MPa In Compression Research Articles

An in vivo model of a mechanically-induced bone marrow lesion

Bone marrow lesions (BMLs) are radiologic abnormalities in magnetic resonance images of subchondral bone that are correlated with osteoarthritis. Little is known about the physiologic processes within a BML, although BMLs are associated with mechanical stress, bone tissue microdamage and increased bone remodeling. Here we establish a rabbit model to study the pathophysiology of BMLs. We hypothesized that in vivo loads that generate microdamage in cancellous bone would also create BMLs and increase bone remodeling. In vivo cyclic loading (0.2–2.0 MPa in compression for 10,000 cycles at 2 Hz) was applied to epiphyseal cancellous bone in the distal femurs of New Zealand white rabbits (n=3, right limb loaded, left limb controls experienced surgery but no loading). Magnetic resonance images were collected using short tau inversion recovery (STIR) and T1 weighted sequences at 1 and 2 weeks after surgery/loading and histological analysis of the BML was performed after euthanasia to examine tissue microdamage and remodeling. Loaded limbs displayed BMLs while control limbs showed only a small BML-like signal caused by surgery. Histological analysis of the BML at 2 weeks after loading showed increased tissue microdamage (p=0.03) and bone resorption (p=0.01) as compared to controls. The model described here displays the hallmarks of load-induced BMLs, supporting the use of the model to examine changes in bone during the development, progression and treatment of BMLs.

Glass Ceramic Materials Based on Beneficiation Tailings of Lead-Zinc Ore

A glass ceramic material was obtained from the beneficiation tailings of lead-zinc ores. The strength of the control samples was 22.26 MPa in bending and 90.22 MPa in compression. After 100 cycles of testing the samples for frost resistance, these characteristics changed to 9.61 MPa in bending and 35.30 MPa in compression.

A cell attracting composite of lumbar fusion cage

Lumbar fusion cages are devices used in spinal fusion procedures for disorders such as spondylosis and degenerative disc diseases that may occur due to age, trauma or genetic reasons. These devices are most frequently made of metals and polymers. The mechanical properties of such devices should be comparable to the bone to avoid stress shielding. Besides, cages should interact with the cells to prevent extrusion and achieve satisfactory fusion. In this study, poly(methylmethacrylate) (PMMA) and hydroxyapatite (HAp) were compounded to create products with HAp contents up to 40% (w/w), processed by hot melt extrusion and injection molded to produce composites with maximum polymer-mineral interaction. The morphology, interaction with the plates and rate of proliferation of human osteoblast-like (HOB) cells were studied in vitro. We learned that cells interact more with HAp when the HAp content is higher than 20%. Tensile and compressive properties of PMMA were significantly increased with increasing HAp content; from an elastic modulus (E) of 2.08 to 3.92 GPa in tension, and from 349 to 562 MPa in compression. High HAp content of the samples increased the roughness from 0.69 μm for pure PMMA to 1.35 μm for 40% (w/w) HAp loaded PMMA, increased cell proliferation and as a result the cells presented filopodia indicating a satisfactory level of interaction with the cage surface. Based on mechanical and in vitro studies, a HAp content of around 30% (w/w) was found to be appropriate for good cell adhesion and satisfactory mechanical properties for use in the construction of a fusion cage. It was concluded that when PMMA and HAp were compounded at an optimal value, a cage material with adequate mechanical properties and increased cell attachment can be obtained for use in spinal fusion applications.

