Reliability Simulation and Design Optimization for Mechanical Maintenance

Reliability model of a mechanical product system will be newly reconstructed and maintenance cost will increase because failed parts can be replaced with new components during service,which should be accounted for in system design. In this paper,a reliability model and reliability-based design optimization methodology for maintenance are presented. First,based on the time-to-failure density function of the part of the system,the age distributions of all parts of the system during service are investigated,a reliability model of the mechanical system for maintenance is developed. Then,reliability simulations of the systems with Weibull probability density functions are performed,the system minimum reliability and steady reliability for maintenance are defined based on reliability simulation during the life cycle of the system. Thirdly,a maintenance cost model is developed based on replacement rates of the parts,a reliability-based design optimization model for maintenance is presented,in which total life cycle cost is considered as design objective and system reliability as design constrain. Finally,the reliability-based design optimization methodology for maintenance is used to design of a link ring for the chain conveyor,which shows that optimal design with the lowest maintenance cost can be obtained,and minimum reliability and steady reliability of the system can satisfy requirement of system reliability during service of the chain conveyor.

Modelling and Simulation of Scraper Reliability for Maintenance

A scraper conveyor is a kind of heavy machinery which can continuously transport goods and widely used in mines,ports and store enterprises.Since scraper failure rate directly affects production costs and production capacity,the evaluation and the prediction of scraper conveyor reliability are important for these enterprises.In this paper,the reliabilities of different parts are classified and discussed according to their structural characteristics and different failure factors.Based on the component's time-to-failure density function,the reliability model of scraper chain is constructed to track the age distribution of part population and the reliability change of the scraper chain.Based on the stress-strength interference model,considering the decrease of strength due to fatigue failure,the dynamic reliability model of such component as gear,axis is developed to observe the change of the part reliability with the service time of scraper.Finally,system reliability model of the scraper is established for the maintenance to simulate and calculate the scraper reliability.

The main projects and development status of noise forecasting and controlling on working face in coal mine

Noise from the machine on coal working face seriously influenced the miners' physical and mental health, and also, due to the noise, there may be a major hidden danger in safety from accidents as all safety warning signals may be masked by the noise. This paper summarized the features of mine environmental noise on working face, such as the variety of noise sources, the continuity of high intensity and slow attenuation in narrow space, etc.The main projects about noise forecasting and controlling on working face was emphatically expounded;the development status about mines machinery noise mechanism and environmental noise acoustic characteristics of space-time of these main research topics were also introduced.

Effects of Aging Temperature on Microstructure and High Cycle Fatigue Performance of 7075 Aluminum Alloy

The hardness, the tensile and the high-cycle fatigue(HCF) performances of 7075 aluminum alloy were investigated under temper T651, solution treated at 380 ℃ for 0.5 h and aged at different temperatures(150, 170, 190 ℃) for 10 hours. The optimal microstructures and the fatigue fracture surfaces were observed. The results show that the hardness and the tensile performances are at their optimum at T651, but the fatigue life is the shortest. The hardness and the elongation are the lowest after solution treatment. With the aging temperature increasing(150-190 ℃), the HCF is improved. The crack is initiated from the impurity particles on the subsurface. Treated at 170 ℃,the area of the quasi-cleavage plane and the width of parallel serrated sections of the crack propagation are the largest. With increasing aging temperature, the dimple size of finally fracture surfaces becomes larger and the depth deeper.

