Peak Compression Research Articles

Calibration and Validation of Simulation Parameters for Maize Straw Based on Discrete Element Method and Genetic Algorithm-Backpropagation.

There is a significant difference between the simulation effect and the actual effect in the design process of maize straw-breaking equipment due to the lack of accurate simulation model parameters in the breaking and processing of maize straw. This article used a combination of physical experiments, virtual simulation, and machine learning to calibrate the simulation parameters of maize straw. A bimodal-distribution discrete element model of maize straw was established based on the intrinsic and contact parameters measured via physical experiments. The significance analysis of the simulation parameters was conducted via the Plackett-Burman experiment. The Poisson ratio, shear modulus, and normal stiffness of the maize straw significantly impacted the peak compression force of the maize straw and steel plate. The steepest-climb test was carried out for the significance parameter, and the relative error between the peak compression force in the simulation test and the peak compression force in the physical test was used as the evaluation index. It was found that the optimal range intervals for the Poisson ratio, shear modulus, and normal stiffness of the maize straw were 0.32-0.36, 1.24 × 108-1.72 × 108 Pa, and 5.9 × 106-6.7 × 106 N/m3, respectively. Using the experimental data of the central composite design as the dataset, a GA-BP neural network prediction model for the peak compression force of maize straw was established, analyzed, and evaluated. The GA-BP prediction model's accuracy was verified via experiments. It was found that the ideal combination of parameters was a Poisson ratio of 0.357, a shear modulus of 1.511 × 108 Pa, and a normal stiffness of 6.285 × 106 N/m3 for the maize straw. The results provide a basis for analyzing the damage mechanism of maize straw during the grinding process.

A biomechanical study comparing the compression force and osseous area of contact of two screws fixation techniques used in ankle joint arthrodesis model

IntroductionArthrodesis of a (diseased) ankle joint is usually performed to achieve pain relief and stability. One basic principle of arthrodesis techniques includes rigid fixation of the surfaces until union. It seems plausible that stable anchoring and homogeneous pressure distribution should be advantageous, however, it has not been investigated yet. The aim is to achieve uniform compression, as this is expected to produce favorable results for the bony fusion of the intended arthrodesis. Numerous implants with different biomechanical concepts can be used for ankle fusion. In this study, headless compression screws (HCS, DePuy Synthes, Zuchwil, Switzerland) were compared biomechanically to an alternative fixation System, the IOFix device (Extremity Medical, Parsippany, NJ, USA) in regard to the distribution of the compression force (area of contact) and peak compression in a sawbone arthrodesis-model (Sawbones® Pacific Research Laboratories, Vashon, WA, USA).This study aims to quantify the area of contact between the bone interface that can be obtained using headless compression screws compared to the IOFix. In current literature, it is assumed, that a large contact surface with sufficient pressure between the bones brings good clinical results. However, there are no clinical or biomechanical studies, that describe the optimal compression pressure for an arthrodesis.Material and methodsTwo standardized sawbone blocks were placed above each other in a custom-made jig. IOFix and headless compression screws were inserted pairwise parallel to each other using a template for a uniform drilling pattern. All screws were inserted with a predefined torque of 0.5 Nm. Pressure transducers positioned between the two sawbone blocks were compressed for the measurement of peak compression force, compression distribution, and area of contact.ResultsWith the IOFix, the compression force was distributed over significantly larger areas compared to the contact area of the HCS screws, resulting in a more homogenous contact area over the entire arthrodesis surface. Maximum compression force showed no significant difference.ConclusionThe IOFix system distributes the compression pressure over a much larger area, resulting in more evenly spread compression at the surface. Clinical studies must show whether this leads to a lower pseudarthrosis rate.

