Static and fatigue analysis of notched composite laminates

2016 ◽  
Vol 50 (30) ◽  
pp. 4307-4317 ◽  
Author(s):  
Christos Kassapoglou
Keyword(s):  
Composite Laminates ◽  
Fatigue Loading ◽  
Test Results ◽  
Characteristic Distance ◽  
Hole Edge ◽  
Additional Testing ◽  
Number Of Cycles ◽  
Static Failure ◽  
Cycles To Failure ◽  
Good Agreement

An approach to predict static and fatigue failure of composite laminates with holes is presented. Static failure is predicted when the stress averaged over a characteristic distance is equal to the un-notched failure strength. This averaging distance is determined analytically without the use of additional testing or need for extra material parameters. During fatigue loading, the size of the damage region next to the hole is calculated and the strains at the hole edge are determined. These are used along with the stresses just outside the damage region to determine whether failure starts at the hole edge or the edge of the damage region extends. A previously developed fatigue model based on the cycle-by-cycle probability of failure is used to calculate the number of cycles needed for the residual strain at hole edge or the residual strength at the edge of the damage region to fall below the corresponding applied values. The procedure is repeated until laminate failure. The method is also used to predict cycles to failure for impacted specimens. The predictions are in very good agreement with test results.

Study on the stiffness degradation in concrete continuous beam with externally prestressed CFRP tendons under fatigue loading

2021 ◽  
pp. 136943322199249
Author(s):  
Xing Li ◽  
Jiwen Zhang ◽  
Jun Cheng
Keyword(s):  
Fatigue Life ◽  
Fatigue Loading ◽  
Load Level ◽  
Fiber Reinforced Polymer ◽  
Stiffness Degradation ◽  
Test Results ◽  
Reinforced Polymer ◽  
Continuous Beams ◽  
Practical Engineering ◽  
Good Agreement

This paper presents fatigue behaviors and the stiffness degradation law of concrete continuous beams with external prestressed carbon fiber-reinforced polymer (CFRP) tendons. Three specimens were tested under fatigue loading, and the influence of different load levels on the stiffness degradation and fatigue life were studied, and it was found that the stiffness degradation of three test specimens exhibited a three-stage change rule, namely rapid decrease, stable degradation, and sharp decline, but there are obvious differences in the rate and amplitude of stiffness degradation. The load level has a significant influence on the fatigue life of the test specimens. An analytical model with load level considered was proposed to calculate the residual stiffness and predict the stiffness degradation, which is in good agreement with the test results. The model of stiffness degradation presents a possible solution for practical engineering applications of concrete continuous beams with externally prestressed CFRP tendons subjected to different fatigue loadings.

A New Design Criterion for Wire Rope

1945 ◽  
Vol 12 (1) ◽  
pp. A33-A38 ◽  
Author(s):  
D. C. Drucker ◽  
H. Tachau
Keyword(s):  
Pressure Ratio ◽  
Testing Procedure ◽  
Wire Rope ◽  
Design Criterion ◽  
Test Results ◽  
Families Of Curves ◽  
Pressure Variable ◽  
Number Of Cycles ◽  
Direct Tensile ◽  
Cycles To Failure

Abstract Several previous attempts have been made to analyze existing experimental and field data on wire rope running over sheaves, in order to arrive at a basis of design. It is believed that this paper is the first to indicate that a dimensionless bearing-pressure variable B = 2T/UdD is of prime importance in the proper choice of wire rope. Its significance is evident in the plot of life (number of cycles to failure) against this bearing-pressure ratio B, Fig. 1, which shows a well-defined curve for several ordinary lay 6 × 37 ropes. Also, the scatter in test results for many different ordinary lay ropes of 6 × 19 and 6 × 37 construction, Fig. 2, is less than might be expected from the considerable variation in testing procedure and the wire rope itself. In addition, the average curves, Fig. 3, for ordinary lay ropes of different construction all show similar characteristics and fall within the same range. This closeness of agreement in both shape and magnitude can easily be explained on the basis of the compressive stress between the wires but not on the nominal bending and direct tensile stresses that have in the past been considered the important quantities. Plotting against these conventional variables, either singly or in combination, at best leads to families of curves instead of one only for a given construction, thus requiring more data and leading to conclusions which probably have less physical meaning, Figs. 4 (a, b, c, d).

