Plastic Deformation Capacity Research Articles

Experimental Study on the Mechanical Properties of C30 Molybdenum Tailings Concrete after High-Temperature and Sulfate Corrosion

In order to study the durability of molybdenum tailings concrete after a specific period of wet-dry cycle tests and exposure to high temperatures, this paper investigates the rule of change of the mechanical properties of molybdenum tailings concrete under the coupled influence of sulfate corrosion and high-temperature environmental conditions. A total of five C30 concrete prisms with molybdenum tailings content (0%, 25%, 50%, 75%, and 100%) were considered in the tests, with sulfate solution concentrations of 0 g/L, 20 g/L, and 50 g/L, and exposure temperatures of 25° at room temperature and 400° at high temperature, respectively. The test results showed that the mass loss rate of concrete prisms with different molybdenum tailings substitution rates under sulfate corrosion and high temperature environment showed an increasing and then decreasing trend. The specimens with 25% molybdenum tailings content still maintain high mechanical properties after wet-dry cycle tests of sulfate solution and high temperature, and the reduction of peak stress in this group is only 11%, and the reduction of elastic modulus is 1%; the rest of the molybdenum tailings content has a reduction of peak stress of about 25%, and the reduction of modulus of elasticity is more than 10%. The plastic deformation capacity of molybdenum tailings concrete decreases under the single-factor effects of wet-dry cycle tests of sulfate solution and high temperature effects, but the plastic deformability capacity of the specimens is enhanced under the combined effects of multiple factors. The stress-strain curve formulas for molybdenum tailings concrete under high temperature, wet-dry cycle tests of sulfate solution, and coupled wet-dry cycle tests of sulfate solution and high temperature were fitted. The results of this study can provide experimental data and valuable references for the engineering application of molybdenum tailings concrete under wet-dry cycle tests of sulfate solution and high temperature conditions, laying a foundation for further research.

Models for the Design and Optimization of the Multi-Stage Wiredrawing Process of ZnAl15% Wires for Spray Metallization.

Metallization, a process for applying anti-corrosion coatings, has advantages over hot-dip galvanizing, such as reduced thermal stress and the ability to work "in situ". This process consists of the projection of a protective metal as coating from a wire as application material, and this wire is obtained by multi-stage wiredrawing. For the metallization process, a zinc-aluminum alloy wire obtained by this process is used. This industrial process requires multiple stages/dies of diameter reduction, and determining the optimal sequence is complex. Thus, this work focuses on developing models with the aim of designing and optimizing the wiredrawing process of zinc-aluminum (ZnAl) alloys, specifically ZnAl15%, used for anti-corrosion applications. Both analytical models and numerical models based on the finite element method (FEM) and implemented by computer-aided engineering (CAE) software Deform 2D/3D v.12, enabled the prediction of the drawing stress and drawing force in each drawing stage, producing values consistent with experimental measurements. Key findings include the modeling of the material behavior when ZnAl15% wires were subjected to the tensile test at different speeds, with strain rate sensitivity coefficient m = 0.0128, demonstrating that this type of alloy is especially sensitive to the strain rate. In addition, the optimal friction coefficient (µ) for the drawing process of this material was experimentally identified as µ = 0.28, the ideal drawing die angle was determined to be 2α = 10°, and the alloy's deformability limit has been established by a reduction ratio r ≤ 22.5%, which indicates good plastic deformation capacity. The experimental results confirmed that the development of the proposed models can be feasible to facilitate the design and optimization of industrial processes, improving the efficiency and quality of ZnAl15% alloy wire production.