Unidirectional Abaca Fiber Reinforced Thermoplastic Starch Composite

Unidirectional abaca fiber reinforced thermoplastic starch composite was prepared via compression molding by varying the fiber volume fraction, compression pressure and fiber treatment. Factorial analysis at 95% confidence level has shown that changing fiber volume from 5% to 10% has a significant effect on the tensile strength of the composite. A treatment-pressure interaction was also found to have significant effect on the tensile strength of the composite. Result of tensile test showed that composite fabricated using 6.89 MPa (1000 psi) compression pressure, 10% fiber volume, and treated fibers exhibited the highest tensile strength of 19.73MPa while composite fabricated using 6.89 MPa (1000 psi) compression pressure, 10% fiber volume and untreated fibers exhibited only a tensile strength of 12.30 MPa. Scanning electron microscopy (SEM) on the transverse cross section has shown that alkali treatment was able to improve the interfacial bond between the fibers and the thermoplastic starch matrix resulting to an increase in strength of the composite fabricated at 6.89 MPa (1000 psi). However, using a compression pressure of 13.79 MPa (2000 psi) during fabrication induced damage, i.e. internal cracking, on the alkali treated fibers, thereby reducing the strength of the composite.

Influence of Synthesis Parameters on the Microstructure and Mechanical Property of Thermoplastic Starch

Thermoplastic starch was prepared via compression molding in a stainless steel mold having dimensions of 150 mm x 150 mm x 2mm. Thermoplastic starch was prepared by varying the compression temperature, compression pressure and duration of compression. The starch was extracted from bitter cassava (Manihot esculenta crantz), Datu 1 variety. Tensile properties of the material were found to be dependent on the specific conditions at which molding was done. Factorial analysis showed a significant effect of the temperature-pressure interaction on the tensile strength of thermoplastic starch at 95% confidence level. Thermoplastic starch prepared using the compression molding parameters of 105°C and 6.89 MPa (1000 psi) compression pressure exhibited the highest tensile strength of 464.88 kPa. However, using the molding parameters of 105°C and 6.89 MPa (2000 psi) compression pressure exhibited the lowest tensile strength of 416.64 kPa. Introduction of gelatinizing agents and compression molding up to 105 °C and 13.79 MPa (2000 psi) has partially caused the transformation of the microstructure of starch to a more amorphous state. This is shown by the disappearance of peaks at diffraction angles (2θ) of 12.45° (d1 = 0.71 nm), 14.85° (d2 = 0.6 nm), and 17.04° (d3 = 0.52 nm) and the increase in FWHM value at diffraction angle of 22.94° (d4 = 0.39 nm) from 3.05° (starch) to 11.43° (TPS).

Non-destructive micro-Raman analysis of Si near Cu through silicon via

Silicon near Cu through-silicon vias (TSVs) develops stresses during processing steps, and the local stress of Si around Cu TSVs of sizes ranging from 4 to 8 μm was characterized using micro-Raman spectroscopy as a function of processing steps. Micro-Raman measurements showed that the max stress sum, σr + σθ, is size dependent, where the stress sum of 88.7 MPa in the compressive direction was measured in Si for 8 μm sized Cu via, and this max stress sum, σr + σθ, decreased to 21 MPa in compression for 4 μm sized Cu via. With the deposition of oxide/nitride overlayers, the stress sum was found to switch sign to 138.9 MPa in the tensile direction for 8 μm sized Cu via after deposition of the SiN overlayers with residual compressive stress caused by ion bombardment. The measured stresses by micro-Raman was used to determine the keep-off-zone that can be used in device design to ensure reliability, and compared against the TCAD simulations results.

Shape memory and transformation behavior of high strength 60NiTi in compression

This study investigates the transformation behavior of highly Ni-rich 60NiTi alloys after aging at 600 °C for 3 h. After 600 °C-3h aging, R-phase disappeared and alloy transformed in one step. The latent heats of austenite to martensite and martensite to austenite transformations were 13 Jg−1 and 16.4 Jg−1, respectively, for 600 °C-3h aged alloy. The elastic strain energy of 0.75 Jg−1 was obtained in aged alloy. The maximum recoverable transformation strain of 1.7% is obtained under 500 MPa in compression. The superelastic behavior was observed accompanied with a recoverable strain of 1.4%, even high stress level of 1000 MPa is applied.

