Search Results (61)

Blast mitigation of structures is an important research topic due to increasing intentional and accidental human-induced threats and hazards. This research area is essential to building capabilities in sustaining structural protection, site planning, protective design efficiency, occupant safety, and response and recovery plans. This paper investigates experimental tests and finite element analysis (FEM) of thin A36 steel sheets subjected to blast. Six field blast tests were performed at standoff distances of 300 mm and 500 mm. The explosive charges comprised 334 g of bare Composition B, and the steel sheets were 2 mm thick. The experimental results, derived from the analysis of high-speed camera recordings of the blast events, were compared with FEM simulations conducted using Abaqus^®/Explicit version 6.10. Three constitutive material models were considered in these simulations. First, the FEM simulation results were compared with experimental results. It was shown that the FEM analysis provided reliable results and was proven to be robust and cost-effective. Second, an extensive set of 460 additional numerical simulations was carried out as a parametric study involving varying standoff distances and steel sheet thicknesses. The results and methodologies presented in this paper offer valuable and original insights for engineers and researchers aiming to predict damage to steel structures during real detonation events and to design blast-resistant structures. Full article

In today’s aviation industry, research and studies are carried out to manufacture and design lightweight, high-performance materials. One of the materials developed in line with this goal is glass laminate aluminum-reinforced epoxy (GLARE), which consists of thin aluminum sheets and S2-glass/epoxy layers. Because of its high impact resistance and excellent fatigue and damage tolerance properties, GLARE is used in different aircraft parts, such as the wing, fuselage, empennage skins, and cargo floors. In this study, a survey was carried out and a low-velocity impact model for GLARE materials was developed using the ABAQUS (2014) version V6.14 software and compared with the results of low-velocity impact tests performed according to the American Society for Testing and Materials (ASTM) D7136 standard. This article introduces a novel integrated approach that combines detailed numerical modeling with experimental validation of GLARE 4A FMLs under low-velocity impact. Leveraging ABAQUS, a robust FEM featuring explicit analysis, cohesive resin interfaces, and custom VUMAT subroutines was developed to accurately simulate energy absorption, dent depth, and delamination. The precise model’s predictions align well with test results performed according to ASTM D7136 standards, exhibiting less than a 0.1% deviation in the displacement (dent depth)–time response, along with deviations of 4.3% in impact energy–time and 5.2% in velocity–time trends at 5.5 ms. Full article

This study investigates the effects of Laser Shock Peening (LSP) on residual stress distribution and surface deformation using a Finite Element Method (FEM) model. LSP is a surface treatment process that generates compressive residual stress by applying high-energy laser pulses over nanosecond timescales. The study aims to analyze the impact of key parameters, specifically laser spot overlap rate and power density, on the induced residual stress and surface deformation. A Design of Experiment (DOE) approach was used to systematically vary these parameters. These simulations were performed using the ANSYS Explicit Dynamics FEM with a Johnson–Cook material model to capture the nonlinear constitutive behavior. The research analyzes the distribution of residual stress and surface deformation caused by LSP. Increasing laser spot overlap and power density leads to higher compressive residual stress and surface deformation, revealing two distinct behavioral outcomes: either deep compressive stress with minimal deformation or a transition from compressive to tensile stress followed by significant surface deformation and a subsequent return to compressive stress. The results demonstrate strong agreement with existing experimental data presented in the literature. This study contributes novel insights into the interaction between LSP parameters and their effects on material properties, with implications for understanding LSP techniques in practical applications. The triangular pulse model and dual-overlap analysis offer a novel simulation strategy for optimizing LSP parameters in stainless steel. Full article

The simulation of human soft tissue deformation is a key issue in the research of surgical simulators. The most mathematically accurate model for soft tissue behavior is the finite element model (FEM), being the most widely adopted numerical approach for nonlinear continuum mechanics equations. The total Lagrangian explicit dynamics (TLED) model is a nonlinear FEM that could simulate the nonlinear deformation of soft tissues accurately and in real time. However, the main problems faced by this method are the high computational cost and the real-time performance of the simulation. Therefore, the linear FEM is used for ensuring computational efficiency and real-time performance of the simulation, though it is inadequate for capturing true biomechanical behavior. Consequently, we have to solve the problems of real-time performance and computational efficiency of nonlinear finite elements in simulating soft tissue deformation. To address this computational challenge, we propose a Dual-Mode Hybrid Dynamics Finite Element Algorithm (DHD-FEA). First, we divide the deformed soft tissues into the surgical area and the non-surgical area. Then, the TLED nonlinear FEM is applied to the simulation of soft tissue deformation in the surgical area, ensuring the accuracy of the simulation effect. Simultaneously, the simulation of soft tissue deformation in the non-surgical area using the linear FEM improves the real-time performance of the simulation and reduces the overall computational cost. Numerical results demonstrate that the error rate in the simulation of the DHD-FEA is lower than that of the complete linear FEM, and the computational efficiency is higher than that of the TLED. Therefore, the DHD-FEA not only ensures the accuracy of soft tissue simulation in the surgical area but also reduces the computational cost. Full article

