• Title, Summary, Keyword: hardness

Search Result 9,693, Processing Time 0.064 seconds

An Effect Analysis of Rearfoot Movement and Impact force by Different Design of Running Shoes Hardness (런닝화의 경도 차이가 후족 제어 및 충격력에 미치는 영향 분석)

  • Lee Dong-Choon;Lee Woo-Chang
    • Proceedings of the Society of Korea Industrial and System Engineering Conference
    • /
    • /
    • pp.291-296
    • /
    • 2002
  • The midsole hardness of athletic footwear affects capability of absorbing impact shock and controls rearfoot movement during running and walking. The prior studies were focused on examining the proper hardness of footwear for rearfoot movement or to finding effective hardness for absorbing impact shock. The displacements of maximal Achilles tendon angle described a amount of pronation motion is decreased when medial hardness of midsole is large more than lateral. Increasing hardness of footwear midsole are effected to reduce maximum and intial pronation angle, but declined the ability of impact shock during heelstrike. For determination of effectiveness hardness of midsole, therefore, the study that makes a compromise between rearfoot movement and absorbing impact during footstrike must be performed. The purpose of this study is to examine quantitative values of rearfoot control and absorbing impact shock with different hardness of medial and lateral midsole on heel portion. The results are useful to define biomechanical hardness of midsole for developing running shoes. As variable for impact shock, accelerations onto shank and knee are measured during 4 running speeds (5, 7, 9, 11km/h). Also, maximum and $10\%$ pronation angle (Achilles tendon angle) were measured using high-speed camera.

  • PDF

The Change of Sliding wear properties of Carbon Steel against several hardened steels (미끄럼 접촉을 하는 탄소강의 경도차 조합에 따른 마모특성변화 연구)

  • Lee Han Yeong;Kim Geun Yeong
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
    • /
    • /
    • pp.85-90
    • /
    • 2003
  • Although wear resistance of material improves with increasing its hardness, it is known that the wear resistance of steel is varied with hardness of counter material. In this context, wear properties of steel must be depended on the difference of hardness between the testpiece and the counter material. In this study, using the pin-on-disc type wear machine, annealed carbon steels were tested against ahoy tool steels with various levels of hardness. Then the changes of wear properties of carbon steel according to the hardness of counter material were investigated and the morphology of worn surface after test were evaluated. The results indicate that if there are no remarkable difference of hardness between them, wear resistance of carbon steel in running-in wear decreases with increasing the hardness of counter material. However, its wear properties at the range of high sliding speed have no relation with hardness of counter material. It is clear that wear properties is influenced by the formation of oxide of steel on their worn surface during wear.

  • PDF

Effect of Hot-stamping Heat Treatment on Microstructure and Hardness in TWB Laser Joints of Al-Si-coated Boron Steel and Zn-coated DP Steel (Al-Si 도금된 보론강과 Zn 도금된 DP강의 TWB 레이저 용접부 미세조직과 경도에 미치는 핫 스탬핑 열처리의 영향)

  • Jung, Byung-Hun;Kong, Jong-Pan;Kang, Chung-Yun
    • Korean Journal of Metals and Materials
    • /
    • v.50 no.3
    • /
    • pp.224-232
    • /
    • 2012
  • In this study, the effect of hot-stamping heat treatment on the microstructure and hardness of TWB(Tailor Welded Blank) laser joints in Al-Si-coated boron steel and Zn-coated DP(Dual Phase)590 steel was investigated. In the TWB joints without heat treatment, hardness profiles showed local hardness deviation near the fusion zone. However, there was no hardness deviation in the heat treated specimen and its hardness was higher than that of the one without the heat treatment, due to a fully martensite microstructure. In the TWB joints of both the boron and DP steels, the maximum hardnesses were observed at the HAZ(Heat Affected Zone) near the base metal, and the hardness decreased gradually to the base metal. In the heat treated joints, the hardnesses of the HAZ and the base metal of the boron steel side were similar to the maximum hardness of the weld, while those of the HAZ and the base metal of the DP steel side were higher than the maximum hardness.

