The Influence of Diameter-to-Thickness Ratios on the Response and Collapse of Sharp-Notched Circular Tubes under Cyclic Bending

2012 ◽  
Vol 28 (3) ◽  
pp. 461-468 ◽  
Author(s):  
K.-L. Lee ◽  
C.-M. Hsu ◽  
W.-F. Pan
Keyword(s):  
Experimental Finding ◽  
Empirical Relationship ◽  
Cyclic Hardening ◽  
304 Stainless Steel ◽  
Cyclic Bending ◽  
Circular Tubes ◽  
Parallel Lines ◽  
Number Of Cycles ◽  
The Moment ◽  
Good Agreement

AbstractThis paper discusses an experimental investigation of the behavior of sharp-notched circular tubes subjected to cyclic bending. The sharp-notched circular tubes of 304 stainless steel with three different diameter-to-thickness ratios (Do / t) were tested under symmetric curvature-controlled cyclic bending. It has been shown that the moment-curvature curves exhibited the loops with cyclic hardening and gradually becoming steady after a few cycles for all tested tubes. The ovalization-curvature curves revealed unsymmetric, ratcheting and increasing behavior with the number of cycles. In addition, five almost parallel lines corresponding to five different notch depths for each Do / t ratio were found from the experimental relationship between the cyclic controlled curvature and the number of cycles necessary to produce buckling on a log-log scale. Finally, an empirical relationship was proposed so it could be used for simulating the aforementioned relationship. By comparing with the experimental finding, the derived empirical relationship was in good agreement with the experimental data.

Variation of Ovalization for Sharp-Notched Circular Tubes Under Cyclic Bending

2010 ◽  
Vol 26 (3) ◽  
pp. 403-411 ◽  
Author(s):  
K.-L. Lee ◽  
C.-Y. Hung ◽  
W.-F. Pan
Keyword(s):  
Empirical Relationship ◽  
304 Stainless Steel ◽  
Tube Bending ◽  
Steel Tubes ◽  
Cyclic Bending ◽  
Circular Tubes ◽  
Tertiary Stage ◽  
Three Stages ◽  
Number Of Cycles ◽  
Good Agreement

AbstractIn this paper, an experimental investigation on the variation of ovalization for sharp-notched circular tubes subjected to cyclic bending is discussed. The tube bending machine and curvature-ovalization measurement apparatus were used to test the unnotched and sharp-notched 304 stainless steel tubes. For sharp-notched tubes, five different notch depths (0.2, 0.4, 0.6, 0.8 and 1.0mm) were considered in this study. It was found that the experimental curve of the ovalization and the number of cycles could be divided into three stages-an initial, secondary and tertiary stage. An empirical relationship was proposed for simulating the aforementioned curve for the initial and secondary stages in this study. It has been shown that the derived empirical relationship was in good agreement with the experimental data.

Finite Element Analysis on the Response of Local Sharp-Notched Circular Tubes under Cyclic Bending

2014 ◽  
Vol 626 ◽  
pp. 34-39
Author(s):  
Kuo Long Lee ◽  
Yun Wang ◽  
Wen Fung Pan
Keyword(s):  
Finite Element ◽  
Experimental Finding ◽  
Experimental Result ◽  
Notch Depth ◽  
Element Analysis ◽  
Cyclic Bending ◽  
Circular Tubes ◽  
Finite Element Software ◽  
Ansys Analysis ◽  
The Moment

In this study, the finite element software ANSYS was used to analyze the mechanical behavior of local sharp-notched circular tubes under cyclic bending. The local sharp-notched depths include: 0.2, 0.4, 0.6, 0.8 and 1.0 mm, and the local sharp-notched directions include: 0, 30, 60 and 90 degrees. According to the experimental result, the notch depth has no influence on the moment-curvature relationship. But the notch depth increases, the unsymmetrical phenomenon of the ovalization-curvature relationship becomes more obvious and the speed of ovalization accelerates. In addition, the ovalization-curvature relationship becomes symmetrical when the direction angle increases. The ANSYS analysis was compared with the experimental finding. Although some differences between the experimental and simulated results, but both trends were very similar.

Collapse of Sharp-Notched 6061-T6 Aluminum Alloy Tubes Under Cyclic Bending

2016 ◽  
Vol 16 (07) ◽  
pp. 1550035 ◽  
Author(s):  
Chen-Cheng Chung ◽  
Kuo-Long Lee ◽  
Wen-Fung Pan
Keyword(s):  
Finite Element ◽  
Aluminum Alloy ◽  
Cyclic Bending ◽  
Finite Element Software ◽  
Buckling Failure ◽  
Simulation Results ◽  
Number Of Cycles ◽  
The Moment ◽  
The Relationship ◽  
Good Agreement

The mechanical behavior and buckling failure of sharp-notched 6061-T6 aluminum alloy tubes with different notch depths subjected to cyclic bending are experimentally and theoretically investigated. The experimental moment–curvature relationship exhibits an almost steady loop from the beginning of the first cycle. However, the ovalization–curvature relationship exhibits a symmetrical, increasing, and ratcheting behavior as the number of cycles increases. The six groups of tubes tested have different notch depths, from which two different trends can be observed from the relationship between the controlled curvature and the number of cycles required to ignite buckling. Finite element software ANSYS is used to simulate the moment–curvature and ovalization–curvature relationships. Additionally, a theoretical model is proposed for simulation of the controlled curvature-number of cycles concerning the initiation of buckling. Simulation results are compared with experimental test data, which shows generally good agreement.

