多道焊三维残余应力场有限元模拟

运用大型有限元计算软件ABAQUS，对316L不锈钢平板多道焊接头的温度场和残余应力场进行模拟。有限元模型中选用三维实体单元，考虑材料物理性能随温度的变化和周边对流、辐射散热的影响。运用内生热的加载方法模拟焊接热源，运用单元激活技术模拟多道焊焊接过程。获得了三维多道焊焊接温度场和残余应力场，并对计算结果进行分析。     

Noncontact surface roughness measurement of engineering surfaces by total integrated infrared scattering

As precision engineering surfaces are gaining in importance in industry, so are the surface quality requirements. These surfaces have rms roughness typically ranging from some nanometers up to a few micrometers. Although numerous techniques exist for rough surface characterization, from traditional line-scanning stylus profilometers to modern three-dimensional (3-D) measurement instruments, there is a need for a fast, area-covering technique. An efficient method for the characterization of smooth surfaces is elastic light scattering. At visible wavelengths, the limits on roughness range and spatial frequency range make the method unsuitable for characterizing engineering surfaces. By increasing the wavelength of the incident light from the visible to the infrared, elastic light scattering turns out to be applicable for engineering surfaces. We have used total integrated scattering at 10.6 μm wavelength to measure rms roughness up to two micrometers. In this paper, the instrument design and properties are reviewed. We also present results from measurements on ground steel surfaces. Excellent correspondence with mechanical stylus measurements exists for surfaces with rms roughness in the range from 0.1–1.7 μm. The technique shows potential for rapid quality inspection of engineering surfaces.     

表面粗糙度对Al2O3增强Y-TZP陶瓷材料生物摩擦学特性的影响

采用销-盘式摩擦磨损试验机研究了氧化铝增强氧化锆陶瓷(ADZ)的表面粗糙度对ADZ/316L不锈钢摩擦副的摩擦磨损性能的影响。结果表明:在小牛血清润滑下,随着陶瓷表面粗糙度的降低,ADZ陶瓷和316L不锈钢的摩擦因数和磨损率均呈降低趋势。但是对于表面粗糙度最高的陶瓷,由于Fe转移膜的物理吸附,出现了“负磨损”现象。     

Experimental Study of Lubricant Film Thickness Behavior in the Vicinity of Real Asperities Passing through Lubricated Contact

This article presents an experimental study of the influence of real surface micro-geometry on the film thickness in a circular elastohydrodynamic (EHD) contact formed between a real, random, rough surface of steel ball and smooth glass disk. Phase shifting interferometry was used to measure in situ initial undeformed rough surface profiles, whereas thin film colorimetric interferometry provided accurate information about micro-EHD film thickness behavior over a wide range of rolling speeds. Two real roughness features were studied in detail—a 56-nm-high ridge and a 90-nm-deep groove, both transversely oriented to the direction of surface motion. It was shown that the ridge is heavily deformed in a loaded contact and its height increases with increasing rolling speed. The asperity tip film thickness behavior is quite similar to the contact average film thickness when the film thickness is higher than the undeformed ridge height. However, below this limit the film is thicker than what the EHD theory predicts. For the groove, a local reduction in film thickness at the leading edge was observed. When the groove is passing through the EHD conjunction, it maintains its undeformed shape. The behavior of both roughness features studied shows good agreement with previous experimental observations conducted using an artificially produced ridge and groove.     

A Study of Computer Vision for Measuring Surface Roughness in the Turning Process

The paper presents a system for measuring the surface roughness of turned parts using a computer vision system. The images of specimens grabbed by the computer vision system are processed to obtain parameters of their grey levels (spatial frequency, arithmetic mean value, and standard deviation). These parameters are used as input data to a polynomial network. Using the trained polynomial network, the experimental result shows that the surface roughness of a turned part made of S55C steel, measured by the computer vision system over a wide range of turning conditions, can be obtained with reasonable accuracy, compared to that measured by a traditional stylus method. Compared with the stylus method, the computer vision system constructed is a useful method for measuring the surface roughness of this material faster, at a lower cost, and with lower environmental noise.     

