•Original lightweight hybrid lattice structures formulated and fabricated by FDM-based 3D printer to achieve favorable energy absorption characteristic.•Addressing limitations of conventional octet ...topology regarding its severely fluctuating post-yield response following a high yield stress.•Stable post-yield stress plateau without sacrificing stiffness and strength significantly in proposed hybrid structures validated by both compression experiments and finite element simulations.•Incorporating fabrication-angle-dependent strut material properties into simulations identified as essential to correlate with experimental results.
Lightweight cellular materials and structures are widely used in load-bearing and energy absorption applications, because of favorable mechanical properties such as high compressibility and low relative density. Recent progress in additive manufacturing techniques has enabled specific architectural geometries of unit cells in cellular structures to be tailored for particular needs. Numerous metallic and polymeric cellular lattices comprising different unit cell topologies have been manufactured and examined in terms of their energy absorption performance. In this study, two designs of hybrid three-dimensional cubic lattices which combine the advantages of an octet and a bending-dominated structure were established, and fabricated via the Fused Deposition Modeling technique. To validate the energy absorption capability of these new hybrid lattices, quasi-static uniaxial compression tests were conducted on samples made from Polylactic Acid. Numerical simulations were also performed to facilitate analysis of the deformation modes of the specimens tested in experiments. Tensile tests on solid dog-bone samples printed at various angles with respect to the build plate reveal fabrication-angle-dependent anisotropy. Consequently, material properties that depend on cell strut inclination were incorporated into the simulations. Compared with a conventional octet that possesses a high stiffness but a fluctuating post-yield response, the experimental results show that the new designs are capable of producing a relatively stable post-yield stress plateau without sacrificing stiffness and strength significantly. The present study indicates the potential for further enhancement of the energy absorption performance of lattice structures by tuning their topological architectures appropriately.
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•The first auxetic nails are designed, fabricated, and experimentally investigated.•The auxetic nails do not always exhibit superior mechanical performance to non-auxetic nails.•The surface roughness ...plays a significant role in the applications of auxetic nails.•Several criteria are proposed for the future design of auxetic nails.•Some disadvantages of auxetic materials are discussed.
Under uniaxial compression (tension), auxetic materials would shrink (expand) laterally. It has been speculated that the auxetic property could be used to design superior nails for easier push-in and harder pull-out. In this study, the first auxetic nails are designed, fabricated and experimentally investigated. Pine timber and medium-density fibreboard are selected as testing materials. The push-in and pull-out performance of auxetic and non-auxetic nails is compared by using two key parameters of the maximum compressive force and the maximum tensile force. It is found that the auxetic nails do not always exhibit superior mechanical performance to non-auxetic ones. Also, the small auxetic deformation of one typical designed auxetic nail is revealed by the experimentally validated finite element model. The experimental and numerical results illustrate the limitations of exploiting the auxetic property in the nail application. Some suggestions are provided for more effective designs of future auxetic nails.
Due to their potential to recover strength and stiffness with a minimum impact on aerodynamic performance of a damaged structure, scarf repairs are boosted as a viable repair option for primary ...aero-structures. So far, most of the experimental and numerical studies have been limited to joint specimens and their equivalent 2 Dimensional models and a few number of studies attempted to examine the results using real scarf repair geometry. Suggestions previously made to justify the difference between scarf joint and scarf repair strength and possible solution to diminish the difference are challenged in current work. Here, it is tried to investigate the strengths and shortcomings of 2D scarf joint modelling and their influence on the associated results by promoting 3 Dimensional Finite Element Modelling of complete geometry of the scarf repair. A method to assign material properties to a planar geometry of composite material has been developed that provides the possibility of plane strain, plane stress, and generalized plane strain modelling options of a scarf repair cross section under uniaxial load. Besides, accuracy of scarf joint specimen as a representative to scarf repair to predict load carrying capacity of a circular scarf repair is investigated. The study mainly focuses on 2D and 3D FEM simulation results discrepancies considering the effect of angle ply, cross ply and various stacking sequences of quasi-isotropic laminate under uniaxial and equi-biaxial loads. Results show that the laminate lay-up angles and stacking sequence substantially affect the 2D and 3D simulations agreement. Also, the observed discrepancies in scarf repair and scarf joint results are not limited to the effects of plastic deformation of the adhesive, but it seems the modelling shortcomings greatly affect the results. In overall, the current work demonstrates that for a particular laminate, joint specimen does not represent reasonably a scarf repair. In fact, the load carrying capacity estimated based on joint specimen data can mislead decision making procedure in a way that results in rejection of an eligible repair. To avoid inaccurate strength estimation, a 3D simulation of a scarf repair especially for a load other than uniaxial tension or compression is strongly recommended.
