High Structural Strength Research Articles

Ultra-compact metafence to block and channel mechanical waves

Wave steering by artificial materials (for example, phononic crystals and acoustic metamaterials) is a fascinating frontier in modern physics and engineering, but suffers from bulky sizes and intractable challenges in fabrication. A sparse layer of identical tiny scatters, which we call metafence, is presented here in a non-destructive way to omnidirectionally block and arbitrarily channel flexural mechanical waves in plates. The underlying mechanism is that the restraining force and moment of the scatter are tuned simultaneously to counter-balance the incident wave. Both our experimental results and numerical analysis have demonstrated that broadband wave sources ranging from 3 to 7 kHz can be segregated from the protected area by the metafence. The metafence is also assembled into a waveguide routing with an arbitrary configuration. Compared with previous isolators and waveguides, our metafences exhibit absolute advantages in compact size, flexible configuration, and high structural strength. The current scenario sheds light on the design of lightweight-and-strong architectures for vibration control and energy harvesting with a high efficiency, and can be extended to microfluidics, acoustics, seismology and other fields.

Composite-inspired multilattice metamaterial structure: An auxetic lattice design with improved strength and energy absorption

Mechanical metamaterials with two-phase lattice structures have recently been explored to enhance the mechanical properties of the constituent lattices. In this work, novel dual-phase lattice structures, named as ‘multilattice’ structures, are designed and fabricated by mimicking particle and fiber reinforced composite materials. The 3D reentrant auxetic lattice, that exhibits negative Poisson’s ratio, is used as the matrix and body-centered-tetragonal lattice with vertical struts (BCTZ), having high stiffness and high strength, is used as reinforcements. The mechanical response and deformation mechanics of the multilattice structures are investigated by numerical simulations and quasi-static compression tests. Due to the presence of BCTZ reinforcements, the multilattice structures exhibit superior strength and stiffness than the parent 3D reentrant lattice without compromising the negative Poisson’s ratio behavior. Moreover, the influence of volume fraction and type of the reinforcements on the mechanical properties of the multilattice structures are also studied. The multilattice structures exhibit higher densification strain and post yield hardening that lead to higher energy absorption than the parent auxetic lattice. Elastic moduli and Poisson’s ratios of the multilattice structures are in good agreement with the predictions obtained from the conventional rule of mixture used for composite materials. This study suggests that the strength, stiffness, energy absorption and Poisson’s ratio of multilattice structures can be tailored as per the requirement of load bearing applications and energy absorbing applications. The continuous fiber-reinforced multilattice (CFRM) can be useful for high strength structures while the particle-reinforced multilattice (PRM) is more appropriate for high energy-absorbing structures.

Local ionic structure unit design in sulfide solid electrolyte flakes by improving pressing process

The rapid development of electric vehicles and energy storage facilities requires novel secondary batteries with higher energy density and increased safety. Sulfide solid electrolyte, especially lithium thiophosphate (LPS), has become a research hotspot due to its non-flammability and high structural strength. The high-performance LPS powders need to be prepared into flakes before practical application. However, the widely used cold pressing process for the preparation of LPS flakes have fatal defects such as low density and high interface resistance. This work systematically studied the differences in the body defects, density and crystallization process of electrolyte flakes obtained by different tableting processes. The nucleation is inhibited in the high-density sulfide solid electrolyte samples. In addition, based on the improvement of pressurizing equipment, it was discovered for the first time that glass transition process (the secondary hot pressing at glass transition temperature) can significantly improve the distribution of local structured ions. Notably, the content of P2S74- and P2S64- has doubled after glass transition, resulting in improving the ionic conductivity and stability, respectively. The HP-GT (the electrolyte flakes after glass transition) exhibits extremely high relative density (99 ± 1%), low ion activation energy (14.4 kJ/mol) and extremely high ion conductivity (3.48 mS/cm). On the other hand, a specific discharge capacity of ∼ 680 mAh g−1 is still maintained for the Li|HP-GT|MoS2 solid-state battery after 30 cycles. This work confirms the feasibility of the sulfide solid electrolyte after the second hot-pressing in the application of high-safety, high-energy density solid-state lithium batteries.