Surface Hardness and Water Repellet of Earth Paint (흙페인트의 적절한 사용을 위한 표면경도 및 발수성에 관한 연구)

  • Hawng, Hey-Zoo;Roh, Tea-Hak;Lee, Jin-Sil
    • KIEAE Journal
    • /
    • v.16 no.3
    • /
    • pp.83-88
    • /
    • 2016
  • Purpose : This study aimed to verify the surface hardness and water repellency of earth paint manufactured with earth, a natural material, and provide the results as basic data for paint made with natural materials. Method : After presenting the accurate manufacturing methods for basic materials for paint, the authors conducted and analyzed experiments to evaluate surface hardness and water repellency, fundamental performance indicators for paint, based on different mixture ratios. From the results of the experiment to assess the surface hardness of flour-based earth paint, we observed high surface hardness only after painting the specimen three times. Since potato starch-based earth paint has higher viscosity than its flour-based counterpart, the former did not paint well on the first occasion, resulting in low surface hardness. After painting two or more times, however, it was observed to have higher surface hardness than flour-based earth paint. Result : It was found that at least three iterations of painting was required to obtain high surface hardness of potato starch-based earth paint. Furthermore, the results of the water resistance experiment of earth paint suggest that the use of environment-friendly finishing materials coupled with boiled linseed oil will mitigate the drawbacks of earth paint. The experiment with one-year-old specimens also demonstrated similar water repellent characteristics, which indicates that the performance will improve once the paint has dried for a sufficient period of time.

Effect of fluoride varnishes on the surface hardness of bovine teeth under demineralization/remineralization cycling

  • Son, Ju-Lee;Shin, Yoon-Jeong;Jeong, Geon-Hee;Choi, Shin-Jae;Oh, Seunghan;Bae, Ji-Myung
    • The Journal of the Korean dental association
    • /
    • v.58 no.6
    • /
    • pp.324-335
    • /
    • 2020
  • We investigated whether fluoride varnishes recover the hardness of bovine teeth under 20 days of demineralization/remineralization cycling. The fluoride varnish groups (two commercial fluoride varnishes [V-varnish (Vericom, Korea) and CavityShield (3M ESPE, USA)] and an experimental fluoride varnish including 5 wt.% NaF were compared with a control group without fluoride varnish. Vickers hardness was measured at baseline, 3 days after immersion in caries-inducing solution, 24 hours after application of a fluoride varnish, and after 10 and 20 days of demineralization/remineralization cycling. Afterward, tooth surfaces were observed by scanning electron microscope. After fluoride varnish application and the cycling 10 and 20 days, the experimental varnish group showed the highest hardness, while the CavityShield and the control groups demonstrated the lowest hardness. The experimental varnish group recovered the hardness of the baseline at 24 hours after application of the varnish, while it was recovered after 20 days of the cycling in case of the V-varnish. However, the CavityShield and the control groups did not recover the hardness even after 20 days of the cycling. The experimental fluoride varnish with fast recovery in the hardness of the baseline can be used as an effective fluoride varnish to resist demineralization and to facilitate remineralization.

  • PDF

THE PHYSICAL PROPERTIES OF REUSED IPS EMPRESS CERAMIC PART IV : HARDNESS AND FRACTURE TOUGHNESS (반복 사용된 IPS Empress ceramic의 물리적 성질에 관한 연구 Part IV : 경도 및 파괴인성에 관한 연구)

  • Jin Tai-Ho
    • The Journal of Korean Academy of Prosthodontics
    • /
    • v.41 no.4
    • /
    • pp.532-537
    • /
    • 2003
  • Statement of the problem : IPS Empress ceramic has been used as one of a esthetic restorative material since it's development, but the broad application of IPS Empress ceramic to clinical prosthodontic field has been limited by its high material cost. Purpose : This study was investigated to evaluate the hardness and fracture toughness after recycling of the IPS Empress ceramic. Material and methods : Reused specimens of IPS Empress were fabricated with repeated pressing. The hardness(Vickers hardness) and fracture toughness of 1st, 2nd and 3rd pressed specimens were measured with Digital Micro Hardness Tester(Model MXT70, Matsuzawa Seiki Co., Ltd, Tokyo, Japan). The obtained data were analyzed using SPSS(Ver 9.5). Result : The mean value of the hardness in the 1st, 2nd and 3rd pressed Empress were $6.23{\pm}0.48MPa,\;5.50{\pm}0.25MPa$, and $5.70{\pm}0.42MPa$. The hardness of the 1st pressing ceramic was higher than those or the 2nd and 3rd pressed ceramics(P<0.05). Hardness of the 3rd pressed ceramic was greater than that of the 2nd pressed ceramic. but there was no significant difference of hardness between those two(P>0.05). The mean value of the fracture toughness was $1.71{\pm}0.16MPam^{1/2}$ in 1st pressed ceramic, $1.78{\pm}0.10MPam^{1/2}$ in 2nd pressed and $1.73{\pm}0.14MPam^{1/2}$ in 3rd pressed IPS ceramic. Fracture toughness of the 2nd pressed ceramic was the highest and that of the 1st pressed ceramic was the lowest. There was no significant difference of fracture toughness among them(P>0.05). Conclusion : Hardness of the 2nd and 3rd pressed IPS Empress ceramics were lesser than that of 1st pressed IPS Empress ceramic(P<0.05), but there was no significant changes of fracture toughness among them(P>0.05).

