Microstructures and High-Temperature Properties of Sm-Modified Mg-4Al-4RE Alloy

The effect of Sm on the microstructure and tensile properties of Mg-4Al-4 (La, Ce) alloy was studied. The Mg-4Al-4 (La, Ce) alloy was mainly composed of α-Mg and Al11(La, Ce)3. With the addition of Sm, a new phase of Al2(La, Ce, Sm) was revealed in the alloy. The results showed that at room temperature (RT), after Sm addition, the ultimate tensile stress and the elongation decreased, while the yield stress increased slightly; the elongation increased with the Sm addition and the yield stress was basically the same, but the ultimate tensile stress decreased at an elevated temperature of 150 °C. The change in the mechanical properties of the alloy was mainly related to the change in microstructure and phase. With the increase in Sm content, the volume fraction of Al2(La, Ce, Sm) phase increased and the Al11(La, Ce)3 eutectic volume fraction decreased significantly, which led to a change in the mechanical properties of the alloy. The 1 wt.%Sm-addition alloy exhibited greater elongation than the Sm-free alloys.

Interfacial Stabilities, Electronic Properties and Interfacial Fracture Mechanism of 6H-SiC Reinforced Copper Matrix Studied by the First Principles Method

The interfacial mechanics and electrical properties of SiC reinforced copper matrix composites were studied via the first principles method. The work of adhesion (Wad) and the interfacial energies were calculated to evaluate the stabilities of the SiC/Cu interfacial models. The carbon terminated (CT)-SiC/Cu interfaces were predicted to be more stable than those of the silicon terminated (ST)-SiC/Cu from the results of the Wad and interfacial energies. The interfacial electron properties of SiC/Cu were studied via charge density distribution, charge density difference, electron localized functions and partial density of the state. Covalent C-Cu bonds were formed based on the results of electron properties, which further explained the fact that the interfaces of the CT-SiC/Cu are more stable than those of the ST-SiC/Cu. The interfacial mechanics of the SiC/Cu were investigated via the interfacial fracture toughness and ultimate tensile stress, and the results indicate that both CT- and ST-SiC/Cu interfaces are hard to fracture. The ultimate tensile stress of the CT-SiC/Cu is nearly 23 GPa, which is smaller than those of the ST-SiC/Cu of 25 GPa. The strains corresponding to their ultimate tensile stresses of the CT- and ST-SiC/Cu are about 0.28 and 0.26, respectively. The higher strains of CT-SiC/Cu indicate their stronger plastic properties on the interfaces of the composites.

Interfacial Stabilities, Electronic Properties and Interfacial Fracture Mechanism of 6H-SiC Reinforced Copper Matrix studied by the First Principles Method

The interfacial mechanics and electrical properties of the SiC reinforced copper matrix composites were studied via the first principles method. The work of adhesion (Wad) and the interfacial energies were calculated to evaluate the stabilities of the SiC/Cu interfacial models. The carbon terminated (CT)-SiC/Cu interfaces were predicted more stable than those of the silicon terminated (ST)-SiC/Cu from the results of the Wad and interfacial energies. The interfacial electron properties of SiC/Cu were studied via the charge density distribution, charge density difference, electron localized functions and partial density of the state. The covalent C-Cu bonds were formed based on the results of the electron properties, which further explained the fact that the interfaces of the CT-SiC/Cu are stable than those of the ST-SiC/Cu. The interfacial mechanics of the SiC/Cu were investigated via the interfacial fracture toughness and ultimate tensile stress, and the results indicate that both CT- and ST-SiC/Cu interfaces are hard to fracture. The ultimate tensile stress of the CT-SiC/Cu is nearly 23GPa, which is smaller than those of the ST-SiC/Cu of 25 GPa. The strains corresponding to their ultimate tensile stresses of the CT- and ST-SiC/Cu are about 0.28 and 0.26, respectively. The higher strains of CT-SiC/Cu indicate their stronger plastic properties on the interfaces of the composites.

Carbon Source Starvation of a Sulfate-Reducing Bacterium–Elevated MIC Deterioration of Tensile Strength and Strain of X80 Pipeline Steel

