The aim of this paper is to explore the watertightness behaviour for high pressure applications using Multi Jet Fusion technology and polyamide 12 as a material. We report an efficient solution for manufacturing functional prototypes and final parts for water pressure applications and provide manufacturing rules for engineers in the pressurized product development process for up to 10 MPa of nominal pressure. The research findings show manufacturers the possibility of using additive manufacturing as an alternative to traditional manufacturing. Water leakage was studied using different printing orientations and wall thicknesses for a range of pressure values. An industrial ball valve was printed and validated with the ISO 9393 standard as also meeting tolerance requirements. This paper is a pioneering approach to the additive manufacturing of high-performance fluid handling components. This approach solves the problem of leakage caused by porosity in additive manufacturing technologies.

Ball-burnishing induces compressive residual stresses on treated materials by the effect of plastic deformation. The result is an increase in the fatigue life of the treated part, retarding the initiation of cracks on the surface. Compressive residual stresses have been previously measured by X-ray diffraction near the surface, revealing considerably high values at the maximum analyzed depth, in relation to other finishing processes such as shot peening. However, the maximum analyzed depth is very limited by using this technique. In this paper, the incremental hole drilling (IHD) technique is tested to measure residual stresses, being able to reach a 2-mm measuring depth. To that objective, a commercial strain gage is used and calibrated using finite element model simulations. A second Finite Element Model based on material removal rate is developed to obtain the equations to calculate the strain release through IHD. Finally, residual stresses are measured experimentally with that technique on two different materials, confirming that ball-burnishing increases the compressive residual stresses in layers up to 0.5¿mm deep for the testing conditions, which is a good response to industrial needs. The method proves to be suitable, simple and inexpensive way to measure the value of these tensions.Preprin

The cold expansion of fastener holes in aircraft components is a standard technique to improve fatigue life. There is concern that the beneficial residual stresses arising from cold expansion may relax due to creep. This paper describes experimental measurement and finite element prediction of cold expansion residual stresses and their redistribution after creep, with and without additional mechanical load. Experimental measurements of near-surface stresses used an X-ray diffraction technique while average through-the-thickness stresses were measured using a new method based on Sachs’ boring. This new method allowed non-axisymmetric residual stresses to be measured, as was the case when creep relaxation occurred with mechanical load. Axisymmetric and three dimensional finite element analyses were used to predict the stress distribution through the thickness of the component showing good agreement with measurement. Creep relaxation of residual stress does indeed occur, but some benefit of the cold expansion remains, particularly when creep relaxation is combined with the application of mechanical load.