Delamination of thin strong film - poster

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Delamination of thin strong film - poster

  1. 1. Delamination of a Strong Thin Film From a Ductile Substrate During Indentation Loading and Unloading Adnan Abdul-Baqi & Erik van der Giessen Koiter Institute DelftIntroduction The cohesive surface modelIndentation loading and unloading of a strong elastic In the description of the interface as a cohesive surface, a small dis-film on a ductile substrate is modeled. The film is con- placement jump ∆ between the film and substrate is allowed, with nor-sidered to be elastic, the substrate is elastic perfectly- mal and tangential components ∆ n and ∆ t respectively. Theplastic and the indenter is spherical and rigid (Fig. 1). corresponding tractions we adopt in this study are those used by Xu andThe interface is modeled by means of a cohesive surface. Needleman [1]. Figure 2 shows these tractions in their uncoupled form. ˙ h 1.5 3 ∆t = 0 1 2 ∆n = 0 R 0.5 1 a 0 t max max increasing ∆ t 0 T /τ −0.5 T /σh n coating t −1 −1 increasing ∆ n −1.5 interface (a) −2 (b) −2 substrate −2.5 −1 0 1 2 3 4 5 6 −3 −3 −2 −1 0 1 2 3 ∆n/δn ∆t/δt Figure 1. Geometry. Figure 2. (a) Normal traction versus normal separation. (b) Tangential traction versus tangential separation.Results 0.00 σe/σy 0.00 σyy/σmax 2 0.5 φ (J/m2) 1.40 1.0 n 1.26 0.4 a 1.11 0.8 1.75 a 150 0.02 0.97 0.01 0.5 0.3 b b 200 0.82 0.3 c 400 0.68 1.5 0.2 0.53 0.1 c d 600 0.39 -0.1 0.1 e >> 600 0.04 0.24 0.02 1.25 d e -0.4 0 z (mm) 0.10 1 1.15 1.3 1.45 1.6 1.75z (mm) -0.6 F/(πR σy) 2 1 0.06 0.03 0.75 0.5 0.08 0.04 (a) (b) 0.25 0.10 0.05 0.00 0.02 0.04 0.06 0.08 0.10 0.00 0.01 0.02 0.03 0.04 0.05 0 0 0.25 0.5 0.75 1 1.25 1.5 1.75 2 r (mm) r (mm) h/tFigure 3. (a) Contour plot of the Von Mises effective stress at the maximum indentation depth Figure 4. Load versus displacement curves for dif-( h max = 2t ), φ n = 150 ( J ⁄ m 2 ). Arrows show the shear direction, line shows the location of the tan- ferent values of interfacial energies. Curve (e) repre-gentially delaminated area. (b) Contour plot of the vertical stress component at the end of the unloading sents the case of a perfect interface.stage ( F = 0 ), φ n = 500 ( J ⁄ m 2 ). 1 Conclusions 0.8 1. For relatively weak interfaces, delamination occurs in the loading stage. It is 0.6 E imprinted on the load vs displacement curve by a ‘kink’.E/Emax el E pl E int 0.4 ∫ F dh 2. Normal delamination occurs during the unloading stage, where a circular part E + E +E el pl int 0.2 of the coating is lifted off from the substrate. It is imprinted on the load vs dis- placement curve by a ‘hump’. 0 0 0.5 1 1.5 2 h/tFigure 5. Evolution of elastic, plastic, interfacial andapplied work during the loading and unloading process. [1] X.-P. Xu, A. Needleman, Model. Simul. Mater. Sci. Eng. 1 (1993) 111.

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