Breakage Properties Research Articles

Anisotropic Effective Moduli of Cracked Short-Fiber Reinforced Composites

A model is presented to analyze the effect of fiber fracture on the anisotropic elastic properties of short-fiber reinforced composite materials. The effective moduli of the material are modeled using a self-consistent scheme which includes the calculated energy dissipated through the opening of a crack in an arbitrarily oriented elliptical inclusion. The model is an extension of previous works which have modeled isotropic properties of short-fiber reinforced composites with fiber breakage and anisotropic properties of monolithic materials with microcracks. Two-dimensional planar composite systems are considered. The model allows for the calculation of moduli under varying degrees of fiber alignment and damage orientation. In the results, both aligned fiber systems and randomly oriented fiber systems with damage-induced anisotropy are examined.

The CSIRO Hopkinson Bar Facility for large diameter particle breakage

The new CSIRO Hopkinson Bar Facility has been commissioned at the Queensland Centre for Advanced Technologies in Brisbane, Australia. Similar devices, such as the Ultra Fast Load Cell (UFLC) at the Utah Comminution Centre have proven to be extremely useful in providing fundamental breakage data of particulate material. In addition to its 19 mm and 60 mm diameter Hopkinson bars, the new CSIRO facility includes a large 100 mm Hopkinson Bar. This large diameter carbon steel load cell is instrumented with highly sensitive semi-conductor strain gauges that give it a force resolution of less than 100 Newtons, permitting precise measurement of the energy to fracture large mineral particles. The device's ability to measure breakage properties, such as first fracture force and energy, of large particles up 100 mm is unique. Breakage data for iron ores over a wide size range is presented. The well known comminution result of increasing particle strength and fracture energy with decreasing particle size was confirmed for the iron ores tested. The influence of iron ore mineralogy and texture was also noted.

A Mineral Liberation Model for Confined Particle Bed Breakage

ABSTRACT The advent of High Pressure Grinding Rolls technology in the minerals industry has created an interest in the particle bed mode of breakage, not only because of its energy saving qualities, but also due to its apparent enhanced mineral liberating properties. Little scientific evidence exists to substantiate any enhanced liberation properties. Automated image analysis and stereological correction methods have now made it possible to measure mineral liberation quite accurately. A population balance mineral liberation model, based on QEM*SEM liberation data of confined particle bed breakage products of a binary ion oxide core, is presented. The selective breakage observed, due to the differential breakage properties of the respective phases, is described. Preferential breakage is incorporated into a liberation model for the first time.

96/05749 Breakage of coals in ring-roller mills. Part I. The breakage properties of various coals and simulation model to predict steady-state mill performance

96/05749 Breakage of coals in ring-roller mills. Part I. The breakage properties of various coals and simulation model to predict steady-state mill performance

Breakage of coals in ring-roller mills Part I. The breakage properties of various coals and simulation model to predict steady-state mill performance

The objectives of the present study are to clarify breakage properties of coals in ring-roller mills and to develop a mathematical mill model capable of predicting steady-state mill performance in full scale mills. It was found that ring-roller mills have a higher coal grinding capability than ring-ball mills with an equal grinding efficiency. It was also demonstrated that breakage characteristics of coals in the mill could not be predicted by the conventional Hardgrove grindability index, HGI, under low filling conditions. On the basis of basic experimental results, a mathematical model was constructed to describe the behaviour in the mill. The model proposed here is based on breakage parameters determined form a batch ring-roller mill and utilizing a new scale-up rule employing apparent grinding energy rates in the batch ring-roller mills as well as large scale ring-roller mills. Furthermore, empirical rule of classification were also added to the mill model. The validity of the model was verified thereafter in large scale mills.

Modelling the new LKAB Kiruna concentrator with USIM PAC©

LKAB has started the construction of a new concentrator at Kiruna, with a capacity of 5 Mtpy. The flowsheet of the new grinding circuit is technically innovative and critical because it entirely relies on ore breakage properties. It includes primary fully autogenous closed circuit grinding and secondary pebble milling. A critical size class of the magnetite ore is extracted from the autogenous mill and used as pebbles. In 1992, LKAB decided to adapt and use a simulator of the new concentrator. USIM PAC© was selected as the support software package, and a modelling team was set up, including both specialists of process modelling and simulation and specialists of the process itself. Specific model development included development of a phenomenological population balance pebble mill model, and adaptation of an existing Control International autogenous mill model. Model parameters were derived from extensive large scale pilot plant tests, and specific laboratory tests were performed to determine pebble mill breakage and selection functions for various types of pebbles and of ores. The simulator was used by the project team for comparing alternative flowsheets (one or two lines, various refinements), for predicting the influence of changes in throughput and plant feed grade, and for evaluating several options for equipment sizes. Additionally, the simulator helped understanding the process in depth and the way the unit operations interact in this particular case.

