Microstructure and properties of laser cladding of 316L stainless steel on hydraulic support tube

In consideration of the special environmental conditions of coal equipment in mining, the seamless steel tube of hy-draulic prop made of 20^# carbon steel was taken as the substrate, and 316L stainless steel powder was used to clad the sub-strate by a fiber-coupled semiconductor laser. The microstructure of the cladding layer was determined by metalloscope. The hardness, wear resistance and corrosion resistance of the cladding layer were measured. The results show that metallurgy bind-ing interface between the cladding layer and the substrate is obtained without defects such as cracks and pores. The hardness of the cladding layer is much higher than that of the matrix, and the wear resistance and corrosion resistance are simultaneously better. According to the analysis, it is summarized that the improvement in performance of the cladding layer is closely related to the change of microstructure and the thermal effect in the cladding process. The maximum hardness occurs in the equiaxed zone, and with the grain coarsening, the hardness reduces simultaneously. In addition, the precipitated phase, hard particles and trace elements also have a great influence on the properties of the cladding layer, and they will prevent the surface from ab-rasion and reduce the plastic deformation of the matrix. It is verified that the 316L stainless steel is suitable for the 20^# steel in laser cladding repairing process. Since this study focused on coal machine equipment parts, it has certain practical significance for the repair of hydraulic equipment.

Structure optimal design research on backfill hydraulic support

Backfill hydraulic support is the key equipment in achieving coal mining and solid backfilling simultaneously in solid backfill mining technology.Based on the summary and analysis of main types,basic structural properties and filed application of backfill hydraulic support,this work has firstly proposed the basic principle of backfill hydraulic support optimization design and provided the method of optimal design of key structural components,like four-bar linkage,rear canopy and tamping structure;the method is further elaborated as changing hinging position of upper bar to optimize four-bar linkage,by lengthening or shortening the rear canopy to optimize length ratio of canopy;and by changing length and hinging position of tamping structure as well as suspension height of backfill scrape conveyor to realize optimization of tamping structure.On this basis,the process of optimal design of backfill hydraulic support is built.The optimal design case of ZC5200/14.5/30 six columns-four bar linkage used in 7203 W workface of Zhaizhen Coal Mine shows that the backfill properties like horizontal roof gap,vertical horizontal gap,tamping angle and tamping head gap are improved obviously through optimizing four-bar linkage,canopy length and tamping structure according to the optimal design method proposed in this work.

Hydraulic support crushed mechanism for the shallow seam mining face under the roadway pillars of room mining goaf

While the fully-mechanized longwall mining technology was employed in a shallow seam under a room mining goaf and overlained by thin bedrock and thick loose sands, the roadway pillars in the abandoned room mining goaf were in a stress-concentrated state, which may cause abnormal roof weighting, violent ground pressure behaviours, even roof fall and hydraulic support crushed(HSC) accidents. In this case,longwall mining safety and efficiency were seriously challenged. Based on the HSC accidents occurred during the longwall mining of 3-1-2 seam, which locates under the intersection zone of roadway pillars in the room mining goaf of 3-1-1 seam, this paper employed ground rock mechanics to analyse the overlying strata structure movement rules and presented the main influence factors and determination methods for the hydraulic support working resistance. The FLAC3 D software was used to simulate the overlying strata stress and plastic zone distribution characteristics. Field observation was implemented to contrastively analyse the hydraulic support working resistance distribution rules under the roadway pillars in strike direction, normal room mining goaf, roadway pillars in dip direction and intersection zone of roadway pillars. The results indicate that the key strata break along with rotations and reactions of the coal pillars deliver a larger concentrated load to the hydraulic support under intersection zone of roadway pillars than other conditions. The ‘‘overburden strata-key strata-roadway pillars-immediate roof" integrated load has exceeded the yield load that leads to HSC accidents. Findings in HSC mechanism provide a reasonable basis for shallow seam mining, and have important significance for the implementation of safe and efficient mining.

Nonlinear Static and Dynamic Stiffness Characteristics of Support Hydraulic System of TBM

Full-face hard rock tunnel boring machines(TBM)are essential equipment in highway and railway tunnel engineering construction.During the tunneling process,TBM have serious vibrations,which can damage some of its key components.The support system,an important part of TBM,is one path through which vibrational energy from the cutter head is transmitted.To reduce the vibration of support systems of TBM during the excavation process,based on the structural features of the support hydraulic system,a nonlinear dynamical model of support hydraulic systems of TBM is established.The influences of the component structure parameters and operating conditions parameters on the stiffness characteristics of the support hydraulic system are analyzed.The analysis results indicate that the static stiffness of the support hydraulic system consists of an increase stage,stable stage and decrease stage.The static stiffness value increases with an increase in the clearances.The pre-compression length of the spring in the relief valve a ects the range of the stable stage of the static stiffness,and it does not a ect the static stiffness value.The dynamic stiffness of the support hydraulic system consists of a U-shape and reverse U-shape.The bottom value of the U-shape increases with the amplitude and frequency of the external force acting on the cylinder body,however,the top value of the reverse U-shape remains constant.This study instructs how to design the support hydraulic system of TBM.

