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Explicit correlations were established between surface integrity (SI) characteristics (roughness, microhardness, residual stresses) obtained via surface cold working (SCW) and bending fatigue limit of chromium-nickel austenitic stainless steels (CNASS). The SCW was implemented via hardening DB, and the treated CNASS was AISI 304. Based on the correlations obtained, a simplified optimization approach to achieving the maximum fatigue limit without carrying out fatigue tests was developed. Five roughness parameters that are functionally significant indicators of fatigue behavior, microhardness, and surface residual axial and hoop stresses form the vector of objective functions. The governing factors are the burnishing force and the number of passes. The fatigue limit was obtained by the accelerated Locati’s method. The SI models and the fatigue limit were obtained by a planned experiment and regression analyses. The correlations between SI characteristics and the fatigue limit were obtained by eliminating the variables in the corresponding pairs of models. The change trends of the microhardness and fatigue limit were found to be identical, i.e., the fatigue limit of CNASS can be controlled via inexpensively measured SI characteristics such as roughness parameters and surface microhardness. In other words, the essence of the proposed approach is that any static cold working process can be optimized without carrying out fatigue tests by choosing these SI characteristics as objective functions and seeking a compromise optimal solution that simultaneously achieves high values of the microhardness and skewness and a low value of the roughness parameter Ra. Given the explicit correlation between the microhardness and the fatigue limit, the compromise optimal solution maximizes the fatigue limit while satisfying the particular roughness requirements. The multi-objective optimization performed and comparisons made prove the effectiveness of the proposed approach.

V- Ti alloys are promising alternatives to Nb for the construction of superconducting solenoids that produce high magnetic fields. The critical current density ( J C ), which quantifies the capacity of a superconductor to carry large dissipationless current, increases in the V-Ti alloys with the addition of Ce. Here, the effects of successive cold working and annealing on the electrical resistivity, J C , and microstructure of the V 0.59 Ti 0.40 Ce 0.01 alloy are studied. The J C is the maximum after the second cold rolling. Annealing at 650 ∘ C is found to nucleate and grow the α -phase which is detrimental to J C , whereas the precipitation of the α ′ -phase is found to improve the J C .

The behavior of the lug joint with interference-fit fastener subjected to axial load which represents a moving boundary value problem is addressed in the article. The variation of contact stresses between the pin and the lug-hole is non-linear and is studied by partially linearizing the non-equilibrium equations. The inverse formulation is employed to estimate the loss of contact of the pin from the lug hole. The operating load levels corresponding to these pin separation regions determine the critical locations of high-stress fields. The lug-hole is pre-stressed by the cold-working which creates the plastic wake around the lug-hole periphery and reduces the stress levels which is beneficial in the retardation of crack growth at critical locations and enhances the performance of the lug joint. Three-dimensional numerical analysis is performed wherein the novel and effective approach in performing the cold-working of lug-hole, insertion of the interference-fit pin and applying pin load is defined in displacement-controlled time steps. The loss of contact of the pin and the cycles to failure is computed using an in-house Python script. The methodology and findings assist in forecasting failure and can be used as a reference for similar fastener problems in engineering applications.

Development of high temperature and corrosion-resistant materials is one of the key issues for the deployment of advanced nuclear reactors and also to accommodate the problem that occurred in the conventional reactor as the lesson-learned from Fukushima Daiichi nuclear reactor power plant accident. One of the high performance materials for that purpose is austenitic stainless steel such as AISI 316L that widely used for power plant. In this study we investigate the characteristics of AISI 316L austenitic phase transformation if cold working is applied. In general, during the cold working process the mechanical characteristic and the phase of the austenitic steel will change. It is expected that the characteristic of AISI 316L austenitic steel will be improved by optimum cold working mechanism. Cold working of AISI 316L austenitic steel at various percentage reduction of 5%, 15%, 25% and 38% have been done. Afterward, the sample was characterized using X-Ray Diffraction and Optical Microscope to analyze the microstructure characteristics and phase transformation. The results showed that the phase transformation in AISI 316L austenitic steel occurred from austenite – gamma (FCC: Face-Centered Cubic lattice) to martensite – alpha prime (BCC: Body Centered Cubic lattice). The percentage of martensite phase was increasingly growth related to the increasing of the percentage of cold working value i.e. 8.3%, 21.6%, 29.6% and 37.1%, respectively. The hardness of AISI 316L austenitic steel increased with the increasing of the cold working percentage. AISI 316L double phases which covers of austenite-martensite intermix phase structure with higher hardness mechanical properties has been successfully developed.

Due to its exceptional mechanical properties, such as its high strength and hardness, high-carbon steel is utilised extensively in various industries. The way of behaving of high-carbon steel is impacted by various handling strategies, for example, hot working and cold working, which can influence its microstructure and mechanical properties. The review aims to Study the behaviour of high-carbon steel material in hot and cold working media. Also, to look at the effects of hot and cold working on the macrostructure of the high carbon steel and the mechanical properties such as hardness, comprehension, impact tests, tensile stress and strain analysis. From the review, the hot and cold working processes, such as bending, rolling, and squeezing, for the result obtained from the hardness test shows the hardness value for hot rolling is higher than that of cold rolling (it is generally expected for hardness obtained from cold rolling should be higher than that from hot rolling) this may be due to the variations in the rolling parameters. While the hardness obtained from cold bending s higher than that from hot bending, and the hardness value obtained from hot squeezing is higher than that of cold squeezing. The results for hot bending of high-carbon steel show improved ductility and reduced risk of cracking compared to cold bending. This viable finding is highly significant to manufacturers to enable the production of sustainable materials for structural applications.

