Strain ratio and volume change during tension and compression creep of thermoplastics

Mallon, Philip; McCammond, D.; Benham, P. P.

doi:10.1002/pen.760120606

Cited by 21 publications

(7 citation statements)

References 5 publications

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“…Negative volume variations were observed during creep tests on semi-crystalline polymers [4,13,26]. Cherry and Hin [13] measured volume variation of PE using three mechanical extensometers under creep at ambient temperature.…”

Section: Bibliographic Data On Compaction Amplitudementioning

confidence: 99%

“…Pioneer systems were essentially based on fluid dilatometers [1,3] but their performances were rather limited because they only gave access to global volume changes and were very sensitive to temperature fluctuations. Another family of systems utilized multiaxially disposed mechanical extensometers but: -they were complicated to manipulate; -they caused unwanted indentation at the surface of soft polymers; -they were generally limited to low temperatures [4,[8][9][10]13]. Although the above techniques are still applied by some researchers, the computerized video techniques developed during the last decade brought a decisive contribution to the assessment of volume strain in polymers.…”

Section: Introductionmentioning

confidence: 99%

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Volume Variation Process of High-Density Polyethylene During Tensile and Creep Tests

Addiego¹,

Dahoun²,

G’Sell³

et al. 2006

Oil & Gas Science and Technology - Rev. IFP

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Résumé -Processus de la variation volumique du polyéthylène à haute densité au cours d'essais de traction et de fluage -Des éprouvettes de polyéthylène à haute densité ont été soumises à des essais de traction et des tests de fluage à l'aide d'un dispositif d'essais mécaniques à pilotage vidéo-métrique (VidéoTraction ® ). L'évolution du volume spécifique de ce polymère semi-cristallin est caracté-risée en fonction de la déformation vraie. Dans le stade élastique, on mesure une expansion hydrostatique puis, dans le stade plastique, on note une compétition entre un effet de compaction et un phénomène de dilatation. La compaction, sans doute surestimée dans les expériences, est toutefois un mécanisme important dû à l'orientation des chaînes amorphes au cours de l'étirage. Ce phénomène est attesté par des mesures de diffraction des rayons X qui montrent une réduction de la distance moyenne entre les chaînes amorphes. Le processus de dilatation s'explique par la diminution du taux de cristallinité et par la formation, la croissance et la coalescence de craquelures au sein et entre les sphérolites. L'observation d'échan-tillons déformés par microscopie électronique révèle ces défauts. La compétition compaction/dilatation est dictée par la mobilité de la phase amorphe influencée elle-même par la température et le temps. Abstract -Volume Variation Process of High-Density Polyethylene During Tensile and Creep Tests -Samples of high-density polyethylene have been subjected to tensile tests and creep experiments by means of a video-controlled testing system (VidéoTraction © ). The evolution of specific volume in this semi-crystalline polymer is determined versus true strain. In the elastic stage, we measure a hydrostatic expansion and then, in the plastic stage, we observe a competition between a compaction effect and a dilatation phenomenon. Although compaction is probably overestimated in the present testing technique, it represents a pertinent mechanism that is ascribed to the orientation of the amorphous chains during stretching. This phenomenon is characterized by X-ray diffraction measurements that show a reduction of average distance between amorphous chains. Dilatation process is explained by the diminution of crystallinity and by the formation, growth and coalescence of crazes inside and between spherulites.Electron microscopy reveals these defects. The competition between compaction and dilatation, controlled by the mobility of the amorphous phase, depends on temperature and time.

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Section: Bibliographic Data On Compaction Amplitudementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Volume Variation Process of High-Density Polyethylene During Tensile and Creep Tests

Addiego¹,

Dahoun²,

G’Sell³

et al. 2006

Oil & Gas Science and Technology - Rev. IFP

View full text Add to dashboard Cite

show abstract

“…Additionally, in [25], Tschoegl et al consider that in cyclic tests, Poisson's ratio of polymers depends on frequency. Mallon et al [26] performed creep tensile and compressive tests on PMMA, PVC, and PP polymers and proved that Poisson's ratios vary in time and depend on the sign of the stress applied.…”

Section: Introductionmentioning

confidence: 99%

New Aspects in the Mechanical Behavior of a Polycarbonate Found by an Experimental Study

Calderón

Díaz

2018

Advances in Materials Science and Engineering

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The aim of this paper was to analyze in detail the mechanical behavior of a polycarbonate by means of uniaxial tensile and compressive tests and to reveal new key aspects that must be taken into account in any predictive model. Uniaxial monotonic and creep-recovery tests were carried out at a variety of temperatures, stress levels, and load rates to get a complete description of the material response. Prior to mechanical testing, the material was subjected to a thermal rejuvenation in order to eliminate any previous aging and to obtain reliable and useful results. In every test, a complete determination of the strain state was assured by measuring axial and transverse strains with strain gauges. During the tests, significant asymmetry effects and viscous phenomena already reported by other authors were confirmed. The newest finding is that a nonlinear master transverse strain/axial strain curve matches perfectly with the experimental curves. This master curve is temperature- and rate-independent. Another originality of this paper is the disclosure of an instantaneous, hypoelastic-like behavior at high strain rates. The experimental observations presented in this study should be incorporated by a theoretical model whose aim is to accurately predict the mechanical behavior of polycarbonate subjected to any 3D stress state.

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“…Mechanical extensometers were tentatively developed to analyze multiaxial deformation in samples under tension [15][16][17][18]. These techniques marked the first steps towards the correct assessment of volume variation, but the calibrated region investigated was often too large with respect to the characteristic length of the necks.…”

Section: Introductionmentioning

confidence: 99%

Characterization of volume strain at large deformation under uniaxial tension in high-density polyethylene

Addiego

Dahoun

G’Sell

et al. 2006

Polymer

150

140

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Strain ratio and volume change during tension and compression creep of thermoplastics

Cited by 21 publications

References 5 publications

Volume Variation Process of High-Density Polyethylene During Tensile and Creep Tests

Volume Variation Process of High-Density Polyethylene During Tensile and Creep Tests

New Aspects in the Mechanical Behavior of a Polycarbonate Found by an Experimental Study

Characterization of volume strain at large deformation under uniaxial tension in high-density polyethylene

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