Compression Mode Research Articles

3D 변형 공정 지도 기반 AISI 4340 소재의 열간 단조 온도 및 변형률 속도 제어

This paper investigated the hot deformation behavior of an AISI 4340 material through high-temperature compression experiments. The compression tests were performed to obtain stress-strain curves at processing temperatures of 900, 1,000, 1,100, and 1,200℃, and the strain rates of 0.01, 0.1, 1, and 10 sSUP-1/SUP up to a true strain of 1.0 in the high-temperature compression mode of GleebleSUP®/SUP 3,500. A novel 3D processing map, constructed through power dissipation efficiency and Ziegler

Enabling Intelligent IoTs for Histopathology Image Analysis Using Convolutional Neural Networks.

Medical imaging is an essential data source that has been leveraged worldwide in healthcare systems. In pathology, histopathology images are used for cancer diagnosis, whereas these images are very complex and their analyses by pathologists require large amounts of time and effort. On the other hand, although convolutional neural networks (CNNs) have produced near-human results in image processing tasks, their processing time is becoming longer and they need higher computational power. In this paper, we implement a quantized ResNet model on two histopathology image datasets to optimize the inference power consumption. We analyze classification accuracy, energy estimation, and hardware utilization metrics to evaluate our method. First, the original RGB-colored images are utilized for the training phase, and then compression methods such as channel reduction and sparsity are applied. Our results show an accuracy increase of 6% from RGB on 32-bit (baseline) to the optimized representation of sparsity on RGB with a lower bit-width, i.e., <8:8>. For energy estimation on the used CNN model, we found that the energy used in RGB color mode with 32-bit is considerably higher than the other lower bit-width and compressed color modes. Moreover, we show that lower bit-width implementations yield higher resource utilization and a lower memory bottleneck ratio. This work is suitable for inference on energy-limited devices, which are increasingly being used in the Internet of Things (IoT) systems that facilitate healthcare systems.

Effect of thermal and hydrothermal aging on the crashworthiness of carbon fiber reinforced plastic composite tubes

Thin-walled structures constructed of fiber reinforced composites are increasingly being employed in engineering practice. However, there is limited investigation into their residual properties after high temperature and hygrothermal aging. The aim of this experimental investigation is to study how moisture absorption and high temperatures affect the mechanical characteristics of fiber reinforced plastic (FRP) composite tubes. A set of accelerated thermal and hygrothermal aging experiments are designed to imitate the service conditions of carbon fiber reinforced plastic (CFRP) structure in harsh environment. Based on the glass transition temperature obtained by dynamic mechanical analysis (DMA), the specimens are divided into two groups for various temperatures (25°C, 70°C, 100°C, 160°C) and hydrothermal aging (25°C, 70°C). The specimens of hydrothermal aging group are immersed for about 700 h to monitor the water absorption of the specimens in hygrothermal environments with different aging time. Aged composite tubes subjected to quasi-static axial compression are tested to identify compressive strength, failure modes and structural degradation process. The scanning electron microscope (SEM) is used to explore the microscopic failure mechanism of CFRP tubes. As temperature and moisture absorption rate increase, the crashworthiness characteristics decrease drastically; and the failure modes differ substantially with three different failure types identified. The crashworthiness of CFRP has a nonlinear relationship with temperature, but it is related to the glass transition temperature of the matrix. Furthermore, moisture absorption can be divided into two stages and temperature affects the moisture absorption of CFRP. Microscopically, the morphology and bonding conditions between fiber and resin is found to change significantly on the microscale as a result of various temperatures and hydrothermal aging.

Microtwinning in the nickel-based superalloy CM247LC during compression tests

ABSTRACT We have studied the variations in the compressive yield strength and deformation modes of the directionally solidified nickel-based superalloy CM247LC with temperature. It is found that the yield strength of the alloy only fluctuates in a small range with temperature when the deformation temperature is below 800 °C. Whereas, as the temperature is raised further, the strength decreases dramatically. After a small plastic strain, the substructures in the alloy are investigated using transmission electron microscope. It is startling to find large numbers of APB (anti-phase boundary)-coupled a/2 < 011 > dislocation pairs, isolated stacking faults and extended stacking faults as well as microtwins in the alloy at temperatures between 25 and 950 °C. Whereas, at 1000 °C, although dislocations bypassing γ′ particles via climb dominates the plastic deformation, two matrix dislocations with different Burgers vectors collectively penetrating γ′ particles, APB shearing and shearing of γ′ particles by partial dislocations also take place during plastic deformation. On the ground of the microstructural observations, correlation between the flow stress and deformation modes is discussed.

