Mar 9, 2016 - laser or electron beam melting of specific regions in a bed of metal powder to ... a desktop computer with Xeon® X5650 @ 2.67Hz processors.
MTC Case Study 30876-001
March 2016
Numerical Modelling of Powder-Bed Additive Layer Manufacturing Technologies
Integration of PowderBed Additive Layer Manufacturing Simulation on an Industrial Scale
The process of additive layer manufacture (ALM) consists of selective laser or electron beam melting of specific regions in a bed of metal powder to build a component sequentially from hundreds or thousands of horizontal layers. Conventional ways of modelling ALM processes have failed to meet industrial demands due to the huge computational effort
required
and
the
associated
challenges
with
numerical
convergence.
The MTC Simulation Group has addressed this limitation through an MTC Members’ Collaborative Research Project aimed at developing an innovative and robust, rapid predictive methodology for powder-bed ALM technologies. The methodology has been validated and applied to complex industrial components to predict distortion and residual stresses as well as give indications of crack initiation risks.
The implementation of the developed methodology in the design of ALM is typically expected to:
Figure 1: Component produced by 3T RPD Ltd with the application of ALM
The innovative part of the developed methodology lies in both the combination
of
analytical
and
numerical
physically-meaningful
analyses, as well as being able to scale the created solutions from the
Overview of Validated Methodology
micro-scale to the macro-scale. A concept of using a specimen is introduced to accommodate the micro-to-macro scaling and calibrate the analytical thermal model. This allows the mechanical solution to be numerically derived without the need for a micro-thermal analysis, which would otherwise be prohibitively lengthy.
Figure 3: Metal 3D printed bicycle frame manufactured by Renishaw
The key capabilities of the methodology can be summarised as: •
Key Capabilities
Residual stresses and distortion can be predicted during ALM fabrication.
•
Industrial components can be simulated in less than 12 hours using a desktop computer with Xeon® X5650 @ 2.67Hz processors.
•
Different materials and process parameters can be incorporated for selective laser melting and electron beam melting.
•
Alternative user-defined toolpath strategies can be modelled that will minimise distortion and residual stresses.
•
It has been applied to a number of industrial components to reduce and compensate distortion, reduce the risk of crack initiation and understand the effect of the induced residual stresses on the component life expectancy.
•
ALM simulation results have been integrated into a manufacturing process chain, including post-processing technologies, such as heat treatment, machining operations and surface treatment & hardening, in order to understand the overall component mechanical behaviour and predict its structural quality.
Figure 4: Application of an aerofoil – prediction of residual stresses in ALM
MTC Case Study 30876-001
March 2016
The methodology has been successfully used in the following
Simulation Applications
applications:
• • • • •
•
Distortion prediction of thin tube structures.
•
Distortion reduction of a lightweight bracket by improving the geometrical stiffness.
•
Aerospace Medical Devices Power Generation Automotive Industry Railway • Defence
Distortion reduction in the blade of an aero-engine by using a geometry compensation technique (see Figure 5).
•
Prediction and reduction of tensile residual stresses, thereby improving the service life of an aerofoil.
•
Predictions of crack initiation risks during fabrication and their mitigation using geometrical modifications for a gas turbine component used in the power generation industry.
•
Selection of appropriate materials in the design of components subjected to thermo-mechanical loading.
Figure 5: An example of applying a geometry compensation strategy based on FEA predictions where component distortion was reduced
Figure 6: Distortion prediction of a specimen using a range of metals
MTC Case Study 30876-001
March 2016
The MTC has successfully simulated two manufacturing process chains for an additively manufactured blade by integrating the novel methodology into a process chain simulation platform. The final distortion and residual stresses were predicted and used for the life assessment of the blade. The simulation results contributed towards
Simulation of Manufacturing Process Chains of Additively Manufactured Blade
making key decisions during the design and manufacture, including geometry compensation to reduce distortion and mitigate risks of crack initiation in service.
Figure 8: ALM blade followed by postprocessing - Morris Technologies
The MTC has developed and matured simulation methodologies and techniques that have been applied to reduce distortion and improve service life of high-value ALM parts. More maturation in modelling and simulation is required to address other engineering aspects in ALM and further improve the quality of the parts, as shown in Figure 9.
Figure 9: Technology roadmap for the maturity in modelling and simulation of additive layer technologies - 2016
