Compression Apparatus Research Articles

An elasto-plastic biphasic model of the compression of multicellular aggregates: the influence of fluid on stress and deformation

We present a mathematical model of the compression of multicellular aggregates, and we specialise it to a compression-release test that is well known in the biological literature. Within the adopted mechanical setting, a multicellular aggregate is studied as a biphasic system consisting of a soft solid porous medium saturated with an interstitial fluid. In particular, together with the deformation of the considered aggregate, the characterisation of the model outlined in this work relies on four fundamental features. First, by assuming the interstitial fluid to be macroscopically inviscid and to evolve according to the Darcian regime, we resolve its flow and determine the associated time dependent pressure distribution. Second, we focus our attention on the remodelling of the compressed aggregate, that is, on the rearrangement of its internal structure in response to the external loads applied to it. Specifically, we look at the way in which such a rearrangement is induced by the considered experiment and at how it affects the mechanical behaviour of the aggregate. Moreover, we introduce a remodelling-dependent permeability tensor with the purpose of visualising a more direct influence of remodelling on the dynamics of the aggregate’s interstitial fluid. Finally, we resolve the interactions exchanged between the aggregate and the compressive apparatus. This task necessitates the formulation of an appropriate contact problem, thereby calling for the description of the evolution of the area through which the aggregate and the apparatus exchange mechanical interactions. In particular, the continuity conditions to be applied on such a contact area are discussed. Our numerical simulations show the role played by the different phenomena accounted for in the model and the overall dynamics of the aggregate within the considered experiment.

RELATIVE DENSITY EFFECTS ON DRAINED SAND BEHAVIOR AT HIGH PRESSURES

A high-pressure triaxial compression and extension apparatus was employed to investigate the effects of initial relative density on the drained behavior of sand. Experiments were performed on cylindrical specimens of Cambria sand with initial relative densities of 30% and 60%, and compared with previously published results for 90%. Confining pressures in the range of 0.25 to 60 MPa were employed to obtain the characteristic behavior of the sand over a large range of pressures. As the confining pressure increased particle crushing increasingly influenced the stress-strain and volume change relations, producing increasing strains to failure and increasingly contractive volume changes. Beyond certain high values of mean normal stress at failure, increasing with initial relative density, the volumetric contraction and strains to failure began to decrease. The Mohr-Coulomb failure envelopes show the greatest curvature for the highest density, but the failure envelopes merge at high pressures where, due to particle crushing, the relations between void ratio and isotropic pressure are described by a single curve. The experiments show clearly that the rates of dilation at failure and the friction angles are directly related to each other, as has been proposed by many investigators. The friction angles are higher in extension than in compression for lower confining pressures, but a crossover occurs and the friction angles are higher in compression than in extension for higher confining pressures.

Development of triaxial compressive apparatus for neutron experiments with rocks.

Underground engineering for processes such as geological disposal of high-level nuclear waste, CO2 capture and storage, and mining and drilling for resources requires an understanding of the mechanical behavior of rocks at subsurface stress states, i.e., triaxial compressive stress. Strain measurement using neutron diffraction can be applied to rocks to analyze strain accumulation mechanisms at the microscopic scale. This study reports the development of triaxial compressive apparatus for strain measurement using neutron diffraction. The apparatus can analyze rock specimens (diameter, 25mm; length, 50mm) and apply a maximum confining pressure of 50 MPa. Materials for the components of the apparatus were investigated theoretically based on neutron beam transmission and experimentally using neutron diffraction experiments. The feasibility of the apparatus was verified by measuring strain at hydrostatic pressure under the application of confining pressure and triaxial compression. The theoretical and experimental results show that the apparatus could obtain sufficient neutron statistics from a rock specimen. It was confirmed experimentally that the measured strain values are correlated with the applied confining pressure and stress. The lattice strains of quartz minerals measured by neutron diffraction showed linear deformation behavior, indicating that elastic strain accumulated in the minerals. This apparatus will enable the finding of new insights into the deformation mechanisms of rocks.