Eccentric compression behaviour and assessment of CFET short columns offering spherical-cap gaps

This paper designs and tests a total of 14 specimens to explore the effect of load eccentricity and spherical-cap gap on the compressive strength, ductility, failure modes, and strain distribution of the concrete-filled elliptical steel tubular (CFET) short columns with spherical-cap gaps. A finite element (FE) model of the eccentrically-pressured CFET short column is established by taking the characteristics of spherical-cap gap and elliptical cross-section into consideration. Extensively parametric studies on the impact of various geometric and material variables are further developed via FE analytical models. Intensive mechanical responses, such as the contact pressure between concrete core and hollow steel section (HSS) and the compressive stress at the mid-height cross-section, are presented as well. Based on the comparison between the test results and the predicted data obtained from the design provisions in specifications EN 1994–1-1, AISC 360–16, and GB 50936–2014, proper design formulae for evaluating the eccentric compressive strength of the CFET-SG short columns are proposed. The research results show that the existence of the spherical-cap gap significantly weakened the interaction between the HSS and the concrete core, leading to a reduction in the eccentric compressive strength and ductility behaviour. The concrete around the gap region appeared brittle collapse due to the shrinking confining effect of the HSS, and the HSS exhibited inward and outward local buckling because of the lack of concrete supporting action. The observations of this paper may furnish a scientific reference for the performance evaluation and prevention measures of CFET short columns with spherical-cap gap defects.

Compressive strength characteristics of hybrid fiber-reinforced cemented soil

ABSTRACT Cemented soil commonly faces issues regarding strength, cracking resistance, and water stability when used in airstrip pavements. Three kinds of soil samples (low-liquid limit clay, high-liquid limit clay, and clayey sand), four kinds of fibers (basalt fiber, glass fiber, fine polypropylene fiber, and coarse polypropylene fiber), and one curing agent (cement) were analyzed in a systematic investigation of the compressive strength of fiber-reinforced cemented soil based on unconfined compressive strength (UCS), water stability, and failure mode. When 38 mm coarse polypropylene fiber at 0.3% content was mixed with 12 mm fine polypropylene fiber at 0.3% content, the hybrid fiber-reinforced cemented soil prepared after 7 d of saturated curing achieved UCS values of 4.18 (low-liquid limit clay), 4.36 (high-liquid limit clay), and 4.16 MPa (clayey sand), which satisfied airstrip requirements for the strength of base course. In this study, coarse polypropylene fiber was adopted and mixed with fine fiber to give full play to their respective advantages and effectively enhance the mechanical properties of cemented soil. The research results improved the understanding of the mechanical properties and reinforcement mechanism of coarse and fine fiber reinforced cemented soil in theory, and enriched the materials and methods of airstrip construction in engineering.

A 13 Gbps 1:16 deserializer ASIC for NICA multi purpose detector project

This paper presents the design and test results of a 13 Gbps 1:16 deserializer ASIC fabricated in a 55 nm CMOS technology for Nuclotron-based Ion Collider fAcility (NICA) Multi Purpose Detector (MPD) project. The deserializer would be used in the downlink data transmission of MPD readout system to recover the serial data from the back-end to the parallel data for the front-end. The ASIC adopts a tree-type structure, consisting of a high-speed data receiver (RXDATA), a high-speed clock receiver (RXCLK), four levels of demultiplexer (DEMUX) modules, clock dividers and 16 Low-Voltage Differential Signaling (LVDS) drivers. The demultiplexer modules are composed of different numbers of high-speed DEMUX unit and low-speed DEMUX unit. The high-speed DEMUX unit and the high-frequency clock divider adopt an optimized compressed current mode logic (CML) differential structure to ensure the bandwidth with limited voltage headroom. The low-speed DEMUX unit and the low-frequency clock divider use CMOS latch to save power consumption. The duty cycle correction (DCC) circuit and the clock aligner are employed in the clock paths to ensure the correct duty cycle and aligned clock edges. In the chip test, the ASIC receives 13 Gbps serial data and outputs 16 channels of 812.5 Mbps data correctly with wide-open eye diagram. The tested power consumption is 203 mA with 1.2 V power supply including the RXDATA, the RXCLK and the 16 channels of LVDS drivers, and the core power consumption is 122.7 mA.

