Fibre Bragg Grating (FBG) sensors are gaining popularity in biomedical engineering. However, specific standards for in vivo testing for their use are absolutely limited. In this study, in vitro ...experimental tests were performed to investigate the behaviors and applications of gratings attached to intact and fractured thighbone for a range of compression loading (<300 N) based around some usual daily activities. The wavelength shifts and the corresponding strain sensitivities of the FBG sensors were measured to determine their effectiveness in monitoring the femoral fracture healing process. Four different arrangements of FBG sensors were selected to measure strains at different critical locations on the femoral sawbones surface. Data obtained for intact and plated sawbones were compared using both embedded longitudinal and coiled FBG arrays. Strains were measured close to the fracture, posterior linea aspera and popliteal surface areas, as well as at the proximal and distal ends of the synthetic femur; their responses are discussed herein. The gratings on the longitudinally secured FBG arrays were found to provide high levels of sensitivity and precise measurements, even for relatively small loads (<100 N). Nevertheless, embedding angled FBG sensors is essential to measure the strain generated by applied torque on the femur bone. The maximum recorded strain of the plated femur was 503.97 µε for longitudinal and −274.97 µε for coiled FBG arrays, respectively. These project results are important to configure effective arrangements and orientations of FBG sensors with respect to fracture position and fixation implant for future in vivo experiments.
In this paper, a multi-scale model for AA3104-H19 and AA2024-T3 aluminium alloy with strong cold rolled crystallographic texture is proposed. This model consists of two components: (i) a full-field ...crystal plasticity spectral method using fast Fourier transformation (CPFFT) that can be used to predict anisotropic mechanical properties in both the in and out-of-plane uniaxial and multi-axial stress states and (ii) a 3D new phenomenological anisotropic yield function with enough flexibility to describe the in and out-of-plane mechanical anisotropies of strongly textured aluminium alloy sheet. This multi-scale model was implemented into a commercial finite element (FE) software Abaqus via a user-defined material subroutine UMAT to predict the anisotropic plastic deformation in a multi-step forming process (deep drawing). Results showed that this new modelling approach is able to accurately predict earing profiles with multiple ears in deep drawn cups based on the crystallographic texture information data obtained from orientation density functions (ODFs).
Several chromitite pods of variable sizes are hosted in dunite-harzburgite of the about 14 km
2
mining district of Nazdasht, in the Colkahan ultramafic complex, located in the Haji Abad-Esfandagheh ...district in the Kerman province, southeastern Iran. Olivine, orthopyroxene, and to a lesser extent clinopyroxene of a highly refractory nature, are the primary silicates found in the dunites and harzburgites. The matrix minerals between chromian spinel grains are serpentinized olivine and pyroxene, Cr-rich chlorite (kaemmererite), uvarovite, and veins of magnesite. Chromian spinel mainly occurs as massive chromitite pods and as thin massive chromitite bands together with minor disseminations in dunites and harzburgites. Chromian spinels in massive chromitites show relatively high Cr-numbers (0.60–0.82), Mg-numbers (0.54–0.74) and very low TiO
2
contents (averaging 0.16 wt.%) which may reflect the crystallization of chromite from a boninitic magma. The Fe
3+
-number is very low, down to <0.17 wt.%, in the chromian spinel of chromitites and associated peridotites of the Colkahan ultramafic complex. The harzburgite and dunite contain accessory chromian spinel with Cr-numbers of about 0.66 and 0.69, respectively. The Colkahan dunites and harzburgites are high depleted with low CaO (0.01–0.47 wt.%) and Al
2
O
3
(0.29–0.64 wt.%) compared to primitive mantle.
The chemical and mineralogical characteristics of these chromitites have a strong affinity to podiform chromitites in the mantle section of supra-subduction zone ophiolites. Calculated parental melts of the chromitites and geochemical discrimination diagrams based on mineral chemistry of peridotites are consistent with the differentiation of arc related magmas with boninitic affinity and support the supra-subduction paleogeodynamic setting of Haji Abad-Esfandagheh district previously proposed by some authors.