Concrete Slump Classification Using GLCM Feature Extraction

Digital image processing technologies have been widely applies in analyzing concrete structure because the accuracy and real time result. The aim of this study is to classify concrete slump by using image processing technique. For this purpose, concrete mix design of 30 MPa compression strength designed with slump of 0-10 mm, 10-30 mm, 30-60 mm, and 60-180 mm were analysed. Image acquired by Nikon Camera D-7000 using high resolution was set up. In the first step RGB converted to greyimage than cropped to 1024 x 1024 pixel. With open-source program, cropped images to be analysed to extract GLCM feature. The result shows for the higher slump contrast getting lower, but higher correlation, energy, and homogeneity.

Effect of internal stress on the electro-optical behaviour of Al-doped ZnO transparent conductive thin films

In this work, we will report on scientific efforts aimed at unraveling the quantitative effect of elastic strain on the electro-optical behaviour of Al-doped zinc oxide (AZO). AZO thin films have been deposited by reactive magnetron sputtering to thicknesses from 300 to 500 nm, both on extra-clear glass substrates as well as on oxidised Si wafers. This resulted in both cases in polycrystalline, strongly textured (002) films. During deposition, the internal stress evolution in the growing film was monitored in-situ using high resolution curvature measurements. The resulting growth-induced elastic strain, which was found to depend heavily on the oxygen partial pressure, could further be modulated by appropriately choosing the deposition temperature. The latter also induces an additional extrinsic thermal stress component, whose sign depends on the substrate used. As such, a wide range of biaxial internal stresses could be achieved, from −600 MPa in compression up to 800 MPa in tension. The resulting charge carrier mobilities, obtained independently from room temperature Hall measurements, were found to range between 5 and 25 cm2/V s. Interestingly, the maximum mobility occurred at the zero-stress condition, and together with a charge carrier concentration of about 8 × 1020 cm−3, this gave rise to a resistivity of only 300 μΩ cm. From the stress-dependent optical transmission spectra in the range of 200–1000 nm, the pressure coefficient of the optical bandgap was estimated from the corresponding Tauc plots to be 31 meV/GPa, indicating a very high strain-sensitivity as well.

Performance of Ferro Foam Concrete Girder Beam Subjected to Static Load

Ferro foam concrete is an alternative material which consist of a combination between wire mesh and foam concrete. The advantage of this material is in addition to its ability to carry the load, this type of material is lightweight, and easy to be produced. The objectives of this study are to study performance of ferro foam concrete girder beam subjected to static load, and to investigate the beam to be used as an alternative material for bridge girder. Six ferro foam concrete channel profile that is configured into three I profile with 300 mm, 450 mm, and 600 mm with four layer wire mesh were tested in Structural Laboratory of Syiah Kuala University. This profile has a span of 2000 mm, and 150 mm, 175 mm, and 300 mm wingspan. Foam concrete used in this research consist of cement, water, foam agent, and 10 % pozzolan. Material properties for concrete 32.47 MPa compression strength, and 421 MPa for yield strength of reinforcement with D8, and 421 MPa for wire mesh G 12.7. The specimens were tested using four point loading. Three units of LVDT placed at a distance of 250 mm and 1000 mm from the support. Based on test results, it was found that the maximum load that can be carried by the channel profile configuration I with 300 mm height is 17.45 tf on deflection of 23.32 mm, for a profile with a height of 450 mm is 20.72 tf on deflection of 14.85 mm, and for a profile with a height of 600 mm was 22.48 tf on deflection of 37.74 mm.

Inflammatory conditions partly impair the mechanically mediated activation of Smad2/3 signaling in articular cartilage.