Mitigating the brittle behavior of compression cast concrete using polypropylene fibers

Compression casting enhances mechanical properties, durability, and microstructure of concrete while reducing cement usage and carbon emissions. However, its brittleness restricts its widespread use. This study aims to mitigate the brittleness of compression cast concrete (CCC) through fiber reinforcement. Eleven concrete mixes with varied volumetric ratios (0, 0.05, 0.1, 0.15, 0.2, and 2 %) and aspect ratios (250, 313, and 396) of polypropylene fibers were prepared. Both compressed and uncompressed specimens were analyzed for compressive stress-strain behavior, compressive strength, modulus of elasticity, toughness, specific toughness, and microstructure. Results show that CCC specimens have steeper and shorter descending segments on their compressive stress-strain curves than uncompressed concrete, indicating brittleness. Adding polypropylene fibers significantly reduces this brittleness by enhancing the post-peak compressive stress-strain behavior of CCC. Fiber reinforced CCC specimens exhibit significant enhancements in compressive strength, modulus of elasticity, and toughness (up to 68 %, 34 %, and 38 % respectively) compared to uncompressed plain concrete. Mercury intrusion porosimetry, scanning electron microscopy, and backscattered electron imaging confirm that compression casting strengthens the interfacial transition zone of both plain and fiber reinforced CCC. Proposed empirical models accurately forecast the modulus of elasticity, compressive strength, and peak compression strain for both types of CCC. Comparisons with existing models show that Nematzadeh and GB50010–2010 models effectively predict the ascending part of the compressive stress-strain curves of plain and fiber reinforced CCC. These findings affirm that polypropylene fibers effectively reduce the brittleness of CCC, promoting its practical application.

Deformation mode and energy absorption of self-assembly CFRP composites cellular structure by 3D printing

Compared with traditional cellular structures, self-assembly structures exhibit significantly higher assembly flexibility, allowing for more scientific and rational protection design in the realm of structural protection. Moreover, self-assembly structure had the potential to mitigate the rapid decrease of load bearing capacity often observed in integral molding due to plastic hinge failure between adjacent cells. Therefore, self-assembly CFRP composites cellular structure was proposed, Quasi-static compression test and finite element simulation were carried out to analyze the deformation modes and energy absorption characteristics. Hexagon (H) structure formed a shear failure band, and re-entrant (R) structure was fully densified with large deflection. The deformation of inclined struts of HR and RH structures were well compatible. The total absorption energy of R structure was max, and H structure was min. The specific energy absorption and mean compression force of two-layer structures were higher, but the increasing number of layers could reduce the peak compression force, RH and R structures showed excellent energy absorption ability.

Effect of 3D printed skeleton shapes on strength behavior, stress evolution and microstructural response of cement-based tailings backfills

The inherent brittle behavior of cement-based tail backfill (CTB) poses some challenges that can significantly impact the safety and effectiveness of underground mining operations. Due to its propensity for abrupt and catastrophic failure without considerable deformation, CTB can endanger both the structural solidity of mined-out cavities and workers’ security. Hence, implementing appropriate strategies is critical to mitigate the risks associated with the brittle nature of CTB. An experiment investigation was commenced to consider the influence of diverse 3D printed polymer reinforcement geometries - specifically, hexagon, staggered quadrilateral, and rhomboid shapes - on strength behavior, stress evolution, and microstructural response of CTB via peak compression strength test plus scanning electron microscope observations. Lab findings specified a decrease in fill strength upon adding these polymer reinforcements. Specifically, the N-3D-PP-reinforced CTB exhibited a strength of 0.61 MPa. In comparison, the reinforced samples showed lower strengths of 0.39 MPa for the hexagon shape, 0.44 MPa for the staggered quadrilateral shape, and 0.45 MPa for the rhomboid shape. The toughness of CTB incorporating 3D-PP was higher than that of N-3D-PP ones. The optimal shape for an ideal toughness was the rhomboid shape, with a value of 58.06 KJ.m−3. N-3D-PP-reinforced CTB specimens exhibited a semi-brittle behavior, while 3D-PP-reinforced CTBs displayed a more ductile response with high total and dissipative energies. Cracks in N-3D-PP reinforced CTB were tensile, and mainly a combination of tensile and shear in 3D-PP reinforced CTB. Despite enhanced toughness, the presence of pores, the poor interfacial bonding between the CTB matrix and the 3D-PP, the low volume of polymer reinforcement, and the potential disruption of cement particle packing compromised the CTB’s overall strength. This research highlights the potential of 3D-printed reinforcements in transforming the landscape of mining backfill technology. The findings pave the way for the widespread adoption of 3D-printed polymer-reinforced CTB in metalliferous mines, promoting safer, more productive, and, ultimately, more profitable underground mining operations.

