Experimental Study on the Axial Compression Performance of Bamboo Scrimber Columns Embedded with Steel Reinforcing Bars

In this paper,a new type of bamboo scrimber column embedded with steel bars(rebars)was proposed,and the compression performance was improved by pre-embedding rebars during the preparation of the columns.The effects of the slenderness ratio and the reinforcement ratio on the axial compression performance of reinforced bamboo scrimber columns were studied by axial compression tests on 28 specimens.The results showed that the increase in the slenderness ratio had a significant negative effect on the axial compression performance of the columns.When the slenderness ratio increased from 19.63 to 51.96,the failure mode changed from strength failure to buckling failure,and the maximum bearing capacity decreased by 43.03%.The axial compression performance of the reinforced bamboo scrimber columns did not significantly improve at a slenderness ratio of 19.63,but the opposite was true at slenderness ratios of 36.95 and 51.96.When the reinforcement ratio increased from 0%to 4.52%,the bearing capacity of those with a slenderness ratio of 51.96 increased by up to 16.99%,and the stiffness and ductility were also improved.Finally,based on existing specifications,two modification parameters,the overall elastic modulus Ec and the combined strength fcc,were introduced to establish a calculation method for the bearing capacity of the reinforced bamboo scrimber columns.The calculation results were compared with the test results,and the results showed that the proposed calculation models can more accurately predict the bearing capacity.

Compression Mechanical Performance Simulation and Parameter Optimization of Degradable Ureteral Stent Based on ABAQUS

The compression performance of a degradable ureteral stent is analyzed and the parameters are optimized by a finite element modeling method.The degradable ureteral stent explored in this paper is developed from poly(glycolic acid)(PGA)and poly(lactic-co-glycolic acid)(PLGA)degradable materials.Based on the actual measurement of fabric structure parameters,the three-dimensional model of the stent is established with the help of the modeling software.The finite element analysis software is used to simulate the compression process of the degradable ureteral stent.The parameters of materials,interactions and boundary conditions are set according to the compression environment of the stent for modeling and simulation.On this basis,the friction coefficient of yarns,the yarn radius,and the braided angle of the stent are further compared.The comparison test is carried out by a single variable.The experimental results show that the change of yarn friction coefficient has little influence on the compressive stress,while the yarn radius and the braided angle of the stent have a great influence on the compressive stress.

Compressive Performance of Fiber Reinforced Recycled Aggregate Concrete by Basalt Fiber Reinforced Polymer-Polyvinyl Chloride Composite Jackets

The development of recycled aggregate concrete(RAC)provides a new approach to limiting the waste of natural resources.In the present study,the mechanical properties and deformability of RACs were improved by adding basalt fibers(BFs)and using external restraints,such as a fiber-reinforced polymer(FRP)jacket or a PVC pipe.Samples were tested under axial compression.The results showed that RAC(50%replacement of aggregate)containing 0.2%BFs had the best mechanical properties.Using either BFs or PVC reinforcement had a slight effect on the loadbearing capacity and mode of failure.With different levels of BFs,the compressive strengths of the specimens reinforced with 1-layer and 3-layer basalt fiber reinforced polymer(BFRP)increased by 6.7%–10.5%and 16.5%–23.7%,respectively,and the ultimate strains increased by 48.5%–80.7%and 97.1%–141.1%,respectively.The peak stress of the 3-layer BFRP-PVC increased by 42.2%,and the ultimate strain improved by 131.3%,relative to the control.This reinforcement combined the high tensile strength of BFRP,which improved the post-peak behavior,and PVC,which enhanced the structural durability.In addition,to investigate the influence of the various constraints on compressive behavior,the stress-strain response was analyzed.Based on the analysis of experimental results,a peak stress-strain model and an amended ultimate stress-strain model were proposed.The models were verified as well;the result showed that the predictions from calculations are generally consistent with the experimental data(error within 10%).The results of this study provide a theoretical basis and reference for future applications of fiber-reinforced recycled concrete.