Enhancing strength, ductility, and thermal fatigue resistance in Stellite 21 coatings via Mn alloying and Transformation-Induced Plasticity

This study investigates the effect of Mn on the microstructure and mechanical properties of Stellite 21 cobalt-based coatings prepared by laser cladding on 24CrNiMo steel substrates, focusing on utilizing the Transformation-Induced Plasticity (TRIP) mechanism to enhance toughness and thermal fatigue performance. The results indicate that the microstructure of the Stellite 21 alloy coating is primarily composed of γ-Co (FCC) with a minor presence of ε-Co (HCP), M23C6, and M7C3 carbides, which predominantly precipitate at or near the grain boundaries. Upon the addition of Mn, it dissolves into the γ-Co matrix, causing lattice distortion and increasing dislocation density, thereby contributing to solid solution strengthening. Compared to the Mn-free Stellite 21 alloy coating, the coating with 5% Mn exhibits an approximately 21% increase in tensile strength (∼1135 MPa) and a 74% increase in elongation (∼14.5%). This improvement is mainly attributed to the solid solution strengthening caused by lattice distortion due to Mn addition and the synergistic enhancement from the TRIP mechanism facilitated by the lower stacking fault energy. Moreover, the thermal fatigue crack propagation rate in the coating with 5% Mn is reduced by approximately 42.5% compared to the Mn-free Stellite 21 alloy coating. The enhancement in thermal fatigue performance is primarily due to the Mn addition, which stabilizes the ε-Co phase during thermal fatigue processes, enhancing plastic deformation capacity. The phase transformation process alleviates stress concentration, effectively reducing crack propagation rates and ultimately improving the material's thermal fatigue performance.

Exploring the brittle-to-ductile transition and microstructural responses of [formula omitted]−TiAl alloy with a crystal plasticity model incorporating dislocation and twinning

γ−TiAl alloy, with its high specific strength and creep resistance, is ideal for aerospace engines and gas turbines, but its brittleness poses significant manufacturing and processing challenges. To address these issues, this study employs a crystal plasticity finite element method incorporating dislocation and twinning to analyze the brittle-to-ductile transition behavior of γ−TiAl alloy at different temperatures. Additionally, the Bayesian optimization methods are employed to efficiently and accurately obtain parameters related to numerical calculations of crystal plasticity. The results indicate that at room temperature, the high activation resistance of the slip systems in the α2 phase leads to limited slip activity, resulting in poor plasticity. However, at 750 °C and 850 °C, the strength of the slip systems decreases significantly, allowing more α2 phase lamellae in the γ-TiAl alloy to undergo greater plastic deformation. This enhancement in the plastic deformation capacity of the α2phase lamellae reduce the overall deformation incompatibility in the TiAl alloy, thereby improving the overall ductile of the γ-TiAl alloy.

The deformation mechanism of low symmetric Ti–Pt intermetallic compounds containing high density of planar defects

Intermetallic compounds typically exhibit limited plastic deformation capacity due to challenges in activating dislocation slip and deformation twinning, coupled with a lack of alternative deformation mechanisms. Ti–Pt alloys are a prevalent type of intermetallic compound utilized in high-temperature shape memory alloys and as materials for energy applications in electric fields. However, they often exhibit poor deformation capability. Here, we prepared a low-symmetry intermetallic phase, Ti4Pt3, which demonstrates significant plastic deformation capability. This phase features a high density of parallel planar defects, resulting in an exceptionally large lattice periodicity perpendicular to these defects. Through in-situ scanning electron microscope compression tests, we observed substantial plastic deformation in this new phase. Analysis of the deformed Ti4Pt3 phase revealed that the dense planar defects create uniformly distributed sites of internal stress concentration, enabling a rapid increase in back stress within crystals. This phenomenon leads to notable lattice rotation and localized order-disorder transitions, both crucial mechanisms facilitating plastic deformation and enhancing deformation capacity. Our research underscores the potential of leveraging structural asymmetry to enable unconventional deformation mechanisms, thereby enhancing the plasticity of intermetallic materials.

Effects of Cooling Media on Microstructure and Mechanical Properties in Friction Stir Welded SA516 Gr.70 Cryogenic Steel Joints.

