2 edition of Smooth specimen simulation of fatigue behavior of notches found in the catalog.
Smooth specimen simulation of fatigue behavior of notches
Richard M. Wetzel
Written in English
|Statement||by R. M. Wetzel.|
|The Physical Object|
|Number of Pages||15|
|LC Control Number||a 68007035|
Recent experiments on the fatigue behavior of slightly notched (K t = ) Ti-6Al-4V specimens immersed in solution at various concentrations of methanol, however, have shown that, in the presence of dynamic loads applied (R = ), the effect of corrosion appears to be significant, even for very high amounts of water in solution . environments. The uniaxial fatigue resistance of smooth and notched specimens made of Ti –6Al 4V has been extensively investigated in the recent literature–64 The role played by different environments (air and NaCl solution) on fatigue limit of pure tension fatigue on Ti –6Al 4V V-notched specimens (with a notch.
Smooth Specimen Representation of Material at the Critical Zone Cyclic Softening and Relaxation of Mean Stress under Neuber Control (Ti-8Al-lMo-lV, K f = ), (12) Cumulative Fatigue Damage Procedure Recorded Data from a Smooth Specimen Simulation of the Local Stress- Strain Behavior of a Notch . Most engineering components and structures contain stress concentrations, such as notches. The state of stress at such concentrations is typically multiaxial due to the notch geometry, and/or multiaxiality of the loading. Significant portions of the fatigue life of notched members are usually spent in crack initiation (crack formation and microscopic growth) and macroscopic crack growth.
Derivation of Effective Strain-Life Data, Crack Closure Parameters and Effective Crack Growth Data from Smooth Specimen Fatigue Tests Small crack growth from notches under variable amplitude loading requires that crack opening stress be followed on a cycle by cycle basis and taken into account in making fatigue life predictions. The paper contains the results of fatigue tests of smooth and notched specimens made of 10HNAP (SJ2G1W) subjected to proportional cyclic loading with use of mean values stress. The results obtained for specimens under bending, torsion and one combination of bending with torsion for four mean values have been compared.
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Although the mean depth of notches of the specimen A is μm, which is of the same order as the depth of a notch, 30 μm, in singly notched specimens, the fatigue limit for specimen A is % higher than that for the singly notched specimen. This is because the fatigue notch effect for specimen A is reduced because of interference.
Interestingly, the fatigue behavior of a notched specimen is not necessarily determined only by the cyclic stress at the notch (which is higher than that experienced by the rest of the specimen).
In many materials, a notched specimen will survive significantly longer than an unnotched (smooth) specimen with the same cyclic notch stress evenly Cited by: 9. Further, several methods based on Neuber's rule allow a smooth cylindrical specimen to be used to simulate the stress-strain behavior of the notch root metal.
The fatigue life of the smooth specimen is shown to furnish a satisfactory estimate of the fatigue life of the notched member, and the stress-strain plot of the smooth specimen is useful Cited by: In a similar manner we can conceive the prediction of fatigue behavior in a notched structural element on the basis of known cyclic behavior in a simpler smooth specimen.
Recent advances in this. Stadnick, S.J. and Morrow, JoDean, “Techniques for Smooth Specimen Simulation of the Fatigue Behavior of Notched Members”, Testing for Prediction of Material Performance in Structures and Components, ASTM STP, pp – CrossRef Google ScholarCited by: the fatigue notch factor, K f.
Notched fatigue strength not only depends on the stress concentration factor, but also on other factors such as the notch radius, material strength, and mean and alternating stress levels. The ratio of smooth to net notched fatigue strengths, based on the ratio of alternating stresses is called K f.
K f. Goal: Trying to analyze the fatigue of Notches. Kf vs Kt for different root radius rho - with associated fracture mechanics parameter, K or del K threshold and smooth specimen endurance life. Troshchenko, V. Kalenchuk, and L.
Khamaza, “Automatic system of local physical experimentation to determine the fatigue properties of metals,” in: Process Automation in Investigations of the Mechanical Properties of Materials and the Strength of Structural Elements [in Russian], IPPAN Ukrainian SSR, Kiev (). COMMON FATIGUE TEST SPECIMENS Specimens shown have been used for obtaining fatigue crack growthdata.
