Microstrain Level Research Articles

Exploring vertebral bone density changes in a trunk with adolescent idiopathic scoliosis: a mechanobiological modeling investigation of intact and unilaterally paralyzed muscles

This study aimed to elucidate the vertebral bone density variations associated with adolescent idiopathic scoliosis (AIS), specifically examining the impact of unilateral muscle paralysis using an integrated approach combining Frost’s Mechanostat theory, a three-dimensional subject-specific finite element model and a musculoskeletal model of the L2 vertebra. The findings revealed a spectrum of bone density values ranging from 0.29 to 0.31 g/cm3, along with vertebral micro-strain levels spanning from 300 to 2200, consistent with existing literature. Furthermore, the ratio of maximum von Mises stress between the concave and convex side in the AIS model with intact muscles was approximately 1.08, which decreased by 4% due following unilateral paralysis of longissimus thoracis pars thoracic muscle. Overall, this investigation contributes to a deeper understanding of AIS biomechanics and lays the groundwork for future research endeavors aimed at optimizing clinical management approaches for individuals with this condition.

Fatigue Performance Evaluation of Fiber-Reinforced Asphalt Mixtures with Four-Point Bending Beam and Uniaxial Fatigue Tests

This study aimed to evaluate the fatigue cracking potential of aramid fiber–reinforced asphalt mixtures. Three fiber-reinforced asphalt mixtures (FRAMs) were prepared employing a singular aggregate type (diabase stone), one binder type (PG76-22), and two distinct combinations of aramid fibers at varying dosages. Two types of fiber were used at different dosages by weight of mix: polyolefin/aramid (PFA) fibers at a dosage 0.05% and sasobit-coated aramid (SCA) fibers at dosages of 0.01% and 0.02%. Additionally, an unreinforced (control) mix was also produced for comparison purposes. Each of the mixtures was produced at a batch plant, adhering to the fiber manufacturer’s recommended mixing methods, while maintaining a constant binder content of 5.5% based on the total mix weight. Four-point beam (4PB) fatigue, uniaxial fatigue (UF), and Texas overlay tests (OT) were performed to characterize the fatigue and reflective cracking behavior of FRAM. The 4PB test results suggest that FRAM improved the fatigue life at lower strain levels (400 µε and 600 µε); however, at higher microstrain (800 µε) level, FRAM exhibited lower fatigue life than the control mix. Damage characteristic curves obtained from the UF tests showed better fatigue tolerance for reinforced mixtures, regardless of microstrain level. For cycles to failure under tensile loading, UF and OT test results indicated lower fatigue life of reinforced mixtures compared with the control mix. Therefore, under flexural loading the fiber-reinforced asphalt mixtures tend to improve the fatigue life. However, for direct tension load, reinforced mixtures tend to deteriorate the fatigue life when comparing cycles to failure at constant strain amplitude.

Molybdenum Based Manganese Oxides as Optoelectronic Nanomaterials: Synthesis, Structural & Optical Characterization

AbstractThis work reports the synthesis of molybdenum based manganese oxide nanomaterials named as (CH1‐CH5) via a facile hydrothermal approach. Nanomaterials were characterized through Powder XRD, SEM, BET, UV‐Vis, Photoluminescence, and FTIR analysis. Structural characterization revealed triclinic crystal structure of nanomaterials having particle sizes in the range of 23.08–52.7 nm with very low levels of microstrain levels (<0.05) and dislocation densities. Surface areas were found to be in the range of 42.37–52.32 m2/g with mesoporous structures and solid bar and cross surface morphology. Optical band gaps (Eg) calculated from absorption data was found to be in the range of 4.65–4.75 eV for direct transitions whereas 4.60–4.74 eV for indirect transitions. The Eg calculated from emission data was found to be in the range of 2.42–2.67 eV. Absorption edge broadening was investigated by urbach energy (EU) calculated to be in the range of 1.23–1.51 eV whereas fermi energy (Ef) were obtained as 4.66–4.72 eV. Refractive index (n) was calculated to be in the range of 0.13–0.21 whereas high values obtained for real and imaginary parts of dielectric constants (ϵ) indicating polarization relaxation in synthesized materials. The calculated structural and optical characteristics indicates that these materials can be potential candidates for optoelectronic and catalytic applications.

