Axial Modulus Research Articles

Axial compression stress-strain relationship of lithium slag rubber concrete

Replacing cement with lithium slag and fine aggregate with rubber in concrete solves waste disposal, reduces material consumption, boosts sustainability, and enhances concrete performance. A set of prismatic concrete specimens with varying proportions were designed and experimentally tested in order to study the compressive stress-strain behavior of lithium slag rubber concrete (LSRC). The main factors affecting the specimens were lithium slag substitution ratio (SL=0%, 10%, 20%, 30%) and rubber substitution ratio (SR=0%, 5%, 10%, 15%). The results demonstrated that the LSRC exhibited good integrity during the damage. Furthermore, the incorporation of lithium slag (LS) was found to effectively compensate for the reduction in compressive strength due to the incorporation of rubber. When 10% of the fine aggregate was replaced with rubber and 20% of the cement was substituted with lithium slag, the axial compressive strength, elastic modulus, and peak strain of the tested specimens increased by 21.57%, 6.92%, and 17.26%, respectively. Compared with ordinary concrete, LSRC has good toughness, impact resistance and durability with minimal loss of strength, and has broad application prospects in engineering fields (such as airports, highways, housing expansion joints, concrete floors and railway concrete sleepers, etc.). Based on the experimental data, simplified modified equations to predict the compressive strength, elastic modulus, peak strain and axial stress-strain constitutive model of LSRC were proposed, so as to promote the development of LSRC.

Influence of Elastic Properties and Nodes on the Flexural Behaviour of Bamboo Culms

This study investigates the influence of elastic properties and nodes on the flexural behaviour of bamboo culms by comparing different characterization techniques and theoretical approaches. The most representative parts of the bamboo culm were selected using microscopic images of bamboo cross-sections. These were sliced from the bottom, middle, and top parts of a single culm and were analyzed with Digital Image Processing. Four-point bending tests were conducted on twelve culms of Phyllostachys aurea, subdivided into groups of untreated (UN) and heat-treated (HT) samples. The axial modulus of elasticity (Eb) and the shear modulus (G) were determined experimentally using four different mathematical models: (i) a global deflection model using the Euler-Bernoulli beam theory according to the ISO Standard; (ii) a global deflection model using the Timoshenko beam theory; (iii) a global deflection model based on the Timoshenko beam theory but accounting for the presence of nodes; and finally, (iv) a local model using extensometry. The dominant failure modes for UN and HT samples are described and discussed, and were influenced by the moisture content (MC). Approaches (i) and (ii) showed good agreement, giving reliable parameters to assess Eb. The third approach (iii) indicated that the nodes significantly influence the flexural behaviour of the culms. Approach (iv) was appropriate for determining G, but resulted in higher values of Eb, typically not representative of the material.

Enhancing Carbon Nanotube Yarns via Infiltration Filling with Polyacrylonitrile in Supercritical Carbon Dioxide.

Carbon nanotube (CNT) fibers are renowned for their exceptional axial tensile strength and modulus. However, in yarn form, they frequently encounter transverse loading in practical applications, which exposes their suboptimal mechanical attributes rooted in inadequate inter-tube interactions and yarn surface defects. Efforts to mitigate micro-slippage among CNTs have encompassed gap-filling methodologies with varied materials, yet the outcomes have fallen short of expectations. This work aimed to enhance the mechanical properties of CNT yarns via infiltration with polyacrylonitrile (PAN) under supercritical carbon dioxide (sc-CO2) conditions. PAN was strategically chosen for its capability to undergo pre-oxidation and subsequent carbonization, leading to robust graphitic reinforcement. Leveraging sc-CO2's swelling and high permeability properties, the infiltration process effectively plugged interstitial spaces, elevating the yarn's tensile strength to 277.50 MPa and Young's modulus to 5094.05 MPa. Additional enhancements were realized after pre-oxidation, conferring a dense, reinforced shell structure that augmented tensile strength by 96.93% and Young's modulus by 298.80%. Scanning electron microscopy (SEM) analyses revealed a homogeneous PAN distribution within the yarn matrix, corroborated by X-ray photoelectron spectroscopy (XPS) evidence of C-N bonding, indicative of a successfully interlaced network. Consequently, this investigation introduces a novel strategy to tackle micro-slippage in CNT yarns, thereby achieving substantial improvements in their mechanical resilience.

