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This work is concerned with forming, specifically deep drawing, and its influence on the micro-mechanical properties of sheet metal. In practice, there are several applications in which fractions can occur due to weak spots in the deep-drawn sheet metal, especially after long-term use. The deep drawing process was carried out on BUP–600 machines using the LHD (Limiting Dome Height) method, which uses a forming tool with a diameter of 100 mm and bead groove. Sheet metals X8CrMnNi19-6-3 (1.4376) with thicknesses of 1, 1.5, and 3 mm were selected for this process. To study the effect of a lubricant on the formability of the sheet metal, deep drawing without and with a lubricant was compared. An FEM analysis was conducted to identify critical points in the deep drawing process, and the results were later compared with real results. The analysis was conducted using the AutoForm program. The micro-mechanical properties of these points were subsequently examined. The specified points on the formed part showed significant differences in their micro-mechanical properties, suggesting a higher strength but also less resistance to fractures. The difference in micro-mechanical properties (indentation and Vickers hardness) in points that were not deep-drawn and points located in critical areas was up to 86%. Significant changes in behavior were found in the indentation modulus and plastic/elastic deformation work as well. This study demonstrates the significant effect of the use of a lubricant in achieving the deep drawing of the sheet metal. The application of a lubricant resulted in a 33% increase in drawing range compared to drawing without lubrication. This study has a significant influence on the deep drawing of sheet metals in practice, showing the fundamental influence of the lubricant on the drawing process and also showing the problem of critical points that need to be eliminated. [ABSTRACT FROM AUTHOR]

Hot forming is an effective approach for improving the formability of ultrathin metal sheets, such as those made of stainless steel and pure titanium. However, the increased friction coefficient between the tool and the high-temperature metal sheet negatively affects material flow during hot forming, potentially resulting in severe local thinning or even cracking. This study explores the frictional behavior of 0.1 mm thick ferritic stainless steel (FSS) and commercially pure titanium (CP-Ti) sheets at elevated temperatures. A friction testing apparatus was developed to measure the friction coefficients of these metal sheets from room temperature (25 °C) up to 600 °C. The friction coefficient of the FSS sheet increased monotonically with temperature, whereas that of the CP-Ti sheet first increased and then decreased. Post-friction testing microscopic examination demonstrated that built-up edges formed on the surfaces of the friction blocks when rubbed against the stainless steel, contributing to the higher friction coefficients. This study provides a foundation for understanding frictional behavior during the hot forming of ultrathin metal sheets. [ABSTRACT FROM AUTHOR]

Generally, when fabricating porous filters using metal powder, about 1 to 2 wt% of a binder is added to increase the formability of the metal powder. If the binder is not completely removed through a debinding and sintering process, however it can cause defects such as discoloration and the generation of fine particles. In this study, a study was conducted to fabricate a plate-type porous stainless steel powder filter with a different pore structure without the use of a biner. First, the metal powder is charged into a ceramic mold to form a plate-shaped powder filter, and then covered with a ceramic top plate. In order to observe the pore properties according to the pressure, the unpressurized specimen and the specimen pressurized with a pressure of 30 MPa were then sintered at 1050? for one hour in a high vacuum atmosphere furnace. The microstructure of the sintered plate-shaped powder filter was observed through an optical microscope and in order to analyze its pore properties as a filter, gas permeability and porosity were measured using a capillary flow porometer and Archimedes' law. [ABSTRACT FROM AUTHOR]

Sheet metal forming is one of the key processes for the automotive sector to be considered. Sheet metal formability is being tested as received, joining them with different welding/joining processes (i.e., tailored blanks) and making them as sandwich forms to reduce the total weight of the body. These sandwich formations of sheets are an advanced method by incorporating PVC/polymer sheets in between metal sheets with a suitable binder. The present work has investigated the formability of AA5052-PVC-AA5052 (Al-PVC-Al) sandwich sheets by considering the sheet rolling direction as a parameter. The mechanical properties of base metal and sandwich sheets were evaluated by conducting the uniaxial tensile tests. For forming behaviour of Al-PVC-Al sandwich sheets, in-plane plane stretching tests were performed on the universal tensile testing machine. From the results, it has been observed that 0-degree and 90-degree rolling direction of AA5052 sheets provided almost similar forming behaviour where the 45-degree rolling direction showed less formability. The limit strains (by which the forming limit curve has been developed and the safe and failure zones are separated) are 0.043, 0.038, and 0.043 of 0°, 45°, and 90°, respectively. Considering 0°-P-90°, 90°-P-90, 0°-P-45°, 0°-P-90°, and 45°-P-45° sandwich sheets with their corresponding limit strains of 0.060, 0.058,0.057, 0.052, and 0.050, a better formability is seen in 0°-P-90° sandwich, followed by 90°-P-90, 0°-P-45°, 0°-P-90°, and 45°-P-45°. The improvement in the formability is calculated as 28.33%, 25.86%, and 24.0% in comparison with the base metal in 0-degree, 90-degree, and 45-degree rolling directions and 0°-P-90°, 90°-P-90, and 45°-P-45° sandwich sheets. [ABSTRACT FROM AUTHOR]

Friction is one of the main phenomena accompanying sheet metal forming methods, affecting the surface quality of products and the formability of the sheet metal. The most basic and cheapest way to reduce friction is to use lubricants, which should ensure the highest lubrication efficiency and at the same time be environmentally friendly. Due to the trend towards sustainable production, vegetable oils have been used in research as an alternative to petroleum-based lubricants. The analysis of friction in sheet metal forming requires an appropriate tribotester simulating the friction conditions in a specific area of the sheet metal being formed. Research has used a special strip drawing tribometer, enabling the determination the value of the coefficient of friction in the blankholder zone in the deep drawing process. Quantitative analysis of the friction phenomenon is necessary at the stage of designing the technological process and selecting technological parameters, including blankholder pressure. This article presents the results of friction testing of 1.0338 (DC04) steel sheets using a strip drawing test. The experimental tests involved pulling a strip of sheet metal between two countersamples with a rounded surface. The tests were carried out on countersamples with different levels of roughness for the range of contact pressures occurring in the blankholder zone in the deep drawing process (1.7–5 MPa). The values of the coefficient of friction determined under dry friction conditions were compared with the results for edible (corn, sunflower and rapeseed) and non-edible (Moringa, Karanja) vegetable lubricants. The tested oils are the most commonly used vegetable-based biolubricants in metal forming operations. Multi-layer artificial neural networks were used to determine the relationship between the value of the contact pressure, the roughness of the countersamples, the oil viscosity and density, and the value of the coefficient of friction. Rapeseed oil provided the best lubrication efficiency during friction testing for all of the tested samples, with an average surface roughness of Sa 0.44–1.34 μm. At the same time, as the roughness of the countersamples increased, a decrease in lubrication efficiency was observed. The lowest root mean squared error value was observed for the MLP-4-8-1 network trained with the quasi-Newton algorithm. Most of the analysed networks with different architectures trained using the various algorithms showed that the kinematic viscosity of the oil was the most important aspect in assessing the friction of the sheets tested. The influence of kinematic viscosity on the value of the coefficient of friction is strongly dependent on the surface roughness of the countersamples. [ABSTRACT FROM AUTHOR]

