The Effect of Grinding Media on Mineral Breakage Properties of Magnetite Ores

The breakage and liberation of minerals are the key to fluidized mining for minerals. In the ball milling process, steel balls function as not only a grinding action implementer but also energy carrier to determine the breakage behavior of ores and the production capacity of the mill. When ground products present a much coarse or much fine particle size distribution, the separation process will suffer, resulting in inefficient recovery of useful minerals. Optimal control of the particle size distribution of the products is therefore essential, but the complexity and randomness of ball mill grinding make it difficult to determine the appropriate ball size. To solve the problem in the precise measurement of grinding ball diameters, this paper carried out magnetite grinding experiments with grinding balls of different diameters under the same grinding conditions to study the influence pattern of steel ball diameters on the particle break behavior, the particle size distribution of ground products, and the mineral liberation degree distribution. The research proposed on the matching relation between the ball size and the quality of ground products is essential for improving the ground product quality and reducing energy consumption.

Mechanochemical Ring-Opening Metathesis Polymerization: Development, Scope, and Mechano-Only Copolymer Synthesis

Ruthenium-alkylidene initiated ring-opening metathesis polymerization (Ru-ROMP) was realized under solid-state conditions employing a mechanochemical ball milling method, promoting greenness and broadening scope. High-speed ball milling provided sufficient mixing and energy to the reaction mixture comprised of the catalyst and solid monomers, thus eliminating the need for solvents. Studies on the catalytic species and ball milling parameters (liquid-assisted grinding, vibration frequency, and ball size) revealed that mechanical energy regulated solid-state Ru-ROMP and it follows similar mechanistic features of solution-phase reactions. The solubility and miscibility of monomer and Ru-initiator are not a limitation in solid-state ball milling. Without the use of a solvent, a wide spectrum of solid monomers, including ionomer, fluorous monomer, and macromonomers, were successfully polymerized. Finally, effective direct copolymerization of immiscible monomers such ionic/hydrophobic and ionic/fluorous monomers resulted in a set of copolymers that are difficult to make using traditional solution procedures.

Effect of Ball Size on the Microstructure and Morphology of Mg Powders Processed by High-Energy Ball Milling

Commercial powders of pure magnesium were processed by high-energy ball milling. The microstructural and morphological evolution of the powders was studied using scanning electron microscopy (SEM), energy dispersive spectrometry (EDX) and X-ray diffraction (XRD). From the results obtained, it was determined that the ball size is the most influential milling parameter. This was because balls of 1 mm diameter were used after a previous stage of milling with larger balls (i.e., 10 and 3 mm). The powder particles presented an unusual morphology with respect to those observed in the Mg-milling literature and recrystallization phenomena. Moreover, the result strongly varied depending on the ball-to-powder weight ratio (BPR) used during the milling process.

Numerical characterization of local and global non-uniformities in the load distribution in ball screws

Load distribution in ball screws is a representation of the ball contact stress, and it is fundamental to understanding the behavior of these machine elements. This work aims to conduct a multi-variable analysis of the load distribution in ball screws. For this purpose, a numerical tool is developed for the generation and calculation of ball screw finite element (FE) models, which has been validated against the state of the art. This tool is based on the combination of an analytical contact model and the use of high-order FE models for the analysis of the load distribution of ball screws and stands out for its accuracy (less than 1% error against high-order FE models), adaptability, versatility (models are generated with more than 20 design variables and they can be introduced as components in larger models) and efficiency (being the computational time 1.25% of that of a high-order FE models) with respect to other existing models. Many different design variables (number of start threads, pitch, contact angle, ball size, slenderness and load arrangement) are studied in order to obtain a general characterization of the morphology of the load distribution in ball screws. Among them, the most influential variables on the load distribution and therefore on the structural behavior of ball screws are, load arrangement (with ratio r variations of up to 25% on the same ball screw) and slenderness (with ratio variations of up to 13% on ball screws with two turns of difference). The two most characteristic features, the non-uniformity at a local and global level are identified, along with as the possible causes of their appearance and the consequences that they may cause.

