MPa In Compression Research Articles

Establishing a through-puncture model for assessing post-injection leakage in the intervertebral disc.

Needle injection through the outer annulus fibrosus of the intervertebral disc (IVD) is the most practical approach for delivery of therapeutic agents, which have been shown to potentially leak following needle retraction. The goal of this work was to establish a protocol for quantifying post-injection leakage and test its sensitivity to factors believed to affect needle track geometry. A through-puncture defect procedure, followed by controlled injection, was performed on bovine caudal IVDs. Sensitivity to needle size was tested by injection of saline into unconstrained discs with either a 30G, 26G, or 21G hypodermic needle. Sensitivity to axial load was tested by repeated injection via a 26G needle with either no constraint, fixed height, or 10% axial compressive strain. Sensitivity to flexion was tested by applying combined 0.2MPa compression and 15° of flexion following injection of 5% of disc volume. Needle diameter significantly affected maximum volume prior to leakage, ranging from 34.6 ± 31.9µL when using 21G to 115.6 ± 23.6µL when using 30G. While all unloaded discs leaked, axial compression decreased the incidence of leakage events by 50-100% depending on load history. Forward flexion resulted in a 22% incidence of leakage. Fluid injected into IVDs is at significant risk of leakage following needle retraction. This risk depends on factors which alter the geometry of the needle track, including needle size, pinching due to axial compression, and stretching as a result of forward flexion.

The Effect of Heavy-Duty Vehicle Crossings on the State of Stress of Buried Pipelines

The aim of this article is to quantify the loads exerted by heavy-duty vehicles when crossing over buried pipeline. This problem arises in connection to the question pertaining to the use of protective sleeves (casings) applied to gas pipelines in regions with increased demands on pipeline operation safety. An experiment was conducted on a test pipe section made from L360NE pipeline steel equipped with strain gauges along the pipe perimeter, measuring strains in the axial and circumferential directions. Strain measurements were taken after back-filling the pipe trench, then during vehicle crossings over the empty pipe, and again after pressurizing the test pipe with air. Strain-based hoop stresses at the surface of the empty test pipe were found to exceed 30 MPa after back-filling the trench and increased to more than 40 MPa during the vehicle crossings. Similarly, axial stresses reached extremes of around 17 MPa in compression and 12 MPa in tension. Applying internal air pressure to the test pipe resulted in a reduced net effect on both the hoop and axial stresses.

A Review of Basic Mechanical Behavior of Laminated Bamboo Lumber

Over the past decade, the physical and mechanical performances of laminated bamboo lumber (LBL)–a bamboo-based structural material, have been extensively studied using experimental, analytical, and numerical approaches. This paper presents a review of existing knowledge in the literature about the mechanical properties of LBL. The paper involved the review of the response of LBL to different types of loading such as tension, bending, compression, and shear. Based on results of the literature reviewed, the strength of LBL parallel to grain was 90–124 MPa with MOE of 10700 MPa in tension, 29.55–72.60 MPa, and MOE of 8396–11022 MPa in compression, 63.87–128.4 MPa, and MOE of 8320–10912 MPa in bending, and 7.15–17.5 MPa in shear. The average strength of LBL was similar and in some cases exceeded the average values of bamboo- or wood-based materials, while the variability of its mechanical parameters was lower. The variability in strength values of LBL was affected by bamboo species, density and thickness of bamboo strips, growth portion, type of treatment, strips arrangements, and type of adhesive which in turn calls for classification of LBL by strength grades, degree of hardness, the capability of impregnation and penetration, as well as by areas of application in construction. The study provided and discussed concluding observations, the current research gap, and future research directions on the mechanical properties of LBL.

Physical and Mechanical Characteristics of Ash Concrete from Palm Nut Shells: Pouzzolanic Effect

The use of agricultural waste in construction is an advantage favorable to environmental sanitation, the preservation of non-renewable resources but also to the execution of an ecological work. The objective of this work is to study the influence of the addition of palm nut cockles ash as an adjuvant on the physico-mechanical properties of concrete. For this study, ordinary concretes and ash concretes were made and subjected to physical and mechanical characterization tests at different maturation periods. The results of the tests carried out indicate that the presence of ash reduces the workability and porosity of the concrete and then increases the density of the concrete to 6.3%. In addition, we found that incorporating the ash improves the mechanical strength of the concrete compared to the control concrete. Thus, the compressive strength of ash concrete is 32.07 MPa and that of splitting is 2.76 MPa at 28 days, which is satisfactory vis-à-vis the threshold of construction projects for ready concrete for use, which recommends a minimum of 25 MPa (compression) and 2.6 MPa (splitting) at 28 days. This improvement in mechanical performance can be attributed to the pozzolanic effect of the constituents of the ash. Therefore, the ash from palm nut shells can be used to improve the mechanical properties of concrete.

