Geometric parameters effect of the atomic force microscopy smart piezoelectric cantilever on the different rough surface topography quality by considering the capillary force

Nowadays, the atomic force microscopy (AFM) is widely used in the nanotechnology as a powerful nano‐robot. The surface topography in Nanoscale is by far one of the most important usages of the AFM device. Hence, in this article, the vibration motion of a piezoelectric rectangular cross‐section micro‐cantilever (MC) which oscillates in the moist environment has been examined based on the Timoshenko beam theory. After extracting the MC governing equations according to Hamilton's principle, the finite element method has been used to discretize the motion equations. The surface topography has been simulated for various roughness forms in the tapping and non‐contact modes by considering the effects of the Van der Waals, capillary and contact forces. Also, the experimental results obtained from the glass surface topography have been simulated. The results illustrate that the time delay in higher natural frequencies in the tapping mode is shorter in comparison with the non‐contact mode, especially, for the lower natural frequencies. The sensitivity analysis of the natural frequencies, topography depth and time delay have been simulated. Results indicate that the most effective parameter is the MC length. In the first mode, the first section length has the highest effect on the surface topography time delay, also, in the second vibration mode; the most effective parameter on the time delay is the MC tip length based on the simulation results.     

Dynamic modeling of oblique non-uniform piezoelectric MC in liquid with various percentages of glycerin in the presence of rough surface

One of the most useful applications of an AFM is imaging of biological particles in a liquid medium. The increase of the topography accuracy in a liquid medium requires accurate dynamic modeling of a Microcantilever (MC). This article investigates the accurate dynamic modeling of the non-uniform AFM piezoelectric MC with rectangular geometry in the amplitude mode in liquid medium for rough surfaces. To increase the accuracy of the modeling, the Modified couple stress (MCS) theory in the liquid medium according to the Timoshenko beam model has been used. Moreover, the differential quadrature (DQ) method has been used for solving equations, because in comparison with the other methods it has a high speed in solving equations and is accurate in the number of fewer elements. In addition, the accurate force modeling has been established by considering the shear forces caused by liquid on the sides of the piezoelectric MC by solving the Navier-Stokes equations, and by considering the hydrodynamic force, squeeze force and applied forces between the sample surface and the MC tip. The results illustrate that utilizing higher vibration modes affect the quality of rough surface topography with the step roughness in the liquid medium and increase the quality of surfaces topography in the tapping mode, especially in the second MC vibration mode. Moreover, it should be noted that the sensitivity of the MC vibration amplitude to the piezoelectric MC angle is higher in comparison with other investigated parameters.     

Analysis of the atomic force microscopy vibration behavior using the Timoshenko theory by multi‐scale method in the air environment

This article deals with the modeling and simulation of the vibration behavior of piezoelectric micro‐cantilever (MC) based on the Timoshenko theory and using multi‐scale (MTS) method in the air environment. In this regard, the results are compared with the previous literature, such as the finite element method and the MTS method. The analysis of the piezoelectric MC vibrating behavior is investigated in a dynamical mode including non‐contact and tapping modes. The dynamics of this system is affected by interferential forces between probe tip and sample surface, such as van der Waals, capillary, and contact forces. According to the results, the forces applied to the probe tip reduce the amplitude and the resonance frequency. The simulation of surface topography in non‐contact mode and tapping for rectangular and wedge‐shaped roughness in the air environment are presented. Various experiments have been conducted in Ara research Company using the atomic force microscopy device in the amplitude mode. In the NSC15 Cantilever, the first natural frequency is derived from the results of the MC simulation based on Timoshenko beam theory, the practical results are 295.85 and 296.12 kHz, and the error rate is 0.09; at higher natural frequencies, the error rate has been increased. The γ _f coefficient is a measure of the nonlinear effects on the system; the effect of the piezoelectric length and width on γ _f coefficient is also investigated.     

