1、GM DAEWOO Auto & Technology EDS Engineering, GM DAEWOO Auto & Technology Standards TEST METHOD DETERMINING THE FLEXURAL STRENGTH OF PLASTICS EDS-T-7518 ISSUED DATE: 1995. 09. 06 REVISED DATE: 2006. 06. 19 VERSION: 5 EDS-T-7518TEST METHOD DETERMINING THE FLEXURAL STRENGTH OF PLASTICS PAGE: 1/4 ISSUED
2、 DATE: 1995. 09. 06 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology 1. SCOPE This standard is used to determine the strength and deformation characteristics of plastic test specimens when flexural loads are applied on plastic test specimens. 2. DEFINITION 2.1. Flexural stress: The
3、quotient of the bending moment in the test specimen at its center at any moment of the test divided by the moment of resistance before the test. 2.2. Flexural strength: Flexural stress at the maximum load. 2.3. Three-point loading flexural test: The bar rests on two supports and is loaded by means o
4、f a loading nose midway between the supports (see Fig 1). 3. APPARATUS 3.1. Flexural Testing Machine It shall be capable of steadily maintaining the test speed up to (50010)mm/min and furnished with force-extension meter. Jigs for bending tests shall be easily mounted to and separated form it. 3.2.
5、Loading Noses and Supports The radius of the nose or noses and supports shall be at least 3.2mm for all specimens as shown in Fig 1 and Fig 2. For specimens 3.2mm or greater in depth, the radius of the supports may be up to 1.5 times the specimen depth and the radius of the loading noses may be up t
6、o 4 times the specimen depth. 3.2.1. Test data have shown that the loading nose and support dimensions can influence the flexural properties values. Fig 1. Loading Noises and Supports Diagram Three-point Loading EDS-T-7518TEST METHOD DETERMINING THE FLEXURAL STRENGTH OF PLASTICS PAGE: 2/4 ISSUED DAT
7、E: 1995. 09. 06 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology 3.3. Micro Meter Micro Meter capable of measuring thickness of specimens 0.03mm. 4. TEST SPECIMENS 4.1. Preparation of Test Specimen Preparation of Test Specimen depend on the product being tested and will be based on
8、the information in the standards for the product concerned. The test specimen may either be manufactured direct, i.e. by extrusion or injection moulding or by machining. All surfaces and edges must be free from damage and defects so as to exclude the possibility of notch effects. If flash marks occu
9、r when the test specimen is produced, these should be removed, whilst avoiding any damage to the surface. All such work shall be carried out in the longitudinal direction of the test specimen. If it is likely that the product is anisotropic, test specimens should be taken both parallel to and perpen
10、dicular to the expected direction of the anisotropy. 4.2. Shape and Dimensions of Test Specimens Unless the dimension of the test specimen is reported in the EDS material spec., it is defined as follow. 4.2.1. Three-point loading flexural Test Dimensions of test specimens for various support span-to
11、-depth ratios are shown in Table 1. The recommended specimen for molding materials(thermoplastics and thermosets) is (12712.73.2)mm tested flatwise on a support span, resulting in a support span-to-depth ratio of 16. Thicker specimens should be avoided if they exhibit significant shrink marks or bub
12、bles when molded. 4.3. Number of Test Specimens Unless otherwise specified, the test results of 3 pieces are reported without maximum value and minimum value, after 5 pieces are tested. 5. TEST SPEED 5.1. Unless the test speed of the material is recorded in the EDS material spec., it is defined as t
13、he clause 5.2 5.2. In case that Material that break at comparatively small deflections, where strain rate is 0.01mm/mmmin, test speed is applied according to specified test speed in Table 1, Table 2 or Table 3. In case that Material that undergo large deflections during testing, where strain rate is
14、 0.1mm/mmmin, multiply these values by 10. EDS-T-7518TEST METHOD DETERMINING THE FLEXURAL STRENGTH OF PLASTICS PAGE: 3/4 ISSUED DATE: 1995. 09. 06 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology Table 1. Test specimen dimensions and test speed for Three-point loading Ratio between
15、distance of supports(L) and specimen depth(d) (L/d) 16 32 40 60 Nominal Specimen Depth (mm) Specimen Width (mm) Specimen Length (mm) L (mm) Test Speed (mm/min) SpecimenLength(mm) L (mm) Test Speed (mm/min)SpecimenLength(mm) L (mm) Test Speed (mm/min) SpecimenLength (mm) L (mm) Test Speed (mm/min)0.8
16、 25 50 16 0.5 50 25 1.3 60 30 2.0 60 48 4.8 1.6 25 50 25 0.8 80 50 2.8 90 60 4.3 124 95 9.4 2.4 25 60 40 1.0 100 80 4.1 120 95 6.4 185 143 14.2 3.2 25 80 50 1.0 130 100 5.3 180 130 8. 247 190 18.8 4.8 13 100 80 2.0 191 150 8.1 240 191 12.7 372 286 28.4 6.4 13 130 100 2.8 250 200 10.9 330 250 17.0 49
17、5 381 37.8 9.6 13 191 150 4.1 380 300 16.3 480 380 25.4 744 572 56.8 12.7 13 250 200 5.3 495 410 21.6 640 510 34.0 991 762 76.2 19.1 19 380 300 8.1 740 610 32.5 940 760 50.8 1486 1143 114 25.4 25 495 410 10.9 990 810 43.4 1240 1020 67.8 1981 1524 152 6. CONDITIONING 6.1. For initial sample approval
18、and arbitration purpose, the minimum time period between vulgarization and testing shall be 7 days. For routine quality control purpose, the period shall be 3 days. 6.2. Before tests, test pieces shall be conditioned at a temperature of 232K and a relative humidity of (506)% for minimum 16 hours, af
19、ter drying at 702.5K for 3 hours. 7. PROCEDURE 7.1. After measuring the detailed dimensions of the test specimen at 3 or more points, get the numerical average of measured values. 7.2. Select the test speed and distance between two supports that fit the sample dimensions by referring to Table 1. 7.3
20、. After mounting the jig onto the test equipment, put a test specimen on it, operate the equipment at the selected speed and record the maximum force when the test piece is bent. 7.4. Apply the load to the specimen until the specimen is broken. If no break has occurred in a specimen by the time the
21、maximum strain has reached 5%, discontinue the test. EDS-T-7518TEST METHOD DETERMINING THE FLEXURAL STRENGTH OF PLASTICS PAGE: 4/4 ISSUED DATE: 1995. 09. 06 REVISED DATE: 2006. 06. 19 VERSION: 5 GM DAEWOO Auto & Technology 8. EVALUATION 8.1. Flexural strength, (Kg/cm2) 2max2bdL3F =Where. Fmax. = Max
22、imum force (kgf) L = Distance between supports (cm) b = Width of test specimen (cm) d = Depth of test specimen (cm) 9. CODE SYSTEM The flexural strength is indicated as follows in drawings and material specifications. Flexural strength to EDS-T-7518 2.8 300kgf/cm2Requirements Test Speed Test method
23、Designation 10. DEVIATIONS Deviations from the requirements of this specification or other additional requirements shall have been agreed upon and shall be specified on the relevant component drawings, test specifications material specifications, etc., and shall be indicated on all test certificates, reports, etc. 11. REFERENCES DIN 53 452 Flexural test ASTM D790 Standard test methods for flexural properties of plastic and electrical insulating materials
