Compaction Stage Research Articles

A novel design of compact tilt stage with spatially distributed anti-symmetric compliant mechanism

The tilt stage with high precision angular motions has emerged as one of the key enabling components in many advanced engineering applications, such as adaptive optics, space communication and ultra-high precision manufacturing, where the design requirements on large deflection angle, high natural frequency and compact size have general challenges. In this research, a 3D-printing compatible anti-symmetric compliant mechanism is proposed, composed of spatially distributed positive Poisson’s ratio structural unit (P-layer) and negative Poisson’s ratio structural unit (N-layer). Under the same tension, the P-layer and N-layer can generate transverse shrinkage deformation and expansion deformation respectively, thus driving the end-effector with a larger angular deflection without sacrificing the natural frequency. The proposed tilt stage with anti-symmetric compliant mechanism achieves a more compact size, as well as better motion behaviors. A theoretical model is also established to analyze the static performance and predict the output angle of the proposed design. The experiments show that the developed tilt stage can achieve a deflection range of 9.23 mrad and a natural frequency of 1086 Hz, with significant improvement over existing results. • Development of spatially distributed anti-symmetric compliant mechanisms compatible with 3D printing. • Working principle and model analysis on the thrust-tension based tilt motions. • Development of a high performance compact tilt stage with a large operating range (9.23 mrad) and a high natural frequency (1086 Hz). • Experimental validations of the proposed design and modeling method.

Изменения хрусталика при осложненной миопии. Возможности лечения

Cataracts are the leading cause of vision loss in patients over 50 years. In addition to senile cataracts, its earlier development due to various risk factors (for example, degenerative myopia characterized by lens opacity even in low myopia) is also an issue. This article discusses the pathogenesis of cataracts with a focus on oxidative stress, which is also important for myopia progression. The published and authors' data on the association between myopia and cataracts are addressed. The importance of early diagnosis of cataract in patients with myopia at the stage of lens suture compaction and its early radial and meridional opacities (that is possible with maximum mydriasis) is emphasized. Potential complex therapy with anti-cataract drops characterized by antioxidant effect is discussed as a pathogenetic approach to delay cataract progression in patients who (for various reasons) are not suitable for surgery. Recommendations for modifying the lifestyle to prevent cataract development are provided. KEYWORDS: degenerative myopia, myopic cataract, lens, oxidative stress, antioxidants, risk factors, drug treatment, pirenoxine. FOR CITATION: Rabadanova M.G., Oganezova J.G., Kremkova E.V., Yakh'yaeva M.M. Lens disorders in degenerative myopia. Treatment options. Russian Journal of Clinical Ophthalmology. 2023;23(4):207–212 (in Russ.). DOI: 10.32364/2311-7729-2023-23-4-6.

Numerical simulation analysis for the effect of water content on the intelligent compaction quality of roadbed

<abstract> <p>In the process of intelligent compaction of roadbeds, the water content of the roadbed is one of the important influencing factors of compaction quality. In order to analyze the effect of water content on the compaction quality of roadbeds, this paper is developed by secondary development of Abaqus finite element numerical simulation software. At the same time, the artificial viscous boundary was set to eliminate the influence of boundary conditions on the results in the finite element modeling process, so that the numerical simulation can be refined to model. On this basis, the dynamic response analysis of the roadbed compaction process is performed on the finite element numerical simulation results. This paper established the correlation between compaction degree and intelligent compaction index CMV (Compaction Meter Value) and then analyzed the effect of water content on the compaction quality for the roadbed. The results of this paper show that the amplitude of the vertical acceleration is almost independent of the moisture content, and the vertical displacement mainly occurs in the static compaction stage. The vertical displacement changes sharply in the first 0.5 s when the vibrating wheel is in contact with the roadbed. The main stage of roadbed compaction quality increase is before the end of the first compaction. At the end of the first compaction, the roadbed compaction degree increased rapidly from 80% to 91.68%, 95.34% and 97.41%, respectively. With the increase in water content, the CMV gradually increased. At the end of the second compaction, CMV increased slightly compared with that at the end of the first compaction and stabilized at the end of the second compaction. The water content of the roadbed should be considered to be set slightly higher than the optimal water content of the roadbed by about 1% during the construction of the roadbed within the assumptions of this paper.</p> </abstract>

