OS06W0434 Mechanical and thermal properties of thin metallic foils and wires using laser techniques

Abstract

There is an increasing necessity to record the deformation characteristics of microelements often consisting of freestanding foils and wires. The data required are either mechanical or thermal such as Young`s moduli, stress-strain values, fatigue-and thermal strain data, but the nominal strength of a structure changes by scaling its size. Due to this size effect, material data cannot be taken from macrospecimens, thus special testing procedures were introduced. Laseroptical sensors based on the speckle correlation method were applied to determine non-contacting strain values with high strain resolution. For the mechanical properties tensile tests were used for the freestanding foils and wires. For thermal strain measurements a laser speckle based dilatometer was designed. A short outline of applicability of the testing equipment is given. The following materials data are presented and discussed: Young`s modulus, mechanical and thermomechanical and thermal strain data of various Cu foils and wires with varying grain sizes, thickness and defined texture. A thickness effect was detected and is interpreted in terms of a "thickness to grain size ratio" approach.

A study of the mechanical and fatigue properties of metallic microwires

“…To study the correlation of the cyclic fatigue behaviour of the thin wires with the associated dislocation structures SEM–ECCI investigations (for details see Ref. [24]) were performed of fatigued wires of 20 μm, 50 μm and 125 μm diameter.…”

“…To record strain without contacting the specimen, an optical method using laser speckles was used. For a detailed description see Refs [22–24].…”

“…This system can be used in the same way as the usual area CCD sensor, but is especially suitable for testing thin wires and fibres (because of the pattern refinement) or when higher strain rates are needed 25 . A comparison of the technical data and the applicability of both systems are presented in Ref. [24].…”

“…To record strain without contacting the specimen, an optical method using laser speckles was used. For a detailed description see Refs [22][23][24]. The optical arrangement to determine the strain of a specimen is presented in Fig.…”

“…25 A comparison of the technical data and the applicability of both systems are presented in Ref. [24]. Because of the high strain resolution the laser speckle technique is especially suited for the determination of the Young's modulus of thin wires with high strength.…”