FEM Numerical Simulation Research Articles

Optimizing mechanical properties and pioneering biodegradable polymer blends for superior energy-absorbing structures used in sport helmets

Replacing elements made of conventional plastics (like polystyrene) with biodegradable substitutes is part of the trend of sustainable development and waste reduction. The manuscript covers issues related to the design, manufacturing and testing of sports helmet protective inserts made of biodegradable material. The FEM numerical simulations carried out by the authors allowed to determine the optimal desirable mechanical properties (Re = 8.5–65 MPa, E = 500–8000 MPa for 30 × 30 mm inserts; Re = 10.5–60 MPa, E = 500–7500 MPa for 48 × 48 mm inserts; Re = 13–95 MPa, E = 400–8500 MPa for 55 × 55 mm inserts) and geometric parameters (wall thickness equal to 0.2–0.5 mm, height of 20 mm), ensuring the formation of a plastic fold, which is the most effective energy-absorbing mechanism. The conducted quasi-static compression, bending and dynamic tensile strength tests allowed to determine blends with appropriate proportions of durable PLA with more plastic PBAT, PBS and TPS that meet the established criteria: PLA50PBAT50, PLA30PBAT70 and PLA30TPS70.

Estimation of temperature-dependent piezoelectric material parameters using ring-shaped specimens

Abstract Simulation-driven design processes of piezoelectric actuators and sensors necessitate precise material parameter knowledge. Historically, the IEEE standard on piezoelectricity is used for this purpose, which proposes an analytical method for material parameter identification based on resonance frequency evaluations. This method requires different impedance measurements on differently shaped and processed samples, which yields inconsistent material parameter sets due to processing effects on material properties. Previous studies show that an inverse procedure using a single disc-shaped specimen with some adaptations can be used to identify a full set of parameters. As high-power actuators often use ring-shaped components, this method needs adaptation for this kind of specimen. Furthermore, the dependence of the material parameters on temperature needs to be considered to characterise the temperature effects and the associated non-linear effects of the specimens. For this purpose, samples with different geometrical dimensions at a range of different temperatures are examined in this study. Material parameters are then estimated using an inverse approach utilising the measurement data in conjunction with a numerical FEM simulation model. The observed temperature dependence of the estimated material parameters is examined and presented in this contribution.

Interfacial bond-slip of horizontally embedded CFRP strips and concrete considering the effect of the groove depth-to-width ratio

Concrete structures with shallow grooving depths require minimal adjustments to accommodate horizontal near-surface-mounted (NSM) carbon fibre-reinforced polymer (CFRP) strips. This method proves advantageous in minimizing damage to reinforced concrete structures, establishing itself as an effective reinforcement technique. To delve into the interfacial performance of the horizontal CFRP strip reinforcement, single shear pull-out testing is utilized to analyze and compare the interfacial bonding performances of concrete specimens reinforced with external bonding (EB), NSM, and horizontal NSM CFRP strips. The study also explores the influence of groove depth-to-width ratio on the interfacial bonding performance of horizontal NSM CFRP strip reinforcement. An interfacial bond-slip principal structure model of horizontal NSM CFRP strips and concrete is established, factoring in the groove depth-to-width ratio. Subsequently, the proposed interfacial bond-slip model is validated through finite element numerical simulation. The results show that the horizontal NSM CFRP strips reinforcement method exhibits commendable bonding capacity and interfacial bond stiffness. Within a specific range of groove widths, increasing the groove depth-to-width ratio diminishes the distance between the peak bond shear stress location and the loading end of the horizontal NSM CFRP strip-reinforced specimens. This improves the interfacial bonding performance between the horizontal NSM CFRP strips and concrete. The theoretical curve derived from the interfacial bond-slip principal structure model aligns well with test data across all reinforced specimens. FEM numerical simulations based on this interface bond-slip principal structure model demonstrate minor relative errors compared to experimental values. Furthermore, the theoretical distribution curve of CFRP strip strain closely follows the measured distribution curve. This model concerning the bond-slip principal structure of the interface between horizontal NSM CFRP strips and concrete, accounting for the groove depth-to-width ratio, exhibits applicability and stands as a valuable reference for practical engineering applications.

