Deviations between FE Simulation and Experiments in the SPIF Process

Single point incremental forming of Ti-6Al-4V titanium alloy for biomedical applications: Process optimization and in vitro biocompatibility assessment.

Single point incremental forming (SPIF) process has proven benefits in terms of formability, flexibility, and low cost as compared to conventional sheet forming, although it has some issues such as dimensional accuracy and low quality of surface finish for some materials. The SPIF is considered as a potential method of producing customised medical parts such as craniofacial implants using a titanium sheet. This investigation aims to analyse the overall surface roughness of grade 1 pure titanium along the wall of the hyperbolic truncated cone formed by the SPIF process with different forming parameters (i.e. forming tool diameter, step size, and feed rate). Focus variation microscopy was used to measure the surface roughness experimentally along the wall of the truncated cone. Abaqus/Explicit was used to predict the equivalent stress and equivalent plastic strain along the wall of the truncated cone part from the top to the fractured region to evaluate the relationship between the stress, strain, and roughness distribution. It was found that the surface roughness changes with the deformed part height and rough surface could be produced in the region of high equivalent stress and low equivalent plastic strain. Such a surface roughness and equivalent stress and plastic strain correlation has a clear implication to the design and the surface quality of sheet parts made by SPIF.

Evaluation of forming forces in ultrasonic incremental sheet metal forming

Investigations on failure-to-fracture mechanism and prediction of forming limit for aluminum alloy incremental forming process

The present paper aims to study the behavior of tailor welded blanks subjected to a single point incremental forming (SPIF) process from an experimental point of view. This process was chosen to deform truncated cone shapes of AA1050 aluminum alloy with different thicknesses. A uniaxial tensile test was performed to determine the mechanical characteristics of the alloy. Initial experimental tests implicated the use of variable wall angle parts which were processed on unwelded sheet blanks for determination of the behavior of the material and the forming forces. Afterwards, the wolfram inert gas (WIG) welding technique was used for joining two sheet blanks with different thicknesses either through one pass on one side, or by one pass on both sides. The conclusion of this paper indicates that one-sided welded blanks cannot be deformed successfully without fracture. In case of two-sided welded blanks, the results showed that the desired depth of 25 mm can be reached successfully. In case of the SPIF process, if welded blanks must be deformed, then the suitable method is to weld the blanks on both sides.

Metal forming process is one of the most important manufacturing processes that translate the sheet and bulk metal to the final product with simple punch and. Single point incremental forming (SPIF) process is considered as a modern flexible manufacturing techniques that is use a simple tool and non-specific fixture die to complete the forming, this method is used in prototype manufacturing system due to the time consuming during the forming. The advantage of this process is low cost and simple equipment. However, some limitation was founded including poor geometric accuracy, non- uniform thickness distribution, dimple and high forming time. Multi-point forming (MPF) is another modern forming method that is used in industrial applications due to its advantage such as uniform thickness distribution with low forming time consuming. This method used matrix of simple tools to deform the sheet metal to the desired shape. Wrinkle and dimple due to small contact area between tool and blank under high forming force are considered the main limitation of using MPF process. To take the advantages of this processes with reduced the limitations a hybrid forming (HF) process of both MPF and SPIF are used. The experimental work was applied to produce a hemi-spherical product of brass blank using the SPIF, MPF, and HF processes. Satisfactory results are obtained using a hybrid forming process with free of defects products and reduction in production as compared to the SPIF. A high improve in microstructure including refinements in grain size with twins effects. The sample produced with SPIF process showed a high microhardness as compared to the sample produced using MPF process, however, the hybrid MPF and SPIF forming process showed slightly improving in microhardness as comparing to the as received materials, reflecting the microstructure development of the processed samples.

In this work, the forming behavior of the High Strength Low Alloy (HSLA) 420 steel sheet during the Single Point Incremental Forming (SPIF) process was investigated. The formability is enhanced by increasing the spindle rotational speed, reducing the tool feed and reducing the incremental step-down. A numerical simulation was also performed and the results were compatible with experimental results. The studies are further extended to microstructural analyses. A large dislocation density was obtained due to a high swiveling effect. Therefore, the possibilities of high-angle grain boundaries were increased, which caused an increase in the percentage of ultra-fine grain formation. Hence, the strong texture was obtained by increasing the swiveling effect and the texture components were favored to enhance the formability.

Investigation of mode-I fracture behavior by essential work of fracture during the single-point incremental forming process

Forming a metallic sheet along with the consideration of computer simulation and experiment had benefited the milling industry for a long time. The ideal forming, without an error, is a concerning topic. So, the computer simulation had the advantage then direct forming. To observe the results before doing the real experiments simulation comes handy. Which helped to set the parameters for the milling process for the single point incremental forming (SPIF) process. For milling, a CAD design was converted into a 3D model. For this, a conical shape of 3D modeling was made in fusion 360. After onwards, it was simulated for finding the maximum depth for the cracking point. Next for the experimental part, the maximum forming depth was considered, and used lubricant grease for reducing friction. While forming with the grease, the impact of parameters was also changed. Throughout the process, an optimization approach was set to reduce the cracking areas for the G-code. Along with the lubricant use, smooth milling finished surface was observed. To reducing the depth forming errors, an optimization approach was introduced in this research.