Strength and Microstructure Characteristics of Blended Fly Ash and Ground Granulated Blast Furnace Slag Geopolymer Mortars with Na and K Silicate Solution.

Mineral geopolymer binders can be an attractive and more sustainable alternative to traditional Portland cement materials for special applications. In geopolymer technology the precursor is a source of silicon and aluminium oxides, the second component is an alkaline solution. In the synthesis of geopolymer binders the most commonly used alkaline solution is a mixture of sodium or potassium water glass with sodium or potassium hydroxide or silicate solution with a low molar ratio, which is more convenient and much safer in use. In this paper, we present the influence of sodium or potassium silicate solution on the physical and mechanical properties of fly ash and ground granulated blast furnace slag-based geopolymer mortars. Mercury intrusion porosimetry and microstructural observation allowed for comparing the structure of materials with a different type of alkaline solution. The evolution of compressive and flexural tensile strength with time determined for composites using 10%, 30% and 50% slag contents (referring to fly ash mass) was analysed. The tests were performed after 3, 7, 14 and 28 days. It was observed that, as the amount of slag used increases in the precursor, the strength of the material grows. Mortars with the sodium alkaline solution were characterised by a higher strength at a young age. However, the values of strength 28 days were higher for geopolymers with potassium alkaline solution reaching 75 MPa in compression. Geopolymer mortar microstructure observation indicates a high matrix heterogeneity with numerous microcracks. Matrix defects may be caused by the rapid kinetics of the material binding reaction or shrinkage associated with the drying of the material.

Composites Based on Iroko Wood Flour Stabilized Using High Density Polyethylene Resin Recovered: 1. Mechanical Properties

Nowadays, waste management has become one of the major priorities for the protection of ecosystems. Among these wastes, those of plastic origin require particular importance. As an alternative solution to this problem, this waste is reused for other purposes such as the development of new materials. The work presented proposes, on the one hand, to develop a composite based on Iroko wood flour stabilized by high density polyethylene resin (Hdpe) and, on the other hand, to measure its mechanical characteristics. To do this, resin mass contents varying from 10 to 60% were mixed with the flour to obtain composites according to a well-defined method. The variation of these mechanical properties has been studied as a function of the proportions of the binder. The measurements carried out related to the behavior in compression, in flexion and in traction. It appears that the mechanical strengths increase for high levels of binder. In addition, for each resin content, the composite has an increasingly resistant behavior in compression than in traction and in flexion. For example, for 60% of Hdpe, the strengths are equal to 23.95 MPa in compression, 18.22 MPa in tension and 13,17 MPa in flexion. However, from 50%, the material adopts an increasingly stable behavior. In addition, it becomes more ductile and deformable as the binder content increases. The use of the proposed method is an alternative for the management of the waste.

Effects of hollow glass microspheres on the polybenzoxazine thermosets: Mechanical, thermal, heat insulation, and morphological properties

AbstractThe growing need for high thermal and mechanical resistant lightweight syntactic foams demands the designing of new materials. Herein, we report the successful fabrication of lightweight and high thermal resistance syntactic foams with excellent thermal and good mechanical properties. For this end, 10–50 wt% hollow glass microsphere (HGMS) containing polybenzoxazine based syntactic foams were prepared by using bisphenol‐A‐aniline (BA‐a) and phenol‐diaminodiphenylmethane (P‐ddm) benzoxazine via curing at 10 MPa compression molding. The curing behavior, tensile, flexural, compressive, and impact strength, thermal properties, and fracture morphology of the syntactic foams were studied by DSC, universal material testing machine, and drop hammer impact testing machine, TGA, and SEM, respectively. The curing temperatures of BA‐a and P‐ddm benzoxazine resins were slightly increased after blending the HGMS. The highest decline (59%) in the density and highest void contains (13.17%) was recorded for the poly(P‐ddm/HGMS50) sample. The excellent specific mechanical properties of the syntactic foams were observed on the 30 wt% HGMS loading. The thermal conductivity of the foams was gradually decreased and the lowest values of 0.106 and 0.0985 W/m.K were observed for poly(BA‐a/HMGS50) and poly(P‐ddm/HGMS50) sample, respectively. Furthermore, a gradual improvement in the thermal properties was observed as the loading of HGMS increased.