A novel variable restitution coefficient model for sphere–substrate elastoplastic contact/impact process

The restitution coefficient serves as a critical parameter to evaluate the energy loss during the contact/impact process. Its in–depth researches are beneficial to accurately describing the contact/impact phenomenon. Given the limitations of existing restitution coefficient models, a novel variable restitution coefficient model, which considers the material properties and the initial relative contacting velocity between two colliding bodies, is proposed in this work. Firstly, the function relationship between the restitution coefficient and the equivalent plastic strain can be obtained based on the energy equivalence principle. After that, multi–condition FEM numerical simulation cases are conducted to explore the mapping relationship among the equivalent plastic strain, material properties and initial relative contacting velocity, with which the new normal variable restitution coefficient model can thus be established. Finally, various comparisons with several existing restitution coefficient models are conducted to showcase its superior performance, with the low–speed experimental data and high–speed FEM results acting as reference values. Furthermore, the new restitution coefficient model is extended to describe interaction process between two spheres, and also employed for the establishment of a new continuous contact force model.

Dynamic responses of ROV system experiencing vessel heave during deployment and recovery processes

Remotely operated vehicle (ROV) system is significantly affected by the excitations coming from the top-end vessel motion and the environmental hydrodynamic forces. Especially, during initial deployment and final recovery stages, the relative motion between suspending ROV and moving top-end vessel gets more complicated and even larger. This may cause a body collision, and consequently the cable tension can also be severely changed by larger ROV motion. Sometimes, cable slack may occur, which seriously affects structural safety.To study the dynamic responses of ROV system induced by vessel heave during initial deployment and final recovery processes, the FEM numerical simulations, combining with the hydrodynamic model are conducted. Then the ROV displacement and cable tension time histories are presented. The influences of vessel motion amplitude and frequency, along with initial condition, on the dynamic responses of ROV system are also discussed. Moreover, to explore the dynamic behaviors of the ROV system further, we discuss the physical mechanisms driving response amplification through theoretical models. The governing equation of ROV system dynamics with a vertical moving boundary is established, and a dimensionless control parameter called amplitude-frequency factor, which characterizes the dynamic excitation effect of vessel heave, is proposed. Then, in order to study the influences of nonlinear hydrodynamic damping effect on ROV response, an empirical formula for hydrodynamic damping ratio is proposed based on ROV displacement time histories. Finally, under consideration of the nonlinear damping effect, the unstable regions of vessel motion amplitude and frequency at different initial conditions are obtained.The results show that the vessel heave may induce a parametric excitation response to the ROV system. Particularly, parametric resonance is most pronounced, when the vessel motion frequency is close to twice the natural frequency of the ROV system. While, under the nonlinear damping effect generated by hydrodynamic force, the parametric resonance occurs when the amplitude-frequency factor reaches its threshold. The unstable regions under hydrodynamic damping are smaller compared with that without damping. Furthermore, as the initial angular displacement of ROV increases, the unstable region becomes smaller further, or, in other words, the parametric conditions of vessel heave for ROV response amplification become more demanding.

Full-scale experimental investigation into stability of segment-SCC-steel tube lining under external pressure

To investigate the mechanical deformation characteristics of the ‘Segment-SCC-Steel Tube’ combined bearing lining structure under internal and external pressure, the loading device and monitoring system for the stability analysis of the full-scale lining were proposed. The effect of cracked encased concrete and local external pressure on the instability mode of thin-walled steel pipes was explored by full-scale model experiment and three-dimensional FEM numerical simulation. The influence of SCC (Self-Compacting Concrete) and stiffening rings on the stability of steel pipes subjected to external pressure was discussed. The results show that SCC cracks occur and intensify with increasing internal pressure. The external water acts directly on the steel tube through cracking, resulting in wavy deformation, and the gap between the SCC and steel tube further increases. When calculating the critical external pressure for the steel pipe, the constraint of encased concrete can be ignored, and only the constraint effect of the stiffening ring can be considered. Therefore, the Von Mises formula was used to predict the critical external pressure between the stiffening rings with high accuracy. In addition, the stiffening ring can mitigate the crack propagation of nearby SCC. The steel tube remained in the elastic stage under internal pressure. In the full-scale experiment, the external pressure could not continue to rise after reaching 0.65 MPa. Nevertheless, the amplitude of the buckling wave continued to increase. It is considered that the steel pipe is in an unstable state, and the failure mode is dominated by single-lobe buckling.