Reinforcement Effect and Permeability Assessment of Gravel-Tire Chips Mixture (GTCM) for Use in Marine Landfill

The number of marine landfills in Japan has increased over the past decade due to the lack of suitable land. For marine landfills, protection of the alluvium clay layer and improvement of the drainage performance in waste inflow are important aspects. In this paper, an economical construction method for these problems is proposed using gravel-tire chips mixture (GTCM) as the horizontal reinforcement and drainage medium beneath the waste. The content and particle size of tire chips mixed with gravel are essential factors that affect the bearing capacity and permeability of the reinforcement layer. Therefore, a series of permeability tests are conducted using newly developed large-scale triaxial compression and permeability test apparatus to investigate the effect of tire chips particle size, the mass proportion of tire chips (MPTC), and triaxial stress on the permeability of GTCM. In addition, the effectiveness of this technique is evaluated by numerical simulations. The experimental results confirm that the shear strength of GTCM is influenced by tire chips content. Furthermore, permeability coefficient of GTCM is on the order of 0.02 cm/s to 0.08 cm/s, which is higher than the tolerable level of permeability of drainage layer in landfills. GTCM sample shows excellent permeability even on higher compression. Moreover, the Non-Darcy flow properties of GTCM (non-linear) are introduced in this study, and an approximate power function relationship between the permeability coefficient and the non-Darcy flow coefficient is developed. The numerical results confirm that GTCM performs better than the sand, a traditional reinforcement material.

Time-dependent strength behavior of dredged clays at low effective stresses

This paper presents an experimental investigation on the effects of initial water content and time during secondary compression on the strength behavior at low effective stresses of dredged clays obtained from two places in China. A suite of vane shear tests was conducted on clay samples consolidated at 16 kPa using the self-developed compression apparatus. Tests results showed that the shear angle corresponding to the peak shear stress almost increases with the decreasing time during secondary compression and the vane shear stress increases with decreasing initial water content at the same shear angle. A significant increase in peak strength with time during secondary compression was observed compared with the insignificant increase in residual strength. The normalized strength increases linearly with log time during secondary compression. The undrained strength of dredged clay specimens with different initial water contents consistently increases with time during secondary compression. The strength and time curve for specimens at lower initial water content lies above that at higher initial water content. A quantitative expression of normalized strength as functions of normalized water content and time during secondary compression was obtained. The proposed equation is verified by comparing the calculated results and measured results for other sources of samples.

ON THE SHEAR STIFFNESS DECREASE OF SANDY SOILS DUE TO PARTICLE CRUSHING PROGRESS

Many previous studies have focused on theoretical and experimental evaluations of the crushing of sandy soil particles under high pressure conditions. From the perspective of practical scenarios, the decreased bearing capacity caused by volume shrinkage and the reduced shear strength and stiffness caused by the crushing of sandy soil particles are important aspects. Therefore, this study aims to confirm the decrease in the shear stiffness of sandy soils subjected to various stress levels combined with high principal stresses. Author conducted crushing tests using the high-pressure true tri-axial compression apparatus under the planned stress paths. Tests on isotropic compression without deviatoric stress q and those involving combinations of the mean stress p and deviatoric stress q up to the shear failure line (SFL) on the p-q plane are employed to characterize the particle crushing of sandy soils. The results indicate that the shear stiffness of sandy soils starts to decrease due to particle crushing under a combination of low mean stress p and high deviatoric stress q. Furthermore, experimental formulas regarding the decrease in shear stiffness due to particle crushing were estimated based on the relationships among the mean stress p, deviatoric stress q and deviatoric strain εd.

A Portable System for Processing Donated Whole Blood into High Quality Components without Centrifugation