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In this research, the improvement in sheet metal formability obtained through the utilization of a mineral grease in solid‐oil‐type (SMG) pressure medium in the hydrodynamic deep drawing process assisted by radial pressure is investigated by experiments and finite‐element method (FEM) simulations on flat‐bottom cups realized with pure copper and DIN 1.0338 steel. To determine the process parameters ranges, an FEM model is developed in ABAQUS/Explicit and validated against experimental results. Afterward, experiments are carried out using two pressure mediums with different viscosities, i.e., water and SMG. Considering the results relevant for both sheet materials, the SMG medium allows an average reduction of the sheet metal thinning of 15% and 10% on the corner edges while also granting a negligible thickness variation on the cup walls. In contrast, the higher viscosity of the SMG, in comparison to the water medium, also results in an average 16% increase in the forming force when compared to the water pressure medium. [ABSTRACT FROM AUTHOR]

Incremental Sheet metal Forming (ISF) Process is a suitable process which helps to produce various parts used in automotive sector by rapid prototyping. This method of producing a prototype helps industry in reducing the production cost. In ISF process, a final product is evolved through local deformation of the sheet metal made by the tool. Usually better formability is obtained when the tool makes a better contact with the sheet metal throughout the process. Improved formability elevates dimensional accuracy of the product, thus increases the market value of the product. A new tool with multiple ball ends capable of making multiple mating points over sheet metal was used in this research to enhance the efficiency of formability and surface finish. Ability of the new Multi-Point Incremental Forming Tool (MPIF) was investigated and compared to the existing Single Point Forming Tool (SPIF) based on the formability and surface finish. Forming Limit Diagram (FLD), Strain Distribution (SD) and Scanning Electron Microscope (SEM) were used to examine the formability of the sheet metal. The SEM & 3D-Surface roughness profilometer were used to observe the sheet metals surface finish. In addition to these experimental techniques a simulation results were also used to predict the stress and strain rate during forming process. The experimentation and simulation outcome shows that the MPIF provides superior formability and surface finish. [ABSTRACT FROM AUTHOR]

Pumping is the preferred placement method for concrete. The pumping process influences fresh properties of concrete. Competent producers handle these issues when composing the mix design. However, sudden changes in workability sometimes appear, both in the form of increased and decreased workability. Both changes might be handled on-site. However, even the situations that are sufficiently handled, cause delays and extra costs. Sometimes the final result's quality is compromised, resulting in repairs and economic compensation claims. The extent and causes of incidents with sudden changes in workability are still to be investigated. It is suggested that around 1 100 000 m3 or 30% of concrete experience sudden change in workability annually in Norway, and that 200 000 kg of chemical admixtures is used on-site. It appears that the most relevant cause is to find within variations in the fine aggregate. Increase in workability might also be caused by lack of compatibility between superplasticiser and binding materials in low-carbon concrete, enhanced by the extra mixing process caused by the pumping process. To approach these questions, the Quality Assessment system of a medium-sized Norwegian concrete producer has been investigated. It comprises documentation of 1 500 000 m3 of concrete, over 10 years. [ABSTRACT FROM AUTHOR]

The addition or substitution of various gel materials in cement-based composites has been proven to be an effective approach in enhancing the performance of concrete. Current research focuses mainly on enhancing the toughness of concrete, but lacks discussion on the performance of alternative gel materials. Therefore, this study aims to explore the effects of partially substituting cement with fly ash and slag powder as gel materials, while incorporating a high volume fraction of micro-steel fibers (6%), on the workability and mechanical properties of self-compacting concrete. By means of rigorous experimental investigation and meticulous analysis, we comprehensively assessed the workability characteristics of self-compacting concrete, encompassing critical aspects such as filling ability, cohesion, and permeability. Additionally, we conducted an extensive evaluation of the mechanical attributes of self-compacting concrete, encompassing vital parameters, such as compressive strength, axial compressive strength, splitting tensile strength, and flexural strength. Last but not least, through a holistic integration of workability and mechanical properties, we conducted a comprehensive performance evaluation of self-compacting concrete incorporating a synergistic blend of fly ash, slag powder, and micro steel fibers. The experimental results indicate that the composite addition of fly ash and slag powder in self-compacting concrete, while compatible with up to 6% micro-steel fibers, leads to a decrease in concrete workability and an increase in cohesiveness due to the addition of micro-steel fibers. Moreover, fly ash predominantly influences the tensile properties of concrete, while the addition of slag powder significantly affects the compressive and flexural properties of concrete. Additionally, the addition of micro-steel fibers significantly improves the overall mechanical properties of concrete. [ABSTRACT FROM AUTHOR]

An accurate description of the formability and failure behavior of sheet metal materials is essential for an optimal forming process design. In this respect, the forming limit curve (FLC) based on the Nakajima test, which is determined in accordance with DIN EN ISO 12004-2, is a wide-spread procedure for evaluating the formability of sheet metal materials. Thereby the FLC is affected by influences originating from intrinsic factors of the Nakajima test-setup, such as friction, which leads to deviations from the linear strain path, biaxial prestress and bending superposition. These disadvantages can be circumvented by an alternative test combination of uniaxial tensile test and hydraulic bulge test. In addition, the forming limit capacity of many lightweight materials is underestimated using the cross-section method according to DIN EN ISO 12004-2, due to the material-dependent occurrence of multiple strain maxima during forming or sudden cracking without prior necking. In this regard, machine learning approaches have a high potential for a more accurate determination of the forming limit curve due to the inclusion of other parameters influencing formability. This work presents a machine learning approach focused on uniaxial tensile tests to define the forming limit of lightweight materials and high-strength steels. The transferability of an existing weakly supervised convolutional neural network (CNN) approach was examined, originally designed for Nakajima tests, to uniaxial tensile tests. Additionally, a stereo camera-based method for this purpose was developed. In our evaluation, we train and test materials, including AA6016, DX54D, and DP800, through iterative data composition, using cross-validation. In the context of our stereo camera-based approach, strains for different materials and thicknesses were predicted. In this cases, our method successfully predicted the major strains with close agreement to ISO standards. For DX54D, with a thickness of 0.8 mm, the prediction was 0.659 (compared to ISO's 0.664 ). Similarly, for DX54D, 2.0 mm thickness, the predicted major strain was 0.780 (compared to ISO 0.705 ), and for AA6016, at 1.0 mm thickness, a major strain of 0.314 (in line with ISO 0.309 ) was estimated. However, for DP800 with a thickness of 1.0 mm, the prediction yielded a major strain of 0.478 (as compared to ISO 0.289 ), indicating a divergence from the ISO standard in this particular case. These results in general, generated with the CNN stereo camera-based approach, underline the quantitative alignment of the approach with the cross-section method. [ABSTRACT FROM AUTHOR]