Lug joints are preferred joineries for transferring heavy loads to parent components in aerospace vehicles. They experience corrosion due to environmental conditions, improper surface finishes and rubbing displacement between the pin and lug-hole. This causes damage of different sizes and shapes near the lug-hole. Stiffness degradation due to corrosion-induced damage is modelled as a through-pit at one of the identified critical locations through stress analysis. The effect of this pit on fatigue crack initiation life is estimated. Lug-hole is pre-stressed by cold-working and the benefits of inducing plastic wake on the intended performance of the lug joint during the damages due to corrosion are brought out and compared with non-cold-worked lug-hole. Numerical analysis is performed on this lug joint with press-fit. The results obtained highlight the benefits of cold-working and the methodology can be extended to damage growth and analyse the effect of surface treatments for better structural integrity of components of aerospace vehicles.

An new insight into the relationship between the C-Cr Ratio and carbides, mechanical property Cr Alloyed of cold working die Steel were investigated by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), rockwell hardness and impact toughness tests. The ‘C-Cr ratio’ and ‘Cr equivalent E Cr ‘ parameters were introduced to characterize the carbide characteristics and mechanical properties. The results show that the precipitation temperature of M 7 C 3 eutectic carbides grows linearly with E Cr when the E Cr value is less than about 22, and the precipitation temperature increases significantly when the E Cr value exceeds 22, and the growth curve takes a plateau turn. The precipitation temperature of MC carbides decreases approximately linearly with E Cr value, and the precipitation of MC eutectic carbides will be completely suppressed when the E Cr value exceeds 19. The content of eutectic carbides in the as-cast organization is more, the shape is more complex and the size is larger. The ratio of Cr and Fe content in the composition of M 7 C 3 eutectic carbides is linearly related to the Cr-C ratio; the content of carbides in the steel after forging and the E Cr value are basically linear. The average particle size and the average length of longitudinal carbides after forging are basically proportional to the E Cr value. The average particle size of longitudinal carbides after forging is greater than 4 μ m and the E Cr value are basically linear; when the Cr content is greater than 4%, the quenching peak hardness of steel and the C / Cr have a good linear relationship; as the E Cr value gradually increases, the impact toughness of steel gradually decreases. These results are important not only for understanding the strengthening mechanisms of die steel, but also for the composition design and carbide control of cold working die steel.

High-Mn austenitic steels have been recently developed for a storage or transportation application of liquefied natural gas (LNG) in cryogenic fields. Since the structural materials are subjected to extremely low temperature, it requires excellent mechanical properties such as high toughness strength. In case of high-Mn steels, twinning deformation during the cold-working process is known to increase strength yet may cause embrittlement of heavy deformed twin and anisotropic properties. In this study, a recrystallization process through appropriate annealing heat treatments after cold-working was applied to improve the impact toughness for high-Mn austenitic steels. Microstructure and mechanical properties were performed to evaluate the influence of cold-worked and annealed high-Mn austenitic steels. Mechanical properties, such as strength and impact toughness, were investigated by tensile and Charpy impact tests. The relationship between strength and impact toughness was determined by microstructure analysis such as the degree of recrystallization and grain refinement. Consequently, both elongation and toughness were significantly increased after cold-working and subsequent annealing at 1000 °C as compared to the as-received (hot-rolled) specimen. The cold-worked high-Mn steel was completely recrystallized at 1000 °C and showed a homogeneous micro-structure with high-angle grain boundaries.

In this study, we propose a rapid plasma-assisted nitriding process using H2/N2 mixture gas in an atmospheric pressure plasma jet (APPJ) system to treat the surface of SKD11 cold-working steel in order to increase its surface hardness. The generated NH radicals in the plasma region are used to implement an ion-bombardment for nitriding the tempered martensite structure of SKD11 within 18 min to form the functional nitride layer with an increased microhardness around 1095 HV0.3. Higher ratios of H/E and H3/E2 were obtained for the values of 4.514 × 10−2 and 2.244 × 10−2, referring to a higher deformation resistance as compared with the pristine sample. After multi-cycling impact tests, smaller and shallower impact craters with less surface oxidation on plasma-treated SKD11 were distinctly proven to have the higher impact wear resistance. Therefore, the atmospheric pressure plasma nitriding process can enable a rapid thermochemical nitriding process to form a protective layer with unique advantages that increase the deformation-resistance and impact-resistance, improving the lifetime of SKD11 tool steel as die materials.

Cold-formed structures are a separate type of metal structures and require more complex mathematical models in comparison with massive profiles. The development of main theories was described. A new type of buckling is also taken into account - warping, which is characteristic only of cold-formed bars.