Additively manufactured lightweight lattice structures are being widely studied, one aspect being their energy absorption characteristics under large deformation, because their load–deformation ...responses can be adjusted by specifically tailoring the geometry of constituent cells. In this study, a newly-proposed hybrid structure (HS), which combines the geometrical features of a traditional primarily axial-deformation dominated octet cell and a primarily bending-dominated rhombic dodecahedron (RD), is designed and fabricated via Fused Deposition Modelling. To ascertain whether the geometrical hybrid enhances the energy absorption performance, the quasi-static compressive responses of such lattices are examined and compared with those of the constituent structures, i.e. the octet and RD. It is noted that the layer-wise additive manufacturing process affects the isotropy of the lattices, as it introduces angle-dependent strut material properties. To study this, the mechanical responses of lattice samples compressed along the rise (printing) and transverse directions are compared. Energy absorption efficiency criteria are adopted to identify the onset of the densification phase, and to evaluate how closely they approximate an ideal energy absorber. Finite element models are also established to study the effect of cell topology and loading direction on the resulting deformation modes and failure patterns. Compression tests along the rise direction show that the proposed novel hybrid structure displays a high stiffness and strength comparable to the octet, as well as a relatively stable post-yield stress–strain behaviour similar to that of an RD. The study demonstrates that the octet and HS topologies are significantly affected by the direction of compression, which alters the stress level and changes the deformation mode. The reason for this is analysed by examining deformation at the cell level, and this is substantiated by FE simulation of compression of cell assemblies, and CT scan images of actual lattices.
•Hybrid Structure, geometrical hybrid of octet and RD, to combine their advantage.•Anisotropy of lattices induced by layer-wise FDM-based additive manufacturing.•Different sensitivity to loading direction associated with lattice cell architecture.•Angle-dependent strut material properties used to simulate anisotropy of lattice.•Solid element better for modelling lattices with struts of small aspect ratios.
Multiscale modeling is an effective approach for investigating multiphysics systems with largely disparate size features, where models with different resolutions or heterogeneous descriptions are ...coupled together for predicting the system’s response. The solver with lower fidelity (coarse) is responsible for simulating domains with homogeneous features, whereas the expensive high-fidelity (fine) model describes microscopic features with refined discretization, often making the overall cost prohibitively high, especially for time-dependent problems. In this work, we explore the idea of multiscale modeling with machine learning and employ DeepONet, a neural operator, as an efficient surrogate of the expensive solver. DeepONet is trained offline using data acquired from the fine solver for learning the underlying and possibly unknown fine-scale dynamics. It is then coupled with standard PDE solvers for predicting the multiscale systems with new boundary/initial conditions in the coupling stage. The proposed framework significantly reduces the computational cost of multiscale simulations since the DeepONet inference cost is negligible, facilitating readily the incorporation of a plurality of interface conditions and coupling schemes. We present various benchmarks to assess the accuracy and efficiency, including static and time-dependent problems. We also demonstrate the feasibility of coupling of a continuum model (finite element methods, FEM) with a neural operator, serving as a surrogate of a particle system (Smoothed Particle Hydrodynamics, SPH), for predicting mechanical responses of anisotropic and hyperelastic materials. What makes this approach unique is that a well-trained over-parametrized DeepONet can generalize well and make predictions at a negligible cost.
Tungsten carbide (WC), renowned for its exceptional hardness and wear resistance, plays an essential role in various industrial applications (cutting tools, abrasives, and wear-resistant components). ...While traditional methods involve hot pressing, Spark Plasma Sintering (SPS) combined with Additive Manufacturing (AM) offers a cutting-edge approach, utilizing high-voltage electric current and mechanical pressure for rapid densification, particularly advantageous for fabrication of complex shape components made from challenging materials like nanosized binderless tungsten carbide. The study encompasses the entire spectrum of the powder's characterization, extending to the development of an intricate finite element simulation tailored for SPS sintering. Sintering cycles underscore the exceptional quality of the powder, demonstrating full density microstructures even under low-temperature (1550 °C) and low-pressure (50 MPa) conditions. The nanosized powder exhibits minimal microstructural coarsening, reflecting the high quality of the initial pure tungsten carbide nano powder. The core of this study revolves around the methodology employed for deriving constitutive parameters, following the Skorohod-Olevsky theory of continuum sintering. The derivation methods include variations in temperature, heating regimes, and stepwise pressure application during SPS. Additionally, a grain growth model is formulated based on microstructural analysis. Critical parameters, including the apparent sintering activation energy (800 kJ/mol) and the creep law stress exponent (n = 4.0), are discussed. The article concludes with the integration of the mechanical sintering model into finite element method (FEM) software, considering thermal and electrical aspects for a comprehensive SPS-AM modeling approach and its application to complex shape production. The research aims to enhance the understanding of SPS for tungsten carbide, providing insights for its application in manufacturing cutting-edge components in challenging environments.
