The influence of indenter-surface misalignment on the results of instrumented indentation tests

Pelletier, Cgn Christophe; Dekkers, E.C.A.; Govaert, Leon Le; Toonder, den Jmj Jaap; Meijer, Heh Han

doi:10.1016/j.polymertesting.2007.06.009

Cited by 22 publications

(10 citation statements)

References 17 publications

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“…Correction for tip-sample misalignment was performed using a specially designed alignment tool. For details on the experimental technique see; [30,38] and for the alignment tool see. [38] Tensile tests were performed on a Zwick Z010 universal tensile tester at a room temperature of 23 8C.…”

Section: Sample Preparationmentioning

confidence: 99%

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Predicting the Long‐Term Mechanical Performance of Polycarbonate from Thermal History during Injection Molding

Engels

Breemen

Govaert

et al. 2009

Macro Materials & Eng

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The influence of the thermal history experienced during injection molding on the mechanical properties of polycarbonate is investigated. Distributions of the yield stress as they result from inhomogeneous cooling during processing, predicted by a previously developed modeling approach, are validated and are in good agreement with experiment. Predictions of the mechanical performance for different mold temperatures during processing are also validated over a range of applied strain and deformation rates and applied stresses and forces, for simple tensile bars and an actual product. Good agreement is found. It is shown that mold temperature has a tremendous influence on the life time of polymer products, which can differ by more than two orders of magnitude.magnified image

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Section: Sample Preparationmentioning

confidence: 99%

“…For details on the experimental technique see; [30,38] and for the alignment tool see. [38] Tensile tests were performed on a Zwick Z010 universal tensile tester at a room temperature of 23 8C. Experiments were performed by applying constant linear strain rates _ " ¼ _ x=l 0 ð Þor engineering stresses s ¼ F=A 0 ð Þ .…”

Section: Sample Preparationmentioning

confidence: 99%

Predicting the Long‐Term Mechanical Performance of Polycarbonate from Thermal History during Injection Molding

Engels

Breemen

Govaert

et al. 2009

Macro Materials & Eng

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“…2), E can be derived in a way that circumvents some of the problems mentioned above. [35] The advantages of this probe geometry include that the contact area is constant and independent of the indentation depth, no assumptions on the contact perimeter are required and, initially, Figure 1. Load-displacement response obtained upon indenting polystyrene with a Berkovich indenter, showing the fit applied in the Oliver and Pharr method to obtain the slope S at the onset of the unloading step as well as the contact depth h c .…”

Section: Progress Reportmentioning

confidence: 99%

“…plasticity is negligible. [35] Unfortunately, that geometry is very sensitive to tip-sample misalignment: 18 misalignment results in approximately 10% difference in E. It is possible to minimize the misalignment. [35] However, performing an alignment procedure for all members of the HTE library is time-consuming and is therefore not HTE-compatible.…”

Section: Progress Reportmentioning

confidence: 99%

Challenges and Progress in High‐Throughput Screening of Polymer Mechanical Properties by Indentation

et al. 2009

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Depth‐sensing or instrumented indentation is an experimental characterization approach well‐suited for high‐throughput investigation of mechanical properties of polymeric materials. This is due to both the precision of force and displacement, and to the small material volumes required for quantitative analysis. Recently, considerable progress in the throughput (number of distinct material samples analyzed per unit time) of indentation experiments has been achieved, particularly for studies of elastic properties. Future challenges include improving the agreement between various macroscopic properties (elastic modulus, creep compliance, loss tangent, onset of nonlinear elasticity, energy dissipation, etc.) and their counterpart properties obtained by indentation. Sample preparation constitutes a major factor for both the accuracy of the results and the speed and efficiency of experimental throughput. It is important to appreciate how this processing step may influence the mechanical properties, in particular the onset of nonlinear elastic or plastic deformation, and how the processing may affect the agreement between the indentation results and their macroscopic analogues.

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“…This problem was solved by sample re-alignment using a specially designed alignment tool. Details on the alignment procedure can be found elsewhere [59]. The geometry of the tip was characterized using SEM and AFM and proved to have a tipdiameter of 10 µm (Figure (5a)), a top angle of 72 º (see Figure (5b)), and an edge radius of 1 µm (Figure (5c)).…”

Section: Techniquesmentioning

confidence: 99%

Numerical simulation of flat-tip micro-indentation of glassy polymers: Influence of loading speed and thermodynamic state

Breemen¹,

Engels²,

Pelletier³

et al. 2009

Philosophical Magazine

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Flat-tip micro-indentation tests were performed on quenched and annealed polymer glasses at various loading speeds. The results were analyzed using an elastoviscoplastic constitutive model that captures the intrinsic deformation characteristics of a polymer glass: a strain-rate dependent yield stress, strain softening and strain hardening.The advantage of this model is that changes in yield stress due to physical aging are captured in a single parameter. The two materials studied (polycarbonate (PC) and poly(methyl methacrylate) (PMMA)), were both selected for the specific rate-dependence of the yield stress that they display at room temperature. Within the range of strain rates experimentally covered, the yield stress of PC increases linearly with the logarithm of strain-rate, whereas for PMMA, a characteristic change in slope can be observed at higher strain rates. We demonstrate that, given the proper definition of the viscosity function, the flat-tip indentation response at different indentation speeds can be described accurately for both materials. Moreover, it is shown that the model captures the mechanical response on the microscopic scale (indentation) as well as on the macroscopic scale with the same parameter set. This offers promising possibilities to extract mechanical properties of polymer glasses directly from indentation experiments.

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The influence of indenter-surface misalignment on the results of instrumented indentation tests

Cited by 22 publications

References 17 publications

Predicting the Long‐Term Mechanical Performance of Polycarbonate from Thermal History during Injection Molding

Predicting the Long‐Term Mechanical Performance of Polycarbonate from Thermal History during Injection Molding

Challenges and Progress in High‐Throughput Screening of Polymer Mechanical Properties by Indentation

Numerical simulation of flat-tip micro-indentation of glassy polymers: Influence of loading speed and thermodynamic state

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