FEM analysis of the vibrational motion of oblique piezoelectric microcantilever in the vicinity of a sample surface in liquid

This article examines an oblique Microcantilever (MC) with an extended piezoelectric layer in liquid. The study of hydrodynamic force in MC which has been floated in viscous fluid is considered as paramount importance. To model the Vibrational motion, the Hamilton's principle has been used. For this purpose, the Vibrational motion equation has been modeled by considering the continuous beam based on the Euler–Bernoulli beam theory in liquid. Furthermore, using the Galerkin method and the Newmark algorithm, the differential equations of the MC has been solved. In this modeling, the inter-atomic forces between the MC tip and the sample surface have been considered in addition to the hydrodynamic and squeeze forces. The simulation results illustrate a reduction in the sensitivity of the vibrational motion under the effect of the squeeze force during the angularization of the MC. Moreover, the results illustrate that by reducing the MC distance from the sample surface, the Vibration amplitude decreases due to the increase in the fluid squeeze force. At the end, it has been shown that the time delay in sample surface topography in liquid substantially decreases in comparison with the air.     

轴向超声辅助端面磨削金属表面形貌及粗糙度预测

轴向超声辅助端面磨削被广泛应用于难加工材料加工,而磨削后的表面粗糙度对构件摩擦、疲劳等服役性能有重要影响。超声振幅的大小对轴向超声辅助端面磨削金属表面形貌和粗糙度有较大影响,但是现有模型中并未考虑实际加载对振幅的影响,因此提出了一种考虑加载状态下振幅变化的轴向超声辅助端面磨削金属表面形貌及粗糙度预测方法。根据砂轮粒度及尺寸建立了考虑磨粒随机分布的砂轮端面模型,并对轴向超声辅助端面磨削磨粒的三维磨削轨迹进行了数学描述,生成了加工后的表面三维数据矩阵并对表面粗糙数值进行了计算。在此基础上,研究了粗糙度随振幅的变化规律,提出了振幅衰减形貌映射系数这一概念,并给出了其标定方法。通过振幅衰减形貌映射系数近似计算出加载状态下的振幅并代入到所建立的轴向超声辅助端面磨削表面形貌及粗糙度预测模型中,实现了金属表面形貌模拟及粗糙度预测。最后,通过试验对所建模型的正确性进行了验证。     

Modelling of the In uence of Tool Runout on Surface Generation in Micro Milling

Micro milling is a flexible and economical method to fabricate micro components with three-dimensional geometry features over a wide range of engineering materials. But the surface roughness and micro topography always limit the performance of the machined micro components. This paper presents a surface generation simulation in micro end milling considering both axial and radial tool runout. Firstly, a surface generation model is established based on the geometry of micro milling cutter. Secondly, the influence of the runout in axial and radial directions on the surface generation are investigated and the surface roughness prediction is realized. It is found that the axial runout has a significant influence on the surface topography generation. Furthermore, the influence of axial runout on the surface micro topography was studied quantitatively, and a critical axial runout is given for variable feed per tooth to generate specific surface topography. Finally, the proposed model is validated by means of experiments and a good correlation is obtained. The proposed surface generation model o ers a basis for designing and optimizing surface parameters of functional machined surfaces.     

Dual frequency atomic force microscopy on charged surfaces

The cantilever is mechanically driven at two resonant frequencies in a bimodal atomic force microscope (AFM). To generate the feedback signal for topography measurement the deflection signal is demodulated at one frequency and for compositional surface mapping at the other. In particular, the second mode amplitude and phase signals are used to map surface forces such as the van der Waals interaction. On electrically charged surfaces both, van der Waals forces and electrostatic forces contribute to the second eigenmode signal. The higher eigenmode signal in bimodal AFM reflects the local distribution of electrical charges. Mechanically driven bimodal AFM thus also provides a valuable tool for compositional mapping based on surface charges.     

A dynamic surface topography model for the prediction of nano-surface generation in ultra-precision machining

Materials induced vibration has its origin in the variation of micro-cutting forces caused by the changing crystallographic orientation of the material being cut. It is a kind of self-excited vibration which is inherent in a cutting system for crystalline materials. The captioned vibration results in a local variation of surface roughness of a diamond turned surface. In this paper, a dynamic surface topography model is proposed to predict the materials induced vibration and its effect on the surface generation in ultra-precision machining. The model takes into account the effect of machining parameters, the tool geometry, the relative tool–work motion as well as the crystallographic orientation of the materials being cut. A series of cutting experiments was performed to verify the performance of the model and good correlation has been found between the experimental and simulation results.     