Liquid metal (LM) exhibits a distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state, thus it is considered a promising material for high-performance soft electronics. However, rapid patterning LM to achieve a sensory system with high sensitivity remains a challenge, mainly attributed to the poor rheological property and wettability. Here, we report a rheological modification strategy of LM and strain redistribution mechanics to simultaneously simplify the scalable manufacturing process and significantly enhance the sensitivity of LM sensors. By incorporating SiO2 particles into LM, the modulus, yield stress, and viscosity of the LM-SiO2 composite are drastically enhanced, enabling 3D printability on soft materials for stretchable electronics. The sensors based on printed LM-SiO2 composite show excellent mechanical flexibility, robustness, strain, and pressure sensing performances. Such sensors are integrated onto different locations of the human body for wearable applications. Furthermore, by integrating onto a tactile glove, the synergistic effect of strain and pressure sensing can decode the clenching posture and hitting strength in boxing training. When assisted by a deep-learning algorithm, this tactile glove can achieve recognition of the technical execution of boxing punches, such as jab, swing, uppercut, and combination punches, with 90.5% accuracy. This integrated multifunctional sensory system can find wide applications in smart sport-training, intelligent soft robotics, and human-machine interfaces. [ABSTRACT FROM AUTHOR]

This study aims to increase the limited formability of the Ti-6Al-4V sheet at room temperature using the pulsating hydraulic bulging and to investigate the microstructural reasons for the increased formability. Accordingly, monotonic and pulsating hydraulic bulge tests (HBTs) were applied to Ti-6Al-4V sheets with 0.55 mm thickness at room temperature, and the underlying microstructural reasons for the improved formability were investigated by conducting detailed microstructural characterizations. The experimental results showed that the pulsating HBT samples reached 15.4% higher bulge dome height than the monotonic HBT samples, and a more homogeneous thickness distribution was achieved by pulsating bulging. The thickness and microhardness distributions, dislocation density estimations, and fracture surface analysis were utilized to correlate the increased formability with the microstructure. It was determined that stress relaxation occurred during the pulsating HBT, resulting in the achieved improved formability. The decrease in the dislocation density in the early stage of forming prevented the locking of the dislocations and delayed the occurrence of the damage, i.e., leading to the increased bulge dome height. The higher plastic deformation resulting from the increased formability also increased the hardness along the cross-section. The increased formability of the Ti-6Al-4V sheet during the pulsating HBT and the underlying microstructural phenomena elaborated in this study are expected to make significant contributions to the current literature on the sheet metals with limited formability at room temperature. [ABSTRACT FROM AUTHOR]

Determination of sheet metal formability, which is commonly evaluated through a forming limit curve (FLC), is an essential task for part designs in the automotive engineering community. This study provides a coherent comparison among four theoretical FLC criteria including Swift's instability, Hill's localized neck, Storen–Rice bifurcation analysis, and Hora's MMFC. Within these criteria, closed-form solutions for FLC are available for fast and expensiveness explicitly estimating the forming limit diagram (FLD) of sheet metals. According to their closed-form solutions, an empirical suggestion is proposed to improve the accuracy of the theoretical FLC. Quantitative comparisons are then made to evaluate the performance of these criteria for numerous aluminum alloys and steel sheets which are frequently used in automotive industries. Based on the comparisons, the advantages and limitations of each model are discussed from a physical point of view, which appears to be a useful suggestion for selecting a proper theoretical model to evaluate the FLD of sheet metals without conducting experimental tests. [ABSTRACT FROM AUTHOR]

Advanced high-strength steels (AHSS) have become increasingly popular in the automotive industry due to their high yield and ultimate tensile strengths, enabling the production of lighter car body structures while meeting safety standards. However, they have some setbacks compared to conventional steels, such as edge cracking through sheet thickness caused by forming components with shear-cut edges. When characterizing the formability of sheet metal materials, the hole expansion test is an industry-standard method used to evaluate the stretch-flangeability of their edges. However, accurately visualizing the first cracking is usually tricky and may be subjective, often leading to inconsistent results and low reproducibility with some impact of the operator on both direct and post-processing measurements. To address these issues, a novel digital image processing method is presented to reduce operator reliance and enhance the accuracy and efficiency of the hole expansion test results. By leveraging advanced image processing algorithms, the proposed approach detects the appearance of the first edge cracks, enabling a more precise determination of the hole expansion ratio (HER). Furthermore, it provides valuable insights into the evolution of the hole diameter, allowing for a comprehensive understanding of the material behavior during the test. The proposed method was evaluated for different materials, and the corresponding HER values were compared with the traditional method. [ABSTRACT FROM AUTHOR]

In order to optimize the thermal forging process of 37CrS4 special steel, single-pass thermal pressing tests are conducted, and a strain compensation Arrhenius constitutive equation is proposed based on the stress-strain curves of 37CrS4 at the temperature of 900-1100°C and the strain rate of 0.1-10 s-1. The stress values calculated from the equation are in good agreement with the counterparts in the thermal simulation compression test. The high correlation between the calculated and experimental data verifies the correctness of the strain compensation based on Arrhenius constitutive equation. According to the dynamic material model and instability criterion, the processing maps of 37CrS4 are established. It is concluded that 37CrS4 is more suitable for thermal working at a strain rate of 0.1-0.37 s-1 and temperature of 1000-1100°C. [ABSTRACT FROM AUTHOR]

Isostatic pressure-carrying properties of conventional flexible dies commonly fail to adapt to the forming of shell with sharp geometry change since pressure required by local region of sheet metal is unequal. In order to deal with this problem, a forming method based on differentiated pressure field was proposed in this work. Heterogeneous elastomers fabricated from partitioned elastomers with different mechanical properties were employed to create a differentiated and adjustable pressure field. Analytical modeling, finite element analysis, and bulge tests of the proposed forming process were carried out. Concretely, when heterogeneous elastomers' ratio of shore hardness of two partitions (ζ) decreased from 34 to 1, filling ratio (ω) of sheet metal corresponding to the "softer" side of the flexible die reduced from 48.76% to 40.71%, and deviation of the filling ratio (λ) decreased from 12.09% to 0, showing the descending filling capacity and deformation nonuniformity. In addition, position of bulged dome shifted from center to one side where sheet metal was in contact with the "stiffer" partition of heterogeneous elastomers along the radial direction. The controllable nonuniform deformation and strain in different regions could be induced. Numerical results showed that through adjusting ζ of heterogeneous elastomers to enhance or weaken the pressure on one side of the sheet metal, stress path deviated or approached the equal biaxial tension stress state, which explained the mechanics of the proposed forming method. Further applications of the proposed method in the forming of nonsymmetric shell components will be expectable. [ABSTRACT FROM AUTHOR]

