scholarly journals Elaboration of the Equipment and Technology for Cutting Rolled Round Bars and Pipes with the Cyclic Circular Bending Method

2021 ◽  
Vol 346 ◽  
pp. 01011
Author(s):  
Aleksej Antimonov ◽  
Sergej Poljanskij ◽  
Nadezhda Pushkareva
Keyword(s):  
Experimental Data ◽  
Low Cycle Fatigue ◽  
Continuous Process ◽  
Comparative Assessment ◽  
Strength Analysis ◽  
Cyclic Loads ◽  
Cycle Fatigue ◽  
Significant Difference ◽  
Theoretical Assessment ◽  
Good Agreement

A brief overview of methods for cutting round bars and pipes is presented, their main advantages, disadvantages and field of application are considered. It is proposed to use the effect of fatigue fracture for round bars and pipes breaking. The task is to study this process under the action of cyclic loads. The possibility of applying the known provisions of calculating theory of strength analysis for low-cycle fatigue for this process is tested. A comparative assessment of theoretical and experimental data is given and their significant difference is established. New calculated dependences are proposed, which are in good agreement with the experimental data. A theoretical assessment of the productivity of the process of round bars and pipes breaking by the method of cyclic circular bending was carried out using new results and various options for the design of a device for breaking were considered with an analysis of the features of their operation. Based on the results of the analysis, a variant of the device for the implementation of a continuous process of breaking the pointed ends of thick-walled fuel pipes during drawing in coils and a diagram of the mechanism for breaking the ends of the pipe with its supply from the coil were selected. Samples of pipes obtained by brittle cyclic bending are presented.

An Energy-Based Approach to Determine the Fatigue Strength and Ductility Parameters for Life Assessment of Turbine Materials

2015 ◽  
Vol 137 (7) ◽  
Author(s):  
M.-H. Shen ◽  
Sajedur R. Akanda
Keyword(s):  
Experimental Data ◽  
Fatigue Strength ◽  
High Cycle Fatigue ◽  
Low Cycle Fatigue ◽  
Turbine Rotor ◽  
Life Assessment ◽  
Cycle Fatigue ◽  
Strength Parameters ◽  
Strength And Ductility ◽  
Good Agreement

An energy-based framework is developed to determine the fatigue strength parameters of the Basquin equation and the fatigue ductility parameters of the Manson–Coffin equation to predict high cycle fatigue (HCF) and low cycle fatigue (LCF) life of a steam turbine rotor base and weld materials. The proposed framework is based on assessing the complete energy necessary to cause fatigue failure of a material. This energy is considered as a fundamental material property and is known as the fatigue toughness. From the fatigue toughness and the experimentally determined fatigue lives at two different stress amplitudes, the cyclic parameters of the Ramberg–Osgood constitutive equation that describes the hysteresis stress–strain loop of a cycle are determined. Next, the coefficients and the exponents of the Basquin and the Manson–Coffin equations are computed from the fatigue toughness and the cyclic parameters of a material. The predicted fatigue life obtained from the present energy-based framework is found to be in a good agreement with the experimental data.

Features of the kinetics of cyclic elastoplastic deformation diagrams at dwells in cycles and superimposition of variable stresses on them

2020 ◽  
Vol 86 (12) ◽  
pp. 46-53
Author(s):  
M. M. Gadenin
Keyword(s):  
Experimental Data ◽  
Elastoplastic Deformation ◽  
Low Cycle Fatigue ◽  
Cycle Fatigue ◽  
Loading Cycle ◽  
Additional Variable ◽  
Dynamic Creep ◽  
Variable Stresses ◽  
Kinetics Of ◽  
Deformation Diagrams

The goal of the study is determination of the regularities of changes in cyclic strains and related deformation diagrams attributed to the existence of time dwells in the loading modes and imposition of additional variable stresses on them. Analysis of the obtained experimental data on the kinetics of cyclic elastoplastic deformation diagrams and their parameters revealed that in contrast to regular cyclic loading (equal in stresses), additional deformations of static and dynamic creep are developed. The results of the studys are especially relevant for assessing the cyclic strength of unique extremely loaded objects of technology, including nuclear power equipment, units of aviation and space systems, etc. The experiments were carried out on the samples of austenitic stainless steel under low-cycle loading and high temperatures of testing. Static and dynamic creep deformations arising under those loading conditions promote an increase in the range of cyclic plastic strain in each loading cycle and also stimulate an increase in the range of elastoplastic strain due to active cyclic deformation. At the same time the existence of dwells on extrema of stresses in cycles without imposition of additional variable stresses on them most strongly affects the growth of plastic strain ranges in cycles. Imposition of additional variable stresses on dwells also results in the development of creep strains, but their growth turns out to be somewhat less than in the presence of dwells without stresses imposed. The diagrams of cyclic deformation obtained in the experiments are approximated by power dependences, their kinetics being described in terms of the number of loading cycles using corresponding temperature-time functions. At the same time, it is shown that increase in the cyclic plastic deformation for cycles with dwells and imposition of additional variable stresses on them decreases low cycle fatigue life compared to regular loading without dwells at the same stress amplitudes, moreover, the higher the values of static and dynamic creep, the greater decrease in low-cycle fatigue life. This conclusion results from experimental data and analysis of conditions of damage accumulation for the considered forms of the loading cycle using the deformation criterion of reaching the limit state leading to fracture.

