The Experts below are selected from a list of 49815 Experts worldwide ranked by ideXlab platform

Jean Frene - One of the best experts on this subject based on the ideXlab platform.

Hjh Jos Brouwers - One of the best experts on this subject based on the ideXlab platform.

  • Ultra-lightweight concrete: Conceptual design and performance evaluation
    Cement and Concrete Composites, 2015
    Co-Authors: Pr Przemek Spiesz, Hjh Jos Brouwers
    Abstract:

    The present study presents a methodology to design ultra-lightweight concrete that could be potentially applied in monolithic concrete structures, performing as both load Bearing Element and thermal insulator. A particle grading model is employed to secure a densely packed matrix, composed of a binder and lightweight aggregates produced from recycled glass. The developed ultra-lightweight concrete, with a dry density of about 650–700 kg/m 3 , shows excellent thermal properties, with a thermal conductivity of about 0.12 W/(m K); and moderate mechanical properties, with a 28-day compressive strength of about 10–12 N/mm 2 . Furthermore, the developed concrete exhibits excellent resistance against water penetration.

  • Design of ultra-lightweight concrete: towards monolithic concrete structures
    Vestnik MGSU, 2014
    Co-Authors: Pr Przemek Spiesz, Hjh Jos Brouwers
    Abstract:

    This study addresses the development of ultra-lightweight concrete. A moderate strength and an excellent thermal conductivity of the lightweight concrete are set as the design targets. The designed lightweight aggregates concrete is targeted to be used in monolithic concrete facade structure, performing as both load Bearing Element and thermal insulator. The developed lightweight concrete shows excellent thermal properties, with a low thermal conductivity of about 0.12 W/(m·K); and moderate mechanical properties, with 28-day compressive strengths of about 10-12 N/mm 2. This combination of values exceeds, to the researchers’ knowledge, the performance of all other lightweight building materials. Furthermore, the developed lightweight concrete possesses excellent durability properties.

  • Design of lightweight aggregates composites : an insight into calcium sulphate and cement as binders (part II)
    2014
    Co-Authors: Hjh Jos Brouwers
    Abstract:

    This article addresses the design of lightweight aggregates composites applying different materials (calcium sulphate hemihydrate and cement) as binder. A moderate strength and an excellent thermal conductivity of the lightweight composites are set as the design targets. The designed lightweight aggregates composites are targeted to be used in monolithic facade structure, performing as both load Bearing Element and thermal insulator. The mixtures are designed based on the insight that superior properties of a granular mix are achieved when a so-called geometric grading line is designed and obtained, applying a model known as the modified Andreasen and Andersen model. The properties of the obtained composites in both fresh and hardened states are investigated. Subsequently, a comparative study on calcium sulphate system and cement as binders is performed.

Roy D. Marangoni - One of the best experts on this subject based on the ideXlab platform.

  • Frictional Analysis of MoS2 Coated Ball Bearings: A Three-Dimensional Finite Element Analysis
    Journal of Tribology, 1997
    Co-Authors: Michael R. Lovell, Michael M. Khonsari, Roy D. Marangoni
    Abstract:

    A brief review of finite Element contact and friction theory is presented for low-speed Bearing operations. A three-dimensional finite Element model is developed to realistically characterize the friction experienced by a coated ball Bearing Element. The finite Elements results, which are obtained for various normal loads and ball materials, are verified using Hertzian contact theory and previous experimental tests performed by the authors. From the results, general trends for the frictional behavior of coated Bearing surfaces are established and implications to the field of controls, as applied to precision positioning and tracking instruments are discussed.

  • A finite Element analysis of the frictional forces between a cylindrical Bearing Element and MoS2 coated and uncoated surfaces
    Wear, 1996
    Co-Authors: Michael R. Lovell, Michael M. Khonsari, Roy D. Marangoni
    Abstract:

    Most precision positioning mechanisms and tracking systems contain instrument ball Bearings that operate at ultra-low-speeds. Successful operation of these highly sensitive systems largely depends upon the ability to predict their Bearing friction behavior. Until recently, very little research has been performed to understand the ultra-low-speed friction in coated Bearings. Herein lies the scope of this paper: to develop a realistic finite Element model which determines fundamental tribological friction relationships in coated Bearings which are directly applicable to enhancing the control of precision systems. A brief review of the general friction response of Bearings operating at ultra-low-speeds and the principles by which thin solid films reduce friction is given. As all of the work presented in this paper exclusively utilizes molybdenum disulfide as a solid lubricant film, the crystallographic structure, material properties and attributes of MoS2 are discussed. A two-dimensional finite Element model was developed to realistically characterize the friction experienced by a rolling Element (i.e. a cylinder) confined between two parallel plates (representing Bearing races). Experimental tests of a similar nature but with ball Bearings were performed by the authors in a specially designed apparatus that allowed speeds as low as 0.001 deg −1. Friction force results are presented for coated surfaces under several normal loads per unit length with steel and ceramic rolling Elements. Using the results, general trends for the frictional behavior of coated Bearing surfaces are established.

Adil Saeed - One of the best experts on this subject based on the ideXlab platform.

  • Experimental analysis and modelling of c-crack propagation in silicon nitride ball Bearing Element under rolling contact fatigue
    Tribology International, 2018
    Co-Authors: M.h. Nazir, Zulfiqar Ahmad Khan, Adil Saeed
    Abstract:

    Abstract A comprehensive model for predicting fatigue failure probability of surface c-shaped cracks in silicon nitride ball Bearing Elements under rolling contact fatigue (RCF) has been presented in this paper. Firstly, three-dimensional finite Element analysis (FEA) is used to determine the stress intensity factors (SIFs) along the front of crack by using fracture mechanics approach. Then the propagation uncertainty of c-crack is evaluated by using surrogate models built upon highly accurate finite Element modelling for equivalent stress intensity factors. Finally, the Monte Carlo Simulations combined with surrogate models are used to predict the failure probability of rolling ball Bearing Element. Simulation results reveal that it is possible to reduce the failure probability of ball Bearing Element up to 95% by reducing the maximum crack size and enhancing the fracture toughness of the ball material. The modelling results have been verified by experimental studies showing that the current predictions of c-crack fatigue failures were consistent with the experimental results. Fatigues crack initiation and propagation is a significant failure mechanism within ceramic ball Bearing Elements. It presents design and durability challenges for both manufacturers and users. A three-fold approach, to simulate fatigue propagation of c-shaped crack in rolling contact ceramic Bearing Element presented in this paper, is novel and will solve major durability issues within ceramic ball Bearing Elements subject to rolling contact fatigue.

Michel Fillon - One of the best experts on this subject based on the ideXlab platform.