Plastic deformation behavior and constitutive modeling of Cu-50Ta alloy during hot compression

This paper presents a study on plastic deformation behavior of Cu–50Ta alloy at temperatures of 286–473 K and strain-rate of 0.01–6200 s−1. The effects of temperature, strain-rate, and strain on the yield strength, flow stress, and strain-rate sensitivity coefficient were determined. A phenomenological model was established to predict variation of the strain-rate sensitivity coefficient for Cu–50Ta alloy under dynamic compression. A Johnson–Cook constitutive model was established to predict the equivalent stress–equivalent plastic strain relationship under extreme deformation (high temperature and strain-rate). The results showed that the plastic deformation behavior of Cu–50Ta alloy was affected by temperature, strain-rate, and strain. The material exhibited obvious strain-rate strengthening and thermal softening. As the strain-rate increased, the yield strength logarithmically increased. At a temperature of 286 K, the strain-rate increased from 0.01 s−1 to 6200 s−1, and the yield strength increased from 543.75 MPa to 881.13 MPa. In addition, the yield strength linearly decreased as the deformation temperature increased. Under conditions of dynamic deformation, the variation of strain-rate sensitivity coefficient could be expressed as a function of strain-rate and strain. The phenomenological model accurately described the variation of the strain-rate sensitivity coefficient of Cu–50Ta under dynamic deformation conditions. The Johnson–Cook constitutive parameters, calibrated by experimental data, described the plastic deformation behavior of the alloy under high-velocity impact.

Finite-Element Modelling of Double-Roller Clamping Spinning of Wind Concentrator

In order to improve the unit-power of a wind-driven generator, a wind concentrator with complex shape is installed in front of the impeller, which makes the airflow integrated and accelerated. It is important to manufacture the wind concentrator with high precision. The double-roller clamping spinning (DRCS) is a dieless, flexible spinning process that is very suitable for forming a wind concentrator with complex shape. The profile of a wind concentrator is divided into two parts: the contraction section and the expanding section. The process routes of both the contraction section and the expanding section are determined, and roller path equations are derived. Then the finite element (FE) analysis model that can describe the plastic deformation behavior of the DRCS forming for a wind concentrator is established, and the DRCS process of the flange is simulated. Furthermore, the wall-thickness distribution on the expanding section during the forming process is obtained. Finally, the reliability of the FE model is verified using the experimental results.

Investigation on the Influence of Weld Position on the Deformation Behavior of Welded Tube During Free Bending Process

The non-uniform distribution of the mechanical properties of welded tube would affect the plastic deformation behavior of tube during the free bending process. To explore the influence of weld position on the forming quality and axis dimensional accuracy of welded tube, the free bending experiment and numerical simulation of welded tube were conducted in this paper. First, the principle of free bending was theoretical deduced and the stress distribution of bent tube was analyzed. Then the hardness test and uniaxial tensile test were conducted to obtain the mechanical properties of weld zone and parent zone of welded tube. The material strength in the weld zone of welded tube is significantly higher than that in the parent zone. Finally, the free bending experiment and numerical simulation with different weld position were carried out, and the influence of weld position on the bending radius, cross-sectional distortion and wall thickness of bent tube was discussed. All these findings advance the insight into the free bending deformation behavior of welded tube and help to improve the forming quality of welded tube and facilitate the application of free bending technology in welded tube.

Numerical study on the plastic deformation behavior of AZ31 magnesium alloy under different loading conditions

Based on the stress characteristics of the instantaneous cross-section deformation of the wall reducing section during the cold rolling of two-roll Pilger pipes, the rectangular samples with 0° and 90° to the extrusion direction (ED) were cut from the extruded AZ31 magnesium alloy bar for 3% pre-deformation test to simulate its stress state equivalently. The sample was then cut from the pre-deformed sample by wire cutting for secondary compression, and the sample that is not pre-deformed is selected. The mechanical behavior and texture evolution of AZ31 magnesium alloy under different loading conditions were respectively studied by EBSD experiment and VPSC simulation. Results show that the true stress–strain curve and texture evolution characteristics of AZ31 magnesium alloy during the secondary compression process are in good agreement with the prediction of the VPSC model. The secondary compression behavior can be effectively explained by the relative activity of the deformation modes. The pre-deformation in the ∥ED (⊥ED) direction is conducive to the shift of the pole density of the {0001} basal surface texture to the positive and negative directions of the ED (TD). The pre-deformed sample exhibits a higher yield strength than the non-pre-deformed sample in the same loading direction. The high ductility of magnesium alloys can be achieved by activating pyramidal 〈c + a〉 slippage.

A New Method of Manufacturing Thin-Walled Tube Made of AZ61 Magnesium Alloy Including Direct Extrusion And Corrugated Equal Channel Angular Extrusion

Due to demand of strong toughness of thin walled tube, and good secondary forming properties and high-precision dimension, New plastic forming method should be researched to achieve a complete filling, uniform deformation and microstructure evolution during forming process.To obtain the deformation mechanisms of a new composite extrusion for thin walled tube fabricated by tube corrugated equal channel angular extrusion has been researched which is shorten as “TC-ECAE” in this paper. Finite element DEFORMTM-3D software to investigate the plastic deformation behavior of magnesium billet during TC-ECAE process has been employed. Computed parameters including workpiece material characteristics and process conditions have been taken into consideration. The pridictions of strains distributions and damage distributions and effective stress distributions and flow velocities distributions and microstructures evolutions have been explored. The results proved that the TC-ECAE process is a forming method for magnesium alloy tube which is suitable for large scale industrial application. The TC-ECAE process would cause serve plastic deformation and improve the dynamic recrystallization of magnesium alloy during TC-ECAE process.

Programmed Plastic Deformation in Mathematically-Designed Architected Cellular Materials

The ability to control the exhibited plastic deformation behavior of cellular materials under certain loading conditions can be harnessed to design more reliable and structurally efficient damage-tolerant materials for crashworthiness and protective equipment applications. In this work, a mathematically-based design approach is proposed to program the deformation behavior of cellular materials with minimal surface-based topologies and ductile constituent material by employing the concept of functional grading to control the local relative density of unit cells. To demonstrate the applicability of this design tactic, two examples are presented. Rhombic, and double arrow deformation profiles were programmed as the desired deformation patterns. Grayscale images were used to map the relative density distribution of the cellular material. 316L stainless steel metallic samples were fabricated using the powder bed fusion additive manufacturing technique. Results of compressive tests showed that the designed materials followed the desired programmed deformation behavior. Results of mechanical testing also showed that samples with programmed deformation exhibited higher plateau stress and toughness values as compared to their uniform counterparts while no effect on Young’s modulus was observed. Plateau stress values increased by 8.6% and 13.4% and toughness values increased by 5.6% and 11.2% for the graded-rhombic and graded-arrow patterns, respectively. Results of numerical simulations predicted the exact deformation behavior that was programmed in the samples and that were obtained experimentally.