SA516 Gr.70 steels were welded by friction stir welding (FSW) under various media of air, water, and water + CO2 cooling, and the effect of the cooling media on the microstructure and mechanical properties of joints was systematically analyzed. The nugget zone (NZ) under the air-cooling condition contained coarse bainite + martensite. Martensite was obtained by decreasing the cooling media temperature. Furthermore, tensile fracturing of the joints occurred in the basal metal (BM), and the ultimate tensile strength of the joints under various cooling media was similar to that of the BM. However, with decreasing cooling media temperature, the total elongation of the joints noticeably increased. Good strength (545 MPa) and elongation (16.8%) were obtained in the joints under the water + CO2 cooling condition since the fine martensite microstructure enhanced the plastic deformation capacity of the joints. In addition, in the NZ under water + CO2 cooling condition, good toughness of 110 J/cm2 was obtained due to a high fraction of high-angle boundaries and fine martensite.

Seismic Performance of Recycled-Aggregate-Concrete-Based Shear Walls with Concealed Bracing

Relatively few studies have been conducted on the seismic performance of recycled aggregate concrete (RAC) shear walls with concealed bracing. To promote the development of high-performance green building structures and the application of RAC in structural components, the seismic performance of RAC shear walls under different influencing factors was tested, and low-cycle reversed loading tests were performed on ten RAC shear walls with different shear-to-span ratios. The test parameters included the recycled coarse aggregate (RCA) replacement ratio, the recycled fine aggregate (RFA) replacement ratio, the axial compression ratio, the shear span ratio and whether to set up the concealed bracing. The influence of the above variables on the seismic performance was then assessed. The results revealed that the bearing capacity, ductility, stiffness and energy dissipation capacity of the RAC shear walls decreased in line with an increase in the replacement ratio of the RFA. However, the bearing capacity, energy consumption and stiffness of the RAC shear walls decreased within 10% and the ductility decreased within 15%. The RAC shear walls were able to meet the seismic requirements of the building structure after reasonable design and use. As the axial compression ratio increased, the bearing capacity of the RAC shear walls improved, but their elastic–plastic deformation capacity was reduced. Setting the concealed bracing significantly improved the seismic performance of the RAC shear walls, such that they achieved a seismic performance close to that of the natural aggregate concrete (NAC) shear wall. After setting up the concealed bracing, the load carrying capacity of the RAC shear walls increased by up to 15%, the ductility increased by up to 20% and the energy consumption capacity increased by up to 50%. A mechanical calculation model of the RAC shear wall was then established by considering the effect of recycled aggregate, the calculated results of which were a good match with the test results.

Enhancing the mechanical performance of 3D-printed self-hardening calcium phosphate bone scaffolds: PLGA-based strategies

Over the last decade, 3D-printed porous calcium phosphates have emerged in the market for customized bone reconstruction. However, despite their excellent biological properties, the inherent brittleness is an obstacle that limits their clinical applications, as the scaffolds must withstand the surgical procedures and the mechanical stresses once implanted. Low-temperature self-hardening calcium phosphate inks offer unique possibilities to be reinforced with polymers, as they do not require high-temperature treatments. This study compares two routes for incorporating poly (lactic-co-glycolic acid) (PLGA) into 3D-printed calcium phosphate scaffolds: i) the use of a PLGA solution as a binder in an alpha-tricalcium phosphate self-hardening ink; ii) the infiltration of a PLGA solution into previously hardened 3D-printed calcium-deficient hydroxyapatite scaffolds. The influence of the added PLGA on the physical-chemical properties, mechanical performance and in vitro biological properties is assessed using a commercially available biomimetic calcium phosphate scaffold as a control. The addition of PLGA increases the plastic deformation capacity and the strength, both in compression and bending, and significantly improves the work of fracture of the scaffolds, up to an 8-fold in compression when PLGA is incorporated as a binder in the ink. Moreover, screwability tests demonstrate the enhanced fixability of the composite scaffolds in a knife-edge ridge indication with challenging fixation in the jaw. Importantly, the improvement of the mechanical properties by the addition of PLGA does not impair the good cytocompatibility of the material. Regarding the two routes studied, the PLGA incorporation in the ink is the best option in terms of overall improvement of the mechanical performance and osteogenic cell response.