Исследование влияния добавок LiCl и LiF на кинетику электроимпульсного плазменного спекания мелкозернистого оксида алюминия

The effect of the lithium chloride and lithium fluoride additives (2 wt. %) on the kinetics of Spark Plasma Sintering of industrial fine alumina powder was investigated. The Al2O3 + 2 % LiF powder was obtained by mixing the α-Al2O3 fine powders with the aqueous solution of LiF. The Al2O3 + 2 % LiCl fine powder was obtained by joint grinding of the components in a planetary mill. The sintering of the powders was performed with the heating rates of 10 and 50 °C/min up to the temperature corresponding to the end of the shrinkage. The ceramics sintered with the heating rate of 10 °C/min had the relative density of 97.4 – 98.7 %. The addition of lithium fluoride into the alumina powder was found to allow reducing the temperature of the beginning of the intensive powder shrinkage from 1400 – 1500 °C down to 1255 – 1335 °C. LiCl was shown to evaporate at low heating temperatures and not to affect the compaction intensity of the Al2O3 powder. The presence of the overheated LiF melt (not having enough time to evaporate from the specimen volume completely) in the ceramics leads to the appearance of the residual porosity and to the reduction of the hardness of the ceramics. Using the Young – Cutler equation, the powder compaction mechanisms were determined for pure alumina α-Al2O3 and for the powder compositions with the LiCl and LiF additives in the rapid heating conditions. The sintering activation energy was shown to be close to the one of the grain boundary diffusion. The LiF melt was found to promote the sliding of the Al2O3 fine particles during the low-temperature compaction stage.

ASPECTE PRIVIND COMPACTAREA DEȘEURILOR DIN CARTON ÎN PRESE VERTICALE CU FLUX DISCONTINUU

The paper analyses the compaction of cardboard waste in vertically stationary presses, the stages of making the bale of material and the forces resistant to the displacement of the cardboard pressing plate at each stage of compaction, the relationship between the piston stroke and the pressing forces, as well as the partial and total energy consumption of compaction. Some clarifications are made regarding the correlation between the piston stroke and the compaction time, respectively the forces resistant to compaction. A link shall also be established between the volume of pressed material and its mass, so that the final density of the bale of material can be specified.

Study on mechanical properties of cemented backfill with different mineral admixtures

In order to establish storages in mining goaf, calcium bentonite (Ca-B), slag powder (SP) and silica fume (SF) were added into the backfill to obtain a cemented backfill with high stability and certain anti-seepage function. Uniaxial compressive strength (UCS), porosity, permeability and scanning electron microscopy (SEM) tests were carried out. Results show that SP and SF can significantly improve the strength at the same level of incorporation, the highest increases are 216.37% and 125.51% compared with the control group, while Ca-B has strong swelling and low pozzolanic activity, the strength can only be increased by 32.83%, and the strength can be significantly reduced by 28.34% if the Ca-B content is too high. The incorporation of mineral admixtures can increase the number of closed pores in the compaction stage, and the damage mode of backfill can be changed with the increase of the incorporation amount. There is a power function relationship between permeability and porosity, permeability increases with the increase of porosity. The strong pozzolanic reaction of SP and SF can produce more gel compounds to block pore channels, refine pore size and reduce permeability. Compared with the control group, the permeability can be reduced by 46.05% and 36.84% at the highest, while Ca-B due to strong swelling, low activity, and insufficient reaction cause the backfill porous, and the permeability is greater than the control group under different incorporation amounts.

