Finite Element Simulation Study Research Articles

Enhanced energy storage performance in Pb-free Na0.5Bi0.5TiO3–Sr0.7Bi0.2TiO3-based relaxor ferroelectric ceramics through a stepwise optimization strategy

This study employed a stepwise optimization strategy, including doping Sr(Ga0.5Nb0.5)O3 (SGN) into 0.65Na0.5Bi0.5TiO3-0.35Sr0.7Bi0.2TiO3 (NBT-SBT) ceramics to modify the composition and a further processing improvement. By introducing Ga3+ and Nb5+ ions with high ionic polarization rates into the B-site, the average polarization of the unit cell was maintained while further inducing local disordered fields and promoting polar nanoregions. The high activity of the polar nanoregions was confirmed using piezoelectric microscopy. The effective energy storage density (Wrec) of 2.73 J/cm³ was obtained when the SGN doping was 6.5 %. Subsequently, the densification of ceramics was improved through viscous polymer processing, thereby enhancing the breakdown strength (BDS). A combined approach of finite element simulation and experimental studies was further utilized to investigate the impact of grain size on the BDS. The stepwise optimization strategy enabled the NBT-SBT-6.5SGNVPP ceramics to achieve the Wrec of 5.2 J/cm3 and efficiency (η) of 85 % under 350 kV/cm. Additionally, the ceramics developed by this strategy possess excellent temperature and frequency stability and pulse discharge performance, making them potential candidates for practical applications.

Design, analysis, and experimental investigations of an asymmetrical under-actuated micro-gripper

In this paper, we present a new asymmetrical under-actuated micro-gripper which can perform twisting and gripping operation to the target simultaneously actuated by a single piezoelectric actuator. Two improved hybrid amplification mechanisms were designed integrated with three different flexure hinges to enhance dynamic performances. Kinematics and dynamics models of the micro-gripper including input stiffness, displacement amplification ratio, and natural frequency based on pseudo-rigid-body method and Lagrange’s equations were derived. Proposed models were evaluated by finite element simulation studies. Experimental results shown that our designed micro-gripper possesses good performance in terms of clamping reliability and dynamic response.

Experimental and finite element simulation studies of the bio-tribological behavior of L-PBF Ti-6Al-4V alloys with various surface roughness

Recently, 3D-printed Ti-6Al-4 V alloys have been gradually used for medical implants, where surface quality plays a crucial role in bio-tribological resistance. In this study, we designed three Ti-6Al-4 V samples through mechanical grinding, polishing, and sandblasting to explore the effect of surface roughness on the bio-tribological behavior against the Si3N4 counter-ball in a simulated body fluid (SBF) solution. Results indicate an increasing trend in the bio-tribological properties with decreasing surface roughness, with the polished sample exhibiting the lowest wear rate (2.73 × 10−3 mm3/N·m) and superior bio-tribological resistance. Finite element simulation reveals that asperities on the rougher surface sample lead to stress concentration, forming larger asperity fragments, enhancing mechanical interlocking and thus intensifying wear. Additionally, with increasing surface roughness, the wear mechanism of the as-printed Ti-6Al-4 V alloy shifts from abrasive and adhesive wear to a combination of abrasive, adhesive, and oxidative wear. This study provides valuable insights into the effect of surface roughness on the bio-tribological properties of as-printed Ti-6Al-4 V alloys, offering guidance for regulating surface quality in biomedical implants.

Magnetic hyperthermia in tissue-like media: Finite element simulation, experimental validation, parametric variations, and calibration studies