Laboratory Study of Liquid Nitrogen Cryo-Fracturing as an Environmentally Friendly Approach for Coalbed Methane (CBM) Reservoirs

This study evaluated two distinct cryo-fracturing techniques using liquid nitrogen (LN2). The evaluation included tests for peak compression strength, acoustic emission, and energy absorption. The experiments compared single-exposure freezing time (FT) and multiple-exposure freezing–thawing cycle (FTC) processes on dried specimens. The outcomes indicated that FTC experiments demonstrated lower uniaxial compression stress (UCS) values compared to FT experiments because, during the thawing phase, the ice inside the pores reverts to liquid as the temperature rises. The difference between average baseline experiments versus FT180 and FTC6 indicated a reduction in stress of 14.5% and 38.5%, respectively. The standard error of our experiments ranged from 0.58% for FT60 to 5.35% for FTC6. The damage factor follows a downward trend in both FT and FTC experiments as the time of LN2 treatment augments. The amount of energy that can be absorbed in elastic or plastic deformation before failure is less for FTC specimens with the same total LN2 exposure time. Samples undergoing the freezing time process demonstrate a greater and denser quantity of acoustic emissions in comparison to freezing–thawing cycle processes, suggesting a positive correlation with uniaxial compressive strength outcomes. The large network of fractures formed by the FTC and PFTC techniques indicated that they have the greatest potential as stimulation approaches. The engineering results were improved by adding the geological context, which is essential to apply these findings to coals that have comparable origins.

An experimental and numerical investigation into compressive failure of pyramidal lattice sandwich structures fabricated using stereolithography technology

AbstractThe pyramid lattice sandwich structure, characterized by high load‐bearing capacity, lightweight nature, and fully open internal space, is considered an extremely promising super‐strong structure. Stereolithography technology was utilized to achieve the monolithic formation of single‐layer multi‐cell pyramidal lattice sandwich structures. Quasi‐static compression tests and finite element simulations were conducted to characterize the compressive properties and failure modes. Results indicate that the compressive strength, compressive modulus, specific strength, and specific stiffness of the single‐layer multi‐cell pyramidal lattice sandwich structure increase as the relative density increases. Moreover, fracture failure was observed in the structures with various relative densities. Additionally, the compressive failure of multi‐layer density gradient pyramidal lattice sandwich structures was investigated. Experimental and numerical findings indicate that the optimal density gradient scheme for the ZCMLG structure is I‐III‐II, resulting in a peak compression force that is 342.14% and 288.55% higher than that of the ZAMLG and ZBMLG structures, respectively.

Investigation on mechanical behaviors and energy characteristics of deep-buried marble in a hydraulic tunnel in Southwest China

Shear behavior of rock is of great significance to the stability of deep-buried rock in transportation geotechnical engineering. A series of direct shear tests are carried out on deep-buried marble with different size and shape to focused on the mechanical properties and size shape effects of deeply buried marble, which have been less studied previously. The results show that the size and shape of the specimen have a relatively small impact on the trend of shear stress-shear displacement curve. The failure morphology at the front and rear surfaces shows a significant normal stress effect. Some properties of specimens with different sizes and shapes increase with increasing normal stress, but the dilation angle generally decreases with the increasing normal stress. With the increase of the shear plane size of intact specimen, the cohesion decreases gradually while the internal friction angle increases steadily. The difference value in peak strain between axial compression and direct shear tests is relatively small while it is huge for the peak compression and peak shear strength. The results in this study are beneficial for further understanding the shear mechanics, energy evolution process and size effects of deep-buried rock in transportation geotechnical engineering.