Effects of kneading and impact action on the movement of aggregates in asphalt mixtures during compaction

Current studies on the movement of asphalt mixture components and the formation of internal structures during compaction are lacking. Therefore, this article focuses on the effect of compaction and compaction methods on the movement and contact of mixture components. First, models of asphalt mixtures were established based on X-ray computed tomography (X-CT) and the discrete element method (DEM). Subsequently, compaction processes of the Marshall and Superpave gyratory compactor (SGC) method were simulated, and the model was verified using monitoring results of the smart rock. Finally, the macroscopic air voids, component contacts, and coarse aggregate trajectories were recorded and analyzed. The results showed that, in the early compaction stages, the compactness of the Marshall specimen increased rapidly, which also led to more resistance. The number of contact points and the contact force inside specimens gradually increased with compaction; however, the rate of this increase was different. The trajectories of coarse aggregates were affected by their location and compaction methods, especially the distance to the impacted side and to the center of the cross-section. An edge effect, namely lower compactness at the edges may also be caused by this difference. The movement of aggregates inside the Marshall specimen mainly occurred in the direction of impact. The kneading effect of the SGC method made aggregate particles move and rotate periodically, and compaction efficiency in the later stages was higher.

A Model of Stress-Damage-Permeability Relationship of Weakly Cemented Rocks under Triaxial Compressive Conditions.

To unravel the permeability variation mechanism of weakly cemented rocks (WCR), the paper conducted triaxial permeability tests on weakly cemented sandstones (WCS) collected from the Jurassic formation in northwest China. The paper identified the correlation of WCS permeability versus porosity, cementation structure, and mineral composition, further developing a model to characterize the WCS stress-damage-permeability relationship. The research indicated that the WCS permeability was initially high due to the naturally high porosity, large pore diameter, and loose particle cementation, thus favoring a significant decline as pore convergence in the compaction stage. In the residual stage, kaolinite and montmorillonite minerals disintegrated into water and narrowed fractures, causing a slight permeability increase from the initial to the maximum and residual stages. The WCS matrix fracturing was phenomenologically accompanied by clay mineral disintegration. By assuming that the matrix can be compressed, jointed, and fractured, the paper defined a damage variable D and accordingly developed a stress-damage-permeability relationship model that incorporated matrix compression, jointing, and fracturing. The model can describe the WCS permeability regime regarding the high initial permeability and slight difference of the maximum and residual permeabilities versus the initial.

Research on Fracture Characteristics and Energy Dissipation of Hard Rock under the Excitation of Ultrasonic Vibration

To promote the application of ultrasonic vibration rock crushing technology in underground rock-drilling engineering, it is necessary to investigate the damage and fracture characteristics of hard rock under the excitation of ultrasonic vibration. In this study, the brittle red sandstone was taken as the research object, the rock fracture experiments under the excitation of ultrasonic vibration were carried out, and the macrodeformation of rock samples was monitored by strain gauges. The experimental results show that the strain curve of rock samples under the excitation of ultrasonic vibration can be divided into the compaction stage, elastic deformation stage, and damage stage; with the increase in static load, the maximum intrusion depth and maximum failure depth of rock samples increase exponentially. To study the damage evolution and energy dissipation mechanism of rock samples under the excitation of ultrasonic vibration, a numerical model was established by using particle flow software PFC2D. The results show that the proposed model can effectively simulate the failure characteristics of rock samples under the excitation of ultrasonic vibration. Through the analysis of the displacement field, stress field, and dynamic fracture process of rock samples, the damage and fracture mechanism of rock samples under the excitation of ultrasonic vibration were revealed. In addition, the ultrasonic vibration simulation tests on rock samples were carried out under different static loads, and the number of rock cracks and energy dissipation process were monitored in real time. The results show that static loads can accelerate the initiation and propagation of cracks and improve the utilization rate of rock crushing energy.

