Advances in Plastic Forming of Metals

The forming of metals through plastic deformation comprises a family of methods that produce components through the re-shaping of input stock, oftentimes with little waste. Therefore, forming is one of the most efficient and economical manufacturing process families available. A myriad of forming processes exist in this family. In conjunction with their countless existing successful applications and their relatively low energy requirements, these processes are an indispensable part of our future. However, despite the vast accumulated know-how, research challenges remain, be they related to the forming of new materials (e.g., for light-weight transportation applications), pushing the boundaries of what is doable, reducing the intermediate steps and/or scrap, or further enhancing the environmental friendliness. The purpose of this book is to collect expert views and contributions on the current state-of-the-art of plastic forming, thus highlighting contemporary challenges and offering ideas and solutions

Single point incremental forming: An assessment of the progress and technology trends from 2005 to 2015

The last decade has seen considerable interest in flexible forming processes. Among the upcoming flexible forming techniques, one that has captured a lot of interest is single point incremental forming (SPIF), where a flat sheet is incrementally deformed into a desired shape by the action of a tool that follows a defined toolpath conforming to the final part geometry. Research on SPIF in the last ten years has focused on defining the limits of this process, understanding the deformation mechanics and material behaviour and extending the process limits using various strategies. This paper captures the developments that have taken place over the last decade in academia and industry to highlight the current state of the art in this field. The use of different hardware platforms, forming mechanics, failure mechanism, estimation of forces, use of toolpath and tooling strategies, development of process planning tools, simulation of the process, aspects of sustainable manufacture and current and future applications are individually tracked to outline the current state of this process and provide a roadmap for future work on this process

Development of a post-form strength prediction model for a 6xxx aluminium alloy in a novel forming process

Accurate prediction of the post-form strength of structural components made from 6xxx series aluminium alloys has been a challenge, especially when the alloy undergoes complex thermo-mechanical processes such as the Fast light Alloys Stamping Technology (FAST). This process involves ultra-fast heating, high temperature plastic deformation, rapid quenching and is followed by multi-stage artificial ageing heat treatment. The strength of the material evolves with the formation of second phase precipitates during the entire process. The widely accepted precipitation sequence is SSSS - clusters - β” - β’ - β. However, due to the complexity of deformations and thermal profile during the process, the classic theory is not applicable. Therefore, in this research, precipitation behaviour during ultra-fast heating, viscoplastic behaviour, effect of residual dislocations generated during high temperature deformation, quenching sensitivity and multi-stage artificial ageing response have been comprehensively studied. A set of experiments, including ultra-fast heating tests, uniaxial tensile tests, pre-straining uniaxial tensile tests, quenching tests, artificial ageing tests and TEM observations were conducted to provide a thorough understanding of the novel forming technology. The underlying mechanisms for the FAST process were investigated through the in-depth analysis of experimental results. ·Under ultra-fast heating conditions, most of the precipitates are dissolved and the spherical pre-β” precipitates are formed and finely dispersed in the aluminium matrix, which are beneficial to accelerate the subsequent precipitation process. ·The residual dislocations, generated during plastic deformation, strengthen the material and act as nucleation sites for precipitates. The peak strength is reduced owing to the uneven accumulation of precipitates around dislocations. ·The coarse β’ and β precipitates induced due to the insufficient quenching are detrimental to precipitation response. These quench-induced precipitates consume both solute atoms and vacancies, which are unable to be reversely transferred to the preferred needle-shaped β” precipitates. Based on the scientific achievements, a mechanism-based unified post-form strength (PFS) prediction model was developed ab-initio to predict the strength evolution of the material during the entire complex FAST process with highly efficient computation. Constitutive equations were proposed to model the viscoplastic behaviour at elevated temperature. Important microstructural parameters, including dislocation density, volume fraction, radius of precipitates and solute concentration were correlated to predict the material strength. The particle size distribution (PSD) sub-model was further established to accurately interpret the detailed microstructural changes during the complex thermo-mechanical processes. Furthermore, the model has been programmed into an advanced functional module ‘Tailor’ and implemented into a cloud based FEA platform. The predictive capability of the module was verified by conducting forming tests of a U-shaped component in a dedicated pilot production line. It was found that the ‘Tailor’ module was able to precisely predict the post-form strength in agreement with experiments, with a deviation of less than 7% compared to experimental results.Open Acces

Constitutive Behaviour and Formability of Pre-aged AA7075 Sheet in a Warm Forming Process

