WAYS TO INCREASE THE EFFICIENCY OF ENGINEERING PROCESSES WHEN FORMING HIGH-DENSITY ARRAYS OF DISPERSE MATERIALS

One of the most important production operations in open pit mining is dumping. The depth of open pit mines increases constantly and the volume of overburden rocks also grows. Overburden is truck-delivered to the dumps. Fractional composition of overburden is diverse. In the early years, loose rocks were transported to the dumps from the upper horizons to the lower levels of the dumps, and in subsequent years - hard rocks. In this view, due to the low strength and stability of the dump mass, it is usually not possible to provide safe working conditions. The mining safety can be increased due to the compaction of rocks composing the dump mass. Based on the analysis of technologies for compaction of dispersed materials using known equipment, a self-propelled vibration device is proposed for the formation of a stable dump mass. The use of a vibrating function element in the design, which implements a polyharmonic vibration mode, will expand the scope of its application during the open pit mining.

TO THE PROBLEM OF CREATING LARGE DUMP TRUCKS WITH ACTIVE BODIES

An analytical review of existing dump trucks with forced unloading of the body, implemented using hydraulic or mechanical devices built into its structure, as well as due to the vibration effect of automobile on-site vibration exciters fixed on the body walls, is given. The possibility of using the transporting devices with an elastic function element, developed at the Institute of Mining of the Siberian Branch of the Russian Academy of Sciences, as a false bottom of the body of large dump truck and the need to equip them with self-synchronizing inertial vibration exciters has been substantiated. The procedure and results of experimental studies of the dynamics of elastic function elements with different rigidity, equipped with two unbalanced vibration sources have been presented. Geometric and dynamic ratios that ensure the stability of synchronous operation of vibration exciters in conditions of a change in the technological load on the surface of a function element due to the release of bulk material from the body have been found. The degree of vibration isolation of vibrotransporting devices from the supporting structure of a dump truck has been experimentally determined.

Optimized control over modes of hydraulic percussion cutting heads of mining machines

The main cause of the disagreement between the actual and calculated output data of hydraulic percussion mining machines is the erroneous feed of manipulation signals by the control units. For the maximal fitting of the calculated and actual figures, the continuous method of control action using the third time derivative of the law of motion of the main function element is accepted, namely, the accuracy. The mathematical models of control using displacement, velocity and acceleration are developed. The service factors of mining machines are found. Based on the theory of control and the mathematical logic theory, the logical circuits of formation of manipulation signals in each phase of the working cycle are developed. The main elements are converters, integrators and accumulators ensuring decomposition of elements of the logical circuits and further generation of appropriate control action. It is found that the simplest way is to generate the control action for acceleration of the key function element. For the developed circuits, it is recommended to use general charts of the control action change, implementable for a certain design of hydraulic percussion cutting heads in certain operating conditions.

Some advances in high-performance finite element methods

Purpose The purpose of this paper is to give a review on the newest developments of high-performance finite element methods (FEMs), and exhibit the recent contributions achieved by the authors’ group, especially showing some breakthroughs against inherent difficulties existing in the traditional FEM for a long time. Design/methodology/approach Three kinds of new FEMs are emphasized and introduced, including the hybrid stress-function element method, the hybrid displacement-function element method for Mindlin–Reissner plate and the improved unsymmetric FEM. The distinguished feature of these three methods is that they all apply the fundamental analytical solutions of elasticity expressed in different coordinates as their trial functions. Findings The new FEMs show advantages from both analytical and numerical approaches. All the models exhibit outstanding capacity for resisting various severe mesh distortions, and even perform well when other models cannot work. Some difficulties in the history of FEM are also broken through, such as the limitations defined by MacNeal’s theorem and the edge-effect problems of Mindlin–Reissner plate. Originality/value These contributions possess high value for solving the difficulties in engineering computations, and promote the progress of FEM.

