Wenguang Nan

Nanjing Tech University · School of Mechanical and Power Engineering

The spreading behaviour of cohesive sand powder is modelled by Discrete Element Method, and the spreadability and the mechanical jamming are focused. The empty patches and total particle volume of the spread layer are examined, followed by the analysis of the geometry force and jamming structure. The results show that several empty patches with dif...

Powder spreadability is critical to particle spread layer and thus the quality of final product in powder-based additive manufacturing. In this work, the effect of plastic deformation on the spreadability is investigated, in which particle jamming, particle dynamics within the heap, and spread layer are analysed. The results show that under the eff...

An improved linear model is developed for elasto-plastic and adhesive contact. New correlations are proposed and validated to estimate the key parameters of the model, including contact stiffness, yield point, maximum pull-off force and time step. The newly proposed contact model is applied to the analysis of single particle contact behaviour upon...

Spreadability of cohesive and frictional powder is critical in powder spreading of additive manufacturing. Different to flowability, the experimental test techniques and underlying powder mechanics of spreadability have not yet been thoroughly acknowledged. In this work, the effects of operation conditions and particle properties on the spreadabili...

Understanding of the rheological behaviour of fully three-dimensional and non-uniform particle flow is of great interest. We analyse the resistance exhibited by a granular bed as a rotating impeller is penetrated into it, from which the rheological characteristics of the bed are deduced. For this end, the transient rheological response of both sphe...

Blade rheometer has been used to characterise the rheological behaviour of bulk particles at high shear strain rate under dynamic conditions, yet little is known about its underlying powder mechanics. We analyse the effects of the shape and rotation direction of the blade, particle-blade friction and particle aspect ratio on the rheological behavio...

Powder spreading in Additive Manufacturing (AM) has been analysed extensively by the Discrete Element Method, but without considering the presence of ambient gas. For fine particles, as commonly used in AM, the gas drag could affect the quality of spread layer. Here, we consider the dynamics of powder spreading by a roller for a gas-atomised metal...

Additive manufacturing based on powder spreading is attracting great interest, but one key weakness is that narrow gaps used for spreading produce non-uniformity in the spread layer due to transient jamming. We propose a simple technique for assessing the powder spreadability, a measure of the ease with which a powder is spread uniformly without th...

Powder processing and manufacturing operations are rate processes for which the bottleneck is cohesive powder flow. Diversity of material properties, particulate form, and sensitivity to environmental conditions, such as humidity and tribo-electric charging, make its prediction very challenging. However, this is highly desirable particularly when a...

Additive Manufacturing (AM) using powder spreading requires uniform spreading. For narrow spreader gaps, as commonly used, transient jamming and segregation could adversely affect the uniformity of the spread layer. Here, we consider the dynamics of powder spreading by roller for a gas-atomised metal powder and analyse the effects of gap height and...

Rodlike particles have been usually found in industrial applications, such as the straw and needle catalyst in energy and chemical engineering. Compared to spherical particles, rodlike particles exhibit different behaviour in the packing structure due to their rotational movement. In this work, we have experimentally explored the packing structure...

Additive manufacturing (AM) has attracted increasing attention in a wide range of applications, due to its ability for rapid manufacturing of complex shapes directly from a Computer-Aided Design (3D CAD) output. One of the manufacturing methods is based on powder processing, where a thin bed is formed to which an energy beam is applied to sinter an...

Additive manufacturing (AM) is going through an exponential growth, due to its enormous potential for rapid manufacturing of complex shapes. One of the manufacturing methods is based on powder processing, but its major bottleneck is associated with powder spreading, as mechanical arching adversely affects both product quality and speed of productio...

Particle shape has a strong influence on bulk powder flow and its associated rheology. It promotes mechanical arching and adversely affects fast feeding and dosing. We use the FT4 powder rheometer of Freeman Technology to experimentally characterise the particle flow as a function of the shear strain rate, and to predict its dynamics for rod-shape...

In fluidised bed processes, the solids are in vigorous motion and thus inevitably subjected to mechanical stresses due to inter-particle and particle-wall impacts. These stresses lead to a gradual degradation of the particles by surface wear, abrasion and body fragmentation commonly termed attrition. One significant contribution of attrition comes...

The FT4 powder rheometer of Freeman Technology is widely used nowadays in industry for characterisation of particle flow under dynamic conditions of shear strain rate. It measures the work (termed flow energy) required to penetrate a rotating impeller into a powder bed. However, little is known about its underlying powder mechanics, i.e. the relati...

Understanding of particle flow behaviour as a function of strain rate is of great interest in many items of equipment of industrial processes, such as screw conveyors, impeller mixers, and feeders, etc. The traditional commercial instruments for bulk powder flow characterisation, such as shear cells, operate at low shear strain rates, and are not r...

In fluidised bed processes, the solids are in vigorous motion and thus inevitably subjected to mechanical stresses due to inter-particle and particle-wall impacts. These stresses lead to a gradual degradation of the particles by surface wear, abrasion and body fragmentation commonly termed attrition. One significant contribution of attrition comes...

The FT4 powder rheometer of Freeman Technology is widely used nowadays in industry for characterisation of particle flow under dynamic conditions of shear strain rate. It measures the work (termed flow energy) required to penetrate a rotating impeller into a powder bed. However, little is known about its underlying powder mechanics, i.e. the relati...

Fluidization of non-spherical particles widely exists in various engineering applications, such as biomass utilization and catalytic reaction. In this work, a mathematical analysis of particle fluidization has been carried out by employing a combined approach of discrete element method (DEM) and computational fluid dynamics (CFD). The emphasis is f...

In order to quantify the material damping of deformed flexible fibers, a linear viscoelastic sphere-chain model based on the discrete element method is presented. In the model the interaction between any two neighboring spheres connected by a visual bond is modeled as springs and dash-pots which can be characterized by the bond stiffness and bond d...

The packing of rodlike particles with a micro size widely exists in various engineering applications, such as the process of separation and catalytic reaction. In this work, a mathematical analysis of the rod packing has been carried out by employing the discrete element method (DEM). The emphasis is focused on the influence of material properties...

In this paper, the rod model is adopted to describe the flexible fiber in the simple shear flow. By using fibers with large stiffness, the Jeffery orbits are obtained to validate the model. Then the effect of the concentration on the dynamic behavior of flexible fibers in semi-concentrated suspension is numerically simulated. The results show that...

Employing the discrete element method with a multi-sphere model, this paper presents a numerical analysis of the packing structure of fibers during the preparation of the fiber porous blank, in which effects of such shape parameters of fibers as the aspect ratio and the curl index have been taken into account. For ten kinds of straight fibers and e...