Low Velocity Impact of a Viscoelastic Beam

1982 ◽  
Vol 104 (2) ◽  
pp. 210-215
Author(s):  
R. E. Llorens ◽  
E. J. McQuillen
Keyword(s):  
Composite Laminates ◽  
Low Velocity Impact ◽  
Viscoelastic Beam ◽  
Test Results ◽  
Transverse Impact ◽  
Low Velocity ◽  
Euler Beam ◽  
Numerical Predictions ◽  
Linear Viscoelastic ◽  
Good Agreement

A theoretical solution for the response of a viscoelastic beam to off-center low speed transverse impact is presented. The flexural model adopted for investigation consists of a uniform Bernoulli-Euler beam whose behavior has been generalized to include a linear viscoelastic constitutive relation for each element of the beam. Further, the beam and rigid impactor are assumed to remain in contact during the resulting motion and a consistent set of initial displacement and velocity distributions is adopted for the beam. The solution method utilizes two Laplace transforms, i.e., one with respect to space and the other with respect to time. Comparison of the numerical predictions of the theoretical model with central impact test results on graphite-epoxy composite laminates indicates a good agreement between theory and experiment.

Fatigue Tests on Aluminum Specimens Subjected to Constant and Random Amplitude Loadings

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Morteza Rahimi Abkenar ◽  
David P. Kihl ◽  
Majid T. Manzari
Keyword(s):  
Fatigue Life ◽  
Aluminum Alloys ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Test Results ◽  
Number Of Cycles ◽  
Mechanical Devices ◽  
Cycles To Failure ◽  
Amplitude Versus ◽  
Weight Structures

Increasing interest in using aluminum as the structural component of light-weight structures, mechanical devices, and ships necessitates further investigations on fatigue life of aluminum alloys. The investigation reported here focuses on characterizing the performance of cruciform-shaped weldments made of 5083 aluminum alloys in thickness of 9.53 mm (3/8 in.) under constant, random, and bilevel amplitude loadings. The results are presented as S/N curves that show cyclic stress amplitude versus the number of cycles to failure. Statistical procedures show good agreements between test results and predicted fatigue life of aluminum weldments. Moreover, the results are compared to the results obtained from previous experiments on aluminum specimens with thicknesses of 12.7 mm (1/2 in.) and 6.35 mm (1/4 in.).

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.

Design of welded structures working under random loading

2002 ◽  
Vol 216 (2) ◽  
pp. 191-201 ◽  
Author(s):  
R Kouta ◽  
M Gungad ◽  
D Play
Keyword(s):  
Fatigue Life ◽  
Statistical Analysis ◽  
Design Method ◽  
Test Results ◽  
Random Loading ◽  
Matrix Representations ◽  
Fatigue Lifetime ◽  
Random Loads ◽  
Number Of Cycles ◽  
Cycles To Failure

This paper presents a design method for prediciting the fatigue life of T-joint assemblies loaded by random loads, based on a statistical analysis of tests. This sduty was on the correclation between the types of loading observed in practive and test results obtained for fatigue life determination. The work follows three steps: analysis tof the statistical distributions of random loads that illustrate extremen value from Markov matrix representations; statistical analysis of lifetimes obtained when the specimens are sbumitted to random loads defined earlier; design of a set of endurance curves [stress-number of cycles to failure ( S-N) curves], called ‘random’ S-N curves. These SN curves. These S-N curves are shifted compared with that obtained under sinusoidal loading. Random S-N curve positions in the S-N plane are obtimized depending on the lifetime able to take into account the damege due to the small cycles that are often present in actual loading. The use of random S-N curves for fatigue life calculations gives results matching with theral fatigue lifetime obtained with a T-joint assembly of a bogie chassis used for railway applications. Different analyses show the robustness of the proposed approach.

The mechanical behavior of poly(lactic acid) unreinforced and nanocomposite films subjected to monotonic and fatigue loading conditions

2011 ◽  
Vol 45 (26) ◽  
pp. 2717-2726 ◽  
Author(s):  
Rodney D. Averett ◽  
Mary L. Realff ◽  
Karl Jacob ◽  
Mukerrem Cakmak ◽  
Baris Yalcin
Keyword(s):  
Lactic Acid ◽  
Fatigue Resistance ◽  
Failure Time ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Nanocomposite Films ◽  
Poly Lactic Acid ◽  
Loading Conditions ◽  
Number Of Cycles ◽  
Cycles To Failure

The mechanical and fatigue behavior of neat poly(lactic acid) (PLA) films and PLA films reinforced with 5 wt% nanoclay particles has been examined using various analytical procedures. The results showed that for the films tested in this study, PLA-5 wt% samples were more susceptible to crazing at the same maximum fatigue stress as the neat PLA samples, as evidenced by results from light transmission experiments. Optical microscopy results confirmed this observation. In addition, under fatigue loading conditions, the neat PLA samples displayed almost the same fatigue resistance (number of cycles to failure) at 3 and 30 Hz, while the PLA-5 wt% samples showed a shift in the number of cycles to failure to higher values at a frequency of 30 Hz. Using the linear regression curves from the S– N data (stress vs. number of cycles to failure), time-to-failure curves were generated to show the difference between the neat PLA and PLA-5 wt% samples when tested at frequencies of 3 and 30 Hz. Based on these results, it is known that the nanoclay particles served to increase the fatigue resistance at the higher frequency of 30 Hz, when compared to the neat PLA sample.

