360㎡烧结机台车起拱问题与解决方案的应用研究

烧结机是冶金行业生产高炉炉料烧结矿的设备,广泛应用于冶金炼铁的烧结工序上,其运行原理是通过电机驱动涡轮装置使机头主星轮旋转起来,星轮轮齿卡住台车体实现向前推动装有混合料的台车体向机尾尾星轮方向匀速移动;台车起拱现象一般出现在烧结机机头主星轮上的吐齿处和机尾星轮的下平面吐齿处,起拱的位置会形成挤压和磨损,对台车体端部会造成较大磨损,当挤压力减小时,台车体受重力作用会落到轨道上,造成摔台车现象,对轨道也会形成冲击,导致台车入主星轮时不正、很容易出现上层台车跑偏、尾星轮顶台车体等问题;另外,上行台车起拱现象还会造成烧结机漏风率上升,影响烧结矿质量和产量的正常生产。

烧结机台车起拱现象的分析及处理

对烧结机起拱现象进行了分析。认为烧结机机尾星轮齿板对台车卡轮推动前进过程中产生过大的向上摩擦分力是造成台车在回车道上起拱的根本原因。永通公司通过采取减小星轮齿板对台车卡轮向上摩擦分力等措施,基本消除了回车道上台车起拱现象,降低了烧结机漏风率,延长了台车使用寿命,效果显著。

分析起拱现象在烧结机台车出现的原因及处理办法

通过对烧结机出现起拱现象详细的情况分析,笔者认为此类现象产生的原因在于内部部件的向上摩擦分力过大,而这个摩擦分力则是由位于烧结机尾部的星轮齿板造成的。由于台车的卡轮同星轮齿板相互作用而受到反向摩擦力作用,出现了起拱。所以,笔者认为对于起拱现象处理的最合理措施就是减小这个作用在台车卡轮上的摩擦分力,从而消除回车道上出现的台车起拱。起拱现象的消除对于台车使用效率的提高以及使用寿命的延长都十分有利。

Comparative study of different theories on active earth pressure

Determination of distribution and magnitude of active earth pressure is crucial in retaining wall designs. A number of analytical theories on active earth pressure were presented. Yet, there are limited studies on comparison between the theories. In this work, comparison between the theories with finite element analysis is done using the PLAXIS software. The comparative results show that in terms of distribution and magnitude of active earth pressure, RANKINE＇s theory possesses the highest match to the PLAXIS analysis. Parametric studies were also done to study the responses of active earth pressure distribution to varying parameters Increasing soil friction angle and wall friction causes decrease in active earth pressure. In contrast, active earth pressure increases with increasing soil unit weight and height of wall. RANK/NE＇s theory has the highest compatibility to finite element analysis among all theories, and utilization of this theory leads to proficient retaining wall design.

Effects of Roughness Elements Distribution on Overland Flow Resistance

Roughness elements are various in a mountain area; they include gravel and ground surface vegetation that often result in surface friction drag to resist overland flows. The variation and characteristics of flow resistance strongly impact the overland flow process and watershed floods. In view of the universal existence of natural vegetation, such as Chlorophytum malayense(CM) or Ophiopogon bodinieri(OB), and the sand-gravel bed of the river channel, it is important to understand the role of different types of roughness elements in flow resistance. This study was performed to investigate and compare through flume experiments the behaviors of overland flow resistance by the reaction of multi-scale configuration of different roughness elements. The result showed that the resistance coefficient gradually reduced versus the increase of flow rate in unit width and tended to be a constant when q = 3.0 l/s.m, Fr = 1.0, and Re = 4000 for slopes of 6 to 10 degrees. The gap of the vegetated rough bed and the gravel rough bed is limited to the same as the gap of the two types of vegetation, CM and OB. It was noted that the vegetation contributed to the increase in form resistance negatively and may lead to the mean resistance on decrease. To classify the flow pattern, the laminar flows were described by DarcyWeisbach's equation. In the study the f-Re equation of vegetated bed was developed with f ?5000 Re.The friction coefficient for laminar flows can be regarded as the critical value for identifying the transformation point of the flow pattern.

Finite element analysis of rolling process for variable cross-section blade

Due to the variation of the blade cross-section, the deformation stress and strain of the workpiece keep changing during the rolling process and the conventional rolling theory is no longer valid. The complexity and diversity of the blade cross-section determine it impossible to establish an universal theoretical model for the rolling process. Finite element analysis(FEA) provides a perspective solution to the prediction. The FEA software DEFORM was applied to discovering the deformation, stress, strain and velocity field of the variable cross-section workpiece, and the effects of friction coefficient and rolling speed during the rolling process. which indicates that the average rolling force at friction coefficient of 0.4 is 6.5% higher than that at 0.12, and the rolling velocity has less effect on the equivalent stress and strain distribution, which would confer instructive significance on the theoretical study as well as the engineering practice.

