The streamlined design of self-bending extrusion die Min, Fanlei; Liu, Huiping; Zhu, Guangming ...
International journal of advanced manufacturing technology,
09/2021, Letnik:
116, Številka:
1-2
Journal Article
Recenzirano
In this paper, the method of limit analysis is adopted, and three kinds of self-bending extrusion dies controlled by combined function are presented. They are the sin-atan self-bending extrusion die, ...the sin-erf self-bending extrusion die, and the sin-tanh self-bending extrusion die. Through numerical simulation, self-bending profiles can be obtained from all three kinds of dies. These dies can make the billet flow closer to the real billet flow path and maximize the billet utilization rate. They also can reduce the extrusion load and reduce the local damage of the die and then prolong the die life. It is very effective to predict the bending deformation of the billet by analyzing the central flow line of the billet. It provides a theoretical reference for the design of the actual streamlined self-bending die.
A twisted channel self-bending shunting die, a vertical shunting die, and a symmetrical streamlined shunting die were designed. The plate extrusions of these dies were simulated and experimented ...with. The experimental results show that the actual metal flow is consistent with it in the simulation. The results of the simulation show that the leftward bending plate is extruded out by the twisted channel self-bending shunting die, and the straight plate is extruded out by the other dies. The data for the welding path in the extrusion process of the three shunting dies were extracted, and the
J
values of the welding criterion were calculated. The longer the weld stability height distance above the
J
value, the wider the stable weld formation interval, the better the weld quality. The order of weld quality among the three dies is that vertical shunting die < symmetrical streamlined shunting die < twisted channel self-bending shunting die. The symmetrical streamlined shunting die and the twisted channel self-bending shunting die were simulated at different extrusion speeds, the results show that the greater the extrusion speed, the shorter the distance of the stable weld height above the junction value
J
, and the worse the weld quality of the shunting dies.
Using an integrated profile extrusion and bending forming process with a streamlined extrusion die, a new self-bending extrusion molding technology is proposed with an axis-distorted variable ...channel. By designing the streamlined extrusion die structure of the distorted central axis, the metal was made to flow non-uniformly in the die cavity, thereby directly extruding a bent profile. The central axis of the streamlined extrusion die is described by a trigonometric function and a Gaussian function. A numerical simulation was applied to analyze the metal flow pattern, equivalent strain, and strain-rate distribution during the self-bending extrusion process. The influences of the extrusion velocity and the addition of a bearing on the self-bending deformation profiles were investigated. During the extrusion process, the streamline at the center of the billet could describe the overall flow of the metal in the die cavity, and the distance between the point on the end face of the die outlet and the center of the die outlet directly determined the degree of extrusion and bending. The greater the distance was, the larger was the degree of bending. The metal strain on the convex edge of the die was greater than that on the concave edge of the die, with the extruded profile always bending toward the concave edge. The strain rate of the metal changed the fastest near the most convex point of the die. As the extrusion velocity increased or more bearings were added, the radius of curvature of the extruded profile increased nonlinearly.
•Spall failure in 7A62 high-strength aluminum alloy results from intergranular fracture.•The modified GTN model accurately predicts the impact failure mode.•Study investigates ballistic impact ...failure behavior of laminate aluminum alloy plates.
The ballistic response and failure mechanisms during the impact of a 304 steel-core projectile on a 7B52 laminated aluminum alloy plate were investigated. The impact resistance of the target plate was obtained through ballistic testing, and a detailed analysis of the fracture mechanism was conducted using microstructure characterization. Furthermore, an enhanced Gurson-Tvergaard-Needleman (GTN) model was employed to simulate the ballistic impact process, as well as the initiation and propagation of fractures. The results revealed significant deformation following the impact of the 304 steel-core projectile on the 7B52-T6 laminated plate. The target plate exhibited spalling failure, shear failure, and ductile hole expansion, with spalling failure being caused by intergranular fracture mechanisms. In the high stress triaxiality regions of the 7A62 alloy, intergranular cracks are prone to occur, and shear stress influences the expansion of the cracks. Fragments following layer cracking adhere to the 7A52 layer, thereby increasing the ballistic resistance surface area. The 7A52 layer on the rear side of the target plate effectively absorbed the projectile's energy through bending and stretching deformation, thereby offering enhanced protection. Furthermore, the spall resistance of the 7B52 laminated plate eliminate secondary damage caused by spall fragments.
•A modified Gurson-Tvergaard-Needleman (GTN) model has been established for predicting ductile fracture in high strain rate conditions for alloys.•The improved GTN model predicts results for 7xxx ...aluminum alloys consistent with Taylor impact fracture test results.•The strength of the material within the shear damage zone may experience a subsequent increase after an initial decrease.
The Gurson-Tvergaard-Needleman (GTN) model has been improved to extend its application for high strain rate loading and assessed by using the Taylor impact process of 7xxx aluminum alloys. The existing modification method based on independent shear damage variables has been integrated into the enhanced GTN model to assess shear fracture. In addition, the effects of strain rate hardening, temperature softening, and viscosity resistance terms have been taken into account in the constitutive equation to accurately depict the material’s deformation behavior under high strain rates. A series of quasi-static mechanical tests and Split Hopkinson Pressure Bar (SHPB) tests with strain rates ranging from 1000s-1 ∼ 5000 s-1 were conducted on 7A52-T6 alloy and 7A62-T6 alloy. The Taylor impact experiments showed that the mushrooming deformation and shear fractures occurred as the impact velocity increased. Both the 7A52 and 7A62 alloys exhibited fracture characteristics of shear and void nucleation, and the voids only grew slightly after formation. The predicted fracture patterns in Taylor impact and the evolution trend of material strength using the enhanced GTN model are consistent with the experimental results.