A Study on the Evaluation of Uncertainty of Rockwell Hardness C Scale According to the Korean Industrial Standards(KS) (한국산업표준(KS)에 따른 로크웰 경도 시험기의 불확도 산정에 관한 연구)

  • Bahng, G.W.;Tak, Nae-Hyung
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.13 no.3
    • /
    • pp.163-169
    • /
    • 2000
  • Recently, uncertainty of hardeness became a major concem for the people working on the laboratory evaluation and accreditation. It is required to indicate uncertainty of hardness tester on the report after calibration. In addition to this, uncertainty of certified hardness reference block is also required to indicate on the certification sheet. Method on the evaluation of uncertainty in hardness measurement is agreed only recently for Rockwell hardness C scale. In this paper, a preliminary calculation of uncertainty based on type B evaluation has been made for hardness testers which satisfies the requirements of Korean Standards. It was found that the tolerance limit of mean value specified in KS should be increased to be compatible with the calculated uncertainty.

  • PDF

Analysis on the Results of the Rockwell Hardness Round Robin Test (로크웰 경도도 순회 비교측정 결과에 대한 분석)

  • Bahng, G.W.;Tak, N.H.
    • Journal of the Korean Society for Heat Treatment
    • /
    • v.14 no.5
    • /
    • pp.275-281
    • /
    • 2001
  • To improve the reliability of hardness test results, Rockwell hardness round robin test was carried out for 10 laboratories. The test condition was the same with the ISO(International Standards Organization) standards. Korea Research Institute of Standards and Science(KRISS) supplied the hardness standard blocks and an indenter to laboratories for the measurement. The participating laboratories measured hardness of the specified areas on the blocks for 6 times with their own indenter as well as common indenter, respectively, and reported the results to KRISS. The result showed that quite large amount of the differences came from the indenter and it is necessary to change indenter with better quality for improved reliability in hardness measurement.

  • PDF

A Study on the Effect of Process Parameters to Mechanical Property in Forward Extrusion of Milli-size Cylindrical Pin (밀리 단위의 원형핀 전방압출에 있어서 공정인자가 기계적 성질에 미치는 영향 연구)

  • 심경섭;김용일;이용신;김종호
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.797-801
    • /
    • 2003
  • The mechanical properties such as shear strength and the hardness of milli-size products that manufactured for various process parameters by forward extrusion using square dies are investigated. Shear strength test is implemented for the observation of relation between vickers hardness and shear strength in the interface of head and shaft part of a stepped pin. When the extrusion ratios of pure aluminum and pure copper billets increase, the hardness on both the surface and the center line of a pin also increase, especially the hardness on the surface is shown to be a little higher than on the center. The existence of knock-out pad in extrusion die caused hardness increase in the interface of a extruded pin. As compared shear strength with hardness of a pin, the approximated linear relations are suggested in this study.

  • PDF

A Study on the Analysis of Plastic Zone in Carbon Steel after Strain Aginig (변형시효처리한 탄소강의 소성역 해석에 관한 연구)

  • 손세원;이진수;장정원
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • /
    • pp.933-937
    • /
    • 1996
  • In this paper, the behavior of plastic zone in the notch tip was studied under Loye's Micro Vickers Hardness Measurement Method. The direction forming maximum plastic zone was estimated by finite element analysis. In the experiments, cold rolling sheet SGCD3, SK5 and hot rolling sheet SS41, S4SC was used to study the influence of carbon contents on plastic zone. The standard hardness test specimen and the notch hardness test specimen was made and loaded cyclically. The specimen was aged to stabilize the hardness. After aging treatment, the notch specimen was made and simple tension load of 50% yield strength was applied. The hardness test at the notch tip until the hardness data of standard hardness specimen was checked was performed.

  • PDF