基于声发射技术的微切削加工表面形貌监测

采用声发射技术对工件材料为A16061-T6的微切削表面轮廓进行了实时测量.采集监控微切削加工表面时产生的声发射均方根信号,并与表面轮廓仪测得的结果进行对比.研究表明,声发射均方根信号与微切削表面形貌很好的相对应,因此,声发射技术适于微切削表面形貌的监测.研究了切削用量(每齿进给量和主轴转速)与表面形貌之间的关系,微切削的每齿进给量对表面粗糙度影响较大.     

Built-up edge effects on process outputs of titanium alloy micro milling

Built-up edge (BUE) is generally known to cause surface finish problems in the micro milling process. The loose particles from the BUE may be deposited on the machined surface, causing surface roughness to increase. On the other hand, a stable BUE formation may protect the tool from rapid tool wear, which hinders the productivity of the micro milling process. Despite its common presence in practice, the influence of BUE on the process outputs of micro milling has not been studied in detail. This paper investigates the relationship between BUE formation and process outputs in micro milling of titanium alloy Ti6Al4V using an experimental approach. Micro end mills used in this study are fabricated to have a single straight edge using wire electrical discharge machining. An initial experimental effort was conducted to study the relationship between micro cutting tool geometry, surface roughness, and micro milling process forces and hence conditions to form stable BUE on the tool tip have been identified. The influence of micro milling process conditions on BUE size, and their combined effect on forces, surface roughness, and burr formation is investigated. Long-term micro milling experiment was performed to observe the protective effect of BUE on tool life. The results show that tailored micro cutting tools having stable BUE can be designed to machine titanium alloys with long tool life with acceptable surface quality.     

Modeling and simulation of grinding surface topography considering wheel vibration

Grinding is an important means of realizing precision and ultra-precision machining. Vibration caused by an unbalanced grinding wheel in grinding process has a significant impact on the quality of workpiece surface. However, the effect of wheel surface topography and/or the relative vibration between grinding wheel and workpiece are not considered in most researches. Taking the relative vibration between grinding wheel and workpiece into account, alongside the abrasive grain trajectory equation, a new analysis and simulation model for surface topography of the grinding process is established. The model for the topography of the grinding wheel surface is first studied, and subsequently, a new simulation model for surface topography of the grinding process is proposed. Case studies are performed at the end, and the influence of grinding wheel vibration amplitude, wheel grit number, as well as grinding parameters on the surface waviness and roughness is discussed. The simulation results could be used to optimize the actual grinding process to improve the ground surface quality or predict the surface topography by given grinding parameters.     

Sensitivity of surface roughness parameters to changes in the density of scanning points in multi-scale AFM studies. Application to a biomaterial surface

In the field of biomaterials surfaces, the ability of the atomic force microscope (AFM) to access the surface structure at unprecedented spatial (vertical and lateral) resolution, is helping in a better understanding on how topography affects the overall interaction of biological cells with the material surface. Since cells in a wide range of sizes are in contact with the biomaterial surface, a quantification of the surface structure in such a wide range of dimensional scales is needed. With the advent of the AFM, this can be routinely done in the lab. In this work, we show that even when it is clear that such a scale-dependent study is needed, AFM maps of the biomaterial surface taken at different scanning lengths are not completely consistent when they are taken at the same scanning resolution, as it is usually done: AFM images of different scanning areas have different point-to-point physical distances. We show that this effect influences the quantification of the average (R(a)) and rms (R(q)) roughness parameters determined at different length scales. This is the first time this inconsistency is reported and should be taken into account when roughness is measured in this way. Since differences will be in general in the range of nanometres, this is especially interesting for those processes involving the interaction of the biomaterial surface with small biocolloids as bacteria, while this effect should not represent any problems for larger animal cells.     

The characteristics of cutting forces in the micro-milling of AISI D2 steel

The interaction effect of parameters to surface topography and cutting forces is investigated, and the magnitudes of these parameters are determined in the micro-milling of AISI D2 steel. The results show that the feed per tooth has a prominent impact on the surface topography. Due to the low feed per tooth to cutting edge radius ratio, a high surface roughness and a high amount of burrs are obtained in micro-milling. In micro cutting, the cutting forces present are small; in addition, the radial thrust cutting forces are greater than the principal cutting forces. This research proves that the micro-milling process can be applied to the manufacturing of AISI D2 steel micro parts and presents experimental evidence and possible solutions to the cutting parameters.     

