Design of custom cranial prostheses combining manufacturing and drop test finite element simulations
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ORIGINAL ARTICLE
Design of custom cranial prostheses combining manufacturing and drop test finite element simulations G. Palumbo 1
&
A. Piccininni 1 & G. Ambrogio 2 & E. Sgambitterra 2
Received: 19 May 2020 / Accepted: 2 October 2020 # The Author(s) 2020
Abstract 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. Keywords Super plastic forming . Single point incremental forming . Ti-6Al-4V . Finite element . Custom prosthesis . Drop test
1 Introduction The continuous research for a new category of prosthetic implants capable of improving the life expectancy of patients, thus reducing the risk of an additional surgery or prolonged hospitalisation, is still an open question [1]. The complete customisation, the biocompatibility and the mechanical resistance represent only some of the requirements in the development of innovative implants characterised by superior performances.
* G. Palumbo [email protected] 1
Dipartimento di Meccanica, Matematica e Management, Politecnico di Bari, Bari, Italy
2
Dipartimento di Ingegneria Meccanica, Energetica e Gestionale, Università della Calabria, Rende, Italy
In particular, when dealing with cranioplasty surgeries, there are two main reasons to use a prosthetic implant fully ma
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