Effect of Two-Stage Aging on Microstructure and Properties of Al-Mg-Si Alloys

The effects of two-stage aging on the microstructures, tensile properties and intergranular corrosion (IGC) sensitivity of Al-Mg-Si alloys were studied by tensile testing and IGC experiments and transmission electron microscope (TEM). The results show that the two-stage aging (180°C, 2h+160°C, 120h) can reduce the IGC sensitivity without decrease the tensile properties. The grain is distributed with high-density β′′ phases, and the grain boundary phases are spherical and intermittently distributed. The formation of the microstructure characteristic is due to the lower re-aging temperature, which results in a decline differences in the diffusion rate between the matrix and grain boundaries. As a result, the pre-precipitated phase can maintain a better strengthening effects due to the slower growth rate. The pre-precipitated phase of the grain boundary presents a spherical and intermittent distribution due to the fast coarsening speed.

Incorporation of Magnetite in Toughened PLA Nanocomposite: Tensile and Thermal Stability

In this study, liquid natural rubber (LNR) toughened polylactic acid (PLA) incorporated with magnetite (Fe3O4) nanocomposites were fabricated via melt-compounding in an internal mixer and followed by hot/cold pressing. The effects of ultrasonic treatment time (1-3 hours) and Fe3O4 (0.5-4.0 wt%) nanoparticles loading on tensile, morphology and thermal stability were investigated. Based on tensile testing results, the ultrasonication time of 1 hour was served as the most suitable treatment period to achieve the optimum distribution of Fe3O4 within PLA/LNR matrix. Among the investigated nanoparticles loading, 1 wt% Fe3O4 nanocomposite presented the highest tensile strength of 23.7 MPa, Young’s modulus of 1293.5 MPa and strain at break of 2.8%. SEM micrographs showed that the over-treated nanocomposites with 2-3 hours and over-high nanoparticles loading had resulted in the formation of clusters in the matrix. With increasing Fe3O4 loading, the decomposition of PLA/LNR nanocomposites was initiated earlier.

The Effect of Electrospun Dihydroartemisinin-Loaded Polycaprolactone/Collagen Scaffolds On Osteoblastic Differentiation of Human Adipose-Derived Stem Cells

In this study, Dihydroartemisinin (DHART)-loaded polycaprolactone collagen nanofibers (PCL/Col NFs) were constructed as effective biocompatible scaffolds through adjusting the proportions of hydrophobic/ hydrophilic polymers for enhanced osteoblastic differentiation of human adipose-derived stem cells (hADSCs). The designed NFs were characterized through FTIR, XRD, TGA, FE-SEM, and tensile testing. DHART-loaded PCL/Col electrospun NFs provide an ideal solution, with the potential of sustained drug release as well as inhibition of drug re-crystallization. Interestingly, inhibiting DHART re-crystallization can improve its bioavailability, providing a more effective therapeutic efficacy. Besides, the data set found through FE-SEM, MTT, PicoGreen, qPCR, and alkaline phosphatase (ALP) assays revealed the improved adhesion and proliferation rate of hADSCs cultured on PCL/Col/DHART (5%) NFs after 14 and 21 days of incubation. These findings confirmed the potential of the designed NF scaffolds for sustained/controlled release of DHART therapeutic molecules toward bone tissue regeneration and engineering.

Study of the anisotropy of carbon steel sheet by the tensile test

In test laboratories, the characteristics of the sheets shall be determined by the tensile test on specimens taken in the direction perpendicular to the rolling direction, and these characteristics shall be used as the date of entry into the process of calculating the parts made of the sheet. In the case of parts with special characteristics such as safety parts in the automotive industry, or for mechanically stressed parts in a certain direction, it is important to know precisely the values of the mechanical characteristics of the sheet in relation to the rolling direction, so as to ensure the required resistance. Also, in the case of stamped parts, their quality is all the better the lower the anisotropy. The paper presents the results of experimental research on the mechanical characteristics of the sheet DC04 with a thickness of 0,65 mm, determined by tensile testing on sets of 7 test specimens, taken every 15 degrees from the rolling direction.

Maximization of Tensile Strength of Aluminum 6061 Alloy T6 Grade Friction Welded Joints by Using the Desirability Function

Various joining techniques are consistently used in fabrications and maintenance applications of numerous parts in manufacturing industries. Typically, the friction welding technique acquired attention in joining of aluminum and its different alloys for very general structural usages in small to medium to large-scale manufacturing sectors. This is an experimental attempt to weld aluminum 6061 alloy T6 grade of 3mm thickness metal sheets. The hexagonal-shaped steel pin of grade H13 is used. The experiment is performed by using the Taguchi L9 approach, and nine welded specimens are prepared. The chosen factors are rotating speed of the tool, tilting angle, and feed. After the welding, the tensile testing is followed for the measurement of strength of the welded samples. The analysis suggested that the chosen working limits of feed and rotational speed is significant and having impacts on weld strength. The maximum strength is obtained as 212MPa when the ranges of above said factors are 560RPM, 0degree, and 20mm/min.

The Resistance Force of the Anterior Cruciate Ligament during Pull Probing Is Related to the Mechanical Property

There are various methods for reconstructing the anterior cruciate ligament (ACL) from other muscles or tendons. Initial tension of the reconstructed ACL is one of the key elements affecting postoperative outcomes. However, tension cannot be measured after graft fixation. The only intraoperative assessment is pull probing, which is performed by pulling joint soft tissues with the arthroscopic probe and can be measured quantitatively. Therefore, its value might be used as an alternative value for the mechanical property of the ACL. Using a probing device one author developed to measure the resistance force of soft tissues quantitatively while probing, we measured the resistance force of dissected ACLs and used tensile testing to investigate the correlation between the resistance force and the mechanical property of the ligaments. According to the results, when a certain amount of tension (strain; 16.6%) was applied, its mechanical properties were moderately correlated (r = 0.56 [p = 0.045]) with the probing force. Therefore, the tension of the reconstructed ACL after fixation under real ACL reconstruction surgery can be derived from the value of the probing device.