Currently, the single-point incremental forming process often faces issues such as insufficient formability of the sheet metal and low strength of the formed parts. To address this problem, this study proposes a pre-aged hardening single-point incremental forming (PH-SPIF) process that offers several notable benefits, including shortened procedures, reduced energy consumption, and increased sheet forming limits while maintaining high mechanical properties and geometric accuracy in formed components. To investigate forming limits, an Al-Mg-Si alloy was used to form different wall angles during the PH-SPIF process. Differential scanning calorimetry (DSC) and transmission electron microscopy (TEM) analyses were conducted to characterize microstructure evolution during the PH-SPIF process. The results demonstrate that the PH-SPIF process can achieve a forming limit angle of up to 62°, with excellent geometric accuracy, and hardened component hardness reaching up to 128.5 HV, surpassing the strength of the AA6061-T6 alloy. The DSC and TEM analyses reveal numerous pre-existing thermostable GP zones in the pre-aged hardening alloys, which undergo transformation into dispersed β" phases during the forming procedure, leading to the entanglement of numerous dislocations. The dual effects of phase transformation and plastic deformation during the PH-SPIF process significantly contribute to the desirable mechanical properties of the formed components. [ABSTRACT FROM AUTHOR]

In this paper, a novel method was proposed to improve the production efficiency and formability of titanium alloy, which was named triple-layer sheet hot stamping with a cold die cooling (THF). The titanium alloy sheet was clamped by two steel sheets with no adhesive added, then heated, transferred and formed together. In order to verify the ability in enhancing formability of this process, spherical part forming tests were carried out to study the formability under the single-layer sheet hot stamping (SHF) and THF. Finally, a plug socket part was formed to verify the practicability of the novel forming process. The finite element (FE) model was established to analyze the forming process finding that the formability of the parts were significantly improved after using THF process. Comparing with SHF process, the stamping depth increases by 135.7% at 900 °C in the THF process. The forming limit strain increases from 0.18 of the single-layer sheet to 0.51 of the triple-layer sheet. The forming limit strain obtained by the THF process is close to that of isothermal forming. The friction state is one of the main reason for improving formability. Moreover, for plug socket parts, there is almost no thinning of the part in the THF process at 900 °C. In conclusion, it has great advantages in improving the formability of titanium alloy using the THF process. [ABSTRACT FROM AUTHOR]

Considering the increasing use of high-speed presses, such as high-speed servo presses, in the automotive industry, it seems necessary to investigate the formability of sheet metals in this range of forming speed. Therefore, this study has been conducted to investigate the effect of medium strain rate forming on the formability of the St14 steel sheet. Tensile tests were done at various strain rates, and formability tests were performed to create forming limit curves at the quasi-static and impact forming. Finite element simulation was used to extract the numerical forming limit curves. The material model was entered into the simulation by considering the strain rate effect using the VUHARD subroutine. The results of tensile tests showed that some influential strain-hardening indicators reduce with strain rate enhancement. Also, using the material model, the tensile behavior was predicted with good accuracy at each strain rate. In impact forming, fracture and strain concentration was transferred to the dome center, and the dome height in biaxial stretching was reduced by 17.1% compared to quasi-static forming due to the variation of frictional conditions. The forming limit curve of impact forming was shifted to the lower values and right side of the forming limit diagram compared to quasi-static forming. In impact forming, the forming limit in plane-strain condition was reduced by 8.1% compared to quasi-static forming. Also, the simulation results, including fracture position, forming limit curve, and dome height in both forming processes, were in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

The identification of Johnson-Cook parameters and the effect of different temperature gradients on A1050 sheet metal formability were performed. Tensile tests and modified Erichsen were carried out at different temperatures and also combined with numerical simulation to identify Johnson-Cook model parameters and the failure criterion. The obtained parameters were validated using the steam bulge test. A good correlation between numerical and experimental results was obtained in terms of failure behavior during the hot forming process. It was observed that hot forming improves the Erichsen index, and the thermal gradient strongly affects the failure zone position in the deformed specimens. [ABSTRACT FROM AUTHOR]

Magnetic smart materials were employed as pressure-carrying medium in sheet metal flexible die forming process to achieve the real-time control of sheet formability in recent years. Yet, few studies involved the mechanism behind this phenomenon, which restricts the improvement of process design. Thus, elastic composites with magnetic-field-dependence (e.g., magnetorheological elastomer, MRE) were taken as an example to investigate their effects on sheet formability and the reason behind that in this work. MREs with different contents of hydroxy iron particles (φ) were fabricated, and their mechanical properties in the presence of external magnetic field with different flux density (B) were determined and introduced into finite element analysis (FEA). Bulge tests of Al1060 sheet employing MREs as the flexible dies were carried out under external magnetic field with the monitoring of digital image correlation (DIC) system. The results showed that, in the case of B = 1950 Gs, limit bulge height (H*) and critical strain (ε*) of deformed sheet respectively increased by 6.7% and 16.4% when adopting appropriate φ (i.e., φ = 20%), and, in the case of φ = 10%, they separately increased by 13.8% and 35.2% when adopting appropriate B (i.e., B = 1650 Gs). Compared with silicone rubber, forming pressure transmitted by MREs decreased under external magnetic field, which reduced equivalent stress of sheet metal and increased stress ratio of two in-plane stresses. By controlling MREs' mechanical properties, their pressure-transmitting properties could be adjusted. On the basis of stress state analysis, mechanism on the increased sheet formability when MREs served as the flexible dies was clarified. [ABSTRACT FROM AUTHOR]

Crystalline metals generally exhibit good deformability but low strength and poor irradiation tolerance. Amorphous materials in general display poor deformability but high strength and good irradiation tolerance. Interestingly, refining characteristic size can enhance the flow strength of crystalline metals and the deformability of amorphous materials. Thus, crystalline–amorphous nanostructures can exhibit an enhanced strength and an improved plastic flow stability. In addition, high-density interfaces can trap radiation-induced defects and accommodate free volume fluctuation. In this article, we review crystalline–amorphous nanocomposites with characteristic microstructures including nanolaminates, core–shell microstructures, and crystalline/amorphous-based dual-phase nanocomposites. The focus is put on synthesis of characteristic microstructures, deformation behaviors, and multiscale materials modelling. [ABSTRACT FROM AUTHOR]

