Development and optimisation of incremental sheet forming of titanium grade 2: process mapping

Uheida, Emad Harari A. (2017-03)

Thesis (PhD)--Stellenbosch University, 2017.

Thesis

ENGLISH ABSTRACT: Manufacturing products ensure value creation from natural resources. The change in manufacturing systems to a greater emphasis on personalisation, increase the need for customised products. Manufacturing challenges are presented by the increasing instability in global markets, shorter innovation cycles, input cost pressures and generally expensive resources. Ever since the industrial revolution, the transformations in manufacturing from mass production and product variety and vice versa, were driven by market and societal transformations and the development of new enabling technologies. Single point incremental forming is a promising rapid prototyping technology for sheet metal applications. Titanium alloys are an attractive material for numerous applications, but its use has been mainly restricted by its material and manufacturing costs. Titanium alloys are also used in a variety of engineering applications, due to its high-strength to weight ratio, corrosion resistance and bio-compatibility. The alloy’s mechanical characteristics make it possible to reduce the application’s structural weight and increase its performance with thin-wall designs. Incremental sheet forming is characterised by its highly-localised deformation ability without drawing in material from a surrounding area. In this truly die-less configuration the sheet is shaped only by the action of a forming tool that has a single point of contact with the blank. Significant cost reductions can be realised from these flexible technologies devoted to reduce the buy-to-fly ratio and enlarge the scope of applications to small series titanium products. Although single point incremental sheet forming (SPIF) is an active research area, the process demands and limitations for forming of CP Grade 2 titanium alloy sheets are not clearly understood. Understanding the effects of these process variables to develop resource-efficient forming process chains of CP Grade 2 titanium sheets will make a significant contribution to manufacturing knowledge. In this dissertation, an efficient twostage process mapping approach is developed and validated. In order to characterise the SPIF conceptual processing space and to identify the key design factors, a systematic quantitative literature review has been undertaken analysing results from relevant publications. The design of experiments (DoE) and one factor at a time test (OFAT) experiments have been methodically implemented to verify the developed conceptual framework. The ultimate goal is to design aprocess suitable for incremental forming of CP Grade 2 sheets that can consistently deliver a product that meets the required quality attributes. The established approach involves mapping the SPIF of the CP Grade 2 in terms of the five key process variables. Once the behaviour of the SPIF process has been mapped, a thorough study of the role of a secondary process variable can be accomplished to evaluate its effect on the process across the full five-key-variables working window. The influence of SPIF factors on the formability of CP Grade 2 were investigated based on the forming forces, the forming temperature and the process productivity. The approach yields insight into the theory of the SPIF process, which deepens the understanding of the dependence of the process outcomes on different variables. The region of the SPIF process variable space, where successful forming of the CP Grade 2 titanium can be anticipated is identified throughout this process mapping approach. The processed data have been presented in a practical two-dimensional process map. The developed working window can be used as a design tool to understand the process demands and limitations for forming of CP Grade 2 titanium alloy sheets. This understanding of the effects of these process variables will enable the development of resource-efficient forming process chains for the CP Grade 2 titanium sheets. The approach as such, however, can be implemented for the establishing of process characteristics for other titanium alloys too.

