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ASTM D ASTM G Designation: E? A number in parentheses indicates the year of last reapproval. A superscript epsilon? Scope 1. This practice is limited to the fatigue testing of axial unnotched and notched specimens subjected to a constant amplitude, periodic forcing function in air at room temperature.
This practice is not intended for application in axial fatigue tests of components or parts. Terminology 3. The results may also be used as a guide for the selection of metallic materials for service under conditions of repeated direct stress. To do so would require the control or balance of what are often deemed nuisance variables; for example, hardness, cleanliness, grain size, composition, directionality, surface residual stress, surface?
Thus, when embarking on a program of this nature it is essential to de? All material variables, testing information, and procedures used should be reported so that correlation and reproducibility of results may be attempted in a fashion that is considered reasonably good current test practice. Specimen Design 5. Referenced Documents 2. Current edition approved Nov. Published November Originally approved in DOI: However, the design should meet certain general criteria outlined below: 5.
The acceptable ratio of the areas test section to grip section to ensure a test section failure is dependent on the specimen gripping method. Threaded end specimens may prove difficult to align and failure often initiates at these stress concentrations when testing in the life regime of interest in this practice.
A caveat is given regarding the gage section with sharp edges that is, square or rectangular cross section since these are inherent weaknesses because the slip of the grains at sharp edges is not con?
Because of this, a circular cross section may be preferred if material form lends itself to this con? The size of the gripped end relative to the gage section, and the blend radius from gage section into the grip section, may cause premature failure particularly if fretting occurs in the grip section or if the radius is too small. Readers are referred to Ref 1 should this occur. Surfaces intended to be parallel and straight should be in a manner consistent with 8.
NOTE 2—Measurements of dimensions presume smooth surface? In the case of surfaces that are not smooth, due to the fact that some surface treatment or condition is being studied, the dimensions should be measured as above and the average, maximum, and minimum values reported.
To ensure test section failure, the grip cross-sectional area should be at least 1. The blending? The test section length should be approximately two to three times the test section diameter. For tests run in compression, the length of the test section should be approximately two times the test section diameter to minimize buckling.
The reduced section length should be greater than three times the minimum test section diameter. Otherwise, the same dimensional relationships should apply, as in the case of the specimens described in 5. In view of this, no maximum ratio of area grip to test section should apply.
The value of 1. Otherwise, the sections may be either of two types: 5. The ratio of specimen test section width to thickness should be between two and six, and the reduced area should preferably be between 0. The test section length should be approximately two to three times the test section width of the specimen. For specimens that are less than 0. For example, specimen alignment is of utmost importance and the procedure outlined in Practice E would be advantageous.
Also, Refs , although they pertain to straincontrolled testing, may prove of interest since they deal with sheet specimens approximately 0. The area restrictions should be the same as for the specimen described in 5. Also, speci? Specimen Preparation 6. Improper methods of preparation can greatly bias the test results. In view of this fact, the method of preparation should be agreed upon prior to the beginning of the test program by both the originator and the user of the fatigue data to be generated.
Since specimen preparation can strongly in? Appendix X1 presents an example of a machining procedure that has been employed on some metals in an attempt to minimize the variability of machining and heat treatment upon fatigue life. Regardless of the machining, grinding, or polishing method used, the? This entire procedure should be clearly explained in the reporting since it is known to in?
One exception may be where these parameters are under study. Fillet undercutting can be readily determined by inspection. Assurance that surface residual stresses are minimized can be achieved by careful control of the machining procedures.
It is advisable to determine these surface residual stresses with X-ray diffraction peak shift or similar techniques, and that the value of the surface residual stress be reported along with the direction of determination that is, longitudinal, transverse, radial, and so forth. The storage medium should generally be removed before testing using appropriate solvents, if necessary, without adverse effects upon the life of the specimens.
Obvious abnormalities, such as cracks, machining marks, gouges, undercuts, and so forth, are not acceptable. Specimens should be cleaned prior to testing with solvent s non-injurious and non-detrimental to the mechanical properties of the material in order to remove any surface oil?
Equipment Characteristics 7. The test forces should be monitored continuously in the early stage of the test and periodically, thereafter, to ensure that the desired force cycle is maintained.
The varying stress amplitude, as determined by a suitable dynamic veri? In the typical regime of 10? It is beyond the scope of Practice E to extrapolate beyond this range or to extend this assumption to other materials systems that may be viscoelastic or viscoplastic at ambient test temperatures and within the frequency regime mentioned. As a cautionary note, should localized yielding occur, signi?
Procedure 8. For most conventional grips, good alignment must come about from very careful attention to design detail. Every effort should be made to prevent the occurrence of misalignment, either due to twist rotation of the grips , or to a displacement in their axes of symmetry.
It is important that the accuracy of alignment be kept consistent from specimen to specimen. For cylindrical specimens, alignment should be checked by means of a trial test specimen with longitudinal strain gages placed at four equidistant locations around the minimum diameter.
The trial test specimen should be turned about its axis, installed, and checked for each of four orientations within the? For rectangular cross section specimens, alignment should be checked by placing longitudinal strain gages on either side of the trial specimen at the minimum width location.
The trial specimen should be rotated about its longitudinal axis, installed and checked in both orientations within the? For specimens having a uniform gage length, it is advisable to place a similar set of gages at two or three axial positions within the gage section. One set of strain gages should be placed at the center of the gage length to detect misalignment that causes relative rotation of the specimen ends about axes perpendicular to the specimen axis.
The lower the bending stresses strains , the more repeatable the test results will be from specimen to specimen. Test Termination 9. Failure may be de? In reporting the results, state the criterion selected for de?
Report Since however, the environment can greatly in? However, regardless of the nature of the forcing function, it should be reported sine, ramp, saw tooth, etc. As a conservative general measure, this procedure is recommended unless: 1 the experimental objective is to evaluate another given surface condition or, 2 it is known that the material under evaluation is relatively insensitive to surface condition.
Ra, in the longitudinal direction. NOTE X1. This is a particular danger in soft materials wherein material can be smeared over tool marks, thereby creating a potentially undesirable in?
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ASTM E466 Load Controlled Constant Amplitude Fatigue Tests of Metals
ASTM D ASTM G Designation: E? A number in parentheses indicates the year of last reapproval. A superscript epsilon? Scope 1.
ASTM E466 – Force Controller Constant Amplitude Axial Fatigue Testing of Metallic Materials
ASTM E describes the determination of the fatigue strength of metallic materials in the fatigue regime where the strains are predominately elastic, both upon initial loading and throughout the test. This test method is applicable for axial unnotched and notched specimens subjected to constant amplitude, periodic force. By following this standard, the effect of variations in material, geometry, surface condition, and stress, on the fatigue resistance of metallic materials subjected to direct stress for a large number of cycles is studied. The results are suitable for application to design only when the specimen test conditions realistically simulate service conditions. Forgot your password? Work with us to find the right equipment for your ASTM standard.