• Title/Summary/Keyword: Brittle material

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Evaluation of Fracture Strength and Material Degradation for Weldment of High Temperature Service Steel Using Advanced Small Punch Test

  • Lee, Dong-Hwan
    • Journal of Mechanical Science and Technology
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    • v.18 no.9
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    • pp.1604-1613
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    • 2004
  • This paper presents an effective and reliable evaluation method for fracture strength and material degradation of the micro-structure of high temperature service steel weldment using advanced small punch (ASP) test developed from conventional small punch (CSP) test. For the purpose of the ASP test, a lower die with a minimized ${\Phi}$1.5 mm diameter loading ball and an optimized deformation guide hole of ${\Phi}$3 mm diameter were designed. The behaviors of fracture energy (E$\_$sp/), ductile-brittle transition temperature (DBTT) and material degradation from the ASP test showed a definite dependency on the micro-structure of weldment. Results obtained from ASP test were compared and reviewed with results from CSP test, Charpy impact test, and hardness test. The utility and reliability of the proposed ASP test were verified by investigating fracture strength, behavior of DBTT, and fracture location of each micro-structure of steel weldment for test specimen in ASP test. It was observed that the fracture toughness in the micro-structure of FL+CGHAZ and ICHAZ decreased remarkably with increasing aging time. From studies of all micro-structures, it was observed that FGHAZ microstructure has the most excellent fracture toughness, and it showed absence of material degradation.

Out-of-plane ductile failure of notch: Evaluation of Equivalent Material Concept

  • Torabi, A.R.;Saboori, Behnam;Kamjoo, M.R.
    • Structural Engineering and Mechanics
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    • v.75 no.5
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    • pp.559-569
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    • 2020
  • In the present study, the fracture toughness of U-shaped notches made of aluminum alloy Al7075-T6 under combined tension/out-of-plane shear loading conditions (mixed mode I/III) is studied by theoretical and experimental methods. In the experimental part, U-notched test samples are loaded using a previously developed fixture under mixed mode I/III loading and their load-carrying capacity (LCC) is measured. Then, due to the presence of considerable plasticity in the notch vicinity at crack initiation instance, using the Equivalent Material Concept (EMC) and with the help of the point stress (PS) and mean stress (MS) brittle failure criteria, the LCC of the tested samples is predicted theoretically. The EMC equates a ductile material with a virtual brittle material in order to avoid performing elastic-plastic analysis. Because of the very good match between the EMC-PS and EMC-MS combined criteria with the experimental results, the use of the combination of the criteria with EMC is recommended for designing U-notched aluminum plates in engineering structures. Meanwhile, because of nearly the same accuracy of the two criteria and the simplicity of the PS criterion relations, the use of EMC-PS failure model in design of notched Al7075-T6 components is superior to the EMC-MS criterion.

A Study on the Generation of Mirror-like Surface and Simulation in Grinding Condition by Inprocess Electrolytic Dressing (연속 전해드레싱의 연삭조건변화에 의한 경면생성 및 시뮬레이션에 관한 연구)

  • 김정두;이연종
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.2962-2969
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    • 1993
  • Recently, a study on the mirror-like surface grinding of brittle materials is active and as branch of these study, new dressing method for superabrasive wheel, electrolytic inprocess dressing(Elid) was developed. Using Elid, the mirror-like surface of brittle material can be generated without polishing or lapping process. In the future, Elid grinding will take important place in industry. But so far the analysis on Elid grinding was not quantitative but qualitative. In this study, The purpose is the quantitative analysis on Elid grinding by computer simulation, For computer simulation, the mean and the variance of the abrasive distribution were measured by tracing of the grinding wheel with stylus in transverse direction in the case of respective dressing current condition. This measurement result in a density distribution of abrasive by mathematical formulation using statistical method. The prediction of the surface roughness in Elid grinding was based on this density distribution.

A Study on the Fracture behavior in Silicon Wafer using the Ultra-Precision Micro Positioning System (초미세 위치결정시스템을 이용한 실리콘 웨이퍼의 파괴거동에 관한 연구)

  • 이병룡
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.9 no.1
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    • pp.38-44
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    • 2000
  • The background of this study lies in he investigation of the formation mechanism of ductile mode(nkanometer-size) chips of brittle materials such as fine ceramics glass and silicon. As the first step to achieve this purpose this paper intends to observe the micro-deformation behavior of these materials in sub${\mu}{\textrm}{m}$ depth indentation tests using a diamond indentor. In this study it was developed Ultra-Micro Indentation. Device using the PZT actuator. Experimentally by using the Ultra-Micro Indentation device the micro fracture behavior of the silicon wafer was investigated. It was possible that ductile-brittle transition point in ultimate surface of brittle material can be detected by adding an acoustic emission sensor system to the Ultra-Micro Indentation appartus.