Coarsening Behavior ofγ′Precipitates and Compression Performance of Novel Co-Ni-Al-W Superalloy

The coarsening behavior ofγʹprecipitate phase at different temperatures and the compressive performance of novel Co-Ni-Al-W superalloy were investigated.Experiment results show that the evolution of the mean radius and volume fraction of theγʹphase obeys the classical Lifshitz-Slyozov-Wagner model.The coarsening rate of theγʹphase exhibits a significant dependence on the aging temperature,which increases from 1.30×10^(−27)m^(3)/s at 800℃to 9.56×10−27 m^(3)/s at 900℃.The activation energy ofγʹphase is mainly influenced by the W diffusion in theγmatrix,presenting as 210 kJ/mol.The prepared Co-Ni-Al-W alloy possesses superb comprehensive properties,particularly the good combination of highγʹsolvus temperature(1221℃)and low density(8.7 g/cm^(3)).Besides,the compressive yield strength of the Co-Ni-Al-W alloy at ambient and high temperatures are higher than that of otherγʹ-strengthened Co-based superalloys.The compressive yield strength of the Co-Ni-Al-W alloy at 850℃is as high as 774 MPa.

Effects of cell wall property on compressive performance of aluminum foams

The effects of cell wall property on the compressive performance of high porosity, closed-cell aluminum foams prepared by gas injection method were investigated. The research was conducted both experimentally and numerically. Foam specimens prepared from conditioned melt were tested under uniaxial compressive loading condition. The cell wall microstructure and fracture were observed through optical microscope（OM） and scanning electron microscope（SEM）, which indicates that the cell wall property is impaired by the defects in cell walls and oxide films on the cell wall surface. Subsequently, finite element（FE） models based on three-dimensional thin shell Kelvin tetrakaidecahedron were developed based on the mechanical properties of the raw material and solid material that are determined by using experimental measurements. The simulation results show that the plateau stress of the nominal stress-strain curve exhibits a linear relationship with the yield strength of the cell wall material. The simulation plateau stress is higher than the experimental data, partly owing to the substitution of solid material for cell wall material in the process of the establishment of FE models.

Effect of Ti content on microstructure and mechanical properties of CuCoFeNi high-entropy alloys

We prepared(CuCoFeNi)Tix(x=0,0.2,0.4,0.6,0.8,and 1.0)high-entropy alloys(HEAs)by vacuum arc melting and then investigated the effects of Ti on their microstructure and mechanical properties.When x was inreased to 0.6,the structure of the alloy transformed from their initial single face-centered cubic(fcc)structure into fcc+Laves mixed structure.The Laves phase was found to comprise Fe2Ti and be mainly distributed in the dendrite region.With increasing Ti content,both the Laves phase and the hardness of the alloy increased,whereas its yield and fracture strengths first increased and then decreased,reaching their highest value when x was 0.8.The(CuCoFeNi)Ti0.8 alloy exhibited the best overall mechanical properties,with yield and fracture strengths of 949.7 and 1723.4 MPa,respectively,a fracture strain of 27.92%,and a hardness of HV 461.6.

Fabrication and Statics Performance of Pyramidal Lattice Stitched Foam Sandwich Composites

In this study,the pyramidal lattice stitched foam sandwich composite materials were manufactured by integrating top and bottom panels with pyramidal lattice core to overcome the weak interface between the core and the skins of the sandwich structure.The influence of the reinforcing core rods on the mechanical properties including compressive,shear,and three-point bending performances of the foam sandwich compositematerialswere revealed through theoretical analysis and comparative experiments.The theoretical predictions were consistent with the experimental results.Compressive test,shear test and three-point bending test were performed.The experimental results show that the core rods can significantly improve the compressive performance and energy absorption efficiency of the pyramidal lattice stitched foam sandwich structure.The effect is related to the diameter of the core rod.The core rod with large diameter has better effect.Compared with the foamsandwich structure,the pyramidal lattice reinforcing foam composites have stronger shear and bending resistance.The failure modes and failure mechanisms of the pyramidal lattice stitched foam sandwich structure under the shear load are given.The failure modes and failure mechanisms of the pyramidal lattice stitched foam sandwich structure under the three-point bending load are also given.The study concludes that compared with the foam sandwich structure,the overall mechanical properties of the lattice stitched foam sandwich structure composites are significantly improved.