Prediction of surface roughness and dimensional deviation of workpiece in turning: a machine vision approach

In the past, roughness values measured directly on machined surfaces were used to develop mathematical models that are used in predicting surface roughness in turning. This approach is slow and tedious because of the large number of workpieces required to obtain the roughness data. In this study, 2-D images of cutting tools were used to generate simulated workpieces from which surface roughness and dimensional deviation data were determined. Compared to existing vision-based methods that use features extracted from a real workpiece to represent roughness parameters, in the proposed method, only simulated profiles of the workpiece are needed to obtain the roughness data. The average surface roughness R _a, as well as dimensional deviation data extracted from the simulated profiles for various feed rates, depths of cut, and cutting speeds were used as the output of response surface methodology (RSM) models. The predictions of the models were verified experimentally using data obtained from measurements made on the real workpieces using conventional methods, i.e., surface roughness tester and a micrometer, and good correlation between the two methods was observed.     

Tribological Performance of Ti–Si-Based in Situ Composites

In this study, a series of Ti–Si-based in situ composites was manufactured by means of a common argon arc melting technique and tribologically evaluated using a sliding ball-on-disc tester under simulated body fluid lubrication. The composite microstructure, mechanical properties, and surface roughness were characterized using light and scanning electron microscopy (SEM), vertical scanning interferometry (VSI), X-ray diffraction (XRD) analysis, and hardness measurements. The evolution of coefficients of friction (COFs) and the appearance of contacting surfaces showed that two the principal wear mechanisms were mixed elastohydrodynamic lubrication (EHL), typically followed by abrasive wear. The mixed EHL was due to the combined effect of serum solution lubrication and surface irregularities, which were produced during the routine surface preparation of samples. The mixed EHL provided the absence of wear and low and stable COFs, which did not depend on the phase composition, microstructure, or hardness of Ti–Si-based alloys. However, in most cases, the change in contact geometry led to the transition from mixed EHL to conventional boundary lubrication, accompanied by increased and unstable friction, adhesive material transfer of metal to the ceramic counterbodies, and abrasive wear. In this respect, the low wear resistance and high adhesion affinity of the titanium matrix of Ti–Si-based alloys should be improved.     

Improved measure of workpiece surface deterioration during turning using non-contact vision method

The surface finish quality of a machined workpiece is commonly measured using the average roughness parameter, R_a. This parameter, however, is insensitive to the lateral changes undergone by the surface in the feed direction as a consequence of tool wear. In this work, the effectiveness of four methods of workpiece surface analysis, namely autocorrelation, cross-correlation, and two new methods, called lateral material shift (LMS) ratio and profile slope ratio (PSR) analyses are investigated. Dry machining experiments were carried out on 316 stainless steel. Images of tool nose and workpiece profiles were captured using digital camera, and the edges were extracted using sub-pixel edge detection. In the autocorrelation approach, each workpiece profile was correlated with a shifted version of the same profile. In the cross-correlation approach, the workpiece profiles at different stages of machining were correlated with a reference profile generated using the unworn tool edge. In the LMS ratio method, the material shift ratios were determined from each waveform on the workpiece profile at various stages of tool wear, while in the PSR method the slopes at the right and left part of the waveform were compared. Among the four methods, the LMS ratio method produced the best correlation with tool flank wear with the maximum R-squared value of 0.9461, while average roughness R_a showed no correlation at all with both major and nose flank wear.     

The influence of AFM and VSI techniques on the accurate calculation of tribological surface roughness parameters

Vertical Scanning Interferometry (VSI) may induce optical artefacts in surface topography measurements. The influence of these optical artefacts on the calculation of R_k surface roughness parameters, contact stiffness and flow factors were studied. Two surface measurement techniques were used: Atomic Force Microscopy (AFM) and VSI. Calibration grids were used to make it easier to isolate the causes of these artefacts, while a real engineering surface was used to compare these two techniques in an industrially applied case. It was found that the optical artefacts have a large influence on all the roughness parameters, contact stiffness and flow factors calculated on the calibration grids. However, for the engineering surface the differences between AFM and VSI measurements were much smaller.     

Effects of Surface Roughness on Point Contact EHL

The effects of orientation of surface roughness, entrainment (rolling) velocity, and slide/roll ratio on micro-elastohydrodynamic lubrication (micro-EHL) are investigated under pointcontact conditions using the optical interferometry technique. Long bumps with constant height and wavelength produced artificially on the surface of a highly polished steel ball are used as a model roughness. It is shown that the asperities are elastically deformed and the magnitude depends on the film factor A, defined by the ratio of the central film thickness based on smooth surfaces to the composite surface roughness, as well as the surface kinematic conditions and the orientation of the asperities. It is also found that a thin or thick oil film formed at the inlet of the contact by a moving rough surface travels through the contact region at a speed very close to the average speed of the contacting surfaces. The possible mechanism is discussed.     

