On-line tool wear estimation in CNC turning operations using fuzzy neural network model

In recent past, several neural network models which employ cutting forces and AErms or their derivatives for estimation as well as classification of flank wear have been developed. However, a significant variation in mean cutting forces and AErms at the start of cutting operation for similar new tools can result in estimation and classification error. In order to deal with this problem, a new on-line fuzzy neural network (FNN) model is presented in this paper. This model has four parts. The first part of the model is developed to classify tool wear by using fuzzy logic. The second part of this model is designed for normalizing the inputs for the next part. The third part consisting of modified least-square backpropagation neural network is built to estimate flank and crater wear. The development of forth part was done in order to adjust the results of the third part. Several basic and derived parameters including forces, AErms, skew and kurtosis of force bands, as well as the total energy of forces were employed as inputs in order to enhance the accuracy of tool wear prediction. The experimental results indicate that the proposed on-line FNN model has a high accuracy for estimating progressive flank and crater wear with small computational time.     

An experimental investigation on monitoring of crater wear in turning using ultrasonic technique

Tool life prediction and tool change strategies are now based on most conservative estimates of tool life from past tool wear data. Hence usually tools are underutilized. In an unmanned factory, this has the effect of increased frequency of the tool changes and therefore increased cost. An ultrasound online monitoring of crater wear of the uncoated carbide insert during the turning operation is presented. The method relies on inducing ultrasound waves in the tool, which are reflected by side flank surface. The amount of reflected energy is correlated with crater wear depth. Various ultrasonic parameters are considered for defining the crater wear and individual contribution of each parameter is analyzed. The ultrasonic parameters, amplitude, pulse width and root mean square (RMS) of the signal are used to quantify the crater depth and width. The power spectrum analysis of received signals shows the importance of frequency components in defining the tool wear. In the presented work, the normalizing of signals are carried out by insert hole, which is provided for clamping. This signal is not influenced by the wear but affected by other factors like tool material variation, improper couplant, temperature, etc. The response of the wear signal is normalized to the response of hole signal by mathematical division. A new approach adaptive neuro-fuzzy inference system (ANFIS) for monitoring of crater in carbide insert is presented. This improves the system accuracy and eliminates the limitation in statistical modeling that was presented in previous studies.     

The total energy and the total entropy of force signals — new parameters for monitoring oblique turning operations

In unmanned CNC turning operations, the accuracy of tool wear predictions is very important for accurate tool replacement policies and avoiding unnecessary tool insert changes. This paper introduces two new parameters, namely the total energy and the total entropy of force signals, for tool condition monitoring. The correlation between the new parameters, tool wear and a wide range of cutting conditions is examined. The experimental results show that the energy of force signal can be reliably used to monitor tool flank and crater wear over a wide range of cutting conditions. However, the total entropy of forces does not appear to be sensitive to feed rate, rake angle and tool wear. The experimental results also indicate that crater wear causes an increase in the effective rake angle resulting in lower total energy of forces. For some particular shapes of worn tool, however, the crater wear results in a decreased rake angle which increases the total energy of forces. The influence of crater wear on forces and the root mean square of acoustic emission (AErms) signals is also observed in this research.     

Chip formation, cutting forces, and tool wear in turning of Zr-based bulk metallic glass

The chip light emission and morphology, cutting forces, surface roughness, and tool wear in turning of Zr-based bulk metallic glass (BMG) material are investigated. Machining results are compared with those of aluminum 6061-T6 and AISI 304 stainless steel under the same cutting conditions. This study demonstrates that the high cutting speeds and tools with low thermal conductivity and rake angle activate the light emission and chip oxidation in BMG machining. For the BMG chip without light emission, serrated chip formation with adiabatic shear band and void formation is observed. The cutting force analysis further correlates the chip oxidation and specific cutting energy and shows the significant reduction of cutting forces for machining BMG at high cutting speeds. The machined surface of BMG has better surface roughness than that of the other two work materials. Some tool wear features, including the welding of chip to the tool tip and chipping of the polycrystalline cubic boron nitride (PCBN) tool edge, are reported for turning of BMG. This study concludes that BMG can be machined with good surface roughness using conventional cutting tools.     

Preparation and wear performance of NiCr/Cr3C2-NiCr/hBN plasma sprayed composite coating

NiCr clad hexagonal BN powder (NiCr/hBN) was added to NiCr/Cr₃C₂ feedstock to improve the tribological properties of chromium carbide nichrome coating. The microstructure, flowability and apparent density of the composite powder, as well as the structure and mechanical properties of the plasma sprayed coating were characterized. The friction and wear behavior of the NiCr/Cr₃C₂-NiCr/hBN coating from ambient temperature up to 800 °C was evaluated on a ball-on-disk wear tester and compared with that of NiCr/Cr₃C₂ coating and NiCr/Cr₃C₂-NiCr/BaF₂·CaF₂ coating. The results show that NiCr cladding can reduce the decarburization of Cr₃C₂ and oxidation of hBN during the thermal spray. The main wear mechanisms of the NiCr/Cr₃C₂-NiCr/hBN composite coating are ploughing and adhesive wear. Layered hexagonal BN particle reduce the direct contact and severe adhesion between friction pairs, thus decreasing the friction coefficient. The NiCr/Cr₃C₂-NiCr/hBN composite coating shows a promising application in the high temperature environment with the request of both wear resistance and friction reduction.     