The gear foundation is commonly assumed to be a rigid body in analyzing the dynamic characteristics of the gear system. This modeling approach may not be appropriate for building the gear model with ...lightweight features. Therefore, this paper proposes a gear dynamic model considering the flexible gear. The shell element with gyroscopic effect is employed to establish the gear finite element model, retaining the gear foundation and teeth structure. The fixed interface modal synthesis method is used to improve computational efficiency. The proposed model is verified by comparing it with the results calculated by Ansys. Based on the proposed model, the effects of gear flexibility on the dynamic characteristics of the spur and helical gear system are investigated. Numerical results show that the developed model can degenerate into the classical gear dynamic model. Due to the assumption of the gear as rigid discs, the predicted resonance speed by the conventional gear dynamic model is larger than the proposed model. Gear flexibility affects the dynamic characteristics of the spur and helical gear system differently. It's worth noting that the dynamic axial meshing force can excite the nodal diameter vibration in the helical gear system. The proposed model provides the theoretical basis and optimization tools for the high-performance design and vibration and noise reduction of high-speed lightweight gear transmission systems.
MgB2 superconducting material has a wide range of application prospects for its high transition temperature, favorable structural characteristics and low cost. When using MgB2 to produce ...superconducting energy storage magnets, it is necessary to twist superconducting wires into cables to increase their current carrying capacity. One typical cable is made of 6 MgB2 superconducting wires wrapped around 1 central copper wire, forming a (6+1) structure. MgB2 coils used for energy storage require solid impregnation and can be cooled by liquid hydrogen or solid nitrogen. Due to the need for fast charging and discharging of energy storage coils and low thermal conductivity of commonly used epoxy resin impregnation and solid nitrogen, it is necessary to consider the temperature variation characteristics caused by AC loss and eddy current loss during operation process. A coil with 8 turns in each layer and 4 layers is simulated using the (6+1)-structure cable. In order to obtain better temperature distribution results while reducing the time required for simulation operation, the simulation time is set to 1 s. The impact of epoxy resin properties and surrounding environments on the coil are then analyzed. The results indicate that increasing the thermal conductivity of epoxy resin can significantly reduce the maximum temperature of the coil, while only changing the cooling method is unhelpful in dealing with the problem of local overheating of the coil.
•Epoxy resin affects the position with the highest temperature in a coil.•Cooling effects of static liquid hydrogen and solid nitrogen are almost the same.•Flow rate of liquid hydrogen is not helpful in avoiding coil overheating.
