A numerical approach to spherical indentation techniques for material property evaluation

Effects of chemical composition and heat treatment on the microstructures and mechanical properties were investigated with automated ball-indentation tests, scanning and transmission electron microscopy, and energy-dispersive X-ray analysis. In this work, the automated ball-indentation (ABI) technique was compared with the standard mechanical tests. The ABI method is based on load-controlled multiple indentations into a polished surface by a spherical indenter. The indentation depth is progressively increased to the specified maximum limit with intermediate partial unloading. This technique allows us to measure the yield strength, the stress-strain curve, the strength coefficient and the strain-hardening exponent. For all the test materials and conditions, the ABI-derived results were in very good agreement with those obtained with conventional standard test methods. We analyzed the effect of heat treatment on the alloys with different chemical compositions. Heat treatment leads to changes in the mechanical properties of the alloys, which are the results of several processes. Keywords: Al-alloys, heat treatment, tensile strength, yield strength, ABI hardness test Vpliv kemijske sestave in toplotne obdelave na mikrostrukturo in mehanske lastnosti je bil preiskovan z avtomatiziranim preizkusom trdote z vtiskovanjem kroglice, z vrsti~no in presevno elektronsko mikroskopijo in energijsko disperzijsko rentgensko spektroskopijo. V tem delu je bila tehnika avtomatskega vtiskovanja kroglice (ABI) primerjana s standardnimi mehanskimi preizkusi. ABI metoda temelji na kontrolirani obte`itvi pri ve~kratnem vtiskovanju krogli~nega telesa v polirano povr{ino. Globina vtiskovanja postopoma nara{~a do maksimalne dolo~ene globine z vmesnimi razbremenitvami. Ta tehnika omogo~a merjenje meje te~enja, krivulje raztezek-obremenitev, koeficienta trdnosti in eksponenta napetostnega utrjevanja. Za vse preizku{ane materiale in pogoje, so se dobljeni ABI rezultati dobro ujemali z rezultati dobljenimi iz obi~ajnih metod preizku{anja. Preu~evan je bil vpliv toplotne obdelave na zlitine z razli~no kemijsko sestavo. Toplotna obdelava povzro~i spremembo mehanskih lastnosti zlitin, kar je posledica ve~ih procesov.

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“…4,5 As shown previously 6 , the results obtained with this method achieve good compatibility with those of the conventional methods.…”

Section: Introductionsupporting

confidence: 77%

Use of the ABI technique to measure the mechanical properties of aluminium alloys: effect of heat-treatment conditions on the mechanical properties of alloys

Trudonoshyn

Puchnin²,

Prach³

2016

Mater. Tehnol.

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“…This model includes local non linearity to model frictionless contact between the indenter and the coating and material non linearity to represent the plastic behaviour of abradable materials. Frictionless contact is assumed because it has been observed that friction produces negligible effects on the curve relating the load to the depth of penetration [10]. TARGE169 and CONTA171 elements were used to model contact between the coating and the indenter and the mesh density is refined in the vicinity of the contact area to account for high stress gradient growing in this region.…”

Section: Finite Element Modelmentioning

confidence: 99%

“…To cover a wider range of alloys and pure metals, Zhao et al [9] have extended the work of Cao and Lu to materials involved in engineering design, such as copper, aluminium, tin and tin alloys. Lee et al [10] have proposed numerical formulas based on the incremental theory of plasticity for material property evaluation. The material properties used for the FE analysis cover the property range of general metals with a Young's modulus varying from 70 to 400 GPa.…”

Section: Introductionmentioning

confidence: 99%

Finite element modeling of abradable materials – Identification of plastic parameters and issues on minimum hardness against coating's thickness

Peyraut

Seichepine

Coddet

et al. 2008

Int. J. Simul. Multidisci. Des. Optim.

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-Abradable materials are used to decrease the gas consumption of aircraft engines by minimizing the gap between the blade tips and the stator. The key idea consists in using the blades themselves to machine the gap on the abradable coating. The best compromise between soft and hard coating properties has to be reached to avoid blades wear and prevent coating erosion by gas flux and particles. The plastic parameters of abradable coating were identified by using an optimization process directly connected to FEA. The first order optimization method (conjugate gradient strategy + golden section algorithm) was applied to achieve the optimal solution. A good agreement was found between experimental and numerical results. The plastic parameters were used to study the hardness variability of abradable materials with the coating thickness. Surprisingly, a minimum hardness value was found while it was expected that hardness should be always decreasing with thickness. It has been demonstrated that this minimum is produced by the boundary conditions influence on hardness measurement. This research work was completed within the Seal-Coat project funded by the European Commission under the FP5 Growth Program.