On the identification of the elastic modulus and axial force of beam members with unknown boundary conditions using modal information

The axial force of beam members with unknown boundary conditions can be estimated by using vibration measurements, and this method necessitates the real elastic modulus of the members to produce accurate estimations. However, in engineering practice, the value of the elastic modulus of such members differs from the designed value owing to material degradation and structural damage. In addition, the elastic modulus of the beam structure may have a significant impact on the identification accuracy of axial force. Therefore, this study develops a methodology for simultaneously estimating axial force and elastic modulus within axial force members of structural systems, based on measurements of multiple natural frequencies and mode shapes. First, an improved vibration formula for the Timoshenko beam under axial load is obtained using the energy approach. Then, based on the proposed dynamic equation, the axial force and elastic modulus of the beam are discovered to have a linear relationship when the modal information of the structure is known. Further, using this linear relationship, a method to identify the axial force and elastic modulus of the beam member under unknown boundary constraints is proposed. Finally, the applicability and accuracy of the proposed method are validated by many numerical and experimental tests, and excellent estimates of the axial forces and elastic modulus are achieved.

Effective mechanical behaviors of transverse isotropic materials containing compressible liquid inclusions with surface effects

Porous media with fluid-saturated microchannels, prevalent in biomaterials, tissue engineering materials and flexible electronic devices, can be modelled as transverse isotropic materials. Surface effects can influence significantly the macro-mechanical responses of such materials, particularly for soft materials with micro- or nano-scale channels. In this study, we first develop constitutive laws for fluid saturated porous materials with microchannels by integrating the top-down (homogenization) approach with the bottom-up (micromechanics) approach. We then explicitly establish a connection between surface effects and macro-mechanical responses. Employing the generalized self-consistent model (GSCM), we estimate the effective parameters (i.e., coefficients in constitutive equations governing macro-mechanical responses), with fluid compressibility and surface effects accounted for. Our findings reveal that, as surface energy increases, the effective transverse shear modulus is enlarged, the effective plane strain bulk modulus, the unit uniaxial straining modulus and the cross modulus are all reduced, but the axial shear modulus remains nearly unchanged. As an application, we characterize the mechanical behaviors of the transverse isotropic fluid-saturated porous material with surface effects by connecting the classic Mandel solution with the estimated effective parameters. The pore pressure exhibits the Mandel-Cryer effect. The insights gained from this study are valuable for comprehending and exploring the intricate ways in which surface effects influence the mechanical responses of transversely isotropic fluid-saturated porous materials featuring sufficiently small channels.

Thermal equation of state of Li-rich schorl up to 15.5 GPa and 673 K: Implications for lithium and boron transport in slab subduction

Abstract The thermal equation of state (EoS) of natural schorl has been established at high temperatures up to 673 K and high pressures up to 15.5 GPa using in-situ synchrotron X-ray diffraction combined with a diamond anvil cell. The pressure-volume (P-V) data were fitted to the third-order Birch-Murnaghan EoS with V0 = 1581.45 ± 0.25 Å3, K0 = 111.6 ± 0.9 GPa and K′0 = 4.4 ± 0.2; additionally, when K′0 was fixed at a value of 4, V0 = 1581.04 ± 0.20 Å3 and K0 = 113.6 ± 0.3 GPa. The V0 (1581.45 ± 0.25 Å3) obtained by the third-order Birch-Murnaghan EoS agreed well with the measured V0 (1581.45 ± 0.05 Å3) under ambient conditions; this result confirmed the high accuracy of the experimental data in this study. Furthermore, the axial compression data of the schorl at room temperature were also fitted to a “linearized” third-order Birch-Murnaghan EoS, and the obtained axial moduli for the a- and c-axes were Ka = 621 ± 9 GPa and Kc = 174 ± 2 GPa, respectively. Consequently, the axial compressibilities were βa = 1.61×10-3 GPa-1 and βc = 5.75×10-3 GPa-1 with an anisotropic ratio of βa:βc = 0.28:1.00, indicating axial compression anisotropy. In addition, the compositional effect on the axial compressibilities of tourmalines was also discussed. Fitting our pressure-volume-temperature (P-V-T) data to the high-temperature third-order Birch-Murnaghan EoS provided the following thermal EoS parameters: V0 = 1581.2 ± 0.2 Å3, K0 = 110.5 ± 0.6 GPa, K′0 = 4.6 ± 0.2, (∂KT/∂T)P = -0.012 ± 0.003 GPa K-1 and αV0 = (2.4 ± 0.2) × 10-5 K-1. The obtained thermal EoS parameters in this study were also compared with those of previous studies on other tourmalines. The potential factors influencing the thermal EoS parameters of tourmalines were further discussed.

