scholarly journals Evaluation of fatigue failure probability in a block loading sequence through the transformation of mean value in constant amplitude conditions

2018 ◽  
Author(s):  
Łukasz Blacha
Keyword(s):  
Fatigue Failure ◽  
Failure Probability ◽  
Mean Value ◽  
Constant Amplitude ◽  
Block Loading ◽  
Loading Sequence

scholarly journals Investigation of Changes in Fatigue Damage Caused by Mean Load under Block Loading Conditions

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2738
Author(s):  
Roland Pawliczek ◽  
Tadeusz Lagoda
Keyword(s):  
Fatigue Life ◽  
Fatigue Damage ◽  
Strain Curve ◽  
Mean Value ◽  
Fatigue Properties ◽  
Stress Strain ◽  
Reference Case ◽  
Block Loading ◽  
The Mean ◽  
Mean Strain

The literature in the area of material fatigue indicates that the fatigue properties may change with the number of cycles. Researchers recommend taking this into account in fatigue life calculation algorithms. The results of simulation research presented in this paper relate to an algorithm for estimating the fatigue life of specimens subjected to block loading with a nonzero mean value. The problem of block loads using a novel calculation model is presented in this paper. The model takes into account the change in stress–strain curve parameters caused by mean strain. Simulation tests were performed for generated triangular waveforms of strains, where load blocks with changed mean strain values were applied. During the analysis, the degree of fatigue damage was compared. The results of calculations obtained for standard values of stress–strain parameters (for symmetric loads) and those determined, taking into account changes in the curve parameters, are compared and presented in this paper. It is shown that by neglecting the effect of the mean strain value on the K′ and n′ parameters and by considering only the parameters of the cyclic deformation curve for εm = 0 (symmetric loads), the ratio of the total degree of fatigue damage varies from 10% for εa = 0.2% to 3.5% for εa = 0.6%. The largest differences in the calculation for ratios of the partial degrees of fatigue damage were observed in relation to the reference case for the sequence of block n3, where εm = 0.4%. The simulation results show that higher mean strains change the properties of the material, and in such cases, it is necessary to take into account the influence of the mean value on the material response under block loads.

The Fatigue Properties of the M27 Higher Strength Bolt in the Grid Structure with Bolted Spherical Joints

2016 ◽  
Vol 851 ◽  
pp. 775-779
Author(s):  
Chao Zhang ◽  
Hong Gang Lei ◽  
Shao Jie Tian ◽  
Xu Yang
Keyword(s):  
Finite Element ◽  
Fatigue Failure ◽  
Fatigue Testing ◽  
Testing Machine ◽  
Fatigue Properties ◽  
Metallographic Analysis ◽  
Constant Amplitude ◽  
Grid Structure ◽  
Finite Element Software ◽  
Loading Device

Under the suspended crane loading, the key to the fatigue of the grid structure with bolt-sphere joints is the fatigue of the higher strength bolt. By now, there are not any research reports about the fatigue properties of M27 higher strength bolt at home and abroad. With the aid of the fatigue-testing machine and the loading device, this paper will have 8 constant amplitude fatigue experiments on test-piece, and will get the S-N curve of the higher strength bolt. With the aid of the metallographic analysis, this paper studies the mechanism and influencing factors of the fatigue failure; and with the aid of the finite element software ABQUAS, it analyzes and gets the stress concentration factor of the M27 higher strength bolt, and verifies the position of the fatigue failure.

scholarly journals Failure Probability Analysis of Interlayer Sliding Belts of Gravity Dams Under Seismic Load

2014 ◽  
Vol 8 (1) ◽  
pp. 85-91 ◽  
Author(s):  
Qiang Xu ◽  
Jian-Yun Chen ◽  
Chunfeng Zhao ◽  
Jing Li ◽  
Hongyuan Yue
Keyword(s):  
Failure Probability ◽  
Mean Value ◽  
Seismic Load ◽  
Mean Square ◽  
Mean Square Deviation ◽  
Concrete Gravity Dam ◽  
Gravity Dams ◽  
The Mean ◽  
Improved Model ◽  
Pseudo Excitation

In this paper, an improved model is presented for analysis of failure probability of the interlayer sliding belts under seismic loads. Firstly, using the theory of the Markov chain, the relation between failure probabilities of specified interlayer sliding belts and elements in this interlayer sliding belt is deduced. Then, the failure function is proposed according to the destructive characteristic of concrete, the pseudo excitation method is utilized in order to obtain the probability distribution of element stresses in specified interlayer sliding belts, and the improved response surface method based on weighted regression is used to calculate the failure probability of elements in specified interlayer sliding belts. Finally, an algorithm is established to calculate the failure probability of the specified interlayer sliding belts. In this paper, the mean value and variance of the tensile strength of elements are changed when interlayer sliding belt is developed. The numerical results show that the conditional failure probability in specified interlayer sliding belts at the head of the dam tends to decrease. However, the tendency of conditional failure probability in the other specified interlayer sliding belts is complicated. And the interlayer sliding belt at head of the concrete gravity dam is the most dangerous. In addition, the tendencies of the mean value and mean square deviation of stresses in different specified interlayer sliding belts are similar. The mean value of stress in different specified interlayer sliding belts tends to decrease but the tendency of mean square deviation changes from decrease to increase. The range of the mean value and the mean square deviation of stress in specified interlayer sliding belts at the heel of the dam is the greatest of all.

