Effects Of Cyclic Compression Research Articles

Effect of cyclic compression on the micromechanical properties of a Zr-based metallic glass

In this study, the effect of cyclic compression on the micromechanical properties of a Zr-based metallic glass (MG) was investigated via nanoindentation. Cyclic compression significantly softened the surface of the sample, with a maximum hardness loss of 19.93%. The number of cyclic compression passes had a greater effect on the hardness of the sample than the cyclic compression load. The elastic modulus exhibited a nonlinear variation upon increasing the cyclic loading or number of passes at a lower loading rate due to the coupling effect of loading rate and cyclic compression treatment. Then, the serration behavior and strain rate sensitivity analysis were applied. The calculated m-values obtained for MGs were all negative and gradually tended to zero upon further cyclic compression treatment. This demonstrated the weakening effect of cyclic compression on the strain rate sensitivity of MG, and the underlying mechanism was discussed. This study provides a process reference for studying the fatigue failure behaviors of MGs from the perspective of mechanical properties, which is useful for understanding their fatigue generation.

Effects of cyclic compression on intervertebral disc metabolism using a whole-organ rat tail model.

Many factors contribute to the development and progression of intervertebral disc (IVD) degeneration. This study was designed to assess the effects of compressive load magnitude on IVD metabolism. It was hypothesized that as load magnitude increased, there would be a significant increase in release of proinflammatory and degradative biomarkers, and a significant decrease in tissue proteoglycan (GAG) and collagen contents compared with unloaded controls. IVD whole organ functional spinal units (FSU) consisting of cranial and caudal body halves, cartilage endplates, and IVD (n = 36) were harvested from the tails of six Sprague Dawley rats, and FSUs were cultured at 0.0 MPa, 0.5 MPa, or 1.0 MPa at 0.5 Hz for 3 days. After culture, media were collected for biomarker analysis and FSUs were analyzed for extracellular matrix composition. Significant differences were determined using a one-way analysis of variance or Kruskal-Wallis test and post hoc analyses. Media concentrations of IFN-γ, IL-6, IL-1β, and MMP-8 were significantly higher in the 0.5 MPa compared with the 0.0 MPa group. Media concentrations of PGE2 and TIMP-1 were significantly higher in the 1.0 MPa group compared with the 0.0 MPa group, and media PGE2 was significantly higher in the 1.0 MPa group compared with the 0.5 MPa group. Media GAG content was significantly higher in the 1.0 MPa group compared with the 0.0 MPa group, and percent GAG in the tissue was significantly lower in 0.5 MPa and 1.0 MPa groups compared with the 0.0 MPa group. Clinical Significance: These data suggest that there are magnitude-dependent inflammatory and degradative IVD responses to cyclic loading, which may contribute to IVD degeneration.

Effect of cyclic compression on bone marrow mesenchymal stromal cells in tissue engineered cartilage scaffold.

In this current study, a novel multilayer porous composite scaffold was fabricated with chitosan (CS), silk fibrin (SF) and nano-hydroxyapatite (n-HA). Scanning electron microscope was utilized to detect the characteristics of the composed scaffold. Rat bone marrow stromal cells (rBMSC) were loaded onto the CS/SF/n-HA scaffold and cultured in a bioreactor under an on-off dynamic compression (10% compressive strain, 0.5 Hz, [2 h action + 4 h pause]/cycle, 4 cycles/day). Metabolism of the loaded rBMSC was assessed through CCK-8 test. Qualitative polymerase chain reaction and western blot were applied to assess the chondrogenic differentiation of the seeded cells. Compressive modulus of the cell/scaffold constructs was analyzed. Additionally, a pig model was employed to evaluate the effect of the tissue-engineered cartilage on repairing of cartilage defect. Results showed that the four layers within the scaffold were tightly connected without gaps between porous interfaces of the layers. Scaffold porosity was 92.20% ± 1.30%. The cyclic compression upregulated chondrogenesis markers (Aggrecan, Sox-9, and collagen II). Increased compressive modulus of the cell/scaffold complex was detected after dynamic compression. The pig bone marrow stromal cells/scaffold complex exposed to cyclic compression presented most favorable reparative effect on the mini pig femoral condyle cartilage defects. Our study suggested that the on-off dynamic compression might be a promising approach to fabricate tissue-engineered cartilage in vitro. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 1294-1302, 2019.