DEM analysis of the dynamic characteristics of QH-E lunar soil simulant under cyclic triaxial tests

In this paper, cyclic triaxial tests are performed by using discrete element method (DEM) to investigate the dynamic behaviors of QH-E lunar soil simulant. The influences of number of cycles, loading frequency, waveform, cyclic stress ratio (CSR) and confining pressure on the dynamic behaviors of lunar soil simulant are discussed. The results indicate that the axial strain and dynamic modulus first increase and then tend to be stable with increasing number of cycles. The dynamic modulus increases with increasing the loading frequency, while the axial strain decreases. The damping ratio is not particularly sensitive to the confining pressure and CSR, it only decreases slightly with increasing confining pressure or decreasing CSR. Under the same conditions, rectangular wave dynamic load can produce a larger axial strain and a smaller dynamic modulus than those of sine and triangular waves, and a higher loading frequency will lead to a higher dynamic modulus and a lower axial strain, these characteristics are consistent with other lunar soil simulants and sandy soils tested in the experiment. However, the effect of confining pressure on the dynamic modulus depends on the magnitude of the CSR. For the lower CSR (CSR<0.6), the dynamic modulus increases with increasing confining pressure. While for the higher CSR(CSR>0.6), the dynamic modulus decreases significantly with increasing confining pressure, which demonstrates the unique dynamic characteristics that differs from other lunar soil simulants and sandy soils, and shows the importance of considering the magnitude of the CSR under cyclic triaxial tests.

Preparation of anisotropic polyimide aerogels for thermal protection with outstanding flexible resilience using the freeze-drying method.

Polyimide aerogels (PIAs) not only possess excellent thermodynamic properties but also have a high porosity structure, making them an exceptional protective and thermal insulation material, and further broadening their application scope in aerospace and other cutting-edge fields. In this work, a series of anisotropic polyimide aerogels (3,3',4,4'-biphenyltetracarboxylic dianhydride (S-BPDA), p-phenylenediamine (PDA), 4,4'-diaminodiphenyl ether (ODA)) with excellent properties were prepared. These PIAs were obtained by unidirectional freeze-drying and thermal amination of two different precursor solutions mixed in proportion. These PIAs possess an irregularly oval tubular structure, exhibiting pronounced anisotropy. (PIA-2 exhibits outstanding flexible resilience in the radial direction. It can still regain its original form after half an hour of compression by a universal testing machine, yet it cannot do so in the axial direction. The thermal diffusivity of PIA-5 in the radial direction at room temperature is as low as 0.067 mm2 s-1, and even at 200 °C, the thermal diffusivity is as low as 0.057 mm2 s-1. Meanwhile, the thermal diffusivity in the axial direction at room temperature is 0.11 mm2 s-1, surpassing the value of 0.106 mm2 s-1 of aerogels prepared from monomeric raw materials and dried under supercritical conditions). PIAs exhibit outstanding thermal stability (the axial strength and modulus retention of PIA-8 at 200 °C are as high as 52.63% and 44.82%), and its weight loss temperature of 5% is as high as 603 °C and it has a glass softening temperature of 387 °C. PIAs also demonstrate exceptional flame retardancy in imitation flame retardant experiments and exhibit outstanding thermal insulation performance when heated on a 150 °C heating plate for 10 minutes (the radial surface temperature of PIA-5 was only 49.9 °C). These anisotropic PIAs materials exhibit outstanding flexible resilience, and thermal protection performance, holding significant importance for their widespread adoption as thermal insulation materials in aerospace, high-precision electronic components, and other domains.

