Optimization of abrasive flow polishing process parameters for static blade ring based on response surface methodology

Static blade ring process technology is a key part for gas turbine manufacturing, and the surface quality of the static blade ring has great influence on a gas turbine. To improve surface roughness of static blade ring, abrasive flow polishing process technology is studied. First, the range of extrusion pressure is obtained by using ANSYS software to analyze the blade deformation. Then a simplified model of surface roughness is estabalished according to experimental results and ANOVA’s results. At the same time, the optimal polishing parameters are confirmed through the response surface methodology. Finally, the polishing experiment is carried out by using the optimal polishing parameters. The experimental results demonstrate that the surface roughness of static blade ring decreased greatly (nearly 14.7%) compared with result using normal parameters.     

Effects of geometric parameters on static load capacity of a double-row four-point contact ball bearing

The geometric parameters, which are difficult to design because of the lack of a corresponding theory and tool, of a double-row four-point contact ball bearing, determine its carrying capacity. In this study, a mechanical model (nonlinear algebraic equations) with the effect of the row spacing, which is different from the current theory for a single-row ball bearing, has been developed. Also, using the corresponding calculation procedure programmed by MATLAB, the effects of the geometric parameters on the load capacity of the bearing have been studied. Some design suggestions have been made for the bearing geometric parameters: to improve the contact strength between the ball and raceway, the row spacing should be designed as small as possible if the bending strength of the mid beam among the rows is enough. To avoid more interference force, the negative clearance should be near zero.     

Effects of working parameters on surface finish in ball-burnishing of hardened steels

Burnishing is a chipless finishing method, which employs a rolling tool, pressed against the workpiece, in order to achieve plastic deformation of the surface layer. Recent developments made possible burnishing of heat-treated steel components up to 65 HRC. Features of burnishing include a good roughness (comparable to grinding), as well as improvement of mechanical characteristics of the surface (fatigue strength, corrosion resistance, and bearing ratio), due to implementation of compressive stresses into the surface layer. This paper will present influences of certain burnishing parameters upon roughness, for a hardened steel component (64 HRC).     

静载荷接触问题中材料力学状态的研究

以两平行圆柱体的接触问题为实例,将“软性系数”的概念引入接触问题,利用软性系数对接触物体的力学状态进行了分析,从理论上证明了工程实际接触问题中塑性变形和塑性破坏的客观存在,从而进一步完善和发展了弹性接触理论。     

Effects of processing parameters on the surface quality of square section die-less spinning

In view of the importance of the surface quality in the application to the square section die-less spinning, the effects of several key parameters which include roller path, half-cone angle, and roller nose radius on the surface quality are investigated. Through the geometric model of residual height, the effect law of the roller path is obtained: the surface quality increases with the decrease of the axial distance of two adjacent slices. Then the finite element model of the square section die-less spinning is established, and the normal force and axial strain states in the deforming process are adopted to predict the relationship between the surface quality and the half-cone angle. Combined with the residual height model and finite element analysis, the roller nose radius’ effect on the surface quality is also obtained. Enlargement of the two parameters can improve the surface quality. All the analysis results are verified by the surface waviness test of the specimens from the workpiece after spinning.     

Effects of process parameters on surface roughness in abrasive waterjet cutting of aluminium

Abrasive waterjet cutting is a novel machining process capable of processing wide range of hard-to-cut materials. Surface roughness of machined parts is one of the major machining characteristics that play an important role in determining the quality of engineering components. This paper shows the influence of process parameters on surface roughness (R_a) which is an important cutting performance measure in abrasive waterjet cutting of aluminium. Taguchi’s design of experiments was carried out in order to collect surface roughness values. Experiments were conducted in varying water pressure, nozzle traverse speed, abrasive mass flow rate and standoff distance for cutting aluminium using abrasive waterjet cutting process. The effects of these parameters on surface roughness have been studied based on the experimental results.     

Monotonic loading of circular surface footings on clay

Appropriate modeling of offshore foundations under monotonic loading is a significant challenge in geotechnical engineering. This paper reports experimental and numerical analyses, specifically investigating the response of circular surface footings during monotonic loading and elastoplastic behavior during reloading. By using the findings presented in this paper, it is possible to extend the model to simulate the vertical-load displacement response of offshore bucket foundations.     

