Investigation on coupling analysis method of bending fatigue damage and sliding wear damage

Yutao Yan,Zhao Zhang,Kai Feng 대한기계학회 2023 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.37 No.9

Bending fatigue and sliding wear are two main damage forms of mechanical components failure and are widely present in mechanical products. The two damages are interrelated and complicated in active system. Therefore, it is incomplete to use any single damage criterion for the analysis and design. This paper proposes a coupling analysis method of bending fatigue damage and sliding wear damage in typical linear contact. A model of the coupling damage is established and the applicable failure criterion based on damage contribution rate is determined. The rationality and practicability of the coupling analysis method proposed are verified by the example and experiment. It is shown that the equivalent stress increases with increasing of wear depth and normal load, the life of coupling damage reduces, and the typical inflection points appear in the coupling damage life curve, which indicates the failure mode changed.

Effects of ZrB2 Nanoparticles on the Microstructures and Tensile Properties of a Hot Extruded In Situ AA6111 Composite

Ran Tao,Yutao Zhao,Gang Chen,Xizhou Kai 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.12

Particle-reinforced aluminum matrix composites (PRAMCs) always show a low forming stability because the particles areeasily separated from the matrix, leaving voids and forming cracks. Extruded in situ PRAMCs are gradually replacing ex situPRAMCs due to the higher interface bonding between the in situ reinforcements and matrix. In this study, a hot-extrudedin situ AA6111 composite with ZrB2nanoparticles was obtained from an Al-Zr-B system. The effects of the ZrB2contenton the geometrically necessary dislocation (GND) density, grain size, grain boundaries, textures and tensile properties ofAA6111 composites were researched. The results showed that as the volume fraction of ZrB2increased, the mean GNDdislocation density increased from 1.53 × 1015m−2 to 3.23 × 1015m−2, and most dislocations were located around the ZrB2nanoparticle clusters. In addition, an increase in the ZrB2content decreased the frequency of high-angle grain boundaries(HAGBs) from 79.28 to 69.45% and increased the frequency of low-angle grain boundaries (LAGBs). ZrB2nanoparticleclusters which were located along the grain boundaries promoted continuous dynamic recrystallization (CDRX) and remarkablyrefined the grains, with the mean size decreasing from 48.2 to 1.8 μm. However, dispersed ZrB2nanoparticles inside thegrains suppressed CDRX. Tensile tests showed that the properties rose dramatically with an increasing volume fraction ofZrB2,and the optimum ultimate tensile strength (UTS), yield strength (YS) and elongation (El) of the 2 vol% ZrB2/AA6111composite were 365 MPa, 280 MPa, and 25.6%, respectively. The mechanisms for CDRX, strengthening and plasticityenhancement were determined and discussed.

AlGaN/GaN Metal-Insulator-Semiconductor (MIS)-HFETs Based DC-DC Boost Converters with Integrated Gate Drivers

Miao Cui,Qinglei Bu,Yutao Cai,Ruize Sun,Wen Liu,Huiqing Wen,Sang Lam,Yung. C. Liang,Ivona Z. Mitrovic,Stephen Taylor,Paul R. Chalker,Cezhou Zhao 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5

This study proposed a 100 kHz, 5V/11V boost converter with an integrated gate driver for a power switching device using recessed E-mode MIS-HFETs. The integrated gate driver consisting of multi-stages DCFL (Direct-Coupled FET Logic) inverters and a buffer stage, has large input swing (up to 10 V) and wide noise margin with gate dielectric, which benefits applications requiring large gate swing without any additional drivers or level shifters. The impact of transistor size on rise times and fall times have been studied. Either buffer stage or larger width of DCFL inverter can reduce rise times from 2.4 μs to less than 0.5 μs at 100 kHz, so the output voltage of boost converter is increased by 10 % at a duty cycle of 0.7. However, large buffer width can result in high gate overshoot and oscillation, indicating careful design to balance switching speed and oscillation.