Introduction: Centrifugation is the cornerstone of blood processing because it has been the only technology capable of separating large volumes of whole blood (WB) into components for storage under optimal conditions in a reasonable amount of time. However, the logistical complications and potential cellular damage associated with centrifugation-based manufacturing of blood products are well documented. In this study, we present a new dual-stage, passive separation system for processing WB into components, which does not require costly or complex machinery, and can be used on-site by minimally-trained personnel immediately following blood donation. This approach consists of two passive blood-processing modules, neither of which requires electricity: (i) a blood-bag compression apparatus designed to maximize the speed and efficiency of passive RBC sedimentation for separating RBCs and platelet-rich plasma (PRP) from WB at normal gravity (i.e. 1×g), and (ii) a flow-through microfluidic concentrator for continuous high-throughput enrichment of platelets from the PRP fraction, to produce platelet concentrate (PC) and platelet-poor plasma (PPP). The ability of this technology to produce high-quality blood components quickly without the use of a centrifuge was demonstrated.Materials and Methods: Freshly-donated units (~500mL) of whole blood (WB) were randomly selected (under an IRB approved protocol) from blood donations by healthy donors who met AABB/FDA eligibility criteria. The WB units (n = 6) were divided into two equal parts, with one half processed by the conventional centrifugation technique (‘PRP method,‘ control arm), and the other half with our new portable blood separation system (test arm). Both separation procedures were performed concurrently, within 4 hours of donation. The initial quality of blood products (RBCs, platelets and plasma) generated by the two approaches were compared using an extensive panel of hematological parameters, including hematocrit, mean corpuscular volume, platelet count, mean platelet volume, white blood cell count, RBC and platelet phosphatidylserine (PS) exposure, platelet P-selectin expression, total free protein, free hemoglobin (Hb), % hemolysis, RBC deformability, pH, K+, Na+, glucose, lactate, ATP, 2,3-diphosphoglyceric acid concentration (2,3-DPG), platelet aggregability (agonists: thrombin receptor agonist peptide, adenosine diphosphate, collagen), factors VIII and XI, soluble CD40-ligand (sCD40L), and thromboxane B2 (TxB2).Results and Discussion: To perform separation using our new portable separation system, 250mL (‘half-unit‘) of WB was placed in a 1L sedimentation bag between two plates of a custom-made compression apparatus at a slight incline (~10°) to allow natural sedimentation of WB into PRP and RBCs at unit gravity. After 150 minutes of sedimentation, the supernatant PRP was expressed from the sedimentation bag through the high-throughput microfluidic platelet concentrator at ~3.2 mL/min to process PRP into PC and PPP. Following PRP expression, the sedimented RBCs were mixed with AS-3 and leukoreduced in the same manner as RBCs produced via centrifugation. The entire separation process for a half-unit of WB was completed within ~3 hours. Comparison of nearly all RBC parameters showed no significant differences between the two separation approaches, although the portable system generated RBC units with a slight, statistically significant improvement in 2,3-DPG (portable system: 15.8 ± 1.2 µmol/g of Hb; centrifugation: 15.3 ± 1.2 µmol/g of Hb; p < 0.05). Importantly, key markers of platelet damage were significantly and meaningfully reduced in PC units generated using the portable, centrifuge-free system: platelet activation (assessed via P-selectin expression) was less than half of that for PC units produced via centrifugation (portable system: 5.2 ± 2.1%; centrifugation: 12.2 ± 3.6%; p < 0.01), and the release of pro-inflammatory mediators (sCD40L, TxB2) was also significantly lower in PC units produced with the portable system than via centrifugation (p < 0.01).Conclusion: This study demonstrated that a simple, portable, passive system for separating donated blood into components could be a viable alternative to centrifugation - particularly for applications in remote or resource-limited settings, or for patients requiring highly functional and undamaged platelets. [Display omitted] DisclosuresGifford:Halcyon Biomedical Incorporated: Employment, Equity Ownership. Shevkoplyas:New Health Sciences, Inc.: Consultancy, Research Funding; Halcyon Biomedical Incorporated: Employment, Equity Ownership, Patents & Royalties: U.S. Patent Appl. 61/929,357, Research Funding.

KONSTANTIN SIVASH - CONSTRUCTOR OF UNIQUE ENDOPROTHESIS

The author briefly describes the history of the creation of the hip joint endoprotheses, as well as the biography of Professor Konstantin Sivash, the implementator of a unique one-piece hip joint endoprosthesis, original knee and elbow joint endoprostheses, compression apparatus for the knee joint, plates and pins for osteosynthesis of fractures.

Triaxial Compression on Semi-solid Alloys

Multi-axial compression of the mushy zone occurs in various pressurized casting processes. Here, we present a drained triaxial compression apparatus for semi-solid alloys that allow liquid to be drawn into or expelled from the sample in response to isotropic or triaxial compression. The rig is used to measure the pressure-dependent flow stress and volumetric response during isothermal triaxial compression of globular semi-solid Al-15 wt pct Cu at 70 to 85 vol pct solid. Analysis of the stress paths and the stress–volume data show that the combination of the solid fraction and mean effective pressure determines whether the material undergoes shear-induced dilation or contraction. The results are compared with the critical state soil mechanics (CSSM) framework and the similarities and differences in behavior between equiaxed semi-solid alloys and soils are discussed.