The impact resistant behaviors of boride reinforced Ti-6Al-4 V functionally graded materials prepared by spark plasma sintering (SPS) with compositional gradients of 90°, 84°, 82°and 79° were ...investigated based on the experimental test and the finite element method. The material constitutive parameters of the boride reinforced Ti-6Al-4 V alloys with different TiB2 contents were determined, and the Johnson Holmquist Ceramics (JH-2) model and a cohesive contact model were established and developed to predict the crack propagation and the impact resistance behaviors of the materials. The calculated results agreed well with the split Hopkinson press bar (SHPB) experimental results. The optimum material composition gradient design scheme with a continuous transition property from a high-toughness end to a high-strength end along the thin-thickness direction was determined. The G84 (0, 0, 15, 30 wt% TiB2) had the best impact resistance, with Young's modulus of 55505±5 GPa, compressive strength of 2045±5 MPa, and microhardness ranging from 535±5HV to 1246±5HV, exhibiting high strength and hardness at a high-strength end that can prolong the interaction time between the impactor and the materials, while the elongation of 39 % at its high-toughness end can cause tensile deformation, consuming impact kinetic energy efficiently. Combined with the experimental and numerical analysis results, the impact resistance and the crack-alleviated mechanisms of boride reinforced Ti-6Al-4 V functionally graded materials were discussed. Reducing the compositional gradient can alleviate the difference in coefficients of thermal expansion between composites, which may lead to strengthen the reflected wave, lower the compression wave, and suppress high-strength end failure efficiently, meaning of relieving the stress concentration under extreme service conditions. Moreover, the effects of the presence of the borides, such as in situ-formed TiB, remained TiB2at al., the dislocation defects and the whisker-like TiB on the armour materials resist fracture and layer cracking were also analyzed. This work provided a method for designing high performance of boride reinforced Ti-6Al-4 V functionally graded materials with high impact resistance and thin thickness.
•The boride reinforced Ti-6Al-4 V functionally graded materials exhibiting great promise in good impact resistance were designed and prepared.•The material constitutive parameters of the boride reinforced Ti-6Al-4 V alloys, the Johnson Holmquist Ceramics (JH-2) model and a cohesive contact model were established to predict the impact resistance behaviors of the materials.•The impact resistance and the crack-alleviated mechanisms of boride reinforced Ti-6Al-4 V functionally graded materials were discussed.•This work provided a method for designing high performance of boride reinforced Ti-6Al-4 V functionally graded materials with high impact resistance and thin thickness.
During multilayer multitrack laser cladding, secondary melting and solidification in the interlayer lap zone have a significant impact on the mechanical properties of cladding coatings. However, ...mathematical modeling of the melt flow and solidification behavior of multilayer, multitrack laser cladding interlayer lap zones is lacking. In this paper, a 3D finite element model was established to investigate the mass and heat transfer processes in both lap and non-lap zones during the laser cladding of multilayer multitrack Fe-Cr-based alloys on 45# steel surface. A dynamic grid is used to track the free surface of the melt pool, while the enthalpy method is used to simulate the solid-liquid phase transition. The change in thermophysical properties with temperature, as well as the change in laser energy and alloy powder flow density in the lap zone, were taken into consideration. The influence of the number of cladding layers on the heat and mass transfer in the molten pool, remelting, and solidification in the lap zone was investigated, along with its intrinsic mechanism. The results show that the model can accurately predict the size and microstructural change law of coating layers, including the grain size of the lap region between layers. The melt pool temperature and grain size increase with the number of cladding layers, while the convection and cooling velocities decrease. In addition, the grain size in the lap zone of the cladding is larger than that in the nearby non-lap zone. Using solidification parameters extracted from the solidification front of the molten pool, changes in grain size and morphology were predicted for both the interlayer lap and non-lap zones. The numerical calculation results were consistent with the experimental measurements.
•Prediction of the dynamic evolution of melt pool temperature and geometry•Clarified the impact of clad layers number on the velocity and temperature field•Grain size within the interlayer lap zone exceeds that of the adjacent grains.•Secondary solidification cooling rate in interlayer lap zone is lower than the first.•Grain size at the top of the cladding becomes larger as the number of layers increases.
