Abstract:In this paper, the discrete element method framework is employed to determine and analyze the stresses induced during and after the powder metallurgy process of particle-reinforced composite. Applied mechanical loading and the differences in the thermal expansion coefficients of metal/intermetallic matrix and ceramic reinforcing particles during cooling produce the complex state of stresses in and between the particles, leading to the occurrence of material defects, such as cracks, and in consequence the compo… Show more
“…[34], Martin et al [27] have used DEM [35] to model sintering of tens of thousands of particles. Nevertheless, most sintering investigations based on DEM [34,36,37,38,39,40,41] do not take into account grain growth and coarsening of particles. To our best knowledge, only one DEM study [27] includes a crude model of grain growth that does not consider realistic driving forces at the scale of individual particles.…”
Section: In This Context Following the Initial Work Of Parhami And MC Meekingmentioning
confidence: 99%
“…Even in the early stage of sintering, the realism of DEM simulations can benefit from the addition of a physically based grain growth model. Also, DEM provides a natural mean to introduce realistic initial packing with size distribution [41,42,43,44]. For packings with size distribution, sintering contact models that handle particles of different sizes are necessary.…”
Section: In This Context Following the Initial Work Of Parhami And MC Meekingmentioning
confidence: 99%
“…For packings with size distribution, sintering contact models that handle particles of different sizes are necessary. Whereas most DEM simulations deal with equal size particles [27,36,37,45] or use an equivalent radius by analogy with elastic and plastic contact theories [37,39,41,42], it is necessary to introduce more realistic models for unequal size particles with large size ratios. Pan et al [13] proposed such a description based on numerical simulations at the scale of individual particles, but to our best knowledge no DEM simulation has yet introduced this type of model.…”
Section: In This Context Following the Initial Work Of Parhami And MC Meekingmentioning
Sintering is a high temperature process used for ceramic or metallic powder consolidation that consists of concurrent densification and grain growth. This work presents a coupled solid-state sintering and grain growth model capable of studying large packings of particles within the Discrete Element Method (DEM) framework. The approach uses a refinement for large particle size ratios of previously established contact laws to model shrinkage. In addition, mass transfer between neighboring particles is implemented to model grain growth by surface diffusion and grain-boundary migration. The model assumptions are valid for initial and intermediate stage sintering. The model is validated on a two-particle system by comparing neck and particle size evolutions with those obtained by phase-field and meshedbased methods. Simulations on large packings (up to 400 000 particles) with particle size distributions originating from experiments are performed. The results of these simulations using physical data from the literature are compared to experimental data with good accordance of the key features of the microstructure evolution (densification kinetics, grain size-density trajectory, evolution of the mean grain size and of the size distribution). The simulations show that even at an early stage of sintering, hardly detectable grain growth actually affects the sintering kinetics to a non-negligible extent and that the realism of DEM simulations of sintering is improved when grain growth is considered. Taking advantage of the possibility to simulate large packings, the model elucidates the influence of the initial particle size distribution on the grain growth kinetics.
“…[34], Martin et al [27] have used DEM [35] to model sintering of tens of thousands of particles. Nevertheless, most sintering investigations based on DEM [34,36,37,38,39,40,41] do not take into account grain growth and coarsening of particles. To our best knowledge, only one DEM study [27] includes a crude model of grain growth that does not consider realistic driving forces at the scale of individual particles.…”
Section: In This Context Following the Initial Work Of Parhami And MC Meekingmentioning
confidence: 99%
“…Even in the early stage of sintering, the realism of DEM simulations can benefit from the addition of a physically based grain growth model. Also, DEM provides a natural mean to introduce realistic initial packing with size distribution [41,42,43,44]. For packings with size distribution, sintering contact models that handle particles of different sizes are necessary.…”
Section: In This Context Following the Initial Work Of Parhami And MC Meekingmentioning
confidence: 99%
“…For packings with size distribution, sintering contact models that handle particles of different sizes are necessary. Whereas most DEM simulations deal with equal size particles [27,36,37,45] or use an equivalent radius by analogy with elastic and plastic contact theories [37,39,41,42], it is necessary to introduce more realistic models for unequal size particles with large size ratios. Pan et al [13] proposed such a description based on numerical simulations at the scale of individual particles, but to our best knowledge no DEM simulation has yet introduced this type of model.…”
Section: In This Context Following the Initial Work Of Parhami And MC Meekingmentioning
Sintering is a high temperature process used for ceramic or metallic powder consolidation that consists of concurrent densification and grain growth. This work presents a coupled solid-state sintering and grain growth model capable of studying large packings of particles within the Discrete Element Method (DEM) framework. The approach uses a refinement for large particle size ratios of previously established contact laws to model shrinkage. In addition, mass transfer between neighboring particles is implemented to model grain growth by surface diffusion and grain-boundary migration. The model assumptions are valid for initial and intermediate stage sintering. The model is validated on a two-particle system by comparing neck and particle size evolutions with those obtained by phase-field and meshedbased methods. Simulations on large packings (up to 400 000 particles) with particle size distributions originating from experiments are performed. The results of these simulations using physical data from the literature are compared to experimental data with good accordance of the key features of the microstructure evolution (densification kinetics, grain size-density trajectory, evolution of the mean grain size and of the size distribution). The simulations show that even at an early stage of sintering, hardly detectable grain growth actually affects the sintering kinetics to a non-negligible extent and that the realism of DEM simulations of sintering is improved when grain growth is considered. Taking advantage of the possibility to simulate large packings, the model elucidates the influence of the initial particle size distribution on the grain growth kinetics.
Reinforcing polymers with particles and fibers has been a common strategy for decades, in order to make them suitable for high-demanding industrial applications. As composites often undergo dynamic loads, it is important to understand their behavior under such conditions. This review first classifies the types of polymer composites and then explains their failure behavior under tension and compression loading, followed by an overview of some of the experimental procedures used to characterize the polymer composites' dynamic mechanical performance. Afterward, the most significant findings in terms of the highstrain-rate compressive and tensile strength and modulus of polymer composites are thoroughly discussed. The results, available in the literature, on the mechanical properties of polymer composites under quasi-static conditions are also presented and compared with the high-strain-rate data. The differences are explained by discussing the changes in the structural configurations of polymer matrices under quasi-static and dynamic loads. Lastly, conclusions and future perspectives are given, with the intent of highlighting the most promising polymer composites that can be used for a wide variety of applications.
The conventional approach when engineering components manufactured from titanium is to design the thermomechanical processing to develop an optimal microstructure in a single alloy. However, this conventional approach can lead to unnecessary over-engineering of components, particularly when only a specific subcomponent region is under demanding service stresses and environments. One approach being developed to join multiple alloys in a single component and enhance engineering performance and efficiency is FAST-DB—whereby multiple alloys in powder form are diffusion bonded (DB) using field-assisted sintering technology (FAST). But the joining of multiple alloys using conventional welding and joining techniques can generate high residual stress in the bond region that can affect the mechanical performance of the components. In this study, the residual stress distribution across dissimilar titanium alloy diffusion bonds, processed from powder using FAST, were measured using X-Ray diffraction and the Contour method. The measurements show low residual stress in the bulk material processed with FAST as well as in the diffusion bond region. In addition, FAST-DB preforms subsequently hot forged into different near-net shapes were also analyzed to understand how the residual stress in the bond region is affected by a subsequent processing. Overall, no sharp transitions in residual stress was observed between the dissimilar alloys. This study reinforces confidence in the solid-state FAST process for manufacturing next generation components from multiple titanium alloy powders.
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