The Abdasht complex is a major ultramafic complex in south-east Iran (Esfandagheh area). It is composed mainly of dunite, harzburgite, podiform chromitites, and subordinate lherzolite and wehrlite. ...The podiform chromitites display massive, disseminated, banded and nodular textures. Chromian spinels in massive chromitites exhibit a uniform and restricted composition and are characterized by Cr# =Cr/(Cr+Al) ranging from 0.76 to 0.77, Mg# =Mg/(Mg+Fe2+) from 0.63 to 0.65 and TiO2<0.2wt.%. These values may reflect crystallization of the chromian spinels from boninitic magmas. Chromian spinels in peridotites exhibit a wide range of Cr# from 0.48 to 0.86, Mg# from 0.26 to 0.56 and very low TiO2 contents (averaging 0.07wt.%). The Fe3+# is very low, (<0.08wt.%) in the chromian spinel of chromitites and peridotites of the Abdasht complex which reflects crystallization under low oxygen fugacities.
The distribution of platinum group elements (PGE) in Abdasht chromitites displays a high (Os+Ir+Ru)/(Rh+Pt+Pd) ratio with strongly fractionated chondrite-normalized PGE patterns typical of ophiolitic chromitites. Moreover, the Pd/Ir value, which is an indicator of PGE fractionation, is very low (<0.1) in the chromitites.
The harzburgite, dunite and lherzolite samples are highly depleted in PGE contents relative to chondrites. The PdN/IrN ratios in dunites are unfractionated, averaging 0.72, whereas the harzburgites and lherzolites show slightly positive slopes PGE spidergrams, together with a small positive Ru anomaly, and their PdN/IrN ratio averages 2.4 and 2.3 respectively. Moreover, the PGE chondrite and primitive mantle normalized patterns of harzburgite, dunite and lherzolite are relatively flat which are comparable to the highly depleted mantle peridotites.
The mineral chemistry data and PGE geochemistry indicate that the Abdasht chromitites and peridotites were generated from a melt with boninitic affinity under low oxygen fugacity in a supra-subduction zone setting. The composition of calculated parental melts of the Abdasht chromitites is consistent with the differentiation of arc-related magmas.
Display omitted
•This study documents ultramafic complex from Southeastern Iran.•Podiform chromitites from the Abdasht ultramafic complex form a continuum from Cr#=0.76–0.77.•The parental melts had low TiO2 (0.27wt.%) but a range of Al2O3 (11.2–11.5wt.%).•The distribution of PGE in chromitites displays PGE patterns typical of ophiolitic chromitites.•Geochemical data indicating an arc related magma with boninitic affinity in a supra-subduction zone setting.
In the present work, rheological behavior of tungsten carbide (WC) slurries was evaluated to utilize it in gel-casting process, and effects of dispersant quantity and solids content on the viscosity ...of WC slurries were examined. It was found that tri-ammonium citrate to WC powder ratio of 0.25 was a preferable dispersant in such a non-toxic system. Maximum allowable WC powder was 25vol.% in the slurry. The slurry with 25vol.% WC powder and gelation additives was prepared, cast and dried at room temperature, then it was pre-sintered at 1450°C for 4h. Scanning electron microscope (SEM) micrograph of the pre-sintered WC foam showed a uniform porous microstructure. It had enough strength to be infiltrated with Zr2Cu molten. A reactive melt infiltration occurred during the practice, resulting in the formation of about 58vol.%W and 42vol.% ZrC in the final microstructure.
Display omitted
•Rheological behavior of WC slurry for gel-casting was evaluated.•Tri-ammonium citrate dispersant with 0.25 ratio to WC was preferable.•The suitable solid content of WC slurry was in the range of 20–25vol.%.•The pre-sintered foam had enough strength to be infiltrated by liquid metal.
In this study, nontoxic sodium alginate was utilized in gel-casting process to fabricate tungsten carbide (WC) micro-porous foam. Suspensions containing 20 and 25vol.% WC and 1wt.% sodium alginate ...were used. Calcium phosphate and sodium hexa-metaphoshphate were employed as solidifier agent and chelator, respectively. The green bodies were dried at room temperature for 36h and pre-sintered at 1450°C for 4h. The influence of chelator and calcium salt on strength of dried green body was evaluated. Tungsten carbide foams with 50–60% porosity were successfully produced. SEM micrographs of tungsten carbide foams show a uniform porous microstructure, with average size of 0.75μm.
Display omitted
•Sodium alginate, a natural innoxious polymer, was employed for gel-casting process.•The gel was loaded by high density tungsten carbide powder.•Drying the slurry led to microporous foam with 50–60% porosity.•The dried green bodies exhibit homogenous pore distribution.•Pre-sintered bodies show microporous foams with average pore size of 0.75μm.