Single point incremental forming (SPIF) is a decent potential procedure appropriate for small batch production. In addition to that, the formability of the material is expanded compared to the other sheet metal forming processes. Meanwhile, the more advanced SPIF process requires perfect comprehension of the material deformation technique. In this paper, the equipment of vibration - sheet metal forming was designed. Finite element model was used to demonstrate and analyze the effect of different frequencies of vibration on the strain distribution in single point incremental forming process. The results show that specific vibration parameters can decrease strain. Moreover, an experimental vibration system using single point incremental forming was designed. The numerical model is primarily supported by test results conclusions from a simple cone of Al1050 aluminum alloy.

In the Tailor-Welded Blanks (TWBs), higher strength or higher stiffness is achieved only at critical areas wherever it is necessary. Many researchers earlier concentrated on TWBs made from steel and its high-strength alloys. Recently, the use of Aluminum alloys has attracted automotive sector in last decade resulted in more research work. In the present study, forming behavior of TWBs made from aluminum alloy AA5052-H32 and AA6061-T6 is studied. TWBs are prepared by joining these two materials with TIG welding technique. These blanks are formed by Single Point Incremental Forming (SPIF) at different wall angles between 40° and 70° with difference of 5°. Formability of the TWBs and parent materials is measured in terms of forming depth, major strain, and thickness strain. The forming result reveals that forming depth of TWBs is achieved up to 12 mm which found to be deteriorated as compared to the forming depth achieved for parent materials (52 mm depth). Further, to find the reason behind this deterioration of TWBs, Slow Strain Rate Tests (SSRTs) are performed for welded portion under very slow straining of 0.0017 mm/min (2.8 × 10–8 m/s) in air environment. It is observed from the SSRT results that the weld portion and parent blank have shown brittle failure and ductile failure, respectively. This brittle nature of weld is due to the deterioration of TWBs during SPIF process. The proper heat treatment after TIG welding may increase the formability of TIG-welded TWBs.

ABSTRACTA novel configuration of bilayer composite sheets containing different polymers is described and used for the first time in the single point incremental forming (SPIF) process. These bilayer sheets made of polypropylene (PP) and Santoprene are fabricated by hot welding, and shaped with cone‐like geometry by SPIF. The bilayer configuration is such that only one of the containing polymers is in contact with the forming tool. During the SPIF processing, the bilayer sheets show a noticeable difference in the mechanical response, depending mainly on the polymer that is not in contact with the forming tool, which is related to a lower polymer softening. The performance of the bilayer sheets is compared against the neat polymers and a blend of these with a mass ratio of 1:1. The observed effect is introduced as a dual effect of properties that brings together in a single composite sheet, properties for a better performance in SPIF and wider functionality of the fabricated parts, evidenced by a lower material softening and higher mechanical strength, in comparison with the two individual polymers, and even better than the blend of both. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47093.

Single point incremental forming (SPIF) is an emerging application in sheet metal prototyping and small batch production, which enables dieless production of sheet metal parts. This research area has grown in the last years, both experimentally and numerically. However, numerical investigations into SPIF process need further improvement to predict the formed shape correctly and faster than current approaches. The current work aims the use of an adaptive remeshing technique, originally developed for shell and later extended to 3D “brick” elements, leading to a Reduced Enhanced Solid-Shell formulation. The CPU time reduction is a demanded request to perform the numerical simulations. A two-slope pyramid shape is used to carry out the numerical simulation and modelling. Its geometric difficulty on the numerical shape prediction and the through thickness stress behaviour are the main analysis targets in the present work. This work confirmed a significant CPU time reduction and an acceptable shape prediction accuracy using an adaptive remeshing method combined with the selected solid-shell element. The stress distribution in thickness direction revealed the occurrence of bending/unbending plus stretching and plastic deformation in regions far from the local deformation in the tool vicinity.

Manufacturing processes, as used for discrete part manufacturing, are responsible for a substantial part of the environmental impact of products, but are still poorly documented in terms of environmental footprint. A thorough analysis on the causes affecting the environmental impact in metal forming processes, especially the innovative but very energy intensive sheet metal forming technologies required to form light-weight products, is nowadays necessary. Therefore, this paper presents an energy consumption analysis, including a power and time study, of Single Point Incremental Forming (SPIF) processes. First, the influence of the most relevant process parameters (e.g. feed rate, step down) as well as the material forming itself are analysed regarding the power demand. Moreover, a comparative study and related energy efficiency assay are carried out on two different machine tools. As the forming time proves to be the dominant factor for the total energy consumption, from environmental point of view, the overall results show many similarities with conventional machining processes. Finally, this paper reports on some potential improvement measures to reduce the SPIF energy consumption.

The failure strain level in a single point incremental forming (SPIF) process is found to be much higher than that in the traditional stamping process. Based on the assumption that forming limits in SPIF are dominated by fracture failure, the Oyane ductile fracture criterion is introduced in this paper to predict the fracture initiation site, and hence the forming limit, given the stress and strain values obtained from finite element simulations. The predicted results compare well with those obtained from the SPIF experiments. Furthermore, this fracture criterion is used to study the size effects in SPIF. Analytical equations are derived to comprehensively consider the effects of design and process parameters on sheet formability including sheet thickness, tool diameter, and incremental depth. Previously published experimental data is used to verify the feasibility of the proposed size effect equation.