Flexible Probe With Array Tunneling Magnetoresistance Sensors for Curved Structure Inspection

The 3-D curved structures are widely used in industries due to their advantages of flowing geometry, high structural strength, and excellent aerodynamic performance. Damages may occur in curved structures during manufacture or use, which may endanger the equipment’s operation safety. Efficient tools for inspection of buried defects in curved structures are still lacking. This article proposes a flexible nondestructive testing probe with tunneling magnetoresistance (TMR) sensors for inspecting buried defects in curved structures for the first time. The probe contains 16 TMR sensors and the distance between each 2 adjacent sensors is 2 mm. The TMR sensors are fetched from a customized wafer and screened to guarantee the consistency. In this probe, the TMR sensors are wire bonded on a flexible printed circuit board and then protected by polyurethane pouring sealant. The probe can be bent to fit an irregular surface with minimum bending radius 5.5 mm. The selection of the excitation frequency and the proposed probe performance for buried defects’ inspection are studied using a 3-D finite-element numerical model. Experimental results demonstrate that defects buried 3 mm below the top surface of cylindrical samples can be accurately detected. A chromatic confocal distance sensor is employed to sketch the curved surface of an irregular shaped sample. The electromagnetic image and optical image of this sample with curved surface are plotted in a fused image, which presents comprehensive information of the sample about both the structural pattern and the buried defects’ indications.

Enhanced High-Temperature YSZ-polyester Abradable Honeycomb Seal Structures.

The abradable coatings had significantly enhanced turbomachinery performance by acting as a sacrificial seal between rotating blades and stationary casing. Further improvement in seal design to meet the higher energy demand and increase the service time has been the key challenge to solve in the gas turbine industry. Honeycomb seals have become the industry standard clearance seal technique due to their unique design and high structural strength with minimum weight. The present study proposes a concept to form a thermal shock resistance structure to achieve higher temperature capability and improve the reliability of high-temperature abradable seal structures for a hot gas path of turbines. A cavity layer of honeycomb seal structure made of SS 321 alloy was coated with advanced high-temperature ZrO2 + 7.5%Y2O3 + 4% polyester seal material using TriplexPro-210 plasma spray system. The integrity of a seal structure was assessed by a cross-sectional analysis and evaluation of the coating microstructure. Additionally, the micro-hardness test was performed to estimate coating fracture toughness, and finite element analysis was used to assess its thermo-mechanical performance. The concept proposed in this study should be further validated to develop the most capable innovative technology for advanced gas turbine abradable seal structures.

Promising light crack-resistant armor obtained using explosion welding technology

An analysis of the state of the development of modern light metal armored materials for the manufacture of armored vehicles, aviation equipment, combat robots and personal protective equipment was carried out. The perspective of producing multilayer metal armor materials by explosion welding combining high bullet resistance and structural strength along with low specific gravity is shown. A new composite reinforcement scheme has been developed that allows localizing the development of brittle cracks along interlayer boundaries with external ballistic impact on the object.

Optimization of 1U nanosatellite on the basis of strength and weight using different Materials: A numerical approach

As the intricacy of problems encountered increases, humans need to explore space, hence demanding more experiments to be performed at different physical conditions. Nanosatellites are not only cheap and flexible but they are also validated in space which can be used as extensions for the larger satellites for more wider applications. The materials chosen for space applications are based on their properties, costs and complexity. Some of the materials that are used include, metal and its alloys, fiber composites. Out of these, aluminum and its alloys such as, Al 7075 – T6, are widely used for spacecraft manufacturing. Due to certain disadvantages of aluminum, there is an increase in the research and development of composite materials such as, HTM143/M55J and T300/5208, are used for space applications because they offer high structural strength in comparison to metallic alloys, but at a lighter weight which improves fuel efficiency and performance. The main objective of the research is to provide a comprehensive description and comparative study of the materials that can be used in improving the structural design and weight of the nanosatellite. Static structural analysis was carried out to analyze the feasibility of using composites as an alternative to metallic alloys on the basis of stress and deformation value. The material HTM143/M55J shown major improvement in the weight and strength ratio as compared to other two materials.