Fabrication and mechanical properties of thermoplastic corrugated sandwich panel with enhanced face‐core interface

AbstractThermoplastic sandwich structures are widely utilized in engineering fields due to their high specific strength and stiffness, recyclability, and impact toughness. The face‐core interface strength is crucial to maximize the performance benefits of sandwich structures. Two sizes of corrugated sandwich panels with hot‐melt bonding and resistance welding connection methods were fabricated. The mechanical properties of sandwich panels were compared using a combination of experimental, numerical, and analytical investigation. Edgewise compression (EC) and 3‐point bending (3 PB) tests were conducted to obtain load–displacement curves and investigate different failure modes of sandwich panels. The peak edge compression and bending loads of the resistance welded structures were 42% and 92% higher, respectively, and the face‐core interface was always well‐connected compared to those of the hot‐melt bonding. The results indicate that the resistance welding method can be utilized as a core bonding technique for thermoplastic composite sandwich structures and has great potential for aerospace application.Highlights A method that includes hot‐melt bonding and resistance welding are develop to produce thermoplastic composite corrugated sandwich panels (TPC‐CSPs). The TPC‐CSPs fabricated by resistance welding exhibit superior interface connection performance compared to hot‐melt bonding and this method enhance the structural load bearing capacity. The numerical and analytical method were presented to investigate the failure model, which was consistent with the experimental results.

Establishment and Parameter Calibration of a Simulation Model of Coated Cotton Seeds and Soil

Precision seeding technology is an important component of agricultural mechanization production. The precise regulation of seed movement behavior is the core of precision sowing technology and the key to improving the quality of single seed precision sowing. To accurately obtain the interaction law between seeds and soil after touching the soil, it is necessary to conduct comprehensive physical experiments to determine the simulation parameters of the seed and soil. This article takes coated cotton seeds as the research object, and the basic physical parameters of coated cotton seeds are measured through biological experiments. Based on the Hertz–Mindlin with bonding V2 contact model, a simulation model of compression between coated cotton seeds and soil is established. Using peak compression force as the response value, a combination of physical experiments and simulation simulations was used to calibrate the simulation parameters of the simulation mode of coated cotton seeds and soil. Through PB testing, it was found that four factors have a significant impact on the peak compressive force, and the parameter range was obtained. The Poisson’s ratio of coated cotton seeds was 0.14–0.26. The static friction coefficient between coated cotton seeds and steel plate was 0.38–0.58. The static friction coefficient between soil and soil was 0.3–1.2. The rolling friction coefficient between soil and soil was 0.1–0.6. Through response surface experiments with four factors and three levels, regression models were established between various factors and response values, and the optimal combination of simulation parameters was determined: the Poisson’s ratio of coated cotton seeds was 0.21; the static friction coefficient between coated cotton seed and steel plate was 0.47; the static friction coefficient between soil and soil was 0.34; and the rolling friction coefficient between soil and soil was 0.59. Based on the optimal parameter combination, the simulation of compression between coated cotton seeds and soil was continued, and the variation law of soil particle bonding bonds at different positions of coated cotton seeds during the compression process was obtained. This study provides a basis for exploring the interaction mechanism between the trencher seed soil of precision seeders and optimizing the design of critical components of cotton precision seeders.