Effects of Notch Depth and Direction on Stability of Local Sharp-Notched Circular Tubes Subjected to Cyclic Bending

2018 ◽  
Vol 18 (07) ◽  
pp. 1850099 ◽  
Author(s):  
Kuo-Long Lee ◽  
Kao-Hua Chang ◽  
Wen-Fung Pan
Keyword(s):  
Analytical Data ◽  
Cyclic Hardening ◽  
Notch Depth ◽  
Steel Tubes ◽  
Element Analysis ◽  
Cyclic Bending ◽  
Tube Cross Section ◽  
Number Of Cycles ◽  
The Moment ◽  
The Relationship

Cyclic bending of tubes leads to progressive ovalization of the tube cross-section, and persistent cycling causes catastrophic buckling of the tube. This paper presents the response and stability of SUS304 stainless steel tubes with local sharp-notched depths of 0.2, 0.4, 0.6, 0.8, and 1.0[Formula: see text]mm and notch directions of 0[Formula: see text], 30[Formula: see text], 60[Formula: see text], and 90[Formula: see text] under cyclic bending. The experimental results reveal that the moment–curvature relationship first exhibits cyclic hardening and then a steady loop after a few cycles. Because the notches are small and localized, notch depth and direction show minimal influence on the moment–curvature relationship. In contrast, the ovalization–curvature relationship demonstrates an increasing and ratcheting pattern along with the bending cycle, whereas notch depth and direction show a strong influence on this relationship. Finite-element analysis via ANSYS is used to simulate the moment–curvature and ovalization–curvature relationships, and an empirical model is proposed to simulate the relationship between the controlled curvature and number of cycles required to ignite buckling. The experimental and analytical data agree well with each other.

scholarly journals Experimental Study of Cyclic Bending Failure for Round-hole Tubes with a Redundant Round Hole in the Same Direction but Different Cross Sections

2020 ◽  
Vol 9 (2) ◽  
pp. 83-92
Author(s):  
Kuo-Long Lee ◽  
Wen-Fung Pan
Keyword(s):  
Aluminum Alloy ◽  
Cross Sections ◽  
Hole Diameter ◽  
Round Hole ◽  
Cyclic Bending ◽  
Number Of Cycles ◽  
The Moment ◽  
Straight Lines ◽  
Bending Failure ◽  
Good Agreement

This paper presents the influence of a redundant round hole in the same direction but different cross sections on the response and failure of round-hole 6061-T6 aluminum alloy tubes subjected to cyclic bending. In this study, round-hole 6061-T6 aluminum alloy tubes with a constant hole diameter of 6 mm were drilled to obtain a redundant round hole in the same hole direction but different cross sections. The experimental results revealed that the moment–curvature relationship exhibited an almost steady loop from the beginning of the first cycle. The redundant round hole showed minimal influence on the moment–curvature relationship. However, the ovalization–curvature relationship demonstrated an asymmetrical, increasing, ratcheting and bow pattern along with the bending cycle, while the redundant round hole showed a significant influence on this relationship. In addition, six groups of round-hole 6061-T6 aluminum alloy tubes were tested, the controlled curvature-number of bending cycles required to ignite failure relationships on double logarithmic coordinates exhibited nonparallel straight lines. Finally, a theoretical model was proposed for simulating the controlled curvature–number of cycles to ignite failure. The simulation result was compared with experimental test data, which showed generally good agreement.

Viscoplastic Collapse of Thin-Walled Tubes Under Cyclic Bending

1998 ◽  
Vol 120 (4) ◽  
pp. 287-290 ◽  
Author(s):  
Wen-Fung Pan ◽  
Yung-Shun Her
Keyword(s):  
Cross Section ◽  
304 Stainless Steel ◽  
Experimental Result ◽  
Metal Tube ◽  
Controlled Experiments ◽  
Cyclic Bending ◽  
Tube Cross Section ◽  
Thin Walled ◽  
Number Of Cycles ◽  
Tubular Specimens

This paper presents the experimental result on the response and stability of thin-walled tubes subjected to cyclic bending with different curvature-rates. The curvature-ovalization measurement apparatus, designed by Pan et al. (1998), was used for conducting the present curvature-controlled experiments on thin-walled tubular specimens of 304 stainless steel. It is observed that the higher the applied curvature-rate, the greater is the degree of hardening of metal tube. However, the ovalization of tube cross-section increases when the applied curvature-rate increases. Furthermore, due to the higher degree of the ovalization of tube cross-section for higher curvature-rates under cyclic bending, the number of cycles to produce buckling is correspondingly reduced.