We report the experimental characterization and finite element modeling of magnetic fluid hyperthermia (MFH) in tissue-like media using tetramethyl ammonium hydroxide coated superparamagnetic iron oxide magnetic nanoparticles (MNPs) of size ∼19.6 ± 1.2 nm, prepared using a co-precipitation technique. MFH properties are probed for the MNPs in ∼1 wt. % agar, resembling the tumor and surrounding normal tissues. The field-induced temperature rise (ΔT) is experimentally measured in real-time utilizing an infrared camera. A finite element model (FEM) is utilized to simulate the spatiotemporal variations in the thermal profiles, which are found to be in good agreement with the experimental data. FEM-based parametric studies reveal that the thermal conductivity of the medium is the most significant parameter influencing the thermal profiles. The spatiotemporal variations in the thermal profiles are numerically studied for seven different tissues, and the obtained results indicate the highest ΔT for the breast tissue in the tumor and the surrounding regions, which is due to the lowest volumetric specific heat and the highest thermal conductivity of the breast tissue, respectively. Numerical studies on the thermal profiles for sub-surface tumors with parametrically varying depths indicate a strong exponential correlation between the surface and tumor temperature, where the regression coefficients are found to be correlated with the thermo-physical properties of the tissues. The obtained findings are beneficial for developing a simplistic and easily deployable framework for a priori generation of the thermal profiles for various tissues during MFH, which is useful for appropriate planning and parameter selection for MFH-based therapy.

Kinematic analysis and bearing capacity optimization of fully decoupled two-rotation mechanisms

Abstract. The existing vehicle durability test platform has low accuracy in reproducing the road spectrum and cannot meet the demand for high-accuracy road spectrum reproduction. In order to meet the need for high accuracy in road spectrum reproduction of vehicle durability tests, this paper is based on an analysis of the factors affecting the accuracy of the test platform. From the perspective of mechanism innovation, a fully decoupled two-rotation parallel mechanism with large load-bearing capacity for vehicle durability testing is proposed in this paper. A new solution is provided to improve the road spectrum reproduction accuracy of the test platform. Based on the requirement of reproduction accuracy of a real road spectrum, inverse kinematics, velocity Jacobians, and workspaces of mechanisms are analyzed. The inverse kinematics and velocity Jacobian analysis of parallel mechanisms can lay a research foundation for the subsequent calculation of load-bearing capacity indexes. The design of the parallel mechanism is based on the performance requirements of large load capacity and complete decoupling. A new index for evaluating the global average carrying capacity of a mechanism is proposed. Based on this index and the atlas method, the dimensional parameters of the mechanism have been optimized. A finite-element simulation study is carried out, and it is proved that the optimized fully decoupled two-rotation parallel mechanism can satisfy the bearing capacity requirements of the platform test. The large load capacity and fully decoupled mechanism proposed in the research work of this paper can improve the road spectrum reproduction accuracy of the vehicle durability test platform and has good application prospects in the field of vehicle durability tests.

Effects of different contact angles during forefoot running on the stresses of the foot bones: a finite element simulation study.

Introduction: The purpose of this study was to compare the changes in foot at different sole-ground contact angles during forefoot running. This study tried to help forefoot runners better control and improve their technical movements by comparing different sole-ground contact angles. Methods: A male participant of Chinese ethnicity was enlisted for the present study, with a recorded age of 25years, a height of 183cm, and a body weight of 80kg. This study focused on forefoot strike patterns through FE analysis. Results: It can be seen that the peak von Mises stress of M1-5 (Metatarsal) of a (Contact angle: 9.54) is greater than that of b (Contact angle: 7.58) and c (Contact angle: 5.62) in the three cases. On the contrary, the peak von Mises stress of MC (Medial Cuneiform), IC (Intermediate Cuneiform), LC (Lateral Cuneiform), C (Cuboid), N (Navicular), T (Tarsal) in three different cases is opposite, and the peak von Mises stress of c is greater than that of a and b. The peak von Mises stress of b is between a and c. Conclusion: This study found that a reduced sole-ground contact angle may reduce metatarsal stress fractures. Further, a small sole-ground contact angle may not increase ankle joint injury risk during forefoot running. Hence, given the specialized nature of the running shoes designed for forefoot runners, it is plausible that this study may offer novel insights to guide their athletic pursuits.