Finite Element Simulation Parameter Calibration and Verification for Stem Cutting of Hydroponic Chinese Kale

The finite element simulation is a valid way for the rapid development of the root-cutting mechanism for hydroponic Chinese kale. The stem of the hydroponic Chinese kale was simplified as a transverse isotropic elastic body, and axial compression, three-point bending, and shear tests were performed. The ANSYS/LS-DYNA19.2 software was adopted for stem shear simulation, and the regression equation of the maximum simulated shear force was established. The optimized mechanical parameters were determined by minimizing the deviation between the maximum shear force obtained from the simulation and test. The three-dimensional scanning method was employed to establish the geometric model of the hydroponic Chinese kale stem. The cutting finite element simulation model and test platform were constructed. Displacement, deformation, and force measured from simulation and test were compared. Through measurement and simulation calibration, an axial elastic modulus of 6.22 MPa, axial Poisson’s ratio of 0.46, radial elastic modulus of 3.56 MPa, radial Poisson’s ratio of 0.44, radial shear modulus of 0.8 MPa, and a failure strain of 0.08 were determined. During the cutting simulation and test, the resulting maximum displacement deviations of the marking points on the end of the stem were 0.68 mm along the X-axis and 2.83 mm along the Y-axis, while the maximum deviations of the cutting and clamping force were 0.49 N and 0.77 N, respectively. The deformation and force variation laws of the kale stem in the cutting simulation and test process were basically consistent. It showed that the mechanical parameters calibrated by the simulation were accurate and effective, and the stem cutting simulation results with the finite element method were in good agreement with that of the cutting test. The study provided a reference for the rapid optimization design of the root-cutting mechanism for hydroponic Chinese kale harvest.

Study on Mechanical Properties of QH-E Lunar Soil Simulant under Conventional Triaxial and Cyclic Triaxial Tests

Study of the mechanical properties of lunar soil simulant is the key to conducting lunar soil sampling and lunar base construction. In this paper, conventional and cyclic triaxial tests are performed by using discrete element method (DEM) to study the mechanical properties of QH-E lunar soil simulant. The results indicate that the confining pressure has an important impact on the shear strength and dynamic modulus of QH-E lunar soil simulant. In the conventional triaxial test, with the increasing of the confining pressure, both the peak deviatoric stress and residual stress increase, and the relevant results have been supported by experiments. In cyclic triaxial test, the area of cyclic hysteresis loop decreases with the increasing of the number of cycles, the axial strain and dynamic modulus first increase and then tend to be stable with the increasing of the number of cycles. Moreover, the axial strain increases with increasing confining pressure, while dynamic modulus decreases at a specific cyclic stress ratio (CSR) condition.

Buckling analyses of cylindrical shells with axial variable elastic modulus under external pressure

Buckling analyses of cylindrical shells with axial variable elastic modulus under external pressure