DNA single and double strand breaks induced by aliphatic and aromatic aldehydes in combination with copper (II).

The aliphatic n-butyr-and n-valeraldehyde as well as the aromatic benz- and anisaldehyde induced DNA strand breaks in PM2 DNA in the presence of CuCl2. Neither aldehydes nor CuCl2 alone showed DNA breakage properties. The maximum of single strand breaks (SSBs) induced by the combination of CuCl2 and aldehydes was dependent on the CuCl2-concentration. The aliphatic aldehydes induced SSBs and double strand breaks (DSBs) at lower concentrations than aromatic aldehydes when optimal CuCl2 concentration were used. Catalase and neocuproine nearly completely inhibited strand break formation induced by aromatic aldehydes/CuCl2. The prevention of strand breaks induced by aliphatic aldehydes/CuCl2 was less effective. While the inhibition by neocuproine was only 25%, catalase was totally ineffective. In all aldehydes/CuCl2 mixtures the formation of Cu(I) was observed. The results point to different DNA damaging species produced during redox reactions of aromatic and aliphatic aldehydes in combination with CuCl2.

Investigation of the breakage properties of components in mixtures ground in a batch ball-and-race mill

Investigation of the breakage properties of components in mixtures ground in a batch ball-and-race mill

Investigation of the Breakage Properties of Components in Mixtures Ground in a Batch Ball-and-Race Mill

The breakage characteristics of mixtures of materials were investigated in a laboratory ball-race mill. A study of the grinding kinetics of the components in a binary mixture showed that the breakage rate of one material was affected by the presence of the other material. The breakage rate of the relatively weaker material increased and, conversely, the breakage rate of the stronger material decreased. The degree of the change in the breakage rate was dependent on the blending ratio and the relative difference in the «strength» of the component. Because there was a consistent pattern, an empirical relationship for this variation was developed. The breakage distribution values of the stronger material were found to be independent of whether the material was ground alone or as a component in a binary mixture. However, the breakage distribution values of the weaker material appeared to change, producing more fines when ground in a binary mixture. Thus, the proportion of the stronger material in the coarser size fractions of the product is greater after mixing the two feed materials and grinding them than after grinding the two materials separately and mixing the products. A similar variation in the breakage rates was observed for a three-component system. The breakage rate decrease of the strongest material and the breakage rate increase of the weakest material were very close to those observed for a binary mixture. However, the breakage rate of the intermediate hardness material stayed essentially the same, even though a slight decrease was expected

Breakage properties of ore blends

The blending of different ore types is common practice to provide a consistent feed to a process either in terms of uniform assay or rock hardness. When several different deposits of varying grindabilities are blended prior to grinding, the hardness of the ore blend is usually estimated as the average of the component grindabilities. It is often suspected that this is not the real case. Investigations were therefore carried out to determine the variation of the Bond Work Index ( W i ) of an ore blend as a function of blend composition. Bond Work Index measurements were carried out on a sample of 100% pure hard rock ( W i = 14) and 100% soft rock ( W i = 6) and three blends of the two components. The work indices were measured by the Bond method and the Magdalinovic method. Both methods gave comparable results for the pure components but differed markedly for the blends. The work index, as measured by the Bond method, did not give a linear relationship with blend composition but was weighted towards the harder component. This would indicate that it is mainly the harder component which is comprising the circulating load. In the Magdalinovic method, no recycle streams are employed and the resultant work index measurement more closely follows a linear relationship with blend composition. As an aid to the understanding of the grinding mechanisms and interactions taking place in the mill, analysis of the breakage properties (breakage distribution function and breakage rate) of each pure component and the blends were also carried out. Qualitative analysis of the breakage properties suggests there is an interaction between the components of the blend which affects their individual breakage rates. From these results, breakage properties of the harder material appears to have a greater influence on the overall breakage properties and the Bond Work Index of the blend than the softer material. Attempts were made to use the measured breakage parameters and the batch grinding equation to simulate the Bond Work Index test and hence calculate the W i .