Dynamic impact experiment and response characteristics analysis for 1:2 reduced-scale model of hydraulic support

It is significant to research the impact resistance properties of hydraulic support due to its key support role in the fully mechanized mining face.However,it is difficult for the entire hydraulic support to implement the impact experiment underground and analyze the response characteristic.Therefore,a dynamic impact experiment for the entire hydraulic support was proposed in this paper,where a 1:2 reducedscale model of hydraulic support was designed and its response characteristics under dynamic impact load were analyzed.Firstly,a comprehensive monitoring scheme was proposed to achieve an effective monitoring for dynamic response of hydraulic support.Secondly,a multi-scale impact experiment was carried out for the entire hydraulic support and dynamic behaviors of hydraulic support under the multi-scale impact load were revealed by experimental data.Then a dynamic impact experiment of the entire hydraulic support was simulated in ADAMS with the same experiment conditions,and the experimental and simulation data were verified mutually.Finally,the characteristics of energy conversion and dissipation of the entire experiment system after impact were analyzed.The experiment results showed that the impact resistance properties of hydraulic support largely depended on the initial support conditions and different vertical rigidities affected energy distribution proportion of the entire support system.

Horizontal roof gap of backfill hydraulic support

For the backfill hydraulic support as the key equipment for achieving integration of backfilling and coal mining simultaneously in the practical process, its characteristics will directly influence the backfill body's compression ratio. Horizontal roof gap, as a key parameter of backfilling characteristics, may impact the backfilling effect from the aspects of control of roof subsidence in advance, support stress, backfilling process and the support design. Firstly, the reason why horizontal roof gap exists was analyzed and its definition, causes and connotation were introduced, then adopting the Pro/E 3D simulation software, three typical 3D entity models of backfill hydraulic supports were built, based on the influence of horizontal roof gap on backfilling effect, and influence rules of four factors, i.e. support height, suspension height, suspension angle and tamping angle, were emphatically analyzed on horizontal roof gap. The results indicate that, the four factors all have significant impacts on horizontal roof gap, but show differences in influence trend and degree, showing negative linear correlation, positive linear correlation, positive semi-parabolic correlation and negative semi-parabolic correlation, respectively. Four legs type is the most adaptive to the four factors, while six legs(II) type has the poorest adaptability, and the horizontal roof gap is small under large support height, small suspension height, small suspension angle and large tamping angle situation. By means of optimizing structure components and their positional relation and suspension height of backfill scrape conveyor in the process of support design and through controlling working face deployment, roof subsidence in advance, mining height and backfilling during engineering application, the horizontal roof gap is optimized. The research results can be served as theoretical basis for support design and guidance for backfill support to have better performance in backfilling.

VIRTUAL DESIGN OF A NEW TYPE OF HYDRAULIC SUPPORT

Using virtual reality to design a new type of hydraulic support is discussed.That is how to make use of the virtual design to develop coal mining machine in practice. Theadvantages of virtual design are studied and the simple virtual reality system is built. The 3Dparts and elements of hydraulic support are modeled with parametric design in CAD software, thenexported to VR environment, in which the virtual hydraulic support is assembled, operated andtested. With the method, the errors and faults of design can be fined easily, many improvements aremade and the new hydraulic support is developed successfully.

Mechanisms and Kinematics of Hydraulic Support for Top-Coal Caving

The structure and characteristic of new type of hydraulic support for top coal caving were discussed. The mechanism and kinematics of the hydraulic support were analyzed. The formulas were deduced to calculate the velocity and acceleration of top beam, shield beam, front and back legs, which give the solution to the design and research for hydraulic support.

The research of the evaluation system for the sealability of hydraulic supports and jacks＇ seals

In order to enhance the sealing quality and assemble efficiency of hydraulic supports, the evaluation system for the sealability of the hydraulic support and jack＇s seals was established through the testing and experimenting technology in respects, such as seals＇ dimensions, reasonable amounts of compression, sealability, life, resistance to pressure, etc. Through life detecting test of the seal, found the longest life seal ring under the same conditions, and through the reciprocating test of the hydraulic support, found the most appropriate amount of interference between the groove and the seal ring, thus, to decrease the leakage and extend the life span of the hydraulic support.