Greenhouse drying system is used to dry agricultural products or low-temperature thermal drying using a greenhouse structure. In this paper, an experimental and simulation study is carried out to ...evaluate the drying performances of an active solar greenhouse dryer using COMSOL Multiphysics. The experimental setup includes a compact thermal storage-based greenhouse dryer (1.5 m × 1.0 m x 0.5 m) equipped with a black gravel-covered Aluminium jacket and 35 kg of paraffin wax for heat retention which is located on the floor of the dryer. The experiments were conducted in Ranchi, India (23.34 °N, 85.30 °E) under clear sky conditions in the month of May. The amount of solar radiation (global solar radiation) varied from (630 W/m2 to 1052 W/m2) with an average of 936 W/m2, ambient air temperature (30.2 °C–38.2 °C), air relative humidity (31.6 %–34.6 %), and wind speed (0.9–1.0 m/s). The inside dryer temperature, humidity, wind speed, and floor temperature were also measured every hour. The average values of these parameters were 59.1 °C, 30.2 %, 0.91 m/s, and 69.1 °C, respectively. The FE (finite element) modelling finds out the maximum temperature in drying products, floor and dryer's outlet is 55.3 °C,72.4 °C and 67.4 °C, respectively at 13:00 h. The proposed dryer costs 19633.50 INR with an embodied energy of 1358.01 kW h. The proposed dryer has a break-even period of 1.87 years, and its lifespan is 35 years. During this time, the net CO2 emission was found to be 21.45 tonnes, and the earned carbon credit varies from 1505.01 to 30030.00 INR. The result shows that the drying efficiency is 42.52 %, reducing the initial moisture content from 88.64 % to 2.28 % within five consecutive hours. The energy and exergy efficiencies of the dryer are found to be 61.84 % and 56 % respectively. The system is a viable, sustainable choice for the large-scale production of bitter gourd flakes.
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•A Comprehensive investigation of bitter gourd drying using an active greenhouse dryer.•Analyzing temperature variations and assessing moisture removal efficiency.•Evaluating 12 mathematical models to determine the best fit for drying.•Utilizing FE Modeling to improve drying processes and understand thermal behaviour.•Promoting the development of sustainable and energy-efficient drying technologies.
A reliable model for predicting wheel wear that considers the interaction between an abrasive block and a wheel as well as the contact between the wheel and rail is developed. First, a wheel wear ...prediction model that integrates vehicle system dynamics and the Archard wear model for wheel–rail interactions is developed. The wheel wear prediction procedure is validated using measured wheel profiles without the influence of abrasive blocks. Second, a new wheel wear prediction model that integrates the previously validated wheel wear prediction model, a finite element method, and a modified Archard wear model for abrasive block–wheel interactions is developed. The new method for predicting wheel wear is validated using the measured data with acting abrasive blocks. The results show that the tread wear rate due to wheel–rail contact is approximately 0.057 mm/104 km and that the tread wear rate due to abrasive block–wheel and wheel–rail contact is approximately 0.070 mm/104 km at a continuous air pressure of 3.0 bar.
•Wheel wear with two types of working schemes of abrasive blocks was measured.•A wheel wear prediction model under the effect of abrasive block was established.•The evolution process of wheel profiles is analyzed in-depth.•The wear coefficient between the abrasive block and the wheel is determined.
We established a three-dimensional (3D) multifilament finite element model for Bi-2212 round wire under axial load and analyzed its mechanical behavior. The model considered the initial thermal ...residual stress and damage of Bi-2212 superconducting filaments. The proposed model accurately predicted the axial mechanical behavior of strands. In addition, the characteristics of hysteresis loops in the stress–strain curves of Bi-2212 high-temperature superconducting (HTS) round wire under axial cyclic load were also obtained, agreeing well with experimental data. We constructed a 3D multifilament finite element model and 3D homogenized finite element model of a Bi-2212 HTS triplet. Both the results predicted by multifilament finite element model and homogenized model are close to the experimental data. The former gave more accurate stress distribution characteristics of strands than the latter. However, the homogenized model maybe more suitable for modeling of higher-level cables than the triplet model because of its lower computational cost.
