1、Dimensions in mm 1 Field of application This standard is applicable to round specimens made of metals, which are subjected to alternate stress through rotating bending. 2 Purpose The rotating bar bending fatigue test is used for determining the fatigue strength behaviour under alternating bending st
2、resses of round specimens when subjected to rotating stress, preferably to determine the fatigue strength under alternating bending stresses. The specimen is subjected purely to alternating stress, i.e. around the mean value 0, between equally large positive and negative stress values. Since the hig
3、hest stresses occur in the surface of the specimen, with this test method the surface finish of the specimen is of particular importance. 3 Concepts For concepts, symbols and general information on procedure and evaluation of the test refer to DIN 50 100. 4 Summary of the method During rotating bar
4、bending fatigue testing, the round specimen is rotated and subjected to a bending moment, causing the stress at every point on the specimen to alter sinusoidally in rhythm with a complete revolution. 5 Designation of the method Designation of the rotating bar bending fatigue test for metallic materi
5、als (A): Test DIN 50 113-A Solesale rights of German Standards (DIN-Normen) are with Beuth Verlag GmbH. Berlin 30 12.89 DIN 50 1 13 Engl. Price group 5 Sales No. 0105 Page 2 DIN 50113 6 Equipment 7 Specimens Rotating bar bending fatigue testing machines which meet the requirements of DIN 51 228and t
6、hegeneral guidelines of DIN 51 220. The most usual stressing arrangement for the two types of specimens according to figure 1 is shown in figure 2. The variation in direct stress in the marginal zone of the specimen in each case is also given schematically in figure 2. As a rule, the test frequencie
7、s used with rotating bar bending fatigue testing machines lie between 50 s-1 and 200 s-1. Attention is drawn to the fact that the test frequency may have an influence on the test result. Figure 1. Examples of rotating bending specimens Figure 2. Example of a stressing arrangement for the two types o
8、f specimen shown in figure 1. F force M bending moment a direct stress in the marginal zone of the specimen Note: Beside the stressing arrangements shown in figure 2, stressing arrangements with a bending moment which increases linearly are also used. The specimens shall have a circular cross sectio
9、n within the measured section. They may be level or indented. Details on the shape and dimensions of the specimen are not specified. They depend on the purpose of the test and on the testing machine available. The dimensions used for determining the test cross section must be measured to the nearest
10、 + 0,01 mm. Two types of specimens commonly used are shown in figure 1. It is pointed out that with differently shaped specimens, areas of material of varying size can be subject to high stress, see figure 2. Results are thereforedependent on the shape and dimensions of the specimen. The condition o
11、f the material and the surface finish of the specimens (surface parameters, e.g. for R, or R, and method of machining) should agree with those of the case of application. It is expressly pointed out that the method and the direction of themachining of the specimen have a decisive influence on the te
12、st results. Care must also be taken to ensure that, prior to and during testing, the surface is not damaged, for example by mechanical or undesired corrosive influences. 8 Procedure 8.1 Stressing The specimen must be mounted in such a way that there is no deformation. Here, the special instructions
13、of the test machine manufacturer must be followed. The test machine is then switched on without the specimen being subjected to stress. Here, steps must be taken to ensure that the specimen is not subjected to any plastic torsional pre-deformation, for instance as a result of forces of gravity, bear
14、ing friction, etc. Once the machine is running, the intended stress shall then be applied without shock, as quickly as possible and in the same way for all tests. 8.2 Temperature of the specimen The temperature of the specimen shall be measured repeatedly during the test. If the specimen are cooled,
15、 the test result can be affected as a result of reactions of the cooling medium with the surface of the specimen. 9 Evaluation The mechanical stress occurring in the marginal zone of the specimen shall be calculated using the formula M bending moment 0 =- = W section modulus (edge stress calculated
16、using the theory of elasticity). The effective stress must be calculated individually for each specimen. The test results shall be suitably represented in graphic form. The stress applied in the test shall be entered on the linearly or logarithmically divided ordinate of the system of coordinates an
17、d the number of load cycles reached until failure shall be entered on the logarithmically divided abscissa. Because of the variation which generally occurs in the number of load cycles to failure reached in the course of equivalent tests, it is recommended that a system of DIN 50113 Page3 test plann