To overcome the limitations of rigid body limit equilibrium methods in earth rock dam slope stability analysis, this study develops a system reliability framework using the finite element strength reduction method (FEM-SRM). An elastoplastic finite element model simulates dam construction and impoundment, identifying potential slip pathways. Each pathway, treated as a parallel system of shear-failed elements, is analyzed via the response surface method to derive explicit limit state functions. Reliability indices are computed using an improved first-order second-moment method, while interdependencies are assessed through stepwise equivalent linearization. System reliability is determined using Ditlevsen’s narrow bound method. Applied to a 314 m earth rockfill dam, three critical slip pathways were identified: upstream shallow (reliability index is 6.94), upstream deep (reliability index is 6.87), and downstream deep (reliability index is 7.44), with correlation coefficients between 0.26 and 0.89. The system reliability index (6.81) significantly exceeds the code target (4.2), highlighting the method’s ability to integrate material randomness, stress-strain nonlinearity, and multi-slip interactions. This framework provides a robust probabilistic approach for high earth rock dam stability assessment, enhancing engineering safety evaluations. Full article

The paper presents an innovative matrix method for defect analysis in heterogeneous structures with significant differences in stiffness parameters. The proposed approach modifies the finite element method (FEM) by introducing a refined type of finite element capable of handling regions with varying material and geometrical properties. Unlike traditional FEM discretization, which increases computational time calculations due to mesh refinement in stiffness-variable areas, the proposed method maintains a consistent discretization while adjusting shape functions to reflect internal stiffness changes. An original functional for modifying linear shape function distributions is introduced, leading to piecewise broken-line shape functions. This enhancement significantly improves the accuracy of numerical calculations, as verified by computational calculations. The explicit formulation of the stiffness matrix enhances computational efficiency, making the approach particularly useful for periodic structures with inclusions, voids, or localized material defects. The results of numerical tests demonstrate that the proposed method provides solutions closely aligned with conventional FEM results while substantially reducing computational costs. The approach is particularly relevant for structural engineering applications where defect analysis and material heterogeneity play a critical role in design and safety evaluation. Full article

The effective measurement method plays a vital role in the structural health monitoring (SHM) field, which provides accurate and real-time information concerning structural conditions and performance. The innovative measurement approach based on strain sensors, referred to as the inverse finite element method (iFEM), has been considered the most promising and versatile technology for meeting the requirements of the SHM system. However, the existing iFEM for shape sensing of thick plate structures has the drawback that the transverse shear effect makes no contribution to the three-dimensional deformation of thick plate structures. Therefore, this study proposed an enhanced inverse finite element method (iFEM) based on single-surface fiber Bragg grating strain sensors for reconstructing thick plate structures coupled with an analytical formulation. The method characterized the explicit relationship between transverse shear and bending displacement field on the mid-plane, which presents the sixth-order differential equation based on a variational approach. The three-dimensional deformation field can be obtained along the thickness direction, expanding the SHM application of iFEM for composite structures based on strain measurement. By performing shape sensing analysis of the thick plate model, the exactness and applicability of the present method are numerically and experimentally validated for different loading cases. Full article

This paper discusses novel numerical techniques for studying the damage to automotive safety components in carbon fiber reinforced polymer (CFRP) deployed in the automotive industry to protect passengers, high voltage batteries and powertrains from rear impacts. The idea proposed in the manuscript is to use Newmark’s methodology with the FEM for the numerical description of the explicit dynamic model of the components facing the standard impactor, following the Euro NCAP protocol. Using an explicit dynamic Radioss rear crash box, we have successfully demonstrated normal behavior for CFRP materials, where the value of kinetic energy is close to the theoretical value. Moreover, the simulation provides a behavior consistent with previous successful studies because the maximum dynamic time is the same as the total damage (0.10 ms). Full article