Investigation of the stress–strain state of a composite blade in ANSYS WorkBench

In this paper, the static strength of a UAV blade made of composite material was calculated. Composite materials have an advantage over traditional materials (metals and alloys) in the field of aviation - gain in weight, low sensitivity to damage, high rigidity, high mechanical characteristics. At the same time, the identification of vulnerabilities in a layered structure is a difficult task and in practice is solved with the help of destructive control. Composite materials available in the ANSYS materials library were used in the modeling: Epoxy Carbon Woven (230 Gpa) Prepreg woven carbon fiber in the form of a semi–finished prepreg impregnated with epoxy resin carbon fiber with Young's modulus E=230 GPa and Epoxy Carbon (230 Gpa) Prepreg is a unidirectional carbon fiber prepreg impregnated with epoxy resin with a Young's modulus E=230 GPa. Modern software products, such as ANSYS WorkBench, allow comprehensive investigation of the layered structure. Several variants of blade designs with different fillers as the median material were investigated. The forward and reverse destruction criteria based on the Tsai-Hill theory were used. The influence of gravity was not taken into account. It is shown that the developed blade design meets the requirements. Balsa wood, pine, aspen and polyurethane foam were chosen as the middle material of the blade. Pine and aspen wood were selected according to the criteria of their availability and having the lowest density. The materials library of the ANSYS WorkBench software package used does not have characteristics for all of them, so the characteristics of the selected materials (pines and aspens) were added manually. For modeling and calculations in the ANSYS WorkBench program, such characteristics as density, axial elastic modulus, Poisson's coefficients, shear modulus and tensile and compressive strength limits are required.

Analytical and numerical solution and multi-objective optimization of tetra-star-chiral auxetic stents

The present study examines the mechanical properties of auxetic stents with the tetra-star-chiral structure. The tetra-star-chiral geometry is parametrically modeled. Then, the design of experiments (DOE) is developed by defining the elastic properties of the stents and using the response surface method (RSM). Finite element (FE) analysis is performed in order to find a polynomial relationship between the geometric parameters as inputs and the elastic parameters as the outputs. Then, the optimal stent is found in terms of elasticity parameters by using RSM and NSGA-II methods and the two-dimensional Pareto front is plotted. The optimal parameters of the stent including flexural stiffness, axial elasticity modulus, radial elasticity modulus and Poisson’s ratio are obtained as 10.66 mPa m4, 5.37 MPa, 33.2 MPa and − 0.41, respectively. Moreover, a method is proposed to find an analytical solution for metal elastic stents in order to verify the FE model results, and also the blood vessel compliance of the optimal stent is examined.

Compression stress-strain curve of lithium slag recycled fine aggregate concrete.

As one of the key materials used in the civil engineering industry, concrete has a global annual consumption of approximately 10 billion tons. Cement and fine aggregate are the main raw materials of concrete, and their production causes certain harm to the environment. As one of the countries with the largest production of industrial solid waste, China needs to handle solid waste properly. Researchers have proposed to use them as raw materials for concrete. In this paper, the effects of different lithium slag (LS) contents (0%, 10%, 20%, 40%) and different substitution rates of recycled fine aggregates (RFA) (0%, 10%, 20%, 30%) on the axial compressive strength and stress-strain curve of concrete are discussed. The results show that the axial compressive strength, elastic modulus, and peak strain of concrete can increase first and then decrease when LS is added, and the optimal is reached when the LS content is 20%. With the increase of the substitution rate of RFA, the axial compressive strength and elastic modulus of concrete decrease, but the peak strain increases. The appropriate amount of LS can make up for the mechanical defects caused by the addition of RFA to concrete. Based on the test data, the stress-strain curve relationship of lithium slag recycled fine aggregate concrete is proposed, which has a high degree of agreement compared with the test results, which can provide a reference for practical engineering applications. In this study, LS and RFA are innovatively applied to concrete, which provides a new way for the harmless utilization of solid waste and is of great significance for the control of environmental pollution and resource reuse.

Modification of carbon nanofibers for boosting oxygen electrocatalysis.

Oxygen electrocatalysis is a key process for many effective energy conversion techniques, which requires the development of high-performance electrocatalysts. Carbon nanofibers featuring good electronic conductivity, large specific surface area, high axial strength and modulus, and good resistance toward harsh environments have thus been recognized as reinforcements in oxygen electrocatalysis. This review summarizes the recent progress on carbon nanofibers as electrocatalysts for oxygen electrocatalysis, with special focus on the modulation of carbon nanofibers for further elevating their electrocatalytic performance, which includes morphological and structural engineering, surface and pore size distribution, defect engineering, and coupling with other electroactive materials. Additionally, the correlation between the geometrical/electronic structure of their active centers and electrocatalytic activity is systematically discussed. Finally, conclusions and perspectives of this interesting research field are presented, which we hope will provide guidance for the future fabrication of more advanced carbon-fiber-based electrocatalysts.

