Simulation and automation of aluminium panel shot peen forming

We present a methodology for automated forming of metal plates into freeformshapes using shot peening. The methodology is based on a simulation softwarethat computes the peening pattern and simulates the effect of its application.The pattern generation requires preliminary experimental characterizationof the treatment. The treatment is applied by a shot peening robot. The program for the robot is generated automatically according to the peening pattern. We validate the methodology with a series of tests. Namely, we form nine aluminum plates into doubly curved shapes and we also shape model airplane wing skins. The article describes the complete workflow and the experimental results.

Effect of Microstructure Evolution and Corrosion Behavior on Phase Transformation of Nanocrystalline SUS304 Prepared by Dry Ice Shot Peening

Microstructure and corrosion behavior of nanocrystalline SUS304 by dry ice shot peening has been investigated in detail in term of phase transformation. SUS304 as metastable austenitic stainless has excellent corrosion resistance and induced martensite by shot peening process. However, the SUS304 has quite low strength which is difficult to wear as metallic component. The dry ice shot peening process was carried out on SUS304 surface for one and three hours. The microstructure was observed by transmission electron microscope (TEM) and scanning electron microscope (SEM) equipped with electron back-scattered diffraction (EBSD). The phase transformation was analyzed by X-ray diffraction (XRD). The corrosion testing was carried out in 3.5% NaCl solution. The result indicated that the grain size of SUS304 surface was finer by deformation due to dry ice shot peened process. The hardness was improved properly by the increasing the shot peened time, and the corrosion resistance was increased. The XRD results showed that three hours shot peening process induced martensite phase of SUS304 by 15 m thickness. It can be summarized that the dry ice shot peening can be induced phase transformation due to high deformation on the SUS304 surface

Load capacity of single-lap adhesive joints made of 2024-T3 aluminium alloy sheets after shot peening

The goal of the work reported was to determine the influence of selected shot peening parameters on the deflection of the Almen strip and the load capacity of single-lap adhesive joints made of 2-mm-thick aluminium alloy EN AW-2024-T3. Moreover, the research was aimed at checking the possibility of using the Almen strip deflection indicator to predict the load capacity of adhesive joints after shot peening. The analysis was carried out according to Hartley’s PS/DS-P:Ha3 plan. The input factors were the shot peening parameters: treatment time t (60–180 s), ball diameter dk (0.5–1.5 mm) and compressed air pressure p (0.3–0.5 MPa). It has been proved in this work that shot peening treatment of the outer surface of single-lap adhesive joints can be used to strengthen the joint. The maximum increase in the load capacity of the shot peened joints was 33.4%. It was observed that the load capacity of the joints decreases with an increase in the deflection of the Almen strip (in the assumed area of variability of technological parameters). Moreover, the results obtained indicate that the adoption of too intensive treatment, manifested in high values of deflection of the Almen strip, may weaken single-lap adhesive joints.

Increasing wear and corrosion resistance of steel products by combined laser thermomechanical treatment

A technique is presented for hardening metal products, in particular, the main tools (hammers) and cases of core drilling bits made of steel 30HGSA, using thermomechanical surface treatment according to a separate scheme. The method of combined laser thermomechanical hardening used in the study consists in the use of shot peening followed by laser heat treatment. Its use makes it possible to increase the operational properties of steel products, in particular, their wear and corrosion resistance. Based on the results of theoretical and experimental studies, the paper substantiates the features of dynamic surface plastic deformation for the analysis of impact during shot peening. The advantages of using laser hardening without surface melting are presented. Experimental research methods are proposed for determining the structural-phase composition, structure of the surface layer, hardness and microhardness of the hardened zones of steel 30HGSA. The range of rational modes of impact shot peening and thermal laser treatment has been determined. A device for testing samples for wear resistance has been developed. Methods of testing for wear and corrosion resistance of the surface of samples are proposed for assessing the tribological properties and contact interaction of materials under quasi-static and dynamic loading conditions. It is concluded that rational technological modes of hardening tools made of steel 30HGSA using combined laser thermomechanical treatment allow increasing the depth of the hardened layer by ~1.5 times compared to laser heat treatment. In addition, they provide the microhardness of the surface layer of ~5400 MPa, which is ~2.5 times higher than the microhardness of the base material

Numerical evaluation of the residual stresses in shot peening of alloy steels

In the present numerical study, the residual stresses generated during the shot peening process were evaluated using the finite element method. The influence of shot velocity on the residual stress distribution due to the indentation of a rigid shot over the target plate of alloy steel was studied. The finite element package ABAQUS 6.20 is used for simulating the shot peening process considering the target plate to be deformable. A parametric study was performed by introducing strain hardening rate as H1 = 800 MPa, keeping the dimension of target plate same with variation in shot velocity 20, 50, 75, 100, 125, and 150 m/s to check the behavior of residual stress distribution. As the indentation takes place over the metallic target plate, elastic-plastic deformation was observed. The indentation of the shot with a different velocity range causes the difference in the depth and size of the dent and induces the compressive residual stress. For perfectly plastic and the strain hardened material, the residual stress contour was simulated. The simulated results for strain hardened material show the significant change in the compressive residual stress in the sub-surface region of the target plate. It is evident from the results that the shot velocity has a significant effect on the residual stress distribution. The maximum compressive residual stress is achieved when the shot is indented at a velocity of 125 m/s.