A laminated thin cylindrical shell under axisymmetric static loading

A model is used to discuss the behavior of a laminated shell in which the laminating mechanism is represented by springs which allow both separation and relative layeral motion of “slip” of the faces of the homogeneous isotropic layers. By varying the spring constants it is possible to determine the dependence of both the buckling load and the flexural response upon a wide range of conditions. It is the attempt here to use the most simple model possible which has physical relevance.     

Reduced dependence on loading parameters in almost conforming contacts

In cases of completely conforming frictionless contact, the contact area generally either decreases or stays the same under load, in which case the extent of the contact area is subsequently independent of load and the stress and displacement fields vary linearly with the loading parameter. Dundurs and Stippes describe such cases as receding contact problems. Here, we demonstrate that similar results apply in the presence of Coulomb friction, in which case the extent of the stick and slip zones and the local direction of sliding are independent of load. We also show that if there is a small initial gap or interference throughout the potential contact area, the extent of the contact area and the stress and displacement fields will approach those of the corresponding receding contact problem as the applied load is increased. If the interface conditions permit adhesion between the contacting surfaces, the extent of the adhesion zone shrinks to zero as the load increases without limit. Progress of the contact configuration towards the limit is governed solely by a dimensionless load factor involving the ratio between the applied load and the initial clearance or interference. This permits results for a variety of initial geometries (due to tolerance variations) to be obtained from a set of finite element results for a single case. Some of these characteristics are demonstrated using a finite element solution of a connecting rod/bushing/gudgeon pin contact. Other interesting applications are those with complex geometries, ranging from biomechanics, as in prostheses, to the design of multiple fasteners.     

固定结合面法向静态特性模型研究

分析了以往学者们对载荷-变形规律所作的处理,提出了一种新的拟合模型。设计了结合面静态特性实验台,通过实验,研究了结合面法向刚度随载荷的变化规律。应用指数曲线对变形-载荷曲线进行了拟合,分析了拟合误差,并结合理论和实验结果,对拟合函数进行了改进,提出了新的拟合模型,减小了拟合误差,能够为工程应用提供较高精度的数据。     

汽车车身静态拓扑参数综合优化设计

在单元灵敏度分析的基础上,提出汽车车身框架结构的静态拓扑参数综合优化方法.在优化过程中,先将单元灵敏度计算公式通过截面特性加权变成拓扑参数再修改灵敏度的分析方法,并提出避免"载荷病态"的灵敏度复合方法来处理多裁荷工况.其次根据设计要求对杆件进行分组,并将可选的梁截面根据属性大小进行编号.最后根据综合灵敏度的大小修改对应组的梁截面特性编号.将所提的方法应用于汽车车身轻量化设计中,得到有效的优化结构.     

Deformation of surface irregularities under static loads

The effect of surface topography on the contact behaviour of surfaces under static loads was studied using turned cylindrical specimens loaded under a hard flat surface. The surface profile was recorded after each loading. The contact behaviour was analysed statistically from surface profiles obtained at various stages of deformation. Three statistical parameters, the height distribution function, the autocorrelation function and the power spectral density function, were used. It was observed that asperities deform plastically even under small loads and persist even under high loads. Most of the load was supported by longer wavelength structures.     

Effects of tool overhang on selection of machining parameters and surface finish during diamond turning

In precision machining leading to nano-metric surface finish, selection of the suitable machining parameters is a critical task. To ensure the desired surface quality, one needs to optimally select the machining parametric matrix. Towards this effort, this paper adds another critical parameter in terms of tool overhang. A well-defined set of machining exercises is carried out with different tool overhangs and machining parameters. In this investigation, an attempt has been made to locate the optimum range of tool overhang with minimum tool vibrations. The interaction between tool overhang with other parameters is also thoroughly investigated. Another important focus of this study is to find out the optimum machining parameters for the situations where it is not possible to select an optimum tool overhang. One such situation occurs when a steep concave parabolic surface needs to be fabricated. In this case a large tool overhang has to be selected. Power spectral density distribution analysis of surface roughness for different tool overhangs is performed to find out significant parameters and their degree of contribution to surface roughness. Analysis of variance is also applied to ascertain statistically significant factors contributing to surface roughness. To model the surface roughness, response surface methodology is being used. The model has been verified by conducting a series of experiments and a steep concave parabolic surface is developed by following the predictions of the developed model.     