Effects of cyclic compression on the mechanical properties and calcification process of immature chick bone tissue in culture

Contribution of mechanical loading to tissue growth during both the development and post-natal maturation is of a particular interest, as its understanding would be important to strategies in bone tissue engineering and regenerative medicine. The present study has been performed to investigate how immature bone responds to mechanical loading using an ex vivo culture system. A slice of the tibia, with the thickness of 3mm, was obtained from 0-day-old chick. For the ex vivo culture experiment in conjunction with cyclic compressive loading, we developed a custom-made, bioreactor system where both the load and the deformation applied to the specimen was recorded. Cyclic compression, with an amplitude of 0.3N corresponding to 1 to 2% compressive strain, was applied to immature bone specimen during a 3-day culture period at an overall loading rate 3–4cycles/min, in the presence of β-glycerol phosphate and dexamethasone in culture medium. The stress-strain relationship was obtained at the beginning and the end of the culture experiment. In addition, analyses for alkaline phosphate release, cell viability and tissue calcification were also performed. It was exhibited that elastic moduli of bone slices were significantly elevated at the end of the 3-day culture in the presence of cyclic compression, which was a similar phenomenon to significant elevation of the elastic moduli of bone tissue by the maturation from 0-day old to 3-day old. By contrast, no significant changes in the moduli were observed in the absence of cyclic compression or in deactivated, cell-free samples. The increases in the moduli were coincided with the increase in calcified area in the bone samples. It was confirmed that immature bone can respond to compressive loading in vitro and demonstrate the growth of bone matrix, similar to natural, in vivo maturation. The elevation of the elastic moduli was attributable to the increased calcified area and the realignment of collagen fibers parallel to the loading direction. The ex vivo loading system established here can be further applied to study responses to mechanical loading in osteogenesis as well as callus maturation for better understanding of factors to consider in successful bone regeneration with mechanical factors.

Effect of cyclic compression and curing agent concentration on the stabilization of mechanical properties of PDMS elastomer

Under repeated deformation, the mechanical properties of polydimethylsiloxane (PDMS) elastomer evolve. This paper aims to investigate the effect of curing agent concentration on the mechanical response of PDMS elastomer under cyclic compressive loading. PDMS elastomer samples containing various curing agent concentrations were prepared following ASTM D575 standard. Three different curing agent concentrations were investigated: 6.25, 9.09 and 16.67wt%. Monotonic compressive test up to failure and 100cycles of cyclic compressive test were performed using Instron 3369 50kN dual column testing machine at a constant crosshead displacement rate of 12mm/min. It was found that the compressive modulus increases with the curing agent concentration. The effects of cyclic compression on strain hardening, compressive modulus, and creep were also investigated. Results showed that cyclic compression contributes to the stabilization of the materials. Moreover, the number of cycles required to reach strain hardening stabilization decreases as the curing agent concentration increases.

2F12 周期的な圧縮・電界複合刺激が軟骨組織再生に及ぼす影響(OS15-1:骨・軟骨再生のための組織工学的アプローチ(1))

2F12 周期的な圧縮・電界複合刺激が軟骨組織再生に及ぼす影響(OS15-1:骨・軟骨再生のための組織工学的アプローチ(1))

Effect of cyclic compression on structure and properties of a Gas Diffusion Layer used in PEM fuel cells

Proton Exchange Membrane Fuel Cell (PEMFC) components are known to deteriorate during use, in time scales much shorter than that required for commercially successful deployment of this technology. Therefore, servicing operations such as identifying and replacing poorly performing components will likely be required to extend the operational lifetime of PEMFC stacks. During such servicing operations fuel cell components are subjected to cyclic compression and expansion due to opening and rebuilding of the fuel cell stack. This cyclic compression may further contribute to the deterioration of PEMFC components. There are several reports in the literature showing the effect of static compression on change in GDL properties, however the present work focuses on the effect of cyclic compression on GDL properties, an aspect that has not been reported in detail elsewhere. This paper focuses on the impact of cyclic compression on the Gas Diffusion Layer (GDL). The results indicate that cyclic compression causes significant and irreversible changes to the structure and properties of the GDL such as surface morphology, surface roughness, pore size, void fraction, thickness, electrical resistance, contact angle, water uptake and in-plane permeability. The implications of these results are considered.

Effects of cyclic compression and thermal aging on dynamic properties of neoprene rubber bearings

AbstractThe dynamic properties of rubber bearings frequently used as isolators in structures could be significantly deteriorated because of the change of microstructure in rubber caused by cyclic compression and thermal aging. As a result, a catastrophic failure of bridges and buildings unexpectedly occurs when they are subjected to earthquake attack. Here, the dynamic properties of neoprene rubber bearings before and after different cycles of compressive loading or various periods of thermal aging were first measured and compared to each other. On the basis of the experimental results, the effects of cyclic compression and thermal aging on the stiffness, energy absorption, and equivalent viscous damping coefficient of neoprene rubber bearings are investigated. It is found that the deterioration of dynamic properties of neoprene rubber bearings caused by either cyclic compression or by thermal aging is significant and should be taken into account in designing rubber bearings. © 2007 Wiley Periodicals, Inc. JAppl Polym Sci, 2008

Effects of cyclic compression on epithelial transport and viral infection in an engineered airway wall model