An Investigation of Cyclic Transient Behavior and Implications on Fatigue Life Estimates

1997 ◽  
Vol 119 (2) ◽  
pp. 161-170 ◽  
Author(s):  
Yanyao Jiang ◽  
Peter Kurath
Keyword(s):  
Stainless Steel ◽  
Fatigue Life ◽  
Cyclic Hardening ◽  
Transient Behavior ◽  
Fatigue Tests ◽  
304 Stainless Steel ◽  
Deformation History ◽  
Life Estimation ◽  
Fatigue Life Estimation ◽  
Track Deformation

Current research focuses on proportional cyclic hardening and non-Massing behaviors. The interaction of these two hardenings can result in the traditionally observed overall softening, hardening or mixed behavior exhibited for fully reversed strain controlled fatigue tests. Proportional experiments were conducted with five materials, 304 stainless steel, normalized 1070 and 1045 steels, and 7075-T6 and 6061-T6 aluminum alloys. All the materials display similar trends, but the 304 stainless steel shows the most pronounced transient behavior and will be discussed in detail. Existing algorithms for this behavior are evaluated in light of the recent experiments, and refinements to the Armstrong-Frederick class of incremental plasticity models are proposed. Modifications implemented are more extensive than the traditional variation of yield stress, and a traditional strain based memory surface is utilized to track deformation history. Implications of the deformation characteristics with regard to fatigue life estimation, especially variable amplitude loading, will be examined. The high-low step loading is utilized to illustrate the effect of transient deformation on fatigue life estimation procedures, and their relationship to the observed and modeled deformation.

Buckling life estimation of circular tubes of different materials under cyclic bending

2010 ◽  
Vol 33 (2) ◽  
pp. 177-189 ◽  
Author(s):  
Kuo‐Long Lee ◽  
Chao‐Yu Hung ◽  
Hao‐Yuan Chang ◽  
Wen‐Fung Pan
Keyword(s):  
Cyclic Bending ◽  
Circular Tubes ◽  
Life Estimation

Prediction of Cutting Forces in Milling Stainless Steels using Chamfered Main Cutting Edge Tool

2005 ◽  
Vol 21 (3) ◽  
pp. 145-155 ◽  
Author(s):  
C.-S. Chang
Keyword(s):  
Stainless Steel ◽  
Cutting Forces ◽  
Steel Plate ◽  
Cutting Edge ◽  
304 Stainless Steel ◽  
Workpiece Material ◽  
Material Force ◽  
Force Data ◽  
Edge Tool ◽  
Good Agreement

AbstractTo study the cutting forces, the carbide tip's surface temperature, and the mechanism of secondary chip and main chip formation of face milling stainless steel with a chamfered main cutting edge has been investigated. Theoretical values of cutting forces were calculated and compared to the experimental results with SUS 304 stainless steel plate as a workpiece material. Force data from these tests were used to estimate the empirical constants of the mechanical model and to verify its prediction capabilities. A comparison of the predicted and measured forces shows good agreement. A preliminary discussion is also made for the design of special tool holders and their geometrical configurations. Next, the tips mounted in the tool holders are ground to a chamfered width and the tool dimensions are measured by using a toolmaker microscope.

Comparative Calculations of TROI TS-2 and TS-3 Steam Explosion Experiments With TEXAS-V

2017 ◽  
Author(s):  
Taehoon Kim ◽  
Sukyoung Pak ◽  
Yongjin Cho
Keyword(s):  
Void Fraction ◽  
Steam Explosion ◽  
Peak Pressure ◽  
Severe Accident ◽  
Experiment Data ◽  
Trigger Time ◽  
Vessel Reactor ◽  
The Moment ◽  
Containment Integrity ◽  
Good Agreement

During a severe accident, contact of the molten corium with the coolant water may cause an energetic steam explosion which is a rapid increase of explosive vaporization by transfer to the water of a significant part of the energy in the corium melt. This steam explosion has been considered as an adverse effect when the water is used to cool the molten corium and could threaten reactor vessel, reactor cavity, containment integrity. In this study, TROI TS-2 and TS-3 experiments as part of the OECD/SERENA-2 project were analyzed with TEXAS-V. Input parameters were based on actual TROI experiment data. In mixing simulations, calculated results were compared to melt front behavior, void fraction in trigger time and other parameters in experiment results. In explosion simulations, corresponding to TROI experiments an external triggering was employed at the moment that melt front reached heights of 0.4 m. Calculated results of peak pressure and impulse at the bottom were compared with TROI experiment results. Melt front behaviors of the melt was different from the experimental results in both TS-2 and TS-3. Void fraction in triggering time in TS-2 was in good agreement with the experiment results and in TS-3 was slightly overestimated. The peak pressure and impulse at bottom were successfully predicted by TEXAS-V. These calculations will allow establishing whether the limitations and differences observed in the simulations of the experiments are important for the reactor case.

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