Lumbar and neck injuries of occupants in different reclining postures

PurposeWith the increasing level of automation in automobiles, the advent of autonomous vehicles has reduced the tendency of drivers and passengers to focus on the task of driving. The increasing automation in automobiles reduced the drivers' and passengers' focus on driving, which allowed occupants to choose a more relaxed and comfortable sitting position. Meanwhile, the occupant's sitting position went from a frontal, upright position to a more relaxed and reclined one, which resulted in the existing restraint systems cannot to keep occupants safe and secure. This study aimed to determine the effects of different reclining states on occupants' lumbar and neck injuries. MethodsThis is an original research on the field of automotive safety engineering. Occupants in different initial sitting positions (25°, 35°, 45°, and 55°) were adapted to changes in seat back angle and restraint systems and placed in the same frontal impact environment. Neck injury indexes, lumbar axial compression force and acceleration, as well as occupant dynamic response during the impact, were compared in different sitting positions. The injury response and kinematic characteristics of occupants in different reclining positions were analyzed by the control variable method. ResultsAs the sitting angle increased, the occupant's head acceleration decreased, and the forward-lean angle decreased. Occupants in the standard sitting position had the greatest neck injury, with an Nij of 0.95, and were susceptible to abbreviated injury scale 2+ cervical medullary injuries. As the seatback angle increased, the geometric position of the lumbar spine tended to be horizontal, and the impact load transmitted greater forces to the lumbar spine. The occupant's lumbar injury was greatest in the lying position, with a peak axial compression force on the lumbar region of 5.5 KN, which was 2.3 KN greater than in the standard sitting position. ConclusionThe study of occupant lumbar and neck injuries based on different recline states can provide a theoretical basis for optimizing lumbar evaluation indexes, which is conducive to the understanding of the lumbar injury mechanism and the comprehensive consideration of occupant safety protection.

Experimental and CFD investigation on resistance reduction of hydrofoils for amphibious vehicles

ABSTRACT Resistance characteristics of amphibious vehicles are crucial for their sailing speed and battlefield survivability. This study proposes the installation of hydrofoils at the wheel cavity to reduce resistance and enhance performance. Two hydrofoil designs and four shapes are analyzed to determine the optimal drag reduction design. Towing tests and numerical simulations are employed to investigate and evaluate the hydrodynamic performance of amphibious vehicles. The impact of hydrofoils on resistance reduction is analysed and elucidated through a comprehensive analysis of surface pressure distribution, sailing attitude, and energy consumption in the flow field. Results demonstrate that, except for the elongation-hydrofoil, the other three shapes all show significant performance optimisation at medium to high speeds Fr > 0.5 , with improved effectiveness as speed increases. Among the four shapes, the curve-hydrofoil exhibits the best overall drag reduction effect (18%) and resistance peak compression ability (6.68%), owing to its ample lift force and optimal trim capability.

The study on the properties of a metamaterial composed of star-shaped auxetic and curved-beam multi-stable structure

This article presents the design of a new metamaterial with adjustable Poisson’s ratio and multi-stability, which combines two common metamaterial structures: star-shaped auxetic and multi-stability. The range of negative Poisson’s ratio variation for the unit structure is 0.2433. The negative Poisson’s ratio shows an increasing trend followed by a decrease with the increase in compression displacement. The peak compression displacement is 12 mm, and the peak negative Poisson’s ratio is −0.1499. Simultaneously, the structure exhibits good shape memory properties, with a shape memory recovery ratio of R rx = 94.18% in the y-axis direction and R ry = 91.20% in the x-axis direction. The shape memory recovery time is 35.10 s. The combination of experimental testing and finite element analysis was employed to verify the functionality of the adjustable Poisson’s ratio in the structure. Special attention was given to investigating the structural parameters such as the type of curved-beam, the angle of the star-shaped structure, the width of the star-shaped structure, and the connection method for their effects on the shape memory effect and the range, peak value, and peak compression displacement of the negative Poisson’s ratio in the unit structure. Based on the characteristics of the novel metamaterial, including a significant increase in stiffness upon compression and controllable deformation sequence, it can be used as a buffering device in protective engineering and civil engineering applications.

