An Investigation of Chipping Generation and Propagation on Carbide Tool under Various Cutting Conditions in End Milling of Low Carbon Steel

Tool conditions are the essential factors in determining the geometric accuracy and the machined surface quality in the milling process. The different mechanisms of tool condition can be classified as tool wear, chipping, and built-up edge. The chipping, which is one of the decisive tool conditions when the brittle milling tools are used in milling, has not been well investigated by previous studies since the chipping is randomly occurs. Therefore, the main objective of this study is to comprehensively investigate the generation and propagation of chipping in the milling process. To realize this objective, the carbide milling tools were used to dry cut 1020 low carbon steel with different combinations of cutting speed and chip load. Under each combination, the cutting tool was evaluated in terms of various tool conditions over a certain cutting distance until the milling tool failed. The result showed that the chipping mainly occurred under the low spindle speed or high chip load per tooth since the cutting force was high. Once the chipping occurred on one flute, other flutes also had the chipping at the same position since the chipping occurred initially increased the chip load per tooth of the next flute. After the chipping was generated, it extended in the following milling process until the width of chipping met the failure criterion. It is found that most of the chipping extended and met the failure criterion in a short cutting distance. However, the chipping which propagated slowly shown three stages with different expansion rates before the end of tool life. Meanwhile, the flank wear was observed on the outline of chipping and was considered as a factor for the chipping propagation since the flank wear increases with the cutting force. The milling test was stopped at the end of tool life, and it was found that the tool life of all the milling tools was shorter than the tool life estimated by using the Taylor equation. However, the Taylor equation only considers the flank wear as a factor for the tool life, whereas, the chipping was dominated in this study

Salient object detection via sparse representation and multi‐layer contour zooming

Since image background is normally composed of congenial regions, it can be represented by a feature dictionary via sparse representation. Based on this theory, the authors propose a novel bottom‐up saliency detection method that unites the syncretic merits of sparse representation and multi‐hierarchical layers. In contrast to most pre‐existing sparse‐based approaches that only highlight the boundaries of a target, the proposed method highlights the entire object even if it is large. Given a source image, a multi‐scale background dictionary is structured with the features form different layers. Each region of the image is then reconstructed by the dictionary to compute its reconstruction error as a saliency score. Although a reconstruction map can be generated by the saliency scores, it is not good enough to be the final result because of low resolution and high error detection rates. Therefore, in middle cue, they propose a multi‐scale contour zooming approach to address the error detection across the hierarchical layers. To improve the resolution of the final detection, a pixel‐level rectification based on the Bayesian observation likelihood is calculated as the bottom cue. Combining sparse representation and multi‐scale correction, the precision of the final saliency map is significantly improved for the detection results

A Complementary Gray Code Like Double N-Step Phase Shift Method Without Gray Code Fringe Images

The complementary Gray code double N-step phase shift method is widely used because of its high detection accuracy and good robustness. However, phase unwrapping methods have the problem of low detection efficiency. In order to solve above problem, this paper proposes a complementary Gray code like double N-step phase shift method without Gray code fringe images. Firstly, the wrapped phases of the different groups of phase shift fringe images are obtained, then we get the phase difference and the fused wrapped phase, and the phase difference is converted into Gray code series. Finally, the unwrapped phase of the measured target is obtained by combining the fused wrapped phase and the Gray code series. This method in this paper improves the detection efficiency. To verify the effectiveness of method proposed in this paper, the method is compared with the complementary Gray code double N-step phase shift method, the complementary Gray code 2N-step phase shift method and the phase derivative variance method. The experimental results show that the method in this paper could effectively obtain the high-precision unwrapped phase, and the efficiency is 33.3% higher than the complementary Gray code double N-step phase shift method and the complementary Gray code 2N-step phase shift method

The Kinetic Mechanism of the Thermal Decomposition Reaction of Small Particles of Limestone at Steelmaking Temperatures

Converter blowing limestone powder making slag steelmaking process has the advantages of low carbon and high efficiency, and can realize the resource utilization of CO2 in the metallurgical process, which is in line with the development direction of green metallurgy. Based on a thermogravimetric-differential thermal analyzer, the kinetic mechanism of decomposition of small limestone at steelmaking temperatures was investigated by a modified double extrapolation method. The results showed that with a higher rate of heating, limestone decomposition lagged, and decomposition temperature increased. Furthermore, the smaller the limestone particle size, the lower the activation energy of decomposition. Compared with N2, air, and O2, small limestone powder used for converter blowing could complete more rapid decomposition, and the time required for decomposition shortened by about 1/3, although the decomposition temperature increased in the CO2. The limestone decomposition rate increased and then decreased at low to high CO2 partial pressures. With a limiting link, the inhibition was more significant under high CO2 partial pressure, but the reaction can be fully completed by 1000 °C. The decomposition type modeled was stochastic nucleation and subsequent growth. As the partial pressure of CO2 increased from 25% to 100%, the number of reaction stages, n, increased

Effects of High-Temperature Annealing Atmosphere on the Secondary Recrystallization Behavior and Magnetic Properties of Fe-3.2%Si-0.055%Nb Grain-Oriented Silicon Steel

High-temperature annealing is a key step for the secondary recrystallization of grain-oriented silicon steel, which has an important effect on the final sharp Goss texture. In this work, the effects of three different annealing atmospheres during high-temperature annealing (100%H2, 25%N2 + 75%H2 and 50%N2 + 50%H2) on the secondary recrystallization microstructure and texture of Fe-3.2%Si-0.055%Nb low temperature grain-oriented silicon steel were analyzed by optical microscopy (OM) and electron back-scattered diffraction (EBSD) techniques, and the magnetic properties of the samples were compared. The results show that when the high-temperature annealing atmosphere is 100%H2, the texture of the grains with secondary recrystallization is mainly //ND orientation, but the grains without secondary recrystallization have a disordered orientation. When the high-temperature annealing atmosphere is 50%H2 + 50%N2, the secondary recrystallization grains present a Goss texture and brass texture. After high-temperature annealing in the 25%N2 + 75%H2 atmosphere, the sample can be fully recrystallized to obtain secondary recrystallization grains; the grain size is relatively uniform and the texture is mainly a Goss texture with a sharp edge. The content of this reaches 93.1%, the magnetic induction B800 is the highest, reaching 1.89 T, and the iron loss P1.7/50 is the lowest, reaching 1.33 W/kg