BackgroundJoint trauma, which is frequently related with mechanical overloading of articular cartilage, is a well-established risk for osteoarthritis (OA) development. Additionally, reports show that trauma leads to synovial joint inflammation. In consequence, after joint trauma, cartilage is influenced by deleterious excessive loading combined with the catabolic activity of proinflammatory mediators. Since the activation of TGF-β signaling by loading is considered to be a key regulatory pathway for maintaining cartilage homeostasis, we tested the effect of proinflammatory conditions on mechanically mediated activation of TGF-β/Smad2/3P signaling in cartilage.MethodsCartilage explants were subjected to dynamic mechanical compression in the presence of interleukin-1 beta (IL-1β) or osteoarthritic synovium-conditioned medium (OAS-CM). Subsequently, the activation of the Smad2/3P pathway was monitored with QPCR analysis of reporter genes and additionally the expression of receptors activating the Smad2/3P pathway was analyzed. Finally, the ability for mechanically mediated activation of Smad2/3P was tested in human OA cartilage.ResultsIL-1β presence during compression did not impair the upregulation of Smad2/3P reporter genes, however the results were affected by IL-1β-mediated upregulations in unloaded controls. OAS-CM significantly impaired the compression-mediated upregulation of bSmad7 and Tgbfb1. IL-1β suppressed the compression-mediated bAlk5 upregulation where 12 MPa compression applied in the presence of OAS-CM downregulated the bTgfbr2. Mechanically driven upregulation of Smad2/3P reporter genes was present in OA cartilage.ConclusionsProinflammatory conditions partly impair the mechanically mediated activation of the protective TGF-β/Smad2/3P pathway. Additionally, the excessive mechanical compression, applied in the presence of proinflammatory conditions diminishes the expression of the type II TGF-β receptor, a receptor critical for maintenance of articular cartilage.

Concrete Slump Classification using GLCM Feature Extraction

Digital image processing technologies have been widely applies in analyzing concrete structure because the accuracy and real time result. The aim of this study is to classify concrete slump by using image processing technique. For this purpose, concrete mix design of 30 MPa compression strength designed with slump of 0-10 mm, 10-30 mm, 30-60 mm, and 60-180 mm were analysed. Image acquired by Nikon Camera D-7000 using high resolution was set up. In the first step RGB converted to greyimage than cropped to 1024 x 1024 pixel. With open-source program, cropped images to be analysed to extract GLCM feature. The result shows for the higher slump contrast getting lower, but higher correlation, energy, and homogeneity.

Microstructure and shape memory behavior of [111]-oriented NiTiHfPd alloys

The relationship between the microstructure and shape memory properties of [111]-oriented Ni45.3Ti29.7Hf20Pd5 (at%) single crystals was explored. In this precipitation-strengthened alloy, the size and volume fraction of precipitates and interparticle distances govern the martensite morphology and the ensuing shape memory responses. Aging of the solution-treated material, leading to a microstructure of fine, closely spaced precipitates, resulted in a material capable of a shape memory strain of 2.15% at 1000 MPa in compression. Larger precipitates formed after aging the as-grown single crystals (without a prior solution treatment) resulting in a shape memory strain of 2.5% at this same stress level in constant-stress thermal cycling experiments. Superelastic strains of 4% in compression without any residual strain were possible under various microstructural conditions and the stress hysteresis could be varied between nearly 500 and 1000 MPa depending on the microstructure.

Development of a Resorbable Calcium Phosphate Cement with Load Bearing Capacity

Compared to cortical bone and polymeric bone cements, the mechanical properties of calcium phosphate cements are generally poor. This has resulted in them being used in non-load bearing clinical applications. The aim of this study was to investigate the possibility of producing a brushite cement with mechanical properties closer to those of cortical bone (i.e., >100 MPa in compression), i.e. with a potential to be used in load bearing applications. With a compressive strength of 74.4 (± 10.7) MPa, maximum at 91.8 MPa, the cement presented herein is comparable with the non degradable polymeric counterparts and the strongest hydroxyapatite cements, and is close in strength of cortical bone. Furthermore, it has a high injectability (>90%) and a setting time of approximately 17 minutes. A cement comprising these properties has great potential of changing the future clinical indications for calcium phosphate cements, and could potentially reduce the use of non-degradable polymeric cements.