ZnO Nanowire-Based Piezoelectric Nanogenerator Device Performance Tests

Over the past two decades, the quick development of wireless sensor networks has required the sensor nodes being self-powered. Pushed by this goal, in this work, we demonstrated a ZnO nanowire-array-based piezoelectric nanogenerator (NG) prototype, which can convert mechanical energy into electricity. High-quality single crystalline ZnO nanowires, having an aspect ratio of about 15, grown on gold-coated silicon substrate, were obtained by using a low-cost and low-temperature hydrothermal method. The NG-device fabrication process has been presented in detail, and the NG’s performance has been tested in both compression and vibration modes. Peak power of 1.71 µW was observed across an optimal load resistance of 5 MΩ for the ZnO nanowires-based NG, with an effective area of 0.7 cm2, which was excited in compression mode, at 9 Hz, corresponding to ~38.47 mW/cm3 volume-normalized power output. The measured voltage between the top and bottom electrodes was 5.6 V. In vibration mode, at 500 Hz, the same device showed a potential of 1.4 V peak-to-peak value and an instantaneous power of 0.04 μW, corresponding to an output power density of ~0.9 mW/cm3.

Parametric Instability: An Evolutive Mechanism for the Alfvénic Turbulence in the Solar Wind

Fluctuations in fast streams or in slow Alfvénic streams of the solar wind, and in the high-latitude wind, are characterized by high cross-helicity and a low level of compressions. Such properties, which are typical of Alfvénic fluctuations, tend to decline with increasing heliocentric distance. Parametric decay, where the energy of an initial Alfvén wave is progressively transferred to both backward-propagating Alfvén and compressive modes, has been proposed as a mechanism responsible for such a behavior. Over the years, the parametric process has been studied, both analytically and numerically, in many configurations, from monochromatic waves to increasingly complex situations which include broad-band turbulent configurations with one- and two-dimensional spectra. In this paper, we give a brief review of this theoretical development, discussing its relevance in the context the evolution of Alfvénic turbulence in the solar wind.

Experimental study on the effects of particle characteristics and pressurization methods on powder compression

Both the particle characteristics and the pressurization methods have an important influence on powder compression behavior. Compression of powder with different average particle sizes, sphericity and adhesion were experimentally investigated by the FT4 rheometer and the pressurized visualization tank. The difference in compressibility caused by particle characteristics and pressurization methods were analyzed. The results show that the smaller the average particle size, the higher the sphericity and the greater the adhesion, the greater the compressibility of the powder. In the experimental range, the effect of gas pressurization is less than mechanical pressurization on powder compression. The relationship between normal stress and gas pressurization rate was proposed and the mechanism of different pressurization methods was also discussed with compression position and mode.

Compressive performance of H-shaped aluminium alloy members with web openings

In this study, experimental, numerical, and theoretical approaches are adopted to comprehensively investigate the compressive bearing capacity and failure modes of H-shaped aluminium alloy members with web openings. The influence of the opening parameters, section size, and slenderness ratio on the bearing capacity of such alloy members is analysed, and a calculation method is presented. Finite element models are established in Abaqus with the same configurations as the test specimens. The following conclusions are drawn from the analysis results: 1) The web openings weaken the practical section and destroy its continuity. Moreover, they affect the force flow transmission, thereby reducing the bearing capacity of the component and changing its failure mode. 2) Web openings have significantly larger impact on members with smaller slenderness ratios. The failure modes of members with different slenderness ratios are therefore different. 3) When the slenderness ratio is approximately 60, the weakening of the load displacement along the strong axis due to the web openings is significantly higher than that along the weak axis. 4) When the opening ratio exceeds 0.7, the openings greatly affect the stability of the components. In contrast, when the opening ratio is less than 0.3, the openings have negligible impact on the component stability. The numerical and theoretical analysis results are compared and verified by the experimental results.