In the present work, tungsten carbide (WC) preforms were fabricated by gel-casting process, using different nontoxic Na-alginate to tertiary calcium phosphate ratios and different loadings of WC ...powder in the initial slurries. The gel-cast green bodies were dried and pre-sintered at 1723 K for 4 h and then reactively infiltrated by molten Zr
2
Cu at 1623 K for 0.5 h, to produce W-ZrC composite via displacive compensation of porosity process. The phases, microstructures, and mechanical properties of the preforms and the W-ZrC composites were investigated by Fourier transform infrared spectroscope, x-ray diffractometer (XRD), scanning electron microscope (SEM), image analyzer, and universal mechanical testing machine. XRD results, SEM micrographs, and elemental maps indicated uniform distribution of phases (W and ZrC) and elements (W, Zr, and C). Flexural strengths and hardness of the fabricated composites were in the ranges of 429-460 MPa and 7.5-9.5 GPa, respectively. Fractography studies revealed two types of dimple rupture and cleavage fracture modes in different composite samples. The W-ZrC composite was ablated by an oxyacetylene flame for 60 s. The mean value of mass and linear ablation rates of the composite were 2.1 ± 0.1 mg/s and 3.6 ± 0.5 µm/s, respectively.
Femur diaphysis fractures almost always require surgery to heal. The femur recovery process may take 3–6 months or even longer. The current femur recovery assessment methods are qualitative and ...mainly rely on physicians' clinical experience. A better methodology to quantify the healing status will help the physicians counsel their patients on the appropriate load-bearing activities accordingly. This paper numerically and experimentally demonstrates a femur healing assessment methodology using fibre Bragg grating (FBG) sensors. Finite Element (FE) analysis was conducted to confirm the feasibility of the used epoxies. For the experiments, a fourth-generation composite femur (4GCF) sample fixated with an implant plate was prepared. The sample was instrumented with a total of six FBGs on the proximal and distal posterior, mid-shaft, and implant surfaces. The prepared sample was then subjected to cyclic loading on a hydraulic tensile machine in various situations including (1) intact, (2) fractured (mid-shaft transverse and wedge), and (3) epoxy-healed. Epoxies with different curing times were applied on the fractured femur to mimic bone regeneration stages as they harden. FBGs were used to monitor the alterations in the strain values during the healing stages. The results demonstrated that the strain values measured by FBGs were able to justify the non-union, mal-union, delayed union, and fully union conditions on the femur shaft compared to the intact and fractured conditions. The proposed assessment technique can potentially be used on long bones with various fracture types and for patients of different ages and recovery rates.
Display omitted
•Fractured femur healing process was quantitatively monitored and assessed.•Epoxies were applied on fractured femur to mimic bone regeneration stages as they cure.•Finite element analysis was used to investigate the utilised epoxies feasibility.•The healing extent of the femur is shown at each stage during the recovery time period.
Neanderthal anterior teeth are very large and have a distinctive morphology characterized by robust ‘shovel-shaped’ crowns. These features are frequently seen as adaptive responses in dissipating ...heavy mechanical loads resulting from masticatory and non-masticatory activities. Although the long-standing debate surrounding this hypothesis has played a central role in paleoanthropology, is still unclear if Neanderthal anterior teeth can resist high mechanical loads or not. A novel way to answer this question is to use a multidisciplinary approach that considers together tooth architecture, dental wear and jaw movements. The aim of this study is to functionally reposition the teeth of Le Moustier 1 (a Neanderthal adolescent) and Qafzeh 9 (an early Homo sapiens adolescent) derived from wear facet mapping, occlusal fingerprint analysis and physical dental restoration methods. The restored dental arches are then used to perform finite element analysis on the left central maxillary incisor during edge-to-edge occlusion. The results show stress distribution differences between Le Moustier 1 and Qafzeh 9, with the former displaying higher tensile stress in enamel around the lingual fossa but lower concentration of stress in the lingual aspect of the root surface. These results seem to suggest that the presence of labial convexity, lingual tubercle and of a large root surface in Le Moustier 1 incisor helps in dissipating mechanical stress. The absence of these dental features in Qafzeh 9 is compensated by the presence of a thicker enamel, which helps in reducing the stress in the tooth crown.
PDF
