Fabien Nazaret

Fibre Reinforced Refractory Castables :An Alternative Solution for SPF Die Manufacturing

Today heat resistant cast steels are the nominal solution for Ti-SPF forming die manufacturing. Nevertheless, this materials present some drawbacks related to delivery time and cost. A fibre reinforced refractory castable (FRRC) is proposed as a new solution for prototype SPF die manufacturing. Due to the general brittleness of refractory castables, a short fibre reinforcement has been investigated in order to avoid catastrophic failure during the forming process. General macroscopic behavior of such materials is very complex and presents large evolutions with the testing temperature. The paper addresses the important benefits of the reinforcement for refractory castable in the case of loading on a complex structure. The capability of the material to support several cracks is shown in the case of a technological sample with a complex shape.

Design of SPF Dies Based on Advanced Material Behaviour Models

Numerical simulation was performed on an axi-symmetric metallic die during a whole fife cycle. It was shown that most important stresses are generated by the thermal gradients during heating up and repeated die removal from the press furnace and also by the clamping pressure during forming. The forming itself causes non dimensioning stresses. Creep relaxation during forming induces plastic deformation and distortion of mould after cooling down. To increase simulation relevance, new behaviour models are investigated for three classes of materials candidate for SPF dies: heat resistant cast steels, fibre reinforced refractory concretes and low cost monolithic ceramics.

Titanium Superplastic Forming by Aurock: A Complete Integrated Solution from CAD File to Final Part

With its experience in the SPF simulation and tool manufacturing, Aurock completes its offer in the titanium SPF field with the part forming and brings a global support from the conception up to the manufacturing. Aurock proposes tool design, forming strategy and simulation, rapid tool manufacturing made of refractory castable reinforced with metallic fibre and now titanium superplastic forming. To improve its offer, Aurock started from a blank page and developed a specific SPF press to test and assess new heating solutions. One major innovation permits to reduce the heating time using a direct sheet heating. The process becomes anisothermal. This approach avoid time to heat up to 900°C large toolings. The completed offer for titanium SPF parts and successful results on the heating solutions are presented.

Hot Forming Process Analysis of Ti6Al-4V Alloy: Experiment, Behaviour Modelling and Finite Element Simulation

The present investigation aims at evaluating and understanding the thermo-mechanical be-haviour of a titanium alloy under hot forming conditions. In this work, several considerations are ad-dressed. First, Scanning Electron Microscopy observations are performed to assess the evolutions of(α − β) phases, grain size, defects regarding the thermo-mechanical loadings from different static anddynamic tests (various temperatures and strain rates). Hence, the relationships between mechanicalproperties and micro-structure evolutions in such conditions allow a first assessment of the deforma-tion mechanisms in link with the macroscopic stress-strain curves. Afterwards, a behaviour modelformulation associated to an identification procedure of the parameters of the constitutive equationsis proposed. Finally, several tests performed under hot forming conditions and conducted on an in-dustrial press are compared to Finite Element calculations. Results are compared and provide someinteresting improvement ways in order to investigate the influence of the process parameters on thefinal shape of the part.

Development of Double-Action SPF Forming Process by Finite Element Simulation for A380 Part

The rear part of the APF A380 has a deep drawn shape. In order to develop the forming by SPF process of this part, numerical simulation by finite elements has been performed. Several configurations for 2D and 3D modeling were studied to determine an efficient forming strategy. A double-action solution was chosen. It ensures a satisfactory thickness distribution. This article will deal with the modeling assumptions, the results of individual cases of calculation and comparison with parts obtained at the Airbus plant.

Thermomechanical Characterization of Monolithic Refractory Castables

This paper deals with the characterization of the thermomechanical behavior of monolithic refractory castables in a wide temperature range, up to 1200°C. Different test types are considered: tensile tests, compression tests, bending tests and tests on more complex shapes and geometries. A particular attention is paid to the detailed characterization and interpretation of the non-linear behaviors of these materials. Monotonic, cyclic and creep tests are considered. In some cases, digital image correlation (DIC) methods can be coupled to mechanical tests to obtain strain fields. Such results are particularly interesting to observe and to understand damage processes. As damage is a major characteristic of the monolithic castable behaviors, links are established between the thermomechanical behavior and damage mechanisms. Two main scales are taken into account for damage characterization: the macroscopic and the microscopic ones. Main mechanisms that are considered deal with microcracking, macrocracking, debonding and cavitation. Two types of materials are considered: non-reinforced and fiber reinforced refractory castables.

Sizing of Refractory Castable Gas-Burner Using Thermomechanical Simulations

Damage is a crucial characteristic of refractory castables and has to be considered to simulate correctly the behaviour of refractory structures. But, damage modelling by finite element simulations remains difficult. Indeed, the use of a continuum damage model with softening leads to strain localization phenomena. Numerical results depend on the mesh. Several numerical methods allow solving this meshing dependence by introducing an internal length in the material constitutive laws. In this paper, a regularization method has been applied with the damage plasticity model, considering a scalar value for damage. This model enables to take into account permanent strains due to plasticity and damage before and after the peak stress in tension and compression. Thermomechanical simulations are performed with this model to predict damage in a gas-burner. The damage level is evaluated after a thermal simulation generating high temperature gradients. Interests to take into account damage in the refractory structures are discussed. Sensitivity of results to material properties is studied. This work gives an example of using thermomechanical simulations to improve the design of refractory castable structures and to help in the material choice.