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The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sat, 04 Jul 2020 09:07:36 GMT2020-07-04T09:07:36ZA self-affine geometrical model of dynamic RT-PMMA fractures: implications for fracture energy measurements
http://hdl.handle.net/10985/9600
A self-affine geometrical model of dynamic RT-PMMA fractures: implications for fracture energy measurements
KOPP, Jean-Benoit; SCHMITTBUHL, Jean; NOEL, Olivier; FOND, Christophe
Profilometric imaging of fracture surfaces of rubber toughened polymer has been performed at two different resolutions (a) at large scales [10 μ\upmu m–25 mm] using an opto-mechanical profilometer and (b) at small scales [0.195 μ\upmu m–0.48 mm] using an interferometric optical microscope. We introduced a self-affine geometrical model using two parameters: the Hurst exponent and the topothesy. We showed that for rubber toughened materials the approximation of the created surface by a mean flat plane leads to a poor estimation of the dynamic fracture energy GIdcG_{Idc}. The description of the created rough fracture surface by a self-affine model is shown to provide a significantly better approximation. A new and original geometrical method is introduced to estimate self-affine parameters: the 3D surface scaling method. Hurst exponents are shown to be unique, χ=0.6±0.1\chi =0.6\pm 0.1 for the different fracture zones and measurement scales. Topothesy ratios indicate a significant difference of fracture surface roughness amplitude depending on the observation resolution when the detrending technique is not correctly introduced.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/96002015-01-01T00:00:00ZKOPP, Jean-BenoitSCHMITTBUHL, JeanNOEL, OlivierFOND, ChristopheProfilometric imaging of fracture surfaces of rubber toughened polymer has been performed at two different resolutions (a) at large scales [10 μ\upmu m–25 mm] using an opto-mechanical profilometer and (b) at small scales [0.195 μ\upmu m–0.48 mm] using an interferometric optical microscope. We introduced a self-affine geometrical model using two parameters: the Hurst exponent and the topothesy. We showed that for rubber toughened materials the approximation of the created surface by a mean flat plane leads to a poor estimation of the dynamic fracture energy GIdcG_{Idc}. The description of the created rough fracture surface by a self-affine model is shown to provide a significantly better approximation. A new and original geometrical method is introduced to estimate self-affine parameters: the 3D surface scaling method. Hurst exponents are shown to be unique, χ=0.6±0.1\chi =0.6\pm 0.1 for the different fracture zones and measurement scales. Topothesy ratios indicate a significant difference of fracture surface roughness amplitude depending on the observation resolution when the detrending technique is not correctly introduced.Rapid crack propagation in PA11: An application to pipe structure
http://hdl.handle.net/10985/17335
Rapid crack propagation in PA11: An application to pipe structure
KOPP, Jean-Benoit; FOND, Christophe; HOCHSTETTER, Gilles
Dynamic fracture mechanism in Polyamide 11 (PA11) material has been described at laboratory scale to access to an intrinsic material parameter. A liquid transportation application is considered with polymer pipes. A preliminary numerical analysis of the rapid crack propagation (RCP) in polymer pipe is firstly realised. Two boundary conditions, imposed displacement or pressure, are numerically investigated. The work of external forces is not negligible for pressurized polymer pipe. A reliable estimate of the dynamic energy release rate GId is in this last case not guaranteed. To limit unwanted structural effects a specific experimental device has been used to ensure a permanent regime of RCP in Pre-Stressed Pipe Specimen (PS2). Experimental dynamic fracture tests are realised with Polyamide 11 PS2. Dynamic instabilities inducing “ring-off” and “snake” mechanisms which could appear during full-scale test are not observed with this new test. A finite element procedure is used to estimate the material toughness GID of PA11. Knowing the crack tip location during RCP inertia effects (i.e. kinetic energy) are quantified. The mean crack tip velocity is observed not to change in PA11 whatever the crack configuration (branching or not). This velocity is known to be the crack branching velocity (≈0.6cR). The average dynamic energy release rate 〈GID〉 is equal to 1.5± 0.1 kJm−2 at the crack branching velocity. The nontrivial fracture surface roughness is observed with a scanning electron microscope.
Mon, 01 Jan 2018 00:00:00 GMThttp://hdl.handle.net/10985/173352018-01-01T00:00:00ZKOPP, Jean-BenoitFOND, ChristopheHOCHSTETTER, GillesDynamic fracture mechanism in Polyamide 11 (PA11) material has been described at laboratory scale to access to an intrinsic material parameter. A liquid transportation application is considered with polymer pipes. A preliminary numerical analysis of the rapid crack propagation (RCP) in polymer pipe is firstly realised. Two boundary conditions, imposed displacement or pressure, are numerically investigated. The work of external forces is not negligible for pressurized polymer pipe. A reliable estimate of the dynamic energy release rate GId is in this last case not guaranteed. To limit unwanted structural effects a specific experimental device has been used to ensure a permanent regime of RCP in Pre-Stressed Pipe Specimen (PS2). Experimental dynamic fracture tests are realised with Polyamide 11 PS2. Dynamic instabilities inducing “ring-off” and “snake” mechanisms which could appear during full-scale test are not observed with this new test. A finite element procedure is used to estimate the material toughness GID of PA11. Knowing the crack tip location during RCP inertia effects (i.e. kinetic energy) are quantified. The mean crack tip velocity is observed not to change in PA11 whatever the crack configuration (branching or not). This velocity is known to be the crack branching velocity (≈0.6cR). The average dynamic energy release rate 〈GID〉 is equal to 1.5± 0.1 kJm−2 at the crack branching velocity. The nontrivial fracture surface roughness is observed with a scanning electron microscope.