Impact of strong magnetization in cylindrical plasma implosions with applied B-field measured via x-ray emission spectroscopy

Magnetization is a key strategy for enhancing inertial fusion performance, though accurate characterization of magnetized dense plasmas is needed for a better comprehension of the underlying physics. Measured spectra from imploding Ar-doped D2-filled cylinders at the OMEGA laser show distinctive features with and without an imposed magnetic field. A multizone spectroscopic diagnosis leads to quantitative estimates of the plasma conditions, namely revealing a 50% core temperature rise at half mass density when a 30-T seed field is applied. Concurrently, experimental spectra align well with predictions from extended-magnetohydrodynamics simulations, providing strong evidence that the attained core conditions at peak compression are consistent with the impact of a 10-kT compressed field. These results pave the way for the validation of magnetized transport models in dense plasmas and for future magnetized laser implosion experiments at a larger scale. Published by the American Physical Society 2024

Mechanical properties of homogeneous and functionally graded spinodal structures

This paper investigates the compressive mechanical behavior of spinodoid metamaterials in a quasi-static state through experimental and numerical analysis at the macroscopic level. This homogeneous structure exhibits weak strain hardening, resulting in a lower initial peak compression force and higher specific absorption energy compared to other mechanical metamaterials. The homogeneous model has multiple low-density regions uniformly distributed within the three-dimensional space due to the random nature of the Gaussian field. Thus, the transition from low-density to high-density regions is described as a gradual process, implying that the deformation of metamaterial shifts to region-by-region compaction. Besides, the functionally graded spinodoid structure shows strong strain hardening, whose deformation mainly tends to collapse layer by layer along a positive graded direction. The graded structures with low densities have a lower energy absorption capacity than the corresponding homogeneous structure, while higher-density structures show a reverse trend. This phenomenon originates from the superimposed effect of two kinds of strain hardening.

Diagnosis of indirectly driven double shell targets with point-projection hard x-ray radiography

We present an application of short-pulse laser-generated hard x rays for the diagnosis of indirectly driven double shell targets. Cone-inserted double shell targets were imploded through an indirect drive approach on the upgraded SG-II laser facility. Then, based on the point-projection hard x-ray radiography technique, time-resolved radiography of the double shell targets, including that of their near-peak compression, were obtained. The backlighter source was created by the interactions of a high-intensity short pulsed laser with a metal microwire target. Images of the target near peak compression were obtained with an Au microwire. In addition, radiation hydrodynamic simulations were performed, and the target evolution obtained agrees well with the experimental results. Using the radiographic images, areal densities of the targets were evaluated.

Biomechanical comparison of headless compression screws versus independent locking screw for intra-articular fractures

PurposeHeadless compression screws (HCS) have a variable thread pitch and headless design enabling them to embed below the articular surface and generate compression force for fracture healing without restricting movement. Locking screws have greater variety of dimensions and a threaded pitch mirroring the design of the HCS. The objective of this study is to determine whether locking screws can generate compression force and compare the compressive forces generated by HCS versus locking screws.MethodA comparison between 3.5-mm HCS versus 3.5-mm locking screws and 2.8-mm HCS versus 2.7-mm locking screws was performed using a synthetic foam bone model (Synbone) and FlexiForce sensors to record the compression forces (N). The mean peak compression force was calculated from a sample of 3 screws for each screw type. Statistical analysis was performed using the one-way ANOVA test and statistical significance was determined to be p = < 0.05.ResultsThe 3.5-mm Synthes and Smith and Nephew locking screws generated similar peak compression forces to the 3.5-mm Acutrak 2 headless compression screws with no statistically significant difference between them. The smaller 2.7-mm Synthes and Smith and Nephew locking screws initially generated similar compressive forces up to 1.5 and 2 revolutions, respectively, but their peak compression force was less compared to the 2.8-mm Micro Acutrak 2 HCS.ConclusionLocking screws are able to generate compressive forces and may be a viable alternative to headless compressive screws supporting their use for intra-articular fractures.

Diagnosing the origin and impact of low-mode asymmetries in ignition experiments at the National Ignition Facility.