Hole expansion ratio is widely used to estimate the stretch flangeability of sheet metals which is a critical property of formability and to evaluate the efficiency of a forming process. Although many experiments were conducted in the past to identify the key tensile properties affecting hole expansion ratio, their results failed due to the data scarcity. This work demonstrates a machine learning framework coupled with imputation methods to augment both the quantity and quality of collected experimental data. Especially, a generative adversarial imputation network (GAIN) is used to impute the missing tensile properties in the collected experimental data. With the imputed data, the hole expansion ratio is predicted through an extra tree regressor. In terms of the imputation performance, GAIN resulted in the lowest root mean square error of 0.09146 when 50 known tensile properties are randomly removed and imputed with GAIN. In terms of the hole expansion ratio prediction performance, the extra tree regressor showed the lowest root mean square error of 0.124 compared to other machine learning models. Finally, the influence of each tensile property on the hole expansion ratio is analyzed using Shapley additive explanations, an explainable artificial intelligence technique. In this study, the influences of various tensile properties on hole expansion ratio were quantitatively determined for the first time via machine learning and this analysis will accelerate the exploration of sheet metals with high formability performances. [ABSTRACT FROM AUTHOR]

A melting lithium alloying strategy enhances the affinity with copper foil to obtain ultra-thin composite lithium metal electrode, which shows high activity lithium utilization rate and stable cycling performance. [Display omitted] Before lithium (Li) metal can be formally used as the anode material of Li-ion battery, the key technical defects of Li metal electrode, such as low active Li metal proportion and low mechanical strength, must be solved. Herein, the surface affinity of molten lithium-copper (LiCu) alloy with Cu foil is improved by alloying Cu and Li in a molten state. The surface of Cu foil naturally adsorbs an ultra-thin (∼30 μm) composite Li metal layer. The ultra-thin composite Li metal layer can greatly reduce the amount of inactive Li, and the Cu foil improves the mechanical strength and engineering workability of Li metal anode. In addition, the enhanced Young's modulus facilitates the uniform Li plating/stripping process. As a result, the stable cycle stability of up to 600 h and the average overpotential of 13 mV (area specific capacity is 1 mAh cm−2 and current density is 1 mA cm−2) are achieved. The cycle life is higher than 150 h even though the maximum utilization rate of Li is greater than 50%. The Li metal full battery assembled with the commercial NCM811 cathode shows more stable cycle performance and Coulombic efficiency. Such strategy can effectively pave the way for the practical application of Li metal anode. [ABSTRACT FROM AUTHOR]

Lightweight sheet metals are attractive for aerospace and automotive applications due to their exceptional properties, such as low density and high strength. Sheet metal forming (SMF) is a key technology to manufacturing lightweight thin-walled complex-shaped components. With the development of SMF, numerical simulation and theoretical modelling are promoted to enhance the performance of new SMF technologies. Thus, it is extraordinarily valuable to present a comprehensive review of historical development in SMF followed by state-of-the-art advanced characterization and modelling approaches for lightweight metallic materials. First, the importance of lightweight materials and their relationship with SMF followed by the historical development of SMF are reviewed. Then, the progress of advanced finite element technologies for simulating metal forming with lightweight alloys is covered. The constitutive modelling of lightweight alloys with an explanation of state-of-the-art advanced characterization to identify the constitutive parameters are presented. Then, the formability of sheet metals with major influencing factors, the techniques for measuring surface strains in SMF and the experimental and modelling approaches for determining the formability limits are clarified. Finally, the review is concluded by affording discussion of the present and future trends which may be used in SMF for lightweight metallic materials. [ABSTRACT FROM AUTHOR]

In this study, Ultrasonically Assisted Deep Drawing Process was developed in order to improve formability of sheet metals in Conventional Deep Drawing Process. Effects of ultrasonic vibrations, applied onto the blank holder in axial direction, on formability of sheet metal were investigated numerically by finite element analyses, and the results of such analyses were verified by deep drawing experiments. In the numerical study, a methodology for two-stage finite element analyses including transient structural and forming analysis was developed. In conventional and ultrasonically assisted deep drawing analyses, limiting drawing ratios and maximum drawable cup depths for DC01 and DC04 materials prone to certain process parameters were compared. With application of ultrasonic vibrations, an increase of up to 9% in limiting drawing ratio and up to 26% in cup depth were achieved. In the analyses performed on circular materials of identical diameters, it was determined that the thinning on sheet metal decreased by up to 43%. As result of the validation experiments, increase in limiting drawing ratio and cup depth was achieved as 11% and 31%, respectively. Numerical results were found to be in good agreement with experimental results since dynamic impact, stress superposition and contact separation effects of ultrasonic vibrations could be effectively modeled in finite element analyses with the proposed method. Small differences in obtained results may be due to the reason that it was not possible to involve the effects of acoustic softening and friction coefficient reduction on the material in numerical analyses. [ABSTRACT FROM AUTHOR]

The automotive industry requires more and more light materials with good strength and formability at the same time. The answer to this type of demands are, among others, aluminium alloys of the 6xxx series, which are characterized by a high strengthto-weight ratio and good corrosion resistance. Different material state can affect formability of AlMgSi sheets. These study analysed the influence of heat treatment conditions on the drawability of the sheet made of 6082 aluminium alloy. The studies on mechanical properties and plastic anisotropy for three orientations (0, 45, 90°) with respect to the rolling direction were carried out. The highest plasticity was found for the material in the 0 temper condition. The influence of heat treatment conditions on the sheet drawability was analysed using the Erichsen, Engelhardt-Gross, Fukui and AEG cupping tests. It was found that the material state influenced the formability of the sheet. In the case of bulging, the sheet in the annealed state was characterized by greater drawability, and in the deep drawing process, greater formability was found for the naturally aged material. [ABSTRACT FROM AUTHOR]

In the last few years, demand for hot stamped components has increased in the automotive industry. Determination of formability under hot stamping is challenging due to elevated temperature, fast cooling, and high punch velocity. Although there was various strive for formability determination, but there were limitations with experiments like non-uniform heating of specimen, non-uniform strain, and temperature distribution. Therefore, in this work, an experimental apparatus was developed to determine formability at room temperature, high temperature, hot stamping conditions, and any complex process cycle involving heating and cooling. New specimen was designed to produce different strain paths, uniform, and homogenous temperature distribution with the help of FEM software using thermomechanical and thermoelectrical simulation. A micro hemispherical dome-based experimental apparatus was designed using Solidworks. The designed apparatus was used in conjunction with the thermo-mechanical simulator (Gleeble-3800). Thermomechanical analysis was done in PAM STAMP software to optimize specimen size and shape to get uniform strain distribution and different strain paths. A thermoelectric FEM model was developed using Abaqus 6.14 to optimize the temperature distribution in the specimen. The developed model enables choosing the appropriate polarity of the electrical cable connection to achieve uniform temperature distribution in the specimen. Strain path and temperature profiles for experiment and simulation were compared. Further, a forming limit curve was developed using the designed apparatus to verify the feasibility of the apparatus. For feasibility test of apparatus, hot stamping process was selected. This new design apparatus can be used for a range of temperatures up to 1000 °C, hot stamping conditions, and for different materials (aluminum, magnesium alloys, different grade of steel, etc.). It concludes that the connection of different polarities of electrical cable was critical for homogenous and uniform temperature distribution in specimens. [ABSTRACT FROM AUTHOR]

