• Title/Summary/Keyword: nominal curve

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The comparison of the fatigue crack initiation life in a notch (노치부의 피로균열발생 수명 비교)

  • Kim, S.H.;Bae, S.I.;Ham, K.C.;Song, J.I.
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.217-222
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    • 2001
  • For the life evaluating of notched members, it is the best way that performing the real fatigue test of structure containing notch. But this method required generally much times and costs to evaluate fatigue life. So, generally we use the modified S-N curve or several methods to predict fatigue life. In this study, crack initiation life was evaluated by fatigue testing the SAE keyhole specimen and smooth specimen made of Al 7075-T6 alloys using the constant load then obtained S-N curve of smooth specimen and P-N curve of SAE keyhole specimen. And, fatigue lives of keyhole specimen are predicted using some life prediction methods (Nominal range I method, Nominal range II method, FEM analysis) for investigating experimented results, and that were compared with experimental data. Predicted fatigue lives by FEM analysis were corresponded with experimental data between 1/3times and 3times on the whole, and predicted fatigue lives using modified S-N curve (Nominal range I method, Nominal range II method) were nonconservative compared with that of FEM analysis.

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Nominal axial and flexural strengths of high-strength concrete columns

  • Al-Kamal, Mustafa Kamal
    • Computers and Concrete
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    • v.24 no.1
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    • pp.85-94
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    • 2019
  • The ACI building code is allowing for higher strength reinforcement and concrete compressive strengths. The nominal strength of high-strength concrete columns is over predicted by the current ACI 318 rectangular stress block and is increasingly unconservative as higher strength materials are used. Calibration of a rectangular stress block to address this condition leads to increased computational complexity. A triangular stress block, derived from the general shape of the stress-strain curve for high-strength concrete, provides a superior solution. The nominal flexural and axial strengths of 150 high-strength concrete columns tests are calculated using the proposed stress distribution and compared with the predicted strength using various design codes and proposals of other researchers. The proposed triangular stress model provides similar level of accuracy and conservativeness and is easily incorporated into current codes.

Comparison of Fatigue Provisions in Various Codes and Standards -Part 1: Basic Design S-N Curves of Non-Tubular Steel Members

  • Im, Sungwoo;Choung, Joonmo
    • Journal of Ocean Engineering and Technology
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    • v.35 no.2
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    • pp.161-171
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    • 2021
  • For the fatigue design of offshore structures, it is essential to understand and use the S-N curves specified in various industry standards and codes. This study compared the characteristics of the S-N curves for five major codes. The codes reviewed in this paper were DNV Classification Rules (DNV GL, 2016), ABS Classification Rules (ABS, 2003), British Standards (BSI, 2015), International Welding Association Standards (IIW, 2008), and European Standards (BSI, 2005). Types of stress, such as nominal stress, hot-spot stress, and effective notch stress, were analyzed according to the code. The basic shape of the S-N curve for each code was analyzed. A review of the survival probability of the basic design S-N curve for each code was performed. Finally, the impact on the conservatism of the design was analyzed by comparing the S-N curves of three grades D, E, and F by the five codes. The results presented in this paper are considered to be a good guideline for the fatigue design of offshore structures because the S-N curves of the five most-used codes were analyzed in depth.

An Analytical Study on the Ultimate Strength of Concrete Poles (콘크리트 전주의 극한강도에 관한 해석적 연구)

  • Shin, Dong-Geun;Yoon, Ki-Yong;Lee, Seung-Hyun;Yi, Gyu-Sei;Kang, Young-Jong
    • Journal of the Korean Society of Hazard Mitigation
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    • v.7 no.5
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    • pp.19-25
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    • 2007
  • In this study, a program based on the P-M interaction curve is developed to calculate the nominal strength of concrete pole. Using this, it is verified to compare with previous studies and the nominal strength$(M_n)$ of concrete pole is calculated. It is less than the rupture strength$(M_r)$ of the design standard. Thus, to increase nominal strength, several parameters are selected like as size of tension and reinforced bars, position of those, number of reinforcement bars, thickness of concrete pole, and diameter of it. The effects of those are analysed in the study. It is supposed that section of concrete pole are satisfied rupture strength.

Nominal flexural strength of high-strength concrete beams

  • Al-Kamal, Mustafa Kamal
    • Advances in concrete construction
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    • v.7 no.1
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    • pp.1-9
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    • 2019
  • The conventional ACI rectangular stress block is developed on the basis of normal-strength concrete column tests and it is still being used for the design of high-strength concrete members. Many research papers found in the literature indicate that the nominal strength of high-strength concrete members appears to be over-predicted by the ACI rectangular stress block. This is especially true for HSC columns. The general shape of the stress-strain curve of high-strength concrete becomes more likely as a triangle. A triangular stress block is, therefore, introduced in this paper. The proposed stress block is verified using a database which consists of 52 tested singly reinforced high-strength concrete beams having concrete strength above 55 MPa (8,000 psi). In addition, the proposed model is compared with models of various design codes and proposals of researchers found in the literature. The nominal flexural strengths computed using the proposed stress block are in a good agreement with the tested data as well as with that obtained from design codes models and proposals of researchers.