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•Protective performance of ACH and full-covered helmet under blast wave were quantitatively analysis by the degree of cranial injury.•ACH does not provide blast protection and may ...even slightly aggravate cranial injury.•Fully-covered helmet can reduce the brain acceleration, strain, displacement, pressure, von-Mises stress and energy absorption.•The lighter fully-covered helmet can effectively reduce head injury by 35%, especially by reducing acceleration, strain and pressure.
Blast traumatic brain injury (BTBI) is the major type of injury, existing helmets are mainly designed to resist bullets and fragments, so it is necessary to study the explosion- proof performance of helmets. In this study, the validated finite element models including head, Advanced Combat Helmet (ACH), fully-covered helmet based on the prototype of Iron Man helmet were used to establish the blast wave-helmet-head fluid–solid coupling model, dynamic responses such as blast wave flow field pressure, skull stress, brain tissue pressure, displacement and energy absorption were obtained through simulations.
Quantitatively analyzed the protective performance of helmets show that wearing ACH can’t reduce the severity of brain injury, but rather increased about 5% compared to without wearing helmet. Wearing fully-covered helmet with same thickness as ACH can reduces the degree of brain injury by about 5%. Fully-covered helmet with same weight as ACH provides better protection, which can reduce the degree of brain injury to 65% than without wearing helmet. Research show that optimizing the shape and thickness of helmet can greatly reduce the brain injury, lighter fully-covered helmet can provide better protection for the brain under blast wave environment. The results can provide reference for new design of helmets.
•Rapid, accurate and flexible prediction of strata and tunnel deformation.•Physics of tunnel deformation embedded in the two-stage surrogate modelling procedure.•Reduced computation by integrating ...parametric FE and LHS design.
Rapid and accurate prediction of strata and tunnel deformation caused by foundation pit excavation is an effective way to mitigate risks in the operation of urban underground spaces. This study proposes a two-stage surrogate modeling strategy, with the aid of predictive capabilities of numerical simulation-based surrogate model and deformation mechanism of underground structures embedded in the modeling procedure. Firstly, a parametric finite element (FE) model of foundation pit–strata–existing tunnel system is established. Subsequently, a first-stage kriging surrogate model is established based on Latin hypercube sampling (LHS) and the aforementioned parametric FE model. Then, another second-stage kriging surrogate model is constructed by utilizing the predictions of the first-stage surrogate model and the deformation mechanism of underground structures. The prediction performances of the two surrogate models and the improvement in performance from this two-stage surrogate modeling strategy were fully investigated via FE simulation examples. The prediction accuracy of strata deformation using the first-stage surrogate model was high at 96.00 ∼ 96.25 %, but for tunnel deformation it was low at 88.75 %. However, after using the two-stage surrogate modeling strategy, the prediction accuracy of the tunnel deformation increased to 95.69 %. Finally, this two-stage surrogate modeling strategy was validated using measurement data from a real-world project, the final prediction results are basically consistent with both the field measurement data and the refined FE model. Consequently, this approach is deemed a viable substitute for numerical simulation, offering rapid and accurate predictions to support digital twin management of urban underground space.
In this paper, the light-induced bending of a liquid crystal elastomers (LCEs) plate with the coupled effect of light incidence angle and deformation is studied for the first time. Based on the ...Reissner-Mindlin plate theory, a finite element model incorporating the coupled effect is developed to investigate the bending behavior of the LCEs plate. Deflections of the LCEs plate subjected to the light illumination with different light incidence angles are given. It is found that the coupled effect will significantly affect the bending deformation of the LCEs plate such as the location of the peak and the bending shape. Comparisons of the spontaneous bending of the LCEs plate with and without the coupled effect demonstrate the necessity of this study, especially for the LCEs plate subjected to the non-normal incidence light.
•The coupled effect of light incidence angle and deformation on the bending of LCEs plates is studied.•A photo-mechanical coupling model of the LCEs plate with considering director orientation is developed.•Coupled effect affects bending deformation of the LCEs plate such as location of the peak and the bending shape.•Some areas of the plate will exhibit self-shadowing.
•Computational model was developed to predict heat and mass transfer considering sample shrinkage and porosity.•Model is capable of predicting shrinkage, density and porosity of sample.•Model can be ...used to study local moisture and temperature profiles within the sample at any time instance.