Analysis of Coil Systems with Non-Symmetrical Fe Backings for Electrical Vehicle Wireless Charging Applications

Wireless power transfer is a widely applied technology whose market and application areas are growing rapidly. It is considered to be a promising supplement to the conductive charging of electrical vehicles (EVs). Wireless charging provides safety, convenience, and reliability in terms of mitigating issues related to wiring, risk of tearing, trip hazards, and contact wear inherent to the conductive charging. A variety of coil structures have been researched for EV charging applications; however, most of them were of the symmetrical type. This work analyzes systems of coils possessing ferromagnetic backing with non-symmetrical geometries and compares them with the conventional symmetrical ones. Numerical FEM simulation was applied in the research. The numerical models were verified analytically and experimentally. The impact of air-gap length, longitudinal displacement, number of turns, and width of the ferrite bars on coupling factor was investigated. The results suggest that coil systems with non-symmetrical structures of ferromagnetic backings are a good alternative to the conventional symmetrical structures for wireless electrical vehicle charging applications.

Assessment of cutting tool wear using a numerical FEM simulation model

The advancement of computational modeling techniques, such as FEM, has allowed to simulate complex machining processes with improved accuracy. Wear prediction is a crucial aspect in understanding and optimizing machining processes, as it directly impacts tool life, surface quality and overall machining efficiency. This work focuses on the FEM simulation, specially utilizing the DEFORM software, in conjunction with the Usui wear model, for wear prediction in machining operations. The Usui wear model, a well-established and widely used wear prediction approach, accounts for multiple wear mechanisms that include adhesion, abrasion, and diffusion. By incorporating the Usui wear model into the FEM simulation framework within the DEFORM software, it is possible to understand wear phenomena in machining processes. The integration of Usui wear model algorithms into DEFORM enables the simulation to accurately predict wear rates, distribution patterns, and progression of tool deterioration. This predictive capability facilitates the identification of critical wear zones and guides proactive measures to improve tool life, reduce production costs, and optimize machining productivity. This work presents research focused on wear prediction in cutting processes, utilizing FEM simulation with DEFORM software and incorporating the Usui wear model. Through a comprehensive analysis of wear phenomena, this research aims to optimize cutting parameters, improve tool life, and contribute to the advancement of machining and manufacturing technologies.

Verification of the Analytical Solution and Numerical Simulation for Tension - Pressure

The proposed constructions have to meet their use in terms of shape, dimensions and above all, strength. Parts of the structure are loaded by external forces. The load on the structure is examined in all parts and directions. Parts of the structure are stressed by a combination of basic types of stress. One of the basic types of stress is pull or pressure. The investigation of the part of the structure under tensile-compression stress is important because of the deformation, stability and strength of the structure as a whole. Analytical solution, classical experiment or modelling FEM can be used to predict the stress of structural parts. Currently, the most preferred solution is FEM numerical simulation. Numerical simulation has a more purposeful use in the solution of structural stability. The article contains the solution, tensile stresses for a steel rod, numerical simulation using the FEM method in the ANSYS program and analytically.

The Effect of Layer Orientation on the Behaviour of the Multilayered Composite Plates

In recent years, the composite materials have been increasingly used in various industries. The required knowledge, which is necessary in order to be able to use composite materials, composite structural elements, requires FEM numerical simulations. In this paper, the study of the effect of the layer orientation on the behavior of the multilayered composite plates is study by taking the three-layer laminate composite for different type of laminates with different symmetric and unsymmetric orientation of the lamina: 0/90/0, 90/0/90, 45/-45/45, -45/45/-45, 0/45/90, 0/-45/90, 90/45/0, 90/-45/0. Based on the obtained results, it can state that the emergence of displacements is dependent on the ply orientation. The used models do not give the same results of the maximum values of the vertical displacement of the layered laminate composite plates.

