Effect Of Deformation Modes Research Articles

New manufacturing process of cylindrical body products with thickened edge part

The manufacturing process of body products by combining the operations of reverse extrusion and simultaneous formation of thickening at the edges of the workpiece is considered. The simulation of the operation is performed, during which the effect of deformation modes on forces and stress-strain state is determined. According to the results of the study, rational parameters of the process are identified.

Effect of deformation modes on continuous dynamic recrystallization of extruded AZ31 Mg alloy

Herein, uniaxial compression experiments, with a series of true strains at different temperatures (573–673 K) and strain rates (3 ×10−3 - 3 ×10−1 s−1), are conducted on AZ31 magnesium alloy with different initial textures. The deformation modes and dynamic recrystallization (DRX) behavior are investigated using electron back-scattered diffraction /transmission electron microscopy and crystal plasticity finite element modeling (CPFEM). A unitive constitutive equation is established for different initial textures, and the activation energies of extrusion direction (ED) and transverse direction (TD) samples are found to be 134.5 kJ/mol and 138.4 kJ/mol, respectively. The microstructural investigations and CPFEM simulations are performed to identify the characteristics of DRX processing during compression and categorize according to the deformation modes originating from the difference in initial texture of alloy. Moreover, it is revealed that basal<a> slip prevails in the TD sample at all strain rates under consideration, whereas prismatic<a> slip dominates the initial deformation of the ED specimen. Consequently, more pronounced kink bands and superior compressed peak stress are observed, corresponding to the higher density of prismatic<a> slip in the ED sample than that in the TD sample. Accordingly, these kink bands along with elevated deformation energies accelerate the development of an early continuous dynamic recrystallization with a higher volume fraction and a smaller grain size of the ED sample compared to the TD specimen. The improvement in strength and ductility of the ED sample after being deformed at a strain of 1.2 is attributed to the smaller grains and the weaker texture than those of the TD specimen. For the first time, the role of prismatic slips and kink bands in the recrystallization process is discussed in detail.

Effect of deformation modes and heat treatment on microstructure and impact property restoration of internal crack healing in SA 508 steel

In this study, the effects of deformation modes and quenching and tempering (Q&T) process on the crack healing and percentage recovery of impact properties were studied. The microstructure, Charpy impact properties and fracture surface morphology of the crack zones at different healing stages were evaluated. When the healing temperatures was 950 °C and 1050 °C, percentage recovery of impact properties of the internal crack healing by multi-pass thermal deformation (twice upsetting and once drawing) was lower than that by uniaxial compression. After deformed by twice upsetting and once drawing at 1150 °C, the ‘Z type’ newly formed grain belt was observed in the crack healing zone, which showed high resistance to the dynamic load. After Q&T process, the microstructure was evolved into the tempered bainite, and residual austenite decomposed gradually to carbides, precipitating out mainly along the grain boundaries. After Q&T process, the impact toughness of the crack healing zones were improved, but the percentage recovery decreased, it is because that in the crack healing zone, the carbides aggregated in the line, which has a lower resistance to applied force than the matrix.

Elastic constants and phonon dispersion relation analysis of graphene sheet with varied Poisson's ratio

Through the achievement of elastic parameter equivalence by the structural mechanics method, the beam–truss space frame model for graphene sheet has been simplified; moreover a representative unit cell of the periodic graphene structure has been extracted. On this basis, the Bloch theorem is combined with the finite element method to determine the phonon dispersion relation of graphene. For the widely used thickness values of the carbon–carbon (C–C) bond, the aspect ratios (thickness/length) are so large that the shear deformation should be considered such that as a result, the negative Poisson's ratio (NPR) characteristic of the C–C bond is observed. Analytical expressions for the elastic constants of graphene sheet have been obtained with varied C–C bond Poisson's ratios. The reasonable coherence with previous results reveals the effectiveness of the structural mechanics method for analysing the mechanical properties of nanostructures. The effect of deformation modes on the phonon dispersion relation of graphene sheet is further discussed; it is concluded that the acoustic phonon modes are sensitive to the deformation modes of the C–C bond, whereas these deformation modes negligibly influence the optical phonon modes. The numerical results also reveal that the shear deformation and the resulting NPR effect play an important role in the mechanical property analysis of graphene sheet. To summarise, the interrelation between NPR materials and nano materials has stimulated a wide field of research; moreover, numerous novel phenomena have been observed.

Crushing response of square aluminium column filled with carbon fibre tubes and aluminium honeycomb

Experimental and numerical evaluation is performed on a square hollow aluminium column, an aluminium honeycomb filled column, an aluminium column filled with combined carbon fibre and an aluminium honeycomb at constant velocity of 3.06 mm/s to analyze the axial crushing phenomenon at low speed axial loads. To validate experimental outputs, numerical simulation is performed using PAMCRASH explicit finite element code. The effects of honeycomb core and carbon fibre reinforced aluminium honeycomb were analysed experimentally and numerically. A decent agreement between experimental and numerical results is observed. The effects of deformation modes and force-displacement curves on these different structural columns were studied. Experimental and numerical results showed the square aluminium column filled with carbon fibre reinforced aluminium honeycomb was the most crashworthy combination, where the maximum increase of energy absorption, specific energy absorption and crush force efficiency were up to 60.6%, 27.8% and 17.4% respectively, compared with bare aluminium hollow column.

Effects of deformation modes on texture evolution during hot working of Al-Zn-Mg-Cu-Zr alloy

Deformation modes have strong effects on deformation textures and subsequent annealing textures during hot working of metals. Micro-textures and macro-textures during hot axisymmetric and planar compressive deformation and subsequent annealing processes of Al-Zn-Mg-Cu-Zr alloy were investigated by EBSD and XRD respectively. The EBSD testing indicated that for the axisymmetric compressive deformation, Brass along the α-fiber and Goss present in the sample deformed at 350 °C, Rotated-Cube was present and Brass transformed to Goss along α-fiber after annealing; Rotated-Cube appeared only in the deformation at 420 °C, which decreased and Brass appeared after annealing. For the planar compressive deformation, Rotated-Cube and Brass aligned to α and β fibers present in the deformation at 350 °C, Rotated-Cube texture transformed to Brass along the α-fiber after annealing; Rotated-Cube and Brass were present in the deformation at 420 °C, and the Rotated-Cube was enhanced and Brass transformed to Goss after annealing. Shearing textures dominated on the surface of the specimen. XRD testing showed that Rotated-Cube and a few Goss dominated in the thick-plates formed by upsetting and drawing, which transformed to Cube after annealing; However, Brass and Cube textures present in the thick-plates formed by rolling besides Rotated-Cube and Goss textures, which remained in the plates after annealing.

Efficient force prediction for incremental sheet forming and experimental validation

Incremental sheet forming (ISF) has been attractive during the last decades because of its greater flexibility, increased formability and reduced forming forces. However, traditional finite element simulation used for force prediction is significantly time consuming. This study aims to provide an efficient analytical model for tangential force prediction. In the present work, forces during the cone-forming process with different wall angles and step-down sizes are recorded experimentally. Different force trends are identified and discussed with reference to different deformation mechanisms. An efficient model is proposed based on the energy method to study the deformation zone in a cone-forming process. The effects of deformation modes from shear, bending and stretching are taken into account separately by two sub-models. The final predicted tangential forces are compared with the experimental results which show an average error of 6 and 11 % in respect to the variation of step-down size and wall angle in the explored limits, respectively. The proposed model would greatly improve the prediction efficiency of forming force and benefit both the design and forming process.