Fruits and vegetables are porous in nature and undergo pronounced shrinkage during convective drying process. Therefore, shrinkage and porosity should be taken into consideration while predicting heat and mass transfer. This work was conducted to study shrinkage and porosity changes along with simultaneous heat and mass transport during the process. Potato slices were subjected to drying for 7h at 62°C. It was observed that shrinkage varies linearly with respect to moisture content and reduction in radial dimension of potato slices was around 35%. Porosity undergoes rapid increase after attaining certain moisture content in final stages of drying. The work was extended to study the influence of shrinkage and porosity on heat and mass transfer. Simulated results were validated with experimental values. This model can be employed to predict temperature, moisture, density profiles and to study shrinkage and porosity of various fruits and vegetables.
The pulsed eddy current (PEC) technique exhibits considerable benefits over conventional eddy current techniques. The structure and dimensional parameters of PEC sensors considerably influence PEC ...systems. Conventional PEC sensors are susceptible to background noise of a magnetic excitation field. To strengthen the magnetic gathering ability and improve detection sensitivity, a magnetic shielding shell structure was introduced to PEC sensors. In this study, a novel canister structure and magnetic core-based PEC sensor with magnetic shielding was designed. Finite element simulation and experimental study were performed subsequently to optimize the design. A three-dimensional finite element simulation model was established according to the eddy current detection mechanism and electromagnetic shielding principle. The influence of the PEC sensor structure and size on its detection performance was observed. Next, a two-dimensional axis-symmetric model was established, and the size of this PEC sensor was optimized by using the orthogonal approach. The results revealed that the detection performance of this PEC sensor could be improved by incorporating an appropriate magnetic shielding mechanism and through the optimization of the sensor size. The research results show that compared with the PEC sensor without magnetic shield, the PEC sensor with magnetic shield developed in this paper can obtain higher signal amplitude and can be better applied to surface and subsurface defect detection.
The present work employed the finite element model (FEM) to predict the influence of successive increases in borate (B2O3) contents, from 0 to 25 mol%, on mechanical properties and dynamic behavior. ...By feeding the isotropic elasticity characteristics of the phosphosilicate glass to the model, such as Young's modulus, density, and maximum compressive stress of the produced glass samples to fit the aim of their clinical use. The effect of successive addition of B2O3 on the in vitro bioactivity of the examined glasses in addition to examined after being dipped in simulated body fluid (SBF) at different times. Moreover, tracking the formation of hydroxyapatite (HA)-like layers on their surfaces using X-ray diffraction technique (XRD) technique and scanning electron microscopy (SEM). The results obtained indicated that increasing B2O3 content to 25% was responsible for improving the deflect resistance by 39%.On the other hand, neither shear stress nor principles stress was affected by this increase in B2O3 content. Moreover, the gradual increases in B2O3 contents were very helpful in improving the bioactivity of the samples. The prepared glasses can be successfully used in bone replacement applications from these promising results.
•Strengthening of RC beams by UHPFRC jacketing using different configurations.•Jacketing using precast panels attached by epoxy or fresh cast in a mold.•Three sided jacketing resulted in high ...capacity enhancement but reduced ductility.•Two-sided and bottom jacketing yielded strength enhancement with high ductility.•FE modeling of jacketed beams captured the experimental response reasonably well.
In this study, the effectiveness and efficiency of two different techniques for strengthening of reinforced concrete (RC) beams using ultra-high performance fiber reinforced concrete (UHPFRC) was investigated i.e.; (i) by sand blasting RC beams surfaces and casting UHPFRC in-situ around the beams inside a mold and (ii) by bonding prefabricated UHPFRC strips to the RC beams using epoxy adhesive. Beams under each technique were strengthened in three different strengthening configurations; (i) bottom side strengthening (ii) two longitudinal sides strengthening (iii) three sides strengthening. Bond strength tests were carried out to ascertain the bond between normal concrete and the UHPFRC, for both sand blasting and epoxy adhesive techniques. Test results for retrofitted beams under flexure regarding various behavioral attributes such as crack propagation, stiffness and failure load indicated significant positive developments resulting from the two strengthening techniques. Beams strengthened on three sides showed the highest capacity enhancement, while beams strengthened only at the bottom side showed the least enhancement. However, there were some concerns regarding loss of ductility with increased use of UHPFRC as part of the tensile retrofit. Finite element (FE) and analytical models were developed to predict the behavior of the beam specimens. The result of the models showed good agreement with experimental results, as they were able to predict the behavior of the beams with high accuracy.