The Revised Universal Slope Method to Predict the Low-Cycle Fatigue Lives of Elbow and Tee Pipes

2017 ◽  
Vol 139 (5) ◽  
Author(s):  
Hiun Nagamori ◽  
Koji Takahashi
Keyword(s):  
Experimental Data ◽  
Internal Pressure ◽  
Low Cycle Fatigue ◽  
Experimental Studies ◽  
High Accuracy ◽  
Universal Method ◽  
Cycle Fatigue ◽  
Element Analysis ◽  
Slope Method ◽  
Stress States

The stress states of elbow and tee pipes are complex and different from those of straight pipes. The low-cycle fatigue lives of elbows and tees cannot be predicted by Manson's universal slope method; however, a revised universal method proposed by Takahashi et al. was able to predict with high accuracy the low-cycle fatigue lives of elbows under combined cyclic bending and internal pressure. The objective of this study was to confirm the validity of the revised universal slope method for the prediction of low-cycle fatigue behaviors of elbows and tees of various shapes and dimensions under conditions of in-plane bending and internal pressure. Finite element analysis (FEA) was carried out to simulate the low-cycle fatigue behaviors observed in previous experimental studies of elbows and tees. The low-cycle fatigue behaviors, such as the area of crack initiation, the direction of crack growth, and the fatigue lives, obtained by the analysis were compared with previously obtained experimental data. Based on this comparison, the revised universal slope method was found to accurately predict the low-cycle fatigue behaviors of elbows and tees under internal pressure conditions regardless of differences in shape and dimensions.

A Study on the Low Cycle Fatigue Behavior of the Steel for Shipbuilding Industry

2005 ◽  
Vol 297-300 ◽  
pp. 10-15 ◽  
Author(s):  
Kyung Su Kim ◽  
Byung Ok Kim ◽  
Young Kwan Kim ◽  
Chang Hwan Lee ◽  
Sung Won Lee
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Published Data ◽  
Cycle Fatigue ◽  
Maritime Industry ◽  
Shipbuilding Industry ◽  
Design Procedures ◽  
Calculation Results ◽  
Good Agreement

Recently, most of fatigue cracks in ship structures are reported within a few years after delivery. This type of fatigue characteristics cannot be explained adequately by the S-N curve based on high cycle fatigue. Calculation results under critical loading conditions reveal that stress magnitude higher than three times the yield stress occurs at some critical locations. It shows the fatigue cracks are related to low cycle fatigue. But the existing recommended design procedures in maritime industry do not properly cover low cycle fatigue problems. This work represents the first step in an effort to develop a design code that addresses low cycle fatigue problems. Low cycle fatigue test for uniform round specimen made of base/weld metal and for cruciform welded joint are carried out under constant amplitude alternating load, controlled by strain. Strain-cycle curves for the base metal and weld joints show good agreement with published data as well as some code recommended design curves.

The Residual Life Prediction of High Temperature Low Cycle Fatigue of 30CrMnSiA Steel

2014 ◽  
Vol 633-634 ◽  
pp. 184-187 ◽  
Author(s):  
Guo Dong Gao ◽  
Wen Xiao Zhang ◽  
Wang Zheng
Keyword(s):  
High Temperature ◽  
Life Prediction ◽  
Residual Life ◽  
Low Cycle Fatigue ◽  
Rbf Neural Network ◽  
Cycle Fatigue ◽  
Mechanical Fatigue ◽  
Steel Base ◽  
Network Method ◽  
Good Agreement

The analysis of the residual life of high temperature low cycle fatigue of 30CrMnSiA steel plays important roles in improving security and avoiding accidents. In this paper, the RBF neural network method is used to predict the residual life of high temperature low cycle fatigue of 30CrMnSiA steel base on data from the thermo-mechanical fatigue test. The feasibility of the method is proved by a practice example, and the learning results are in good agreement with the experimental data.

Comparison of Ni-Steel Dissimilar Joints for Coke Drum External Weld Repairs Based on Isothermal Low-Cycle Fatigue Tests

2021 ◽  
Author(s):  
Shutong Zhang ◽  
Sebastian Romo ◽  
Rafael Arthur Giorjao ◽  
Jorge Penso ◽  
Haixia Guo ◽  
...  
Keyword(s):  
Experimental Data ◽  
Base Metal ◽  
Low Cycle Fatigue ◽  
Cyclic Hardening ◽  
Fatigue Tests ◽  
Cycle Fatigue ◽  
Alloy 625 ◽  
Weld Joints ◽  
Nickel Base ◽  
Filler Metals