The effects of surface dissolution on dislocation activation in FeSi6.5 steel are quantitatively studied by analyzing the stress relaxation data using the thermal activation theory of dislocation. The stressed FeSi6.5 steel sample in acid solutions (H2SO4 or HCl) exhibits a much higher rate of stress reduction with time compared with that in air or deionized water. As the stress relaxation time is prolonged to 20 min, the relaxation rates are 0.055 MPa·min−1 in water and 0.074, 0.1, 0.11 MPa·min−1 in H2SO4 solutions with pH 4, 3, and 2, respectively. In a NaCl solution, a slight increase in the relaxation rate compared with air was found. Higher acidity (lower pH) of the solution inducing higher stress relaxation rate implies the softening is associated with the anodic dissolution of the surface layer and the accelerated (additional) flow of dislocations. The analyses using the thermal activation theory of dislocation during relaxation reveal the mechanism for the accelerated plastic flow induced by the corrosive medium. The variations of these parameters are related to the relaxation of the stress field of dislocations and the weakening of interaction between slip dislocations and short-range obstacles. The chemomechanical effect, including a reduction in apparent activation energy and a decrease in waiting time for dislocation to obtain sufficient thermal activation energy to cross obstacles, causes an increase in the stress relaxation rate (plastic strain rate). The study confirms that surface dissolution accelerates the plastic flow of metals and supports the view that surface dissolution facilitates dislocation slip. It is helpful to improve the formability of brittle metals. [ABSTRACT FROM AUTHOR]

The extraction of iron ore has a fundamental role in the Brazilian economy. However, such activity generates considerable volumes of waste whose disposal, even if regulated and licensed, has a significant environmental impact. The worldwide concern for sustainable practices along with the urgency for measures to mitigate environmental damage, justifies research on its use in other activities. Therefore, the present study aims to analyze the test results of laboratory versus field of mixtures composed of mining waste. The field studies were made on the execution of an experimental section on the BR 040 highway, in Minas Gerais - Brazil. According to the validation of the laboratory results, the mixtures composed of 35% Tailings + 15% Waste Rock + 50% Canga of Ore and 35% Tailings + 20% Gravel 1 + 45% Gravel 0 were used in the base and sub-base layers of the experimental section, respectively. The field technological control showed that the mixtures had an anomalous behavior from the one observed in the laboratory, mainly regarding strength and deformability. [ABSTRACT FROM AUTHOR]

[Display omitted] • An efficient/accurate model for predicting interface fatigue performance is proposed. • A multi-fidelity RSM for MPH structures with micro-structure interlock is developed. • The non-synergistic mechanisms on MPH static and fatigue performances are elucidated. • The developed methodology for predicting MPH's performance is validated in industry. Metal-polymer hybrid (MPH) structures, featuring a micro-structure interlocking design, combine the high strength of metal with the exceptional formability of polymer-based composites and have gained significant attention in automotive load-bearing components. Challenges persist in accurately predicting MPH structure fatigue life using small samples with diverse interlock parameters and swiftly generating static strength and fatigue life response surfaces for automated optimization. We introduce a simplified model for predicting fatigue at the interfaces of MPH structures. Our multi-fidelity prediction method integrates this model with limited high-fidelity data samples to assess both the static strength and fatigue life effectively. This method predicts the deviation with less than 3% error compared to FSR-FEM, achieving a reduction in prediction time of over 60%. Additionally, we elucidate the non-synergistic mechanisms of key interfacial locking parameters between static strength and fatigue life at the micro-scale. Finally, we propose and apply a multi-objective synergistic optimization strategy to the MPH thrust rods in vehicles. By utilizing our optimization method, we achieve a 27.9% weight reduction compared to steel counterparts, while enhancing overall tensile strength by 11.8% and significantly improving fatigue life by 46.7% compared to MPH torque rods lacking an interlock interface. [ABSTRACT FROM AUTHOR]

Forming limit curves (FLCs), which are constructed using the limit strains at localised necking, are the most widely used tools for the evaluation of the formability of sheet metals. Fracture forming limit curves (FFLCs) are more recently developed, complementary tools for formability evaluation which are instead constructed using the limit strains at fracture. Since the formability depends strongly on forming conditions such as strain state, temperature and strain rate, models for predicting FLCs and FFLCs are essential for the optimisation and further application of hot forming processes in which these forming conditions vary significantly with both position and time. However, no model has so far been developed to predict FFLCs either alone or in conjunction with FLCs for sheet metals such as boron steel under hot stamping conditions. In this study, a set of unified viscoplastic constitutive equations for the prediction of both FLCs and FFLCs based on continuum damage mechanics (CDM) has been formulated from a set of recently developed constitutive equations for dislocation-based hardening, in combination with two novel coupled variables characterising the accumulated damage leading to localised necking and fracture. The novel variables take into account the effects of strain state, temperature and strain rate on the formability of sheet metals. The material constants in the CDM-based constitutive equations have been calibrated using experimental data comprising true stress-true strain curves and limit strains of a 22MnB5 boron steel obtained at a range of temperatures and strain rates. Investigation of the effect of varying selected parameters in the coupled damage variables on the resulting computed FLCs and FFLCs has demonstrated the flexibility of the model in enabling curves of different shapes and numerical values to be constructed. This indicates the potential of the CDM-based constitutive model for application to other materials for warm or hot stamping processes. [ABSTRACT FROM AUTHOR]

