Materialwissenschaft und Werkstofftechnik最新文献

The polymer-based acetabular cup prosthesis, a vital component of hip replacement surgery, significantly contributes to the recovery of patients afflicted with osteoarthritic conditions. Nevertheless, the current clinical usage of polymer acetabular cup prostheses commonly encounters the challenge of balancing wear resistance and oxidation resistance, significantly impacting both their lifespan and patients′ quality of life. Consequently, researchers have persistently enhanced the attributes of polymer acetabular cup prosthetic materials. These enhancements, including irradiation and filler modifications, are intended to concurrently bolster both the wear and oxidation resistance of the prosthesis materials. This comprehensive approach aims to address wear-associated clinical complications like osteolysis and oxidative brittleness, ultimately extending their in vivo service life. For this reason, this paper retrospectively discusses the progress of research on the modification of polymer acetabular cup prosthesis materials for high wear and oxidation resistance and explores potential design methods for optimising artificial acetabular cup materials, with a view to providing new ideas for extending the service life of artificial joint implants.

As the important component to guide the airflow in the classifier, installation position of the guide vane determines the width of the classification annular region and influences the flow field distribution. The influence of the guide vane positioning on the flow field in the annular region is analyzed through numerical simulation. The simulation results show the tangential velocities near the inner edge of the guide vanes increase, and the tangential velocity gradient decreases with decrease of the width of the annular region. The increases of turbulent dissipation rate near the guide vanes are beneficial to powder dispersion. However, the increases of turbulent dissipation rate near the rotor cage aren′t conducive to uniformity of the flow field. In case of the narrow annular region, the cut size gradually increases when the width of the annular region increases. However, when the width of the annular region continues to increase, the particle′s residence time become long, and the solid concentration increases significantly to increase the probability of particle aggregation. The reasonable range of the installation diameter of the guide vane in the classifier is between 504 mm and 524 mm.

Temperature control of mould surfaces is of high relevance for part quality in moulding processes. Due to highly dynamic heating behaviour, heating elements applied by thermal spraying can be an alternative to existing tempering methods. To ensure the feasibility of these heating coatings on industry-relevant moulds, the coating system needs to be applied onto more demanding non-flat geometries. For this purpose, the spray angle of the plasma spraying process is varied during the application of the titanium oxide/chromium oxide heating coating and the insulating aluminium oxide coating. Subsequently, the results are related to application-oriented cavity shapes. Spray angle deviations from the optimal perpendicular angle are leading to decreasing dielectric strength of the coating system and an increase of the electrical resistivity. Additionally, the application efficiency reduces with the spray angle variation. Knowledge of the spray angle's influence on coating properties can help to coat more demanding shapes, including free formed surfaces or corners.

Since the solidification structure of metals cast by conventional mold casting often has porosity defect, the combination of low voltage pulsed magnetic field and thermally controlled solidification was used to solve this defect. The combination method is called magnetic-thermal coordinated control solidification. Pulsed magnetic field stirring can refine equiaxed grains, and the thermally controlled solidification method can eliminate the concentrated shrinkage cavity and reduce the dispersed shrinkage porosity. Thus, a superalloy K4169 with fine equiaxed grains, low content of dispersed shrinkage porosity and without concentrated shrinkage cavity defect is fabricated by magnetic-thermal coordinated control solidification.

Aerospace and automotive industries, among others, utilize reinforced aluminium metal matrix composite materials extensively. Aluminium alloy 5052 matrix was reinforced with tungsten carbide and titanium dioxide particulate reinforcements by varying their weight fractions, to fabricate the hybrid composites. The melt-stir casting route was used to process the materials, and their characteristics were determined by measuring Vickers microhardness, tensile strength and peak elongation. The cost-effectiveness and productivity of the melt-stir casting route led to its selection. Investigations were carried out to assess how reinforcement particles were mixed into the aluminium alloy matrix using scanning electron microscopy and energy-dispersive x-ray analysis. The microstructure of aluminium alloy 5052 showed a distinct homogenous structural integrity. Adding tungsten carbide and titanium dioxide particles to aluminium alloy 5052 led to a 6.57 % rise in the Vickers microhardness value. The tensile strength of the hybrid composites made of aluminium, tungsten carbide, and titanium dioxide increased by as much as 8.7 %. The findings demonstrated that all of the hybrid composites failed due to particle fracture and ductile fracture in the case of the as-cast aluminium alloy 5052.