Relation between surface hardening and roughness induced by ultrasonic shot peening

This paper is focused on the identification of a relation between surface hardening and roughness induced by ultrasonic shot peening. A method that dissociates the influence of roughness from the value of the true macroscopic hardness is applied to AISI 316L stainless steel specimens treated using different processing conditions. The true macroscopic hardness is identified and used to determine the surface roughness parameter and scale that give the best relation between hardness and roughness. A relation is identified between the five point pit height S_5V roughness parameter (local depth of roughness) and hardness using a high-pass filter with a cut-off of 100 µm. This power function was identified at a scale that corresponds to the size of the shot impacts.     

Determination of film thickness and surface profile using reflectometry and spectrally resolved phase shifting interferometry

Surface profiling and film thickness measurement play an important role for inspection in semi conductor industry. White light source had been used as scanning white light interferometry and spectrally resolved white light interferometry for determining surface and film thickness profile. These techniques however failed for thinner film. Recently, reflectometry and spectrally resolved white light interferometry was combined for the same. This technique used Fourier Transform for the calculation of phase in spectral domain with the use of Linnik interferometer. In this method a large amount of carrier offset (carrier fringes) is required to be effective. This carrier fringes in spectrally resolved white light interferometry was achieved by increasing the optical path difference between the test and the reference surface. But, Linnik interferometer cause defocusing problem to create these carrier fringes. We propose in this paper to combine reflectometry and spectrally resolved phase shifting interferometry for measurement of surface and film thickness profile with the use of Michelson objective. Michelson objective will be convenient to implement as compared to the Linnik type and the use of phase shifting interferometry does not necessarily need large number of fringes in the spectral domain.     

Relation between roughness and processing conditions of AISI 316L stainless steel treated by ultrasonic shot peening

This article assessed the roughness induced by ultrasonic shot peening. Surface properties of AISI 316L steel specimens were modified through the variation of ultrasonic shot-peening parameters (shot material, shot diameter, sonotrode amplitude vibration and coverage). Each surface was characterized using fifty surface roughness parameters and two types of robust Gaussian filter (low pass and high pass) associated with twenty one cut-off lengths. For each type of processing parameter, the most relevant roughness parameter and its corresponding length scale and filter were found. A linear relationship was identified between the four ultrasonic shot-peening parameters and the mean density of furrows with a coefficient of determination equal to 0.97.     

Characterization of micromachined mirror surfaces from high speed diamond fly cutting

The measurement of the surface finish of diamond “fly-cut” mirrors is discussed. By considering each surface as a series of superimposed sinusoidal gratings, the surface spectral density function (SDF) was calculated from measurements of light scattered from an He-Ne laser beam. The SDF allows examination of the roughness as a function of spatial frequency from which the r.m.s. roughness is calculated. The scattering results are compared with other methods of assessing the surface finish of the mirrors. Results from Talystep measurements compare favourably with those from the lightscattering technique for the smooth copper mirrors, the best of which had a total r.m.s. roughness of 33 Å. The apparatus developed is described. Problems encountered with stylus methods, interferometry and scanning electron microscopy are reported.     

基于超声无损评价的表面粗糙度测量方法

选用不同线切割工艺制备各种表面粗糙度的304不锈钢试块。基于超声波入射到粗糙表面的自由应力边界条件,采用表面回波的幅值均值、离差率和平均功率同时表征粗糙度,根据主成分分析法建立粗糙度的多参数评价模型。实验结果表明,和触针法相比,超声评价法误差最大为3.09%,且其不确定度更低,将该模型用于含粗糙表面试块的晶粒尺寸评价中,评价误差小于5%,可见该方法能有效实现表面粗糙度及材料微观结构的一体化评价,可提高超声自动化评价系统的实用性。     

Tribological Property of Selective Laser Melting–Processed 316L Stainless Steel against Filled PEEK under Water Lubrication