Life prediction for rolling contact fatigue crack initiation of kiln wheels

这份报纸关于轴行偏转调查火炉车轮的滚动接触疲劳，它与车轮上的应用支持的负担是线性的。为有弹性的临时的便床，塑料临时的便床和 ratcheting 材料回答的疲劳裂缝开始标准被使用与轴的行偏转的二个集合估计车轮回答。有限元素模拟被使用双线性的材料模式为执行非线性、运动学在 ANSYS 11.0 变硬。由从不同 critera 比较结果，低周期的疲劳是支配的失败，这被显示出。从不同的轴的线偏转的结果显示最佳调整罐头极大地提高支持的结构的整个生活。

A Modified Free Volume Model for Characterizing of Rate Effect in Bulk Metallic Glasses

我们调查塑料变丑和体积的组成的行为金属性的眼镜(BMG ) 。尺寸更少德卜拉数字 De (标志)= t (r) /t (i)被建议在 BMG 描绘率效果，在 t (r)是 BMG 在下面的结构的令人放松的典型时间的地方砍负担， t (i)是应用应力的宏观的强加的典型时间或宏观的变丑的典型时间。结果证明修改免费体积模型能有效地在 BMG 描绘紧张率效果。

Numerical Simulation for Shaping Feature of Molten Pool in Twin-Arc Submerged Arc Welding

The notion of ratio of width to length is proposed to describe the shaping feature of molten pool of twin-Arc submerged arc welding accurately, and analyze the law of molten pool variation and weld formation. The temperature field finite element numerical simulation model of twin arc movement is established. The loading form of twin-arc with double ellipsoid heat source is discussed. The molten pool temperature field of twin-arc submerged arc welding is calculated and analyzed under different process parameters. The law of molten pool characteristics influenced by the welding speed, current and voltage of twin-arc submerged arc welding parameters is analyzed. The relation between shaping feature of molten pool and weld formation is discussed according to the ratio of width to length. The results manifested that the width to length ratio of weld pool decreases with the improvement of welding speed, which result in gene- ration of weld defects. The width to length ratio of weld pool is increased by adjusting the proportion of the current, voltage and the distance of the two arcs, which avoids the generation of weld defects.

Weighted Multi-sensor Data Level Fusion Method of Vibration Signal Based on Correlation Function

As the differences of sensor's precision and some random factors are difficult to control,the actual measurement signals are far from the target signals that affect the reliability and precision of rotating machinery fault diagnosis.The traditional signal processing methods,such as classical inference and weighted averaging algorithm usually lack dynamic adaptability that is easy for trends to cause the faults to be misjudged or left out.To enhance the measuring veracity and precision of vibration signal in rotary machine multi-sensor vibration signal fault diagnosis,a novel data level fusion approach is presented on the basis of correlation function analysis to fast determine the weighted value of multi-sensor vibration signals.The approach doesn't require knowing the prior information about sensors,and the weighted value of sensors can be confirmed depending on the correlation measure of real-time data tested in the data level fusion process.It gives greater weighted value to the greater correlation measure of sensor signals,and vice versa.The approach can effectively suppress large errors and even can still fuse data in the case of sensor failures because it takes full advantage of sensor's own-information to determine the weighted value.Moreover,it has good performance of anti-jamming due to the correlation measures between noise and effective signals are usually small.Through the simulation of typical signal collected from multi-sensors,the comparative analysis of dynamic adaptability and fault tolerance between the proposed approach and traditional weighted averaging approach is taken.Finally,the rotor dynamics and integrated fault simulator is taken as an example to verify the feasibility and advantages of the proposed approach,it is shown that the multi-sensor data level fusion based on correlation function weighted approach is better than the traditional weighted average approach with respect to fusion precision and dynamic adaptability.Meantime,the approach is adaptable and easy to use,can be applied to other areas of vibration measurement.

NEW APPROACH FOR RELIABILITY-BASED DESIGN OPTIMIZATION:MINIMUM ERROR POINT

常规基于可靠性的设计优化(RBDO ) 为可靠性限制的概率的分析要求最可能的点(MPP ) 方法到使用。一条新途径被介绍，作为最小的错误点(MEP ) 调用了方法或 MEP 基于方法，基于 forreliability 的设计优化，其想法是最小化错误，由接近的性能函数生产了。MEP 基于方法使用第一顺序泰勒“在 MEP 的 s 扩大而不是 MPP。例子证明 MEP 基于设计优化能在要求的水平保证产品可靠性，它为许多重要工程系统是很必要的。MEPbased 可靠性设计优化方法是可行的并且为解决可靠性设计优化问题被看作一种选择。MEP 基于方法比通常使用的 MPP 为一些不规则的表演功能基于方法是更柔韧的。