Finite element simulation and experimental study of non-blank holder forward and backward composite deep drawing earing test

Finite element simulation and experimental study of non-blank holder forward and backward composite deep drawing earing test

An acoustic cloaking design considering flow effects by using topology optimization

A topology optimization method is utilized to design an acoustic cloak in the presence of background mean flows, highlighting both the scientific significance and practical importance of acoustic invisibility in fluids. This study focuses on understanding the inherent physical mechanism and considering realistic constraints for actual manufacturing, ultimately inspiring the development of an optimized cloak that is available for practical fabrication in the presence of flows. Here, we use the density-based topology optimization to assign specified materials and impose practical constraints on the material allocation to achieve the desired cloaking performance. The optimization problem is then efficiently solved using the gradient-based globally convergent method of moving asymptotes, leveraging the derivative information from the finite element simulation studies of the linearized acoustic potential equation. To validate the proposed method, several numerical simulations are conducted, exploring different frequencies, incident flow speeds, and incident angles of flow. The results confirm the effectiveness and efficiency of the optimization method, expanding the range of applications of the acoustic cloak and contributing to a deepened physical understanding of how it manipulates sound waves in flows.

Simulation of low-energy impacts on the human hand for prediction of peak reaction forces and bone fracture

Hands of workers in extractive and heavy-duty industries are susceptible to suffering injuries of varying severity. Improved safety procedures and new technologies for production and maintenance tasks have contributed to reducing the severity of injuries. However, manual tasks with high-risk factors can still lead to hand injuries. Hand bone fractures and dislocations can be caused by relatively small objects impacting a region of the hand at velocities in the range of 1.3 to 1.6 m per second. This impact can produce significant functional, physical, and psychological consequences in those affected and result in high costs derived from medical care. This study presents the results of a finite element simulation study conducted to reproduce impacts with energies in the range of 7 to 10 Joules of an object on the dorsal region of the hand. Simulation results are compared to previous experimental results obtained from controlled impact tests performed using cadaveric hand specimens. The vertical peak reaction force (PRF) as a function of the impact position was used as a primary outcome for comparisons. Simulation results for all impact positions were within the standard deviation measured experimentally, with differences in the PRF values in the range of −5.3% to 4.9%. Bone stress analyses at the position of impacts showed the locations where the maximum principal stress exceeded the bone strength, as well as the variability in the correspondence between the stress distribution predicted by the FE models and the fracture rate distribution observed experimentally.

Finite element simulation and experimental study of selective laser melted 40Cr steel forming process

Selective Laser Melting (SLM) is a novel manufacturing method of complex metal parts. 40Cr is a traditional steel with low cost and high strength, and has wide application. However, the process parameters for the selective laser melted 40Cr steel have not yet been developed. In this paper, based on ANSYS finite element analysis results of the molten pool size and experiments, the optimal parameter of selective laser melted 40Cr was developed and maximum relative density of the fabricated samples was up to 99.34%, when the laser power was 285 W and the scanning speed was 960 mm/s. It was found that the sample consisted of α-Fe phase and a small quantity of γ-Fe retained austenite phase. The microstructure of the specimen was mainly composed of lath martensite, granular bainite and lower bainite. The microstructure of the specimen was mainly composed of lath martensite, granular bainite and lower bainite. Hardness, tensile strength, yield strength and elongation of the sample with maximum relative density reached to 430HV, 1467.75 MPa and 1298.82 MPa and 25.26% respectively. The mechanical properties of SLMed 40Cr steel is superior to that of 40Cr specimens made by other manufacturing methods, such as casting, electropulsing quenching, etc.

Finite element simulation study on vertical bearing characteristics of single pile with ram-compacted bearing sphere.

The pile with ram-compacted bearing sphere (PRBS)is a kind of special-shaped pile, the calculation formula of single pile bearing capacity stipulated in Chinese Standards JGJ/T 135-2018 is relatively simple, and the factors considered are not comprehensive enough. This article uses the finite element simulation software ABAQUS to simulate and calculate the compressive bearing characteristics of PRBS, and studies the changes in the vertical bearing characteristics of PRBS under different factors and working conditions (different pile lengths, pile diameters, and the diameters of ram-compacted bearing sphere (RBS)). The calculation results indicate that the PRBS still has a large axial force near the enlarged end of the pile bottom, and the RBS bears a large load. The vertical bearing capacity of the PRBS is mainly provided by the RBS, but the pile side friction still has a certain degree of influence on its bearing capacity. The maximum ratio of pile side frictional resistance to applied load can reach 18.41%. Compared with the ordinary pile, the bearing capacity of the PRBS is significantly improved. The ultimate bearing capacity of the PRBS with the RBS diameter of 1m is more than 5 times that of the ordinary pile under the same condition. Pile diameter has little influence on the bearing capacity of PRBS, while the change of RBS diameter has great influence on the bearing capacity of single pile. However, when the RBS diameter is too large, it is easy to cause the uplift of surrounding soil in the construction process and affect surrounding piles. Therefore, it is suggested that the optimal RBS diameter should be 800mm~1200mm. This study provides reference suggestions for the study of piles with ram-compacted bearing sphere.