Research on High Structural Strength MEMS S & A Device for Micro Initiator

Research on High Structural Strength MEMS S & A Device for Micro Initiator

Enhance interfacial deposition kinetics to achieve dendrite‐free zinc anodes by graphene oxide modified boron nitride nanosheets

Aqueous zinc (Zn)-ion hybrid supercapacitors (ZIHCs) exhibit great potential for large-scale energy storage applications due to the merits of environmental friendliness, and low redox potential of Zn anode. However, the original Zn anodes still suffered from electrochemical performance deficiency caused by dendrite formation and side reactions. In this work, an artificial interface of graphene oxide modified boron nitride (GOBN) nanosheets was rationally designed and utilized to regulate Zn ion transmission rate and constrain the side reaction with electrolyte. Results demonstrated that the as-established interlayer could effectively suppress Zn dendrite growth during cycling, benefiting from the high mechanical strength and nanosheet-built hierarchical structure of GOBN. The GOBN@Zn symmetric cell enables a long-term working life of 1000 h under 1 mAh•cm−2 with a low plating/stripping overpotential of ∼50 mV. Accordingly, the strategy of establishing GOBN interlayer endows the Zn anode with an ultra-long cycling lifetime by providing effective protection along with fast kinetics.

Fracture prediction in transverse fillet welded joints of high strength structural steel

Due to the huge property difference between high strength structural (HSS) steels and mild steels after welding, mechanical behavior and failure mode of fillet welded joints of HSS steels should be studied further. Numerical simulations can provide increased insight into this topic. This paper concerns finite element simulations of component tests of two types transverse fillet welded joints of HSS steels: lap-welded transverse fillet welds and cruciform type transverse fillet welds. In order to investigate the influences of triaxial stress states on fracture ductility of weld metals, a series of tests on specimens with various initial geometries are carried out. By comparing three typical uncoupled fracture models (stress triaxiality-dependent ductile fracture model (VGM), Lode angle-dependent ductile fracture model (MSSM) and combination of stress triaxiality and Lode angle ductile fracture model (BWM)), BWM gives precious prediction of ductile fracture of weld metals. The behaviors in terms of load-displacement and failure modes of transverse fillet welds are all well captured by the numerical simulations with calibrated ductile fracture models. Specifically, the location of fracture initiation and propagation of cracks obtained from simulations are both identical with real responses.

Preparation of geopolymer based on lunar regolith simulant at in-situ lunar temperature and its durability under lunar high and cryogenic temperature

Lunar base construction is of great importance for deep space exploration, and the establishment of lunar pavements for the movement of machinery and transportation of materials is essential to improve construction efficiency. Lunar regolith as an in-situ resource has been demonstrated to be used as raw materials to prepare geopolymers for lunar pavements. In this paper, geopolymers based on lunar regolith simulant with different concentrations of alkali activator were synthesized using the natural high-temperature of the lunar surface. Then, the durability of the resulting geopolymer under lunar high and cryogenic temperature was investigated. The flexural and compressive strength was tested, and the microstructure was characterized using Scanning Electron Microscope coupled with Energy Dispersive Spectroscopy (SEM-EDS), 29Si Magic Angle Spinning-Nuclear Magnetic Resonance (29Si MAS-NMR), and Mercury Intrusion Porosimetry (MIP). The results of the curing section showed that the geopolymer with 8 mol/L sodium hydroxide (NaOH) generated high strength and dense structure, and the period of 420 h–492 h of a lunar day corresponding to a temperature variation from 84.5 °C to 33.5 °C in 72 h was suitable for preparation, with 5.7 MPa and 31.2 MPa 72-h flexural and compressive strength. Three test points were selected on the lunar 30° latitude temperature curve, corresponding to before and after the cryogenic attack, and after high temperature again to investigate the durability of the geopolymer, and the degradation was found noticeable. The flexural strength decreased about 49% and 70%, and the compressive strength decreased about 15% and 18% after the cryogenic temperature and high temperature again, respectively. Microscopic observations revealed that the geopolymer structure was significantly granulated with obvious cracks and increased porosity. In addition, the formation of the zeolitic phase was unexpectedly found, leading to interfacial cracks and mechanical strength reduction of the geopolymer. This paper will be beneficial to explore the evolution of properties of lunar pavement construction materials in the lunar environment.

