A 2D isothermal finite element simulation of the injection stretch-blow molding (ISBM) process for polyethylene terephthalate (PET) containers has been developed through the commercial finite element package ABA-QUS/standard. In this work, the blowing air to inflate the PET preform was modeled through two different approaches: a direct pressure input (as measured in the blowing machine) and a constant mass flow rate input (based on a pressure-volume-time relationship). The results from these two approaches were validated against free blow and free stretch-blow experiments, which were instrumented and monitored through highspeed video. Results show that simulation using a constant mass flow rate approach gave a better prediction of volume vs. time curve and preform shape evolution when compared with the direct pressure approach and hence is more appropriate in modeling the preblowing stage in the injection stretch-blow molding process.
Picqué et alMechanical behaviour of iron oxide scale 2
SummaryThe paper addresses the identification of constitutive parameters of thick, brittle layers on metal substrates. Application is to the iron oxide behaviour during hot rolling processes of steel, where oxide scale breaking and embedding is one of the major causes of surface defects. Contact management of a FEM software has been adapted in order to address the transitions corresponding to transverse oxide fracture, along with two other mechanisms, namely delamination and interfacial stick / slip. It is applied to the hot strip rolling process to show pre-bite cracking and its consequences ("microextrusion" of the metal). To approximate the stress state prevailing at roll bite entry, the four-point Hot Bending Test (4PHBT) has been selected for the measurement of oxide properties. Oxidation is made in-situ in the test rig under conditions similar to a Hot Strip Mill (HSM) environment. Comparison of load-deflection curves for oxidized and nonoxidized samples allows to determine the mechanical properties of the oxide. Above a critical temperature T c -around 700°C, but depending on strain rate -the oxide is ductile (with a very narrow plastic strain range, p < 10 -2 ), Elastic-Viscoplastic (EVP) constitutive parameters are identified numerically. Below T c , brittleness is manifested by an array of transverse, through-thickness cracks. Acoustic Emission (AE) has been used to help detect the onset of fracture, while numerical simulation gives the critical fracture stress at the corresponding point of the load-deflection curve. Results for four low carbon steel grades are compared.
International audienceA 2-D isothermal finite element simulation of the injection stretch-blow moulding (ISBM) process for polyethylene terephthalate (PET) containers has been developed via the commercial finite element package ABAQUS/standard. In this work, the blowing air to inflate the PET preform was modelled via two different approaches; a direct pressure input (as measured in the blowing machine) and a constant mass flow rate input (based on a Pressure-Volume-time relationship). These two methods were tested with a simplified stretch blow moulding process where a preform was blown with and without a stretch rod in free air (no mould). The results clearly show that simulation with a constant mass flow rate as input gave an excellent prediction of volume vs. time curve and preform shape evolution when compared with the direct pressure approach. In addition to this, rapid inflation of the PET preform (∼0.03s) was found to occur in the direct pressure approach which was not observed in reality. This result reveals that the constant mass flow rate approach is more appropriate in modelling the blowing stage in ISBM process
International audienceStrain induced crystallisation of PET designed for stretch blow molding is studied combining well-controlled tensile tests and free blowing on a stretch blow prototype. Microstructure evolution is followed by WAXS and SAXS. Observations on blown parts clearly show that the microstructure can differ along the bottle and from processing conditions to another. Difference can be observed on crystalline orientation, periodic arrangement at the level of lamellae and long period. Range of long period, 8.5 to 13 nm is in agreement with literature. In certain case lamellar organisation disappears. Despite of high level of strain and evidence for strain hardening to occur during blowing no perfect crystalline pattern is observed, except in very thick zones. Interrupted tensile tests followed by quenching demonstrates that strain hardening is not correlated to prefect crystallisation. Microstructure clearly depends on the three parameters: temperature, strain rate and strain. It is concluded that strain hardening is mainly controlled by first stages of crystallisation and that actual crystallisation occurs during a following relaxation step. This later is then highly dependent upon cooling step
International audienceThe behaviour of oxide scales in the finishing Hot Strip Mill is simulated by the hot Plane Strain Compression Test (PSCT). Compared with the ideal case of homogeneous plastic co-deformation of the oxide layer and the underlying metal, different types of defects are described: delamination at the interface or within the oxide layer; interfacial plastic instability due to the jump of the mechanical properties; perpendicular, through-thickness cracks where the axial strain parallel to the interface dominates, followed by micro-extrusion of metal between the fragments; oblique cracks followed by sliding along the lips, where shear dominates. The Finite Element Method (FEM) is used to bring elements of interpretation, as to which conditions determine each mechanism. Conclusions for the behaviour in hot rolling are sketche
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.