Near-Field Measurements of Water-Entry Sound of Low-Speed Metal Balls in a Non-Anechoic Tank

As one of the target characteristics, water-entry sound characteristics are of great significance to study, and its research has certain reference value for the detection of sea target. The water-entry sound of an underwater target is a transient sound signal, and it is mainly measured in open water such as the sea and lakes. However, due to the short duration of the acoustic signal and the modulation effect of the measuring environment, it is difficult to measure water-entry sound. To deal with this problem, in this work, the water-entry sound of a metal ball was measured in a water tank in a laboratory. The measurements were made in the direct acoustic control area 0.45 m away from the drop point of the ball to eliminate the influence of reflection. Through a time-domain integration, the power of the transient signal of the water-entry sound of the metal ball was obtained. The energy of the initial impact sound and the pulsating-bubble sound was investigated, as was the impact of ball size, entry velocity, and other factors on the characteristics of the water-entry sound. The results show that by combining the virtual-source method with the time-domain integral in the near field, the energy of the incoming sound can be obtained accurately. The results are consistent with closed-space measurements. The water-entry sound includes the initial impact sound and the pulsating-bubble sound. The energy of the pulsating-bubble sound is 3–5 orders of magnitude larger than that of the initial impact sound. The average power level of the water-entry sound is proportional to the ball size and the 2/3 power of the slamming velocity. The relation between the average power level and the 1/3 power of the kinetic energy is an exponential function with base 10. Based on the kinetic energy variety of metal balls entering the water, an acoustic model of this system is established. The results can be used for reference to other transient sound measurements.

Particle Size Distribution Models for Metallurgical Coke Grinding Products

Six different particle size distribution (Gates–Gaudin–Schuhmann (GGS), Rosin–Rammler (RR), Lognormal, Normal, Gamma, and Swebrec) models were compared under different metallurgical coke grinding conditions (ball size and grinding time). Adjusted R2, Akaike information criterion (AIC), and the root mean of square error (RMSE) were employed as comparison criteria. Swebrec and RR presented superior comparison criteria with the higher goodness-of-fit and the lower AIC and RMSE, containing the minimum variance values among data. The worst model fitting was GGS, with the poorest comparison criteria and a wider results variation. The undulation Swebrec parameter was ball size and grinding time-dependent, considering greater b values (b > 3) at longer grinding times. The RR α parameter does not exhibit a defined tendency related to grinding conditions, while the k parameter presents smaller values at longer grinding times. Both models depend on metallurgical coke grinding conditions and are hence an indication of the grinding behaviour. Finally, oversize and ultrafine particles are found with ball sizes of 4.0 cm according to grinding time. The ball size of 2.54 cm shows slight changes in particle median diameter over time, while 3.0 cm ball size requires more grinding time to reduce metallurgical coke particles.

Proposed method for scale drawing calculating depending on the line detector and length detector

A scale drawing is a significant tool in many fields such as geography, mathematics, and astronomy research as it has a variety of applications, including Google maps. A new way to benefit from the scale drawing in soccer image is presented in this paper. When the distance of the camera is uncertain, the scale drawing can be used to determine the relationship between the ball and players to estimate the ball size and determine the zooms in and out. The scale drawing and factor are used in architecture and image processing. After calculating the scale factor, the length of every part or line in the image can be computed by multiplying the original length by the scale factor. The research findings indicated that the proposed work was successful in computing the scale drawing in two ways, namely, line detector and length detector, with approximate results to the desired results

The Synthesis of Hydroxyapatite Powder Using Shaker Mill Technique

Hydroxyapatite is a material that has the same structure and composition as the main minerals of human teeth and bones. This study's purpose was hydroxyapatite synthesis and determining the effect of variations in the ball sizes, the ratio of a mass of precursors to balls size, milling time, and ball size ratio of crystals and particles, surface area and morphology of hydroxyapatite produced by the mechanochemical method. Two different ball sizes (3mm and 6mm) and three different powder to ball ratio of 1:1.44; 1:2.88; and 1:4.32 were milled for 6 hours. Furthermore, the ball size ratio between the small ball (3 mm) and large ball (6 mm) was 1:1, 1:3, and 3:1 were milled for 2, 4, and 6 hours. The synthesized powder was analyzed by X-ray diffraction, Particle Size Analysis, Brunauer-Emmet-Teller analysis, and Scanning Electron Microscopy to confirm hydroxyapatite structure formation with nanocrystallite size and morphology in all variables. The crystallite size increased as the powder to ball ratio increased. The surface area at powder to ball ratio of 1:2.88 and ball size of 3 mm was 19.51 m2/g, while at ball size ratio of 1:1, it was 18.82 m2/g. The morphology of hydroxyapatite was uniform to granular with mol ratio Ca/P 1.81 for powder to ball ratio and ball size variation.