scholarly journals Experimental Study on Constant-Amplitude Fatigue Performance of Weld Toe in Steel Tube of Welded Hollow Spherical Joints in Grid Structures

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Jian-li Zhang ◽  
Hong-gang Lei ◽  
Shi-hong Jin
Keyword(s):  
Experimental Study ◽  
Fatigue Failure ◽  
Design Method ◽  
Testing Machine ◽  
Steel Tube ◽  
Load Test ◽  
Fatigue Performance ◽  
Constant Amplitude ◽  
Fatigue Design ◽  
Weld Toe

The grid structure with welded hollow spherical joints (WHSJs) is widely used in industrial buildings with suspended cranes. Cyclic loadings generated by the suspended cranes could result in the fatigue failure of WHSJs. However, a corresponding fatigue design method has not been established. This paper presents an experimental study on the fatigue performance of the weld toe in the steel tube of WHSJs under axial force. Stress distribution on the joint’s surface was obtained by the static load test. By using the MTS fatigue testing machine, a constant-amplitude fatigue test was performed on the full-scale joint specimens. Twenty effective test data were obtained and fitted to a fatigue S-N curve by the least squares method. The corresponding fatigue design method for allowable stress amplitude was established. The mechanism of fatigue failure at the joint was investigated through microscopic analysis using scanning electron microscopy. The results of this paper can be potentially used as a basis for revising specifications and to promote the practical application of grid structures with WHSJs.

Constant Amplitude Fatigue Calculative Method of Welded Hollow Spherical Joint with Cross-Board in Steel Plate-Type Grid Structure

2012 ◽  
Vol 166-169 ◽  
pp. 180-186
Author(s):  
Jin Feng Jiao ◽  
Hong Gang Lei ◽  
Han Wu ◽  
Yong Liu
Keyword(s):  
Fatigue Failure ◽  
Stress Amplitude ◽  
Fatigue Curve ◽  
Use Of Self ◽  
Spherical Joint ◽  
Constant Amplitude ◽  
Grid Structure ◽  
Structural Fatigue ◽  
Plate Type ◽  
Welded Hollow Spherical Joint

The fatigue of grid structures with welded hollow spherical joint under suspending cranes is an issue in both academic and engineering fields at home and abroad. The structural fatigue is mainly caused by the fatigue failure of welded hollow spherical joint with cross-board. In this paper, 16 specimens categorized in KQ-4、KQ-5 and KQ-7were tested stably and efficiently under constant amplitude stress by use of self-designed loading equipment. The testing results show that the form and mechanism of fatigue failure were clarified elementarily. A fatigue curve of welded hollow spherical joint with cross-board, S-N curve, was suggested in this paper based on the statistic regression analysis of the 16 testing results. The constant amplitude fatigue calculation method was established for welded hollow spherical joint with cross-board in grid structure with welded hollow spherical joint by use of allowable stress amplitude method.

Effects of External Loads on the Reliability of Welded Pipe with Circumferential Crack

2007 ◽  
Vol 353-358 ◽  
pp. 2513-2516
Author(s):  
Bo Lin He ◽  
Ying Xia Yu ◽  
Li Xing Huo ◽  
Yu Feng Zhang
Keyword(s):  
Finite Element ◽  
Failure Probability ◽  
Surface Crack ◽  
Safety Assessment ◽  
Bending Moment ◽  
Mean Value ◽  
Stochastic Finite Element ◽  
Inner Pressure ◽  
The Mean ◽  
Welded Pipe

The reliability of welded pressure pipe with circumferential surface crack was calculated by using 3-D stochastic finite element method. This method has overcome the shortcomings of conservative results in safety assessment with deterministic fracture mechanics method. The calculation of reliability was based on 3-D elastic-plastic stochastic finite element program which was developed by ourselves. The effects of variables such as bending moment, the inner pressure on the structure reliability were discussed. The calculation results indicate that the bending moment has great effect on the reliability of the welded pipe, and the inner pressure has little effect on the reliability of the welded pipe if the inner pressure is less than 10MPa. If the mean value of the inner pressure changed from 0.5MPa to 30MPa, the failure probability will changes from 10-6 to 10-2. The bending moment also has great effect on the reliability. When the mean value of moment is changed from10000 Nm to 15000 Nm, the failure probability of the welded pipe increases dramatically for the same inner pressure. Irrespective of the changing of moment, the pipe has higher reliability if the inner pressure is less than 6 MPa. The method has put forward a new way for safety assessment of welded pipe with circumferential surface crack.

Damage accumulation in quasi-isotropic graphite/epoxy laminates under constant-amplitude fatigue and block loading

1998 ◽  
Vol 58 (9) ◽  
pp. 1535-1547 ◽  
Author(s):  
Jonathan Bartley-Cho ◽  
Seung Gyu Lim ◽  
H.Thomas Hahn ◽  
Peter Shyprykevich
Keyword(s):  
Damage Accumulation ◽  
Constant Amplitude ◽  
Block Loading ◽  
Isotropic Graphite
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