Simulation of charge motion in ball mills. Part 1: experimental verifications

A numerical tool known as the discrete element method (DEM) is used to study the motion of the ball charge in ball mills. In particular, the motion of individual balls in the ball charge is simulated. An interesting aspect of this simulation is that it yields the frequency distribution of ball collisions as a function of collision energy. The results of numerical simulations are compared with experiments: The angular positions of the toe and shoulder, the trajectory of two balls, and the power draft — all of these predictions are reasonably close to experimental measurements. An interesting sidelight of this study is that the collision frequency can be combined with the breakage property of particles to carry out direct simulation of particle fragmentation in ball mills. The rudiments of such a simulation are illustrated.

２成分粒子の単体分離に関する研究 第１報 粉砕‐単体分離モデルによる構成鉱物粒径分布の推定

Two-phase comminution-liberation model is developed to investigate the effects of raw material properties and operating conditions on mineral liberation. To represent the raw material properties, the distribution function on the constituent mineral grain size is proposed by the introduction of run theory.The simulation results indicate how the mineral grain size and the size of progeny particles after comminution affect mineral liberation. It is also shown that the fractional degree of mineral liberation (FDL), i. e., degree of mineral liberation at a constant particle size, is independent of the reduction ratio, while the shape of FDL curve does not change by the breakage properties and content of valuables.

Cell line selectivity and DNA breakage properties of the antitumour agent N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide: role of DNA topoisomerase II

N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide (NSC 601316) is a DNA intercalating experimental antitumour agent which is curative against the Lewis lung carcinoma in mice. Its action has been compared with amsacrine, its inactive isomer oAMSA, the solid tumour active derivative CI-921 (NSC 343499), a C-6 methylene chain-linked bisacridine (NSC 210733), 9-aminoacridine and quinacrine. All compounds inhibited the unknotting of phage P4 DNA by topoisomerase II in nuclear extracts prepared from L1210 cells. NSC 601316 inhibited growth of cultured L1210, P388, P/AMSA (P388 resistant to amsacrine) and P/ACTD (resistant to actinomycin D) cell lines at concentrations of 87, 150, 2020 and 150 nM respectively. A 1 h drug exposure to 0.85 μM NSC 601316 killed 50% of L1210 cells. L1210 cells treated for 1 h with NSC 601316 accumulated DNA breaks and protein-DNA crosslinks. There was a good correlation between DNA breakage and cytotoxicity, but the relationship between drug concentration and number of protein-DNA cross-links was non-linear and differed from that of amsacrine and CI-921. There was also a positive correlation between the degree of cross-resistance of P/AMSA cells (which have altered topoisomerase II function) and ability to induce DNA breakage or protein-DNA complexes. The results suggest that topoisomerase II is the target of action of NSC 601316.

Breakage properties of some materials in a laboratory ball mill : Austin, L G; Bagga, P; Celik, M Powder Technol, V28, 1981, P235–241

Breakage properties of some materials in a laboratory ball mill : Austin, L G; Bagga, P; Celik, M Powder Technol, V28, 1981, P235–241

The Effect of Rotor Fiber Groove Design on Trash Accumulation, End Breakage, and Yarn Properties1

The trash accumulation and end breakage from an experimental rotor with a narrow, deep V-type fiber groove was compared with that from a conventional rotor with a wider, rounded fiber groove. Then the trash accumulation and end breakage characteristics of experimental and conventional rotors with holes in the periphery were compared to those without holes, both with the trash cleaner in and out of operation. The V-type fiber groove had greater trash accumulation but fewer end breaks and appeared to yield stronger, more uniform yarn at high rotor speeds. Rotors with holes in the periphery were most effective in regards to rotor trash, end breakage, and yarn properties when spinning coarse counts from a relatively clean cotton.

Breakage properties of some materials in a laboratory ball mill

Crystalline quartz, silicon carbide, three coals of different rank and a cement clinker were studied in a small laboratory ball mill under standard conditions. The first-order specific rates of breakage and the cumulative primary daughter fragment distributions were determined. Two coals showed a slowing down of breakage rate at fine dry grinds. Anthracite showed an acceleration of grinding rate. Wet grinding was first order in all cases even to very fine grinds. Wet grinding was always faster than dry grinding for a given material but the shapes of the size distributions were the same within experimental variability.