The accumulation of waste tires leads to environmental degradation caused by uncontrolled dumping in landfills, which are prone to fire and emit harmful gases like carcinogens. Reusing this as reinforcement to selfcompacting concrete (SCC) is an alternative way to address the issue. For over a decade, SCC emerged in the construction industry due to its enhanced mechanical properties and capacity to self-consolidate on its own. However, there is still limited literature describing the behavior of SCC with tire waste steel fiber (TWSF). This study provides an overview of the extraction, quantification, geometric characterization, surface characterization, and application of TWSF to self-compacting concrete to determine workability and the compressive strength of SCC with TWSF. A total of five mixes were prepared, including the control noted as SCC without fiber and SCC with TWSF, with fiber content ranging from 0.7 %, 1 %, 2 %, and 3 %. The fresh properties were evaluated using the European Federation for Specialist Construction Chemicals and Concrete (EFNARC) standards such as slump flow test, T500, L-Box, and wet sieving or GTM Screen Stability Test. In addition, the compressive strength was determined after 28 days. The investigation reveals that these fibers can be retrieved in three ways: manually cutting the tire's edge, using a specialized machine to pluck the fibers, or incinerating them. It was projected that 4.85 - 7.16 x 105 t of TWSF might be generated annually. The result of the inclusion of TWSF in SCC does not significantly affect the workability. However, there is a reduction in the passing ability of about 11.713 % and 186.75 % for GTM screen stability, but all mixes are still within the acceptable ranges specified on the EFNARC standard. In contrast, the results reveal that adding 3 % TWSF to SCC enhances compressive by 31 %, which might be due to the fiber's uneven surface, increasing the bond between the fiber and concrete. As a result, the TWSF can be utilized to strengthen the SCC and fully applied in the construction industry. Additionally, it is advantageous to combine TWSF with SCC to extend its life resulting in lower carbon emissions produced during the production processes. [ABSTRACT FROM AUTHOR]

Copyright of Materials & Technologies / Materiali in Tehnologije is the property of Institute of Metals & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This article presents a range of mix design formulations to obtain metakaolinbased geopolymer synthesis. Geopolymer samples were synthesized from metakaolin, a 10 M sodium hydroxide solution, and alkaline sodium silicate. These three components were mixed in different proportions to form a paste which was molded in a cylindrical shape, set at room temperature for 24 hours, and demolded. The workability of the paste, the integrity of the samples, development of efflorescence, and the presence of undissolved metakaolin particles in the microstructure of the geopolymer matrix were observed. Since sodium and water play a vital role in the geopolymerization and were added at fixed proportions, a mix design was employed based on the molar proportions of aluminum, silicon, and sodium plus water. The simplex design plot was able to separate the regions of a mix of the components that showed different behaviors according to the observed responses. The dissolution of metakaolin, condensation of orthosialate and silicate species, which are expected to interact with each other according to the model of geopolymerization of Davidovits, can explain the observed results. "Good results" (no release of white powder, no efflorescence, no shrinkage, and no cracks) after 28 days of curing at room conditions were observed for the molar proportions 0.097 < Al < 0.112, 0.120 < Si < 0.178, and 0.711 < Na+H2O < 0.775 (Na/H2O = 0.185). [ABSTRACT FROM AUTHOR]

The forming limit diagrams (FLDs) characterizing the formability of sheet metals are usually obtained by applying proportional loadings. Nevertheless, the industrial processes involve strain path changes that can modify the limit-strain values. In addition, for strongly anisotropic sheet metals such as the Zn-Cu-Ti zinc alloy, large differences in forming limit curves (FLCs) with respect to the sheet rolling direction are observed. In the present work, the analysis of the effect of bilinear strain paths on the FLC is addressed by both experimental measurements and numerical simulations. For this purpose, a miniature testing device was used that allows evaluation of the influence of strain path changes on the limit strain on samples at 0°, 45° and 90° with respect to the sheet rolling direction cut from non-standard large samples previously subjected to a prestrain along the RD up to an early deformation of ~0.12. Numerical simulations were carried out using the well-known Marciniak and Kuczynski (MK) theory in conjunction with the viscoplastic self-consistent (VPSC) crystal plasticity model. In order to account for the grain fragmentation process due to the continuous dynamic recrystallization (CDRX) mechanism, an ad hoc short-range interaction effect (SRE) model was included in the simulations. Additionally, the measured and simulated texture evolution of Zn-Cu-Ti alloy sheets at the different stages of the deformations were shown. The capacity of the MK-VPSC-SRE model was validated, and the limitations to simulating the texture development, flow stress and forming limit curves, including a non-proportional strain path, were discussed. [ABSTRACT FROM AUTHOR]

The use of ultra-high performance concretes (UHPC) in the modern construction industry is increasingly widespread. UHPCs are a type of concrete that provides advantages in solving many engineering problems. UHPCs have superior properties compared to conventional concretes in terms of workability, self-settling, as well as high strength and durability. However, although UHPCs have many advantages, achieving the desired workability is one of the biggest challenges of the production procedure, since they contain high amounts of powder materials. Therefore, the aim of this study is to determine the most suitable superplasticizer (SP) additive in terms of workability and strength by using different SP additives in UHPC mixtures. In this study, workability and strength parameters were tested on UHPC mixtures using 8 different SP additives. The SPs used were named A, B, C, D, E, F, G, H. First of all, the spreading diameters of the obtained mixtures were measured. For each mixture, compressive strength, unit weight, ultrasound velocity, Schmidt hammer rebound and Leeb hardness measurements were performed on 70x140 mm sized cylindrical samples taken on days 2, 7 and 28. Since SPs have a working principle at the interfaces of particles in the internal structure of concrete, different behaviors were observed on workability, even if a little. All the results obtained have been compared with the literature and it has been proven that they meet the UHPC specifications. As a result of the study, the best compressive strength value (127.83 MPa) was achieved with the G superplasticizer, and the flow diameter value was determined as 230 mm. [ABSTRACT FROM AUTHOR]

Cold rolling has detrimental effect on the formability of sheet metals. It is, however, inevitable in producing sheet high quality surfaces. The effects of cold rolling on the forming limits of stretch sheets are not investigated comprehensively in the literature. In this study, a through experimental study is conducted to observe the effect of different cold rolling thickness reduction on the formability of sheet metals. Since the experimental procedure of such tests are costly, an artificial intelligence is also adopted to predict effects of cold thickness reduction on the formability of the sheet metals. In this regard, St14 sheets are examined using tensile, metallography, cold rolling and Nakazima's hemi-sphere punch experiments. The obtained data are further utilized to train and test an adaptive neural network fuzzy inference system (ANFIS) model. The results indicate that cold rolling reduces the formability of the sheet metals under stretch loading condition. Moreover, the tensile behavior of the sheet alters considerably due to cold thickness reduction of the same sheet metal. The trained ANFIS model also successfully trained and tested in prediction of forming limits diagrams. This model could be used to determine forming limit strains in other thickness reduction conditions. It is discussed that determination of forming limit diagrams is not an intrinsic property of a chemical composition of the sheet metals and many other factors must be taken into account. [ABSTRACT FROM AUTHOR]

It is shown that the deformability of Ti49.2Ni50.8 and Ti50.0Ni50.0 alloys rolled with electric current is considerably greater than that obtained by cold rolling. The influence of deformation with an electric current on features of the microstructure was investigated. It was demonstrated that strong grain refinement to size of 60-120 nm accompanies the electroplastic rolling process. At the same annealing temperature, the alloy with the initial martensitic structure has a larger grain size. These differences can probably be explained by the different recrystallization temperatures of deformed martensite and austenite. The intensity of strain hardening was compared for both alloys after electroplastic rolling (EPR). The reasons for the different behaviour in the EPR process are discussed. [ABSTRACT FROM AUTHOR]

