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In this work, impact puncture tests (drop tests) have been used to both tune numerical models and correlate the performance of customised titanium cranial prostheses to the manufacturing process. In fact, experimental drop tests were carried out either on flat disk-shaped samples or on prototypes of titanium cranial prostheses (Ti-Gr5 and Ti-Gr23 were used) fabricated via two innovative sheet metal forming processes (the super plastic forming (SPF) and the single point incremental forming (SPIF)). Results from drop tests on flat disk-shaped samples were used to define the material behaviour of the two investigated alloys in the finite element (FE) model, whereas drop tests on cranial prostheses for validation purposes. Two different approaches were applied and compared for the FE simulation of the drop test: (i) assuming a constant thickness (equal to the one of the undeformed blank) or (ii) importing the thickness distribution determined by the sheet forming processes. The FE model of the drop test was used to numerically evaluate the effect of the manufacturing process parameters on the impact performance of the prostheses: SPF simulations were run changing the strain rate and the tool configuration, whereas SPIF simulations were run changing the initial thickness of the sheet and the forming strategy. The comparison between numerical and experimental data revealed that the performance in terms of impact response of the prostheses strongly depends on its thickness distribution, being strain hardening phenomena absent due to the working conditions adopted for the SPF process or to the annealing treatment conducted after the SPIF process. The manufacturing parameters/routes, able to affect the thickness distribution, can be thus effectively related to the mechanical performance of the prosthesis determined through impact puncture tests.

In the present work, the design of the warm forming of a component in AA5754-O for railway vehicle applications is proposed: the increase of the working temperature overcomes the big limitation of aluminium alloys in terms of poor formability. The design of the process started from the characterization of both the mechanical and the strain behaviour of the alloy under investigation: tensile tests and formability tests, carried out in warm conditions (up to 250°C) provided the necessary data to be implemented within the numerical model created with the commercial Finite Element (FE) code Abaqus. The numerical activity was arranged according to an uncoupled thermo-mechanical approach: a preliminary mechanical simulation of the forming process at room temperature was run in order to evaluate the critical regions. Subsequently, thermal simulations of the heating up of both the tools and the blank were conducted to design the heating system in order to achieve a temperature distribution as uniform and close to the target (according to the results of the material characterization) in the blank deformation zone. Nodal temperature distribution coming from the thermal simulation was imported as a boundary condition into the subsequent mechanical step: strain severity was locally evaluated implementing the forming limit curves at different temperatures within the Abaqus FE model. Simulations results were subsequently validated performing experimental trials, confirming the beneficial effect of adopting warm conditions to avoid the risk of rupture: thus a sound component was successfully manufactured.

The present work has been focused on the warm deep drawing process by superimposing a thermal gradient between the blank centre in contact with the punch and the blank flange (which is going to be drawn). Using such a technique the limit drawing ratio of Mg alloys can be dramatically improved. As a case of study, the forming of cylindrical AZ31 cups was investigated. In particular, the attention was focused on the forming temperature (in both the flange region and in the blank centre). Finite element simulations were run in order to investigate the stress and strain distribution in the material determined by the temperature gradient and to validate experimental results. Tests highlighted that a LDR equal to 3.375 is possible when setting the temperature of the blank holder at 230 °C and the punch speed at 6 mm/min.

An accurate determination of the contact pressure and local sliding in a cold rolling process is an essential step towards the prediction of the roller’s life due to wear damage. This investigation utilized finite element analysis to quantify the local contact pressure and local sliding over the rolling bite in a plate cold rolling process. It was the first study to quantify the local sliding distance in a rolling process using the Finite Element Analysis (FEA). The numerical results indicate that the local contact pressure over the rolling bite demonstrates a hill profile, and the peak coincides with the neutral plane. The local sliding distance over the rolling bite demonstrates a double-peak profile with the two peaks appearing at the forward slip and backward slip zones respectively. The amplitude of sliding distance in the backward slip zone is larger than that in the forward slip zone. A stick zone was confirmed between the forward slip and backward slip zones. According to a parametric study, the local contact pressure and sliding distance decrease when the thickness reduction is reduced or the diameter of the roller is decreased. The location of the neutral plane always presents at the rolling exit side of the rolling bite’s center. The size of the stick zone enlarges and the sizes of slip zones shrink significantly when the friction coefficient is increased. Finally, a novel concept of wear intensity was defined to examine the wear of the roller based on the local contact pressure and local sliding distance. The results show that a two-peak wear response exists in the backward and forward slip zones. The magnitude of the wear in the backward slip zone is larger than that in the forward slip zone. For a given roller and blank material combination, using a smaller thickness reduction, a smaller diameter roller and a higher friction coefficient condition can reduce the wear of the roller for a single rolling cycle. The current paper develops an understanding of rolling contact responses to the wear of the roller in rolling process. The research method can also be applied to study other rolling or sliding wear problems.

Deep drawing is a sheet metal forming operation which involves conversion of flat thin sheet blanks drawn into desired cups. Forming of high strength sheet metal and low weight alloys under warm conditions is in great demand now-a-days and its application has great importance in nuclear plants, cryogenic vessels, heat exchangers, pharmaceutical industries etc. In the Present investigation the austenitic stainless steel (ASS)-304 of different blank diameters is deep drawn under warm condition. It is observed that there is a significant improvement in limiting drawing ratio (LDR) from 2.16 at room temperature to 2.5 at 150 °C and drawn cups are determined. In this investigation blanks of different diameters are deep drawn to determine LDR at various temperatures and it was found out that under warm conditions there is a significant improvement in limiting drawing ratio from room temperature to 300 °C. In the present investigation the other material IS 737 grade aluminum alloy is drawn at elevated temperature and its formability was investigated in warm condition and it was found that there was a substantial increase in the formability of commercial pure aluminum when drawn at 350 °C. For a successful design and simulation by finite element (FE) analysis, it is important to determine reliable friction data for a given lubrication system. Especially when the deep drawing operation is being performed under warm conditions, the prediction of friction becomes complex as its value increases with temperature. By inverse analysis of relating the predicted and measured values of the load-stroke curve this paper presents a practical methodology using the deep drawing test and finite element (FE) analysis to evaluate the coefficient of friction between blank and tooling.