Optimization of Piezoresistive Strain Sensors Based on Gold Nanoparticle Deposits on PDMS Substrates for Highly Sensitive Human Pulse Sensing

In this study, highly-sensitive piezoresistive strain sensors based on gold nanoparticle thin films deposited on a stretchable PDMS substrate by centrifugation were developed to measure arterial pulse waveform. By controlling carbon chain length of surfactants, pH value and particle density of the colloidal solutions, the gauge factors of nanoparticle thin film sensors can be optimized up to 677 in tensile mode and 338 in compressive mode, and the pressure sensitivity up to 350. Low pH and thin nanoparticle films produce positive influences to superior gauge factors. It has been demonstrated that nanoparticle thin film sensors on PDMS substrates were successfully applied to sense arterial pulses in different body positions, including wrist, elbow crease, neck, and chest.

Solenoidal turbulent modes and star formation efficiency in Galactic plane molecular clouds

ABSTRACT It is speculated that the high star formation efficiency observed in spiral-arm molecular clouds is linked to the prevalence of compressive (curl-free) turbulent modes, while the shear-driven solenoidal (divergence-free) modes appear to be the main cause of the low star formation efficiency that characterizes clouds in the Central Molecular Zone. Similarly, analysis of the Orion B molecular cloud has confirmed that, although turbulent modes vary locally and at different scales within the cloud, the dominant solenoidal turbulence is compatible with its low star formation rate. This evidence points to intercloud and intracloud fluctuations of the solenoidal modes being an agent for the variability of star formation efficiency. We present a quantitative estimation of the relative fractions of momentum density in the solenoidal modes of turbulence in a large sample of plane molecular clouds in the 13CO/C18O (J = 3 → 2) Heterodyne Inner Milky Way Plane Survey (CHIMPS). We find a negative correlation between the solenoidal fraction and star formation efficiency. This feature is consistent with the hypothesis that solenoidal modes prevent or slow down the collapse of dense cores. In addition, the relative power in the solenoidal modes of turbulence (solenoidal fraction) appears to be higher in the Inner Galaxy declining with a shallow gradient with increasing Galactocentric distance. Outside the Inner Galaxy, the slowly, monotonically declining values suggest that the solenoidal fraction is unaffected by the spiral arms.

Microbiological Profile of the Implantation Zone under Different Mechanical Compression of Percutaneous Implants: Experimental Study

Background. Infection of percutaneous implants in patients with limb amputation is the most common complication.&#x0D; Aim of the study evaluation of the microflora in the implantation zone depending on the mechanical compression of the implant in conditions of its additional external fixation.&#x0D; Methods. The study was performed on 36 male rabbits. The tibia of all the rabbits was sawn at the border of the upper and middle parts. The medullary canal was reamed and a percutaneous implant was placed in the tibial stump. The segment and the implant were fixed with an Ilizarov apparatus. An additional compression device was installed in 30 animals. We used 5 compression modes, accordingly, 6 experimental groups were formed, 6 animals in each: group 1 without compression, group 2 compression on the implant with force of 0.053 N/mm2, group 3 compression on the implant with force of 0.105 N/mm2, group 4 compression on the implant with force of 0.158 N/mm2, group 5 compression on the implant with force of 0.211 N/mm2, group 6 compression on the implant with force of 0.263 N/mm2. The restraint was removed 6 weeks after implantation for a total follow-up of 26 weeks. The microflora of the place where the implant enters the skin (the implant / skin interface) was investigated, the level of blood leukocytes and the level of C-reactive protein in blood serum were determined.&#x0D; Results. On days 9-10 after implantation, significant differences in the microbial landscape were found at the site of the exit of the metal implant in animals of different groups. The largest number of strains was found in animals of groups 1, 5 and 6, the smallest in groups 2 and 3. The most frequently detected strains: S. saprophyticus and Enterococcus spp. It was found that the greatest statistically significant increase in the level of CRP in the blood serum was observed in animals of group 6. The level of leukocytes in animals of all groups did not change statistically significantly relative to preoperative values. Animals with better osseointegration (groups 2 and 3 no cases of implant loss) showed a minimal number of growing strains.&#x0D; Conclusions. The microbiological profile of the implantation zone of percutaneous implants changes depending on the amount of mechanical compression. The optimal mode is 0.053-0.105 N/mm2.