Creep Fracture Mechanism of a Single Crystal Nickel Base Alloy Under High Temperature and Low Stress

Xiangfeng Liang,Jili Wu,Yutao Zhao 대한금속·재료학회 2022 METALS AND MATERIALS International Vol.28 No.4

This paper reports the creep behavior of a nickel-based single crystal alloy and the creep fracture mechanism under hightemperature and low stress was discussed. The creep curves were analyzed with the Kelvin model. The retardation spectrasuggest that the involved atoms during creep need more relaxation time to achieve the viscous flow, nevertheless, the creepunder the stress of 120 MPa may be caused by the mismatch of dislocation motion and visco-plastic deformation. The fracturemorphologies of crept alloys indicate that the nickel base single crystal alloy presents micro-pore aggregation fracturemechanism under the condition of high temperature and low stress creep.

Vibrational Energy Properties of Twin–Block Ballastless Track with Anti–vibration Structure on Bridge by Power Flow Analysis

Na Fu,Zhenhang Zhao,Yutao Liu,Yuxiang Li 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.2

This article aims to investigate the vibrational energy properties of the twin–block ballastless track with anti–vibration structure (TBTAS) by mobility power flow method. Power flow of the components in TBTAS and bridge are deduced and power flow transfer rate is proposed to present the vibrational energy transmission property of the TBTAS–bridge system. Power flow of rail, twin–block slab and bridge in frequency domain is calculated based on a train–track–bridge interaction model. The effect of the stiffness of the elastic pad on power flow is discussed. The results show that the power flow of the rail exhibits a broad peak in the frequency range of 100 − 400 Hz which corresponds to the broad peak of the rail mobility and exhibits another peak around 1,000 Hz which is the pinned–pinned vibration frequency of the rail. By using elastic pad, the power flow of the bridge reduces by a maximum of 43 dB in the frequency range of 1 − 1,000 Hz. The power flow transfer rate shows that the vibrational energy concentrates in the slab. The vibrational energy of slab and bridge reaches the balance when the stiffness of the elastic pad is 40 MPa/m.

A Method for Generating Malware Countermeasure Samples Based on Pixel Attention Mechanism

Xiangyu Ma,Yuntao Zhao,Yongxin Feng,Yutao Hu 한국인터넷정보학회 2024 KSII Transactions on Internet and Information Syst Vol.18 No.2

Studies have shown that malware has become a primary means of attacking the Internet. Therefore, adversarial samples have become a vital breakthrough point for studying malware. By studying adversarial samples, we can gain insights into the behavior and characteristics of malware, evaluate the performance of existing detectors in the face of deceptive samples, and help to discover vulnerabilities and improve detection methods for better performance. However, existing adversarial sample generation methods still need help regarding escape effectiveness and mobility. For instance, researchers have attempted to incorporate perturbation methods like Fast Gradient Sign Method (FGSM), Projected Gradient Descent (PGD), and others into adversarial samples to obfuscate detectors. However, these methods are only effective in specific environments and yield limited evasion effectiveness. To solve the above problems, this paper proposes a malware adversarial sample generation method (PixGAN) based on the pixel attention mechanism, which aims to improve adversarial samples' escape effect and mobility. The method transforms malware into grey-scale images and introduces the pixel attention mechanism in the Deep Convolution Generative Adversarial Networks (DCGAN) model to weigh the critical pixels in the grey-scale map, which improves the modeling ability of the generator and discriminator, thus enhancing the escape effect and mobility of the adversarial samples. The escape rate (ASR) is used as an evaluation index of the quality of the adversarial samples. The experimental results show that the adversarial samples generated by PixGAN achieve escape rates of 97%, 94%, 35%, 39%, and 43% on the Random Forest (RF), Support Vector Machine (SVM), Convolutional Neural Network (CNN), Convolutional Neural Network and Recurrent Neural Network (CNN_RNN), and Convolutional Neural Network and Long Short Term Memory (CNN_LSTM) algorithmic detectors, respectively.