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Frontiers of Structural and Civil Engineering 2022年第8期16卷 1040-1055页

作者： Shuvankar DAS Debarghya CHAKRABORTY Department of Civil Engineering Indian Institute of Technology KharagpurWest Bengal 721302India

In the present study,the stability of a vertical rock escarpment is determined by considering the influence of *** bound finite element limit analysis in association with Power Cone Programming(PCP)is applied to incorporate the failure of rock mass with the help of the Generalized Hoek-Brown yield *** change in stability due to the presence of undercut is expressed in terms of a non-dimensional stability number(σci/γH).The variations of the magnitude ofσci/γH are presented as design charts by considering the different magnitudes of undercut offset(H/vu and wu/vu)from the vertical edge and different magnitudes of Hoek-Brown rock mass strength parameters(Geological Strength Index(GSI),rock parameter(mi),Disturbance factor(D)).The obtained results indicate that undercut can cause a severe stability problem in rock mass having poor *** the help of regression analysis of the computed results,a simplified design equation is proposed for obtainingσci/γ*** performing sensitivity analysis for an undisturbed vertical rock escarpment,we have found that the undercut height ratio(H/vu)is the most sensitive parameter followed by GSI,undercut shape ratio(wu/vu),and *** developed design equation as well as design charts can be useful for practicing engineers to determine the stability of the vertical rock escarpment in the presence of *** patterns are also presented to understand type of failure and extent of plastic state during collapse.

关键词： undercut vertical escarpment stability Hoek-Brown yield criterion PCP

Fabrication of GaN-based LEDs with 22° undercut sidewalls by inductively coupled plasma reactive ion etching

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Chinese Physics B 2013年第10期22卷 445-448页

作者：王波宿世臣何苗陈弘吴汶波张伟伟王巧陈虞龙高优张力朱克宝雷严 Laboratory of Nanophotonic Functional Materials and Devices Institute of Optoelectronic Materials and TechnologySouth China Normal University Key Laboratory for Renewable Energy Chinese Academy of SciencesBeijing Key Laboratory for New Energy Materials and DevicesBeijing National Laboratory for Condense Matter PhysicsInstitute of PhysicsChinese Academy of Sciences

We use a simple and controllable method to fabricate GaN-based light-emitting diodes （LEDs） with 22° undercut sidewalls by the successful implementation of the inductively coupled plasma reactive ion etching （ICP-RIE）. Our exper- iment results show that the output powers of the LEDs with 22° undercut sidewalls are 34.8 rnW under a 20-mA current injection, 6.75% higher than 32.6 mW, the output powers of the conventional LEDs under the same current injection.

关键词： GaN light-emitting diode (LED) undercut

Effect of Thermal Shrinkage of Extruded Sheet on Mouthguard Thickness: Influence of Model undercut

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Materials Sciences and Applications 2022年第1期13卷 54-62页

作者： Mutsumi Takahashi Yogetsu Bando Department of Physiology The Nippon Dental University School of Life Dentistry at Niigata Niigata Japan BANDO Dental Clinic Ishikawa Japan

The effectiveness and safety of the mouthguard are greatly affected by its thickness. The aim of this study was to investigate the effect of thermal shrinkage of the extruded sheet on the mouthguard thickness depending on the amount of undercut of the model. Mouthguard sheet was used a 4.0 mm thick ethylene-vinyl acetate resin manufactured by extrusion molding. The sheets were placed in the vacuum forming machine with the sheet extrusion direction either vertical (condition V) or parallel (condition P) to the model’s centerline. The working models were three hard plaster models trimmed so that the angles of the anterior teeth to the model base were 90?, 100?, and 110? (Models A, B, and C). The sheet was softened until it sagged 15 mm, and then suction was continued for 30 s. Measurement points of the mouthguard were the incisal portion (incisal edge and labial surface) and molar portion (cusp and buccal surface). The differences in the reduction rate of the thickness due to model form and extrusion direction were analyzed using two-way ANOVA and Bonferroni’s multiple comparison tests. Differences in thickness depending on the extrusion direction of the sheet were observed in Models B and C on the labial surface and in all models on the buccal surface, and the thicknesses obtained under condition P were significantly thinner than those obtained under condition V. The thicknesses of the incisal edge and the cusp were not affected by the extrusion direction. The result of this study was suggested that the labial and buccal thickness of the mouthguard was secured by placing the sheet in the extrusion direction vertical to the model’s centerline. Furthermore, it was clarified that the presence of the undercut of the model tends to increase the influence of the extrusion direction of the sheet on the thickness of the mouthguard.