Cyclic behavior of beam-to-column connections with vertical oblique angles

Beam-to-column connections with vertical oblique angles are being used in construction; however, such connections have not been adequately researched to confirm their seismic performance. This study investigated the cyclic behavior of beam-to-column connections with vertical oblique angles, offering critical insights through theoretical analysis and full-scale experiments. Mechanical interactions at the beam ends were initially analyzed to predict failure sections and strengths. Full-scale experiments under cyclic loading conditions were conducted for verifying these predictions. The experimental results highlighted the hysteretic behavior, and the failure modes of the beam ends showed that vertical oblique angles have a negligible effect on the hysteretic behavior of the beam-to-column connections. Moreover, the plastic deformation capacity and strain distribution of the beam ends vary with regard to vertical oblique angles, which is consistent with the theoretical predictions. Finite element analysis also confirmed the experimental results, demonstrating the effectiveness of proposed method for predicting the structural performance of the connections.

Effect of loading sequence on the ultra-low-cycle fatigue performance of all-steel BRBs

Buckling-restrained braces (BRBs) are intended to protect the primary structure of buildings by absorbing most earthquake input energy through the plastic deformation of the steel cores. The ultra-low-cycle fatigue performance of BRBs is crucial for their seismic performance as energy dissipators. Despite the plenty of research on the ultra-low-cycle fatigue behavior of steel members, it remains susceptible if arbitrary loading paths have a major effect on the ultra-low-cycle fatigue life or cumulative plastic deformation (CPD) capacity of BRBs. This paper introduces an experimental campaign of nine supposedly identical BRB specimens subjected to three different loading protocols of similar average strain amplitudes. For each loading protocol, the test was repeated for three times to account for possible uncertainty. The results show that the effect of loading protocol is trivial given the similar average strain amplitudes throughout the loading. The Miner's assumption that the loading sequence has no effect on the fatigue life of BRBs is supported by the test results, however, the proper choice of the Coffin-Masson model's parameters is crucial. The skeleton ratio, which is derived from decomposing the hysteresis curve into a skeleton part and a Bauschinger part and has been used to account for the loading path effects, is shown to be insensitive to varied loading protocols by the test results.

Enhancing mechanical properties of medium Mn steel by warm rolling based on laminated elemental segregation

The hot-rolled microstructure of medium Mn steel has coarse grains and severe elemental segregation, resulting in low strength and plasticity. Constructing a multiphase structure, refining the microstructure, and regulating elemental segregation enhance the mechanical properties. In this study, liquid nitrogen treatment created a layered distribution of austenite and martensite. Warm rolling was then used to reduce layer thickness and refine grain structure. After liquid nitrogen and warm rolling treatments, the strength and plasticity of medium Mn steel increased to 1270 MPa and 23.3%, respectively, far exceeding the hot-rolled state (724 MPa, 12.8%). Warm rolling also triggers austenite reverted transformation (ART) and introduces high-density dislocations, further improving austenite stability. This strengthening effect is higher than that from intercritical annealing alone. Improved austenite stability delays the transformation induced plasticity (TRIP) effect, preventing brittle fracture and enhancing deformation coordination between layers, significantly increasing the plastic deformation capacity of medium Mn steel.

Molecular Dynamics Investigation of Metastable Structure and Hybridization Bond Evolution in High-Entropy CoCrFeNi Heterostructured Amorphous Carbon Films.

