Investigation of Thermal-Related Effects in Hot SPIF of Ti–6Al–4V Alloy

The present work focuses on a new approach to hot form hard-to-work materials by Single Point Incremental Forming (SPIF) technology using a global heating of the sheet. A set of trials was carried out in order to identify the optimum temperature cycles to minimize geometric distortions associated to each process stage on the fabrication of parts made of Ti–6Al–4V. On the one hand, heating trials allowed defining the optimal procedure to improve the temperature distribution homogeneity along the sheet and consequently to minimize its thermal distortion previous to the forming stage. On the other hand, the influence of both working temperature and the applied cooling on the geometric accuracy was evaluated by means of SPIF trials. For this purpose, a generic asymmetric design with typical aeronautical features was used. These trials pointed out that high forming temperatures allow reducing significantly the material springback whereas a controlled cooling (with an intermediate stress relief treatment) minimizes both the distortion of the part during the cooling and the mechanical stresses accumulated on the clamping system. Furthermore, the work includes a post-forming material evaluation to determinate the influence of the employed processing conditions on microcracks, alpha-case layer, microstructure and hardness.Research leading to these results was done within the project INMA—Innovative manufacturing of complex titanium sheet components. This project has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no. 266208

Accuracy and Surface Quality Improvements in the Manufacturing of Ti-6Al-4V Parts Using Hot Single Point Incremental Forming

The present work focuses on the manufacturing of Ti-6Al-4V parts using hot single point incremental forming (SPIF), a non-conventional forming technology mainly oriented toward the fabrication of prototypes, spare parts, or very low volume series. In the used procedure, the entire sheet is heated and kept at uniform temperature while the tool incrementally forms the part, with the limited accuracy of the obtained parts being the major drawback of the process. Thus, this work proposes two approaches to improve the geometric accuracy of Ti-6Al-4V SPIF parts: (i) correct the tool path by applying an intelligent process model (IPM) that counteracts deviations associated with the springback, and (ii) skip overforming deviations associated with the deflection of the sheet along the perimeter of the part based on a design improvement. For this purpose, a generic asymmetric design that incorporates features of a typical aerospace Ti-6Al-4V part is used. The results point out the potential of both solutions to significantly improve the accuracy of the parts. The application of the IPM model leads to an accuracy improvement up to 49%, whereas a 25.4% improvement can be attributed to the addendum introduction. The geometric accuracy study includes the two finishing operations needed to obtain the part, namely decontamination and trimming.Research leading to these results was done within the project INMA—Innovative manufacturing of complex titanium sheet components. This research was funded by the European Union´s Seventh Framework Programme for research, technological development, and demonstration under grant agreement number 266208

High-Temperature Mechanical Properties of IN718 Alloy: Comparison of Additive Manufactured and Wrought Samples

Wire Arc Additive Manufacturing (WAAM) is one of the most appropriate additive manufacturing techniques for producing large-scale metal components with a high deposition rate and low cost. Recently, the manufacture of nickel-based alloy (IN718) using WAAM technology has received increased attention due to its wide application in industry. However, insufficient information is available on the mechanical properties of WAAM IN718 alloy, for example in high-temperature testing. In this paper, the mechanical properties of IN718 specimens manufactured by the WAAM technique have been investigated by tensile tests and hardness measurements. The specific comparison is also made with the wrought IN718 alloy, while the microstructure was assessed by scanning electron microscopy and X-ray diffraction analysis. Fractographic studies were carried out on the specimens to understand the fracture behavior. It was shown that the yield strength and hardness of WAAM IN718 alloy is higher than that of the wrought alloy IN718, while the ultimate tensile strength of the WAAM alloys is difficult to assess at lower temperatures. The microstructure analysis shows the presence of precipitates (laves phase) in WAAM IN718 alloy. Finally, the effect of precipitation on the mechanical properties of the WAAM IN718 alloy was discussed in detail.This project received funding from the European Union’s Marie Skłodowska–Curie Actions (MSCA) Innovative Training Networks (ITN) H2020-MSCA-ITN-2017 under the grant agreement No. 764979 and Basque Government QUALYFAM project, ELKARTEK 2020 program (KK-2020/00042) and HARIPLUS project, HAZITEK 2019 program (ZL-2019/00352)

Review of Intermediate Strain Rate Testing Devices

Materials undergo various loading conditions during different manufacturing processes, including varying strain rates and temperatures. Research has shown that the deformation of metals and alloys during manufacturing processes such as metal forming, machining, and friction stir welding (FSW), can reach a strain rate ranging from 10−1 to 106 s−1. Hence, studying the flow behavior of materials at different strain rates is important to understanding the material response during manufacturing processes. Experimental data for a low strain rate of 103 s−1 are readily available by using traditional testing devices such as a servo-hydraulic testing machine and the split Hopkinson pressure bar method, respectively. However, for the intermediate strain rate (101 to 103 s−1), very few testing devices are available. Testing the intermediate strain rate requires a demanding test regime, in which researchers have expanded the use of special instruments. This review paper describes the development and evolution of the existing intermediate strain rate testing devices. They are divided based on the loading mechanism; it includes the high-speed servo-hydraulic testing machines, hybrid testing apparatus, the drop tower, and the flywheel machine. A general description of the testing device is systematically reviewed; which includes the working principles, some critical theories, technological innovation in load measurement techniques, components of the device, basic technical assumption, and measuring techniques. In addition, some research direction on future implementation and development of an intermediate strain rate apparatus is also discussed in detail.This project received funding from the European Union’s Marie Skłodowska–Curie Actions (MSCA) Innovative Training Networks (ITN) H2020-MSCA-ITN-2017 under the grant agreement No. 76497