X-ray diffraction of concrete composites of high structural strength and density

Аn analysis of the structure formation of concrete composites, compressive strength of which exceeds 120 MPa and a quantitative analysis of their qualitative composition and hydration products by X-ray diffraction, x-ray spectral analysis. The main factors affecting the physicomechanical parameters of the complex of various nanofillers and the formation of a denser cement stone structure, which mainly includes calcium hydrosilicates, calcium silicate hydroaluminates and hydroaluminates of various basicity, are studied.

Effects of gravel content and shape on shear behaviour of soil-rock mixture: Experiment and DEM modelling

The soil-rock mixture (SRM) is an excellent composite filler for subgrade, due to its renewable sources and high structural strength. It is still a challenge to evaluate the impact of gravel content (GC) and gravel shape on the shear behaviour of SRM in pavement engineering, due to the complex and uncontrollable microstructure of SRM. Thus, the aims of the study were: (i) to experimentally analyze the influence of GC and shape distribution of limestone and basalt gravels on shear strength of SRM at various stress conditions; and (ii) to numerically investigate the difference of mesoscale characteristics between SRM models considering irregular shape and proportion by discrete element method (DEM). The test results in the laboratory showed that the Gray correlation of gravel shape on shear strength was greater than that of GC. The numerical results showed that the developed DEM model could accurately predict the mechanical properties and deformation behavior of SRM. As GC increased, the contribution of contact force within gravel particles increased. Meanwhile, the interlocking work had a nonlinear positive correlation with the increase of sphericity. This study implied that morphological characteristics of gravel should be paid more attention to during the design of the SRM subgrade.

Experimental study on an oil‐based polymer gel for lost circulation control in high‐temperature fractured formation

AbstractAiming at the lack of plugging agent for oil‐based drilling fluid leakage in fractured formation, an oil‐based gel‐plugging agent with high structural strength and strong thermal stability was synthesized based on monomer polymerization and crosslinking. According to the preparation experiment, when the total concentration of methyl methacrylate (MMA) and butyl acrylate (BA) is 30% and the ratio is 6:4, the oil‐based gel solution can be completely gelatinized from 80 to 200°C, which has high gel strength and controllable gelation time. The effects of total concentration of BA and MMA, the ratio of BA and MMA, synthesis temperature, oil‐based drilling fluid invasion, shear effect, and fiber concentration on gelling performance were systematically studied. Fourier transform infrared molecular structure analysis showed that the oil‐based gel contained benzene ring group and ester characteristic group. From the rheological properties of oil‐based gel with 30% gelling agent at 160°C, it could be seen that the elastic modulus G′ of 10 Hz is 232 kPa, which is much larger than the storage modulus G″ is 99 kPa, which reflects the solid properties and has good elasticity and high strength. The displacement experiment of sand filling pipe and dynamic and static plugging experiment of high temperature and high pressure shows that the oil‐based gel has high bearing capacity in fractures and sand filling pipe. The bearing pressure is 3.01 MPa in 6 mm fractures, and the bearing pressure gradient is 0.602 MPa/cm.

Elastic gels based on flaxseed gum with konjac glucomannan and agar.