Heterogeneous element doping in amorphous carbon films can reduce residual stresses and improve plastic deformation. Nevertheless, the effects of dopant content and size on the metastable transition mechanism between sp2-C and sp3-C atoms during the deformation process are unclear and difficult to be in situ observed and researched, experimentally. In this work, the mechanical properties and the structural evolution during the nanoindentation of amorphous CoCrFeNi sphere-doped carbon heterostructured films with different radii were simulated. The results indicate that the hardness H and elastic modulus E of the films decreased with the increase of the dopant addition. H decreases from 50.69 to 28.94 GPa, and E decreases from 664.39 to 448.62 GPa. The decrease in the elastic recovery and the enlargement of the shear transition zones indicate that the presence of the amorphous CoCrFeNi dopant can significantly improve the plastic deformation capacity of the films. During the nanoindentation process, the spherical dopants reduce the stress and shear strain of the regions under the indenter in a-C films. The reduction of compressive and shear stresses in the film can inhibit the C atom metastable transition from sp2-C to sp3-C. This can provide a theoretical basis for the development and design of heavy-load and high-deformation-rate a-C films.

The Influence of Cyclic Loading on the Mechanical Properties of Well Cement

The cyclic loading generated by injection and production operations in underground gas storage facilities can lead to fatigue damage to cement sheaths and compromise the integrity of wellbores. To investigate the influence of cyclic loading on the fatigue damage of well cement, uniaxial and triaxial loading tests were conducted at different temperatures, with maximum cyclic loading intensity ranging from 60% to 90% of the ultimate strength. Test results indicate that the compressive strength and elastic modulus of well cement subjected to monotonic loading under high-temperature and high-pressure (HTHP) testing conditions were 14–21% lower than those obtained under ambient testing conditions. The stress–strain curve exhibits stress–strain hysteresis loops during cyclic loading tests, and the plastic deformation capacity is enhanced at HTHP conditions. Notably, a higher intensity of cyclic loading results in more significant plastic strain in oil-well cement, leading to the conversion of more input energy into dissipative energy. Furthermore, the secant modulus of well cement decreased with cycle number, which is especially significant under ambient test conditions with high loading intensity. Within 20 cycles of cyclic loading tests, only the sample tested at a loading intensity of 90% ultimate strength under an ambient environment failed. For samples that remained intact after 20 cycles of cyclic loading, the compressive strength and stress–strain behavior were similar to those obtained before cyclic loading. Only a slight decrease in the elastic modulus is observed in samples cycled with high loading intensity. Overall, oil-well cement has a longer fatigue life when subjected to HTHP testing conditions compared to that tested under ambient conditions. The fatigue life of well cement increases significantly with a decrease in loading intensity and can be predicted based on the plastic strain evolution rate.

Study on hydrogen embrittlement sensitivity of 30CrMnSiNi2A steel in electrochemical hydrogen charging

Abstract Electrochemical hydrogen charging was performed on a 30CrMnSiNi2A steel tensile sample, and the difference in hydrogen-charging effect with different hydrogen-charging times, current densities, and toxic agents was compared. The effect of hydrogen on the tensile strength, elongation and failure mode of the material was studied by the tensile test of slow strain rate. Results of the test show that hydrogen can greatly reduce the tensile strength, plastic deformation capacity, and elongation of 30CrMnSiNi2A steel, and the higher the hydrogen concentration in the material is, the more obvious the reduction will be. Hydrogen can make the failure mode of 30CrMnSiNi2A steel change from ductile failure to quasi-joint fracture and intergranular fracture.

