June, 19-22, 2013 Biograd, Croatia CIM2013
POSSIBILITY OF QUALITY CONTROL OF NON-STANDARD
POLYMER PRODUCTS WITH COMPRESSION TESTING
Tihana Kostadin, Andreja Mihalić, Tomislav Crnković
T. Kostadin, mag.ing.mech., Karlovac University of Applied Sciences, I. Meštrovića 10, 47000 Karlovac
A. Mihalić, bacc.ing.mech., Karlovac University of Applied Sciences, I. Meštrovića 10, 47000 Karlovac
T. Crnković, bacc.ing.mech., Karlovac University of Applied Sciences, I. Meštrovića 10, 47000 Karlovac
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June, 19-22, 2013 Biograd, Croatia CIM2013
Keywords: compression test, quality assurance, adaptation of test equipment.
Abstract
In order to ensure quality and meet the quality criteria of finished products of polymeric crates for glass packaging, it is necessary to conduct compression test according to DIN EN 22782 (HR EN ISO 12048). Plastic crate as a finished product is a non-standard test object for compression testing. Compression tests were performed by using the own construction and making an adequate apparatus by adapting the existing test equipment. Based on tests performed in accordance with the above standard and the results obtained conclusions about the quality of the product are drawn. The test results provide the required quality of the product, and therefore harmless application of crates filled with glass packaging during storage and transport.
1. INTRODUCTION
Since the existing test equipment does not use an appropriate apparatus for performing a pressure test of non-standard polymeric crates for glass packaging, meaning that it has not been prepared for such a test object, a construction was created and necessary parts were made in order to perform testing.
The position shown in Figure 1. is made of material Č.5432 (30CrNiMo8), while the position shown in Figure 2. is made of material Č.0361
( S235JRG2 ) and subsequently bluing was carried out for surface protection of the positions to ensure tribological effects during application.
It is important to emphasize the appropriate selection of measuring positions shown in Figure 2. because these dimensions are adapted to the dimensions of the test object.
After creating an appropriate apparatus compression testing is conducted in accordance with the standard DIN EN 22782 (HRN EN ISO 12048). Seven polymeric crates for glass packaging were tested to obtain appropriate features of finished articles concerning resistance to stresses during storage and transport.
It is important to measure the load at which it will be deformed or broken in order to be able to predict and avoid possible dangers in operation.
The crates to be tested are made of polypropylene, a polymeric material belonging to the group of plastomers.
When plastomers heat up, they soften, and when they cool to (room) temperature, they harden again. Plastomer molecules are linear, and material properties are based on the structure; mechanical properties are among the most important ones. Compression test falls into tests where load is static and short. [1,2,3]
Polypropylene (PP) is a linear hydrocarbon polymer, which belongs to the group of saturated polymers. It is one of the most common materials for the production of plastic items. It is used for the production of various items, from fiber production, to the production of consumer goods.
Polypropylene is a crystalline plastomer, and its melting point is 175 ° C. The meaning of the name crystalline plastomer is that apart from the crystalline phase it also contains the amorphous phase. Hence the name, which means that these materials are similar to crystalline ones, and the proportion of crystalline phase is expressed by the degree of crystallinity. As a rule, widely applicable crystalline plastomers rarely reach a high degree of crystallization.
Crystalline materials are generally opaque. They excel through toughness and better chemical stability of amorphous plastomers. [4]
Compression testing of polymeric crates should show whether the test results provide the required product quality.
Also, during testing adaptation of the own designed and manufactured apparatus is tested, because it is a major prerequisite for the successful implementation of the tests.
2. EXPERIMENT
2.1. CONSTRUCTION AND CREATION OF THE APPARATUS
Tests are performed at the Laboratory of the Karlovac University of Applied Sciences on the Shimadzu AG-X testing machine. The testing machine was adapted by creating an apparatus or plates between which a polymeric crate is placed for compression testing. Figure 1. shows position 1 (material 30CrNiMo8), and Figure 2. shows position 2 (material S235JRG2).
Figure 1. Position 1 [5]
Figure 2. Position 2 [5]
Figure 3. shows the complete schematic drawing of the apparatus.
Figure 3. Schematic drawing of the apparatus [5]
Apparatus are assembly of two plates, two plates holders and two pins.
Dimensions of plates holders are shown on Figure 1. Pins are inserted through holes on plates holders to ensure both plates parallel and fixed on strenght testing machine during compression testing.
Dimensions of plates ( 435x335x12 [mm] ) are shown on Figure 2. and adapted to the dimensions of the test object.
2.2 COMPRESSION TESTING
Test object - a polymeric crate - is placed between two plates (made according the description in the previous section) on the testing apparatus. The plates must be flat, their dimensions should cover the entire surface of the test object and be sufficiently rigid (includes deformability of less than 1 mm on reaching 75% of maximum load).
One of the plates must be fixed to the device (bottom plate), while the second plate (upper plate) is used for continuous pressure loads while increasing the contact pressure on the test apparatus. [6]
Figures 4. (a,b,c) show the adaptation of the test equipment for compression testing of polymeric crates.
Figure 4. (a,b.c) Adaptation of the test equipment for compression testing [5]
Testing is done by compression loading polymeric crates for glass packaging with a continuous load speed of 10 mm / min.
