Mechanical Behavior Of Parts Research Articles

Revisiting the influence of the scanning speed on surface topography and microstructure of IN718 thin walls in directed energy deposition additive manufacturing

Controlling the mechanical properties of metallic parts produced by additive manufacturing remains challenging. The mechanical behavior of parts is mainly related to the microstructure, which depends on process parameters and manufacturing strategies. The scanning speed is one of the key parameters that can be modulated during the process (according to the kinematic behavior of the machine tool) in order to reach different microstructures. Thus, in this work, an experimental study in laser metal powder directed energy deposition is conducted to analyze the influence of the scanning speed on the macroscopic geometry, the surface topography, and the microstructure. To do so, a series of single-layer experiments has been conducted to establish an empirical relationship between the laser power, the powder flow-rate and the scanning speed on the one hand, and the layer height and width on the other hand. In addition, six multi-layer thin-walled structures have been produced for various laser powers and scanning speeds in order to determine an association with macroscopic features, topography and microstructure. This approach opens interesting long-term perspectives to better control microstructures in DED.

FEA integration in the tolerance analysis using Skin Model Shapes

Many research works on tolerance analysis have been carried out in the last thirty years. In this paper, a new idea is proposed, aiming to investigate the effect of form error and mechanical behavior of parts on the stack-up result by combining the recent novelties on the tolerance analysis of rigid and flexible bodies. The real parts are simulated considering the non-nominal Skin Model Shape and the mechanical properties in order to simulate the assembly of a realistic case study. A manufacturing signature model to generate the features with geometric deviations and Finite Element Analysis (FEA) are used.

Effect of IN718 Recycled Powder Reuse on Properties of Parts Manufactured by Means of Selective Laser Melting

Abstract Powder quality control is essential to obtain parts with suitable mechanical properties in Selective Laser Melting manufacturing technique. One of the most important advantages of suchtechnique is that it allows an efficient use of the material, due to the possibility to recycle and reuse un-melted powder. Nevertheless, powder material properties may change due to repeated recycling, affecting this way the mechanicalbehavior of parts. In this paper the effect of powder reuse on its quality and on the mechanical properties of the resulting melted parts is studied via self-developed recycling methodology. The material considered for investigation was IN718, a nickel superalloy widely used in industry. After recycling powder up to 14 times, no significant changes were observed in powder and test parts properties. The results obtained in this work will help to validate powder recycling methodology for its use in current industrial Selective Laser Melting manufacturing.

Reversible effect of memory of form as the result of thermal cycling conditioning under load

1. The amount of the REMF formed as the result of thermal cycling under load is not proportional to the residual deformation, which is a violation of the known rule valid in the case of isothermal loading. 2. The amount of the REMF depends substantially upon the number of preliminary thermal cycles under load. With the same amount of plastic deformation the greater the number of thermal cycles, the greater the effect. Such an influence of repeated martensite⇌austenite transformations may be explained by features of the processes of inheritance of defects of the crystalline lattice in the martensite transformations. 3. Thermal cycling treatment of titanium nickelide-base alloys under the action of an external load may lead to the occurrence of two REMF's of opposite signs. The possibility of their coexistence and interaction must be taken into consideration both in interpretation of the experimental results and in prediction of the mechanical behavior of parts of various devices. 4. After thermal cycling with significant stresses the spontaneous change in form of the material may have a complex character accompanied by a change in the direction of deformation with a steady reduction or increase in temperature.