Optimization of CO2 Adsorption and Physical Properties for Pelletization of Zeolite 5A

This research investigated the effects of compression force, compression time, and addition of bentonite binder on zeolite 5A pelletization. Carbon dioxide (CO2) adsorption of zeolite 5A pellets was tested in a laboratory-scale packed-bed reactor at 298 K, atmospheric pressure and 2 l/h flow rate. Zeolite 5A pellets were prepared using a pelletization technique at 200-400 MPa compressive force, 5-15 min compression time, and with 0-15% wt. of bentonite binder. The specific surface area and density of zeolite 5A pellets increased with increase of compression force. Compression force led to increase in specific surface area and resulted in an agglomeration of zeolite pellets, making CO2 molecules more difficult to become active sorbent. The addition of bentonite into zeolite 5A pellets with more compression time resulted in the reduction of specific surface area. The compression force and mass fraction of the binder were found to offer significant control over CO2 adsorption capacity. No addition of binder, 200 MPa compression force and 5 min compression time resulted in a maximum CO2 adsorption capacity of 3.64 mmol CO2/g. This research indicated that zeolite 5A pellets have a beneficial effect and high potential as an adsorbent, especially in terms of CO2 adsorption and environmental applications

Tension-compression asymmetry of stress-relaxation ageing behavior of AA2219 alloy over a wide range of stress levels

The asymmetric stress-relaxation ageing behavior of AA2219 alloy has been experimentally investigated under both tension and compression loading conditions, over a wide range of stress levels at 165 °C for 11 h, using the stress-relaxation ageing tests, room-temperature tensile tests and transmission electron microscopy observations. The relaxed stresses in tension are much larger than those in compression and this deviation mostly originates from the initial rapid reduction stage of stress relaxation. With increasing initial stress, the yield strength in tension increases monotonously, while it remains basically unchanged with only a slight fluctuation of 8 MPa in compression. The mechanisms for asymmetric deformation and strengthening are unveiled on the basis of microstructural analysis. At low initial stress region, the yield strength under compression is higher as compared with that under tension, due to the GP zones and θ'' phases with larger size and weaker stress orientation effect, leading to more stronger hindering effects on the dislocation movement. At high initial stress region, massive dislocations caused by loading and main strengthening θ′ promoted by dislocations result in the larger yield strength under tension, exhibiting an unique reversed strength asymmetry in contrast to low stress level; meanwhile, these dislocations considerably accelerate the tensile stress relaxation process. In addition, the effect of tensile and compressive stresses on precipitate variants is quantitatively discussed based on the Eshelby inclusion theory. These findings benefit the deep understanding of tension-compression asymmetry and offer the theoretical basis for stress-relaxation ageing prediction models.

Combustion synthesis of NbC/ZrO2 composites: Influence of Cr additives on the microstructure and mechanical properties

AbstractComposites of NbC/ZrO2 reinforced with different weight ratios of Cr metal were prepared by dynamic compaction combustion from a blend of Nb2O5–Zr–Cr powders. Factors controlling the synthesis process, the microstructure, and the mechanical properties of the samples, such as Cr wt% and the compression loads were studied. The samples were characterized by XRD, SEM, porosity, and hardness measurements. The porosity value of the sample with no additives was high and reached 31.6 vol%. A sudden decrease in the sample porosity to 2.4 vol % was noticed for the sample containing 3.0 wt% of Cr. A high‐density sample with less than 2.0 vol % porosity and maximum hardness of 1038 HV was produced using 5.0 wt% Cr under 300 MPa compression load. Detailed thermodynamic calculations for the effect of Cr additives on the physicochemical properties of the system were introduced.

Effects of Isochoric Freezing Conditions on Cut Potato Quality.