超声辅助激光沉积原位TiC-TiB2/Al-12Si铝基复合材料微观组织及摩擦磨损行为研究

以Ti、B₄C和Al-12Si粉末为原材料,通过超声辅助激光沉积制备了原位TiC-TiB₂/Al-12Si铝基复合材料。采用XRD、EDS分析了复合材料的物相组成,通过OM、SEM观察了复合材料的微观组织,利用摩擦磨损试验机和三维轮廓仪测试了复合材料的磨损性能。结果表明,随Ti+B₄C含量的增加,α-Al晶粒细化,原位生成的TiB₂呈棒状,且可成为α-Al的异质形核核心;原位生成的TiC为150nm多边形形貌。随Ti+B₄C含量的增加,原位TiC-TiB₂/Al-12Si铝基复合材料的耐磨性提高;未加入Ti+B₄C的Al-12Si合金磨损机制为疲劳磨损;当Ti+B₄C的加入量为8%(质量分数)时,磨损机制为磨粒磨损;当Ti+B₄C的加入量为10%时,其磨损机制转变为疲劳磨损。     

Investigation of the microwave dielectric properties of Ca1−xMgxLa4Ti5O17 ceramics for application in coplanar patch antenna

In this paper, the dielectric properties of Ca_1−xMg_xLa₄Ti₅O₁₇ ceramics at microwave frequency have been studied. The diffraction peaks of Ca_(1−x)Mg_xLa₄Ti₅O₁₇ ceramics nearly unchanged with x increasing from 0 to 0.03. Similar X-ray diffraction peaks of Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic were observed at different sintering temperatures. A maximum density of 5.3 g/cm³ can be obtained for Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h. A maximum dielectric constant (_r) and quality factor (Q × f) of Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h are 56.3 and 12,300 GHz (at 6.4 GHz), respectively. A near-zero temperature coefficient of resonant frequency (τ_f) of −9.6 ppm/°C can be obtained for Ca_0.99Mg_0.01La₄Ti₅O₁₇ ceramic sintered at 1500 °C for 4 h. The measurement results for the aperture-coupled coplanar patch antenna at 2.5 GHz are presented. With this technique, a 3.33% bandwidth (return loss <−10 dB) with a center frequency at approximately 2.5 GHz has been successfully achieved.     

A literature review and test: Structure and physicochemical properties of spinel LiMn2O4 synthesized by different temperatures for lithium ion battery

A series of LiMn₂O₄ spinel was prepared by adipic acid-assisted sol–gel method at different temperatures. The structure and physicochemical properties of spinel LiMn₂O₄ synthesized by different temperatures were investigated by differential thermal analysis (DTA) and thermogravimetery (TG), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron micrographs (SEM), inductively coupled plasma-mass spectroscopy (ICP-MS), galvanostatic charge–discharge test, and cyclic voltammetry (CV), respectively. TG–DTA shows that the weight loss occurs in four temperature regions during the synthesis of LiMn₂O₄. XRD indicates that the sintering temperature affects the formation of spinel phase, and prominent LiMn₂O₄ spinel powder with smaller atom location confusion forms about 800 °C. XPS reveals that the manganese oxidation state in spinel lithium manganese oxide synthesized at different temperatures is between +3 and +4. SEM shows that LiMn₂O₄ spinel synthesized at 800 °C has the uniform, nearly cubic structure morphology with narrow size distribution. ICP-MS indicates that the average chemical valence of Mn element of LiMn₂O₄ synthesized at 800 °C is the most close to 3.5 among the samples synthesized at different temperatures. CV illustrates that the LiMn₂O₄ synthesized at 800 °C has the best electrochemical activity. Charge–discharge test explains that the capacity retention sintered at 350, 700 and 800 °C over the first 50 cycles is 93.6%, 86.1% and 85.2%, respectively, but the discharge capacity at the 50th cycle is 82.2, 104.8 and 110.8 mAh g⁻¹, respectively.     

State-of-the-art overview of pipeline steel corrosion in impure dense CO2 for CCS transportation: mechanisms and models

This work reviews the existing open literature concerned with pipeline steel corrosion in CO₂-rich phase with impurities for carbon capture and storage purpose. The intent of this review was to provide information on the corrosion mechanisms, which is crucial for establishing the mechanistic prediction models. The primary focus was placed on key affecting parameters and their corresponding mechanisms, while the corrosion control strategies and research prospects are also discussed. This review covers the effects of: impurities, pressure, temperature, flow, exposure time, product layers, and steel chemistry. The influences of flow dynamics, amines, sulphur, and solids that had received little systematic attention need to be further addressed. Contradictory conclusions regarding the influence of H₂O and O₂ on the corrosion rates should be re-evaluated. The localised corrosion and cathodic reaction mechanisms also require further investigation, especially under synergistic conditions with multiple impurities.     

Inhibitive properties, adsorption and a theoretical study of 3,5-bis(n-pyridyl)-4-amino-1,2,4-triazoles as corrosion inhibitors for mild steel in perchloric acid

Corrosion inhibition of mild steel in molar perchloric acid by 3,5-bis(n-pyridyl)-4-amino-1,2,4-triazoles (n-PAT, n = 2, 3 and 4) was studied at 30 °C using gravimetric and electrochemical impedance spectroscopy techniques. Protection efficiencies of 95% and 92% were obtained with 12 × 10⁻⁴ M of 3-PAT and 4-PAT, respectively; while 2-PAT reached only 65%. The inhibiting properties of n-PAT were found to depend on the concentration and the order of increasing inhibition efficiency was correlated with the modification of the position of the nitrogen atom in the pyridinium substituent. It was shown that adsorption of 4-aminotriazole derivatives on the steel surface is consistent with the Langmuir adsorption isotherm and the obtained standard free energy of adsorption () values indicate that the corrosion inhibition of the mild steel in 1 M HClO₄ is depends on both physic-and chemisorption. A significant correlation is obtained between inhibition efficiency and quantum chemical parameters using semi-empirical quantitative structure-activity relationships (QSAR) approach.