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“…This method needs a large number of FEM computations within a certain range of the material properties defined as the power law equation. The dimensional function has established a relationship between the indentation characteristics and material properties [16,[73][74][75][76][77][78][79][80].  theorem is the key theorem in dimensional analysis, which could reduce complex physical problems to their simplest form [81,82].…”

Section: Determination Of Plastic Property Through Spherical Indentatmentioning

confidence: 99%

“…The strain constraint factor,  , should vary with indentation depth through which the tangent of the corresponding contact point can be equal to the same angle of a sharp indenter [6,55]. The fact is that the equivalent stress and strain at an arbitrary point beneath the indenter should be equal to the uniaxial stress strain curve from the result of FEM, although the equivalent stress and strain of the material vary from point to point [75,146] .…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Determining the elastic-plastic properties of metallic materials through instrumented indentation

Chang¹

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AgradecimientosPrimero, me gustaria agradecer a mis supervisores. Me gustaría expresar mi máximo aprecio hacia mi supervisor Dr. J. Ruiz-Hervias por guiarme y ayudarme durante estos años en el laboratorio. He aprendido de él, no solo en lo estrictamente académico, si no en su generosidad y en su mente positiva hacia la vida. Además, también quería agradecer a mi co-supervisor Dr. M. A. Garrido. Él ha jugado un papel muy significante en el inicio de mi vida académica. Sus ideas y su entusiasmo siempre me inspiraron y me motivaron. Sin su paciencia y su ayuda, nunca hubiera acabado esta tesis. ResumenEn los últimos años, y asociado al desarrollo de la tecnología MEMS, la técnica de indentación instrumentada se ha convertido en un método de ensayo no destructivo ampliamente utilizado para hallar las características elástico-plásticas de recubrimientos y capas delgadas, desde la escala macroscópica a la microscópica. Sin embargo, debido al complejo mecanismo de contacto debajo de la indentación, es urgente proponer un método más simple y conveniente para obtener unos resultados comparables con otras mediciones tradicionales. En este estudio, el objetivo es mejorar el procedimiento analítico para extraer las propiedades elástico-plásticas del material mediante la técnica de indentación instrumentada.La primera parte se centra en la metodología llevada a cabo para medir las propiedades elásticas de los materiales elásticos, presentándose una nueva metodología de indentación, basada en la evolución de la rigidez de contacto y en la curva fuerza-desplazamiento del ensayo de indentación. El método propuesto permite discriminar los valores de indentación experimental que pudieran estar afectados por el redondeo de la punta del indentador. Además, esta técnica parece ser robusta y permite obtener valores fiables del modulo elástico.La segunda parte se centra en el proceso analítico para determinar la curva tensión-deformación a partir del ensayo de indentación, empleando un indentador esférico. Para poder asemejar la curva tension-deformación de indentación con la que se obtendría de un ensayo de tracción, Tabor determinó empíricamente un factor de constricción de la tensión () y un factor de constricción de la deformación (). Sin embargo, la elección del valor de  y  necesitan una derivación analítica. Se describió analíticamente una nueva visión de la relación entre los factores de constricción de tensión y la deformación basado en la deducción de la viii ecuación de Tabor. Un modelo de elementos finitos y un diseño experimental se realizan para evaluar estos factores de constricción. A partir de los resultados obtenidos, las curvas tension-deformación extraidas de los ensayos de indentación esférica, afectadas por los correspondientes factores de constricción de tension y deformación, se ajustaron a la curva nominal tensión-deformación obtenida de ensayos de tracción convencionales.En la última parte, se estudian las propiedades del revestimiento de cermet Inconel 625-Cr 3 C 2 que es depositado en el medio de una a...

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A numerical approach to spherical indentation techniques for material property evaluation

Cited by 218 publications

References 21 publications

Use of the ABI technique to measure the mechanical properties of aluminium alloys: effect of heat-treatment conditions on the mechanical properties of alloys

Use of the ABI technique to measure the mechanical properties of aluminium alloys: effect of heat-treatment conditions on the mechanical properties of alloys

Finite element modeling of abradable materials – Identification of plastic parameters and issues on minimum hardness against coating's thickness

Determining the elastic-plastic properties of metallic materials through instrumented indentation

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