Comprehensive Characterization of Solution-Cast Pristine and Reduced Graphene Oxide Composite Polyvinylidene Fluoride Films for Sensory Applications.

Pristine and doped polyvinylidene fluoride (PVDF) are actively investigated for a broad range of applications in pressure sensing, energy harvesting, transducers, porous membranes, etc. There have been numerous reports on the improved piezoelectric and electric performance of PVDF-doped reduced graphene oxide (rGO) structures. However, the common in situ doping methods have proven to be expensive and less desirable. Furthermore, there is a lack of explicit extraction of the compression mode piezoelectric coefficient () in ex situ rGO doped PVDF composite films prepared using low-cost, solution-cast processes. In this work, we describe an optimal procedure for preparing high-quality pristine and nano-composite PVDF films using solution-casting and thermal poling. We then verify their electromechanical properties by rigorously characterizing -phase concentration, crystallinity, piezoelectric coefficient, dielectric permittivity, and loss tangent. We also demonstrate a novel stationary atomic force microscope (AFM) technique designed to reduce non-piezoelectric influences on the extraction of in PVDF films. We then discuss the benefits of our measurements technique over commercially sourced piezometers and conventional piezoforce microscopy (PFM). Characterization outcomes from our in-house synthesized films demonstrate that the introduction of 0.3%w.t. rGO nanoparticles in a solution-cast only marginally changes the -phase concentration from 83.7% to 81.7% and decreases the crystallinity from 42.4% to 37.3%, whereas doping increases the piezoelectric coefficient by 28% from = 45 pm/V to = 58 pm/V, while also improving the dielectric by 28%. The piezoelectric coefficients of our films were generally higher but comparable to other in situ prepared PVDF/rGO composite films, while the dielectric permittivity and -phase concentrations were found to be lower.

Field Line Resonances and Cavity Modes at Earth and Jupiter

Ultra-Low-Frequency (ULF) waves provide a means for the rapid propagation of energy and field-aligned current in planetary magnetospheres. At Earth, the ULF frequency range is usually defined as including waves with periods of 0.2–600 s; however, at Jupiter these waves can extend to periods of tens of minutes. In both magnetospheres, shear mode Alfvén waves can form field line resonances that exist between the ionospheres, with periods of a few minutes at Earth and a few tens of minutes at Jupiter. A major distinction between these two magnetospheres is in the density distribution. Earth has a dense ionosphere full of heavy ions, an extended, cold plasmasphere and a relatively low-density plasma sheet. In contrast, at Jupiter, the ionosphere is largely hydrogen (both in atomic form and in the H3+molecular ion), there is no appreciable plasmasphere and the plasma disk is dense and populated with heavy ions (largely sulfur and oxygen) originating at the moon Io and to some extent from other moons. As at Earth, the sharp Alfvén speed gradient above the ionosphere forms an ionospheric Alfvén resonator at Jupiter with periods of seconds. Furthermore, the high-latitude lobes at Jupiter have very low density and a resonant structure can be formed by waves bouncing between the ionosphere and the dense plasma disk. This structure leads to periods of tens of seconds. Finally, the dense Io plasma torus and plasma sheet provide conditions for compressional cavity modes to form in this region. Thus, the structure of the field line resonance modes is quite different at the two planets. Implications of these resonances on auroral particle acceleration will be discussed.

Dynamic Mechanical Properties of TC11 Titanium Alloys Fabricated by Wire Arc Additive Manufacturing.

To study the compressive mechanical properties and failure modes of TC11 titanium alloy fabricated by wire arc additive manufacturing (WAAM) technology in a large strain rate range at room temperature, the quasi-static and dynamic compression tests were carried out. In addition, optical microscopy (OM) and scanning electron microscopy (SEM) were employed to observe the metallographic structure and fracture morphology, respectively. The stress–strain curves in the range of 0.001 s−1–4000 s−1, original and post-deformation microstructures, macroscopic damage patterns, and microscopic fracture morphology were obtained at two different loading directions, including the scanning and deposition directions, respectively. In uniaxial compression experiments, the material showed little difference in mechanical properties between the scanning and deposition directions, exhibiting a strain rate strengthening effect. However, the strain rate sensitivity of the material under quasi-static loading conditions is much less than that under dynamic loading conditions. In addition, combining the stress–strain curve with the fracture morphology analysis, the plasticity in the scanning direction is better than in the deposition direction. Based on the experimental results, a modified Johnson–Cook (JC) constitutive model considering strain rate sensitivity and the effect of strain rate on strain hardening was proposed, and the parameters were determined using a Multiple Population Genetic Algorithm (MPGA). The obtained constitutive model is in good agreement with the experimental data, which can provide a reference for the engineering numerical calculation of TC11 titanium alloy for WAAM. This study also provides a fundamental databank for the application and design of WAAM TC11 alloy in the manufacturing of large and complex structural parts.