关键词： Mouthguard Extrusion Molding Thickness Model Angle undercut

Effect of undercut defect on deformation behavior TC4 titanium alloy laser welded butt joint under static tensile loading

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China Welding 2020年第2期29卷 30-37页

作者：段爱琴王振书彭欢马旭颐 Science and Technology on Power Beam Process Laboratory Beijing Aeronautical Manufacturing Technelogy Research InstituteBeijing 100024China

By measuring and analyzing infrared thermal image of the specimen in static load tensile test process, it was studied that the influence of the undercut defects and double-sided dressing method on the deformation behavior of the laser welded joint specimens of TC4 titanium alloy. The results showed that for the unmodified specimens, the yield phenomenon occurs first in the region of the joint, but the undercut value has an effect on the stress and strain of starting to yield phenomenon, and a great effect on the plastic deformation *** the undercut is less than a certain value, the large plastic deformation occurs in the base metal region and the plasticity of the specimen is comparable to that of the base metal, but the larger undercut defect results in a concentrated plastic deformation in the joint region and rapidly failed in this region. But the double-sided dressing specimen is significantly different. The physical yield is no longer concentrated in the joint region, but at the same time occurs in the several regions including joint and the base metal. And the plastic deformation mainly occurs in the base material area, similar to that of the base material.

关键词： TC4 titanium alloy laser welding undercut defect static tensile loading infrared thermograph method

Design of undercuts and dipole stabilizer rods for the CPHS RFQ accelerator

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Chinese Physics C 2012年第5期36卷 464-468页

作者：蔡金赤刑庆子关遐龄杜磊 Department of Engineering Physics Tsinghua University Key Laboratory of Particle & Radiation Imaging Ministry of EducationTsinghua University

As part of the design and machining of the RFQ accelerator in the Compact Pulsed Hadron Source （CPHS） project at Tsinghua University, the design process of the undercuts and dipole stabilizer rods is presented in this paper. In particular, the relationship between the inter-vane voltage slope and the local frequency of the undercut section is described quantitatively. With the identification of modes existing in the cavity, the specific parameters are optimized by the SUPERFISH and MAFIA codes. In addition, the water-cooling requirement of the dipole stabilizer rods is briefly discussed.

关键词： RFQ accelerator undercut dipole stabilizer rod

Numerical analysis and experimental research on detection of welding defects in pipelines based on magnetic flux leakage

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Petroleum Research 2023年第4期8卷 550-560页

作者： Changsheng Zhang Jinpeng Bi Yuexia Lv Mengli Li Yongying Qi Kai Zhou Ming Zhang Tingting Du School of Mechanical Engineering Qilu University of Technology(Shandong Academy of Sciences)Jinan 250353China Shandong Institute of Mechanical Design and Research Jinan 250031China CNPC Economics&Technology Research Institute Beijing100120China Shandong Special Equipment Inspection Institute Group Co. Ltd.Jinan 250101China School of Energy and Power Engineering Shandong UniversityJinan 250061China

Regular inspection of long-distance oil and gas pipelines plays an important role in ensuring the safe transportation of oil and gas,and inspection on welding defects is an important part of the inspection *** flux leakage(MFL)is an electromagnetic non-destructive testing technique which has been commonly utilized to detect welding defects in *** the present study,Maxwell electro-magnetic simulation software was used to carry out numerical study on the welding defects in pipelines,including incomplete penetration and ***Ф406 pipeline with a wall thickness of 7 mm was selected as the study case to establish the numerical *** the life-off value at 1 mm,the distribution of magnetic leakage field was investigated for pipeline without defect,pipeline with incomplete penetration defect and pipeline with undercut defect respectively,the characteristic values describing the depth and width of defects were ***,quantified equations which can be used to describe the defect depth were ***,experimental research was carried out to validate the effectiveness of the numerical model,and the experimental results showed good consistence with the numerical calculation *** research results indicate that,it is technically feasible and reliable to diagnose the incomplete penetration and undercut welding defects in pipelines using MFL.