•The modified GTN model accurately predicts the impact failure mode.•Laminated plates in specific combinations can mitigate the risk of fragment impact.•The mechanism of impact failure is clarified ...through microstructural characterization.•Laminated plates enhance ballistic resistance against blunt nosed and deformable projectiles.•The laminated plate increasing the plastic deformation capacity after spalling failure.
The ballistic impact of two 7XXX aluminum alloys, 7A52-T6 and 7A62-T6, as well as their combination in a 7B52 laminate plate, was simulated and experimentally tested. Three types of projectiles were utilized hard ogival nosed, hard blunt nosed, and 304 steel core projectiles to investigate the ballistic resistance and failure mechanisms of the aluminum alloy targets. Additionally, an existing modified Gurson-Tvergaard-Needleman (GTN) model incorporating shear, void growth, and spalling failure mechanisms, was employed to simulate the ballistic impact process, utilized to analyze energy dissipation during impact. The results reveal that the 7A52 alloy only experiences ductile hole expansion failure, whereas the 7A62 high-strength aluminum alloy undergoes spalling and fragmentation subsequent to penetration, leading to potential impact hazards. Due to its backing layer being the highly ductile 7A52 alloy, the laminate plate will not produce fragments after penetration. The improved GTN model provided better predictions of the impact failure modes of the aluminum alloys. Concerning impact performance, when subjected to hard ogival projectiles, the laminate alloy did not enhance material impact resistance. However, when impacted by blunt-nosed projectiles, the laminate alloy exhibited a 27 % improvement over the 7A52 plate and an 11.9 % increase over the 7A62 plate. Furthermore, when impacted by 304 steel core ogival projectiles, the laminate alloy demonstrated over a 41.3 % improvement compared to the 7A52 plate and over a 15.5 % increase compared to the 7A62 plate. The laminate plate's high ballistic performance was attributed to the increased plastic deformation energy after spalling failure, while ensuring high energy absorption during ductile hole expansion penetration.
The crystal structure, orientation, reduced modulus, and hardness of Al3Sc single crystal were studied using X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and nanoindentation ...techniques, combined with Hertzian elastic theory method (Hertz) and Oliver-Pharr method (O&P). Millimeter-sized Al3Sc single crystals were prepared using quasi-equilibrium solidification of hypereutectic Al-15(wt %) Sc alloy. The XRD results showed that the samples were composed of L12-Al3Sc and Al phases. The EBSD and nanoindentation results showed that for five Al3Sc single crystals with different orientations, the reduced moduli measured by Hertz method were 146.6 ± 0.4–148.3 ± 0.2 GPa; while measured by O&P method they were 147 ± 2–150 ± 3 GPa. The corresponding hardnesses were varied between 3.8 ± 0.1 and 3.9 ± 0.1 GPa. The Poisson's ratio and elastic constants were determined through iterative calculation based on the relationship between the reduced modulus and Young’s modulus at various orientations. The polycrystal elastic properties, bulk modulus, shear modulus and Young's modulus, were determined. The elastic constants c11, c12, and c44 were 179.2 ± 0.4, 44.1 ± 0.1, and 68.3 ± 0.3 GPa, respectively; the Poisson's ratio was 0.196 ± 0.001. The Young's modulus of five Al3Sc single crystals oriented in different directions was in the narrow range 161–164 GPa. The anisotropy factor of Al3Sc crystal was 1.011 ± 0.002, confirming that it is elastically isotropic. These results provide fundamental information for the research and development of the Al3Sc intermetallic compound and related alloys in future.
•Millimeter-sized Al3Sc single crystals were made by quasi-equilibrium solidification.•The reduced moduli of Al3Sc single crystals were measured by nanoindentation.•The elastic constants and Poisson’s ratio were determined by iterative calculation.•The elastic properties of Al3Sc single crystals are determined to be isotropic.
► A novel polysaccharide isolated from Acanthopanax senticosu. ► The characterisation was characterised. ► Demonstrated that had stronger immunomodulatory and antioxidant activities.
A water-soluble ...polysaccharide obtained from Acanthopanax senticosus leaves (ASL), was fractionated by DEAE–Sepharose fast-flow column chromatography, and purified by Sephadex G-75 gel-permeation column chromatography. The characteristics of ASP-2-1 were determined by chemical analysis, high-performance capillary electrophoresis (HPCE), high-performance gel-permeation chromatography (HPGPC). The results show that ASP-2-1 contained 89.47% carbohydrate, 7.45% uronic acid, 2.16% protein and seven kinds of monosaccharides including rhamnose, xylose, glucose, mannose, arabinose, galactose and glucuronic acid in a molar ratio of 7.45:18.63:25.15:0.93:8.35:2.79:5.69, with an average molecular weight of about 14,573Da. Furthermore, the immunobiological and antioxidant activities, in vitro, of ASP-2-1 were evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and ferric-reducing antioxidant power assay (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH), superoxide radical (O2-) and hydroxyl radical (OH) free radical-scavenging assay, respectively. The results showed that ASP-2-1 exhibited significantly higher immunomodulatory activities against the lymphocyte proliferation in vitro, pronounced reductive power (FRAP value: 785.1μM at 0.2mg/ml), strong hydroxyl radical (89.56% at 1mg/ml) scavenging activity, moderate superoxide radicals (65.32% at 1mg/ml) and DPPH radicals (68.9% at 1mg/ml) scavenging activities. ASP-2-1 should be explored as a novel and potential natural antioxidant and immunostimulating agent for use in functional foods or medicine.