Inertial confinement fusion ignition requires high inflight shell velocity, good energy coupling between the hotspot and shell, and high areal density at peak compression. Three-dimensional asymmetries caused by imperfections in the drive symmetry or target can grow and damage the coupling and confinement. Recent high-yield experiments have shown that low-mode asymmetries are a key degradation mechanism and contribute to variability. We show the experimental signatures and impacts of asymmetry change with increasing implosion yield given the same initial cause. This letter has implications for improving robustness to a key degradation in ignition experiments.

Abstract 189: How Quickly Does Arterial Blood Pressure Recover After Pauses in Mechanical Chest Compressions in Humans With Out-of-Hospital Cardiac Arrest?

Introduction: Conventional wisdom says that arterial blood pressure (ABP) recovers slowly after interrupting CPR chest compressions (CCs). An oft-cited animal study with manual compressions and 15:2 compression:ventilation ratio showed that all 15 compressions were needed to restore pre-pause invasive pressure, implying that even short pauses substantially reduce CPR blood flow. Whether this holds true for humans receiving mechanical chest compressions is unknown. We measured recovery of ABP after pauses in mechanical compressions by LUCAS in patients treated for out-of-hospital cardiac arrest (OHCA). Methods: We analyzed data from a subset of patients enrolled in both groups of a prospective, randomized LUCAS 2 Active Decompression trial performed by an anesthesiologist-staffed rapid response car program in Oslo, Norway from 2016 to 2018. Only patients with an ABP signal and at least one CC pause longer than 2 sec were included. All CCs were mechanical. Arterial cannulation was verified, and CC pauses were identified by physician review of the patient care record and physiological signals. Pauses were excluded if ROSC or a LUCAS “soft start” occurred or epinephrine had been applied within 5 minutes of the pause. Peak compression (cAP), mean (mAP), and mean decompression arterial blood pressures (dAP) for 10 CCs before and after each pause were measured with custom MATLAB code. Results: We included 56 patients with a total of 148 pauses (mean pause duration: 10.63 ± 3.05 sec). Pre-pause mean cAP, mAP, and dAP were 95.6 ± 0.3, 49.9 ± 0.1 and 30.5 ± 0.1 mmHg. Post-pause dAP for each compression was not significantly different than pre-pause dAP (Fig. 1A,B). cAP and mAP recovered to &gt;90% of pre-pause pressure within 2 CCs. Pause duration was not predictive of post-pause pressures (Fig. 1C). Conclusions: ABP generated by mechanical CPR recovered quickly after pauses. Consequently, short pauses (such as pauses for 30:2 CPR) may pose less hemodynamic concern than previously thought.

Energy absorption characteristics of aluminum foam-filled corrugated tube under axial compression loading

To improve the energy absorption characteristics of thin-walled structures and reduce the initial peak compression force and load fluctuation, a novel aluminum foam-filled corrugated tube was proposed in this study. Finite element model validated by quasi-static compression experiments was adopted to investigate the crashworthiness performances of aluminum foam-filled corrugated tubes and their combined energy-absorbing structures. The effects of structure parameters including corrugation radius, wall thickness, corrugation length and corrugation radius increments on axial compression characteristics were investigated through finite element analysis. The results showed that compared with aluminum foam-filled straight tubes, the initial peak compression force of aluminum foam filled corrugated tube was reduced by 22.87 %, the compression force efficiency was increased by 6.69 % and the load fluctuation was reduced by 17.94 %. The smaller the values of corrugation radius, wall thickness and corrugation length, the smaller the initial peak compression force; Because the corrugation radius had a great effect on the peak compression force, the order that the corrugations were compressed into folds can be controlled by designing the corrugation radius; In view of the peak and valley values of compression force, an innovative combination of single tubes with different △H was obtained, which had better energy absorption performance. Compared with a single aluminum foam-filled corrugated tube, the compression force efficiency of the combined structure (△H: 0–5–10) was increased by 18.15 % and the load fluctuation was reduced by 33.60 %. The research results can provide a reference for the design and optimization of energy-absorbing devices.