Investigation into the Mechanism of the Steel Particle Feeding Process: A Numerical and Experimental Study

The particle feeding system is a prerequisite for the realization of particle impact drilling technology. Because of the high density, the storage and flow of the steel particle are different from those of the other nonviscous particles. The differential equation of the particle movement was built with the liquid bridge force model and the discrete element method. The dynamic movement process and the distribution state of particles in the high-pressure tank were analyzed. For 1 mm steel particles, the mass flow rate decreased with the increase in water content. For 2 mm and 3 mm steel particles, the water content of 15% and 20% was the dividing point of the mass flow rate from increasing to decreasing. When the water content was 10% and 20%, the mass flow rate increased with the steel particle size. But when the water content was 30% and 40%, the mass flow rate decreased with the steel particle size. The study of the control mechanism of the uniformity and stability of particles showed that the funnel flow was the major reason causing the instability and blocking of the feeding process. This research results can provide a basis for the further improvement of the differential pressure feeding system.

A simple and economical method for the synthesis of steel-reinforced copper composite

The present study explores a new method of steel particle-reinforced copper matrix composite synthesis. Steel reinforced copper was prepared by stir casting processing method at variable percentages between 10 wt% and 50 wt%. Characterization and mechanical testing were performed on these composites using a variety of techniques. The results showed that the microstructure of the composites has a uniform distribution of steel particles in the matrix with good interfacial integrity. Brinell hardness, tensile and yield strengths, impact energy and compressive yield strength of the composites increased with increasing steel particle contents. Vickers micro-hardness increased markedly at the interface region between particle and matrix evident by the hardness maps. The friction coefficient increased proportionally with increasing steel particle content in the composite, but the contrary was noticed for accumulative wear amount. A slight decrease in deformability is expected by increasing particle content. A ductile fracture was noticed in fractographs of fracture surfaces. Cracks are propagated in the Cu matrix up to the point of fracture, i.e. not through the interfacial boundaries.

Mechanical Characterizations of 3D-printed PLLA/Steel Particle Composites

The objective of this study is to characterize the micromechanical properties of poly-l-lactic acid (PLLA) composites reinforced by grade 420 stainless steel (SS) particles with a specific focus on the interphase properties. The specimens were manufactured using 3D printing techniques due to its many benefits, including high accuracy, cost effectiveness and customized geometry. The adopted fused filament fabrication resulted in a thin interphase layer with an average thickness of 3 µm. The mechanical properties of each phase, as well as the interphase, were characterized by nanoindentation tests. The effect of matrix degradation, i.e., imperfect bonding, on the elastic modulus of the composite was further examined by a representative volume element (RVE) model. The results showed that the interphase layer provided a smooth transition of elastic modulus from steel particles to the polymeric matrix. A 10% volume fraction of steel particles could enhance the elastic modulus of PLLA polymer by 31%. In addition, steel particles took 37% to 59% of the applied load with respect to the particle volume fraction. We found that degradation of the interphase reduced the elastic modulus of the composite by 70% and 7% under tensile and compressive loads, respectively. The shear modulus of the composite with 10% particles decreased by 36%, i.e., lower than pure PLLA, when debonding occurred.