Ratcheting, Wrinkling and Collapse of Tubes Induced by Axial Cycling Under Internal Pressure

2011 ◽  
Author(s):  
Rong Jiao ◽  
Stelios Kyriakides
Keyword(s):  
Cyclic Loading ◽  
Internal Pressure ◽  
Kinematic Hardening ◽  
Cyclic Plasticity ◽  
Combined Loads ◽  
Offshore Pipeline ◽  
Number Of Cycles ◽  
Cyclic Plasticity Model ◽  
Cycles To Failure ◽  
Good Agreement

A buried offshore pipeline is essentially axially constrained by the soil cover. Heating by the passage of hot oil at high pressure can plastically deform it. The deformation involves expansion of the diameter, which for thinner pipes can be accompanied by axisymmetric wrinkling. During a lifetime of 20 or more years, lines experience regular startup and shutdown cycles. This study examines how this cycling affects wrinkling and the hoop expansion of such lines. A set of experiments on super-duplex tubes with D/t of 28.5 was conducted using the following idealized cyclic loading history. A tube is first pressurized and then compressed into the plastic range to a level that initiates wrinkling. It is then cycled under stress control about a compressive mean stress while the pressure is kept constant. The combined loads cause simultaneous ratcheting in the hoop and axial directions as well as a gradual growth of the wrinkles. At some stage the amplitude of the wrinkles starts to grow exponentially with the number of cycles N leading to localization and collapse. The rate of ratcheting and the number of cycles to failure depend on the initial compressive pre-strain, the internal pressure and the stress cycle parameters. The problem is modeled as a shell with initial axisymmetric imperfections. A challenge in the simulations is that the cyclic plasticity model that is used must be capable of capturing correctly the type of biaxial material ratcheting that develops. The Dafalias-Popov two-surface nonlinear kinematic hardening model, enhanced and suitably calibrated is shown to capture the prevalent ratcheting deformations correctly leading to predictions that are in good agreement with the experimental results. The model is then used to evaluate the ratcheting behavior of pipes under thermal-pressure cyclic loading histories seen by buried pipelines.

scholarly journals Assessment of Validity of Selected Criteria of Fatigue Life Prediction

Materials ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2310 ◽  
Author(s):  
Krzysztof Kluger ◽  
Roland Pawliczek
Keyword(s):  
Fatigue Life ◽  
Fatigue Loading ◽  
Mean Value ◽  
Material Behavior ◽  
Density Parameter ◽  
Test Results ◽  
Critical Plane Approach ◽  
Calculation Results ◽  
The Mean ◽  
Number Of Cycles

The paper reports on the results of a comparison involving mathematical models applied for fatigue life calculations where the mean load value is taken into account. Several models based on the critical plane approach and energy density parameter were tested and analyzed. A fatigue test results for three types of materials are presented in this paper. The specimens were subjected to bending, torsion and a combination of bending with torsion with mean value of the load. Analysis of the calculation results show that the best fatigue life estimations are obtained by using models that are sensitive to the changes of material behavior under fatigue loading in relation to the specified number of cycles of the load.

Prediction of the Scatter of Crack Initiation under High Cycle Fatigue

2007 ◽  
Vol 345-346 ◽  
pp. 363-366 ◽  
Author(s):  
Stephane Osterstock ◽  
Christian F. Robertson ◽  
Maxime Sauzay ◽  
Suzanne Degallaix ◽  
Veronique Aubin
Keyword(s):  
Fatigue Crack ◽  
Crack Initiation ◽  
High Cycle Fatigue ◽  
Fatigue Crack Initiation ◽  
Fatigue Loading ◽  
Anisotropic Elasticity ◽  
Dislocation Dynamics ◽  
Cycle Fatigue ◽  
Number Of Cycles ◽  
Cycles To Failure

Under fatigue loading, the number of cycles to failure and its associated scatter increase when the loading level decreases. The High-Cycle Fatigue (HCF) regime is thus characterized by a large scatter in the number of cycles to failure [1]. Cracks initiation represents an important part of the lifetime of the structures. A stochastic method is used to study the fatigue crack initiation prediction in the 316L austenitic stainless steel. The present work proposes to show that this scatter can be attributed to the random orientation of individual grains, which influences the crack initiation localization. The stresses in grains are determined by finite element computations (FEM [2]), using a configuration representative of a polycrystalline aggregate. This approach takes into account the crystallographic orientations of the grains in the aggregate as well as the deformation incompatibilities between neighbouring grains due to crystalline anisotropic elasticity and elasticplasticity [3]. Then, the scatter of the number of cycles to crack initiation is derived from the FEM stress fields using two fatigue crack initiation criteria: an usual one, Mura’s criterion [4] and a more recent one [5], based on Discrete Dislocation Dynamics (DDD) simulations and taking into account plastic slips, cross slip and stress tensor components.

Sign in / Sign up

Export Citation Format

Share Document