Monitoring the Durability Issues of Asphalt Concrete Mixtures

The asphalt concrete mixture is prone to environmental issues such as moisture damage and ageing. This may exhibit a great significance in the service performance of asphalt concrete pavement mixtures which may be more susceptible to many types of early distresses throughout its fatigue life. In the present investigation, asphalt concrete mixtures were prepared and compacted with the aid of laboratory roller compaction into a slab samples. optimum binder content was implemented. Extra samples were prepared at higher and lower binder content of 0.5 % (above and below the optimum). Asphalt concrete beam specimens were obtained from the prepared slab samples with the aid of a diamond saw. Part of the Asphalt concrete beam specimens were tested under four point’s repeated flexural stresses after practicing moisture damage while another part was subjected to long term ageing. The rate of change in the flexural strength was monitored and compared among the various testing conditions at 20 ºC environment and under constant micro-strain level of 750. It was observed that the lower flexural strength was observed for moisture damaged specimens while higher flexural strength could be detected for aged specimens as compared with the control mixtures. The binder content exhibits a significant influence on flexural strength of the asphalt concrete specimens since it declines significantly at higher or lower binder content as compared with that of specimens prepared at the optimum.

Fatigue and stiffness characteristics of asphalt mixtures made of recycled aggregates

This research studies the stiffness characteristics and fatigue life of several asphalt mixtures made of recycled glass, reclaimed asphalt pavement (RAP), and recycled concrete aggregate (RCA). Experiments were carried out at 5–35 °C, loading frequencies of 0.1–20 Hz, and at two microstrain levels of 200 and 400 µm/m. To date, the effect of extensive parametric combinations of loadings, microstrain levels, and temperatures on asphalt mixtures made entirely of recycled materials (RM) has not been undertaken. The findings exhibited superior stiffness characteristics and improved fatigue life of some RM mixtures compared to control mixtures. The next step of this study included the optimization of three existing fatigue life prediction models. In addition, a prediction model was developed based on nominal maximum aggregate size (NMAS), percentage of RCA, and percentage of RAP in the asphalt mixture. The optimized models resulted in a much higher coefficient of determination (R2) and P-value (likelihood) in the statistical T-test compared to the existing prediction models utilized in this study. The developed model yielded R2 values close to 0.99 between measured and predicted fatigue life, indicating an enhanced accuracy in the prediction. Comparison of the estimated dissipation energy of mixtures supported and validated the fatigue testing outcomes.

On the enhanced dielectric and magnetic properties of BiFeO3 ceramics sintered under meta-stable conditions

Multiferroic BiFeO3 (BFO) ceramics are synthesized by non-thermodynamically stable methods, such as fast firing, cryomilling and Spark Plasma Sintering (SPS) with applied pressure of 60 MPa and high heating rate of 150 K/min. We obtained BFO ceramics and powders that present enhanced magnetic and electrical properties. The observed enhancements are caused by the chosen routes, such as cryomilling, which causes a significant reduction of crystallite size, reaching 23 nm, and a high micro-strain level, reaching 1.2%. This is reflected in the magnetic curve which is changed from antiferromagnetic-like to weak-ferromagnetic-like, with an increased maximum magnetization from 0.085 emu/g to 0.369 emu/g. The dielectric constant reached a high value, close to Ɛ’= 102 coupled with low dielectric loss (tan δ ∼ 0.019) over a wide range of frequencies (1 kHz to 2 MHz), reaching values close to 0.005 near 2 MHz. Such dielectric constant (dielectric loss) values are generally present for highly resistive ceramics. By equivalent circuit fitting we managed to separate the grain and grain boundary contributions. These results and those from XRD diffraction and Mössbauer spectroscopy indicate a migration of defects to the surface of the grains. In summary, we managed to consolidate this sintering method as a powerful method to obtain BFO ceramics with enhanced electrical and magnetic properties. Such improvements, especially the high resistivity and low tangent losses, can open new avenues for future technological applications of BiFeO3 nanostructured ceramics, such as ferroelectric memories and the magnetic enhancements for spintronic based devices.