Abstract

As a 3D printing technology, selective laser melting has remarkable advantages such as high processing flexibility, high material utilization, and short production cycle. The applications of selective laser melting technology in industry have become quite extensive. There are many tribological studies on selective laser melting materials, but few based on water lubrication (Zhu, et al., Journal of Zhejiang University-Science A, 19(2), pp 95–110). In this article, the tribological properties of 316L stainless steel processed by selective laser melting and traditional methods have been studied under water lubrication. Polyether ether ketone (PEEK) filled with carbon fiber (CF)/polytetrafluoroethylene (PTFE)/graphite was selected as the counterpart. 316L stainless steel and PEEK are a tribopair commonly used in water hydraulics. This study is of great significance to the application of selective laser melting material of tribopairs in water hydraulics. Friction and wear tests were carried out on a pin-on-disc contact test apparatus under different operating conditions. The friction coefficient, specific wear coefficient, scanning electron microscopy (SEM) of the worn surface, and energy-dispersive spectroscopy (EDS) of the surface adhesions of the three tribopairs were measured and compared. The results revealed that the friction coefficient of the selective laser melting (SLM) 316L stainless steel was significantly higher than that of traditionally processed (TP) 316L stainless steel, which might be caused by the pores on the surface of SLM 316L stainless steel. Adhesion and cutting on the surface of SLM 316L stainless steel were also more serious, resulting in a higher specific wear coefficient of its counterpart PEEK composite compared to PEEK composite against TP 316L stainless steel.     

An experimental investigation on micro machining of fine-grained graphite

Industrial applications of the micro milling process require sufficient experimental data from various micro tools. Research has been carried out on micro milling of various engineering materials in the past two decades. However, there is no report in the literature on micro milling of graphite. This paper presents an experimental investigation on micro machinability of micro milling of moulded fine-grained graphite. Full immersion slot milling was conducted using diamond-coated, TiAlN-coated and uncoated tungsten carbide micro end mills with a uniform tool diameter of 0.5 mm. The experiments were carried out on a standard industrial precision machining centre with a high-speed micro machining spindle. Design of experiments (DoE) techniques were applied to design and analysis of the machining process. Surface roughness, surface topography and burrs formation under varying machining conditions were characterized using white light interferometry, SEM and a precision surface profiler. Influence of variation of cutting parameters including cutting speeds, feedrate and axial depth of cut on surface roughness and surface damage was analysed using ANOVA method. The experimental results show that feedrate has the most significant influence on surface roughness for all types of tools, and diamond tools are not sensitive to cutting speed and depth of cut. Surface damage and burrs analysis show that the primary material removal mode is still brittle fracture or partial ductile in the experimental cutting conditions. 3D intricate micro EDM electrodes were fabricated with good dimensional accuracy and surface finishes using optimized machining conditions to demonstrate that micro milling is an ideal process for graphite machining.     

Developing A Surface Roughness Model for End-Milling of Micro-Channel

Micro-milling operations are one of the common manufacturing processes that are used primarily to produce miniaturized components within the range of less than a millimeter. The surface roughness of the channel plays an important role in the motion of fluid in the channel. Since most traditional finishing operations cannot be performed easily on micro-channels, the study of relationship between micro-milling parameters and surface roughness is of extreme importance. In this work, the geometrical features of cutting edge, along with the concept of minimum chip thickness, are taken into consideration for constructing the micro-channel surface texture using kinematic rules and transformation operators. ACIS, a 3D B-rep geometric kernel, is used as a geometric engine for simulation of surface texture produced in the micro-milling process. In addition, the relationship between cutting conditions and surface roughness is investigated using DOE method and a regression model. All micro-channel experiments were performed on stainless steel 316. Finally, simulation and regression results are compared with measured surface roughness and the validity of these two models is approved. Depending on the available data, one of these two approaches can be used to predict the surface roughness of the channel's floor.     

表面粗糙度对金属平垫泄漏率的影响

为探究金属垫片表面形貌对泄漏率的影响,通过三维形貌仪对不同表面粗糙度的Cu、Al和316L金属垫片进行局部扫描,构建出真实法兰垫片的微观接触模型。在此基础上,进行静力学和计算流体力学分析,通过对流体域设置不同的边界条件,考察不同介质压力下,表面粗糙度和接触压力对泄漏率的影响。仿真结果表明：3种材质的垫片均呈现表面粗糙度越大,则泄漏率越大的趋势;其中,Al垫片的泄漏率对表面粗糙度最为敏感,316L垫片的泄漏率受表面粗糙度的影响最小;当表面粗糙度一定时,施加的接触压力越大,泄漏率越低,但当接触压力达到一定值后,增大接触压力对降低泄漏率的影响将越来越小。     

罐式集装箱罐体用不锈钢板表面质量控制研究

从提高罐式集装箱的原材料---316L不锈钢板表面质量的角度出发,通过对不锈钢冷轧过程中乳化液相关参数的优化,开发了一套适合于罐式集装箱用不锈钢原板的表面质量综合防治技术,并直接应用于现场,获得了良好的效果。