AFRIKAANSE OPSOMMING: Vervaardiging van produkte verseker die toevoeging van waarde tot natuurlike hulpbronne. Die verandering in vervaardiging stelsels om vir individue voorsiening te maak, verhoog die behoefte vir meer persoonlike produkte. Die uitdagings in vervaardiging word veroorsaak deur die toenemende variasie in wêreldmarkte, korter innovasie siklusse, toenemende insetkostes en duur hulpbronne. Sedert die Industriële Revolusie was die transformasie in vervaardiging van massaproduksie na produk verskeidenheid en omgekeerd, gedryf deur die mark, sosiale veranderinge en die ontwikkeling van nuwe tegnologie. Enkel punt inkrementele vervorming is 'n belowende snel vervaardiging tegnologie vir plaatmetaal toepassings. Titaan allooie is 'n gesogte materiaal vir talle toepassings, maar die gebruik daarvan is hoofsaaklik beperk deur die materiaal en vervaardigingskoste. Titaan allooie word ook gebruik in 'n verskeidenheid ingenieurstoepassings, as gevolg van sy hoë sterkte-tot-gewig verhouding, korrosie weerstand en biomediese aanvaarbaarheid. Die meganiese eienskappe van die allooie maak dit moontlik om die strukturele gewig van toepoasssings te verminder en hul prestasie met 'n dun-muur ontwerpe te verhoog. Inkrementele plaat vervorming word gekenmerk deur die hoogs gesentraliseerde vervorming vermoë, sonder om die nabye materiaal te betrek. In die werklike vormlose opstelling word die plaat gevorm slegs deur die beweging van die beitel wat 'n enkele kontakpunt met die plaat het. Beduidende kostes kan deur hierdie vervormings tegnologie gespaar word. Terselfdertyd kan die koop-tot-vlieg verhouding met titaan allooie verminder word en die toepoassings van klein reeks titanium produkte vermeerder. Hoewel enkele punt inkrementele plaat vervorming (SPIF) 'n aktiewe navorsing gebied is, is die proses vereistes en beperkings vir die vorming van CP Graad 2 titaan allooi plaatmateriaal nie duidelik bekend nie. Die verstaan van die gevolge van hierdie proses veranderlikes om hulpbrondoeltreffend vervorming proses kettings van CP Graad 2 titaan plate te ontwikkel, sal 'n belangrike bydrae tot vervaardiging kennis maak. In hierdie tesis word 'n doeltreffende twee fase proses kaart benadering ontwikkel en bevestig. Die SPIF konseptuele verwerking ruimte kon slegs ontwikkel word deur die sleutel ontwerp faktore te identifiseer. 'n Stelselmatige kwantitatiewe literatuuroorsig was onderneem om die resultate van relevante publikasies te ontleed. Die ontwerp van eksperimente (DOE) en een faktor op 'n tyd toets (OFAT) eksperimente was wetenskaplik geïmplementeer om die ontwikkelde konseptuele raamwerk te bevestig. Die doel is om 'n proses kaart vir die vervorming van CP Graad 2 plate te ontwikkel wat ‘n konstante kwaliteit produk kan verseker. Die benadering behels die kartering van die SPIF van die CP Graad 2 titaan allooi in terme van die vyf mees belangrikste prosesveranderlikes. Sodra die gedrag van die SPIF proses gekarteer is, kan 'n deeglike studie van die rol van 'n sekondêre proses veranderlike tot stand gebring word om die uitwerking daarvan op die proses oor die volle vyf sleutel-veranderlikes werk venster te evalueer. Die invloed van SPIF faktore op die vormbaarheid van CP Graad 2 titaan allooi is ondersoek en baseer op die vervorming kragte, die vervorming temperatuur en die produktiwiteit van die proses. Die benadering lewer insig in die teorie van die SPIF proses op, wat die begrip van die afhanklikheid van die proses uitsette op verskillende veranderlikes verdiep. Die area waar die SPIF proses veranderlikes suksesvolle vervorming van die CP Graad 2 titaan kan verwag word geïdentifiseer deur hierdie proses kartering benadering. Die verwerkte data is aangebied in 'n praktiese tweedimensionele proses kaart. Die ontwikkelde werk venster kan gebruik word as 'n ontwerp instrument om die proses vereistes en vervorming beperkings van CP Graad 2 titaan allooi plate te verstaan. Hierdie begrip van die gedrag van hierdie proses veranderlikes sal die ontwikkeling van die hulpbron-doeltreffende vervorming proses kettings vir CP Graad 2 titanium plate moontlik maak. Die benadering kan ook geïmplementeer word vir ander titaan allooie.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/101243
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