猪笼草蜡质滑移区表面反粘附特性的研究

利用环境扫描电子显微镜(ESEM)和原子力显微镜(AFM)表征红瓶猪笼草蜡质滑移区表面微观形貌,并提取粗糙度的相关参数。利用AFM分别在低载荷和高载荷下对蜡质区表面同一区域进行扫描,在不同条件下的扫描形貌一致,且扫描后的探针针尖上未发现附着污染物。利用胶体探针技术在无针尖的探针悬臂上粘附15 μm SiO2小球,模拟单根刚毛与猪笼草蜡质区表面的接触,并测试蜡质区表面的粘附力和摩擦力,并与不同粗糙度的抛光纸表面做对照。考虑到表面物理化学性质对其粘附特性的重要影响,利用接触角测量仪测量蜡质区表面和同粗糙度范围抛光纸表面对水和二碘甲烷的表观接触角并利用二滴法计算其表面能。研究结果表明：蜡质滑移区表面单个蜡质晶体具有力学稳定性,不会因脱落而污染昆虫的粘附器官,污染学说不成立;表面微粗糙度能有效地减小界面间的接触面积,降低了蜡质滑移区表面的粘附力和摩擦力;蜡质滑移区超疏水特性和低表面能是降低表面粘附力和摩擦力的另一个重要因素,两者共同作用形成了猪笼草蜡质滑移区的反粘附特性。     

Mold surface roughness effects on cavity filling of polymer melt in micro injection molding

Micro injection molding presents many challenges in the injection-molding community. When the dimensions of the part (and thus the cavity of the mold) are small, micro-scale factors such as mold surface roughness may play an important role in the filling of polymer melt. This paper investigates the effects of mold surface roughness on cavity filling of polymer melt in micro injection molding. A disk insert, which has two halves with different surface roughness but with the same roughness mean lines, was used in the investigations. The ratio of flow area of the rougher half with the total flow area of the molded part is used to evaluate the significance of surface roughness effect. The experimental results revealed that mold surface roughness does resist the cavity filling of polymer melt in micro injection molding. For the limited range of injection rate investigated, it is not significant on the surface roughness effects. The increase of mold temperature will decrease surface roughness effects. The change of melt temperature within the range allowed by the process is insignificant for surface roughness effects.     

Demonstration of topography modification by friction processes and vice versa

Contact formation and development are the basis of friction and wear modelling and understanding. Unanimously topography formation and development in friction contacts are regarded of highest importance for understanding and modelling friction processes. The frequently found running in behaviour of sliding contacts is—aside from the build up of reaction and transfer layers-at least partly caused by the topography development due to friction processes until a stable equilibrium state is reached.Experimental results of friction and topography measurements are presented which demonstrate the mutual modification of friction and contact topography.A special experimental set up with an AFM allowed to correlate the measured friction forces with the contact position and the topography at this point. In this way, friction force transitions and changes can be assigned to topography changes due to abrasion, adhesion and wear particle agglomeration.Contact surfaces with artificial regular structures have been prepared to avoid problems with topography and friction correlation due to the statistical nature of roughness on technical contact surfaces. The friction effects of roughness were simulated by etched ditches of defined width, depth and distance on silicon or metal surfaces. This allowed to explain the mutual influences of topography and friction. The effect of a single ‘asperity’ and of the ‘roughness structures’ could be demonstrated.Topography measurements with an AFM correlated with the friction force could help to understand friction changes without changing any parameter.     