Isochoric freezing is a pressure freezing technique that could be used to retain the beneficial effects of food storage at temperatures below their freezing point without ice damage. In this study, potato cylinders were frozen in an isochoric system and examined using full factorial combinations of three processing procedures (immersed in water, vacuum-packed and immersed in ascorbic acid solution), four freezing temperatures/pressures (−3 °C/37 MPa, −6 °C/71 MPa, −9 °C/101 MPa and −15 °C/156 MPa) and two average compression rates (less than 0.02 and more than 0.16 MPa/s). The effects of process variables on critical quality attributes of frozen potatoes after thawing were investigated, including mass change, volume change, water holding capacity, color and texture. Processing procedure and freezing temperature/pressure were found to be highly significant factors, whereas the significance of the compression rate was lower. For the processing procedures, immersion in an isotonic solution of 5% ascorbic acid best preserved quality attributes. At the highest pressure level of 156 MPa and low compression rate of 0.02 MPa/s, potato samples immersed in ascorbic acid retained their color, 98.5% mass and 84% elasticity modulus value. These samples also showed a 1% increase in volume and 13% increase in maximum stress due to pressure-induced hardening.

Making strong Al(Mg)-Al3Mg2 composites

Size control of β-Al3Mg2 precipitates, formation of clean Al(Mg)/Al3Mg2 interfaces and refinement of matrix microstructures are key structural factors in the development of strong Al(Mg)-Al3Mg2 composites. Here, we combine severe plastic deformation with rapid thermomechanical powder consolidation to attain a desirable synergy of these structural factors to achieve a high strength. The study demonstrates that the fabricated composite containing 1.2vol.%Al3Mg2 precipitates shows a high yield strength of ~700 MPa in tension and ~850 MPa in compression, opening up a new pathway for developing lighter Al-Mg alloy based composites with higher strength.

Electro-mechanical behaviour of ferroelectrics: Insights into local contributions from macroscopic measurements

The behaviour of a bulk lead zirconate titanate ceramic has been characterised under combined high stress and high electric field. The electrical response of the sample was monitored, and Digital Image Correlation (DIC) was used to characterise the strain field at the surface of the sample. The DIC technique allows both longitudinal and transverse strains to be measured simultaneously. The results showed that a compressive stress of 25 MPa increases the susceptibility by 128% and the longitudinal piezoelectric coefficient by 47%. A further increase of stress has reversed this trend and under a 500 MPa compression, the susceptibility has fallen by 71% and the longitudinal piezoelectric coefficient by 98% compared to the unstressed case. The analysis of the ferroelastic contribution revealed that this decrease is explained by a saturation of the ferroelastic switching, beginning at the coercive field. The material volume change during loading was computed using the DIC results. It was found that a negligible piezoelectric activity remains at 500 MPa while ferroelastic switching still occurs and is reversible. This work shows that it is possible to obtain quantitative insights into the physical mechanisms underlying the macroscopic behaviour of ferroelectrics using the DIC technique without requiring the use of local investigation technique.

The role of quenched-in disorder in polycrystalline bulk and melt-spun ribbons of Ni50Mn29Ga21

ABSTRACT Investigations on the properties of polycrystalline bulk and melt-spun ribbons of composition Ni50Mn29Ga21 are contrasted. Both samples are subjected to quenching after melting and then were homogenized at the same temperature. Though the electron per atom ratio is unchanged, the quenched-in disorder has caused the structural and magnetic transformations to occur in close proximity in the ribbon giving rise to magnetic entropy change of –9.2 J/kg-K at the martensitic transformation. The bulk alloy showed significantly high magnetic field-induced strain of 0.7% at 5 kOe magnetic field and an apparent compressive strain of 5.3% at 40 MPa compression stress, without training the sample. Large grain size and micro-twinning are observed in the bulk, while nano-scale twinning is seen in the ribbon. The variations in the process altered the degree of ordering, which modified the transformation temperatures, the crystal structure, the microstructures of the ribbon and the mechanical properties of the bulk specimen significantly.