Mechanical behavior and seismic control performance of a metallic torsional damper for flexible structures

The use of metallic dampers is an effective way to reduce seismic responses and dissipate excessive vibration energy for civil structures. Conventional metallic dampers employed energy dissipation by plastic deformation under bending or shear modes are hard to design, and may cause uniform distribution of stress in the metallic components. In this paper, employing the high plastic deformation capacity of aluminum materials, a metallic torsional damper using a gear and rack device (MTDGRD) is proposed to enhance the control effectiveness for the structural response reduction under earthquakes. The static mechanical behavior and energy dissipation of aluminum metallic components under torsional deformation are experimentally studied. Moreover, the configuration and working principle of the proposed damper are introduced. The dynamic behavior of the proposed damper is experimentally studied. For precise modeling in simulations, the elastic-plastic theory of torsional deformation is used to derive the mechanical model of the proposed damper and the model accuracy is validated by experimental data. Finally, numerical simulations under different seismic ground motions controlled by a proposed MTDGRD are compared to that controlled by a conventional tuned mass damper (TMD) for a 10-floor flexible structure. The results show that aluminum 6061# of the energy dissipation capacity is higher than aluminum 1060#. The dynamical tests show that the loading frequency and operational cycles have very limited effect on mechanical behavior and energy consumption capacity of the MTDGRD. The proposed dynamic mechanical model of the MTDGRD has considerable accuracy in numerical simulations and seismic control simulations show the better performance of the proposed damper in reducing structural displacement responses than the conventional TMD with a mass ratio of 0.5 %.

Numerical Simulation of Cluster-Connected Shear Wall Structures under Seismic Loading

The reinforced part at the bottom of high-rise assembled monolithic concrete shear wall structures generally uses cast-in-place concrete due to high elastic–plastic deformation capacity requirements, which limits the advantages of prefabricated shear wall structures. This study investigates the feasibility of using cluster connections to assemble integral shear wall structures at the bottom by modifying the vertical reinforcement of the cluster connection. Numerical simulations using ABAQUS (Version 2019) were validated with laboratory test results. The seismic performance of prefabricated shear walls with cluster connections was examined under varying axial compression ratios. Results indicate that the prefabricated shear wall demonstrates higher bearing and deformation capacity compared to cast-in-place shear walls. The degradation of strength and equivalent stiffness in prefabricated walls is slower, showing better seismic performance under higher axial compression ratios. The cluster connection ensures effective force transmission, maintaining wall integrity. After optimization, the prefabricated shear wall with cluster connection meets the expected seismic performance, providing a basis for its application in reinforced bottom sections.

Development and experimental study of a novel rotational metallic damper

As passive control technology advances and building forms become increasingly diversified, traditional axial and shear dampers may no longer meet diverse structural application requirements. This paper introduces a novel rotational metallic damper, i.e. rotational steel rod damper (RSRD), as an alternative engineering solution. The RSRD comprises three steel plates rotating around a central pin and four low yield point steel rods as energy dissipators. The input seismic energy can be dissipated in the form of plastic rotation of the RSRD. Initially, the structural form, working mechanism, and design approach of the RSRD are presented. Subsequent cyclic quasi-static tests on two RSRD specimens under varied loading protocols demonstrated satisfactory energy dissipation capacity, with an equivalent viscous damping ratio exceeding 0.47. The cyclic behavior, rotational strength, and cumulative plastic deformation capacity are discussed following the tests. A finite element (FE) analysis on the RSRD using ABAQUS is conducted to further investigate its performance. A comparison between the hysteretic behavior and failure mode of tested and simulated results is presented to validate the FE model. Additionally, two new structural forms, with linear and arc-shaped weakening on the steel rod, are simulated and compared with the original. FE results indicate that the arc-shaped weakening of the steel rod effectively avoids plastic strain concentration, showcasing superior low-cycle-fatigue performance. Finally, nonlinear time history analyses on two RC frames, with and without RSRD, reveal that structural and non-structural damage can be controlled under the maximum considered earthquake (MCE) by utilizing RSRDs.

Microstructure and Mechanical Properties of Mg-Li/Al Dissimilar Joints via Dynamic Support Friction Stir Lap Welding.