Multiaxial fatigue life prediction of kiln roller under axis line deflection

This paper investigates the multiaxial fatigue life of the roller in rolling contact with wheels with respect to axis line deflection. The multiaxial fatigue criteria proposed by Wang and Brown, together with the rainflow counting method and Miner-Palmgren's rule, are applied to the cumulative damage estimation and life prediction. As the axis line deffection of overlong kilns generally results in asymmetric load distribution on each roller, the load ratio is introduced to describe the deffection for quantitative stress analyses. The stress analyses are performed within the finite element code ANSYS. The tangential friction stress is calculated in terms of the condition of the rolling contact area. By taking one roller as an example, the plotted fatigue life versus load ratio curve discovers how the axis line deffection affects the fatigue life. This study is significant to prevent the fatigue failure of the roller and can provide basis to adjust and optimize the axis line of the rotary kiln.

Tribological Properties of MoSi_2 Against AISI10045 Steel Under Sliding Friction

MoSi2 samples were prepared by a self-propagating high-temperature synthesis (SHS) and a hot-press technique. The sliding friction and wear properties of intermetallic MoSi2 against AISI10045 steel under dry friction and oil lubrication conditions were investigated with a MRH-5A type ring-on-block friction and wear tester. The elemental composition, microstructure and worn surface morphology of the MoSi2 material were observed and analyzed by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The synthetic parameter pv value reflecting friction work, was used to discuss the tribological properties of MoSi2 material. The results show that 1) oil lubrication can obviously improve the tribological properties of MoSi2, 2) the bigger the pv value, the greater the antifriction and the abrasive resistance of MoSi2 under oil lubrication, 3) with an increase in the pv value, the wear mechanism of MoSi2 material under dry sliding friction is the fatigue fracture and adhesive wear and 4) under oil lubrication the wear mechanism is mainly fatigue pitting.

An Improved Kernel K-Mean Cluster Method and Its Application in Fault Diagnosis of Roller Bearing

For the kernel K-mean cluster method is run in an implicit feature space, the initial and iterative cluster centers cannot be defined explicitly. Against the deficiency of the initial cluster centers selected in the original space discretionarily in the existing methods, this paper proposes a new method for ensuring the clustering center that virtual clustering centers are defined in the feature space by the original classification as the initial cluster centers and the iteration clustering centers are ensured by the further virtual classification. The improved method is used for fault diagnosis of roller bearing that achieves a good cluster and diagnosis result, which demonstrates the effectiveness of the proposed method.

Critical Free Volume Concentration of Shear Banding Instability in Metallic Glasses

We present a model which predicts the critical free volume concentration of shear banding instability in metallic glasses(MGs).Fl-om the stability map,this model demonstrates that the prediction of shear band thickness is valid only for a short time after shear instability,and the diffusion of defects should be included in the mature shear band in MGs.The results agree well with the experimental observations and simulations.

Fatigue reliability analysis of kiln welded shell

这份报纸在裂缝生长期间为焊接的壳论述一个概率的可靠性方法。与一张失败评价图(一度时髦的风尚) 合并的裂缝生长模型，罐头提供批评裂缝长度的一个更好的评价，被开发描述疲劳失败。为壳的特别焊接关节的所有变量被学习。在他们之中，压力变量由使用有限元素(FE ) 基于计算压力代码 ANSYS。焊接的壳的疲劳可靠性分析被使用蒙特卡罗模拟方法执行。例子火炉的失败概率曲线是显著地有用的决定壳裂缝的修理时间表。