关键词： Magnetic flux leakage Pipeline welding defect Incomplete penetration undercut

Reduction of undercuts in Fillet Welded Joints Using Taguchi Optimization Method

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Journal of Minerals and Materials Characterization and Engineering 2015年第3期3卷 171-179页

作者： Joseph Achebo Sule Salisu Department of Production Engineering University of Benin Benin Nigeria Department of Mechanical Engineering Petroleum Training Institute Effurun Nigeria

This project work focuses on the reduction of weld undercuts using the Taguchi method. The phenomenon of weld undercuts constitutes a major problem for the welding industry. When undercuts occur, and particularly when such cuts are deep, it has a negative impact on the weld as it lowers the integrity and quality of the weldment. Therefore, efforts are made globally to reduce the depth of such weld undercuts to the barest minimum. Several optimization methods have been adopted;however, in this study, the Taguchi method is applied. “The smaller the better components” of the Taguchi method is applied. From the results obtained from applying this Taguchi method, the optimum process parameters obtained are A2-B1-C2, which are a voltage of 20 V, a current of 180 A, and a welding speed of 130 mm/s, required to form an undercut of 0.03 mm. Whereas the existing process parameters used by the company are A1-B3-C, which make an undercut to a depth of 0.09 mm. It is concluded that the use of Taguchi method has been able to reduce the depth of undercut as shown in this study. A step-by-step approach is presented in the study.

关键词： Bead Geometry Fillet Weld Process Parameters Taguchi Method Weld undercut

Design Optimization of Pillar Bump Structure for Minimizing the Stress in Brittle Low K Dielectric Material Layer

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Acta Metallurgica Sinica(English Letters) 2020年第4期33卷 583-594页

作者： Xin-Jiang Long Jin-Tang Shang Li Zhang Key Laboratory of MEMS of Ministry of Education Southeast UniversitySipailou 2#Nanjing 210096China Jiangyin Changdian Advanced Packaging Co. Ltd.No.275 Binjiang RdJiangyin 214400China

Cu pillar bump offers a number of advantages for flip chip packaging,compared to the conventional solder ***,due to its rigidity structure,Cu pillar bump introduces a lot of stress to the chip,which causes the failure of packaging structures,especially for the advanced node devices which typically have brittle low K dielectric *** this paper,for the first time we propose two types of Cu pillar structures to reduce the *** first Cu pillar structure has bigger Cu dimensions at the *** other one is designed to add an additional Cu pad under the Cu pillar *** element analysis is used to study the stress of the both structures,and it is found that with the increase in pillar bump contact area over the chip surface,the stress decreases in both *** also indicate that the Cu pillar bump undercut induces higher stress,and thin Cu6 Snss intermetallic compound has less impact on the stress during flip chip mount *** study provides a novel way to improve the reliability by reducing the stress in the Cu pillar bump related packaging.

关键词： Cu pillar bump Flip chip Low K stress undercut

Static equilibrium model for the bead formation in high speed gas metal arc welding

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China Welding 1998年第1期7卷 25-30页

作者：冯雷陈树君李亮玉殷树言

On the basis of the Young-Laplace Equation that describes the pressure difference between each side of a curved liquid surface, a static equilibrium model is established to describe the surface shape of the weld bead. The geometrical model for the molten pool is included, which is essential to explain the undercut phenomenon during high speed bead-on-plate welding. The results got from an iteration algorithm show that it is the force balance on the liquid mixture of the deposited metal and the molten base metal that causes the undercut. Some factors and their effects are also analyzed.

关键词： static equilibrium Young-Laplace Equation surface tension undercut

关于确定弧齿锥齿轮无根切最小变位系数的新发展

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机械技术史

机械技术史 1998年 634-638页

作者：杨伯原梁桂明洛阳工学院

非零变位原理用于空间传动弧齿锥齿轮设计中,是平衡大、小齿轮的强度,减少齿数,改善啮合性能的好方法。但最基本的是要保证正常的啮合,避免出现根切。这就需要确定在某种齿数条件下的最小变位系数。早期的设计人员在设计中按照弧齿锥齿... 详细信息

非零变位原理用于空间传动弧齿锥齿轮设计中,是平衡大、小齿轮的强度,减少齿数,改善啮合性能的好方法。但最基本的是要保证正常的啮合,避免出现根切。这就需要确定在某种齿数条件下的最小变位系数。早期的设计人员在设计中按照弧齿锥齿轮的当量斜齿轮齿数须大于渐开线斜齿圆柱齿轮无根切最少齿数来确定其最小变位系数,(见下式)。

关键词： Spiral bevel gear undercut modification