The zygomatic bone, a fundamental structure in facial anatomy, is exposed to fractures in impact situations, such as traffic accidents or contact sports. The installation of zygomatic implants can also alter the distribution of forces in this region, increasing the risk of fractures. To evaluate this situation, the first step is to develop a complex anatomical model from the stomatognathic point of view so that simulations in this sense can be validated. This study uses numerical simulation using a finite-element method (FEM) to analyze the behavior of the zygomatic bone under impacts of different velocities, offering a more realistic approach than previous studies by including the mandible, cervical spine, and masticatory muscles. Methods: An FEM model was developed based on 3D scans of actual bones, and simulations were performed using Abaqus Explicit 2023 software (Dassault Systemes, Vélizy-Villacoublay, France). The impact was evaluated using a steel cylinder (200 mm length, 40 mm diameter, 2 kg weight) impacted at speeds of 5, 10, 15, and 20 km/h. Zygomatic, maxillary, and mandibular bone properties were based on dynamic stiffness parameters, and bone damage was analyzed using ductile fracture and fracture energy criteria. Results: The results show that at impact velocities of 15 and 20 km/h, the zygomatic bone suffered crush fractures, with impact forces up to 400 kg. At 10 km/h, a combination of crushing and bending was observed, while at 5 km/h, only local damage without complete fracture was detected. The maximum stresses were concentrated at the zygoma–jaw junction, with values above 100 MPa at some critical points. Conclusion: The FEM model developed offers a detailed representation of the mechanical behavior, integrating the main structures of the stomatognathic apparatus of the zygomatic bone under impact, providing valuable information to, for example, advance injury prevention and zygomatic implant design. Higher impact velocities result in severe fractures, underscoring the need for protective measures in clinical and sports settings. Full article

Carbon fiber reinforced polypropylene (CF/PP) thermoplastics integrate the superior formability of fabrics with the recoverable characteristics of polypropylene, making them a pivotal solution for achieving lightweight designs in new energy vehicles. However, the prevailing methodologies for designing the structural performance of CF/PP vehicular components often omit the constraints imposed by the manufacturing process, thereby compromising product quality and reliability. This research presents a novel approach for developing a stamping–bending coupled finite element model (FEM) utilizing ABAQUS/Explicit. Initially, the hot stamping simulation is implemented, followed by the transmission of stamping information, including fiber yarn orientation and fiber yarn angle, to the follow-up step for updating the material properties of the cured specimen. Then, the structural performance analysis is conducted, accounting for the stamping effects. Furthermore, the parametric study reveals that the shape and length of the blank holding ring exerted minimal influence on the maximum fiber angle characteristic. However, it is noted that the energy absorption and crushing force efficiency metrics of the CF/PP specimens can be enhanced by increasing the length of the blank holding ring. Finally, a discrete optimization design is implemented to enhance the bending performance of the CF/PP specimen, accounting for the constraint of the maximum shear angle resulting from the stamping process. The optimized design resulted in a mass reduction of 14.3% and an improvement in specific energy absorption (SEA) by 17.5% compared to the baseline sample. Full article

In cold climate regions, ships navigate through diverse ice conditions, making the varied interaction scenarios between hulls and ice critically important. It is crucial to consider the safety and integrity of the hull during an ice–hull interaction, especially in the presence of lightweight structures. Proper design and material selection can help improve the structure’s ability to withstand ice forces. Within the scope, understanding the behavior of ice and its interaction with the structure can inform the development of appropriate measures to minimize possible damage or failure. The current study focuses on the interactions occurring during the impact loading phases, which are characteristic of thin first-year ice. A sandwich structure made with carbon fiber-reinforced epoxy prepreg and PVC core was investigated. Low-velocity ice impact was modelled using the Ansys Workbench 2023 R2 and LS-DYNA R11 explicit solver. As the material model, the *MAT055 was chosen based on the literature, while ice was represented with its equation of state. The Tsai Wu criterion was adopted to identify tensile and compressive failure in the matrix and fibers. This simulation allowed us to evaluate how the composite material responds to ice impacts, considering factors such as the speed of the impact, the shape and thickness of the ice, and the properties of the composite material itself. Full article

Single point incremental forming (SPIF) is becoming more and more widely used in the metal industry due to its high production flexibility and the possibility of obtaining larger material deformations than during conventional sheet metal forming processes. This paper presents the results of the numerical modeling of friction stir rotation-assisted SPIF of commercially pure 0.4 mm-thick titanium sheets. The aim of this research was to build a reliable finite element-based thermo-mechanical model of the warm forming process of titanium sheets. Finite element-based simulations were conducted in Abaqus/Explicit software (version 2019). The formability of sheet metal when forming conical cones with a slope angle of 45° was analyzed. The numerical model assumes complex thermal interactions between the forming tool, the sheet metal and the surroundings. The heat generation capability was used to heat generation caused by frictional sliding. Mesh sensitivity analysis showed that a 1 mm mesh provides the best agreement with the experimental results of total forming force (prediction error 3%). It was observed that the higher the size of finite elements (2 mm and 4 mm), the greater the fluctuation of the total forming force. The maximum temperature recorded in the contact zone using the FLIR T400 infrared camera was 157 °C, while the FE-based model predicted this value with an error of 1.3%. The thinning detected by measuring the drawpiece with the ARGUS non-contact strain measuring system and predicted by the FEM model showed a uniform thickness in the drawpiece wall zone. The FE-based model overestimated the minimum and maximum wall thicknesses by 3.7 and 5.9%, respectively. Full article