Finite element simulation study on cutting coal and rock by cutting head of roadheader

In order to improve the cutting efficiency of the roadheader and address the challenge of monitoring the load of the cutting head and pick, a load simulation method was proposed using ABAQUS finite element software to simulate the cutting head at different cutting depths under various cutting conditions. According to the coal cutting test, a finite element simulation model was developed using Drucker-Prager as the constitutive model of coal to simulate the conical pick cutting of coal. The results of the finite element analysis were compared with the cutting test results, and the reliability of the former was confirmed. The study further involved establishing a model of cutting coal with different depths under various working conditions, and the torque waveform was obtained through finite element simulation. MATLAB was employed to program the theoretical formula, the theoretical waveforms of the force and torque of the cutting head were obtained. Additionally, the mean value of the cutting force of each pick in the finite element simulation results under different working conditions was statistically analyzed, and its distribution law was obtained. The results showed that the finite element simulation results were in good consistency with the theoretical calculation results, indicating that the simulation method was both reasonable and feasible for simulating the coal cutting process. Finite element simulation combined with theoretical calculation can be used in the stability control of cutting head dynamic load, and provide a basis for improving cutting efficiency.

Three-Point Bending Test and Finite Element Simulation Study of 304 Stainless Steel Based on Elastoplastic Constitutive Model

Rebar bending is commonly found in engineering and has received widespread attention. In this paper, a combination of experimental and finite element methods was used to conduct a study on three-point bending of 304 stainless steel. The real-time bending angle of the round bar during bending was recorded using a digital inclinometer. The force-displacement curves of specimens with different diameters were obtained and compared with the results of finite element simulations. Furthermore, the results from the digital inclinometer were compared with theoretical angle values. The findings suggest that the larger the diameter of the 304 stainless steel round bar, the greater the normal force it experiences. The finite element results are relatively consistent with the experimental results. The angle displayed by the digital inclinometer is consistent with the theoretical angle value of the round bar before unloading. The rebound angle of the reinforcing bar is greatly influenced by its diameter. When the diameter of the round bar exceeds a certain value, the rebound angle can be neglected.

Experimental and finite element simulation study of the mechanical behaviors of aluminum foam-filled single/double tubes

Aluminum foam-filled tubes are complicated structures created by filling one or more thin-walled metal tubes with varying shapes in cross-sections with aluminum foam. We optimized the structure of aluminum foam-filled tubes using software simulation, compression, and three-point bending experiments. Filling aluminum foam not only improves the axial compressive performance and bending strength of the thin-walled metal tube but also eliminates the disadvantage of the low strength of the aluminum foam. The aluminum foam-filled single tube exhibited significant improvements in load-bearing and energy absorption, with a one-time increase in load-bearing and five times increase in energy absorption compared with an empty tube. The aluminum foam-filled single tube with a smaller diameter-to-thickness ratio has a higher load-bearing capacity. In contrast, the length-to-diameter ratio has a lower impact on load-bearing capacity. Once the filling length reaches the effective filling length, the structure can still support higher loads and effectively reduce its overall weight. The compression and bending properties in the double-tube structure filled with foam aluminum improved significantly compared with the empty tube and single-tube structure filled with aluminum foam. The total compressive energy absorption capacity in the double-tube structure filled with aluminum foam is 2.01 times that of the empty tube and 1.81 times that in the single-tube-filled structure. When the wall thickness of the filled stainless steel tube is 1.0 mm, the total bending energy absorption and the specific absorption energy of the aluminum foam-filled double tube structure are 1.5 and 2.1 times that of the corresponding aluminum foam-filled single tube, respectively.