It is known that starved sulfate-reducing bacterial biofilms corrode carbon steel more aggressively because they use electrons from elemental iron oxidation as an alternative source of energy. This work used carbon source starvation to vary MIC (microbiologically influenced corrosion) severity for studying subsequent MIC impacts on the degradation of X80 carbon steel mechanical properties. X80 square coupons and dogbone coupons were immersed in ATCC 1249 culture medium (200 ml in 450-ml anaerobic bottles) inoculated with Desulfovibrio vulgaris for 3-day pre-growth and then for an additional 14 days in fresh media with adjusted carbon source levels for starvation testing. After the starvation test, the sessile cell counts (cells/cm2) on the dogbone coupons in the bottles with carbon source levels of 0, 10, 50, and 100% (vs that in the full-strength medium) were 8.1 × 106, 3.2 × 107, 8.3 × 107, and 1.3 × 108, respectively. The pit depths from the X80 dogbone coupons were 1.9 μm (0%), 4.9 μm (10%), 9.1 μm (50%), and 6.4 μm (100%). The corresponding weight losses (mg/cm2) from the square coupons were 1.9 (0%), 3.3 (10%), 4.4 (50%), and 3.7 (100%). The 50% carbon source level had the combination of carbon starvation without suffering too much sessile cell loss. Thus, both its pit depth and weight loss were the highest. The electrochemical tests corroborated the pit depth and weight loss trends. The tensile tests of the dogbone coupons after the starvation incubation indicated that sulfate-reducing bacteria (SRB) made X80 more brittle and weaker. Compared with the fresh (no-SRB-exposure) X80 dogbone coupon’s ultimate tensile strain of 13.6% and ultimate tensile stress of 860 MPa, the 50% carbon source level led to the lowest ultimate tensile strain of 10.3% (24% loss when compared with the fresh dogbone) and ultimate tensile stress of 672 MPa (22% loss). The 100% carbon source level had a smaller loss in ultimate tensile strain than the 50% carbon source level, followed by 10% and then 0%. Moreover, the 100% carbon source level had a smaller loss in ultimate tensile strength than the 50%, followed by 10% and 0% in a tie. This outcome shows that even in the 17-day short-term test, significant degradation of the mechanical properties occurred and more severe MIC pitting caused more severe degradation.

Intrinsic Tendon Regeneration After Application of Purified Exosome Product: An In Vivo Study

Background: Tendons are primarily acellular, limiting their intrinsic regenerative capabilities. This limited regenerative potential contributes to delayed healing, rupture, and adhesion formation after tendon injury. Purpose: To determine if a tendon’s intrinsic regenerative potential could be improved after the application of a purified exosome product (PEP) when loaded onto a collagen scaffold. Study Design: Controlled laboratory study. Methods: An in vivo rabbit Achilles tendon model was used and consisted of 3 groups: (1) Achilles tenotomy with suture repair, (2) Achilles tenotomy with suture repair and collagen scaffold, and (3) Achilles tenotomy with suture repair and collagen scaffold loaded with PEP at 1 × 1012 exosomes/mL. Each group consisted of 15 rabbits for a total of 45 specimens. Mechanical and histologic analyses were performed at both 3 and 6 weeks. Results: The load to failure and ultimate tensile stress were found to be similar across all groups ( P ≥ .15). The tendon cross-sectional area was significantly smaller for tendons treated with PEP compared with the control groups at 6 weeks, which was primarily related to an absence of external adhesions ( P = .04). Histologic analysis confirmed these findings, demonstrating significantly lower adhesion grade both macroscopically ( P = .0006) and microscopically ( P = .0062) when tendons were treated with PEP. Immunohistochemical staining showed a greater intensity for type 1 collagen for PEP-treated tendons compared with collagen-only or control tendons. Conclusion: Mechanical and histologic results suggested that healing in the PEP-treated group favored intrinsic healing (absence of adhesions) while control animals and animals treated with collagen only healed primarily via extrinsic scar formation. Despite a smaller cross-sectional area, treated tendons had the same ultimate tensile stress. This pilot investigation shows promise for PEP as a means of effectively treating tendon injuries and enhancing intrinsic healing. Clinical Relevance: The production of a cell-free, off-the-shelf product that can promote tendon regeneration would provide a viable solution for physicians and patients to enhance tendon healing and decrease adhesions as well as shorten the time required to return to work or sports.

Intrasound Therapy Improves the Mechanical Properties and the Morphology of Tendons in Fluoroquinolone-Induced Achilles Tendinopathy

Fluoroquinolones (FQs), especially Pefloxacin (PEF) have been reported to increase risk of Achilles tendon rupture. However, prior studies showed that intrasound therapy (ITR) significantly improved the morphology of the healing tendon. This study aimed to compare the effects of 7, 14 and 21 days intrasound treatment on the mechanical properties and morphology of the Achilles tendon in fifty (50) male Sprague-Dawley rats induced with FQ and randomized into three main categories designated as Normal control (A), Experimental control (B) and Treatment groups (C). All animals in groups B and C were orally administered PEF 400mg/kg in a fixed volume of 2.5 ml/kg daily for 6 consecutive days. The Achilles tendon of both hind limbs in group C were treated with the lowest intensity ITR 5 minutes daily for 7, 14 and 21 consecutive days. All the animals were serially sacrificed on days 8, 15 and 22 and the tendons excised and processed. Data were analyzed with RSTUDIO version 4.0.02 and the level of significance set at 0.05. Kruskal Wallis showed no significant differences (p >0.05) in all the biomechanical parameters across all the groups. Compared with group B, ITR 14 days treatment had the best improvement in all biomechanical variables, though insignificant (p>0.05). In the Intrasound groups, there were significant positive correlations of Nitric Oxide Synthase (NOS) with ultimate tensile stress and tensile load (p= 0.005; p=0.003) respectively. Intrasound treatment to the Achilles tendon for 14 days improved the mechanical properties and morphology of tendons in Fluoroquinolone-induced tendinopathy.

