Nonlinear transient engagement characteristics of planetary gear train

Based on the engagement principle of the gear drive, the nonlinear transient dynamic characteristics of the planetary gearing are researched and the corresponding dynamic equilibrium equations for sun gear, planet gear and internal gear are respectively derived. Then transient engagement simulation analysis of the planetary gear train is performed in ANSYS. The corresponding stress-time curves of sun gear, planet gear and internal gear are obtained, and the worst engaging location and the ultimate stress in every gear are calculated accurately. The simulation experiment shows that the engagement characteristics of the planetary gearing at any time and in any location can be accurately analyzed by transient engagement analysis. It provides a reliable guaranty for the subsequent fatigue analysis and structural optimization of the planetary gear train

Pose Adjusting Simulation of Hydraulic Support Based on Mechanical-Electrical-Hydraulic Coordination

The pose variations of the hydraulic support have significant influence on its performance. And the pose adjusting operations are required to be fast and precise, while they have typical mechanical-electric-hydraulic coordination characteristics which are challenging to simulate. In view of these problems, a method has been proposed in this work for accurately monitoring and controlling the pose of the hydraulic support, and using a suitable multi-software co-simulation model to simulate it. A mathematical model for pose monitoring and control was initially established.A teaching-learning-based optimization algorithm (TLBO) was then introduced to obtain the numerical solution of the nonlinear equations.Finally, a numerical model based on mechanical-electrical-hydraulic co-simulation was established. The model was tested and validated by using different pose signals. The results indicate that the pose controller developed in this paper can control the support pose well (iteration time less than 1 s and cumulative error less than 1.5 mm). Moreover, the multi-software co-simulation approach was effective for describing the complex system. The co-simulation platform proposed in this study can benefit the virtual monitoring technology for hydraulic supports.The research provides theoretical basis and technical guidance for the automation and unmanned control of underground mining

Numerical Simulation of Fragment Separation during Rock Cutting Using a 3D Dynamic Finite Element Analysis Code

To predict fragment separation during rock cutting, previous studies on rock cutting interactions using simulation approaches, experimental tests, and theoretical methods were considered in detail. This study used the numerical code LS-DYNA (3D) to numerically simulate fragment separation. In the simulations, a damage material model and erosion criteria were used for the base rock, and the conical pick was designated a rigid material. The conical pick moved at varying linear speeds to cut the fixed base rock. For a given linear speed of the conical pick, numerical studies were performed for various cutting depths and mechanical properties of rock. The numerical simulation results demonstrated that the cutting forces and sizes of the separated fragments increased significantly with increasing cutting depth, compressive strength, and elastic modulus of the base rock. A strong linear relationship was observed between the mean peak cutting forces obtained from the numerical, theoretical, and experimental studies with correlation coefficients of 0.698, 0.8111, 0.868, and 0.768. The simulation results also showed an exponential relationship between the specific energy and cutting depth and a linear relationship between the specific energy and compressive strength. Overall, LS-DYNA (3D) is effective and reliable for predicting the cutting performance of a conical pick

Anti-osteoporosis effect of Notopterygium incisum Ting ex H. T. Chang extract in rats

Purpose: To investigate the effect of Notopterygium incisum Ting ex H.T. Chang extract (NICE) on ovariectomy-induced osteoporosis in rats. Methods: Female Sprague-Dawley rats were randomly assigned to a normal group (control) and five ovariectomy (OVX) subgroups: OVX with vehicle (OVX), OVX with positive control drug alendronate sodium tablets (1.8 mg/kg/week), and OVX with varying NICE doses (45, 90, or 180 mg/kg/day). After rats were subjected to ovariectomy for 4 weeks, alendronate or NICE were administered orally daily for 16 weeks. The bone mineral density (BMD) of the L4 vertebrae and right femurs of all rats was estimated. The serum hormones estradiol (E2), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels and serum alkaline phosphatase (ALP), osteocalcin (OC) and telopeptides of collagen type I (CTx) levels of rats were detrmined. Results: The results show that NICE dose-dependently inhibited bone mineral density (BMD) reduction of L4 vertebrae and femurs (p < 0.05). Compared with OVX group, serum E2, FSH and LH levels was significantly increased in osteoporosis rats (p < 0.01), but serum ALP, CTx, and OC concentrations were significantly lower (p < 0.05). On the other hand, bone trabeculae in the three NICE groups and nilestriol group were all wider, while the space and connections increased. Conclusion: These findings indicate that NICE mitigates OVX-induced osteoporosis in rats, and hence can potentially be developed for the management of osteoporosis

Dynamic characteristics analysis on shearer drum in condition of cutting coal with different distributed rocks

Dynamic characteristics analysis on shearer drum is an important aspect in shearer design and a well-structured shearer drum provides better performance in vibration reduction and service life extension. To make reference for structure improvement, many researchers have focused on the dynamic analysis on cutting pick. However, the simplified model such as single pick, linear motion and continuous coal in the previous study made it divorced from actual situations underground. On basis of this, the model of shearer drum with several arranged picks and the coal model with some distributed rock have been set up in order to consist with the real working conditions. Through simulation, it can be found that the mean force in X-direction is little influenced by rock distribution, but the peak force in X-direction fluctuates greatly under different rock distribution. During the analysis on the peak force, it can be found that this kind of force could be cut down effectively when the rock was distributed on the top of the shearer cutting range. Based on these conclusions, we can program the cutting strategy to lower the influence of cutting forces on the shearer and its drum in the future