Surface generation modeling of micro milling process with stochastic tool wear

Micro milling is widely used to manufacture miniature parts and features at high quality with low set-up cost. To achieve a higher quality of existing micro products and improve the milling performance, a reliable analytical model of surface generation is the prerequisite as it offers the foundation for surface topography and surface roughness optimization. In the micro milling process, the stochastic tool wear is inevitable, but the deep influence of tool wear hasn't been considered in the micro milling process operation and modeling. Therefore, an improved analytical surface generation model with stochastic tool wear is presented for the micro milling process. A probabilistic approach based on the particle filter algorithm is used to predict the stochastic tool wear progression, linking online measurement data of cutting forces and tool vibrations with the state of tool wear. Meanwhile, the influence of tool run-out is also considered since the uncut chip thickness can be comparable to feed per tooth compared with that in conventional milling. Based on the process kinematics, tool run-out and stochastic tool wear, the cutting edge trajectory for micro milling can be determined by a theoretical and empirical coupled method. At last, the analytical surface generation model is employed to predict the surface topography and surface roughness, along with the concept of the minimum chip thickness and elastic recovery. The micro milling experiment results validate the effectiveness of the presented analytical surface generation model under different machining conditions. The model can be a significant supplement for predicting machined surface prior to the costly micro milling operations, and provide a basis for machining parameters optimization.     

Model-based identification of tool runout in end milling and estimation of surface roughness from measured cutting forces

This paper presents a model-based approach for the identification of tool runout and the estimation of surface roughness from measured cutting forces. In the first part of the paper, the effect of tool runout on variations in the cutting forces and the effect on surface roughness generation are studied. Thereby, several influencing parameters are identified and examined systematically. Based on theoretical considerations, systematic relationships between tool runout, resultant process force variations, and surface roughness characteristics are deduced. The sensitivity of process force variation is investigated for varying runout parameters by experimental tests. In the next part, the model-based runout identification method is developed, which identifies runout parameters accurately from the measured process forces. The approach has been tested extensively and was verified by measured runout parameters and the correlation of surface roughness characteristics of the machined workpiece. The performance of the developed approach is demonstrated in the final part by comparing the result of the model-based surface reconstruction with the measured surface topography.     

A torsional resonance mode AFM for in-plane tip surface interactions

Changing the method of tip/sample interaction leads to contact, tapping and other dynamic imaging modes in atomic force microscopy (AFM) feedback controls. A common characteristic of these feedback controls is that the primary control signals are based on flexural deflection of the cantilever probes, statically or dynamically. We introduce a new AFM mode using the torsional resonance amplitude (or phase) to control the feedback loop and maintain the tip/surface relative position through lateral interaction. The torsional resonance mode (TRmode™) provides complementary information to tapping mode for surface imaging and studies. The nature of tip/surface interaction of the TRmode facilitates phase measurements to resolve the in-plane anisotropy of materials as well as measurements of dynamic friction at nanometer scale. TRmode can image surfaces interleaved with TappingMode™ with the same probe and in the same area. In this way we are able to probe samples dynamically in both vertical and lateral dimensions with high sensitivity to local mechanical and tribological properties. The benefit of TRmode has been proven in studies of water adsorption on HOPG surface steps. TR phase data yields approximately 20 times stronger contrast than tapping phase at step edges, revealing detailed structures that cannot be resolved in tapping mode imaging. The effect of sample rotation relative to the torsional oscillation axis of the cantilever on TR phase contrast has been observed. Tip wear studies of TRmode demonstrated that the interaction forces between tip and sample could be controlled for minimum tip damage by the feedback loop.     

A study on the effect of surface topography on rough friction in roller contact

The friction behaviour of gear teeth in the context of tribology can have a strong effect on housing vibration, noise and efficiency. One of the parameters that greatly influences the friction under certain running conditions is surface roughness. In this work, rough friction was studied in lubricated sliding of roller surfaces, which were manufactured to simulate the real gear surfaces. By examining 3D surface topography of two mating bodies, both surface roughness and its effect on friction behaviour can be studied. In a previous study, a rough-friction test rig has been designed, constructed and initially verified. The types of surfaces involved in this study are ground, shot-peened, phosphated and electrochemically deburred. These rollers were subjected to the same friction testing procedures. Roller surfaces were then examined, and correlation between the topography and the frictional behaviour was analysed. Friction behaviour was interpreted in terms of Stribeck curves (friction coefficient as the function of Hersey parameter (ην/p)). The results showed that electrochemically deburred and certain phosphated surfaces provide lower friction coefficient values which are competitive to fine-ground surfaces in lubricated rolling/sliding contact.