Concrete-filled high strength steel tube stub columns after exposure to fire: Testing, numerical modelling and design

This paper reports experimental and numerical investigations into the structural behaviour and residual capacity of concrete-filled high strength steel tube (CFHST) stub columns after exposure to fire. The experimental investigation was conducted on twelve square CFHST stub column specimens after exposure to the ISO-834 standard fire for 15 min, 30 min and 45 min and four reference specimens at ambient temperature. The test results, including failure loads, load–end shortening curves, initial compressive stiffnesses and failure modes, were fully reported and discussed. A numerical investigation was subsequently conducted, where thermal and mechanical finite element models were developed and validated against the test results, and afterwards used to performed parametric studies to generate further numerical data over a wide range of cross-section dimensions. Owing to the absence of design codes for composite structures after exposure to fire, the relevant ambient temperature design rules, as set out in European code, American specification and Australian/New Zealand standard, were evaluated, using post-fire material properties, for their applicability to post-fire CFHST stub columns, based on the test and numerical data. The evaluation results revealed that all the three design codes generally yield accurate failure load predictions for CFHST stub columns after exposure to fire.

The driving mode of shock-driven turbulence

ABSTRACT Turbulence in the interstellar medium (ISM) is crucial in the process of star formation. Shocks produced by supernova explosions, jets, radiation from massive stars, or galactic spiral-arm dynamics are amongst the most common drivers of turbulence in the ISM. However, it is not fully understood how shocks drive turbulence, in particular whether shock driving is a more solenoidal (rotational, divergence-free) or a more compressive (potential, curl-free) mode of driving turbulence. The mode of turbulence driving has profound consequences for star formation, with compressive driving producing three times larger density dispersion, and an order of magnitude higher star formation rate than solenoidal driving. Here, we use hydrodynamical simulations of a shock inducing turbulent motions in a structured, multiphase medium. This is done in the context of a laser-induced shock, propagating into a foam material, in preparation for an experiment to be performed at the National Ignition Facility (NIF). Specifically, we analyse the density and velocity distributions in the shocked turbulent medium, and measure the turbulence driving parameter $b=(\sigma _{\rho /\langle \rho \rangle }^{2\Gamma }-1)^{1/2}(1-\sigma _{\rho /\langle \rho \rangle }^{-2})^{-1/2}\mathcal {M}^{-1}\Gamma ^{-1/2}$, with the density dispersion σρ/〈ρ〉, the turbulent Mach number $\mathcal {M}$, and the polytropic exponent Γ. Purely solenoidal and purely compressive driving correspond to b ∼ 1/3 and b ∼ 1, respectively. Using simulations in which a shock is driven into a multiphase medium with structures of different sizes and Γ &amp;lt; 1, we find b ∼ 1 for all cases, showing that shock-driven turbulence is consistent with strongly compressive driving.

A coupled smeared crack-plasticity model in incremental sequentially linear analysis for mixed failure modes

In this paper, a coupled smeared crack-plasticity model is proposed in incremental sequentially linear analysis (ISLA) to simulate mixed failure modes of tension, shear and compression. ISLA provides a robust and extensible solution for quasi-brittle materials. The solution search path follows damage cycles sequentially with secant stiffness corresponding to local damage increments, which traces both damage history (explicit) and displacement history (implicit). The proposed rotating smeared crack model resolves the limitations of a purely rotating crack model in the case that the smallest and the largest principal stress value are almost the same or the situation that the principal directions interchange between the beginning and the end of a load step. ISLA with the proposed constitutive model were demonstrated by mixed flure modes of the in-plane tests with large overburdens of a double clamped short wall and a cantilever long wall. Stable post-peak results were computed for large displacements, and localized crack propagation was computed robustly and correctly.