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Concrete is an essential construction material, and infrastructures, such as bridges, tunnels, and power plants, consume large quantities of it. Future infrastructure demands and sustainability issues necessitate the adoption of non-conventional supplementary cementitious materials (SCMs). At the same time, global labor shortages are compelling the conservative construction sector to implement autonomous and digital fabrication methods, such as 3D printing. This paper thus investigates the feasibility of using oil shale ash (OSA) as an SCM in concrete suitable for 3D printing, and collision milling is examined as a possible ash pretreatment. OSA from four different sources was collected and analyzed for its physical, chemical, and mineralogical composition. Concrete formulations containing ash were tested for mechanical performance, and the two best-performing formulations were assessed for printability. It was found that ash extracted from flue gases by the novel integrated desulfurizer has the greatest potential as an SCM due to globular particles that contain β-calcium silicate. The 56-day compression strength of concrete containing this type of ash is ~60 MPa, the same as in the reference composition. Overall, collision milling is effective in reducing the size of particles larger than 10 μm but does not seem beneficial for ash extracted from flue gasses. However, milling bottom ash may unlock its potential as an SCM, with the optimal milling frequency being ~100 Hz.

Mineral additives are materials which are used in wide range of industries including construction, cosmetics, agricultural and biotechnology. Such materials as plasters, paints, abrasives etc. are produced using mineral powders. Main qualities of mineral additives are purity of chemical composition, grading properties and shape factor. To obtain powder like material most common method is milling. One of most effective milling method for refining of brittle material is grinding by collision in disintegrator. One of advantage of this method is that high milling energy is transferred to the milling material in short period of time. In present research three types of mineral materials were treated in disintegrator with specific energy Es applied 8.4 and 25.2 kWh/t: natural quartz sand 0.3/1mm, quartz-limestone 0.3/2.5mm sand and dolomite screenings 0/4mm. Results indicate that powder like material with d90 form 66 to 141 µm could be obtained at Es 8.4 kWh/t while increase of Es reduces d90 value to 48 to 72 µm and the milling efficiency was effected by the sand type.

Ball milling is a representative mechanochemical strategy that uses the mechanical agitation-induced effects, defects, or extreme conditions to activate substrates. Here, we demonstrate that ball grinding could bring about contact-electro-catalysis (CEC) by using inert and conventional triboelectric materials. Exemplified by a liquid-assisted-grinding setup involving polytetrafluoroethylene (PTFE), reactive oxygen species (ROS) are produced, despite PTFE being generally considered as catalytically inert. The formation of ROS occurs with various polymers, such as polydimethylsiloxane (PDMS) and polypropylene (PP), and the amount of generated ROS aligns well with the polymers’ contact-electrification abilities. It is suggested that mechanical collision not only maximizes the overlap in electron wave functions across the interface, but also excites phonons that provide the energy for electron transition. We expect the utilization of triboelectric materials and their derived CEC could lead to a field of ball milling-assisted mechanochemistry using any universal triboelectric materials under mild conditions. Through contact-electro-catalysis (CEC), reactive oxygen species can be produced by chemically inert triboelectric materials in ball milling, enabling mechanoredox reactions with a broad selection of abundant triboelectric materials

In 5-axis machining, the existing tool’s axis vector optimization methods are limited since they only consider the global collision between the tool and the workpiece while aiming at the ball-nosed cutter. A multi-factor vector optimization method for the face milling cutter shaft is proposed to solve this problem. This method comprehensively considers machining global collision, cutting force, the angular displacement of a rotating shaft, and angular speed. An improved global collision detection method of cutter axis vector based on the NURBS surface principle is developed, and a global collision detection algorithm is employed to determine the cutter machining global collision. The relationship model between the end-milling cutter axis vector and cutting force variation is established to optimize the cutting force. In addition, an optimization model of angular displacement and velocity of the machine tool’s rotating axis is proposed based on Dijkstra optimal path algorithm. The CAM software simulation and experimental validation are conducted using a large propeller with a complex surface. The tool’s axis vector optimization algorithm is applied to the propeller results. Comparing the tool’s axis vector optimization results to those obtained without optimization, it is discovered that the surface workpiece’s machining quality has significantly increased.

Plunge milling, as a recognized high-efficiency metal cutting process, is an ideal choice for roughing machining of deep groove and cavity parts. However, due to the severe cutting load of plunge milling, especially the problem of plunge milling collision, and the lack of cavity plunge milling process, its engineering application has always been unsatisfactory. In this paper, starting from the cutter design, the inward-inclined structure of cutting edge is proposed, which can effectively avoid the sharp increase in cutting load caused by plunge milling collision, and realize in situ cutter retraction. At the same time, the dislocation chip-separation structure of cutting edge is also proposed, which can effectively reduce the plastic deformation of cutting layer, and the maximum cutting force is reduced by about 55%. Based on the design of the above high-performance plunging cutter, considering the constraints of material residue and isolated corner, the plunging milling process strategies for open cavity, semi-closed cavity and closed cavity are planned. Finally, the influence law of machining parameters on cutting force is explored. The setup series of verification experiments show that the inward-inclined structure and dislocation chip-separation structure of plunge milling cutter are reasonable, and the process strategies and machining parameters of cavity plunge milling are feasible. Compared with the traditional layer milling, the machining efficiency is increased by about 3.3 times.

