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1、INTERNATIONAL STANDARD IS0 3385 Third edition 1989-11-15 Flexible cellular polymeric materials - Determination of fatigue by constant-load pounding Matkriaux polym at this point the full force of the indentor shall be supported by the test piece. The indentor shall be free to be lifted in its mounti
2、ng to prevent overloading of the test piece. Means shall be provided whereby at any stroke the time can be controlled during which the full force is exerted by the indentor. This time shall be no more than 25 % of the total duration of each cycle. 4.4 Force measuring device, whereby the load applied
3、 to the test piece by the indentor can be measured. A suitable method consists in mounting the platen upon load cells. NOTE - Where adjustment is manual, the indentor is attached to the lower end of a shaft which passes through a vertical guide above the platen carrying the test piece. Adjustment of
4、 the vertical position of the indentor relative to the platen controls the length of time at any stroke that the full force of the indentor is supported by the test piece. A sug- gested arrangement is shown diagrammatically in figure 1. A suggested method of securing automatic adjustment is shown in
5、 figure 2, whereby the length of time during which the test piece sup- ports the indentor is controlled directly by the time during which the valve is open. 5 Test pieces 5.1 Shape and dimensions Test pieces shall be right parallelepipeds having sides of length 360 mm f 20 mm and a thickness of 50 m
6、m + 2 mm. Tests may also be carried out on components that do not comply with these dimensions subject to agreement between the in- terested parties. 1 -,-,- IS0 3365 : 1969 (El 5.2 Samples showing orientation If the products show an orientation of the cellular structure, the direction in which the
7、indentation is to be carried out shall be agreed upon between the interested parties. Normally, testing is carried out in that direction in which the finished product will be stressed under service conditions. Repeat the whole procedure, from the measurement of the original thickness and hardness in
8、dex at the beginning of this clause, for the two remaining test pieces. 7 Expression of results 7.1 Loss in thickness 5.3 Number Three test pieces shall be tested. 5.4 Conditioning The percentage loss in thickness Ad given by the formula 4 - 4 Ad = 100 x 4 where Test pieces shall not be tested less
9、than 72 h after manufacture unless it can be demonstrated that, at either 16 h or 46 h after manufacture, the compression stress-strain characteristics ob- tained do not differ by more than + IO % from those obtained after 72 h. Testing is permitted at either 16 h or 49 h if, at the selected time, t
10、he above criterion has been satisfied. d, is the original thicknes; d2 is the final thickness. Express the result as the median of the values obtained for the three test pieces. Prior to the test, the test pieces shall be stored for at least 16 h at either 7.2 Loss in hardness 23 OC I!I 2 OC. 50 % +
11、 5 % relative humid 6 Procedure H2 is the final hardness. Express the result as the median of the values obtained for the three test pieces. Measure the thickness d, of one of the test pieces and its hard- ness index as specified in IS0 2439. Place the test piece concentrically under the indentor, a
12、djust the stroke to be equal to the thickness of the test piece and ad- just the relative positions of the indentor and platen until the specified load of 750 N zl 20 N is applied. Adjustment of the indentor mass may be required. NOTE - This method of expressing hardness loss results as absolute rat
13、her than percentage losses has been selected because analysis of experimental data shows that the variability of results is reduced by this method of expression. The commonly used percentage loss is related to the absolute loss by the following formula : Percentage hardness loss = 100 x ffl - H2 HI
14、NOTE - In the case of the manually adjusted arrangement shown in figure 1, the correct setting is achieved when the indentor is just lifted in its mounting. In the case of the arrangement shown in figure 2, these adjustments are automatic. However, slight movement of the in- dentor in its mounting m
15、ay not be clearly visible, but provided that the valve is operated at each stroke, the conditions of the test are satisfied. As the foam softens during the. test, it is necessary, if automatic adjustment is not provided, that the indentor pos- ition be adjusted manually sufficiently frequently to ma
16、intain the above test load of 750 N + 20 N. Run the machine for 60 000 continuous load cycles and then remove the test piece from the machine and allow to rest in an unstrained state for IO,0 min f 05 min. 6 Test report The test report shall include the following information : a) a reference to this
17、 International Standard; b) a description of the material; cl the conditioning used; d) the size and shape of the component tested, if different from the standard test piece; e) the predominant direction of the cellular structure, if any; Remeasure the thickness d2 of the test piece as specified in
18、IS0 2439 and then carry out the measurement of hardness index at 40 % f 1 % indentation as specified in sub-clause 7.2 (method A) of IS0 2439 : 1960, including the preliminary indentation procedure specified in sub-clause 7.1 of that Inter- national Standard, except that the 40 % I g) the median har
19、dness loss after pounding. NOTE - An example of how to express briefly the dynamic fatigue characteristics determined in accordance with this International Stan- dard is as follows: IS0 3385/median percentage thickness loss/median hardness lose. -,-,- IS0 3365 : 1969 (El Adjustable stop lndentor sup
20、port mounting Indentor Platen Figure 1 - Diagrammatic arrangement for manually adjusted machine 3 Fluid reservoir Valve opened momentarily when mounting and platen are closest together, allowing - force to balance out on test piece (operated automatically) I- Non-return valve in piston prevents over
21、loading of test piece , lndentor support mountir lndentor i ATest piece c / Figure 2 - Diagrammatic arrangement for automatically adjusted machine IS0 3365 : 1969 (E) UDC 676.076 : 620.178.3 Descriptors : cellular materials, flexible cellular materials, tests, compression test, fatigue tests. Price based on 4 pages -,-,-