Evolution of surface roughness of single sand grains with normal loading

The surfaces of soil grains are not perfectly smooth, especially examined at small scale. In geotechnical engineering, surface roughness has been found to be able to influence the inter-particle friction angle at micro scale and small-strain stiffness at macro scale. However, the quantity and quality of the studies on surface roughness of natural soils are still limited. In this study, the evolution of surface roughness of natural sand grains with increasing normal load was investigated by a single-particle compression apparatus. Thirty Leighton Buzzard sand (LBS) grains coarser than 2·36 mm were tested, and the surface roughness was measured before and after compression by an optical interferometer. The deformations of the asperities and of the bulk of the sand grains in the vicinity of the contact were mapped. Three stages were identified as the normal load increased: (a) plastic deformation of the asperities; (b) asperities and bulk plastic deformation; and (c) bulk only plastic deformation. At very small normal load, only the asperities were found to deform plastically, and the surface roughness of the sand grains decreases due to the flattening of the asperities. Within this regime, the load–displacement relationship of LBS grains under compression could be simulated by the modified Hertz model, which takes surface roughness into consideration. With increasing normal load, the bulk of the sand grains began to yield near the contact. The geometry of the surfaces of LBS grains in contact with the loading platen is the main factor that influences the plastic deformation of the bulk. Differently from the plastic deformation of the asperities, the plastic deformation of the bulk could both smoothen and roughen the surfaces. When plastic deformation of the bulk occurred, both Hertz and modified Hertz theory could not predict the load and displacement relationship of sand grains. Through analysing the cumulative distributions of surface roughness of 30 LBS grains at different normal loads by the Weibull function, the surface roughness was found to decrease dramatically with increasing normal load at first and then tended to be constant.

Effect of inclined interface angle on shear strength and deformation response of cemented paste backfill-rock under triaxial compression

Cemented backfilling has been widely used in underground mines worldwide. The stability of cemented backfill must be sufficient to maintain the subsequent stope. Investigation into the shear strength and deformation of cemented paste backfill-rock (CPB-rock) under triaxial compression is prominent important for mine operators and managers, while the knowledge of the effect of the interface between cemented paste backfill (CPB) and rock on the shear strength and deformation behavior is limited. The objective of this paper is to experimentally investigate the effect of interface angle on the triaxial deformation behavior and shear strength of the CPB-rock. Two interface angles (45° and 60°) and three cement contents (2.5, 5 and 7.5 wt%) were designed. All tests were carried out by a standard triaxial compression apparatus, and the confining stress levels were varied in a range corresponding to the in-situ horizontal pressures (σc ≤ 200 kPa). The results show that the interface angle plays a dominant role in the failure patterns of CPB-rock. Increasing the cement content improves the brittleness of CPB matrix, and increases the shear strength difference between CPB-rock and CPB. The failure pattern of CPB-rock changes from composite failure to slipping failure. At last, the bilinear peak strength envelope for CPB-rock specimens is proposed. The results are expected to quantify the effect of CPB-rock interface on stability of cemented backfill.

ON THE PARTICLE CRUSHING FEATURES OF SANDY SOILS

Previous studies have investigated particle crushing of sandy soils in high-pressure conditions. In practice, the volume shrinkage and decreasing shear strength due to particle crushing around the pile-foundation tip in crushable sandy soils may be more important. Therefore, this study aims to confirm the volume shrinkage of sandy soils, e.g., silica sand, weathered granite, and volcanic sand, under various stress paths with a combination of high principal stresses. High-pressure crushing tests were carried out using a true tri-axial compression apparatus under the planned stress paths. Isotropic compression tests and combined stress tests (mean stress p and deviatoric stress q) were employed for three types of sandy soil. The particle-crushing progress became active in combination with mean stress p and deviatoric stress q. In addition, the relationships between the plastic volumetric strain and relative breakage were found to be approximately linear. As expected, the silica sand was less crushable than the weathered granite sand and volcanic sand under the same stress conditions.