Effects of cyclic compression on epithelial transport and viral infection in an engineered airway wall model

Effects of cyclic compression on ECM synthesis and mechanical property in cultured chondrocyte-agarose construct

In numerous cell types, the cytoskeleton has been widely implicated in mechanotransduction pathways involving stretch-activated ion channels, integrins and deformation of intracellular organelles. Studies have also demonstrated that the cytoskeleton can undergo remodelling in response to mechanical stimuli such as tensile strain or fluid flow. In articular chondrocytes, the mechanotransduction pathways are complex, inter-related and as yet, poorly understood. Furthermore, little is known of how the chondrocyte cytoskeleton responds to physiological mechanical loading. This study utilises the well-characterised chondrocyte-agarose model and an established confocal image-analysis technique to demonstrate that both static and cyclic, compressive strain and hydrostatic pressure all induce remodelling of actin microfilaments. This remodelling was characterised by a change from a uniform to a more punctate distribution of cortical actin around the cell periphery. For some loading regimes, this remodelling was reversed over a subsequent 1 h unloaded period. This reversible remodelling of actin cytoskeleton may therefore represent a mechanism through which the chondrocyte alters its mechanical properties and mechanosensitivity in response to physiological mechanical loading.

The effect of cyclic compression on the mechanical properties of the inter-vertebral disc: An in vivo study in a rat tail model

Objective. To assess the changes in the mechanical properties of inter-vertebral discs in vivo following static and cyclic compressive loading of different frequencies. Design. An in vivo biomechanical study using a rat-tail model of the inter-vertebral disc. Background. Mechanical loading has been suggested as playing a major role in the etiology of disc degeneration, but the relationship is still not fully understood. Methods. Sixty Sprague–Dawley rats were subject to daily compressive stress via pins inserted in the 6th and 7th caudal vertebrae over a two-week loading period. Animals were randomly divided into a sham group (pin insertion, no loading), a static loading group, or cyclic loading groups of 0.5, 1.5, or 2.5 Hz. Loading was applied for 1 h each day from the 3rd to 17th day following pin insertion, and the angular compliance, angular laxity, and inter-pin distance were measured in vivo at days 0, 3, 10 and 17. Results. Changes in the inter-vertebral disc height depended on the frequency of loading, with the decrease in disc height in the static compression group significantly greater than that in all other groups, whereas the decrease in the 1.5 Hz cyclic compression group was significantly smaller than that in all other compression groups. Conclusions. Changes in disc properties depend on both the total load exposure and the frequency of loading. Cyclic loading in general produced less marked changes than static loading, but loading at particular frequencies may result in more severe changes. Relevance Previous studies have shown the in vivo changes in the mechanical properties of inter-vertebral discs to depend on the magnitude and duration of loading. In this study, a frequency dependent response to cyclic loading is also demonstrated.

Parameters Influencing Performance of Elastomeric Bearings at Low Temperatures

Experimental research was conducted to study the performance of elastomeric bridge bearings at low temperatures. Full-size natural rubber and neoprene bearings were tested by specially designed test setups inside a walk-in type environmental chamber. Steel laminated bearings were ordered with 2 specified shear modulus, 0.69 and 1.08 MPa. Tests were conducted at 23, -10, -20, and -30 deg C for a period of 21 days. The effects of cyclic compression, cyclic shear, rate of loading, type of elastomer compound, temperature history, creep, and slip coefficient on the performance were investigated. Approximately 500 shear stiffness tests were performed. Results indicate that the increase in shear stiffness at low temperature is a function of elastomer compound, temperature, and time. Rate of loading, amplitude of strain, coefficient of friction, and temperature history were identified as key parameters influencing bearing performance. Creep at low temperature was markedly different from that at room temperature, but had no major influence on overall performance. It was shown that cyclic compression force and shear strain do not have major influence on time-dependent stiffening of bearings.

Response of peripheral nerve to cyclic compression in a laboratory rat model.

Repetitive cyclic loading of a nerve has been proposed as a pathogenic factor in the development of occupational compression neuropathies. Little is known about the basic response of peripheral nerve to cyclic compression. We investigated the hypothesis that cyclic compression is more detrimental to nerve function than constant compression. We measured the amplitudes and velocities of distally evoked action potentials in the presence of constant or cyclic compression of the tibial nerve in rats. Seven groups were subjected to constant or cyclic compression for 6 h by a computer controlled, hydraulically activated compression chamber. Nerves were compressed with 0 (control group), 30, 60, or 90 mm Hg of constant pressure or 0-30, 20-50, or 30-60 mm Hg of cyclic compression for approximately 20,000 compression cycles. Action potentials were recorded every 15 min. The effects of cyclic compression on nerve conduction were equivalent to the effects of constant compression at the average applied pressure. Cyclic loading itself does not appear to be an important pathogenic factor in the development of nerve conduction block.