Detecting the Impact of Micro and Nano Size Additives on Deformation of Asphalt Concrete

Permanent deformation is considered as one of the major distress type of asphalt concrete pavement in the hot climate region. It can be controlled by the use of additives either for asphalt binder or for the asphalt concrete mixture. In the present assessment, the impact of micro and Nano size additives (fly ash and silica fumes) on the deformation behaviour of asphalt concrete mixtures was assessed. Such additives were implemented as partial substitute of mineral filler. Asphalt concrete slab samples were prepared in the laboratory with the aid of roller compaction. The optimum percentages of the additives are (2 and 4) % of silica fumes and coal fly ash respectively by the weight of the binder. Beam specimens were obtained from the slab samples and tested for fatigue life under three constant strain levels using four point bending beam technique. It was observed that for mixture treated with Nano additive (silica fumes), the reduction in the permanent deformation starts at 0.0001 MJ/m3 loss in energy for 750 microstrain level. However, for mixture treated with Micro size additive (fly ash), as the dissipated energy vanishes, the permanent deformation was in the range of (3 - 4.5) microstrain. It was concluded that as the dissipated energy vanishes, the permanent deformation was lower by (29.4 and 11.7) % for mixtures treated with silica fumes and fly ash additives respectively as compared with the control mixture.

Influence of Additives on the Viscoelastic Behavior of Asphalt Concrete

Implication of mineral additives into the asphalt concrete mixture can influence the viscoelastic behavior; change the density, gradation, and strength properties. In the present investigation, fly ash and silica fumes were added to the asphalt concrete mixture. Slab samples were compacted with the aid of laboratory roller, and then beam specimens were sawed from the slab samples. The asphalt concrete beam specimens were subjected to repeated flexural stresses through the four-points bending test at 20℃ and under 400 micro-strain level until failure. The influence of the additives was monitored and compared. It was concluded that the phase angle, flexural stiffness, and the fatigue life declines while the cumulative dissipated energy increases after implication of the additives. However, the silica fumes additives exhibit a significant impact on the viscoelastic properties as compared with the control or the fly ash treated mixtures.

Detecting the Influence of Additives on Asphalt Concrete Durability

Modification of asphalt cement with additives is a sustainable issue. An attempt was made in the present assessment to detect the influence of modification of the asphalt binder by 2 % silica fumes and 4 % fly ash additives on the durability in terms of fatigue life of asphalt concrete mixture under short-term and long-term ageing processes and moisture damage. Asphalt concrete slab samples of wearing course was prepared and compacted by roller. The beam specimens of 400 mm length and 50 mm height and 63 mm width were extracted from the slab samples. The beam specimens had practiced the four-point repeated flexural bending beam test. The fatigue life was monitored as the number of load repetitions to reach the failure under three constant micro strain levels of (250, 400, and 750). The reduction in fatigue life after long-term ageing for control, silica fumes modified, and fly ash modified mixtures was (74.7, 38.4, and 60) %, (66.2, 52.4, and 64.3) %, (63.9, 63.1, and 57.5) % under 250, 400, and 750 microstrain levels respectively. However, the reduction in fatigue life after practicing moisture damage for control, silica fumes modified, and fly ash modified mixtures was (71.2, 59.6, and 37.2) %, (37.1, 64.9, and 11.2) %, (71, 84.8, and 32.2) % under (250, 400, and 750) microstrain levels respectively. It was concluded that Fly ash exhibit lower susceptibility to long-term ageing process as compared to other mixtures, while silica fumes exhibit lower susceptibility to moisture damage as compared to other mixtures.