Stability mechanism and control of the pumpable supports in longwall recovery room

The load-bearing performance(LBP)of pumpable supports(PPS)is crucial for the stability of longwall pre-driven recovery room(PRR)surrounding rock.However,the unbalanced bearing coefficient(UBC)of the PPS(undertaking unequal load along the mining direction)has not been investigated.A mechanical model of the PRR was established,considering the main roof cantilever beam structure,to derive an assessment formula for the load,the failure criteria,and the UBC of the PPS.Subsequently,the generation mechanisms,and influencing factors of the UBC were revealed.Global sensitivity analysis shows that the main roof hanging length(l_(2))and the spacing between the PPS(r)significantly impact the UBC.A novel design of the PPS and the coupling control technology were proposed and applied to reduce the UBC of the PPS in the adjacent longwall PRR.Monitor results showed no failure of the PPS at the test site,with the UBC(ζ)reduced to 1.1 consistent with the design value(1.15)basically,fully utilizing the collaborative LBP of the PPS.Finally,the maximum roof-to-floor convergence of the PRR was 234 mm,effectively controlling the stability of the surrounding rock of the PRR and ensuring the mining equipment recovery.

Longwall Top-Coal Caving in Thinner Thick-Seam and Research on Light Hydraulic Support

The application of light hydraulic support highlights the advantages of longwall top-coal caving (LTC) in thinner thick-seams (3. 0~ 5. 0 m). Considering the problems in practice, the developing of its new series will promote the mining of LTC with light hydraulic supports. Some relevant technical problems of the caving technology and the future of this series of supports are analyzed in this paper with several new opinions.

Computer-Aided Rapid Variant Design System for Hydraulic Support

The paper gives a detail analysis on the necessity of rapid hydraulic support design, and presents a computer-aided rapid variant design system for hydraulic support. The system integrates the type selection and embodiment design of hydraulic support. Case-based reasoning and rule-based reasoning are the main reasoning methods. Several crucial problems are discussed.

A soft-sensing model on hydraulic excavator's backhoe vibratory excavating resistance based on fuzzy support vector machine

In order to measure the backhoe vibratory excavating resistance of a hydraulic excavator fast and precisely,the influences of vibratory excavating depth,angle,vibratory frequency,amplitude,bucket inserting velocity and soil type on the vibratory excavating resistance were analyzed.Simulation analysis was carded out to establish the bucket inserting velocity,amplitude and vibratory frequency considered as secondary variables and excavating resistance as primary variable.A fttzzy membership function was introduced to improve the anti-noise capacity of support vector machine,which is a soft-sensing model on the hydraulic excavator＇s backhoe vibratory excavating resistance based on fuzzy support vector machine.The simulation result reveals that its maximum relative training and testing error are nearly 0.68% and-0.47%,respectively.It is concluded that the model has quite high modeling precision and generalization capacity,and it can measure the vibratory excavating resistance accurately,reliably and fast in an indirect way.

Optimization of Molten Salt Cleaning Process for Surface Roughness of Remanufactured 27SiMn Hydraulic Support Column

During molten salt cleaning of remanufactured 27SiMn hydraulic support column,oxidation occurs on the surface of metal substrate.This results in a change of the surface roughness of metal substrate after cleaning,which affects subsequent remanufacturing process.To decrease the effect is very important.This paper analyzed the oxidation mechanism of molten salt cleaning,explored the oxidation reaction that occurred during cleaning,and determined the key process parameters of cleaning that affecting oxidation reaction.By using central composite experimental design method and taking surface roughness variation of 27SiMn steel samples before and after molten salt cleaning as response variable to optimize the key process parameters,the optimal parameters of molten salt for cleaning remanufactured 27SiMn hydraulic support column could be obtained.The results show that the oxidation reaction of cleaning paint dirt can protect metal substrate from oxidation to a certain extent,and cleaning temperature and placement depth of metal substrate have a direct impact on the degree of oxidation reaction.When the cleaning temperature is 300℃and the distance between paint dirt and free surface of molten salt is 0.5 times the height of the parts,the surface roughness variation is minimal.Therefore,the cleaning quality will be improved under such parameters.

FLUID INDUCED HYDRAULIC SYSTEM VIBRATIONOF POWERED SUPPORT

Fluid and solid interaction analysis of hydraulic support under the coming pressure of roof rocks was presented. The mathematical model of the system was proposed and numerical studies by the character line method were carried out.

STUDY OF A FAULT DIAGNOSIS EXPERT SYSTEM FOR SYNTHETIC MINING SYSTEM HYDRAULIC SUPPORT

Fault diagnosis expert system for hydraulic support is studied.The system is achieved by Turbo prolong Language, it summaries the experience of the domain expert and sets up a fault tree, knowledge base is developed by a productive rule.According to the feature of diagnosis, the system selects forward non determination inferring and limited depth first search strategy.It can accomplish expert diagnosis of more than 50 kinds faults in hydraulic support.

