Papers by Brecht Van Hooreweder
This paper provides new insights into the fatigue properties of porous metallic biomaterials prod... more This paper provides new insights into the fatigue properties of porous metallic biomaterials produced by additive manufacturing. Cylindrical porous samples with diamond unit cells were produced from Ti6Al4V powder using Selective Laser Melting (SLM). After measuring all morphological and quasi-static properties, compression-compression fatigue tests were performed to determine fatigue strength and to identify important fatigue influencing factors. In a next step, post-SLM treatments were used to improve the fatigue life of these biomaterials by changing the microstructure and by reducing stress concentrators and surface roughness. In particular, the influence of stress relieving, hot isostatic pressing and chemical etching was studied. Analytical and numerical techniques were developed to calculate the maximum local tensile stress in the struts as function of the strut diameter and load. With this method, the variability in the relative density between all samples was taken into account. The local stress in the struts was then used to quantify the exact influence of the applied post-SLM treatments on the fatigue life. A significant improvement of the fatigue life was achieved. Also, the post-SLM treatments, procedures and calculation methods can be applied to different types of porous metallic structures and hence this paper provides useful tools for improving fatigue performance of metallic biomaterials.
Journal of Materials Processing Technology, 2016
104] Detection of bearing failure by acoustic emission A W Lees, Z Quiney Swansea University and ... more 104] Detection of bearing failure by acoustic emission A W Lees, Z Quiney Swansea University and A Ganji SKF Engineering & Research Centres [105] Metrological self-check as an efficient tool for condition monitoring R Taymanov, Mendeleyev Institute of Metrology [106] About periodicity and signal to noise ratio -the strength of the autocorrelation function N Martin and C Mailhes GIPSA-lab, INPG/CNRS Department Images Signals KEY [100] -Denotes reference number in abstract booklet 11:10 [107] Application of the singular value decomposition method for steam turbine diagnostics T Galka, Institute of Power Engineering [108] Condition monitoring for tribological contacts Ling Wang, University of Southampton [109] Condition monitoring for ship fuel (bunkering) applications M P Henry University of Oxford [110] On-Line monitoring of transient variations in hydraulic power plants pressure pipes S Charbonnier, [257] AURA: The use of binary associative memories for condition monitoring applications
ABSTRACT The quasi-static and fatigue properties of Fused Deposition Modelling ABS parts are larg... more ABSTRACT The quasi-static and fatigue properties of Fused Deposition Modelling ABS parts are largely influenced by the quality of the interconnection between adjacent tracks and layers. During this process, coalescence of the interconnection is obtained through he thermal energy of the deposited material and build environment and is strongly influenced by many factors related to the production process. However, the process parameters influencing this thermal history are often not monitored. Furthermore, when printing large batches in a single build, it is often impossible to control the process such that the optimal thermal history is obtained at every location in the build. Therefore, any designer has to take into account the inherent product variability resulting from the local and time-dependent variations in the production process. This work focuses on the identification of the variation that is caused in the mechanical behaviour, more specifically in the quasi-static and fatigue properties of the final component. The variability in material properties between different identical components (inter-variability) is identified based on measurements on a sample population, and related to the production process.
Space frame optimization can be complex and time consuming if done with traditional analytical me... more Space frame optimization can be complex and time consuming if done with traditional analytical methods. Optimization using 3D finite element analysis in an iterative design cycle provides a solution, but often leads to results that are not conform to production constraints. For the design of the tubular space frame of a solar powered vehicle, a topology optimization in 2D surfaces was used to develop the 3D frame. This allowed significant gains in modeling and processing time and insured conformity of the results with the production constraints of a tubular space frame. The shortened development time allowed more design cycles to be spent on the entire vehicle design, leading to a highly improved design. The described method can be applied to any type of tubular space frame optimization.