In this study, we prepared hydrocolloid gels in which flaxseed gum (FSG), konjac glucomannan (KGM), and agar (AG) were blended in different ratios for use as a viscoelastic food. The prepared hydrogels' physicochemical properties were analyzed concerning their water solubility index (WSI), swelling power (SL), frequency sweep results, and microstructures. As the FSG ratio decreased, the WSI value of the compound gel tended to increase. However, it showed a tendency to have a relatively high SP value and a low tan δ value according to a specific KGM/FSG/AG mixing ratios (8:2:1.5 and 6:4:1.5). Through microstructure analysis, the FKA821.5 sample showed a relatively small, monodispersed gel building structure, correlated with the rheological results. In conclusion, the FKA821.5 gel was determined to have good water retention capacity and high structural strength. These results are expected to increase the applicability of FSG-based gelling agents in the food industry.

Investigation on the ballistic performance of rubber-aluminum (AA7075-T651) laminated plates reinforced with borosilicate glass balls

In this study, the ballistic behavior of protective armor plates (PaP) obtained by curing between high structural strength AA7075-T651 aluminum plates by reinforcing with glass balls of two different rubber mixtures whose damping properties were developed with carbon nanotube and glass bubbles fillers were investigated. A total of six PaPs at 27, 30, and 35 mm heights were prepared using two different matrix damping rubbers. High-strength liner rubber used in air bellows is vulcanized on the front and back surfaces of PaPs. Between the PaPs, Ø15.875 and Ø6.747 mm, borosilicate glass balls were placed in a particular arrangement that coincides with the middle of the matrix rubber and does not have any gaps. Liner rubber cured on the front face has managed to hold the energy by forming a layer like clothing around the bullet cores. Glass balls between PAPs play an essential role in the energy absorption of GB-filled mixtures. In contrast, in MWCNT-filled mixtures, they act as a second damping element. The ballistic performance of PAPs prepared with multiwalled carbon nanotubes was determined to be better than those prepared with Glass Bubbles. Thanks to the superior mechanical properties and high aspect ratio of MWCNTs, the penetration and swelling heights of the matrix damping rubbers prepared to have excellent results compared to glass bubbles. With the increase in the thickness of the PaPs prepared with MWCNTs, the deformation effect of the penetration depth and bulging height created by the bullet on the anterior and posterior surfaces decreased. As the thickness of PaP increased from 27 mm to 35 mm, penetration depth decreased by 38%, and bulging height reduced by 35%. The amount of penetration and swelling increased in PaPs using rubber filled with glass bubbles. As the plate thickness increased, the damping feature decreased and the glass balls were activated, and the bullet was stopped.

Application of microbial induced carbonate precipitation for loess surface erosion control

China is one of the countries with the most serious soil erosion disaster, especially in Loess Plateau region. A new strategy for loess surface erosion control using MICP technology in terms of spraying was proposed. The feasibility, mitigation mechanism and the effects of MICP treatment cycle and cementation solution (CS) concentration were investigated through the rainfall erosion test and penetration test. It is found that the proposed MICP technique shows the ability to mitigate the rainfall erosion of loess. Final accumulative soil erosion weight could reach a maximum reduction of 200 times after only 3 cycles of MICP spaying treatment and almost no soil loss was observed since 5 cycles of treatment. The mitigation mechanism can be attributed to the MICP induced double layer structure, namely the upper hard crust layer on soil surface and the lower weak cemented layer, which is attributed to the bonding effect of the precipitated calcium carbonate (CaCO3) between soil particles and the filling effect in pores. The high structure strength of the hard crust can resist the impact of raindrops as well as can resist runoff erosion. The low permeability of the hard crust effectively prevents the rainwater infiltration to soft the subsurface weak cemented layer and deep uncemented soil. With increasing MICP treatment cycles, the amount CaCO3 and the thickness of the hard crust layer increases accordingly, leading to higher soil structure strength and erosion resistance. The CaCO3 content generally decreases with increasing depth. It is also found that the loess treated by 1.0 M CS presents the highest CaCO3 content, hard crust layer thickness and soil structure strength as compare with the samples treated by 1.5 M and 0.5 M CS. Taking into account the overall effectiveness, efficiency and cost, 5 cycles of MICP treatment with 1.0 M CS is optimal for the mitigation of the rainfall erosion of the tested loess.

