Effect of a Continuous Annealing Temperature on the Microstructure, Mechanical Properties and Texture of Annealed Drawn and Ironed Plate

To improve the production process and produce high-quality annealed drawn and ironed (DI) plate, continuous annealing experiments were carried out at 620 °C, 640 °C, 680 °C, and 720 °C, and the effect of a continuous annealing temperature on the microstructure, mechanical characteristics, and texture of annealed DI plate were clarified. The microstructure was tested with a scanning electron microscope (SEM); the mechanical properties and weighted average of the plastic strain ratio (r¯) were measured using a tension test; and the texture characterizations were tested by X-ray powder diffractometer (XRD) and electron backscatter diffraction (EBSD). The results reveal that, with the increase of the annealing temperature, the average grain size grew from 5.14 μm to 6.56 μm, the yield strength and tensile strength decreased, and the elongation increased. The rolling textures drastically reduced after annealing. When annealed at a lower temperature of 620 °C, the texture content of {111} <110> was the highest. When the annealing temperature increased to 640 °C, 680 °C and 720 °C, the texture content of {111} <112> was higher than that of {111} <110>. The mechanical properties of the DI plate that was annealed at 640 °C are the best, with a higher r¯ value and a lower planar anisotropy value.

Effect of Interface on the Deep Drawability of Ti/Al Multilayered Composites

Ti/Al multilayered composites (LMCs) with different layers were prepared by hot-pressing and hot-rolling. The effects of interface on the deep drawability of LMCs were explored. The results indicate that LMCs with more layers have a higher limit-drawing ratio (LDR) and exhibit an excellent deep drawability. The texture strength of the Ti layer gradually weakens with the increase of layers, which leads to the smaller yield ratio (σs/σb), the plastic strain ratio (r), and the larger strain hardening index (n), thus the deep drawability of LMCs with more layers is enhanced effectively. The Ti/Al interfaces in three, five, and seven layers of LMCs exhibit straight, small wave-like interlocking, and dense serrated structures at the corner of the cylindrical parts, respectively. The component metals become thinner with the increase of layers, and the increased interfacial pressure promotes the formation of an increasingly firm overlapped interfacial structure. The load transfer via the interfaces makes the stress distribution between layers more uniform with the increase of layers, which helps to coordinate deformation. Deflection and tearing occur when the cracks propagate to the interface due to the complex stress state, which hinders and delays the crack penetration, thereby improving the deep drawability of LMCs with more layers.

Influence of water saturation on the strength characteristics and deformation behavior of hardened cement paste backfill

In this study, a uniaxial compression experimental was conducted to examine the mechanical properties of hardened cemented paste backfill (CPB) with different water saturations (0.18%, 4.98%, 9.30%, 21.6%, 32.8%, and 100%). The experimental results demonstrated that water saturation loosened the overall structure of the CPB, which led to the deterioration of its mechanical properties. As the water saturation increased, the uniaxial compressive strength (UCS), residual strength, strength difference, deformation modulus, secant modulus, E50 (the secant modulus at 50% of the UCS), peak strain, and elastic strain decreased, while the plastic strain ratio increased. The UCS, E50, and peak strain demonstrated exponential function relationships with the water saturation. After the peak point, when the water saturation was less than 20%, the strength of the CPB decreased rapidly, and when the water saturation was greater than 30%, the strength decreased slowly. Lastly, the plastic strain, the strain at 50% of the UCS, and the strain at the maximum secant modulus conformed to the normal distribution, and the water saturation had a minimal impact on these three strains. The fractal dimension, D, of the cracks in the CPB increased exponentially with increasing water saturation and demonstrated a negative linear correlation with the UCS.

Modeling plastic anisotropy evolution of AISI 304 steel sheets by a polynomial yield function

In this study, a numerical model for the evolution of plastic anisotropy is investigated for the purpose of stamping method design by Finite Element (FE) analysis and proved experimentally via process simulations of a cold-rolled austenitic stainless steel (AISI 304) sheet. The plastic anisotropy of the sheets is described with a fourth-order homogenous polynomial yield function and this modelling approach is enhanced by plastic strain dependent material coefficients. Tensile tests of coupon specimens taken along the different directions from rolling direction, and flow strength and deformation anisotropies are described with the planar variations of yield stress and plastic strain ratio computed at four plastic strain levels (0.002, 0.02, 0.05 and 0.18). A new numerical approach is, then, applied to identify polynomial coefficients ensuring an orthotropic positive-definite, convex yield surface with a well-defined stress gradient at every loading point on plane stress subspace. The developed computational model is implemented into general purpose explicit FE analysis software Ls-Dyna by a user-defined material model subroutine (UMAT) and applied in the stamping simulation of AISI 304 steel rectangular cups for the house-hold applications. The computed thickness distributions and the flange geometries were compared with measurements and it was observed that the best predictions were done with material parameters at %5 plastic strain level.