Influence of flute number and stepped bit geometry when drilling CFRP/Ti6Al4V stacks

Hybrid stacks made of carbon reinforced plastic (CFRP) and Ti-6Al-4 V alloy (Ti) are often drilled together to reduce positional errors, enhance tight tolerances and minimize machining time. However, this is a complex task due to the dissimilar properties of each material. Tool geometry has a significant impact on the machinability of CFRP/Ti stacks. In this study, the influence of flute number and stepped bit design was experimentally investigated. Confocal and SEM microscopy were used to analyse the evolution of the cutting-edge micro-geometry and the dominant wear modes. The results have shown that a stepped design with three flutes leads to a slower wear progression, lower cutting forces and less hole damage. Furthermore, this paper also highlights the influence of the geometrical characteristics of the stepped tool design on the drilling stage number and on the shape of the thrust force signal. The information gathered can be used for the improvement of the process competitiveness in terms of the reduction of production time and cost

Quality monitoring of blind fasteners installation: An approach from the manufacturing chain and visual analytics

Fastening is a recurrent assembly operation at the aerospace industry. Among the many different types of fasteners being used blind ones offer particular advantages but there is yet a lack of reliable installation monitoring methods for their massive adoption. The present paper proposes an installation evaluation solution for blind fasteners that integrates the effect of the previous drilling operation and allows the visualization of the relationships between hole quality parameters, installation variables and installation quality. The results show high precision values of 0.95 and accuracy of 0.9

Accuracy and Surface Quality Improvements in the Manufacturing of Ti-6Al-4V Parts Using Hot Single Point Incremental Forming

The present work focuses on the manufacturing of Ti-6Al-4V parts using hot single point incremental forming (SPIF), a non-conventional forming technology mainly oriented toward the fabrication of prototypes, spare parts, or very low volume series. In the used procedure, the entire sheet is heated and kept at uniform temperature while the tool incrementally forms the part, with the limited accuracy of the obtained parts being the major drawback of the process. Thus, this work proposes two approaches to improve the geometric accuracy of Ti-6Al-4V SPIF parts: (i) correct the tool path by applying an intelligent process model (IPM) that counteracts deviations associated with the springback, and (ii) skip overforming deviations associated with the deflection of the sheet along the perimeter of the part based on a design improvement. For this purpose, a generic asymmetric design that incorporates features of a typical aerospace Ti-6Al-4V part is used. The results point out the potential of both solutions to significantly improve the accuracy of the parts. The application of the IPM model leads to an accuracy improvement up to 49%, whereas a 25.4% improvement can be attributed to the addendum introduction. The geometric accuracy study includes the two finishing operations needed to obtain the part, namely decontamination and trimming

Experimental characterization of the AA7075 aluminum alloy using hot shear compression test

The experimental characterization of the material under shear loading is essential for researchers to study the plastic behavior of materials during manufacturing processes. Indeed, regardless of the loading mode, ductile materials mainly deform plastically under shear loading. Thus, for such material behavior analysis, shear tests are very useful. In this paper, a test procedure is defined to characterize the shear deformation of AA7075 aluminum alloy at high strain under compression loading. The Finite Element (FE) simulation is used to select the suitable specimen geometry for the testing. Finally, the experimental tests are carried out using a conventional compression device at a constant strain rate of 0.1 s−1 and at an elevated temperature of 20–500 °C. The results show that the drop in the flow stress curved relative to the increase in temperature exhibits the softening mechanism. The homogeneous behavior of the shear strain along the shear region was also observed and shown by the macro and micro images. The effect of temperature and equivalent strain on the evolution of the microstructure is discussed in detail. It is discovered that, various dynamic recrystallization mechanisms were recorded for aluminum alloy AA7075 depending on the imposed strain conditions.H2020 Marie Skłodowska-Curie Action

Inconel 718 aleaziozko pieza asimetriko baten konformatzea prentsa gabe?

This article upholds the possibility of forming an aeronautical component made of In-conel 718 sheet by means of Incremental Sheet Forming and without using a forming press. The re-search work presented aims to validate the operation of the hydrostatic ball burnishing as a strategy to improve the surface quality of an aeronautical component of Inconel 718, previously shaped by Asymetric Incremetal Sheet Forming (AISF). The combination of both processes, burnishing on AISF, has a very high level of innovation and is a pioneer in its application on an industrial component made of this high performance nickel-chromium alloy. The surface quality of the incrementally shaped component has been studied to subsequently apply a burnishing by means of the hydrostatic ball. The results obtained confirm the feasibility of the proposed strategy, with a reduction in roughness ranges between 20 and 65%, depending on the area treated.; Artikulu honek berresten du posible dela Inconel 718 aleaziozko pieza asimetriko bat prentsa gabe konformatzea. Aurkeztutako ikerketa-lanak bola bidezko leunketa hidrostatikoaren erren-dimendua balioztatzeko asmoa du, aurrez inkrementalki konformatutako Inconel 718 aleazio aeronauti-koko piezetan. Lanaren helburua pieza aeronautikoen gainazal akaberaren optimizazioa da. Konforma-zio inkrementalaren eta bola-leunketaren konbinazioa balioztatzeak berrikuntza-maila handia aurkezten du eta aitzindaria da bere aplikazioan. Pieza konformatuaren gainazalaren kalitatea aztertu ondoren bola bidezko leunketa hidrostatikoa aplikatu da. Egindako emaitzek baieztatu dute proposatutako estrategia-ren bideragarritasuna, zimurtasuna %33 eta % 70 artean murriztea, tratatutako eremuaren arabera