Simultaneous Improvement of the Electric Conductive and Mechanical Properties of Nanostructured Aluminum Alloy

Aluminum nanocomposites demonstrate improvements in the mechanical properties, as well as in thermal and electric conductivity. The incorporation of multiwalled carbon nanotubes (MWCNT) in the aluminum matrix, using conventional melting methods, is a long-standing issue. In this paper, Aluminum nanocomposites were fabricated via conventional casting method, using a nanostructured stainless-steel (SS) powder. Carbon nanotubes were treatment treated with hydrogen peroxide, allowed which led to an attachment with to the metal matrix particles. In this sense, The the SS powder, added as an element alloy, refinement refined the grains, and the MWCNT providedled the electric conductive to a better performance. Given this, the best alloy analyzed presented an approximate 10% increase in all of its characterized properties, that is,therefore presenting a microhardness of 48 HV, a Ultimate Tensile Stress of 183 Mpa, and and an electrical conductivity of 67% of IACS..

Experimental investigation into the effect of surface roughness and mechanical properties of 3D-printed titanium Ti-64 ELI after heat treatment

The initial stability after implantology is paramount to the survival of the dental implant, and the surface roughness of the implant plays a vital role in this regard. The characterisation of surface topography is a complicated branch of metrology, with a huge range of parameters available. Each parameter contributes significantly towards the survival and mechanical properties of three-dimensional printed specimens. The purpose of this paper is to experimentally investigate the effect of surface roughness of three-dimensional printed dental implants and three-dimensional printed dogbone tensile samples under areal height parameters, amplitude parameters (average of ordinates), skewness parameters and mechanical properties. During the experiment, roughness values were analysed, and the results showed that the skewness parameter demonstrated a minimum value of 0.59%. The three-dimensional printed dental implant recorded the arithmetic mean deviation of the assessed profile with a 3.4-mm diameter at 43.23% and the three-dimensional printed dental implant with a 4.3-mm diameter at 26.18%. Samples with a complex geometry exhibited a higher roughness surface, which was the greatest difficulty of additive manufacturing when evaluating surface finish. The results show that when the ultimate tensile stress decreases from 968.35 to 955.25 MPa, the arithmetic mean deviation increases by 1.4%, and when ultimate tensile stress increases to 961.18 MPa, the arithmetic mean deviation increases by 0.6%. When the cycle decreases from 262,142 to 137,433, the arithmetic mean deviation shows that less than a 90.74% increase in the cycle is obtained. For the three-dimensional printed dental implants, the higher the surface roughness, the lower the mechanical properties, ultimately leading to decreased implant life and poor performance.

To Optimize Fiber Lay Length in OPGW Cables Used in Power Transmission Networks

In this paper, the optimal fiber length in optical ground wire (OPGW) cable during production process is determined. The results show that in OPGW cable, if the fiber stranding length is less than the maximum lay length, the ultimate tensile stress (UTS) percentage decreases, but if it is higher, it would increase the bending losses and uses more fiber length, which is economically not viable. The calculation results show that by determining the maximum fiber lay length, the UTS percentage of OPGW cable can be controlled for a desired value.

On the use of paper to facilitate recyclability of suspension packaging

Background of this research is suspension packaging: fragile goods are attached to a panel of cardboard by wrapping it in stretch film. The panel is then appropriately folded, and the whole thing is placed in a cardboard box of corresponding dimensions. The primary objective of this study is to identify paper types that might be used in future as a more sustainable alternative for stretch wrap film. The experimental methods that are utilized are basically variants of mechanical pulling tests on paper samples. Sample preparation and sample size are adopted from international standards, but displacement control is adopted to detect relevant stretchability properties. Some kraft papers show a high ultimate tensile stress and a moderate stretchability, mainly permanent stretch as expected. Although the ultimate tensile stress of paper from recycled fibers is lower, some of these paper grades show a considerable higher stretchability including a higher elastic stretch. It is concluded that both kraft paper and paper grades from recycled fibers may be applicable as a wrapping material for suspension packaging. Further experimental research is needed to identify appropriate wrapping parameters for each paper type.