Study on Roadheader Cutting Load at Different Properties of Coal and Rock

The mechanism of cutting process of roadheader with cutting head was researched, and the influences of properties of coal and rock on cutting load were deeply analyzed. Aimed at the defects of traditional calculation method of cutting load on fully expressing the complex cutting process of cutting head, the method of finite element simulation was proposed to simulate the dynamic cutting process. Aimed at the characteristics of coal and rock which affect the cutting load, several simulations with different firmness coefficient were taken repeatedly, and the relationship between three-axis force and firmness coefficient was derived. A comparative analysis of cutting pick load between simulation results and theoretical formula was carried out, and a consistency was achieved. Then cutting process with a total cutting head was carried out on this basis. The results show that the simulation analysis not only provides a reliable guarantee for the accurate calculation of the cutting head load and improves the efficiency of the cutting head cutting test but also offers a basis for selection of cutting head with different geological conditions of coal or rock

Analysis on the Effect of Slideway Friction to the Slider-Type Hydraulic Powered Support

This paper presents a design concept of the slider-type hydraulic powered support. The equivalent mechanical model is established when the hydraulic powered support supporting the stable roof pressure and deriving the numerical calculation formula of the supporting efficiency is based on the slideway frictional coefficient. Meanwhile, theoretical solutions of supporting efficiency at different working heights are obtained. On this basis, the rigid-flexible coupling simulation model of the support was established by using Hypermesh and Adams and the dynamic simulation was carried out under the condition that the roof is bearing the stable pressure, and finally, obtaining the force response curves and the simulation solutions of the supporting efficiency. The final analysis shows the following: The slider-type powered support is suitable for working at high position; with the increase of the friction coefficient between the slider and the slideway, the supporting efficiency increases gradually, the working safety and reliability are enhanced, furthermore, its shock resistance and stability are enhanced

Optimization design for roadheader cutting head by orthogonal experiment and finite element analysis

U radu se istražuje optimizacija konstrukcije rezne glave stroja za bušenje. U tu su svrhu kao varijable optimizacije izabrani brzina rotacije, brzina oscilacije, rezni kutovi pijuka i kutovi nagiba pijuka, a kao ciljevi optimizacije izabrani su srednja vrijednost rezultirajuće sile i koeficijent varijacije reznog opterećenja. Učinci ovih parametara na indekse evaluacije analiziraju se ortogonalnim eksperimentom i analizom konačnih elemenata. Također je provedena analiza promjene trenda indeksa evaluacije s promjenama eksperimentalnih čimbenika. U usporedbi s originalnim projektom, dva indeksa evaluacije smanjila su se za 18,3 % i 5,5 % nakon optimizacije, čime je značajno poboljšana rezna performansa rezne glave stroja za bušenje.Optimization design for roadheader cutting head is investigated in this paper. For this purpose, the rotation velocity, the swing velocity, the cutting angles of picks, and the inclination angles of picks are chosen as the variable for the optimization, and the mean value of resultant force and variation coefficient of cutting load are chosen as optimization objective. The effects of these parameters on evaluation indexes are studied by orthogonal experiment and finite element analysis. The change trend of the evaluation indexes with the experimental factors is also carried out. Compared with the original design, the two evaluation indexes decreased by 18,3 % and 5,5 % after optimization design separately, which improves the cutting performance of roadheader cutting head efficiently

Production information management system of intelligent welding workshop for hydraulic support

In order to ensure intelligent welding process is suitable for production of structural member of support, improve equipment utilization rate, guarantee welding quality, and give full play to advantages of intelligent welding workshop, production information management system of intelligent welding workshop for hydraulic support based on MES was studied. The overall system model and its network architecture were established, functional requirements of the system were analyzed, and the system database model was established. The design of data acquisition module of intelligent welding workshop production information was introduced. The module realizes comprehensive collection of scene information of workshop. The practical application results show that the system realizes effective data communication between enterprise decision-making level and production site, and ensures production quality and efficiency of hydraulic support

Improved deep learning based multi‐index comprehensive evaluation system for the research on accuracy and real‐time performance of coal gangue particles recognition

Abstract The problems of insufficient recognition accuracy, poor real‐time performance and lack of consideration of actual working conditions in the process of intelligent construction of coal mines make this technology still in the research stage and not applied in practical engineering. The purpose of this paper is to establish an accurate and real‐time recognition model, which can quickly distinguish the vibration acceleration signals of coal and gangue under the influence of external factors such as impact position, velocity, and direction by using the different physical properties of coal and gangue particles. Therefore, the accuracy and real‐time of coal gangue recognition model established by different convolutional neural networks (CNN) structures and different position signal input are studied. First, to meet the real‐time requirements, an original CNN recognition model composed of single convolution layer and single pooling layer is established, and the data collected by seven sensors are input in the form of two‐dimensional matrix. However, the stability of the training and test results is insufficient. To solve this problem, once improved CNN (OI‐CNN) recognition model with multiconvolution layers and multipooling layers is built by deepening the network. The experimental results show that the stability and accuracy are improved, but the real‐time performance is poor. Furthermore, through parameter adjustment, the OI‐CNN is changed to the twice improved CNN (TI‐CNN), and the sensor data at different positions are input in the form of one‐dimensional vectors. The results show that the accuracy and real‐time performance of the TI‐CNN coal gangue recognition model are further improved. Finally, according to the research purpose of this paper, the weights of CNN indexes are given, and a multi‐index comprehensive evaluation system (MICES) is established. With the original CNN recognition model as the control, the OI‐CNN recognition model and the TI‐CNN recognition model at different positions are quantitatively compared to obtain the comprehensive evaluation scores of each model. The results show that the MICES of the coal gangue recognition model established based on the TI‐CNN structure and the data input of a single position sensor is the highest, while the sensor position has little effect on the recognition results