Elastic properties evaluation of banana-hemp fiber-based hybrid composite with nano-titanium oxide filler: Analytical and Simulation Study

In recent years, nano-filler-based hybrid composites have gained significant attention from the research community; The nano-filler-based hybrid composites can have potential applications in numerous sectors. Nano-fillers are bringing a leading development in material science and natural fibers-based composites. The present study considers the impact of various weight percentages of nano-titanium oxide (NTiO2) fillers (2%, 4%, and 6%) on the elastic features of novel hybridized banana-hemp fiber-reinforced epoxy composites. The proposed composite is analyzed for its elastic properties like longitudinal and transverse elastic modulus, axial Poisson's ratio, and axial shear modulus using homogenized micromechanical models, namely, Mori-Tanaka (M-T) model, Generalized self-consistent (G-SC) model and Modified Halpin-Tsai (M-HTS) model. The composite is modeled using one layer of banana fiber, one layer of NTiO2 and epoxy, and one layer of hemp fiber. All three layers of the composite are arranged in the sequence of banana fiber at 450, a layer of NTiO2 and epoxy at 00, and hemp fiber at 450. The proposed composite's vector sum deformation and strength are examined by employing the ANSYS APDL application. The results obtained in this study are compared with the experimental work mentioned in the literature. The composite reinforced with six weight% NTiO2 has the highest mechanical strength, and the modified Halpin-Tsai (M-HTS) model is the most effective in calculating the elastic features of the proposed composite. In addition to the above, the hybridization effect for the proposed composite is also estimated to analyze the tensile failure strain of banana and hemp fiber in the proposed hybrid composite structure.

Experimental investigation on static and dynamic properties of nanosilica modified cement soil

It has been proved that nanosilica can improve the mechanical properties of cement soil, however, the static and dynamic properties of nanosilica modified cement soil and dispersion method study of nanosilica in cement soil were few, thereby investigated by unconfined compression test and dynamic triaxial test in this study. A series of unconfined compression test results indicated that the dispersion method of nanosilica is of importance in the strength of nanosilica modified cement soil (NCS), and soaking in water for 24 h is the optimal dispersion method among designed methods. Unconfined compressive strength (UCS) increases with increasing nanosilica content in the range of 0 to 0.4%, and then reduces gradually while nanosilica content is beyond 0.4%. The optimal nanosilica content can be seen as 0.4%, and the corresponding UCS at the curing age of 7 d is 960 kPa, which increases by 47.2% comparing to the specimen without nanosilica. Dynamic triaxial test reveals that the variation of the cumulative plastic axial strain and dynamic elastic modulus versus nanosilica content are same and opposite to UCS respectively, and the minimum of the cumulative plastic axial strain and maximum of dynamic elastic modulus are obtained while nanosilica content is 0.4%, which reduces by 48.1% and increases by 69.8% respectively comparing to the specimen without nanosilica. Finally, a simple and practical prediction model is developed to capture the evolution of the cumulative plastic axial strain with cycle number, and its simulation effect is validated by dynamic triaxial test results. It is believed that this paper finds an efficient dispersion method of nanosilica in cement soil, and provides the dynamic properties of nanosilica modified cement soil, which can promote practical application of nanosilica in road engineering.

