Materialwissenschaft und Werkstofftechnik最新文献

The focus of this study, using results obtained with hollow specimens of the alloy Al 2024 T3 (AlCuMg2 T3) with a one-sided bore, was to determine if, under multiaxial loading, the fatigue strength in a notch with a uniaxial stress state can simply be assessed without the application of any multiaxial strength hypothesis. In the fatigue critical location, the bore edge, only a superimposition of normal stress components, resulting from axial loading or/and torsion, occurs. In the case of out-of-phase loading, the resulting local uniaxial stress is even lower than the stress under in-phase loading and leads to an increase of fatigue life to crack initiation under the non-proportional loading, which is not observed in the case of multiaxial stressing/straining of the material itself. As the local stress state in the crack initiation site is uniaxial, the application of a multiaxial strength hypothesis, for the failure criterion of crack initiation (l=0.2 mm), is not necessary. Furthermore, the benefit of non-homogenous stress distributions, which allow locally higher stresses than the levels given by the Woehler-line for unnotched specimens, was underlined by considering highly-stressed, material-volume-related support factors.

This research investigates the structural performance and failure mechanisms of beam-column joints reinforced with aramid fiber-reinforced polymer to bolster the durability and seismic resilience of concrete structures. It meticulously selects and proportions materials such as ordinary Portland cement Grade 53 cement, fine and coarse aggregates meeting IS: 383–1970 standards, and water conforming to IS: 456–2000 specifications. Tests confirm the high quality of ordinary Portland cement, crucial for optimal beam-column joint performance, while carbon fiber-reinforced polymer enhances structural integrity with its lightweight composition and substantial tensile strength (3800 MPa–4200 MPa). Failure analysis reveals that non-aramid fiber reinforced polymer wrapped beam-column joint specimens predominantly failed due to concrete crushing, whereas aramid fiber-reinforced polymer-wrapped specimens failed due to fracture in the aramid fiber-reinforced polymer composite, emphasizing stress concentration areas. This study underscores the pivotal role of stress distribution in failure mechanisms and underscores the significance of robust reinforcement design in bolstering structural resilience. These insights advance retrofitting strategies and reinforce techniques aimed at enhancing the longevity and seismic resistance of concrete structures.

This present work concerns the effect of ternary addition of non-metallic and diamagnetic silicon on the metastable solubility of the immiscible silver-cobalt system during the course of ball milling, annealing of the ball milled samples and the corresponding magnetic properties. It should be noted that silicon has a smaller goldsmidt radius (111 pm) than silver (144 pm) and silicon⁺⁴ has more valence electrons than silver⁺¹. Keeping the objectives of the current study in mind, silicon may thus be considered as an option for ternary addition, in contrast to metallic components. An attempt has been made to examine the phase changes that occurred in the 50 silver-40 cobalt-10 silicon (atom percent) system during ball milling and the subsequent isothermal annealing of the ball milled product. Phase evolution during mechanical alloying and isothermal annealing is identified by means of x-ray diffraction, differential thermal analysis, high resolution transmission electron microscopy and magnetic measurements. The addition of silicon facilitates cobalt‘s formation of a metastable alloy with copper after 50 hours of ball milling. Annealing significantly improves the magnetic characteristics of materials that have been ball milled; the optimal combination of magnetic properties was obtained after an hour of annealing at 550 °C.

This study used electroless nickel-immersion gold surface finish. The lead free solder used are tin-silver-copper 305 and tin-silver-copper 307 solder alloys. The difference in copper composition will affect the intermetallic compound′s microstructure after the laser soldering process. The intermetallic compound formation analysis reveals that only (Cu, Ni)₆Sn₅ was observed at the solder joint interface for both solders after laser soldering. The grain microstructure of tin-silver-copper 305 formed is rounded-shaped and bar-shaped, while tin-silver-copper 307 shapes are oval-shaped and flake-like. However, for cross-sectioned analysis, the intermetallic compound grain microstructure formed at the solder joint formation was (Ni, Cu)₃Sn₄ and (Cu, Ni)₆Sn₅ presented in dendrite-like and scale-like shapes. This result shows that copper content in solder composition is directly affected the intermetallic compound grain microstructure. When exposed to the ageing process, the intermetallic compound thickness will increase directly with ageing time. The intermetallic compound thickness for tin-silver-copper 305 was increased from 0.98 μm to 8.34 μm while tin-silver-copper 307 was increased from 1.54 μm to 8.76 μm. The result also shows that nano-sized of Ag₃Sn grain particle was formed on the intermetallic compound surface after an ageing process for both samples, tin-silver-copper 305 and tin-silver-copper 307.

In this investigation hot rolled steel bars of 1.24 weight % carbon steel are subjected to incomplete austenitization based cyclic quenching treatment. Each cycle consists of inserting the specimen in an electric resistance furnace at a temperature of 894 °C and holding for a short duration (6 minutes), followed by oil quenching to the room temperature. Such a typical thermal cycling results in the evolution of a novel microstructure that comprises of large clusters and blocks of cementite in a matrix of martensite after 3 and 4 cycles. Accordingly, a significantly high hardness (7.13 GPa) is achieved on execution of 3 cycles which envisages a new pathway of incomplete austenitization based cyclic quenching treatment for development of new-generation plain carbon hypereutectoid tool steel.

In this study, cryogenic-temperature formal machining technique was used to process solution-treated aluminum 7075 alloys, the mechanical properties, morphology, and microstructure of machined surface and produced chips are investigated. Results show machining temperature has a huge influence on chip and machined surface morphology, cryogenic-temperature machining chips and machined surfaces possess better surface integrity, chips are continuous and smoother, and machined surfaces are flatter. In contrast, room-temperature formal machining chips exhibit serrated cracks on their free surface and the machined surface produces more serious scaly spines phenomenon. Both cryogenic-temperature and room-temperature samples experience severe deformation, cryogenic-temperature machining alumium 7075 alloys max microhardness has enhanced from 98 HV 0.1 to 174 HV 0.1, and cryogenic-temperature samples’ microhardness is higher than corresponding room-temperature samples’ microhardness among all machining parameters. Cryogenic-temperature can effectively suppress dynamic recovery thus chips could store more dislocations and then possess smaller ultrafine-grained structures, accounting for higher microhardness. Besides cryogenic-temperature inhibits precipitation of solute cluster and second phase particles and plays a lubrication effect at tool-chip interface, thus cryogenic-temperature machining aluminum 7075 alloys could obtain superior machined surface quality/chip morphology to improve processability. (*: Equal contributi)

High energy consumption and poor processing quality are common problems in wood sawing. To address these issues, in this article, specific cutting energy and surface roughness were investigated with saw blade speed as control variables. Analysing the effect of parameters on specific cutting energy and surface roughness. The sawing parameters were optimised with the objectives of minimum specific cutting energy and minimum surface roughness. The findings indicate that specific cutting energy and surface roughness reduction with increasing rake angle; specific cutting energy and surface roughness decrease with increasing spindle speed; specific cutting energy decreases and surface roughness increases with increasing feed rate. ANOVA analysis reveals that sawing speed (n) has the most significant impact on specific cutting energy during oak cutting. The optimal solution derived from TOPSIS suggests a specific cutting energy of 2E7 J/m³ and a surface roughness of 1.758 μm. The innovation of this paper is the study of the specific cutting energy and the optimisation of parameters. These findings provide valuable theoretical and practical guidance for enhancing the efficiency and quality of oak processing while minimizing energy consumption.