Performance enhancement of sandwich panels with honeycomb–corrugation hybrid core

The concept of combining metallic honeycomb with folded thin metallic sheets （corrugation） to construct a novel core type for lightweight sandwich structures is proposed. The honeycomb-corrugation hybrid core is manufactured by filling the interstices of aluminum corrugations with precision-cut trapezoidal aluminum honeycomb blocks, bonded together using epoxy glue. The performance of such hybrid-cored sandwich panels subjected to out-of-plane compression, transverse shear, and three-point bending is investigated, both experimentally and numerically. The strength and energy absorption of the sandwich are dramatically enhanced, compared to those of a sandwich with either empty corrugation or honeycomb core. The enhancement is induced by the beneficial interaction effects of honeycomb blocks and folded panels on improved buckling resistance as well as altered crushing modes at large plastic deformation. The present approach provides an effective method to further improve the mechanical properties of conventional honeycomb-cored sandwich constructions with low relative densities.

Rock excavation using surface miners: An overview of some design and operational aspects

Surface miner, a continuous mining machine, is being manufactured in India and abroad owing to enhanced demand of production in various mining industries like coal, limestone, gypsum, bauxite etc. Different types of surface miners are manufactured today based on cutting drum placement and design specifications. Selective mining without drilling and blasting, high production and small size products are some of the prominent attractive features obtained with these moving marvels. This machine can be used with good efficiency in soft to medium hard rock (100-120 MPa). This paper synthesizes the different applications, equipment models, features offered, operating methods, cutting performance assessment models as well as typical production performance of surface miner in coal and limestone mines of India. Engine hour metre reading, diesel and pick consumptions are linearly influenced by production. The emphasis for future research is also brought out.

A Simple Mix Proportion Design Method Based on Frost Durability for Recycled High Performance Concrete Using Fully Coarse Recycled Aggregate

Durability design of recycled high performance concrete（RHPC） is fundamental for improving the use rate and level of concrete waste as coarse recycled aggregate（CRA）. We discussed a frostdurability-based mix proportion design method for RHPC using 100 % CRA and natural sand. Five groups of RHPC mixes with five strength grades（40, 50, 60, 70 and 80 MPa） were produced using CRA with four quality classes, and their workability, 28 d compressive strengths and frost resistances（measured by the compressive strength loss ratio and the relative dynamic modulus of elasticity） were tested. Relationships between the 28 d compressive strength, the frost resistance and the CRA quality characteristic parameter, water absorption, were then developed. The criterion of a CRA maximum water absorption limit value for RHPC was suggested, independent of its source and quality class. The results show that all RHPC mixes achieve the expected target workability, strength, and frost durability. The research results demonstrate that the application of the proposed method does not require trial testing prior to use.

A novel cylindrical sandwich plate inspired by beetle elytra and its compressive properties

The design and experimental analysis of a semi-cylindrical structure known as the cylindrical beetle elytron plate(CBEP)were presented.Radial compression tests and finite element simulation were performed on CBEPs under 30°and 45°inclined sliding support constraints,with a comparison made to cylindrical honeycomb plate(CHP).The study aims to investigate the superior compression performance and enhancement mechanisms of CBEPs.The results demonstrate that CBEPs exhibit a 14%–26%increase in specific load-bearing capacity and a 20%increase in specific energy absorption compared with CHPs with equal core wall thickness.Distinct“Z-shaped”tearing failures were observed,with honeycomb plates showing tearing at the center of the honeycomb walls,while beetle elytron plates exhibited tearing along the midline of the trabeculae.Three different stress patterns,including elastic-plastic development stage of arch,plastic hinge node stage,and rigid node stage,were identified and analyzed to explain the mechanical performance improvements and failure characteristics.Considering that structural damage to trabeculae mostly occurs at its junction with the skin,it is recommended to add chamfers to the junctions of CBEP.Therefore,this paper lays the groundwork for the engineering application of CBEP.