Influence of Additives on the Fatigue Life and Stiffness of Asphalt Concrete

Implementation of additives to the asphalt binder can enhance the overall physical properties of the modified asphalt concrete. In the present assessment, an attempt has been made to use 2 % of silica fumes and 4 % of fly ash class F for modification of asphalt binder in wet process. Asphalt concrete wearing course mixtures have been prepared and compacted by roller in the laboratory. The beam specimens of 400 mm length and 50 mm height and 63 mm width were extracted from the slab samples. The specimens were subjected to the four-point repeated flexural bending beam test. The flexural stiffness was calculated under three constant micro strain levels of (250, 400, and 750). The fatigue life was monitored in terms the number of load repetitions to reach the required reduction in stiffness. It was concluded that the flexural stiffness increases by (11, and 15) %, (17.7, and 63.6) %, (57.2, and 65) % when 2% of silica fumes or 4 % of fly ash are implemented and the specimen’s practices 750, 400, and 250 microstrain levels respectively. However, the fatigue life of asphalt concrete beam specimens increases by (40, and 72.8) %, (115, and 220.6) %, (46, and 94.6) % when 2% of silica fumes or 4 % of fly ash are implemented and the specimen’s practices 750, 400, and 250 microstrain levels respectively. It is recommended to use modified binder with fly ash and silica fumes in asphalt concrete to enhance the fatigue life and stiffness.

La doped BiFeO3 ceramics synthesized under extreme conditions: Enhanced magnetic and dielectric properties

Multiferroic Bi0.85La0.15FeO3 powders and ceramics were synthesized under extreme conditions by a combination of high-energy ball cryomilling, fast firing and spark plasma sintering procedures. Single-phased and perovskite structured samples, where both rhombohedral (R3c space group) and orthorhombic (Pnma) phases coexist, were successfully processed. Highly dense (7.92 g/cm3, 97.5% of the theoretical one) and electrically resistive (2.19×1011Ω⋅cm) nano-structured ceramics with high internal micro-strain levels (up to 1.08%), small crystallite size (24 nm) and elevated magnetization (ranging from 0.204 to 0.350 emu/g at 15 kOe) with an expressive non-linear response were obtained by combining cryomilling, SPS and oxidative annealing. Particularly, the dielectric response is improved by oxidative annealing at 200 °C, reaching 170 at 1 kHz with very low loss tangent (2.5%). This study demonstrated the effectiveness of the chosen synthesis route in the production of BFO-based ceramics with enhanced ferroic properties.

Residual Stresses in Soft Magnetic FeTiB and FeZrN Films Obtained by Magnetron Deposition

The coercive field of soft magnetic ferromagnets is a structure-sensitive property and, in particular, is substantially affected by residual stresses. In the present study, the phase and structural states and residual stresses of the FeTiB and FeZrN films of various compositions, which were prepared by magnetron deposition on glass substrates and subsequent 1-h annealing at temperatures of 200–600 °C, were investigated by X-ray diffraction. The formation of a nanocrystalline structure is observed. It comprises different phases having different lattice parameters and unit-cell volumes and is characterized by high level of microstrains of grains as well; the microstrains predetermine the formation of high compressive stresses in the deposited films. As the annealing temperature increases, the compressive stresses decrease and, at certain temperatures, gradually transform into thermal tensile stresses, which are induced by the difference in the thermal expansion coefficients of the film and substrate. Thus, the heat treatment is the efficient way to improve the soft magnetic properties of the studied class of film materials produced by magnetron deposition.

Effects of mechanical milling time on densification, microstructural characteristics and hardness of Cu–SiC nanocomposites prepared by conventional sintering process

In this study, effects of the milling time on densification, microstructural characteristics and mechanical properties of Cu–SiC nanocomposite produced by high energy mechanical milling and conventional sintering process are investigated. Cu–SiC powder was milled for different durations and then cold compacted under 800 MPa pressure followed by conventional sintering at 900 °C under argon atmosphere for 1h. The microstructural characterization was conducted by x-ray diffraction (XRD), scanning electron microscope (SEM), and scanning transmission electron microscope (STEM). The highest densification for the composite powder was obtained at a short milling time, where the powder showed flake morphology and lower strain-hardening. By increasing the milling time, the size of the Cu matrix grains refined and the level of microstrain and microhardness of the nanocomposite improved. The incorporation of the nanoparticles in the Cu matrix increased the microhardness of the copper. This effect was more evident in lower milling durations.

