A New Application of Dynamic Indentation: Indentation Machining Technology

While the indentation method is an excellent way to evaluate the mechanical properties of various sizes of materials, from the nano-scale to the macro-scale, its applications have been limited to measuring mechanical properties. In this study we propose a new application of the dynamic indentation method, in an indentation machining technology for mass-production. The core idea is that the array of residual indentations generated by dynamic indentation testing can be used to fabricate a lens array suitable for thinner and brighter displays. We developed an advanced system from a dynamic indentation system, whose maximum speed and maximum specimen size were about 10Hz and 250 mm*250 mm, respectively. Using dual actuating heads this system was used to produce arrays of lenses having depths of 1 μm to 6 mm. Pile-up is a critical reason why indentation machining technology had been not widely used in display industries. Since lower pile-up is observed in more ductile copper-based metals, we increased the annealing time of the metal molds to reduce the amount of pile-up. Then, following a quantitative analysis of the annealing heat treatment and resulting amount of pile-up, a lens array was successfully machined on a metal mold fabricated by the developed system. The machined metal mold was used to manufacture optical plates for a lens array. The results verified that the indentation machining technology proposed in this study, based on the dynamic indentation method, can be applied for the manufacturing of optical components for better displays.

[1]  G. Pharr,et al.  Measurement of hardness and elastic modulus by instrumented indentation: Advances in understanding and refinements to methodology , 2004 .

[2]  J. Vlassak,et al.  Determination of indenter tip geometry and indentation contact area for depth-sensing indentation experiments , 1998 .

[3]  G W Marshall,et al.  Evaluation of a new modulus mapping technique to investigate microstructural features of human teeth. , 2004, Journal of biomechanics.

[4]  M. M. Chaudhri,et al.  The effect of the indenter load on the nanohardness of ductile metals : an experimental study on polycrystalline work-hardened and annealed oxygen-free copper , 1999 .

[5]  D. Kwon,et al.  Optimum definition of true strain beneath a spherical indenter for deriving indentation flow curves , 2006 .

[6]  Jiwang Yan,et al.  Manufacturing structured surface by combining microindentation and ultraprecision cutting , 2012 .

[8]  Kuan-Yu Chen,et al.  Patterned microlens array for efficiency improvement of small-pixelated organic light-emitting devices. , 2008, Optics express.

[9]  Stephen R. Forrest,et al.  Improved light out-coupling in organic light emitting diodes employing ordered microlens arrays , 2002 .

[10]  G. Pharr,et al.  An improved technique for determining hardness and elastic modulus using load and displacement sensing indentation experiments , 1992 .

[11]  D. Jarzabek,et al.  Decrease of Nano-hardness at Ultra-low Indentation Depths in Copper Single Crystal , 2016 .

[12]  Robert D. Weed,et al.  Copper and Copper Alloys , 2015 .

[13]  D. Kwon,et al.  Estimation of biaxial surface stress by instrumented indentation with sharp indenters , 2004 .

[14]  Donald S. Gardner,et al.  Plastic properties of thin films on substrates as measured by submicron indentation hardness and substrate curvature techniques , 1986 .

[15]  John G Swadener,et al.  Measurement of residual stress by load and depth sensing indentation with spherical indenters , 2001 .

[16]  Brian R. Lawn,et al.  A Critical Evaluation of Indentation Techniques for Measuring Fracture Toughness: I , 1981 .

[17]  George M. Pharr,et al.  On the measurement of stress–strain curves by spherical indentation , 2001 .

[18]  E. Herbert,et al.  Continuous stiffness measurement during instrumented indentation testing , 2010 .

[19]  Yang-Tse Cheng,et al.  Effects of 'sinking in' and 'piling up' on estimating the contact area under load in indentation , 1998 .

[20]  M. M. Chaudhri,et al.  LETTER TO THE EDITOR: The load-bearing area of a hardness indentation , 1988 .

[21]  D. Kwon,et al.  An instrumented indentation technique for estimating fracture toughness of ductile materials: A critical indentation energy model based on continuum damage mechanics , 2006 .