Parametric optimization and microstructural characterization of friction welded aeronautic aluminum alloy 2024

Continuous drive friction welding was employed to join the aeronautic aluminum alloy 2024.Parametric optimization and microstructural characterization were investigated.Results show that friction pressure is the most significant factor influencing the tensile strength of joints.To obtain a high joint efficiency,the combination of moderate friction pressure,less friction time and higher upset pressure is recommended.The optimized joint efficiency from Taguchi analysis reaches 92% of base metal.Under the optimized experimental condition,the interfacial peak temperature is calculated analytically in the range of 779-794 K,which is validated by experimental data.Fine recrystallized grains caused by the high temperature and plastic deformation are observed in the friction interface zone.The grain refinement is limited in the thermo-mechanically affected zone,where most of matrix grains are deformed severely.The extensive dissolution and limited re-precipitation of strengthening phases result in a lower microhardness in the friction interface zone than that in the thermo-mechanically affected zone.

Productivity prediction model and optimal configuration of herringbone multilateral well

In order to accurately predict the productivity of herringbone multilateral well,a new productivity prediction model was founded.And based on this model,orthogonal test and multiple factor variance analysis were applied to study optimization design of herringbone multilateral well.According to the characteristics of herringbone multilateral well,by using pressure superposition and mirror image reflection theory,the coupled model of herringbone multilateral well was developed on the basis of a three-dimensional pseudo-pressure distribution model for horizontal wells.The model was formulated in consideration of friction loss,acceleration loss of the wellbore and mixed loss at the confluence of main wellbore and branched one.After mathematical simulation on productivity of the herringbone multilateral well with the coupled model,the effects of well configuration on productivity were analyzed.The results show that lateral number is the most important factor,length of main wellbore and length of branched wellbore are the secondary ones,angle between main and branched one has the least influence.

Theoretical analysis of thermoviscoelastic contact between friction lining and wire rope in mine friction hoists

Serious accidents of mine hoists caused by high-speed sliding between friction lining and wire rope are often seen in coal mines.In order to solve this problem,we analyzed the contact characteristics between friction lining and wire rope.Then we carried out a dynamic mechanical analysis(DMA) to explain the change in mechanical properties of the friction lining as function of temperature and load frequency and found that temperature has a stronger effect on the mechanical properties than the frequency.We used multiple regression analysis to obtain the thermoviscoelastic constitutive relations of the friction lining.As well we derived the analytic solution for the thermoviscoelastic contact radius and pressure by combining the theory of viscoelastic contact mechanics with thermoviscoelastic constitutive relations.

Granular dynamic shear strength and its influencing factors

The granular dynamic shear strength is the same as that of the static one in nature, as found from numerous experiments and investigations. The shear strength is equal to the sum of the internal frictional force and the cohesive force. The influences of type, shape, size distribution, pore ratio, moisture content and variation of vibration velocity on the dynamic shear strength of granules were studied. Based on numerous vibration shear experiments, the authors investigate the mechanism of dynamic shear strength in granules in terms of the fundamental principle and the relevant theory of modern tribology.

FEASIBILITY AND EXPERIMENT ANALYSIS OF FOUR-ROPES FRICTION HOIST WITHOUT ROPE GROOVES CUTTING

Based on theoretical analysis and experiment, when the difference between the ropes length is ensured, the radius difference between the rope grooves and the difference of the rope strain of a double rope friction hoist will decrease with the increasing of hoisting times. Then the rope grooves cutting are not needed. If the connection form of the ropes or the structure of the frictional wheel of a four ropes friction hoist are changed into as a double ropes hoists, the hoist rope grooves will not need to be cut as well, and the working time will be saved and the service life of the rope lining will be lengthened also.

Single asperity friction in the wear regime

We used molecular dynamics simulation to investigate the friction of a single asperity against a rigid substrate, while generating debris. In the low wear regime(i.e., non-linear wear rate dependence on the contact stress, via atom-by-atom attrition), the frictional stress is linearly dependent on the normal stress, without any lubrication effect from the wear debris particles. Both the slope(friction coefficient) and friction at zero normal stress depend strongly on asperity-substrate adhesion. In the high wear regime(i.e., linear wear rate dependence on the contact stress, via plastic flow), the friction-normal stress curves deviate from a linear relation merging toward plastic flow of the single asperity which is independent of the interfacial adhesion. One can further link wear and friction by considering debris generation as chemical reaction, driven by both normal and frictional forces. The coupling between wear and friction can then be quantified by a thermodynamic efficiency of the debris generation. While the efficiency is less than 5% in the low wear regime, indicating poor mechanochemical coupling, it increases with normal stress toward 50% in the high wear regime.

Wear analysis of revolute joints with clearance in multibody systems

In this work, the prediction of wear for revolute joint with clearance in multibody systems is investigated using a computational methodology. The contact model in clearance joint is established using a new hybrid nonlinear contact force model and the friction effect is considered by using a modified Coulomb friction model. The dynamics model of multibody system with clearance is established using dynamic segmentation modeling method and the computational process for wear analysis of clearance joint in multibody systems is presented. The main computational process for wear analysis of clearance joint includes two steps, which are dynamics analysis and wear analysis. The dynamics simulation of multibody system with revolute clearance joint is carried out and the contact forces are drawn and used to calculate the wear amount of revolute clearance joint based on the Archard's wear model. Finally, a four-bar multibody mechanical system with revolute clearance joint is used as numerical example application to perform the simulation and show the dynamics responses and wear characteristics of multibody systems with revolute clearance joint. The main results of this work indicate that the contact between the joint elements is wider and more frequent in some specific regions and the wear phenomenon is not regular around the joint surface, which causes the clearance size increase non-regularly after clearance joint wear. This work presents an effective method to predict wear of revolute joint with clearance in multibody systems.