Influence of severe plastic deformations in the bridgman anvil on lattice parameters and microhardness of ferromagnetic metals

The influence of severe plastic deformation by torsion in the Bridgman anvil on the lattice parameters of pure ferromagnetic metals Ni and Co is investigated by x-ray diffraction analysis. It is shown that torsion combined with strong compression leads to decrease in the lattice of these metals and to the change in the level of crystal lattice microstrains. The mechanisms of deformation influence on the lattice parameters are proposed.

A Fully Inkjet-Printed Strain Sensor Based on Carbon Nanotubes

A fully inkjet-printed strain sensor based on carbon nanotubes (CNTs) was fabricated in this study for microstrain and microcrack detection. Carbon nanotubes and silver films were used as the sensing layer and conductive layer, respectively. Inkjet-printed CNTs easily undergo agglomeration due to van der Waals forces between CNTs, resulting in uneven films. The uniformity of CNT film affects the electrical and mechanical properties. Multi-pass printing and pattern rotation provided precise quantities of sensing materials, enabling the realization of uniform CNT films and stable resistance. Three strain sensors printed eight-layer CNT film by unidirectional printing, rotated by 180° and 90° were compared. The low density on one side of eight-layer CNT film by unidirectional printing results in more disconnection and poor connectivity with the silver film, thereby, significantly increasing the resistance. For 180° rotation eight-layer strain sensors, lower sensitivity and smaller measured range were found because strain was applied to the uneven CNT film resulting in non-uniform strain distribution. Lower resistance and better strain sensitivity was obtained for eight-layer strain sensor with 90° rotation because of uniform film. Given the uniform surface morphology and saturated sheet resistance of the 20-layer CNT film, the strain performance of the 20-layer CNT strain sensor was also examined. Excluding the permanent destruction of the first strain, 0.76% and 1.05% responses were obtained for the 8- and 20-layer strain sensors under strain between 0% and 3128 µε, respectively, which demonstrates the high reproducibility and recoverability of the sensor. The gauge factor (GF) of 20-layer strain sensor was found to be 2.77 under strain from 71 to 3128 µε, which is higher than eight-layer strain sensor (GF = 1.93) due to the uniform surface morphology and stable resistance. The strain sensors exhibited a highly linear and reversible behavior under strain of 71 to 3128 µε, so that the microstrain level could be clearly distinguished. The technology of the fully inkjet-printed CNT-based microstrain sensor provides high reproducibility, stability, and rapid hardness detection.

Ferroelectric Sr3 Sn2 O7 :Nd3+ : A New Multipiezo Material with Ultrasensitive and Sustainable Near-Infrared Piezoluminescence.

Ultrasensitive and sustainable near-infrared (NIR)-emitting piezoluminescence is observed from noncentrosymmetric and ferroelectric-phase Sr3 Sn2 O7 doped with rare earth Nd3+ ions. Sr3 Sn2 O7 :Nd3+ (SSN) with polar A21 am structure is demonstrated to emit piezoluminescence of wavelength of 800-1500 nm at microstrain levels, which is enhanced by the ferroelectrically polarized charges in the multipiezo material. These discoveries provide new research opportunities to study luminescence properties of multipiezo and piezo-photonic materials, and to explore their potential as novel ultrasensitive probes for deep-imaging of stress distributions in diverse materials and structures including artificial bone and other implanted structures (in vivo, in situ, etc).

Study of Residual Stresses and Microstructural Changes in Charpy Test Specimens Reconstituted by Various Welding Techniques

Changes in the reactor pressure vessel (RPV) material properties due to neutron irradiation are monitored by means of surveillance specimen programs, which are used for realistic evaluation of the RPVs’ lifetime. Due to a limited number of surveillance specimens, the evaluation of reconstitution methods by various welding techniques after Charpy impact tests is of great importance. Time-of-flight (TOF) neutron diffraction method was used to determine the residual stress distributions and microstructural changes in Charpy specimens welded by arc stud, electron, and laser beam welding techniques. The lowest level of the residual stress in weld seams regions was found for the specimen welded by electron beam with optimal parameters as compared to other techniques. At the same time, this specimen exhibits the maximal level of microstrain, which points to high dislocation density in the material. The corresponding contributions to the yield strength due to various strengthening mechanisms were estimated.