Development and Verification of Micro-indentation Technique for Material Property Evaluation of Hyper-elastic Rubber (초탄성고무 물성평가용 미소압입시험법 개발 및 검증)

  • Lee, Hyung-Il;Lee, Jin-Haeng
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.132-137
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    • 2004
  • In this work, effects of hyper-elastic rubber material properties on the indentation load-deflection curve and subindenter deformation are first examined via [mite element (FE) analyses. An optimal data acquisition spot is selected, which features maximum strain energy density and negligible frictional effect. We then contrive two normalized functions. which map an indentation load vs. deflection curve into a strain energy density vs. first invariant curve. From the strain energy density vs. first invariant curve, we can extract the rubber material properties. This new spherical indentation approach produces the rubber material properties in a manner more effective than the common uniaxial tensile/compression tests. The indentation approach successfully measures the rubber material properties and the corresponding nominal stress.strain curve with an average error less than 3%.

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Mechanical characteristics of involute-circular arc composite tooth profile (인벌류우트-圓弧 合成齒形의 諸特性)

  • 변준형;최상훈;윤갑영
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.10 no.6
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    • pp.870-875
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    • 1986
  • In this study, full-rounded tip curve of rack and its mating fillet curve of pinion in Involute-circular arc composite tooth profile are derived. Mechanical characteristics are calculated analytically, i.e., Specific sliding, Nominal bending stress at working root circle and the Contact factor of the arc of contact in circular arc part to the arc of double contact. These characteristics compared with standard involute tooth profile are improved in circular arc part of composite tooth profile. To obtain more efficient composite tooth profile, we studied these characteristics with regard to the changes of unwound angle and radius of circualr arc. And a design method of composite tooth profile is suggested. Composite tooth profile are compared with standard involute tooth profile.

Modeling of a Multi-Leaf Spring for Dynamic Characteristics Analysis of a Large Truck (대형트럭 동특성 해석을 위한 다판 스프링의 모델링)

  • Moon Il Dong;Oh Seok Hyung;Oh Chae Youn
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.10
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    • pp.147-153
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    • 2004
  • This paper presents an analytical modeling technique fer representing a hysteretic behavior of a multi-leaf spring used for a large truck. It divides a nonlinear hysteretic curve of the multi-leaf spring into four parts; loading part, unloading part and two transition parts. It provides conditions fur branching to a part of the curve corresponding to a current multi-leaf spring status. This paper also presents a computational modeling technique of the multi-leaf spring. It models the multi-leaf spring with three links and a shackle. It assumes those components as rigid bodies. The links are connected by rotational joints, and have rotational springs at the joints. The spring constants of the rotational springs are computed with a force from the analytical model of the hysteretic curve of the multi-leaf spring. Static and dynamic tests are performed to verify the reliability of the presented techniques. The tests are performed with various amplitudes and excitation frequencies. The hysteretic curves from the tests are compared with those from the simulations. Since th e presented techniques reproduce the hysteretic characteristic of the multi -leaf spring faithfully, they contribute on improving the reliability of the computational model of a large truck.

Fatigue Life Evaluation Model of Welded Joints With Residual Stress (잔류응력을 고려한 용접 이음부의 피로수명 평가 모델)

  • Goo, Byeong-Choon;Yang, Sung-Yong
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.9
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    • pp.1328-1336
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    • 2004
  • According to our fatigue tests carried out at 20 Hz, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short life range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

Fatigue Life Evaluation Model for Welded feints Based on Nominal Stress and Residual Stress Relaxation (잔류응력 완화를 고려한 공칭응력 기반 용접재의 피로수명 평가 모델)

  • 구병춘;양승용;정흥채;최성규
    • Proceedings of the KWS Conference
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    • 2004.05a
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    • pp.249-251
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    • 2004
  • According to our fatigue tests carried out at 20 ㎐, R=0.1 on transversely butt-welded joints, fatigue strengths of as-welded specimens, that is, specimens having residual stress are higher than those of annealed specimens in short hie range, but vice verse in long life range. This behavior seems to be concerned mainly with residual stress relaxation by applied loading. After analyzing the welding process, we conducted finite element analysis to quantify the degree of residual stress relaxation. By taking into account residual stress relaxation, modified Goodman diagram, and nominal stress, we evaluated the fatigue life of the welded joint from the S-N curve for the parent material. The estimated results are in a good agreement with the experimental results.

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