Bestimmung des Verformungs- und Versagensverhaltens von Kunststoffen unter einachsiger Druckbeanspruchung Schlussbericht

The subject is the determination of uniaxial compressive material behaviour by using lubricated cylindrical specimen. The height of the cylinders is 27 mm and their diameter 18 mm. The research was done with two PE, two PP materials and one PMMA. For the machining of the specimens extruded bars of 30 mm diameter have been used for the polyolefins. The specimens PMMA have been machined out of cast PMMA plates of 30 thickness. The materials were: Basell Hostalen GM 5010 T3 black and natural, Basell Novolen PPH 2150, Borealis PE HE 3490-Ls, Borealis PP BA 212E and PMMA Roehm GS 222 transparent. At first the specimen geometry, e.g. the geometry of the machined grooves at both cylinder ends was optimised. For the polyolefins the optimal depth of the grooves was found to be 0,2 mm. The width of the groove rims is 1,5 mm. The use of grooved specimens, where the grooves are filled with silicone grease, was found to induce cracking of the specimens so that correct values of material strength could not be reached. For this material a machined cylinder with greased plane ends is optimal. That means that previous to compressive tests with unknown material it has to be found out which geometry of the specimen ends delivers satisfying results. Another result of the present work is that the determination of the modulus of elasticity under compressive load should be done by the use of plane ended not greased cylinders for all materials. Parallel to the short term compressive tests tensile tests with machined tensile specimens of the same diameter of 18 mm have been performed. It was found that the polyolefins could endure 1,5 to 2,0 times and the PMMA up to 2 times more stress under compression than under tension. Contrary to the tensile behaviour no sign of damage could be found in specimens after they passed on a compressive test. In the last step long term tests like creep and relaxation tests each at 23 C and 40 C were performed with the optimised specimens. After all long term tests were finished the middle portion of the specimens were cut out as 5 mm thick slices. These small plates have been checked under a microscope. No sign of damage like micro cracking, shear lines or the appearance of fibrils was detected. Only cracks beginning from the lubricated ends of the cylinder were found and classified as secondary cracks because their appearance is connected to the applied test method which leads to certain biaxiale load due to the grease and the machined micro structure of the lubricated cylinder ends or the end grooves. Different specimens for te load case uniaxial compression were optimised. The found geometry is ready for the immediate application in the practical work. It could be shown that the materials endure significantly higher stresses without any damage under compression load than under tensile load. Thesefacts oblige to change the up to now usual practice in dimensioning make it necessary to apply results gained with the shown methods.(orig.)SIGLEAvailable from TIB Hannover: F04B1344 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekArbeitsgemeinschaft Industrieller Forschungsvereinigungen 'Otto von Guericke' e.V. (AIF), Koeln (Germany)DEGerman

Beitrag zum Ermuedungsverhalten erdverlegter Kunststoffrohre zur Ableitung von Oberflaechen- und Abwasser im Verkehrswegebau Schlussbericht

For life tests on PVC-U pipes Woehler curves were determined at a constant R-value (R=0.2, 0.4, 0.6). Investigations include the effect of an intermediate tempering at 60 C. The hard- and software applied for the dynamical tests allow not only the record of strengths but at the same time also the record of sample deformation. From the measured hysteresis values the beginning of the damage, e.g. by crack formation, can be derived. Hysteresis values are more sensitive to starting damages than deformation values. Parameters effecting hysteresis and crack formation during test conditions are discussed. The obtained results can be used for the dimensioning of plastic pipes. (WEN)SIGLEAvailable from TIB Hannover: F94B0818 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekArbeitsgemeinschaft Industrieller Forschungsvereinigungen e.V., Koeln (Germany)DEGerman