Impact resistance of geopolymer concrete under different types of fiber admixtures

To investigate the dynamic mechanical response characteristics of geopolymer concrete under impact load, the effects of different curing ages and strain rates on the impact resistance of geopolymer concrete have been explored. First, this paper first obtains the optimal mix ratio of geopolymer concrete by optimizing the slump test of mix ratio. Second, the stress–strain constitutive relationship of geopolymer concrete at different ages is deduced, and the mechanical properties, such as axial compressive strength and elastic modulus, are determined. Finally, two different kinds of fibers, carbon fiber and steel fiber, are mixed into concrete, which are utilized to test the mechanical properties including compressive strength, splitting tensile strength, flexural strength, and impact toughness. The results indicate that with the increase in carbon fiber content, the compressive strength, splitting tensile strength, and flexural strength of geopolymer concrete decrease first and then increase. Moreover, with the increase in steel fiber content, the compressive strength of geopolymer concrete increases continuously, the splitting tensile strength increases first and then decreases, the flexural strength decreases first and then increases, and the impact toughness increases first and then decreases.

Three-dimensional structural characterization and mechanical properties of bamboo parenchyma tissue

Bamboo is predominantly composed of parenchyma and fibers, with parenchyma constituting approximately 52% of the bamboo culm wall. The bamboo fibers function as the primary load-bearing elements, its structure and performance have been studied in detail. However, investigations concerning the structure and mechanical properties of parenchyma tissue remain limited. Consequently, this study focuses on the comprehensive characterization of the three-dimensional (3D) structure of bamboo parenchyma. Additionally, the study encompasses the evaluation of tensile and compressive properties of parenchyma tissue, along with an analysis and discourse on failure mechanisms. Parenchyma cells can be categorized into two types: long cells, accounting for approximately 89.37%, and short cells. The measured tensile strength and elastic modulus of the parenchyma tissue are 48.81 MPa and 706.48 MPa, respectively. The propagation of cracks leading to tensile failure predominantly occurs along the middle lamella, accompanied by partial penetration through cell walls. Concerning parenchyma tissue compression, three discernible stages can be identified: the elastic stage, plateau stage, and densification stage. The axial load-bearing capacity of parenchyma tissue exceeds that of the tangential and radial orientations. Axial compressive strength and elastic modulus of the parenchyma are measured at 18.82 MPa and 5.24 GPa, respectively. Compression failure modes in parenchyma tissue encompass compression bending and cell fracture, shear failure of the middle lamella, and detachment and debonding of the cell wall. The comprehensive structural and mechanical parameters derived from this investigation provide valuable insights for the development of numerical models and understanding the various mechanical properties of bamboo.

Dynamic behaviour of oyster shell powder-modified expansive soil under cyclic loading

This paper systematically studies the dynamic mechanical properties of oyster shell powder (OSP)-modified expansive soil under simulated train loads. A GDS dynamic triaxial test system was used in the study. The axial cumulative strain development and hysteresis curve characteristics of expansive soil with different oyster shell powder particle sizes (dosp=0–0.075 mm, 0.075–0.15 mm, 0.15–0.25 mm, 0.25–0.5 mm, 0.5–1.0 mm, 1.0–2.0 mm), dosages (Fosp=0 %, 3 %, 6 %, 9 %) and cyclic stress ratios (CSR=0.1, 0.15, 0.2, 0.25, 0.275, 0.3) were studied. The results show that when dosp< 0.5 mm, the axial cumulative strain, damping ratio and dynamic resilient modulus of the modified soil are significantly improved with increasing oyster shell powder content; when Fosp= 9 % and dosp< 0.5 mm, the dynamic performance of the modified soil is similar. When Fosp= 9% and dosp= 0.25–0.5 mm, compared with plain soil, the axial cumulative strain decreases by 37.3 %, the damping ratio decreases by 39 %, and the dynamic elastic modulus increases by 29.9 % after 200,000 cycles. When dosp> 0.5 mm, the performance of each dynamic performance index of the modified soil deteriorates compared with that of the plain soil, and the deterioration effect is more significant with increasing oyster shell powder content and particle size. When oyster shell powder-modified soil is used as a subgrade filler for a ballasted track railway with a design speed below 200 km/h, it is recommended to control the content of oyster shell powder as Fosp= 9 % and the particle size of oyster shell powder as dosp= 0.25–0.5 mm. At this time, from the perspective of controlling the postconstruction settlement of the railway subgrade, the cyclic stress ratio CSR should be controlled below 0.2.