Time-Dependent Compressibility of Crude Oil in Gelled State Measured by a New Apparatus

Summary Compressibility is a basic property of gelled crude oil, which was always regarded as a constant in the unsteady-pipe-flow process. In this article, the compressibility of gelled crude oil was accurately measured, and some new characteristics were discovered by a new apparatus that was developed using a special sealing method consisting of an elastic film and the Newtonian fluid. There was no leakage in the special hermetical method, and the unexpected seal-ring deformation of the piston in the traditional compression apparatus was also well-avoided. Using the new apparatus, compressibility of the gelled crude oil was tested and it was found that the compressibility of gelled crude oil is strongly time dependent.

Investigation of Different Compression Apparatus Usage Effects in Calibration Process of Strain Cylinders

In this article, in calibration process of strain cylinder, which is performed according to ISO 376 standard, effect of loading apparatus with different dimensions on measurement result has been investigated. In addition, relative repeatability error of calibration on measurement results, temperature fluctuation, accuracy error of measurements, creep error, as well as the stability and metrological characteristics of indicator have been examined. As a result, it has been determined that use of loading pads with different diameters has significantly affected metrological performance of strain cylinder.

Effect of stress paths on the particle crushing

In previous studies, almost all they had carried out the crushing tests under usual tri-axial compression, Ko and simple shear conditions. However, it is necessary to perform the crushing test under general stress conditions in ground with controlled each principal stresses individually to find the mechanical characteristics of the particle crushing. Therefore, the purpose of this study is to confirm the effect for particle crushing under various stress paths in the combination of principal stresses. Authors plan the particle crushing tests with combinations of principal stresses operating the mean stress p, deviatoric stress q and Lode angle θ up to the Shear Failure Line (SFL) on the pie-plane. These particle crushing tests were carried out using the high pressure true tri-axial compression apparatus under the planned stress paths. As a result, the degree of Lode angles has little traction to the progress of the particle crushing and authors found that deviatoric stress q has essential effect on the particle crushing. In addition, the degree of particle crushing are little effected by the various monotonic stress paths on p-q plane when the maximum values of p and q are same.

Mechanical Behavior Study of Bending and Compression of Pineapple Leaf Fiber

This study aims to provide new-type textile raw materials for the textile industry with pineapple leaf fiber as an example. The bending of pineapple leaf fiber and compressibility of fiber assemblies were tested with JXW03 single fiber compression bending tester and KES-G5 minitype compression apparatus respectively, to study the change rule of bending property of pineapple leaf fiber and represent the compression characteristic curve of fiber assemblies. The results indicate that the values of EB and RB of fiber roots are 6.43GPa and 294.59E-5cN·cm2, and that of the middle segment of fiber are 2.82GPa and 118.17E-5cN·cm2; the mean values of Rc, ΔT and Lc of fiber roots are 57.73%, 4.33 mm and 0.46, and that of the middle segment of fiber are 62.20%, 4.65 mm and 0.43. Anova suggests that there exists highly significant difference in the sampling site in respect of equivalent bending modulus and flexural stiffness of fiber (P<0.01), no significant difference in respect of compressive mechanical indicators of fiber assemblies (P>0.05), the compression-restore curve of fiber roots and that of central assemblies are in the same shape, and they are similar in respect of compression recoverability, besides, the compression curve doesn’t coincide with restoration curve for fibers are of elasticity and viscosity concurrently.

Puerarin Relieved Compression-Induced Apoptosis and Mitochondrial Dysfunction in Human Nucleus Pulposus Mesenchymal Stem Cells via the PI3K/Akt Pathway.

Puerarin (PUR), an 8-C-glucoside of daidzein extracted from Pueraria plants, is closely related to autophagy, reduced reactive oxygen species (ROS) production, and anti-inflammatory effects, but its effects on human nucleus pulposus mesenchymal stem cells (NPMSCs) have not yet been identified. In this study, NPMSCs were cultured in a compression apparatus to simulate the microenvironment of the intervertebral disc under controlled pressure (1.0 MPa), and we found that cell viability was decreased and apoptosis level was gradually increased as compression duration was prolonged. After PUR administration, apoptosis level evaluated by flow cytometry and caspase-3 activity was remitted, and protein levels of Bas as well as cleaved caspase-3 were decreased, while elevated Bcl-2 level was identified. Moreover, ATP production detection, ROS, and JC-1 fluorography as well as quantitative analysis suggested that PUR could attenuate intercellular ROS accumulation and mitochondrial dysfunction. Besides, the rat tail compression model was utilized, which indicated that PUR could restore impaired nucleus pulposus degeneration induced by compression. The PI3K/Akt pathway was identified to be deactivated after compression stimulation by western blot, and PUR could rescue the phosphorylation of Akt, thus reactivating the pathway. The effects of PUR, such as antiapoptosis, cell viability restoration, antioxidation, and mitochondrial maintenance, were all counteracted by application of the PI3K/Akt pathway inhibitor (LY294002). Summarily, PUR could alleviate compression-induced apoptosis and cell death of human NPMSCs in vitro as well as on the rat compression model and maintain intracellular homeostasis by stabilizing mitochondrial membrane potential and attenuating ROS accumulation through activating the PI3K/Akt pathway.

