Multiple-Shot Impact Model for Vibration-Assisted SMAT Process

Surface mechanical attrition treatment enhances the mechanical properties of metallic materials by inducing high strength layer on the top surface. In this study, multiple-shot impact behavior was modeled for the 7075-T6 aluminum alloy to achieve maximum magnitudes of equivalent stress, plastic strain, residual stress depth, and residual stress. Finite element simulations have been carried out to investigate the effect of selected framework on stress and strains in constituent. The plastic deformation process during SMAT was analyzed using ANSYS/AUTODYN explicit dynamic solver according to shot velocity and diameter with a dynamic explicit finite element method (FEM). Deformation behavior was evaluated after multiple-shot impact.

Truck Synchronizer Rings Recovery by Plastic Deformation Technology

A truck's gearbox friction rings restoring process by hot 3D stamping was developed and adopted for implementation. Using this recovery method in combination with subsequent synchronizer rings mechanical processing allows restoring up to 95% resource of worn parts. It was established that section of a stamp's deforming element for axisymmetrical parts restoring should be a one-way wedge with a sloping face facing the reconstructed surface. The most significant factors influencing the transmission gearbox synchronizer rings restoring process are: stamp deforming element thickness, plunging depth and distance to a recoverable surface. The energy and force parameters study of hot plastic deformation process serves as input data for automatic design systems of working elements of stamps for restoring synchronizer rings as well as for determination of a required deforming force during hot stamping.

A Study of the Metallurgical and Mechanical Properties of Friction-Stir-Processed Cu

Friction stir processing (FSP), a severe plastic deformation process, was applied on pure Cu to obtain a stir zone with a very fine grain size. Yet, when FSP is used, the stir zone is as wide as the diameter of the shoulder at the upper surface of the weld and markedly narrower near its opposite surface. This property, as well as the differences between the advancing side and the retreating side, makes it impossible to obtain a uniform cross-section as far as the microstructure and mechanical properties are concerned. For these reasons, a new approach is proposed in which the material was processed on both sides, thus yielding a wider, rectangular and more homogenous stir zone from which all the specimens were machined out. Processing the material from both sides eliminated any microstructural difference between the upper and the lower side, at least within the gauge length’s cross-section of the creep specimens. Although grain refinement was detected, the mechanical properties of the friction-stir-processed (FSP’ed) material are inferior relative to those of the parent material. The TEM study reported in the current paper revealed the existence of nanosized grains in the FSP’ed material due to dynamic recrystallization (DRX) occurring during the processing stage. Because both X-ray inspection and fractography showed that the FSP’ed material was free of defects, the material may not comply with the Hall–Petch relation due to lower dislocation density caused by XRD occurring during FSP. The inverse Hall–Petch effect may also be considered as an assistive mechanism in mechanical property deterioration.

INFLUENCE OF A LOW-TEMPERATURE PLASTIC-DEFORMATION PROCESS ON THE MICROSTRUCTURE OF AN Al-Si-Mg ALUMINUM ALLOY

This work was planned to modify the microstructure of a solution-treated, cast Al-Si-Mg aluminum alloy by a plastic deformation method at a cryogenic temperature. It was found that cryo-rolling is an efficient low-temperature, plastic-deformation method that causes the transformation of a dendritic microstructure to an ultrafine-grained counterpart with a high dislocation density and the redistribution of hard silicon particles in the cast aluminum alloy. The results show cryo-rolling strains lead to an increment of the dislocation density because of the annihilation of the dislocations’ dynamic recovery. The microstructural refinement imposed by cryo-rolling seems to lead to a notable strength enhancement of the material because of the coupled impact of dislocation-strengthening and grain-boundary-strengthening mechanisms.

Finite Element Analysis of Large Plastic Deformation Process of Pure Molybdenum Plate During Hot Rolling

Rare molybdenum resources have been increasingly involved in heavy industries. In this paper, the common unidirectional and cross hot rolling operations, for pure molybdenum plate, are numerically simulated by using MSC. Marc software. An elastic-plastic finite element model is employed together with updated Lagrange method to predict stress and strain fields in the work-piece. The results showed that there was a typical three-dimensional additional compressive stress ( σy > σx > σz ) in deformation zone, while strain could be divided into uniaxial compressive strain and biaxial tensile strain ( Ey > Ex > Ez ). Tensile stress σx increased with the accumulation of reduction and the decrease of friction coefficient at the edge of width spread. More importantly, the interlaced deformation caused by cross commutation was helpful to repair the severe anisotropy created by unidirectional hot rolling. By comparing the theoretical verification of rolling forces and the measured temperatures with the simulated values, eventually, it is demonstrated that the model is aligning well with the actual engineering.

On the Effects of Burnishing Process on Tribological Surface Resistance of Additively Manufactured Steel

Burnishing is a Severe Plastic Deformation process having the potential to replace expensive finishing post processes. It is considered a super finishing process due to its results in terms of drastic roughness reduction. Also, additional advantages include the surface integrity improvement functionalized to the specific application. Even though burnishing is widely applied for surface improvement of conventional materials, knowledge about its effect on additively manufactured metals is still limited. This paper aims to fill this gap presenting experiments on roller burnishing on additively manufactured stainless steel in order to improve its tribological performance. The experimental campaign was carried out to find suitable process parameters able to drastically improve the tribological behavior of the final product. In particular, the influence of the burnishing forces on the whole surface quality has been addressed. The overall results demonstrate that the selected burnishing configuration is able to successfully modify the surface characteristics of the steel, making it appropriate for critical applications. Furthermore, the experimental findings allow to conclude that burnishing process can replace a series of post processes needed after additive manufacturing, drastically reducing the time and costs associated to the manufacturing process and meeting Industry 4.0 requirements.