Abstract Low-cycle fatigue failure has been widely accepted as the key mechanism causing damages of coke drums during cyclic thermal-mechanical loadings. Common damages of coke drums known as bulging and cracking are associated with accumulative plasticity caused by thermal and mechanical strains. External repairs using temper-bead welding techniques are implemented to repair welds in the damaged areas of coke drums, which provide structural support to the vessels. Compared with matching filler metals, Ni-base fillers including alloy 625 and alloy 182 are compatible with both low-alloy steel base metal and internal clads in terms of weldability and thermal expansion. However, the differences of yield strengths and cyclic hardening behaviors of nickel-base alloys from base metals compromise the fatigue resistances of weld joints. In this study, alloy 182 and alloy 625 repair coupons were evaluated and compared based on isothermal low-cycle fatigue tests. Low-cycle fatigue behaviors of both weld metals and 1.25Cr-0.5Mo base metal were measured at 1.0%, 1.5% and 2.0% strain amplitudes. Test results indicate both nickel-base filler metals exhibit overmatching strength over the base metal due to cyclic hardening. Low-cycle fatigue tests of Heat Affected zone (HAZ) samples show the failures of alloy 625 weld joints occur in the base metal, while the failures of alloy 182 weld joints occur along the fusion boundary. The observations show strength mismatch and fatigue resistance are the key factors to determine failure locations of the joints. In addition, cyclic hardening coefficients based on kinematic hardening model were extracted from experimental data to simulate the cyclic behaviors of the weld joints. Finite element simulation results were shown to be consistent with experimental data at stabilized cycles. Cyclic behaviors of weld metal and base metal within a weld transition sample were calculated based on the numerical model.

Low Cycle Fatigue Study of 63Sn-37Pb Solder under Torsional Cyclic Loading

2013 ◽  
Vol 785-786 ◽  
pp. 72-75
Author(s):  
Hong Qiang Guo
Keyword(s):  
Experimental Data ◽  
Low Cycle Fatigue ◽  
Constant Strain Rate ◽  
Fatigue Tests ◽  
Stress And Strain ◽  
Cycle Fatigue ◽  
Fatigue Lifetime ◽  
Torsional Fatigue ◽  
Relationship Of ◽  
The Relationship

In this paper, the torsional fatigue tests under angle control at the constant strain rate of 5×10-3/s were conducted on 63Sn–37Pb solder over a range of . The relationship of stress and strain for the 63Sn–37Pb solder was investigated. The number of cycle with loading decrease of 25% was thought as the fatigue lifetime. The parameters of Coffin-Manson equation were determined based on the experimental data.

Modeling the Low Cycle Fatigue in Copper Single Crystal: Multiscale Dislocation Dynamics Simulations

2013 ◽  
Vol 1535 ◽  
Author(s):  
Micheal Kattoura ◽  
Mutasem Shehadeh
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Loading ◽  
Dislocation Dynamics ◽  
Half Cycle ◽  
Cycle Fatigue ◽  
Micro Structure ◽  
Copper Single Crystals ◽  
Number Of Cycles ◽  
Dynamics Simulations ◽  
Good Agreement

ABSTRACTMultiscale dislocation dynamics plasticity (MDDP) model is used to investigate the evolution of dislocation microstructure in copper single crystals subjected to low cycle fatigue loading. Half cycle total plastic strain simulations are carried out at strain amplitudes ranging from 1×10-3 to 8×10-3. The initial hardening is investigated and the micro-structural cause behind it is presented. In addition, the loading history is presented and the effect of the initial micro-structure and dislocation distribution on the hardening behavior is studied. In addition, the evolution of the microstructures is examined. In depth analyses of the dislocation microstructures show that: 1) dislocation planes that are parallel and very close to each other are formed, 2) these walls contain dipoles that keep on zipping and unzipping during the first few cycles until they reach some stable zipping configuration. We can see that the hardening rate decreases with the increase of the number of cycles where we have large hardening rate in the first cycles then we reach to somehow constant stress. Our results are qualitatively in good agreement with recent experimental results of low cycle fatigue deformation.

Low Cycle Fatigue Strength of X65 Pipeline Girth Welds

2004 ◽  
Author(s):  
Koji Gotoh ◽  
Stig Berge
Keyword(s):  
Low Cycle Fatigue ◽  
Cyclic Strain ◽  
Test Series ◽  
Cyclic Loads ◽  
Plastic Strains ◽  
Maximum Strain ◽  
Cycle Fatigue ◽  
Fatigue Design ◽  
Large Water ◽  
Girth Welds

During pipe laying at large water depth using S-lay over a stinger, the pipe may be subjected to reversed plastic strains which could lead to low cycle fatigue failure. X65 pipeline girth welds with wall thickness 22mm were tested in cyclic strain control. Undermatched and overmatched welds were tested. Two types of cyclic strain programs were applied. In the first test series the welds were subjected to a tensile-tensile cyclic strain, simulating pipe going over the stinger, to validate that a pipe going over a stinger would not violate criteria for low cycle fatigue design. In the second test series, the specimens were initially pre-strained to 2% and subsequently fatigue-cycled with a maximum strain of 2% to obtain design criteria for a pipe laying stationary over the stinger for a period of time, subjected to cyclic loads due to waves. The results are presented in terms of Δε–N curves, with proposed design curves for the two types of welds.

Sign in / Sign up

Export Citation Format

Share Document