Microcatheter tracking in thrombectomy procedures: A finite-element simulation study

Background and objectiveMechanical thrombectomy is a minimally invasive procedure that aims at removing the occluding thrombus from the vasculature of acute ischemic stroke patients. Thrombectomy success and failure can be studied using in-silico thrombectomy models. Such models require realistic modeling steps to be effective. We here present a new approach to model microcatheter tracking during thrombectomy. MethodsFor 3 patient-specific vessel geometries, we performed finite-element simulations of the microcatheter tracking (1) following the vessel centerline (centerline method) and (2) as a one-step insertion simulation, where the microcatheter tip was advanced along the vessel centerline while its body was free to interact with the vessel wall (tip-dragging method). Qualitative validation of the two tracking methods was performed with the patient's digital subtraction angiography (DSA) images. In addition, we compared simulated thrombectomy outcomes (successful vs unsuccessful thrombus retrieval) and maximum principal stresses on the thrombus between the centerline and tip-dragging method. ResultsQualitative comparison with the DSA images showed that the tip-dragging method more realistically resembles the patient-specific microcatheter-tracking scenario, where the microcatheter approaches the vessel walls. Although the simulated thrombectomy outcomes were similar in terms of thrombus retrieval, the thrombus stress fields (and the associated fragmentation of the thrombus) were strongly different between the two methods, with local differences in the maximum principal stress curves up to 84%. ConclusionsMicrocatheter positioning with respect to the vessel affects the stress fields of the thrombus during retrieval, and therefore, may influence thrombus fragmentation and retrieval in-silico thrombectomy.

Finite element simulation and experimental study of laser-generated surface acoustic waves on determining mechanical properties of thin film

The laser-generated surface acoustic wave (LSAW) nondestructive testing (NDT) technique is a promising method to characterize the mechanical properties of thin films. In this study, based on the thermoelastic mechanism, a finite element method (FEM) is put forward to simulate the LSAW in the film/substrate structure, and the effect of the temporal and spatial distribution of the Gaussian pulse laser on the Rayleigh-type SAW signals is revealed. For the SiO2 and low dielectric constant (low-k) dense Black Diamond™ (SiOC:H, BD) films with the thickness of 500 and 1000 nm, the typical displacement waveforms of SAW at a series of probing points along the propagation direction are obtained. By analyzing the full width at half maximum (FWHM) of the signal, the optimal NDT experimental conditions for laser are determined with the minimum possible pulse rising time and the linewidth less than 10 μm. Based on the FEM simulation result, the LSAW NDT experiment is carried out and the dispersion curve of SAW is calculated to characterize Young's modulus of the SiO2 and low-k samples. It is found that the experimental results are in good agreement with the simulation results. This study verifies the validity of FEM simulation of LSAW in layered structures containing thin film and that the laser parameters determined by FEM fit perfectly in characterizing the mechanical properties of thin films.

Nozzle Geometry and Particle Size Influence on the Behavior of Low Pressure Cold Sprayed Hydroxyapatite Particles

Low-pressure cold spray (LPCS) technology has attracted interest for the deposition of ceramic coatings due to the thermo-kinetic conditions experienced by the sprayed particles. Unlike conventional thermal spray techniques, the spraying conditions in LPCS can be controlled to avoid the formation of undesired phases. However, ceramics deposition through this process is still challenging. The present study includes a finite element analysis and simulation study of the kinetic conditions of ceramic particles in the LPCS process based on experimental data. The analysis seeks to discuss the effect of nozzle geometry on the kinetic and thermal energy of the sprayed particles at impact and elucidate how the particle travels within the high-velocity jet to be deposited onto a metallic surface. This work examines the behavior of hydroxyapatite particles as a function of particle size and nozzle geometry during LPCS deposition. Interestingly, the results from this research suggest that particle size and nozzle geometry have an influence on the deposition of hydroxyapatite particles. Inertia of large particles proved to be beneficial in keeping their trajectories, allowing them to contribute to the formation of the coatings. Nozzle geometry modifications produced changes in the jet profile and affected the homogeneity of the coatings obtained. This finding contributes to a better understanding of the deposition of hydroxyapatite particles by cold spraying.