Compaction characteristics assessment of cold mix patching materials through gyratory shear compactor

Cold mix patching materials (CMPMs) are widely employed in pothole repair due to ease of installation and environmental benefits. In order to generate long-lasting pavement repairs, CMPMs must guarantee adequate volumetric properties, which in turn determine a proper pavement serviceability. In this context, the present study aims to provide an improved understanding of the compaction process of CMPMs through a laboratory campaign based on gyratory compaction tests carried out under a wide range of energy. To this end, the volumetric response of nine ready-to-use CMPMs and the evolution of shear stress along their densification process have been investigated at different temperatures.Based on both densification and shear stress curves, two modelling approaches are here presented by the authors. Results demonstrate that the proposed s-shaped function enables densification curves to be studied with a high reliability and provides distinctive parameters to characterize the CMPMs at different stages of compaction. Moreover, the analysis of shear stress data through a two-stage model highlights a certain correlation among physical and mechanical responses of studied mixtures.

The Infrared Radiation Characteristics of Sandstone Fracture Seepage under Coupled Stress-Hydro Effect

Effective monitoring of rock fracture and seepage is an important information means to ensure the safety of geotechnical engineering. Therefore, sandstone samples were subject to uniaxial compression under different hydraulic conditions in the presence of infrared radiation and observation. This study uses the multiple infrared radiation indexes (ΔAIRT, IRV, VDIIT) and image data to analyze the influence of coupled stress-hydro effect of infrared radiation change on sandstone surface. The main findings are: (1) The surface temperature of sandstone samples rises in the compaction and linear elastic stages, keeps stable or decreases in the fracture development stage, and rapidly decreases in the post-peak failure stage. (2) The samples with internal water pressure not more than 0.30 MPa, surface temperature and load curve at the compaction and linear elastic stage have a strong power function relationship, which a coefficient of determination is 0.8900. (3) The IRV curve appears as a pulse jump at the time of water seepage. After that, both the fracture development and the post-peak failure stages have stepped up. The VDIIT curve also appears to be a pulse jump at the time of water seepage, and obvious up and down fluctuations exist before water seepage and fracture. (4) Based on the Pauta Criterion, by analyzing the values of VDIIT during the experiment, the early warning threshold of sandstone fracture seepage is determined to be 0.00559. The research finding can provide an experimental and theoretical basis for the early warning of flood accidents in underground rock engineering.

Assessment of Poorly Compactable Sands by Recycling and Recompaction: Experimental Program and Packing Particle Analysis.

Compaction is a common ground improvement technique based on the densification of soils for an energy level and optimum water content, mainly influenced by the particle size and curve gradation. Poorly compactable sands, characterized as cohesionless, fine and uniformly graded, are a challenge for earthworks since compaction is not effective due to the lack of a larger range of particle sizes to infill the voids and the compaction energy is not relevant either. These characteristics are common to other materials, i.e., desert sand, industrial or mining by-products or quarry fines, which are mostly discarded to landfill and replaced by proper soils, causing serious environmental issues. To enlarge the technical feasibilities of poorly compactable sands, reducing construction waste and raw material consumption, a mechanical stabilization, based on a repetitive series of recycling and recompaction without binder, is experimentally explored. The behavior observed is also analyzed from reported correlations and a packing particle approach, attending to densification stage, saturation degree, recompaction series, coordination number and packing density. The improvement achieved is moderate and dependent on the cycles applied, showing a characteristic repetitive pattern in the compaction curve, and approaching the estimated minimum void ratio and the theoretical maximum packing possibilities without degradation of the material.