Reutilisation of coal gangue and fly ash as underground backfill materials for surface subsidence control

To address the environmental problems caused by solid waste while promoting the sustainable development of mines, gangue and fly ash can be used as underground backfill materials to achieve the comprehensive utilisation of solid waste mining resources. We measured the compressive deformation characteristics of samples with different ratios of gangue to fly ash and analysed their stress-strain relationship and associated changes in their porosities using a YAS-5000 servo testing machine and a homemade compression apparatus. Moreover, we revealed the mechanisms of deformation resistance of gangue and fly ash from both a macro and meso perspective and determined that the optimal ratio of gangue to fly ash is 0.35. In addition, taking the backfill face in Coal Mine as an example, mixed materials of gangue and fly ash at a ratio of 1:0.35 were backfilled into a goaf. After mining of the working face, the surface only sank by 170 mm approximately. This method not only effectively disposes of solid wastes, i.e., gangue and fly ash, on a large scale but also controls surface subsidence to protect adjacent buildings and structures. Therefore, the coordinated development of coal resource mining and environmental protection are realised.

Effect of Particle Size on the Hydraulic Characteristics of Mechanically and Biologically Treated Waste

Mechanical biological treatment (MBT) is a waste processing technology that helps conserve resources and reduce emissions harmful to the environment. The treatment of municipal solid waste (MSW) using MBT is a hot topic in environmental geotechnical engineering. Permeability tests were carried out on MBT waste using a compression and permeability combined apparatus and a large‐scale vertical permeability apparatus taking the influence of particle size into consideration. The permeability of samples with smaller particle sizes was found to be lower for the same pressure and dry mass (%) of component. The best‐fit line between the logarithmic permeability and variables such as the dry density was linear. As the dry density increased or the void ratio decreased, the permeability of samples with smaller particles decreased more. The logarithmic permeability increased with the increase in the average particle size and void ratio. The permeabilities of MBT waste corresponding to particle size ranges of 0–10, 0–20, and 0–40 mm were 10−10–10−5, 10−8–10−4, and 10−5–10−3 m/s, respectively. The difference between MBT waste and MSW was analyzed in terms of their permeability. The results of MBT waste were compared with those reported in previous studies to provide reference for the permeability analysis of MBT landfills.

Influence of Real‐Time Heating on Mechanical Behaviours of Rocks

The rock mechanical properties under the effect of high temperature present a great significance on underground rock engineering. In this paper, the mechanical properties of sandstones, marbles, and granites under real‐time heating were investigated with a servo‐controlled compression apparatus. The results show that mechanical behaviours of all the three types of rocks are influenced by real‐time heating to different degrees. Due to thermal cracking, the uniaxial compressive strengths decrease as the heating temperature rises from room temperature to 400°C. Above 400°C, the sandstone exhibits a significant increase in UCS because of the sintering reaction. The sintering enlarges the contact area and friction between crystal grains in the sandstone, which strengthens the bearing capacity. For marbles, the UCS continues to decrease from 400°C to 600°C due to thermal cracking. However, the carbonate in the marble begins to decompose after 600°C. The generated particles would fill the cracks in the marble and increase the strength. For granites, their UCS presents a sharp decline after 400°C because of thermal cracking. For all rock elastic modulus, they present a decreasing trend, and this indicates that the rock’s ability to resist deformation gradually weakens under the effect of temperature. In general, rock mechanical behaviours under real‐time heating differ from those in normal situations, and use of the parameters presented here is important for underground rock engineering related to high temperature and can improve the precision in theoretical and numerical analysis.