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경취 재료의 ELID(Electrolytic In-Process Dressing) 경면 연삭 절단에 관한 연구

  • 김화영;안중환;부산대기계공학부
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 1995.10a
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    • pp.65-68
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    • 1995
  • A slicing method by thin diamond blade is widely usd slicing of hard and brittle materials such as ceramics,glass and ferrite etc.. In this study, a new slicing system which realizes highly efficient and mirror surface slicing was developed by applying ELID-grinding with metallic bond diamond blades and its performance was evaluated. Hard and brittle materials such as ceramics,glass and ferrite were used as workpiece. Metallic bond diamond blades with grit sizes #325 and #2000 were used. Experimental results show that highly efficient slicing and good mirror surface can be successfully obtained using the developed slicing system with ELID features.

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Nano-turning of single crystal silicon (단결정 실리콘의 초정밀가공)

  • 김건희;도철진;홍권희;유병주;원종호;박상진;안병민
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2000.11a
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    • pp.939-942
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    • 2000
  • Single point diamond turning technique for optical crystals is reported in this paper. The main factors influencing the machined surface quality are discovered and regularities of machining process are drawn. Optical crystals have found more and more important applications in the field of modern optics. Optical crystals are mostly brittle materials of poor machinability. The traditional machining method is polishing which has many shortcomings such as low production efficiency, poor ability to be automatically controlled and edge effect of the workpiece. The purpose of our research is to find the optimum machining conditions for ductile cutting of optical crystals and apply the SPDT technique to the manufacturing of ultra precision optical components of brittle material.

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Characteristic of Ductile Regime AFM Machining Using Acoustic Emission (AE를 이용한 AFM 연성 영역 가공 특성 연구)

  • Ahn Byoung-Woon;Lee Kwang-Ho;Lee Seoung-Hwan
    • Transactions of the Korean Society of Machine Tool Engineers
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    • v.15 no.4
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    • pp.15-21
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    • 2006
  • Recently, atomic force microscope(AFM) with suitable tips is being used for nano fabrication/nanometric machining purposes. In this paper, acoustic emission(AE) was introduced to monitor the nanometric machining of brittle materials(silicon) using AFM. In the experiments, AE responses were sampled, as the tip load was linearly increased(ramped load), to investigate the machining characteristics during a continuous movement. By analyzing the experimental results, it can be concluded that measured AE energy is sensitive to changes in the mechanism of material removal including the ductile-brittle transition during the nanometric machining. The critical depth of cut value for the transition is evaluated and discussed.

A Study on the Mirror Surface Grinding of Optical Glass Utilizing Electrolytic In-Process Dressing (전해 인프로세스 드레싱을 이용한 Optical glass계의 경면연삭에 관한 연구)

  • 조주현;원종호;박원규;이진오;김민수;김성수
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 2003.04a
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    • pp.410-415
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    • 2003
  • Electrolytic In-process Dressing (ELID) technique for metal bonded diamond grinding wheel has been developed for mirror surface grinding of hard and brittle materials. This study process optical glass in using Electrolytic In-process Dressing. In using to main variable wheel speed (400rpm~2000rpm),feed rate (5$\mu\textrm{m}$/min~25$\mu\textrm{m}$/min),depth of cut (3$\mu\textrm{m}$~5$\mu\textrm{m}$),dressing and spray. We measured surface roughness in representative brittle materials

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Development of Ultra-Micro Indentation Device using the PZT Actuator (압전구동기를 이용한 초미세 압입장치의 개발)

  • 박기태;박규열;홍동표
    • Proceedings of the Korean Society of Machine Tool Engineers Conference
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    • 1999.05a
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    • pp.51-55
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    • 1999
  • Recently, manufacturing work has been transformed to advanced technology intensive form from mass production with a little items required in the past. It was demanded that superior workpiece surface integrity. However, the study of ductile mode machining was proceeded actively.In this paper, it is developed Ultra-Micro Indentation Device using the PZT actuator. Experimentally, by using theUltra-Micro Indentation device, the micro fracture behavior of the silicon wafer was invesgated. It was possible that ductile-brittle transition point in ultimate surface of brittle material can be detected by adding an acoustic emission sensor system to the Ultra-Micro Indentation apparatus.

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A Closed-Form Solution for Circular Openings in an Elastic-Brittle-Plastic Extended Spatial Mobilized Plane Medium

  • Wu, Chuangzhou;Guo, Wei;Jang, Bo-An
    • The Journal of Engineering Geology
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    • v.32 no.1
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    • pp.1-12
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    • 2022
  • Based on the extended spatial mobilization plane (SMP) criterion, we present an elastic-brittle-plastic solution for an axisymmetric cylindrical tunnel. The influences of the intermediate principal compressive stress and material strain-softening behavior are considered. Closed-form formulas for the critical support force, radius of plastic zone, and distributions of stress and displacement in surrounding rock are proposed. The elastic-plastic solution based on SMP is compared with the Kastner solution to verify the credibility of the obtained elastic-plastic solution. The elastic-brittle-plastic solution following the SMP criterion and the current solution based on the Mohr-Coulomb criterion are also compared. The rock strain-softening rate and the intermediate principal stress affect the stability of the surrounding rock. The results provide guidance for optimizing the design of support systems for tunnels.