Strength reliability and in vitro degradation of three-dimensional powder printed strontium-substituted magnesium phosphate scaffolds

Strontium ions (Sr2+) are known to prevent osteoporosis and also encourage bone formation. Such twin requirements have motivated researchers to develop Sr-substituted biomaterials for orthopaedic applications. The present study demonstrates a new concept of developing Sr-substituted Mg3(PO4)2 – based biodegradable scaffolds. In particular, this work reports the fabrication, mechanical properties with an emphasis on strength reliability as well as in vitro degradation of highly biodegradable strontium-incorporated magnesium phosphate cements. These implantable scaffolds were fabricated using three-dimensional powder printing, followed by high temperature sintering and/or chemical conversion, a technique adaptable to develop patient-specific implants. A moderate combination of strength properties of 36.7MPa (compression), 24.2MPa (bending) and 10.7MPa (tension) were measured. A reasonably modest Weibull modulus of up to 8.8 was recorded after uniaxial compression or diametral tensile tests on 3D printed scaffolds. A comparison among scaffolds with varying compositions or among sintered or chemically hardened scaffolds reveals that the strength reliability is not compromised in Sr-substituted scaffolds compared to baseline Mg3(PO4)2. The micro-computed tomography analysis reveals the presence of highly interconnected porous architecture in three-dimension with lognormal pore size distribution having median in the range of 17.74–26.29μm for the investigated scaffolds. The results of extensive in vitro ion release study revealed passive degradation with a reduced Mg2+ release and slow but sustained release of Sr2+ from strontium-substituted magnesium phosphate scaffolds. Taken together, the present study unequivocally illustrates that the newly designed Sr-substituted magnesium phosphate scaffolds with good strength reliability could be used for biomedical applications requiring consistent Sr2+- release, while the scaffold degrades in physiological medium. Statement of significanceThe study investigates the additive manufacturing of scaffolds based on different strontium-substituted magnesium phosphate bone cements by means of three-dimensional powder printing technique (3DPP). Magnesium phosphates were chosen due to their higher biodegradability compared to calcium phosphates, which is due to both a higher solubility as well as the absence of phase changes (to low soluble hydroxyapatite) in vivo. Since strontium ions are known to promote bone formation by stimulating osteoblast growth, we aimed to establish such a highly degradable magnesium phosphate ceramic with an enhanced bioactivity for new bone ingrowth. After post-processing, mechanical strengths of up to 36.7MPa (compression), 24.2MPa (bending) and 10.7MPa (tension) could be achieved. Simultaneously, the failure reliability of those bioceramic implant materials, measured by Weibull modulus calculations, were in the range of 4.3–8.8. Passive dissolution studies in vitro proved an ion release of Mg2+ and PO43- as well as Sr2+, which is fundamental for in vivo degradation and a bone growth promoting effect.In our opinion, this work broadens the range of bioceramic bone replacement materials suitable for additive manufacturing processing. The high biodegradability of MPC ceramics together with the anticipated promoting effect on osseointegration opens up the way for a patient-specific treatment with the prospect of a fast and complete healing of bone fractures.

Synthesis and characterization of polycyanurates as dismantlable adhesives

Random copolycyanurates with a low number of amide units in the main chain have been developed as a candidate of dismantlable adhesives based on the rapid decrease of the molecular weights during the rearrangement to polyisocyanurates by a thermal treatment. The random copolycyanurates were prepared by the phase-transfer-catalyzed polycondensation of 2,4-dichloro-6-methoxy-1,3,5-triazine with bisphenol A and a new bisphenol containing an amide unit in the presence of tetrabutylammonium bromide. They exhibited an excellent adhesive property for the silicon and copper deposited on the silicon substrate after the high thermal treatment of 240 °C under 0.6 MPa compression, and the die shear strengths of these polymers dramatically decreased at 260 °C for 1 h. Random copolycyanurates containing the amide unit are shown to be promising materials for dismantlable adhesion. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1153–1158