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Nanostructured Polymer Composite Electrolytes with Self-Assembled Polyoxometalate Networks for Proton Conduction

Achieving Yield Symmetry in an Extruded Mg-Zn-Y Alloy by More Effective Dispersion of Quasicrystalline i-Phase

A better dispersion of quasicrystalline icosahedral i-phase is achieved in a Mg-3 at. pct Zn-0.5 at. pct Y (ZW82) alloy by a process involving two direct extrusions here. It is confirmed by particle size and distribution analysis that the finer distribution of the particles results from breakage and refinement of the larger particles within the matrix. Better particle distribution resulted in full recrystallization, reported in this alloy composition for the first time. Consequently, a tension-compression yield symmetry was achieved even with a relatively large grain size of about 5 μm. A weaker basal texture (maximum intensity 5.283) played an important role in the strengthening. Yield strengths of about 259 MPa in tension and 269 MPa in compression, with large tensile elongation of 28 pct and compressive elongation of about 20 pct, were obtained. Thus, full recrystallization assisted by finer dispersion of icosahedral phase strengthens the alloy against twinning to remove yield asymmetry, even in a relatively larger grain size alloy.

Development of Multi-Filament Textured-Powder Bi-2212/Ag Wire With Enhanced Local Area Ratio

The performance and cost of Bi-2212/Ag wire is limited by the large fraction of Ag matrix (~3:1) that is required in the oxide-powder-in-tube fabrication process. An alternative fabrication process is being developed in which fine-powder Bi-2212 is uniaxially compressed to form bars with a thin Ag foil sheath. The fine powder naturally textures (aligns the a-bplanes perpendicular to the direction of compaction) with texture >80% using 200 MPa compression. A billet is formed by stacking trapezoidal-cross-section bars in a symmetric 8-12-16 pattern around an Ag rod and enclosed in an Ag-wall extrusion can. The billet is extruded and drawn to fine wire. Results are presented on present status of the development and testing.

Dense drug-eluting biodegradable Fe-Ag nanocomposites

Biodegradable metals in orthopedics are aimed to eliminate secondary the surgical intervention for implant removal, and thus improve patient compliance, reduce surgery costs and the risk of infections. In addition, biodegradable implants could be loaded with different drugs to prevent the growth of pathogens and the development of bone infections, kill remaining cancer cells after tumor resection or stimulate bone regeneration. However, drugs undergo thermal decomposition under the conditions of conventional metal fabrication processes. In this work, we describe the fabrication of a dense drug-eluting biodegradable Fe-Ag nanocomposite containing 10 vol% of Ag and loaded with the antibiotic vancomycin by consolidation at ambient temperature utilizing advanced cold sintering. Fabricated Fe10Ag nanocomposites loaded with 1 wt% VH combined strength of 225 and 123 MPa in compression and bending tests, respectively, and antibacterial activity against Staphylococcus aureus. Finally, the show good cell compatibility with a human osteoblast-like cell line. Our findings show the promise of this simple process to produce drug-eluting biodegradable metals.

Characterization of a New Lightened Gypsum-Based Material Reinforced with Fibers.

This paper shows the characterization of a new lightened gypsum-based material for use in buildings. A plaster material has been designed with a polymeric compound based on polyvinyl acetate, bicarbonate and a boric acid solution, which reduce the density and thermal conductivity by up to 20% and 30%, respectively. In addition, tests have been carried out with the lightened plaster material reinforced with glass (GF), basalt (BF), polypropylene (PPF) and wood (WF) fibers. A significant improvement in mechanical properties was achieved. All samples obtained resistance values greater than 2 MPa in flexion and 3 MPa in compression. Physico-chemical analysis were also carried out. The study is completed with a statistical analysis, where confidence intervals have been obtained for the mean at 95% confidence for each of the physical properties studied.

Materials modelling and process simulation of the pultrusion of curved parts

The present paper addresses the simulation of a concept for the manufacturing of aerospace quality carbon/epoxy composite curved parts using pultrusion. In this approach, the part is first partially cured in a pre-former followed by final curing in a curved post-former. An aerospace epoxy resin system has been fully characterised and the corresponding constitutive material models, incorporating dependence on both temperature and degree of cure, developed. A 3D Finite Element model of the process, to manufacture a T-stiffener, involving impregnation, curing and forming of the curvature was developed and implemented. The simulation results show that a degree of cure of around 62% -close to the gelation point of the resin system considered - at the exit of the pre-former stage is appropriate for the success of the subsequent stage. In the post-former the cure is completed reaching a final degree of cure of about 87%. The stresses generated in post-forming reach a maximum of 54 MPa in compression in the transverse direction and of 200 MPa in tension in the fibre direction showing that the process is feasible without inducing defects linked to micro buckling or rupture.