Plastic deformation behavior of aluminum alloy fiber porous body and its filled tube under impact loading

The size of aluminum alloy fiber wire with a short side of 5mm, a long side of 10mm and an arc radius of 1mm were prepared from the raw material of 6061 aluminum alloy fiber with diameter of 0.15mm by Spring machine cutting, namely the structure size of 5×10mm bending aluminum alloy fiber. The aluminum alloy fiber porous body with different porosity were prepared by vacuum hot pressing sintering furnace, and it was sleeved with 6063 aluminum alloy round tube to prepare aluminum alloy fiber porous body filled tube. The impact test was carried out with drop hammer impact testing machine, The plastic deformation behavior of aluminum alloy fiber porous body and its filled tube under impact loading with different porosity was studied. The results show that the impact process of aluminum alloy fiber porous body can be divided into three stages: plastic platform stage, densification stage and unloading stage, the filled tube with aluminum alloy fiber porous body can be divided into four stages: elastic deformation stage, progressive buckling stage, densification stage and unloading stage. Low porosity will make more fibers, and more benefit the generation of the sintering necks, the plastic deformation strength increases with the porosity decrease. The coupling effect of the aluminum alloy tube and the aluminum alloy fiber porous body makes the filled tube absorb the same energy with shorter impact displacement, and has stronger impact resistance and better mechanical properties.

Plastic deformation behavior of bending aluminum fiber porous material under compressive load

The 6061 aluminum alloy wires with diameters of 0.15 mm and 0.20 mm were cut into different structural sizes of 5 × 10 mm and 10 × 15 mm by a spring machine to bend the aluminum alloy fibers, one is 5 mm short side, 10 mm long side, and 1 mm arc radius, and the other is 10 mm short side, 15 mm long side, and 1 mm arc radius. Special cylindrical molds are used to prepare folding sheets with different porosities using vacuum hot pressing sintering technology. Bent aluminum fiber porous material. The gas displacement method was used to detect the pore size and pore size distribution, and the Plastic Deformation Behavior were analyzed by quasi-static uniaxial compression test. Research shows that the material presents a three-stage stress-strain curve, from the initial nonlinear elastic deformation stage to the pseudo-platform stage and the densification stage, the wire diameter and structure of the material The smaller the size, the more conducive to the densification of the silk skeleton, and the smaller the average pore size formed, the higher the compressive strength.

Design of a compact long-stroke high-precision rigid-flexible coupling motion stage driven by linear motor

Design of a compact long-stroke high-precision rigid-flexible coupling motion stage driven by linear motor

Noncontact 3-D Orientation Control at Microscale: Hydrodynamic Out-of-Plane Rotation and In-Plane Rotation by Compacted Rotational Stage

In cloning, clinical <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in vitro</i> fertilization, gene research, and stem cell research, enucleation or injection of the individual cell is essential. Three-dimensional (3-D) orientation control of the target cell could significantly influence the operation success rate, which is still one of the main challenges in conventional micromanipulation. In this article, we give a cost-effective solution of the 3-D orientation control at the microscale combining the hydrodynamic out-of-plane rotation and the in-plane rotation by compacted rotational stage. We equipped a standard microinjection system with a single piezo-actuator and a 3-D printed compacted rotational stage. Using the resonance of the designed copper cantilever as the pipette holder and the Lissajous Principle, we extended the 1-D oscillation of the piezo-actuator to 2-D circular oscillation of the injecting micropipette. The circular oscillation could generate a whirling flow for noncontact immobilization and out-of-plane rotation of the target. After the out-of-plane rotation, the rotational stage was employed to realize the in-plane rotation, and a holding-position control strategy was proposed to compensate circular motion in global of the target. The performance of these two rotation methods has been tested by rotating microbeads with outer diameters of 98 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">μ</i> m. 3-D orientation control of the microbead and the mouse oocyte has been achieved, which indicates that the proposed method could be widely applied in the biomedical field.

Research on densification mechanism of Inconel 718 alloy miniature gear by electric field-assisted sintering

The densification mechanism of the electric field-assisted sintering (E-FAST) for Inconel 718 alloy miniature gears was studied using the Bernard-Granger model. Under the conditions of sintering temperature of 950 °C, 1000 °C and 1050 °C and dwelling time of 240 s, 300 s and 360 s, the Inconel 718 powders were subjected to E-FAST using the Gleeble thermal simulator, and the densification rate was up to 10−3 s−1. With the increase of the sintering temperature, the peak of the densification rate of the sintered sample was enlarged, and the time for the peak to appear became shorter. The densification of Inconel 718 alloy miniature gears was mainly concentrated in the dwelling stage. When the dwelling time reached 300 s, the densification rates of the samples under different temperature conditions were similar, indicating that the gear samples were close to full density at this time. Simulation and sintering test results show that the densification stages of the gear samples can be divided into low sintering stress stage with stress index n = 0.4 and high sintering stress stage with stress index n = 3.5. The apparent activation energy of the densification changes with the variation of the sintering stress stage.