Mineralogical characterization and strain analysis of the Marcellus shales

Due to the complex structure of the brittle formations like shale, their microcracking and mechanical deformation behavior are not well known. To understand the fundamental factors at the micron scale, Marcellus shales were cored both parallel and perpendicular to the bedding orientation and mechanically tested through triaxial creep test under constant stress. The parallel-bedded shales exhibited higher level of permanent strain in the radial direction, which increased with increasing time. This also confirmed their anisotropic nature due to the bedding. Their advanced characterization via X-ray diffraction (XRD) and Raman spectroscopy techniques before and after the creep tests revealed the mineralogical heterogeneity, and the presence of an organic matter (kerogen) concentrated in the microcrack areas. Besides, the XRD peak shifts and changes in peak shape indicated that there was a certain level of macrostrain and microstrain in the shale. Further investigation of the XRD peak shape (integral breadth) changes using the Williamson-Hall method demonstrated a higher concentration of lattice defects and associated microstrain (inhomogeneous lattice strain) present in the calcite phase compared to the quartz. The parallel-bedded shales also revealed a higher level of microstrain with respect to the perpendicular-bedding. The results proved that the microcracking (initiation and propagation) and associated mechanical deformation of the Marcellus shales were mostly influenced by the presence of organic matter, microstrain level (defect concentration) in the calcite mineral, and the bedding orientation.

Synthesis, characterisation and hydrogen sorption properties of mechanically alloyed Mg(Ni1-xMnx)2

Hydrogen storage materials based on the stoichiometry Mg(Ni1-xMnx)2 have been synthesized by High Energy Ball Milling (HEBM) and studied as potential candidate materials for solid state hydrogen storage. The microstructures of the as-cast and the milled alloys were characterized by means of X-ray Powder Diffraction (XRD) and Scanning Electron Microscopy (SEM) both prior and after the hydrogenation process. The storage characteristics (Pressure-Composition-Temperature isotherms) and the sorption kinetics obtained by a commercial and automatically controlled Sievert-type apparatus. The X-ray results showed that the substitution of Mn over Ni could eliminate and inhibit the MgNi2 phase. The calculation of the average crystallite size showed that the increase of the amount of Mn can reduce the size at the early stages, but for Mn content higher than 0.25 the crystallite size increases, while the microstrain levels decreased monotonically. The hydrogenation and dehydrogenation measurements took place at several temperatures (150–200–250–300 °C). The results showed that the kinetics for both the hydrogenation and dehydrogenation can be fast for operation at temperatures between 250 and 300 °C, but for temperatures below 200 °C the hydrogenation process is very slow, and the dehydrogenation process cannot be achieved.

Biomechanical Effect of an Exposed Dental Implant's First Thread: A Three-Dimensional Finite Element Analysis Study.

BackgroundThe purpose of this study was to assess the effect of different exposure levels of a dental implant’s first thread on adjacent bone stress and strain using the finite element analysis method.Material/MethodsThree-dimensional models of 2 threaded implants and abutments with a mandibular bone segment were constructed to represent the covered (C) and exposed models. In the exposed models, the implant was first placed in the bone, and rotated around its axis a quarter-turn each time to simulate 4 different levels of first thread exposure at the mid-lingual side: Upper Flank (UF), Thread Crest (TC), Lower Flank (LF), and Thread Root (TR) models. Oblique forces were applied and analysis was performed.ResultsMaximum compressive stress magnitude and distribution varied according to the exposed thread profile. In the exposed group, peak stress ranged from 136 MPa to 197 MPa in TC and LF models, respectively, compared to 141 MPa in C model. In LF, UF, and C models, peak stress was observed at the mid-lingual side of the crestal region, while in TC and TR models, peak stress shifted distally in accordance with thread profile. However, alveolar bone volumes which exhibited compressive microstrain levels within the physiological loading and maintenance windows were relatively close in all models.ConclusionsResults suggest that the exposed thread profile influences stress and strain outcomes in the adjacent bone; however, this influence is only limited to a small region around the exposed thread.