Study on the Cutting Temperature of the Textured Tool by 3D FEA Simulation

Temperature plays an important role in the life of cutting tools.However,it is sometimes difficult to observe instantaneously because of limited data acquisition,especially for the textured tool.In this paper,the performance of microgroove textured cutting tools for three-dimensional(3D)oblique dry turning of AISI 1045 steel was studied by finite element simulation.The effects of width,depth and spacing of strip micro-texture on cutting temperature and the effect of cutting speed on cutting temperature of strip microtexture tool were studied.The results show that the maximum temperature of the tool and the tip temperature first increase and then decrease with the increase of micro-texture width.When the micro-texture depth increases,the maximum temperature and the tool tip temperature decrease first and then increase.The highest temperature and tip temperature of the tool gradually increase with the increase of micro-texture spacing.The highest temperature and tip temperature of the tool increase with the increase of cutting speed,feed speed and cutting depth.In addition,the effective mechanism of micro-texture parameter for the temperature was proposed.It provides profound guidance for optimizing the microstructure parameters and cutting process of cutting tools according to cutting temperature in this study.It also provides an effective and practical method for the design,innovation and development of microtextured tools.

Research on Instantaneous Angular Speed Signal Separation Method for Planetary Gear Fault Diagnosis

Planetary gear train is a critical transmission component in large equipment such as helicopters and wind turbines. Conducting damage perception of planetary gear trains is of great significance for the safe operation of equipment. Existing methods for damage perception of planetary gear trains mainly rely on linear vibration analysis. However, these methods based on linear vibration signal analysis face challenges such as rich vibration sources, complex signal coupling and modulation mechanisms, significant influence of transmission paths, and difficulties in separating damage information. This paper proposes a method for separating instantaneous angular speed (IAS) signals for planetary gear fault diagnosis. Firstly, this method obtains encoder pulse signals through a built-in encoder. Based on this, it calculates the IAS signals using the Hilbert transform, and obtains the time-domain synchronous average signal of the IAS of the planetary gear through time-domain synchronous averaging technology, thus realizing the fault diagnosis of the planetary gear train. Experimental results validate the effectiveness of the calculated IAS signals, demonstrating that the time-domain synchronous averaging technology can highlight impact characteristics, effectively separate and extract fault impacts, greatly reduce the testing cost of experiments, and provide an effective tool for the fault diagnosis of planetary gear trains.

Mapping the elastic properties of two-dimensional MoS_(2) via bimodal atomic force microscopy and finite element simulation

Elasticity is a fundamental mechanical property of two-dimensional(2D)materials,and is critical for their application as well as for strain engineering.However,accurate measurement of the elastic modulus of 2D materials remains a challenge,and the conventional suspension method suffers from a number of drawbacks.In this work,we demonstrate a method to map the in-plane Young’s modulus of mono-and bi-layer MoS_(2) on a substrate with high spatial resolution.Bimodal atomic force microscopy is used to accurately map the effective spring constant between the microscope tip and sample,and a finite element method is developed to quantitatively account for the effect of substrate stiffness on deformation.Using these methods,the in-plane Young’s modulus of monolayer MoS_(2) can be decoupled from the substrate and determined as 265±13 GPa,broadly consistent with previous reports though with substantially smaller uncertainty.It is also found that the elasticity of mono-and bi-layer MoS_(2) cannot be differentiated,which is confirmed by the first principles calculations.This method provides a convenient,robust and accurate means to map the in-plane Young’s modulus of 2D materials on a substrate.

Elastocaloric Effect in PbTiO3 Thin Films with 180°Domain Structure:A Phase Field Study

The elastocaloric effect of Pb TiO_3 thin films with 180°domain structure is studied using the phase field method.The influence of external stress σ_(33),misfit strain u_m and domain wall energy on the adiabatic temperature change(ΔT_σ)at room temperature are carried out.The calculation results indicate that|ΔT_σincreases as|σ_(33)|or|u_m|increases.The largest ΔT_σ value of-7.8 K is obtained atσ_(33)=2 GPa and u_m=-0.02.Furthermore,thedomain switching behaviors under different gradient coefficients are different,and finally affect the elastocaloriceffect in PTO thin films.These results could provide a guide to choose the substrate and the preparation processin experiments.