Abstarct Mechanochemical methodologies, particularly ball milling, have become commonplace in many laboratories. In the present work, we examine the effects of milling ball mass on the polymorphic conversion of anhydrous caffeine. By investigating a single-phase system, the rate-limiting step of particle–particle contact formation is eliminated. It is found that larger milling balls lead to considerably faster conversion rates. Modelling of the transformation rate suggests that a single, time-independent rate constant is insufficient to describe the transformation. Instead, a convolution of at least two rate-determining processes is required to correctly describe the transformation. This suggests that the early stages of the transformation are governed only by the number of particle–ball collisions. As the reaction proceeds, these collisions less frequently involve reactant, and the rate becomes limited by mass transport, or mixing, even in originally single-phase systems, which become multi-phase as the product is formed. Larger milling balls are less hindered by poorly mixed material. This likely results from a combination of higher impact energies and higher surface areas associated with the larger milling balls. Such insight is important for the selective and targeted design of mechanochemical processes.

Pinch milling is a new technique for slender and long blade machining, which can simultaneously improve the machining quality and efficiency. However, two-cutter orientation planning is a major challenge due to the irregular blade surfaces and the structural constraints of nine-axis machine tools. In this paper, a method of twin-tool smoothing orientation determination is proposed for a thin-walled blade with pinch milling. Considering the processing status of the two cutters and workpiece, the feasible domain of the twin-tool axis vector and its characterization method are defined. At the same time, an evaluation algorithm of global and local optimization is proposed, and a smoothing algorithm is explored within the feasible domain along the two tool paths. Finally, a set of smoothly aligned tool orientations are generated, and the overall smoothness is nearly globally optimized. A preliminary simulation verification of the proposed algorithm is conducted on a turbine blade model and the planning tool orientation is found to be stable, smooth, and well formed, which avoids collision interference and ultimately improves the machining accuracy of the blade with difficult-to-machine materials.

Abstract In mirror milling of thin-walled parts, the machining path and change in tool axis vector will affect the surface quality of the workpiece and machining efficiency. Reasonable planning of the tool axis vector can avoid the occurrence of overcutting and undercutting and prevent a collision between the tool and the workpiece and damage of the spindle. At the same time, the rapid change in tool axis vector will also affect the machining quality, so optimization of the tool axis vector is very important in mirror milling. In this paper, the optimization of the tool axis vector for titanium alloy skin processing is divided into two steps. The first optimization is carried out on the basis of the planning of the machining path. First, the machining path is obtained according to constraints of mirror milling, and the iterative algorithm of the tool position is used. The tool location point is obtained, and then the tool location point is projected onto the parameter plane to optimize the tool axis vector. The second optimization is to optimize the tool axis vector based on kinematic constraints. The rotation axis of the machine tool needs to meet the constraints of the maximum angular velocity, the maximum angular acceleration, and the maximum angular jerk. First, the optimal feed rate of the mirror milling machine tool is obtained. The tool axis vector is optimized for optimization goals with minimum motion fluctuation stop and minimum adjacent machining time. Subsequently, the optimized machining path and the tool axis vector were simulated and tested. Finally, the simulation and experimental results were determined by an analysis that proved the feasibility of the optimized model proposed in this paper. At the same time, the results of the experimental measurements also showed that the optimized machining path had been greatly improved in terms of quality and efficiency.

Mechanochemical and mechanical alloying processes take place between colliding surfaces in the heavy container of a ball mill, where the in situ examination of the reaction mechanism is extremely challenging. As shown in this paper, useful indirect information can be obtained from detailed analysis of the reaction kinetics. A shaker mill with a single ball was used, so that time could be replaced with the number of collisions as the variable of kinetics. A simple stochastic model was developed that is capable of describing the kinetics of gradual mechanochemical reactions and the variation of physical properties such as grain size. The kinetic constant is directly related to the fraction of powder processed in a single collision, and its value indicates that only a few micrograms of powder are processed in a single collision. Measuring the kinetic constant as a function of impact energy revealed that a minimum impact energy, on the order of a few hundreds of a Joule, is needed to initiate chemical change. The model was also applied to the self-sustaining reaction between Ti and graphite. In that case, the critical number of collisions required for ignition characterizes the speed of mechanical activation.

In five-axis machining of blisk, the filleted end mill has attracted more and more attention because of its larger cutting width. However, it is still a hard work to find the tool posture without interference. In this paper, a method is proposed to solve the collision-free regions. Based on the visibility of free-form surface, a tool-surface tangent model of the filleted end mill is established. With the model, only critical points on profiles of checking surface are searched with a self-adapting step length and the corresponding critical vectors are calculated and mapped to construct the collision-free regions. Firstly, critical points on the boundaries are searched according to the given precision. Meanwhile, the corresponding critical vectors are calculated and some special searched points are selected as the endpoints of each profile. Then, the adjacent critical points are searched along the profile by adjusting iteratively with a self-adapting step length in the parameter domain one by one. During the search, the corresponding critical vectors are calculated too. After that, the critical vectors are mapped to construct the subinterval collision-free regions in two-dimensions. And a method is adopted to combine collision-free regions. This algorithm is finally verified with a closed blisk and compared with a referenced method. The results show that it can efficiently solve collision-free regions in five-axis milling of blisk with a filleted end mill.