Compression behavior of metal foams with real pore structures through CT scan images

Based on the real pore structure obtained from computed tomography(CT)scan images,a three-dimensional(3D)model of the metal foam sample with specified porosity is established,and the model is compressed and simulated by finite element method with the simulation results compared with the experimental test results for validation.At the same time,based on the spatial distribution characteristics of cells extracted from 3D model construction,a widely used metal foam model with Voronoi pore structure or spherical pore structure was established and simulated under compression.The two compression simulation results with regular pore structure models were also compared with the experimental results and CT model results to study the influence of cell wall morphology on the compression performance of metal foams.The simulation results show that CT model agrees well with the experimental results and is more accurate than Voronoi pore or spherical pore model,which can provide a more reasonable option for investigation of metal foams.

Efficient Partitioning Method for Optimizing the Compression on Array Data

Array partitioning is an important research problem in array management area,since the partitioning strategies have important influence on storage,query evaluation,and other components in array management systems.Meanwhile,compression is highly needed for the array data due to its growing volume.Observing that the array partitioning can affect the compression performance significantly,this paper aims to design the efficient partitioning method for array data to optimize the compression performance.As far as we know,there still lacks research efforts on this problem.In this paper,the problem of array partitioning for optimizing the compression performance(PPCP for short)is firstly proposed.We adopt a popular compression technique which allows to process queries on the compressed data without decompression.Secondly,because the above problem is NP-hard,two essential principles for exploring the partitioning solution are introduced,which can explain the core idea of the partitioning algorithms proposed by us.The first principle shows that the compression performance can be improved if an array can be partitioned into two parts with different sparsities.The second principle introduces a greedy strategy which can well support the selection of the partitioning positions heuristically.Supported by the two principles,two greedy strategy based array partitioning algorithms are designed for the independent case and the dependent case respectively.Observing the expensive cost of the algorithm for the dependent case,a further optimization based on random sampling and dimension grouping is proposed to achieve linear time cost.Finally,the experiments are conducted on both synthetic and real-life data,and the results show that the two proposed partitioning algorithms achieve better performance on both compression and query evaluation.

Experimental study on the compressive performance of new sandwich masonry walls

Sandwich masonry wall,namely,multi-leaf masonry wall,is widely applied as energy-saving wall since the interlayer between the two outer leaves can act as insulation layer.New types of sandwich walls keep appearing in research and application,and due to their unique connection patterns,experimental studies should be performed to investigate the mechanical behavior,especially the compressive performance.3 new types of sandwich masonry wall were investigated in this paper,and 3 different technical measures were considered to guarantee the cooperation between the two leaves of the walls.Based on the compression tests of 13 specimens,except for some damage patterns similar with the conventional masonry walls,several new failure patterns are found due to unique connection construction details.Comparisons were made between the tested compression capacity and the theoretical one which was calculated according to the Chinese Code for Design of Masonry Structures.The results indicate that the contributions of the 3 technical measures are different.The modification coefficient(γ)was suggested to evaluate the contribution of the technical measures on the compression capacity,and then a formula was proposed to evaluate the design compression capacity of the new sandwich masonry walls.

Theoretical bounds on Fresnel compressive holography performance(Invited Paper)

During the last years the theory of compressive sensing has found significant utility in the digital holography realm. In this letter we summarize and extend our previous theoretical results which determine the relation between the number of Fresnel samples required on the object illumination type, illumination wavelength, imaging geometry and sensor＇s size and resolution.