Anchoring mechanism and application of hydraulic expansion bolts used in soft rock roadway floor heave control

Comparing with the resin bolt, the hydraulic expansion bolt has different anchoring mechanism and application advantage. According to the working mechanism of the hydraulic expansion bolt, its anchoring force is expressed in four forms including support anchoring force, tension anchoring force, expansion anchoring force and tangent anchoring force, and their values can be obtained on the basis of each calculation formula. Among them, the expansion anchoring force, which is the unique anchoring force of the hydraulic expansion bolt, can provide confining pressure to increase the strength of rock. Aiming at solving the problem of stability control in the soft rock roadway in Jinbaotun Coal Mine which has a double layer of 40 U-type sheds and cannot provide enough resistance support to control floor heave, the study reveals the mechanism of floor heave in the soft rock roadway, and designs the reasonable support parameters of the hydraulic expansion bolts. The observed results of floor convergence indicate that the hydraulic expansion bolts can prevent the development and flow of the plastic zone in the floor rock to control floor heave. Research results enrich the control technology in the soft rock roadway.

综采液压支架中部跟机多模态人机协同控制系统

我国煤矿智能化综采工作面建设处于初级阶段,液压支架电液控自动化技术已广泛应用,但目前液压支架单一固化的自动化控制逻辑难以适应复杂、多变、动态的工作面生产场景,现场实际控制过程仍大多采用自动化+人工干预方式。针对综采工作面复杂场景中液压支架人机交互协作任务需求,提出液压支架中部跟机多模态人机协同控制系统的理论方法与技术原理。首先,设计了人工式、分工式、批准式、否决式4种人机协同模态,以煤层地质、瓦斯粉尘、采煤机速度、液压支架智能水平、系统状态、岗位工技术水平、任务负荷等为判别因素,构建了基于AOG的液压支架人机协同模态选择模型,实现了人工、机器偏好的模态选择。然后,设计了液压支架中部跟机人机协同控制决策机制,提出液压支架中部跟机再次调控策略AI推理技术思路,利用现场数据学习人工操作经验,分别构建了液压支架是否再次调控决策树分类模型和再次拉架时间贝叶斯回归模型,基于上述模型开发了液压支架人机协同控制决策程序,实现了基于多模态与或推理和再次调控策略AI推理的液压支架人机协同控制。最后,采用云-边-端架构软硬件技术,开发了液压支架多模态人机协同控制系统,实现了模型进化、运算推理、程序执行等液压支架多模态人机协同控制功能。该系统在沙曲二矿3404工作面进行了工业试运行,相比于系统使用前,该工作面液压支架中部跟机效率平均提高2%。

基于数字孪生和深度强化学习的矿井超前液压支架自适应抗冲支护方法

受深部开采冲击地压等地质灾害扰动的影响,存在矿井超前支护系统自感知能力差、智能抗冲自适应能力弱、缺乏决策控制能力等问题。针对上述问题,提出了一种基于数字孪生和深度强化学习的矿井超前液压支架自适应抗冲支护方法。通过多源传感器感知巷道环境和超前液压支架支护状态,在虚拟世界中创建物理实体的数字孪生模型,其中物理模型精确展现超前液压支架的结构特征和细节,控制模型实现超前液压支架的自适应控制,机理模型实现对超前液压支架自适应支护的逻辑描述和机理解释,数据模型存储超前液压支架实体运行数据和孪生数据,仿真模型完成超前液压支架立柱仿真以实现超前液压支架与数字孪生模型虚实交互。根据基于深度Q网络(DQN)的超前液压支架自适应抗冲决策算法,对仿真环境中巷道抗冲支护进行智能决策,并依据决策结果对物理实体和数字孪生模型下达调控指令,实现超前液压支架智能控制。实验结果表明:立柱位移与压力变化一致,说明超前液压支架立柱仿真模型设计合理,从而验证了数字孪生模型的准确性;基于DQN的矿井超前液压支架自适应抗冲决策算法可通过调节液压支架控制器PID参数,自适应调控立柱压力,提升巷道安全等级,实现超前液压支架自适应抗冲支护。

基于加权实例推理的缓倾斜综采工作面液压支架选型研究

为实现地质构造简单的缓倾斜综采工作面液压支架智能化选型,提出了一种基于加权实例推理的液压支架选型方法。首先,建立了液压支架选型实例库;其次,采用粗糙集理论和序关系分析法进行权重构造;另外,将液压支架的条件属性分为3种类型计算相似度;最后通过匹配实例选型。以某煤矿选型方案为例,并以50组液压支架的属性数据进行验证。结果表明,该方法的准确率为88%,能够为液压支架的智能化选型提供较好的参考依据。