61 research outputs found
Exercices de mathématique générale I: (relatifs au cours du Professeur J. Janssen)
No full textSYL-010761 = Fascicule 1 ;SYL-010760 = Fascicule 2 ;SYL-011641 = Fascicule 7 ;SYL-005191 = Techniques de dérivation et d'intégrationFascicule 2 :Structures algébriques et nombres. Eléments de logique et applications -- Fascicule 7 :IntégralesFascicules 1, 2 et 7 :Exercices rédigés par M. Anciaux, F. Quertainmont, J.M. Reinhard et F. Van Humbeeck ;Techniques de dérivation et d'intégration :exercices rédigés par M. Anciaux, F. Quertainmont, J.-M. Reinhard1e candidature en sciences économiques ;1e candidature école de commercePremière édition 1976-1977info:eu-repo/semantics/published
en het groteske. Een beschouwing van proza, poëzie en poëtica van F. Harmsen van Beek in het licht van het groteske
No full text
Microstructure and Texture of Metal Parts Produced by Selective Laser Melting
No full textSelective laser melting (SLM) is an additive manufacturing technique by which structural geometrical complex parts an be created directly by selectively melting consecutive layers of powder. The high energy den sity applied by a laser beam results in high and directional thermal gra dients. In combination with the additive character of the process, this results in the formation of a unique microstructure in SLM parts which c an be altered by varying the process parameters or the constitution of t he alloy. In this work, the microstructure and texture of pure Ta, Ti-6Al-4V, AlSi 10Mg and maraging steel 18Ni(300) SLM parts are characterised by microst ructural analysis (LOM, SEM and EBSD) and X-ray diffraction. The influen ce of the unique microstructure on the mechanical properties are analyse d as well. The experimental work is supported by using a pragmatic model for SLM to calculate the temperature distribution and by using a model to estimate the plastic deformation behaviour based on the measured text ure. For most alloys, the high thermal gradients result in very fine submicro n-sized cellular-dendrites growing toward the centre of the melt pool al ong the easygrowth direction (AlSi10Mg and maraging steel 18Ni(300)). Du e to the partial remelting or previously consolidated layers, most grain s solidify epitaxially and grow across the layers. For pure metals (Ta) and Ti-6Al-4V, the solidification front remains stable, resulting in lar ge elongated grains more or less along the building direction. The competition between the epitaxial solidification and the orientation of the easy-growth of the parent grain with respect to the local heat f low direction is found to be the main determining factor to determine th e morphological as well as crystallographic texture during SLM.status: Publishe
Influence of Powder Bed Preheating on Microstructure and Mechanical Properties of H13 Tool Steel SLM Parts
No full textAbstractPowder bed preheating is a promising development in selective laser melting (SLM), mainly applied to avoid large thermal stresses in the material. This study analyses the effect of in-process preheating on microstructure, mechanical properties and residual stresses during SLM of H13 tool steel. Sample parts are produced without any preheating and are compared to the corresponding parts made with preheating at 100°, 200°, 300°, and 400°C. Interestingly, internal stresses at the top surface of the parts evolve from compressive (-324MPa) without preheating to tensile stresses (371MPa) with preheating at 400°C. Nevertheless, application of powder bed preheating results in a more homogeneous microstructure with better mechanical properties compared to H13 SLM parts produced without preheating. The fine bainitic microstructure leads to hardness values of 650-700Hv and ultimate tensile strength of 1965MPa, which are comparable to or even better than those of conventionally made and heat treated H13 tool steel
Impulse excitation apparatus to measure resonant frequencies, elastic moduli, and internal friction at room and high temperature
No full textThis paper presents a new apparatus to measure elastic properties and internal friction of materials. The apparatus excites the test specimen by a light mechanical impact (impulse excitation) and performs a software-based analysis of the resulting vibration. The resonant frequencies f(r) of the test object are determined and, in the case of isotropic and regular shaped specimens, the elastic moduli are calculated. The internal friction value (Q(-1)) is determined for each f(r) as Q(-1)=k/(pi f(r)) with k the exponential decay parameter of the vibration component of frequency f(r). A furnace was designed and equipped with automated impulse excitation and vibration detection devices, thus allowing computer-controlled measurements at temperatures up to 1750 degrees C. The precision of the measured f(r) depends on the size and stiffness of the specimen, and varies from the order of 10(-3) (that is +/-1 Hz at 1 kHz) in soft, high damping materials or light specimens, to values as precise as 10(-5) (that is +/-0.1 Hz at 10 kHz) in larger or stiffer specimens. The highly reproducible Q(-1) measurements are accurate whenever the relation Q(-1)=k/(pi f(r)) holds. The precision of the Q(-1) measurement depends on the suspension or support of the specimen, and on the specimen size. Since external energy losses are relatively smaller for larger specimens, the lower limit of measurable Q(-1) extends from 10(-3) for small specimens (for example <1 g) down to 10(-5) with increasing specimen size. High temperature tests have shown that Q(-1) can be monitored up to values of about 0.1. (C) 1997 American Institute of Physics.status: Publishe
Superelastic behavior and stabilization of stress-induced martensite in Cu-13.4Al-4.0Ni single crystals
No full textBy applying tensile stress along [100] of beta phase, the superelastic behavior and stabilization of stress-induced martensite (SIM) of Cu-13.4Al.4.0Ni(mass fraction, %) single crystals were studied. The results show that the pseudo-yield stress decreases with the increase of cycling number, and keeping load isothermally has an effect on stabilization of SIM. Previous thermal cycling between (M-s - 20 degreesC) and (A(f) + 20 degreesC) promotes the superelasticity and the stabilization of SIM as well; the pre-thermal cycling also reduces the pseudo-yield stress. However, once the stabilization of SIM is produced, it can be destabilized by either the afterwards thermal cooling-heating cycling or load and immediately unload cycling in (A(f)similar toM(d)) Isothermal treatment in (A(f)similar toM(d)) brings restabilization of SIM. The maximum superelastic value from beta --> beta (1) (18 R) is 9 % for the studied single crystal. When test temperature is in A(f)similar to (A(f) + 50 degreesC) and stress is in 0 similar to 350 MPa, the superelastic behavior exist.status: Publishe
Mechanical Properties of AlSi10Mg Produced by Selective Laser Melting
No full textAbstractSelective Laser Melting (SLM) is an Additive Manufacturing (AM) technique in which a part is built up in a layer- by-layer manner by melting the top surface layer of a powder bed with a high intensity laser according to sliced 3D CAD data. In this work, mechanical properties like tensile strength, elongation, Young's modulus, impact toughness and hardness are investigated for SLM-produced AlSi10Mg parts, and compared to conventionally cast AlSi10Mg parts. It is shown that AlSi10Mg parts with mechanical properties comparable or even exceeding to those of conventionally cast AlSi10Mg can be produced by SLM
- …