In all cases a thin slit, notch, or groove with a very small root radius is machined into the specimen. Fatigue crack growth testing is covered in Section Mean Stresses at Notches. ε σ ε. elastic. plastic Nominal Notch. Nominal Notch. Stadnick and Morrow, “Techniques for Smooth Specimen Simulation of Fatigue Behavior of Notched Members” ASTM STP, Smooth & Notched.
The basic mechanical properties of smooth and notched specimens were detected. The strength of notched specimens are applied to compare with Whitney-Nuismer stress criterion.
For average stress criteria, the theoretical value is in good agreement with experimental data. Fatigue testing experiments and computer-simulations have been conducted for notched specimens of two cutting-tool materials: high speed steel (M42 HSS) and cemented carbide composite (WCCo).
The effects of varying loads and notches on the fatigue lives of M42 HSS and WCCo, including a comparative study of the fatigue behavior of the two. systematic fatigue tests done in the ’s. S-N Curve plots the diagram of amplitude of nominal stress as a function of number of cycles to failure for un-notched (smooth) specimens.
Mathematical description of the material S-N curve: A B S a= σ a= AN f-B σa – applied alternating stress A – constant, value of σa at one cycle. specimens tested were with various notch geometries and dimensions. By using Stress Life approach, the two types cylindrical specimens smooth (reference) and notched have been investigated and fatigue life analysis the are obtained experimentally and by use FEA.
The fatigue notch factor, k. f, is determined at a given number of completely reversed cycles (typically 6. or 7) to crack initiation and is given as: unnotched notched.
f f f. k (2) where is the fatigue strength of the unnotched specimen and is the fatigue strength of the notched specimen. The difference between. kt and kf for a. The fatigue strength of the 7N01 aluminum alloy after electropolishing is almost unchanged compared with the original specimen.
The fatigue behavior of the 7N01 aluminum alloy after prefabricated side straight through the notch deviated from the theoretical smooth specimen law and long crack propagation law in which is a 'shortage effect. A method is presented for predicting the fatigue life of notched members from smooth specimen fatigue data.
Inelastic behavior of the material at the notch root is treated using Neuber's rule which states that the theoretical stress concentration factor is equal to the geometric mean of the actual stress and strain concentration factors. This provides indices of equal fatigue damage for.
From the literature review, it is observed that pre-fatigue damage behavior exhibits a strong influence on the remnant tensile properties. Very few studies have been reported on the influence of pre-HCF damage on both smooth and notch tensile behavior.
Also, the influence of damage on post necking behavior still creates a research gap. An elastic plastic fracture mechanics solution for short fatigue cracks in smooth and notched specimens is presented which admits plasticity by replacing the conventional stress term with a strain term and accounts for the propagation of very short cracks by the introduction of an effective crack length which is equal to the actual length increased by length l 0, the length constant l 0 is.
A single-edge-notched specimen was used to observe the propagation behavior of relatively long through thickness cracks. The notch depth was mm. The total pre-crack length including the notch depth was and mm.
Fatigue Tests Fatigue tests were performed in a servo-hydraulic fatigue. For most materials, the reduction in fatigue lifetime between a notched and a smooth specimen is linearly related to the elastic stress concentration, resulting in parallel S-N behavior.
Since both geometries would be hypothesized to create a proportional reduction to a smooth specimen, their relationship should also be parallel. Fatigue life of notched specimens is calculated using the fatigue life obtained from the experiments for smooth specimens (reference) and by use Numerical method (FEA).The fatigue experiments were carried out at room temperature, applying a fully reversed cyclic load with the frequency of 50 Hz and mean stress equal to zero (R= -1), on a.A general definition of the notch strength reduction factor is the ratio of fatigue strength of smooth specimen to fatigue strength of the notched specimen in the same numbers of cycles and the same experimental test conditions : n s k f = (1) where s and n are the fatigue strength of smooth and notched specimens, respectively.