This study employs the finite element (FE) method to analyze the Incremental Sheet Forming (ISF) process of Ti-6Al-4V titanium alloy. The numerical modeling of pressure-assisted warm forming of Ti-6Al-4V sheets with combined oil-heating and friction stir rotation-assisted heating of the workpiece is presented in this article. The thermo-mechanical FE-based numerical model took into account the characteristics of the mechanical properties of the sheet along with the temperature. The experimental conditions were replicated in FEM simulations conducted in Abaqus/Explicit, which incorporated boundary conditions and evaluated various mesh sizes for enhanced accuracy and efficiency. The simulation outcomes were compared with actual experimental results to validate the FE-based model’s predictive capacity. The maximum temperature of the tool measured using infrared camera was approximately 326 °C. Different mesh sizes were considered. The results of FEM modeling were experimentally validated based on axial forming force and thickness distribution measured using the ARGUS optical measuring system for non-contact acquisition of deformations. The greatest agreement between FEM results and the experimental result of the axial component of forming force was obtained for finite elements with a size of 1 mm. The maximum values of the axial component of forming force determined experimentally and numerically differ by approximately 8%. The variations of the forming force components and thickness distribution predicted by FEM are in good agreement with experimental measurements. The numerical model overestimated the wall thickness with an error of approximately 5%. By focusing on the heating techniques applied to Ti-6Al-4V titanium alloy sheet, this comparative analysis underlines the adaptability and precision of numerical analysis applied in modeling advanced manufacturing processes. Full article

During machining, the surface of the machined materials is damaged and tool wear occurs, sometimes even to complete failure. Machining of thin-walled parts is generally cumbersome due to their low structural rigidity. The study deals with the effect of the feed rate and the thickness of the thin-walled part on the dynamic behavior and stability of the turning process during the roughing and finishing of thin-walled tubular workpieces made of steel alloy 42CrMo4. At the same time, the cutting forces and deformations of the workpiece were also evaluated via numerical and experimental approaches. The numerical study is based on a three-dimensional (3D) finite element model (FEM) developed using the ABAQUS/Explicit frame. In the model, the workpiece material is governed by the behavior law of Johnson–Cook. Numerical and experimental results show that the cutting forces and the quality of the machined surface depend not only on the choice of cutting parameters but also on the dynamic behavior of thin-walled parts due to their low rigidity and low structural damping during the machining operation. Cutting forces are proportional to the feed rate and inversely proportional to the thickness of the part. Their variations around the average values are low for roughing tests where the wall-part thickness is higher or equal to 3.5 mm. However, these variations intensify for finishing tests where the wall thickness is less or equal to 1.5 mm. Indeed, the recorded FFT spectra for a finishing operation show several harmonics that occurred at around 550 Hz, and the amplitude of the peaks, which describes the level of power contained in the signals, shows an increase similar to that of the amplitudes of the temporal signal. The flexibility of the part generates instability in the cutting process, but the frequencies of the vibrations are higher than the frequency of rotation of the part. Full article

Rockfall events represent a significant hazard in mountainous regions, putting human safety and critical infrastructure at risk. Various mitigation devices are available, among which, Rockfall protection embankments (RPEs) located in natural soil are passive defense work suitable for high-energy and high-frequency events. Currently, limited research has been conducted in this area, with the Austrian standard ONR 24810 providing the sole codified design method. A parametrical analysis involving both the RPE geometry and the impact features was developed by Abaqus/Explicit FEM code, with 2270 cases overall. The research aims to identify conditions under which RPEs effectively stop falling blocks, focusing on two failure mechanisms: the block pass over the RPE after impacting the upstream side bank and the RPE structural collapse. Additionally, the interaction between RPEs and their foundations during the impact is explored. The results provide valuable insights into the dynamic behavior of these structures. In terms of design considerations, this study offers analytical equations to quantify crater depth and foundation stress induced by the impact. Furthermore, design charts are developed to assess the block passing over verification and the structural collapse verification. Full article