In this study, two-mm-thick dual-phase LA103Z Mg-Li and 6061 Al alloys, known for their application in lightweight structural designs, were joined using dynamic support friction stir lap welding (DSFSLW). The microstructural evolution and mechanical properties of dissimilar joints were investigated at different welding speeds. The analysis revealed two distinct interfaces: the diffusion interface and the mixed interface. The diffusion interface, characterized by a pronounced diffusion zone, is formed under slower welding speeds. The diffusion zone height, the effective lap width, and the interface layer thickness decrease with increasing welding speed due to low plastic deformation capacity and weak interfacial reactions. Conversely, the mixed interface, associated with higher welding speeds, contained large Al fragments. The extremely high microhardness values (130.5 HV) can be ascribed to the formation of intermetallic compounds (IMCs) and strain-hardened Al fragments. Notably, the maximum shear strength achieved was 175 N/mm at a welding speed of 20 mm/min. The fracture behavior varied significantly with the interface type; the diffusion interface showed enhanced mechanical strength due to better intermetallic reactions and interlocking structures, while the mixed interface displayed more linear crack propagation due to weaker IMCs and the absence of hook structures. Fracture surface analysis indicates that fractures are more likely to propagate through the Al matrix and interface layers.

Seismic cyclic test of perforated replaceable link for eccentrically braced frames

This study introduces a design comprising a unweakened link and four variants of perforated replaceable links, denoted as specimens RX1 (unweakened link), RX2 and RX3 (with circular holes of 50 mm diameter on the web), RX4 and RX5 specimens (with elliptical holes on the web), and RX6 and RX7 specimens (with weakened flanges and circular holes of 50 mm and 80 mm diameter on the web). Seven link specimens underwent cyclic loading tests. RX1 ultimately failed due to tearing of the weld at the connection between the flange and the end plate, while RX2 to RX7 exhibited deformation concentrated within the energy dissipating region, ceasing loading upon failure of this region, demonstrating enhanced safety and stability. All specimens exhibited relatively full hysteretic curves, with a decrease in the area of hysteretic curves corresponding to an increase in the web perforation ratio. The overstrength coefficient for specimen RX1 ranged from 1.81 to 1.82, while for specimens RX2 to RX7, it ranged from 1.80 to 3.65. Not only were the overstrength coefficients greater than RX1, but also the cumulative energy dissipation was higher than RX1. This indicates that RX2 to RX7 can accommodate larger plastic deformations, effectively utilizing plastic deformation for energy dissipation, thereby exhibiting superior safety. Moreover, an increase in web perforation ratio and weakening of the flanges resulted in a decrease in the overstrength coefficient, load-bearing capacity, and plastic deformation capacity of the specimens. Ductility decreased with increasing web perforation ratio but increased with flange weakening. Additionally, through analysis of link replacement time and residual rotation of links after unloading, it was observed that perforated replaceable links exhibited favorable replaceability.

Enhanced forming height and accuracy of thin-walled aluminum alloy by impact pneumatic forming

To enhance the plastic deformation capacity of hard-to-deform metal materials, the utilization of impact pneumatic forming technology is proposed for shaping complex thin-walled structures within milliseconds at room temperature. In this study, an efficient numerical simulation model is established and experiments were performed to investigate the forming height, limits, and accuracy of aluminum alloy components. The experimental results show a 21.4 % increase in the ultimate forming height when employing impact pneumatic forming as compared to quasi-static pneumatic forming. Moreover, as the initial gas pressure increases, part forming height experiences an increase but the gas compression rate experiences a decline. The simulation results reveal a maximum deformation velocity of 43.19 m/s and a limited strain rate exceeding 134 s−1, affirming the connection between increased forming height and high strain rate. Furthermore, the actual contours of parts under different gas pressures align with the simulation results, validating the reliability of the simulation. It is shown that a high gas pressure of more than 20 MPa applied for a long time can improve the forming accuracy of flat bottom and wave parts. Microstructural analysis shows that dislocations in the specimens subjected to IPF conditions are better distributed, and the dimples at the fracture sites are more pronounced. This further substantiates that the IPF process improves the plastic deformation capacity of hard-to-deform materials.