Analysis of the structure formation processes of building composites by geometric methods

The work considers a method of structure formation modeling in composite materials based on geometric methods. For this purpose, a differential system is written for the fractions of the volume, surface, linear and point phase of the structure forming components of the material. To study it, a decomposition into a gradient and generalized-conservative component was used. Approaches to modeling of the processes of structure formation and destruction based on the theory of gradient systems, which take into account the structural potentials for the surface and volumetric components of the composite material, were proposed. The hypothesis according to which the formation of a high-strength structure of the material is associated with the implementation of the oscillatory mode for the indicator of the fraction of the volumetric phase was proposed. The mechanism of increasing the strength of the composite binder dough based on the selective preservation of the strongest intercrystalline contacts was discussed.

Light and high-strength structure inspired by the characteristics of double-nutrient foramens in intertarsal joint of ostrich

The ostrich (Struthio camelus) is characterized by high speed and heavy load when running. Its intertarsal joint (Fig. 1A) with double-nutrient foramina (DNF) exhibits excellent ability to withstand high impact during running, and is characterized by lightweight. We investigated the effect of DNF on the biomechanical properties of the intertarsal joints of the ostrich. The intertarsal joint was reconstructed according to computed tomography images, and four models were established to uncover the separate and combined effects of the compositional parameters (geometric features, material properties) on stress concentration reduction. We have revised the formula that can be used to predict the elasticity modulus (E) of ostrich bones and verified the accuracy of the formula with nano-indentation equipment. The results were analyzed by t tests, and the p value is less than 0.05. The finite element analysis was performed to evaluate the mechanical properties of the PT and models. Compared to the Filled model (DNF was filled), the maximum stress at the lateral and medial fossa in the Initial model was reduced by 15.4%, although there was no significant difference in the medial maximum stress. Compared with the stress value of models without holes, the models with holes have lower stress, with a reduction of 4.0%. Reasonable design of holes can improve the efficiency of material utilization. This paper investigated the mechanism of high mechanical properties of the intertarsal joints of ostrich and developed four bionic-bearing parts based on the characteristics of DNF and heterogeneity materials, which may provide ideas for the design of aircraft and robot parts with lightweight and high strength.

A CFRP/PZT laminated piezoelectric motor with high force density

This work presents a laminated piezoelectric (PZT) motor to achieve high force density, high strength, and compact structure. The oscillator consists of vibration units and a driving foot. Each of the vibration units is formed by symmetrically bonding two PZT ceramics on a carbon fiber-reinforced plastic (CFRP) layer to improve its strength. The oscillator works in hybrid mode of the first longitudinal vibration (L1) and second bending vibration (B2). The finite-element method is adopted to tune the resonance frequencies of the two modes, and the vibration characteristics are experimentally analyzed. The strength test shows that the presence of the CFRP layer can increase the overall strength of the oscillator by 28% compared with a pure PZT motor. To evaluate the performance, the load characteristics of the fabricated prototype (with a size of 39 × 10 × 4.6 mm3 and weight of 10.6 g) are tested on a designed testbed. The single-phase driving method is used to drive the motor, and the best performance is obtained at the B2-mode frequency. The maximum thrust force, no-load speed, and output power reach 17 N, 335 mm s−1, and 775 mW, respectively, at a drive voltage of 100 Vp. Meanwhile, a thrust density of 1604 N kg−1 and an output power density of 73.11 W kg−1 are achieved. The thrust density is much higher than that of the other motors that operate in the same modes.