The Choice of Vascular Implants in Accordance with Age-Related Vessel Changes

Background Today, one of the problems of modern society in the health are the high rates of mortality from cardiovascular disease.Aim of study Study of physico-mechanical properties of the vascular implants and aortic wall to support an adequate choice of the plastic material when performing reconstructive surgeries in patients of various age groups.Material and methods As an object of study, sections of the anterior wall of the thoracic and abdominal aorta were taken from 30 corpses. Study groups: Group 1 - from 33 to 60 years, Group 2 - from 60 to 92 years. We also evaluated the physical and mechanical properties (finite length, plastic strain ratio, tensileuniaxial load (longitudinal)) of the three vascular implants made of polyethylene terephthalate and polytetrafluoroethylene. Kruskal–Wallis H test was used to determine the significance of differences.Results The finite length of the aortic wall varies slightly in the study groups, while plastic strain rate of the abdominal aorta in Group 1 was 1.3 times higher than that in the chest. When assessing physical and mechanical properties of thoracic and abdominal aorta, values of “finite length” (1.4 times) and “plastic strain ratio” (1.5 times) were higher in Group 1, and the value of the tensile load indicator is higher in Group 2 compared to Group 1 (1.47 times). The tensile load of the thoracic aorta in Group 1 is 14 H and 27 H lower than the samples of Groups 1 and 3, respectively, but 1.6 times higher than the sample of Group 2. The tensile load of the abdominal aorta of Group 1 is 13 H higher compared to the sample of Group 1 and twice higher compared to the sample of Group 2. The study Group 2 values of tensile load for thoracic aorta are 1.3 times, 2.4 times and 1.16 times higher than respective implant values (sample 1, 2 and 3, respectively).Conclusion We used samples of Group 3 vascular implants for replacement of abdominal aorta and Group 1 implants for thoracic aorta. In study Group 2 vascular implants of Group 3 may be used for abdominal and thoracic aorta replacement due to the proximity of the values of the evaluated characteristics.

Effects of Initial Precipitate on Shear Deformation during Asymmetric Rolling of Al-Mg-Si Alloy: Texture and Formability

Al-Mg-Si alloy was rolled asymmetrically at several temperatures to apply shear deformation, and the effects of the initial precipitate on shear deformation, texture evolution, formability, and plastic anisotropy were studied. Texture was analyzed using a EBSD, and the formability and plastic anisotropy of the specimen were evaluated using the value and value calculated from the plastic strain ratio (r-value) which was determined from the change in the length of the specimen during tensile deformation. Asymmetric rolling induces a larger equivalent strain than symmetric rolling, and the equivalent strain increases as the asymmetric rolling temperature increases. When a specimen with peak-aged initial precipitates was asymmetrically rolled, less shear deformation occurred at room temperature than in a solution-treated specimen without initial precipitates. In contrast, a larger shear deformation occurred at high temperatures (500°C). With asymmetric rolling at room temperature, the specimens without initial precipitates had higher formability and lower plasticity, while for asymmetric rolling at high temperature, the specimens with initial precipitates had higher formability and lower plastic anisotropy. This is due to the <111>//ND texture, such as {111}<110> and {111}<112> orientation that has similar and high r-values at 0°, 45°, and 90° to the rolling direction, developed by the shear deformation that occurred during asymmetric rolling.

Microstructure and Texture Evolution with Relation to Mechanical Properties of Compared Symmetrically and Asymmetrically Cold Rolled Aluminum Alloy

The impact of asymmetric cold rolling was quantitatively assessed for an industrial aluminum alloy AA 5454. The asymmetric rolling resulted in lower rolling forces and higher strains compared to conventional symmetric rolling. In order to demonstrate the positive effect on the mechanical properties with asymmetric rolling, tensile tests, plastic-strain-ratio tests and hardness measurements were conducted. The improvements to the microstructure and the texture were observed with a light and scanning electron microscope; the latter making use of electron-backscatter diffraction. The result of the asymmetric rolling was a much lower planar anisotropy and a more homogeneous metal sheet with finer grains after annealing to the soft condition. The increased isotropy of the deformed and annealed aluminum sheet is a product of the texture heterogeneity and reduced volume fractions of separate texture components.

Investigation on Fracture of a 6014-T4 Aluminum Alloy Sheet in the Flanging and Hemming Process Based on Numerical and Experimental Methods

The fracture of a flat-surface straight-edge hemmed component of aluminum alloy sheets was investigated in this study. The specimen was made of 1 mm thick 6014-T4. Natural aging characteristics of 6014-T4 were studied via uniaxial tensile tests. The results show that the yield stress and ultimate tensile strength increased while the uniform elongation, strain hardening exponent, and plastic strain ratio decreased during the natural aging period, which worsened the formability. The sheet was biaxially stretched to obtain a pre-strain before the flanging and hemming operation. The influence of the flanging radius on the fracture was evaluated using experimental and numerical methods, and the optimum values were obtained. The comparison between the roller hemming and die hemming process proved that the former tends to produce better formability.

Optimizing Material Parameters for Better Formability of DQ Steel Pipe

As Pipelines are subjected to bursting failure, the prediction of the burst capacities of corroded pipelines is of significant relevance to the pipeline industry. The Single mode deformation processes, most commonly used in laboratory evaluations like tensile test, may not realistically predict formability performance. Therefore, limit strains tests that use multiple deformation stages would better simulate actual material performance hence bulge test is widely used in pipeline industry for analyzing formability. The tube bulge test is an advanced testing material in which the tube is placed in a die cavity and is sealed from both the ends, the water is injected from the hole inside the sealing punch and hydraulic pressure is increased and the tube gets deformed at the center. The objective of this work is to utilize Taguchi coupled finite element computational methodology to determine the optimum material parameters to attain better formability without necking-splitting failure. To evaluate the dependence of the slope of the forming limit diagram on the material parameters, the simulation under various combinations of strain-hardening exponent (n), plastic strain ratio (r) and thickness of tube (t) is carried out and using thickness gradient criterion, the occurrence of necking i. e. forming limit strains during tube bulging is examined. By observing the optimum condition obtained for maximum plain strain it is concluded that higher the n, r and t more the limit strains will be. It is also observed that among n, r and t, n is the most prominent factor contributing on limit strains followed by r and t. The verification of optimum process parameters obtained through Taguchi technique is carried out using additive model and it is found that the observed value is well in agreement with the predicted value, the extra validation simulation is carried out to validate the Taguchi results.