Experimental and finite element investigation of precision multi-grain grinding of pure titanium

Pure titanium composed of α single-phase has important applications for its excellent mechanical, physical, and chemical properties, which also impose high requirements on its surface finish. However, pure titanium is a difficult-to-machine material due to its low mass transportation caused by the low stiffness and the low thermal conductivity. Thus, it is greatly needed to investigate the machinability of pure titanium by precision grinding. In the present work, we carry out experimental and finite element simulation studies on the precision multi-grain grinding of pure titanium. Specifically, finite element model of pure titanium grinding using grinding wheel with multiple grains is established, which enables the prediction of successive material removal behavior by neighboring grains in line with experiments. The machining behavior of pure titanium and its correlation with machined surface morphology and grinding force are studied by experiment, and are further revealed by finite element simulation. Subsequent grinding experiments are performed to study the effects of workpiece speed and grinding depth on the ground surface quality of pure titanium, with which a surface roughness of 0.27 μm is obtained under the optimized grinding parameters.

Characteristics and application of present in situ stress field of a strike-slip fault: a 3D finite-element simulation study

AbstractPrevious hydrocarbon explorations in the middle of the Tarim Basin indicate that strike-slip faults play an important role in the development of Ordovician carbonate reservoirs and hydrocarbon accumulation. The SB5 fault in the Tarim Basin was the target of this investigation. An evaluation of the stress in situ was carried out and provided boundary conditions to build a 3D geomechanical model. The distribution and application of present in situ stress in the strike-slip fault were studied. The results show good agreement between the absolute measured stress in situ and the modelled stresses, revealing a different stress regime along the strike-slip fault. The uplift segment belongs to a strike-slip stress state, and other areas belong to a normal fault stress state. The strike-slip fault has a significant influence on the present in situ stress distribution. The direction of the maximum horizontal stress deflects near the fault and tends to be parallel to the fault strike. This work introduces a comprehensive evaluation of the present in situ stress of the fractured carbonate reservoirs controlled by the strike-slip fault system. The present in situ stress direction can clarify the propagation direction of hydraulic fracturing and serve to evaluate the effectiveness of natural fractures.

Stability of internal fixation systems based on different subtypes of Schatzker II fracture of the tibial plateau: A finite element analysis.

Background: Schaztker II fracture is the most common type of the tibial plateau fractures (TPF). There has been a large number of cadaveric biomechanical studies and finite element simulation studies to explore the most stable fixation methods for this type of fracture, which were based on a single fracture morphology. But differences among fracture morphologies could directly affect the stability of internal fixation systems. In this sense, we verified the stability of existing internal fixation modalities by simulating Schatzker II fractures with different fracture morphologies. Objectives: To compare the stability of different filler types combined with locked compression plate/screw in different subtypes of Schatzker II TPF. Methods: Four subtypes of Schatzker II were created based on 3D map of TPF. Each of the subtypes was fixed with LCP/screw or LCP/screw combined with different fill types. Stress distribution, displacement distribution, and the load sharing capacity of the filler were assessed by applying the maximum load during gait. In addition, repeated fracture risks of depressed fragment were evaluated regarding to the ultimate strain of bone. Results: The stress concentration of the implant in each scenario was located on the screw at the contact site between the plate and the screw, and the filler of the defect site significantly reduced the stress concentration of the implant (Subtype A: Blank group 402.0 MPa vs. Experimental group 315.2 ± 5.5 MPa; Subtype C: Blank group 385.0 MPa vs. Experimental group 322.7 ± 12.1 MPa). Displacement field analysis showed that filler significantly reduced the reduction loss of the depressed fragment (Subtype A: Blank group 0.1949 mm vs. Experimental group 0.174 ± 0.001 mm; Subtype C: 0.264 mm vs. 0.253 ± 0.002 mm). Maximum strain was in subtype C with the value of 2.3% ± 0.1% indicating the greatest possibility of failure risk. And with the increase of its modulus, the bearing capacity of filler increased. Conclusion: The existence of filler at the defect site can effectively reduce the stress concentration of the implant and the reduction loss of the collapsed block, thus providing good stability for Schatzker II fracture. In subtype A fracture, the modulus of filler presented the slightest influence on the stability, followed by subtype C, while the stability of subtype B was most influenced by the modulus of filler. Therefore, it is necessary to evaluate the preoperative patient imaging data adequately to select the appropriate stiffness of the filler.