Hailstorms today have the potential to damage almost every object in their path. Efforts are been made to prevent hailstorms, which can be quite severe. However, a completely successful result has not been achieved. Automobiles are the ones most damaged by hailstorms. In order to protect automobiles from this damage, various protective fabrics have been studied on and patents have been obtained. Spacer fabrics are one of the materials that have the potential to be used as protectors. In this study, an experimental device that can test the performance of spacer fabrics against hail and simulate hail damage has been designed and manufactured. At the same time, suggestions for the preparation of artificial hail grains that can be used in different studies are presented. With 25 mm and 30 mm diameter artificial hail grains, experiments were carried out on spacer fabrics of different thicknesses with the same weave structure. The same diameters of artificial hail grains were also tested without covering and the amount of damage in all experiments was measured. As a result, it was compared which fabric provided how much protection against artificial hailstones of different diameters.

The present paper describes the fabrication and wear behaviour of CaO and MgO added stabilized zirconia (ZrO₂) ceramics produced by powder metallurgy method were examined and modelling with artificial neural networks was studied using the experimental data obtained. CaO/MgO added stabilized zirconia ceramics were fabricated by using a combined method of ball milling, cold pressing - cold isostatic pressing and sintering. CaO and MgO in different amounts (0–8 %mole) were mixed with zirconia. These mixtures were prepared by mechanical alloying method. The green compacts were sintered at 1600 °C. The wear experimental results obtained were converted into data suitable for modelling with artificial neural networks. Wear Load, wear time, CaO and MgO data were used as artificial neural networks input variables. The amount of wear according to the pressing method was taken as the output variables of artificial neural networks. An artificial neural networks was established for the prediction of wear properties of zirconia pressed using the adaptive neuro fuzzy inference systems (ANFIS) learning technique. As a result, a high R² value of 0.9187 for cold pressing samples and 0,9449 for cold isostatic pressing samples was achieved based on the approach of comparing the success of the model with the test data set and the result produced.

In the current study, dental nanocomposite reinforced with silanized silicon dioxide nanoparticles was developed. The silicon dioxide nanoparticles were varied from 0 to 30 weight-%. Polymer resin of bisphenol A-glycidyl methacrylate/ triethylene glycol dimethacrylate (BisGMA/TEGDMA) was used along with camphorquinone and ethyl 4-(dimethylamino) benzoate as polymerization initiator and accelerator respectively. The role of silicon dioxide nanoparticles in mechanical and viscoelastic properties of dental composites was evaluated. Physical properties like void content and water sorption were increased by 10 % and 25 % respectively. However, mechanical and viscoelastic properties were improved with the addition of silicon dioxide nanoparticles. Data were analyzed statistically with one-way analysis of variance (ANOVA) and post hoc Tukey′s HSD test (α<0.05). The incorporation of 10 weight-% of silicon dioxide nanoparticles increased the micro-hardness by 126.1 %, compressive strength by 7.6 % and flexural strength by 28.8 %. The storage modulus was increased by 37 % and loss modulus was decreased by 1 % with the introduction of 10 weight-% of silicon dioxide nanoparticles.

In this paper, titanium-aluminum based alloy was successfully prepared by introducing titanium powders using powder metallurgy. The experimental results indicated that the microstructures of alloys were composed of the new trititanium-aluminium layers skeleton and the γ+α₂ phases filler, which exhibited excellent compression properties. The compressive strength of the titanium-aluminum based alloy (10 wt.% titanium) were 509.9 MPa, higher than monolithic Ti-48Al-2Cr-2Nb alloy at 800 °C and 1×10⁻⁴ s⁻¹. The deformation mechanism is mainly referred to the motion and rotation of γ+α₂ areas and dynamic recrystallization. The γ+α₂ areas were surrounded by complete new trititanium-aluminium layers, which is beneficial to dislocation pile-up, cross and tangle at grain boundaries, resulting in high strength. Besides, the dislocation pile of γ, α₂ phase, and twins in γ phases, are the deformation mechanism in alloys.

In this study, a small-sized shredder machine equipped with spiral oriented double-edged rotating and fixed blades was utilized to shred high-density polyethylene (HDPE) waste. The performance of the shredder machine was determined based on the recycling and shredding efficiency, the percentage of retention, and the wear of its rotating and fixed blades. The wear of the blades was examined using an optical microscope, a scanning electron microscope, an energy dispersive x-ray, and an x-ray diffraction. High recycling (~95 %–98 %) and shredding (~66 %–70 %) efficiency, and low percentage of retention (~1.2 %–4.1 %) indicated a reliable performance of the shredder machine. The rotating blade exhibited higher wear at the back end, compared to the front end for the fixed blade. The wear of the blades was due to scratching and edge chipping. Formation of iron oxides during shredding did not cause significant changes in the hardness of the blades. Based on the evaluation, cost-effective and time saving maintenance of the shredder blades could be achieved by gradual maintenance starting from the blade exhibited high wear.