Diagnosis of Mechanoluminescent Crack Based on Double Deep Learning in Al 7075

The phenomenon of mechanoluminescence (ML) refers to the emission of light induced by mechanical stimulation applied to mechano-optical materials for example SrAl<sub>2</sub>O<sub>3</sub>:Eu,Dy (SAO). Numerous technologies on the basis of ML have been presented to visualize the stress or strain in various structures for the applications including structural health monitoring. As a result, extensive attention has been devoted to the design, synthesis, characteristics, optimizations, and applications of ML materials. However, challenges still remain in the standardization of ML measurement and evaluation, thereby commercially viable ML applications are currently unavailable. To overcome these difficulties, present study proposes ML measurement and evaluation techniques employing the ML fracture mechanics, finite element method, and dual deep learnings. For the effective normalization of visualized ML images under fixed initial ML intensity condition, continuous UV irradiation above the critical ML power density has been subjected to tensile and compact tension (CT) specimens. Therefore, Plastic Stress Intensity Factor (SIF) as well as crack tip stress field have been extracted successfully from normalized ML images based on ML fracture mechanics. To complement and verify the ML analysis, numerical FEM simulation and analytical ASTM calculation have been also provided. Finally, a double deep learning consists of Generative Adversarial Networks (GAN) and Convolutional Neural Networks (CNN) has been trained and tested for the standard evaluation of in-situ ML images.

Results of the “DPDT-Auger” Research Project on Screw Displacement Piles

Abstract The main objective of the “DPDT-Auger” research project was to test the prototype DPDT auger for forming screw displacement piles in the ground (patented in Poland in 2020). An additional aim was to develop design methods and rules for the making of such piles. The augers and piles were first tested on a model scale, and then more extensively in the real scale on experimental field plots. The results found the overall functionality of the DPDT auger to be good, and in several aspects better than that of the SDP auger. The load-bearing capacities and Q-s characteristics of piles made with both augers were considered comparable. All the conducted tests and their derived dependencies together with the results of in situ subsoil tests allowed for the development of empirical calculation methods and prognostic procedures, useful for designing and producing piles with DPDT and SDP augers. FEM numerical simulation rules for the considered piles were also developed, verified and calibrated by the results of real pile tests. This article describes only the most important final results of the research project but not the detailed results of the numerous tests and analyses that were carried out. Also omitted are the results of model tests and numerical simulations, as well as the implementation and acceptance recommendations, as they have already been or will be the subject of separate publications.

NUMERICAL AND THEORETICAL INVESTIGATION ON COMPOSITE COLD-FORMED STEEL JOINTS WITH LIGHTWEIGHT CONCRETE

This research intends to investigate behaviour of composite cold-formed steel joint numerically through finite element analysis by using ABAQUS and theoretically by referring to BS 5950-1:2000 and Green book P213 “Joint in Steel Construction-Composite Connection”. A composite joint is modelled by combination of composite beam and steel column with connection of HRS gusset plate and M12 bolts. The significant failure mode is local buckling in CFS column web which similar in experimental study, FEM numerical simulation and theoretical component calculation. The behaviour of the cold-formed steel composite joint will be expressed in moment-rotational and load-deflection relationship to determine the initial rotational stiffness and ultimate moment resistance. The findings from numerical and theoretical investigations are compared with the full-scale experimental study in three different thicknesses of gusset plate. A correlation in stiffness ratio and strength ratio are obtained in the range of 1.76 to 2.25, and 1.00 to 1.60 respectively indicating that the numerical modelling tends to underpredict the behaviour of the composite structures.

Numerical Analysis on Effects of Soil Improvement on Pile Forces on Existing High-Rise Building

Nowadays, seismic codes are regularly updated with new knowledge and a better understanding of the earthquake phenomenon. With these updates, existing buildings require a reevaluation of their stability and a process of reinforcement and/or retrofitting. This study investigated the effects of two types of ground improvement which use cement-mixing soil surrounding the foundation structure to reduce and redistribute forces acting on piles. This is especially important when the reevaluation of high-rise buildings leads to increased forces in the piles. Typically, buildings are designed while assuming fixed base boundary conditions at the foundation level, without considering soil–pile–structure interaction (SPSI). SPSI significantly influences the response of high-rise buildings supported by soft soil. Increasing the lateral resistance of the surrounding soil can reduce the influence of SPSI. In this study, a detailed dynamic numerical analysis was used to investigate the dynamic response of an SPSI system of a high-rise building under seismic load. A dynamic analysis was conducted on a modified layout of a real building, using real-time earthquake motion. The finite element program DIANA FEA was used to perform nonlinear 3D FEM numerical simulations, taking into account the essential SPSI phenomena, gap-slip between the piles and the soil, and free-field boundary conditions. A comparison of the data suggests that the bending moment and shear forces in the piles are reduced in magnitude and evenly distributed along the upper part of the pile, which reduces the stress concentration of the bending moment and shear forces at the contact between the piles and the pile cap.