Properties and ballistic tests of strong B4C-TiB2 composites densified by gas pressure sintering

B4C-TiB2 composites with classical 75/25 vol ratio were sintered by pressureless sintering with and without gas pressure application in the final stage of densification, using a novel prototypal furnace. A small fraction of WC was introduced through high energy milling of the starting powders with WC-Co spheres. High energy milling facilitated the densification thanks to incorporation of WC impurities acting as sintering aid, and size reduction of the starting powders. Strength, stiffness and toughness of the ceramic densified at 2050 °C via gas pressure sintering were even better than hot pressed composites at 1900 °C. Depth of Penetration tests on plates with 3–5 mm thickness demonstrated that the gas pressure sintered material had a superior performance compared to the hot pressed one. This work also revealed that hardness was not the property spotting the best ballistic performance.

Compaction Behavior and Damage Constitutive Model for Porous Cement Mortar under Uniaxial Cyclic Loads.

The void compression stage causes porous cement mortar to present special mechanical properties. In order to study the compaction behavior and the damage evolution of the porous material, cement mortar specimens with an average porosity of 26.8% were created and cyclic uniaxial compression tests were carried out. The irreversible strain accumulated in the tests was obtained by cyclic loading and unloading. As the secant modulus of the porous cement mortar increases with stress in the pre-peak deformation stage, its damage variable is defined according to the accumulated irreversible strain instead of modulus degradation. The strain-based damage indicator fitted with the damage evolution law is characterized by linear accumulation at the beginning and has an acceleration rate of about 0.3 in the pre-peak deformation stage, and the damage value converges to 1 at failure. Based on the Weibull distribution, a constitutive damage model of porous cement mortar is improved by considering both the damage evolution during the plastic deformation stage and the mechanical behavior in the compaction stage. The theoretical envelope curves obtained by the constitutive model are in good agreement with the experimental envelope curves of cyclic uniaxial compression in the compaction and pre-peak stages, and the average absolute error is about 0.54 MPa in the entire pre-peak stage, so the proposed damage constitutive model can characterize the damage-induced mechanical properties of porous cement mortar in the compaction and pre-peak stages.

Compression of Fibrous Assemblies: Revisiting the Stress–Density Relation

Abstract Many engineering materials are made from fibers, and fibrous assemblies are often compacted during the fabrication process. Compression leads to the formation of contacts between fibers, and this causes stiffening. The relation between the uniaxial stress, S, and the volume fraction of fibers, φ, is of power law form. The derivation of this relation based on micromechanics considerations takes as input the structural evolution represented by the dependence of the mean segment length of the network, lc, on the current density, ρ (ρ is defined as the total length of fiber per unit volume of the network). In this work, we revisit this problem while considering that the mean segment length should be defined exclusively by fiber contacts that transmit load. We use numerical simulations of the compression of crimped fiber assemblies to show that, when using this definition, ρ∼1/lc2 at large enough strains. Purely geometric considerations require that ρ∼1/lc, and we observe that this applies in the early stages of compaction. In pre-stressed networks, the density–mean segment length scaling is of the form ρ∼1/lc2 at all strains. This has implications for the relation between stress and the fiber volume fraction. For both ρ versus lc scalings, S∼(φn−φ0n), where φ0 is the initial or reference fiber volume fraction; however, n = 3 when ρ∼1/lc and n = 2 for ρ∼1/lc2. These predictions are compared with experimental data from the literature.