Study of Different Biomaterials for Artificial Lumbar Disc Prosthesis Using FEM

The purpose of this study was to analyze the behavior of a lumbar spine disc prosthesis with different materials. The study was performed at L4-L5 lumbar motion segment using the finite element method (FEM). A healthy Finite Element (FE) model was used as a reference with which to compare the results of the FE simulations of the artificial discs. The healthy and the artificial FE models were subjected to a combination of 0.5 MPa Compression pre-load and 10Nm of Flexion moment. The artificial FE models were based on Maverick artificial disc, and the three materials proposed for study the artificial disk were Titanium, Ceramic and CrCoMo alloy. The most suitable material for developed the artificial disc was the CoCrMo alloy due to: The von Mises stresses on the bone with which this artificial disc was in contact were reduced as much as possible and also, were very similar to the von Mises stresses obtained in the bones from the healthy disc.

Duration-dependent influence of dynamic torsion on the intervertebral disc: an intact disc organ culture study.

Mechanical loading is an important parameter that alters the homeostasis of the intervertebral disc (IVD). Studies have demonstrated the role of compression in altering the cellular metabolism, anabolic and catabolic events of the disc, but little is known how complex loading such as torsion-compression affects the IVD cell metabolism and matrix homeostasis. Studying how the duration of torsion affects disc matrix turnover could provide guidelines to prevent overuse injury to the disc and suggest possible beneficial effect of torsion. The aim of the study was to evaluate the biological response of the IVD to different durations of torsional loading. Intact bovine caudal IVD were isolated for organ culture in a bioreactor. Different daily durations of torsion were applied over 7 days at a physiological magnitude (±2°) in combination with 0.2 MPa compression, at a frequency of 1 Hz. Nucleus pulpous (NP) cell viability and total disc volume decreased with 8 h of torsion-compression per day. Gene expression analysis suggested a down-regulated MMP13 with increased time of torsion. 1 and 4 h per day torsion-compression tended to increase the glycosaminoglycans/hydroxyproline ratio in the NP tissue group. Our result suggests that load duration thresholds exist in both torsion and compression with an optimal load duration capable of promoting matrix synthesis and overloading can be harmful to disc cells. Future research is required to evaluate the specific mechanisms for these observed effects.

Partial gasification of lignite in a bed with a pulsed reverse blast

The aim of this work is to develop a technology of thermal processing of brown coal to produce carbonizate with increased strength. Here are presented the results of an experimental study of the process of partial gasification of brown coal (grade 3B) in the bed apparatus with pulsating reversed blow. In previous work, it was shown that satisfactory strength of a particle (no less than 8 MPa compression) is achieved by limiting the heating rate, as well as, the maximum temperature of the heating medium. To provide these conditions, it was proposed to use partial gasification of the coal in the fuel-bed apparatus using a pulsating supply mode of an oxidant. Parameters of blowing: flow rate 0.022 m3/(m2 s); blowing period 25 s; stop blowing period 150 s. Under these conditions, the producing lignite coke had a crush strength in the range of 8–10 MPa. The product yield was 56%.

Experimental Analysis of Hydrothermal Curing Influence on Properties of Fiber-Cement Composite

Special industrial application of fiber-cement composites is currently one important issue of concrete industry and research activity. The field of refractory and high-temperature resistance materials is very large and contains the cement composites too. Hydrothermal curing together with using aluminous cement with refractory basalt aggregates and fibers shows high potential for its applications in high temperature. These composite is characterized by compressive strength over 140 MPa and tensile strength in bending 12 MPa (investigated on specimens 40 x 40 x 160 mm). After exposure to temperature 1000 °C these parameters are 60 MPa in compression respective 6 MPa in bending. Achieved values are significantly higher than in the case of laboratory curing condition and there are suitable especially for prefabricated fire resistance cladding or other special application in the industry.