The fracture toughness (K1c) and fatigue crack growth rate (FCGR) properties of selective laser m... more The fracture toughness (K1c) and fatigue crack growth rate (FCGR) properties of selective laser melted (SLM) specimens produced from grade 5 Ti6Al4 V powder metal has been investigated. Three specimen orientations relative to the build direction as well as two different post-build heat treatments were considered. Specimens and test procedures were designed in accordance with ASTM E399 and ASTM E647 standard. The results show that there is a strong influence of post-build processing (heat treated versus ‘as built’) as well as specimen orientation on the dynamic behaviour of SLM produced Ti6Al4 V. The greatest improvement in properties after heat treatment was demonstrated when the fracture plane is perpendicular to the SLM build direction. This behaviour is attributed to the higher anticipated influence of tensile residual stress for this orientation. The transformation of the initial rapidly solidified microstructure during heat treatment has a smaller beneficial effect on improving...
CIRP Annals - Manufacturing Technology
Selective laser sintered parts in polyamide are increasingly being used in functional application... more Selective laser sintered parts in polyamide are increasingly being used in functional applications. The monotonic properties of these parts are well-known and documented. The cyclic material properties, on the other hand, are largely unknown. Therefore, in this paper a systematic analysis is made of fatigue properties and failure mechanisms of selective laser sintered parts subjected to fluctuating loading in tension/compression. Both plain and notched specimens are produced along perpendicular building directions. The fatigue behaviour of these parts is analysed and compared to injection moulded samples. In addition, the influence of the test frequency and the notch manufacturing method is studied.
Mechanical Systems and Signal Processing, 2015
ABSTRACT Precise prediction of the lifetime of rolling element bearings is a crucial step towards... more ABSTRACT Precise prediction of the lifetime of rolling element bearings is a crucial step towards a reliable design of many rotating machines. For bearings subjected to highly varying loads, recent research emphasises a strong reduction of the actual bearing lifetime w.r.t. the classically calculated bearing lifetime. This paper experimentally analyses the influence of external dynamic loads on the lifetime of rolling element bearings. A novel bearing test rig is introduced. The test rig is able to apply a fully controlled multi-axial static and dynamic load on a single test bearing. Also, different types and sizes of bearings can be tested. Two separate investigations are conducted. First, the behaviour of the lubricant film between the rolling elements and raceways is analysed. Increased metallic contact or breakdown of the film during dynamic excitation is investigated based on the measured electrical resistance through the bearing. The study shows that the lubricant film thickness follows the imposed variations of the load. Variations of the lubricant film thickness are similar to the variations when the magnitude of the static bearing load is changed. Second, wear of the raceway surfaces is analysed. Surface wear is investigated after a series of accelerated lifetime tests under high dynamic load. Due to sliding motion between asperities of the contacting surfaces in the bearing, polishing of the raceway honing structure occurs. This polishing is clearly observed on SEM images of the inner raceway after a test duration of only 0.5% of the calculated L10 life. Polishing wear of the surfaces, such as surface induced cracks and material delamination, is expected when the bearing is further exposed to the high dynamic load.
CIRP Annals - Manufacturing Technology, 2014
Selective laser sintered parts in polyamide are increasingly being used in functional application... more Selective laser sintered parts in polyamide are increasingly being used in functional applications. The monotonic properties of these parts are wellknown and documented. The cyclic material properties, on the other hand, are largely unknown. Therefore, in this paper a systematic analysis is made of fatigue properties and failure mechanisms of selective laser sintered parts subjected to fluctuating loading in tension/compression. Both plain and notched specimens are produced along perpendicular building directions. The fatigue behaviour of these parts is analysed and compared to injection moulded samples. In addition, the influence of the test frequency and the notch manufacturing method is studied.
ABSTRACT The quasi-static and fatigue properties of Fused Deposition Modelling ABS parts are larg... more ABSTRACT The quasi-static and fatigue properties of Fused Deposition Modelling ABS parts are largely influenced by the quality of the interconnection between adjacent tracks and layers. During this process, coalescence of the interconnection is obtained through he thermal energy of the deposited material and build environment and is strongly influenced by many factors related to the production process. However, the process parameters influencing this thermal history are often not monitored. Furthermore, when printing large batches in a single build, it is often impossible to control the process such that the optimal thermal history is obtained at every location in the build. Therefore, any designer has to take into account the inherent product variability resulting from the local and time-dependent variations in the production process. This work focuses on the identification of the variation that is caused in the mechanical behaviour, more specifically in the quasi-static and fatigue properties of the final component. The variability in material properties between different identical components (inter-variability) is identified based on measurements on a sample population, and related to the production process.
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Papers by Brecht Van Hooreweder