Effects of ball burnishing parameters on surface finish—A literature survey and discussion

Ball burnishing, a plastic deformation process, is becoming more popular as a finishing operation. A literature survey and discussion on the effects of the various types of burnishing (normal, vibratory and ultrasonic) and related parameters—force, speed, feed-rate, lubrication, ball material and diameter, workpiece material, pre-machined roughness and frequency of oscillation—on the final surface roughness are presented. The effect is an interaction between the process parameters with burnishing force and feed-rate as the two most significant factors. A particular surface finish can be obtained by appropriate selection of the parameters     

Experimental studies on mechanical behavior of carbon fiber laminates under static and cyclic loading

An experimental investigation of the mechanical behavior of carbon fiber-reinforced plastic laminates under quasistatic and cyclic loading is performed. A uniform nonlinear elastic deformation of carbon fiber reinforced plastic laminates with uniform increment of the tangent modulus is studied. A condition for the initiation of the microscopic damage process was identified. The analysis of discreet continuous stages of the damage process followed by energy release was conducted. A diagram of deformation up to full loss of carrying capacity of the material is plotted. The proposed approach can be useful for diagnostics of elements of composite structures in operation.     

Detection and measurement of damage to surfaces after static contact loading

A system for three-dimensional measurements of surfaces has been developed and used to determine contact areas and spot distributions (following incremental loadings) of ground aluminium surfaces contacting a smooth platten.     

静磁场对固液界面表面电荷性质的影响

考虑磁场对固液界面表面电荷性质的影响与微纳流体系统的流体阻力相关,本文采用原子力显微镜(AFM)研究了静磁场对去离子水黏度以及高硼硅玻璃-去离子水界面表面电荷性质的影响,并分析了静磁场对去离子水性质影响的机理。研究结果表明,将去离子水静置于磁场强度为0~0.6T的静磁场下30min时,去离子水的黏度随磁场强度的增加而减小,而高硼硅玻璃-磁化水界面的表面电荷密度随磁场强度的增加而增加;静磁场对去离子水性质影响的机理是磁场引起的去离子水内氢键以及氢氧键的断裂。研究结果同时表明,磁场可以有效地改变固液界面的表面电荷性质。本文的研究结果为利用磁场有效地控制微纳流体系统的流体阻力提供了可能。     

Strength calculations for reinforced plastic pipes under static and low-cycle loading

Methods for selecting the strength phenomenological approach and for calculating of rein- forced plastic pipes strength under static and low-cycle loading are represented. The results of experimental studies are given. The curvature effect on fiberglass curved pipes’ strength is shown.     

Stochastic analysis of compositionally graded plates with system randomness under static loading

This paper presents an investigation of the stochastic bending response of moderately thick, compositionally graded plates with uncertainties of low variability and subjected to lateral load and uniform temperature change. System parameters such as the thermal and mechanical material properties of each constituent material, volume fraction index, and load intensity are taken as independent random variables. The basic formulations are based on Reddy's higher-order shear deformation plate theory and a semi-analytical method. A first-order perturbation technique is employed to obtain the second-order response statistics-mean and variance of the flexural deflection of plates with various boundary conditions. Typical results are presented for two types of plates containing functionally graded materials made of metallic phase Ni and ceramic phase Al₂O₃. It is found that the response sensitivity of the plate is very much dependent on the material composition. Variations in Young's modulus and lateral load have dominant effects on the stochastic characteristics compared to other random parameters. The deflection dispersion of compositionally graded plates shows the so-called “non-intermediate” characteristic even when thermal loading is absent.     

滚动接触载荷作用下的铁轨表面裂纹开合状态分析

通过计算不同接触载荷以及轮轨表面摩擦系数条件下裂纹面的接触面积和接触应力,对裂纹面的开合状态进行分析,并且对相应状态下液体渗入裂纹的可能性做出判断,由此总结了滚动接触载荷作用下,液体环境存在对铁轨表面疲劳裂纹扩展机理的影响.