scholarly journals Effect of Aggregate Gradation on the Stiffness of Asphalt Mixtures

Author(s):  
Hasan Al-Mosawe ◽  
Nick Thom ◽  
Gordon Airey ◽  
Amjad Al-Bayati

Abstract Aggregate gradation plays an important role in the behaviour of asphalt mixtures. Packing of aggregate is a very important factor that will be affected by changing the aggregate gradation. Many researchers have investigated different ways of describing packing both theoretically and practically. Bailey ratios have recently been used to understand the volumetric properties of mixtures. In this paper, the Bailey ratios have been used, and two further ratios have also been introduced to allow the asphalt mixture gradation to be fully understood. Thirteen different aggregate gradations have been chosen within the 14 mm asphalt concrete specification to investigate the effect of particle size distribution on the stiffness of the mixture. It was found that variation in aggregate gradation has a significant effect on asphalt stiffness, even within specification limits, and a reasonable correlation between the set of ratios investigated and the Indirect Tensile Stiffness.

2017 ◽  
Vol 184 ◽  
pp. 240-247 ◽  
Author(s):  
A. Norori-McCormac ◽  
P.R. Brito-Parada ◽  
K. Hadler ◽  
K. Cole ◽  
J.J. Cilliers

2017 ◽  
Vol 64 (6) ◽  
pp. 281-287 ◽  
Author(s):  
Nur Zalikha KHALIL ◽  
Sanjay Kumar VAJPAI ◽  
Mie OTA ◽  
Kei AMEYAMA

Author(s):  
Vaishak Ramesh Sagar ◽  
Samuel Lorin ◽  
Johan Göhl ◽  
Johannes Quist ◽  
Christoffer Cromvik ◽  
...  

Abstract Selective laser melting (SLM) process is a powder bed fusion additive manufacturing process that finds applications in aerospace and medical industries for its ability to produce complex geometry parts. As the raw material used is in powder form, particle size distribution (PSD) is a significant characteristic that influences the build quality in turn affecting the functionality and aesthetics aspects of the product. This paper investigates the effect of PSD on the printed geometry for 316L stainless steel powder, where three coupled in-house simulation tools based on Discrete Element Method (DEM), Computational Fluid Dynamics (CFD), and Structural Mechanics are employed. DEM is used for simulating the powder bed distribution based on the different powder PSD. The CFD is used as a virtual testbed to determine thermal parameters such as heat capacity and thermal conductivity of the powder bed viewed as a continuum. The values found as a stochastic function of the powder distribution is used to analyse the effect on the melted zone and deformation using Structural Mechanics. Results showed that mean particle size and PSD had a significant effect on the packing density, melt pool layer thickness, and the final layer thickness after deformation. Specifically, a narrow particle size distribution with smaller mean particle size and standard deviation produced solidified final layer thickness closest to nominal layer thickness. The proposed simulation approach and the results will catalyze in development of geometry assurance strategies to minimize the effect of particle size distribution on the geometric quality of the printed part.


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