Warm constitutive and formability characterization of a high strength aluminum alloy (AA7075) was performed for a range of pre-aged (i.e. under-aged) tempers, strain rates and temperatures. The pre-aging processes were composed of a solution treatment process and a natural aging period of 2 days, followed by aging at temperatures of 80, 100 and 120 C for durations of 1, 2, and 4 hours. The peak-aged T6 temper condition was also considered for comparison purposes. Warm constitutive characterization was performed at strain rates of 0.01, 0.1, and 1 s-1, and temperatures of 150, 175 and 200 C. Room temperature and warm formability tests were performed using a Nakazima [1] tooling geometry with a plane strain specimen for the same temperatures, considering a range of tooling stroke rates from 0.5-63 mm/s. The formability results were assessed utilizing limit strains based on the ISO 12004-2:2008 [2] necking detection method, as well as the measured dome heights at failure. In addition, the effect of heating rate prior to elevated temperature constitutive and formability testing was considered. The room temperature constitutive results revealed that the pre-aged tempers exhibit superior work hardening response and elongation compared to the peak-aged T6 temper. However, serrated flow, attributed to PLC effects, was observed in the flow response of the tempers with reduced/insufficient pre-aging schedules (e.g. 1 hour at 80 and 100 C pre-age schedules). This behaviour induced a negative strain rate sensitivity and reduced the repeatability of the tensile flow response and room temperature formability limits. In response to elevated temperature deformation, the T6 tensile samples exhibited clear thermal softening effects. This response, however, was accompanied by early onset of diffuse necking, although the elevated temperature strain rate sensitivity is high which results in increased elongation to failure. The pre-aged tempers, in contrast, also responded positively to the thermal softening effect and exhibited a delay in the onset of diffuse necking, compared to T6. Interestingly, the elevated temperature strain rate sensitivity of the pre-aged tempers was quite low compared to the T6 samples, part of which is attributed to aging during the lower rate (longer duration) tensile tests. The room temperature formability results revealed improvements in forming limits with the pre-aged tempers, as compared to the peak-aged T6 temper. At elevated temperatures, thermal softening resulted in higher forming limits for all evaluated tempers, with the T6 temper at 200 C having the highest limit strain, closely followed by the 100 C 4 hour and 80 C 4 hour aged tempers formed at 175 C. Interestingly, the high limit strain exhibited by the warm formed T6 temper was not fully reflected in its limit dome height, since the early onset of diffuse necking prevented a globally uniform strain distribution along the surface of the specimen. In contrast, the pre-aged tempers in contrast resulted in superior dome height limits, which is attributed to their higher extent of work hardening prior to onset of diffuse necking. Both the tensile elongation and forming limit strains were shown to decrease with test speed. Further, the faster heating rates considered in this study resulted in mildly superior forming limits, since the extent of pre-aging during heating to the warm forming temperatures was reduced. A limited study on the hardness of the warm formed specimens before and after a paint bake cycle (PBC) revealed a notable increase in hardness values in response to the PBC for all tested conditions. Interestingly, the T6 temper exhibited a mild drop in hardness following warm forming, however, the loss in hardness was largely recovered after the PBC, which may be due to retrogression and re-aging effects. For the range of initial tempers and forming conditions considered herein, the specimens heat-treated at 100 C for 4 hours, and warm formed at 175 C (utilizing the rapid heating method) resulted in one of the best overall performances. This process route (evaluated at the slow forming speeds of 1 mm/s) resulted in an increase of approximately 42% in dome height (from 19 to 27 mm), and 77% in major limit strain (from 14.5 to 25.7%), compared to the room temperature limits of the T6 temper. Moreover, the repeatability of this process route proved to be superior compared to the majority of the other under-aged processing routes. In addition, the hardness values of this pre-aged temper, following warm forming and a paint bake cycle (PBC) were within 97% of the as-received T6 temper. Finally, a numerical model was devised, using the Hockett-Sherby [3] constitutive model to fit the warm tensile data. The numerical simulations demonstrated accurate predictions for the tensile experiments and fair predictions for the warm forming experiments

Mass Production Processes

It is always hard to set manufacturing systems to produce large quantities of standardized parts. Controlling these mass production lines needs deep knowledge, hard experience, and the required related tools as well. The use of modern methods and techniques to produce a large quantity of products within productive manufacturing processes provides improvements in manufacturing costs and product quality. In order to serve these purposes, this book aims to reflect on the advanced manufacturing systems of different alloys in production with related components and automation technologies. Additionally, it focuses on mass production processes designed according to Industry 4.0 considering different kinds of quality and improvement works in mass production systems for high productive and sustainable manufacturing. This book may be interesting to researchers, industrial employees, or any other partners who work for better quality manufacturing at any stage of the mass production processes

Emerging trends in single point incremental sheet forming of lightweight metals

Lightweight materials, such as titanium alloys, magnesium alloys, and aluminium alloys, are characterised by unusual combinations of high strength, corrosion resistance, and low weight. However, some of the grades of these alloys exhibit poor formability at room temperature, which limits their application in sheet metal-forming processes. Lightweight materials are used extensively in the automobile and aerospace industries, leading to increasing demands for advanced forming technologies. This article presents a brief overview of state-of-the-art methods of incremental sheet forming (ISF) for lightweight materials with a special emphasis on the research published in 2015–2021. First, a review of the incremental forming method is provided. Next, the effect of the process conditions (i.e., forming tool, forming path, forming parameters) on the surface finish of drawpieces, geometric accuracy, and process formability of the sheet metals in conventional ISF and thermally-assisted ISF variants are considered. Special attention is given to a review of the effects of contact conditions between the tool and sheet metal on material deformation. The previous publications related to emerging incremental forming technologies, i.e., laser-assisted ISF, water jet ISF, electrically-assisted ISF and ultrasonic-assisted ISF, are also reviewed. The paper seeks to guide and inspire researchers by identifying the current development trends of the valuable contributions made in the field of SPIF of lightweight metallic materials