The Effect of Radial-Shear Rolling Deformation Processing on the Structure and Properties of Zr-2.5Nb Alloy.

The rheological properties of the Zr-2.5Nb alloy by the strain rate range of 0.5-15 s-1 and by the temperature range of 20-770 °C was studied. The dilatometric method for phase states temperature ranges was experimentally determined. A material properties database for computer FEM simulation regards the indicated temperature-velocity ranges were created. Using this database and DEFORM-3D FEM-softpack, the radial shear rolling complex process numerical simulation was carried out. The contributed conditions for the ultrafine-grained state alloy structure refinement were determined. Based on the simulation results, a full-scale experiment of Zr-2.5Nb rod rolling a on a radial-shear rolling mill RSP-14/40 was carried out. It takes in seven passes from a diameter of 37-20 mm with a total diameter reduction ε = 85%. According to this case simulation data, the total equivalent strain in the most processed peripheral zone 27.5 mm/mm was reached. Due to the complex vortex metal flow, the equivalent strain over the section distribution was uneven with a gradient reducing towards the axial zone. This fact should have a deep effect on the structure change. Changes and structure gradient by sample section EBSD mapping with 2 mm resolution were studied. The microhardness section gradient by the HV 0.5 method was also studied. The axial and central zones of the sample by the TEM method were studied. The rod section structure has an expressed gradient from the formed equiaxed ultrafine-grained (UFG) structure on a few outer millimeters of the peripheral section to the elongated rolling texture in the center of the bar. The work shows the possibility of processing with the gradient structure obtaining and enhanced properties for the Zr-2.5Nb alloy, and a database for this alloy FEM numerical simulations are also presents.

Stability Analysis of Toll Road Embankment Induced by Liquefaction In Klaten Regency Based On FEM Numerical Simulation

The construction of toll roads in Klaten Regency supports community connectivity in increasing economic growth and accessibility to tourist areas around the southern part of Java Island. The location of this study is in Polanharjo District, Klaten Regency. The study area has geological conditions, sandy volcanic ash, and shallow groundwater levels and is accompanied by a history of earthquakes that have occurred greater than Mw. 5.0. These three things are triggers for liquefaction. This study discusses the stability analysis of toll road embankments at the STA. 10+724 on the construction of the Solo - Yogyakarta - YIA Kulon Progo Toll Road due to the potential for liquefaction reaching 14 meters. The road embankment construction is placed on the ground surface, which has the potential for liquefaction with a height of up to 5 meters. Calculate the safety factor using the numerical simulation finite element (Plaxis v.8.2 software) with static and pseudostatic analysis. Numerical calculations show that the stability analysis of toll road embankments placed on the ground with the liquefaction potential is still safe for construction with a safety factor on the static analysis (SF: 1.989 > 1.5) and pseudostatic analysis (SF: 1.912 > 1.1).

Optimization of hot deformation processing parameters for as-extruded 7005 alloys through the integration of 3D processing maps and FEM numerical simulation

The hot deformation behavior and microstructure were investigated for as-extruded 7005 alloys, which is the same as the billet state in real applications in the commercial forging process. It provides a more accurate understanding of the hot deformation flow behavior and microstructure evolution of 7005 alloys for commercial forging processing engineers and mold designers. The compression tests were conducted in temperatures 300–550 °C and strain rates 0.001–1 s−1 using an isothermal hot compression test. The power dissipation efficiency (η) and instability parameter (ξ) were calculated according to the true stress-true strain data obtained from the thermal compression tests. 3D thermal processing maps including the true strains were generated for as-extruded 7005 alloys, and the optimal processing conditions were selected according to η, ξ, and microstructure. The results showed that η increased with increasing temperature but decreased with increasing strain rate. The size of the instability region expanded with decreasing temperature and with increasing strain rate. An η < 0.20 is generally designated an instability region. Microscopic defects such as micro cracks and flow localizations could be observed, and the microstructures of the stability regions showed fine recrystallized grains with η above 0.30. The optimal processing conditions were determined to be a processing temperature between 425 and 500 °C and a strain rate between 0.1 and 0.01 s−1. This study is the first to optimize the closed die forging processing parameters through integration of 3D processing maps and a numerical simulation for a hub based on its real workpiece appearance. A function for prediction of the microstructure evolution is provided using commercial simulation software to help mold designers and forging processing engineers reduce the trial time.

