheeting thickness has a limited influence on the resistance of the member. The effect of the overlapping length and detailing of the connection is studied through a parametric study. Six overlaps varying from 100mm to 1200mm (1.6% to 20% of one span) capture the change of the failure mode from the overlap edge to the support region of the purlin. The connection detailing is studied considering multiple bolt/screw patterns. The detailing and length of the overlap connection has a major influence on the moment distribution and consequently on the failure mode. The detailed finite element analysis shows that assuming the beam connection as continuous in 1D beam models lead to an unrealistic bending moment distribution and failure mode. Connecting the bottom flange using screws improves the overall load carrying capacity of the beam especially for short overlap lengths. The increase in resistance is attributed to the restraining effect on the free flange which fails due to distortional buckling.

Investigation of Thermoplastic Polyurethane Finger Cushion with Magnetorheological Fluid for Soft-Rigid Gripper

This paper presents a study of penetrating a pin into a magnetorheological fluid (MR) cushion focused on the force measurement. The research is supported by detailed finite element analysis (FEA) of the magnetic field distributions in several magnetic field exciters applied to control rheological properties of the MR inside the cushion. The cushion is a part of the finger pad of the jaw soft-rigid gripper and was made of thermoplastic polyurethane (TPU) using 3D printing technology. For the pin-penetrating setup, the use of a holding electromagnet and a magnetic holder were considered and verified by simulation as well as experiment. In further simulation studies, two design solutions using permanent magnets as the source of the magnetic field in the cushion volume to control MR fluid viscosity were considered. The primary aim of the study was to analyze the potential of using an MR fluid in a cushion pad and to investigate the potential for changing its viscosity using different magnetic field sources. The analysis included magnetic field simulations and tests of pin penetration in the cushion as an imitation of object grasping. Thus, an innovative application of 3D printing and TPU to work with MR fluid is proposed.

Nonlinear finite element analysis of circular stiffened FRP-concrete-steel double-skin tubular columns (DSTCs) and experimental compressive behavior of multiple DSTC shapes

A new variation of hybrid double-skin tubular column (DSTC) consisting of concrete sandwiched between outer fibre-reinforced polymer (FRP) and inner stiffened-steel tube shows better structural performance than its unstiffened conventional form. Vertical steel stiffeners placed on the outer surface of the steel tube can potentially reduce inner tubes’ local buckling and enhance composite interactions between column components, thus resulting in improved confined concrete behavior. The present study proposes an analysis-oriented confined concrete stress–strain model for nonlinear finite element (FE) simulation of circular stiffened DSTCs. Detailed FE analyses were performed using the proposed confined concrete model for validation against documented test results of circular DSTCs with parametric stiffener geometry variations. An excellent agreement was shown between numerical and test results (at most 5% errors at critical elastic, peak and ultimate axial loads). The numerical models captured well both the elastic and post-elastic behavior of stiffened DSTCs. Finally, 14-stiffened DSTC specimens of different cross-sectional shapes, i.e., circle-circle (CC), square-circle (SC) and square-square (SS) cross-sections were tested for investigating their behavior under axial compression. Stiffened DSTCs showed significantly increased axial load capacity (up to about 32% in this study) with enhanced ductility than unstiffened specimens. The SS-shape DSTCs provided with steel stiffeners at mid-flat sides of the inner steel tube manifested relatively better performance benefits than CC and SC shapes.

Modeling and Finite Element Analysis of Chain Drive using Different Materials

In any automobile the power is transmitted from one shaft to another by using chain drive. Chain drive consists of chain, driving sprocket and driven sprocket. The driving sprocket is connected to engine output shaft, which transfer power to driven sprocket by chain. Further this driven sprocket transfer power to drive shaft. The design and material selection of this chain drive plays a vital role in efficient running of the automobile. Present the material used for chain drive is mild steel. This paper involves increases the strength of the Pulsar 180cc chain drive by selecting the different materials (AISI 1050 steel, EN 8 steel, EN 32 steel, EN 19 steel and C45 steel). In this the Pulsar 180cc chain drive designed through reverse engineering approach and detailed finite element analysis is carried out to calculate stresses and deflections on the chain drive. Later the analysis is extended to fatigue analysis to estimate the life of the chain drive and the dynamic analysis is carried out to calculate stresses and deflections on the chain drive when it is in motion. SOLID WORKS software is used for doing 3D model of chain drive and ANSYS is used for doing finite element analysis.

Compressive testing and finite element analysis-based confined concrete model for stiffened square FRP-concrete-steel double-skin tubular columns

A new variation of fibre-reinforced polymer (FRP) confined concrete-steel double-skin tubular column (DSTC) shows more promise than its traditional form when steel stiffeners are provided on the inner steel tube. Stiffeners can provide better composite action between individual DSTC components, reduce local buckling, and potentially improve confined concrete behavior. The present study performs the first-ever experimental and analytical investigation to quantify the influence of stiffened steel tube on the confined concrete behavior of square-shaped DSTCs. First, a total of 18 DSTC specimens were tested by varying the steel stiffener properties, such as quantity, configuration for the similar total stiffener-rib area, effective placement, and rib cross-section dimensions and shape. Providing stiffened steel tubes in DSTCs showed a significant increase in axial load capacity (up to about 52% in this study) with enhanced ductility than unstiffened specimens. Then the test results were used to propose an analysis-based confined concrete model for square-shaped stiffened DSTCs. Detailed finite element analyses were performed for validation study using the proposed concrete model. The numerical results showed excellent agreement with tests (about 2–4% average errors at critical elastic, peak and ultimate axial loads) and captured well both the elastic and inelastic compressive behavior of stiffened DSTCs. Finally, this study proposed a simple analytical equation for accurately estimating the peak axial load-bearing capacity of square-shaped stiffened DSTCs.

Analytical and Experimental Investigation of Elastic–Plastic Strain Distributions at 2-D Notches

Abstract Both elastic and elastic–plastic stress–strain response were studied for a series of part-circular and V-shaped notches in flat specimens. Both the peak strain at the notch root and the strain distribution along the notch bisector were studied. These quantities were determined analytically using detailed finite element analysis (FEA), and it was shown that significant differences can arise between detailed FEA results and two of the commonly used approximations for the peak notch strain response: Neuber’s rule and Glinka’s equivalent strain energy density theorem. These differences can become significant for notches with low acuity. The strain response for these configurations was also studied experimentally using two measurement techniques: optical fibers and surface differential displacement mapping. Agreement was shown between computed response strains and measured strains for some of the eight notch configurations and two aerospace alloys studied, while for others, experimental difficulties prevented agreement. These difficulties are described in detail.