Maximum load without deformability to be achieved is 25 000 N, while preload is 10% of the maximum load (2500 N).
Characteristic points that testing must meet are:
- Deformability during load of 7000 N must not be greater than 0,5%;
- Deformability during load of 12000 N must not be greater than 1%. [6]
Dimensions of the test object polymeric crate are: 400x300x300 [mm].
3. TEST RESULTS
3.1. TEST RESULTS FOR COMPRESSION TESTING OF POLYMERIC CRATE
Results for compression testing of 7 polymeric crates for glass packaging are illustrated in Figures 5 to 11.
Figure 5. Results for compression testing - polymeric crate 1 [5]
Figure 6. Results for compression testing - crate 2 [5]
Figure 7. Results for compression testing - crate 3 [5]
Figure 8. Results for compression testing - crate 4 [5]
Figure 9. Results for compression testing - crate 5 [5]
Figure 10. Results for compression testing - crate 6 [5]
Figure 11. Results for compression testing - crate 7 [5]
Figure 5. to Figure 11. show diagrams of performed compression testing on 7 polymeric crates. In diagrams x-axis is stroke of polymeric crates during the testing and y-axis is the value of force during the testing.
The value of maximum force shown in diagrams is also value where the first deformation on polymeric crate is visible.
Characteristic points shown in diagrams are :
- Deformability during load of 7000 N,
- Deformability during load of 12 000 N,
- Deformability during load of 25 000 N and
- Maximum force with maximum stroke.
Tables 1. (a,b) show the results of all seven of polymeric crates for glass packaging, while Table 2. shows the mean test values for individual parameters.
Table 1a. Test results for polymeric crates (N1,N2,N3) [5]
UNITNAME / N1 / N2 / N3
Max Force
[ N ] / 35 260 / 35 787 / 35 613
Max Stroke Strain
[ % ] / 4,13 / 4,02 / 3,81
Stroke Strain
(Force 7000 N)
[ % ] / 0,38 / 0,39 / 0,38
Stroke Strain
(Force 12 000 N)
[ % ] / 0,77 / 0,78 / 0,77
Stroke Strain
(Force 25 000 N)
[ % ] / 1,94 / 1,91 / 1,90
Table 1b. Test results for polymeric crates (N4,N5,N6,N7) [5]
UNITNAME / N4 / N5 / N6 / N7
Max Force
[ N ] / 37 503 / 35 835 / 36 403 / 37 766
Max Stroke Strain
[ % ] / 4,09 / 4,13 / 4,11 / 4,01
Stroke Strain
(Force 7000 N)
[ % ] / 0,36 / 0,39 / 0,38 / 0,36
Stroke Strain
(Force
12 000 N)
[ % ] / 0,73 / 0,78 / 0,76 / 0,73
Stroke Strain
(Force
25 000 N)
[ % ] / 1,80 / 1,92 / 1,87 / 1,788
Table 2. Mean test values [5]
Max Force[ N ] / 36 309,57
Max Stroke Strain
[ % ] / 4,04
Stroke Strain
( Force 7000 N )
[ % ] / 0,38
Stroke Strain
( Force 12 000 N )
[ % ] / 0,76
Stroke Strain
( Force 25 000 N )
[ % ] / 1,87
Tables 1. (a,b) show values of maximum forces [N] for all tested polymeric crates and stroke strain [%] during load of 7000 N, 12000 N, 25000 N and during of maximum force.
Table 2. shows the mean test values of:
- Maximum force,
- Stroke strain during load maximum force,
- Stroke strain during load of 7000 N, 12 000 N and 25 000 N.
3.2 ANALYSIS OF RESULTS
The results show that polymeric crates for glass packaging meet the quality criteria required by standard DIN EN 22782 (EN ISO 12048).
The results show that the maximum force of all seven tests objects lies far above the required 25000 N.
Also, deformability during load of 7000 N is less than the required 0,5%, while the deformability during load of 12000 N is less than the required 1% of all 7 tested crates.
Tests also showed that the own designed and constructed apparatus (plates between which a test object is placed) can withstand much greater load (more than 75% of maximum force) without visible strain, which confirms that the device worked well and that it can be used further in of these types of tests.
4. CONCLUSION
After creating an appropriate apparatus compression testing is conducted in accordance with the standard DIN EN 22782 (HRN EN ISO 12048).
After the test it was concluded that the own constructed apparatus fully meets the quality criteria, and it can be used for conducting tests on the testing machine.
All tested polymeric crates for glass packaging are according to standard.
5. REFERENCES
[1] Filetin, T., Kovačiček, F., Indof, J., Svojstva i primjena materijala, FSB Zagreb, Zagreb 2002.
[2] M. Franz: Mehanička svojstva materijala, Sveučilište u Zagrebu, Fakultet strojarstva i brodogradnje Zagreb, Zagreb 1998.
[3] N. Sonički: Mehanička svojstva materijala, Veleučilište u Karlovcu, Karlovac 2011.
[4] Rogić, A., Čatić, I., Godec, D., Polimeri i polimerne tvorevine, Društvo za plastiku i gumu, Zagreb 2008.
[5] Documentation made by Karlovac University of Applied Sciences.
[6] Standard DIN EN 22782 (HRN EN ISO 12048).
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