Experiments and numerical simulation of the reinforcement effect of channel-steel-reinforced shield tunnel segments under unloading conditions

The increasing emergence of foundation pit excavations in dense urban areas has caused a series of adverse impacts on operating tunnels. Thus, the investigation of tunnel segment reinforcement is crucial and essential for geotechnical engineers. This article intends to investigate the reinforcement effect of the channel steel reinforcement method through a three-ring full-scale test and finite element simulation. The three-ring full-scale test is carried out by considering different confining pressures under the influence of different tunnel burial depths and different distances between the foundation pit and tunnel (clearance distances). In addition, a three-dimensional refined FEM numerical simulation verified by the full-scale model test is conducted to study the influence of foundation pit retaining structure deformation. The research results show that channel steel reinforcement can significantly improve the stiffness of the segment and its bearing capacity. The effect of the channel steel is more prominent in tunnels with a large burial depth. The stress and deformation of the segment are relatively uniform under the conditions of different clearance distances after the reinforcement of the channel steel. The top and bottom convergence of the segment and the bolt stress increase as the deformation parameters of the envelope structure increase; furthermore, the top and bottom convergence of the segment can be reduced up to 46.88% after the channel steel reinforcement.

Elastic Critical Resistance of the Simple Beam Grillage Resulting from the Lateral Torsional Buckling Condition: FEM Modelling and Analytical Considerations.

Transversely loaded beam grillages are quite often used in industrial construction. In order to produce a safe design of such structures, it is necessary to account for the lateral torsional buckling phenomenon, which reduces load-bearing capacity. To be able to calculate the relevant reduction factor, the elastic critical load must be determined. As regards the existing design practice for such structures, simplified conditions are assumed for the mutual restraint of the component beams. However, this approach does not correspond to reality. This study discusses the results of numerical investigations and analytical calculations concerning the effect of the elastic action of simple beam grillage (SBG) joints on the critical load, which results from the lateral torsional buckling (LTB) condition. The SBG was defined as a flat system of interconnected beams, unstiffened laterally and loaded perpendicularly to the grillage plane. The analysis covered H-shaped grillages with different span ratios of component beams, in which the main (coupling) beam was decisive for instability. The effectiveness of the use of closed-section stiffeners at the grillage joints was also investigated. The grillage elastic critical resistances (ECR) were determined for two variants of joint stiffening. The computations were performed by means of FEM numerical simulations. The spatial models were discretised with the following elements: (1) solid ones in Abaqus, (2) shell ones in ConSteel, and (3) thin-walled bars in ConSteel. The LTB critical moments of the weakest beam (critical beam), elastically restrained against warping and against lateral rotation (in the LTB plane), were computed using the analytical methods developed by the authors. To this end, the methods were proposed to determine the indexes of the critical beam elastic restraint in the adjacent stiffening beams. In the study, it was demonstrated that (1) taking into account the conditions of mutual elastic restraint and interaction of the component beams provides a more accurate assessment of the grillage ECR, (2) the use of closed-section stiffeners in the grillage joints increase the ECR compared with classic flat stiffeners, (3) the grillage ECR can be estimated based on the critical moment Mcr of the weakest beam (critical beam) when the conditions of its elastic restraint in joints are accounted for.

Compliant joint to reduce docking loads between CubeSats

This paper presents the design, modelling and experimental verification of a damping joint for application to miniature space docking mechanisms. The joint design is based on deformable elastomeric elements, thus avoiding any sliding or contact between moving components. Numerical FEM simulations have been conducted in order to quantify the joint mechanical characteristics (rigidity and damping coefficient) as a function of the main design parameters (geometry, material, assembly). The obtained parametric relations provide an estimate of the joint characteristics based on the selected design. An equivalent visco-elastic model is developed and implemented in dynamic simulations. The results of the experimental evaluation of the joint design provide a validation of the developed models and prove the advantage of adopting damping joints in docking applications between small satellites, like reduced contact loads and enhanced damping.