18、ing and evaluation based on static principles be used 1). Results from specimens which have reached the preset limit number of load cycles without failing shall be specially marked, e.g. by an arrow pointing to the right. 10 Test report The test report shall refer to this standard and give the follo
19、wing information: a) details on the specimen: - material (type, pretreatment, dimensions, chemical analysis, parameters of the tensile test) - manufacture (sampling zone and direction, shape and dimeniions of specimen, method of manufacture, type of heat (e.g. lever arm, weight), measuring method (e
20、g. mechanical scale), type of restraint (e.g. cone, clamping restraint), test speed, parameters for setting the testing machine (e.g. scale divisions) C) details on the ambient conditions: - ambient temperature - air humidity - temperature of the specimen during the test, cooling medium if any - an
21、y special ambient conditions d) details on the test result: - fracture or specimen without fracture - position of fracture (in the test area, in the clamping area) - number of fatigue cycles N to fracture or at the end of the test treatment, storage time after heat treatment, stress e) general infor
22、mation: concentration factor, surface parameters 2) - serial number of the test b) details on test procedure: - specimen number - type of stressing (e.g. rectangular moment, triangular moment, - date sinusoidal moment in the test area) - testing station, tester - stress parameters (transverse force,
23、 bending moment, maximum bending stress) 1) It is intended to incorporate these in a revised edition - testing machine of DIN 50 100. (type, designation) with details on load application 2) e.g. in accordance with DIN 4768 Part 1 Standards referred to DIN 4768 Part 1 Determination of the surface rou
24、ghness R, R, and R, with electric stylus instruments; basic data DIN 50 100 Testing of materials; continuous vibration test; definitions; symbols, procedure, evaluation DIN 51 220 Material testing machines; general directions DIN 51 228 Material testing machines; fatigue testing machines; definition
25、s, general requirements Previous editions 1 DIN DVM A 113 = DIN 50 113: 10.34. 12.52 Amendments Compared with the December 1952 ebition, the following amendments have been made: a) Selection and representation of the stressing arrangements have been adapted to IS0 1143. b) With a view to achieving t
26、est results which have greater practical application, it is recommended that the test be carried out with specimens whose surface finish corresponds to that of the application case. c) Repeated measurement of the specimen temperature during the test was prescribed in order to ensure correct evalu- a
27、tion of the test results. d) Direct details about the Wohler method have been omitted. e) In the interests of greater accuracy of the test results, the dimensions of the test cross section of each specimen tested must now be determined. f) It is recommended that the tests be planned and evaluated st
28、atistically. g) The details to be given in the test report were considerably expanded for the purpose of improved documentation. Page 4 DIN 50 113 Explanations This standard was drawn up by Technical Committee NMP 145 “Test methods with alternating stresses for metals“ of Normenausschuss Materialpri
29、ifung (NMP) (Materials Testing Standards Committee). The International Organization for Standardization (ISO) has published the following Internationalstandard: IS0 1143 - 1975 Metals - Rotarrng bar bending fatigue testing The essential differences between IS0 1143 and this standard are the followin
30、g: Compared with DIN 50 113, IS0 1143 contains further representations of stressing arrangements which are not in fact excluded by DIN 50 113, but are not given as examples, because they do not allow for stress of the specimen without transverse force. Results from tests in which, in addition to the
31、 bending moment, transverse forces occur are not directly comparable with results from tests in which no transverse forces occur. The specifications given in IS0 1143 about the diameter of the specimens to be used were not taken over, since they represent too great a restriction. The recommendations
32、 with regard to manufacture of the specimens and machining of the surface have not been taken over from IS0 1143 into this standard, as they involve unusually high expenditure. Instead, this standard specifies that the condition of the material and the surface finish of the specimens shall correspon
33、d to that of the case of application. The surface parameters of the specimens tested (e.g. R, R,) must be stated in the test report together with the method of manufacture. Because of the high test speeds normally used and the consequent heating of the specimens which may arise, repeated measurement of the temperature of the specimen during the test is prescribed. International Patent Classification G 01 N 3/00 3) Obtainable from Beuth Verlag GmbH, Burggrafenstrasse 4-10, 1000 Berlin 30.