Drawing die complexity is higher than conventional stamping operations, nowadays. It needs to decrease stamping die operation numbers for a part to reduce project budget consumption. Therefore, frequency of tearing, thinning, crack occurrence increase while this amendment. Force, blank cutting, blank location on the drawing die and process optimization were investigated to decrease tearing, thinning and crack occurrence in Transit bodyside inner panels which have over 110 mm. deep drawing process. Formability was improved at the end of this study. Thus production scrap, stoppage time of stamping line were decreased over 90%. This study was conducted at Ford Otosan. [ABSTRACT FROM AUTHOR]

Liquid metal is being regarded as a promising material for soft electronics owing to its distinct combination of high electrical conductivity comparable to that of metals and exceptional deformability derived from its liquid state. However, the applicability of liquid metal is still limited due to the difficulty in simultaneously achieving its mechanical stability and initial conductivity. Furthermore, reliable and rapid patterning of stable liquid metal directly on various soft substrates at high-resolution remains a formidable challenge. In this work, meniscus-guided printing of ink containing polyelectrolyte-attached liquid metal microgranular-particle in an aqueous solvent to generate semi-solid-state liquid metal is presented. Liquid metal microgranular-particle printed in the evaporative regime is mechanically stable, initially conductive, and patternable down to 50 μm on various substrates. Demonstrations of the ultrastretchable (~500% strain) electrical circuit, customized e-skin, and zero-waste ECG sensor validate the simplicity, versatility, and reliability of this manufacturing strategy, enabling broad utility in the development of advanced soft electronics. In this article, meniscus-guided printing of polyelectrolyte-attached liquid metal particles to simultaneously achieve mechanical stability and initial electrical conductivity at high resolution is introduced. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This work studies the mechanical and quasi-static compression behaviour of AA6082/Metakaolin composites hybridized with nano-silicon nitride (Si3N4) particles. Hybridization with nano-Si3N4 particles was intended to improve the ductility of the composites. The composites were manufactured using an ultrasonication-assisted stir casting process. The weight fraction (wt.%) of Metakaolin was maintained as 7.5 wt.%, and the nano-Si3N4 particles were added by varying their wt.% from 0.5 to 2.5 % at the increment of 0.5 %. A premixing technique was adopted to blend the Metakaolin and Si3N4 reinforcements to improve their wettability and dispersion in the matrix. The tensile properties and microhardness of the composites improved with the incorporation of nano-Si3N4 particles up to 1 wt.%. The compressive strength was higher for the AMC with 1.5 wt.% Si3N4. The workability of hybrid composites was studied by the cold upsetting process where the composites were subjected to quasi-static compression. [ABSTRACT FROM AUTHOR]

This study theoretically and experimentally investigates blanking/piercing operations of explosively welded commercial DP600 advanced steel sheets, Al1100 aluminium sheets, and DP600-Al1100 composite plates, in which punches with different tip shapes are used. The experimental studies included several methods, such as explosive welding, punching, tensile testing, and macro image analyses using digital, optical, and SEM microscopes. The theoretical studies comprised finite element modelling using 3D models. The explosive weld was successfully applied, and the obtained Fe-Al weld microstructure was evaluated. A total of five punches, which have different tip shapes - flat-ended (0°), angled (16°), concave (R1 and R2), and V-shaped (V16) tips - were used in the experiments. Blanking forces were obtained using a load cell mounted to the die, a data acquisition card, an amplifier, and computer software. The simulation and the experimental study results were in agreement and clearly showed the effects of the punch shear angle and shape on the forces required for blanking/piercing. [ABSTRACT FROM AUTHOR]

A new type of Ti-18.4 Nb-1.4Zr-0.3Ta-4.3 O exhibiting near-linear deformation behavior was created to elucidate the core principles behind its near-linear deformation behavior in quasi-Gum Metals. The in situ simultaneous X-ray diffraction study shows that a β→α″ stress-induced martensitic transformation (SIMT) persists and covers a large stress range under the near-linear deformation of Ti-18.4 Nb-1.4Zr-0.3Ta-4.3 O. Within the SIMT process, the variant 5 of α″ martensite usually forms more readily as it can output the maximum phase transformation strains compared to the other equivalent variants. The experimental results indicate that near-linear deformability of quasi-Gum Metal is due to the combined influence of its inherent deformation (including elastic and trace plastic) together with a SIMT that operates over a large strain range. These findings have helped to develop a more comprehensive view of the principle behind the near-linear deformation in quasi-Gum Metals and Gum Metal. • A quasi-Gum Metal with near-linear deformation behavior consisting of Ti-18.4 Nb-1.4Zr-0.3Ta-4.3 O was designed. • The near-linear deformation mechanism of this alloy was studied. • The combined effect of inherent deformation together with the SIMT contributes to the near-linear deformability. [ABSTRACT FROM AUTHOR]

An advanced Crystal Plasticity Finite Element (CPFE) approach is developed to accurately predict the ductility limit strains of thin metal sheets. This method uses polycrystalline unit cells to represent the metal sheets at the macroscopic level. The macroscopic behavior of these unit cells is determined based on that of the constituent single crystals using the periodic homogenization multiscale scheme. At the single crystal scale, the constitutive framework follows a finite strain rate-independent formulation, with the flow rule governed by the Schmid law. The evolution of the single crystal yield surface is described through a physically-based mixed hardening model, where isotropic hardening is characterized by a dislocation density-based formulation, while kinematic hardening is described by the nonlinear Armstrong–Frederick model. The unit cell ductility limit strains are predicted by the Rice bifurcation criterion. The reliability of the mixed hardening model in accurately reproducing mechanical behavior is confirmed through simulations of uniaxial tension/compression loading. Then, the developed computational strategy is used to investigate the impact of key microstructural hardening parameters on the initiation of localized necking under linear strain paths. The numerical predictions reveal the significant influence of these parameters on the formability of thin metal sheets. Additionally, the analysis of ductility limits under non-linear strain paths demonstrates a strong dependency of the numerical predictions on strain path changes. The numerical predictions obtained by the developed CPFE multiscale strategy are compared with experimental results from the literature. In summary, the proposed approach provides a reliable tool for accurately predicting the ductility limits of thin metal sheets, offering valuable insights for engineering applications. • A dislocation density-based mixed hardening model is considered. • The Rice bifurcation criterion is used to predict plastic strain localization. • The effects of microstructural hardening parameters and texture are investigated. • The ductility limits under linear and non-linear strain paths are examined. • The kinematic hardening results in a reduction of the predicted ductility limits. • The proposed framework predicts accurate ductility limits compared to experiments. [ABSTRACT FROM AUTHOR]