Bioinspired Simultaneous Changes in Fluorescence Color, Brightness and Shape of Hydrogels Enabled by AIEgens

Development of stimuli-responsive materials with complex practical functions is significant for achieving bioinspired artificial intelligence. It is challenging to fabricate stimuli-responsive hydrogels showing simultaneous changes in fluorescence color, brightness and shape in response to one stimulus. Herein a bilayer hydrogel strategy was designed by utilizing an aggregation-induced emission luminogen (AIEgen) tetra-(4-pyridylphenyl)ethylene (TPE-4Py) to fabricate hydrogels with the above capabilities. Bilayer hydrogel actuators with ionomer of poly(acrylamide-r-sodium 4-styrenesulfonate) (PAS) as matrix of both active and passive layers and TPE-4Py as the core function element in the active layer were prepared. At acidic pH, the protonation of TPE-4Py led to fluorescence color and brightness changes of the actuators and the electrostatic interactions between the protonated TPE-4Py and benzenesulfonate groups of PAS chains in the active layer caused the actuators to deform. The proposed TPE-4Py/PAS-based bilayer hydrogel actuators with such responsiveness to stimulus provide pregnant insights in the design of intelligent systems and are highly attractive material candidates in fields of 3D/4D printing, soft robots and smart wearable devices.

Bioinspired Simultaneous Changes in Fluorescence Color, Brightness and Shape of Hydrogels Enabled by AIEgens

Development of stimuli-responsive materials with complex practical functions is significant for achieving bioinspired artificial intelligence. It is challenging to fabricate stimuli-responsive hydrogels showing simultaneous changes in fluorescence color, brightness and shape in response to one stimulus. Herein a bilayer hydrogel strategy was designed by utilizing an aggregation-induced emission luminogen (AIEgen) tetra-(4-pyridylphenyl)ethylene (TPE-4Py) to fabricate hydrogels with the above capabilities. Bilayer hydrogel actuators with ionomer of poly(acrylamide-r-sodium 4-styrenesulfonate) (PAS) as matrix of both active and passive layers and TPE-4Py as the core function element in the active layer were prepared. At acidic pH, the protonation of TPE-4Py led to fluorescence color and brightness changes of the actuators and the electrostatic interactions between the protonated TPE-4Py and benzenesulfonate groups of PAS chains in the active layer caused the actuators to deform. The proposed TPE-4Py/PAS-based bilayer hydrogel actuators with such responsiveness to stimulus provide pregnant insights in the design of intelligent systems and are highly attractive material candidates in fields of 3D/4D printing, soft robots and smart wearable devices.

Distortion-resistant and locking-free eight-node elements effectively capturing the edge effects of Mindlin–Reissner plates

Purpose A simple shape-free high-order hybrid displacement function element method is presented for precise bending analyses of Mindlin–Reissner plates. Three distortion-resistant and locking-free eight-node plate elements are proposed by utilizing this method. Design/methodology/approach This method is based on the principle of minimum complementary energy, in which the trial functions for resultant fields are derived from two displacement functions, F and f, and satisfy all governing equations. Meanwhile, the element boundary displacements are determined by the locking-free arbitrary order Timoshenko’s beam functions. Then, three locking-free eight-node, 24-DOF quadrilateral plate-bending elements are formulated: HDF-P8-23β for general cases, HDF-P8-SS1 for edge effects along soft simply supported (SS1) boundary and HDF-P8-FREE for edge effects along free boundary. Findings The proposed elements can pass all patch tests, exhibit excellent convergence and possess superior precision when compared to all other existing eight-node models, and can still provide good and stable results even when extremely coarse and distorted meshes are used. They can also effectively solve the edge effect by accurately capturing the peak value and the dramatical variations of resultants near the SS1 and free boundaries. The proposed eight-node models possess potential in engineering applications and can be easily integrated into commercial software. Originality/value This work presents a new scheme, which can take the advantages of both analytical and discrete methods, to develop high-order mesh distortion-resistant Mindlin–Reissner plate-bending elements.