Yong Huan

A moving-coil designed micro-mechanics tester with application on MEMS

A moving-coil designed micro-mechanics tester, named as MicroUTM (universal testing machine), is in-house developed in this paper for micro-mechanics tests. The main component is a moving coil suspended in a uniform magnetic field through a set of springs. When a current passes through the coil, the electromagnetic force is proportional to the magnitude of the current, so the load can easily be measured by the current. The displacement is measured using a capacitive sensor. The load is calibrated using a Sartorius BP211D analytical balance, with a resolution/range of 0.01 mg/80 g or 0.1 mg/210 g. The displacement is calibrated using a HEIDENHAIN CT-6002 length gauge with an accuracy of ±0.1 µm. The calibration results show that the load range is ±1 N and the displacement range is ±300 µm. The noise levels of the load and displacement are 50 µN and 150 nm, respectively. The nonlinearity of the load is only 0.2%. Several in-plane load tests of the MEMS micro-cantilever are performed using this tester. Experimental results, with excellent repeatability, demonstrate the reliability of the load measurement as well as the flexible function of this tester.

Development of a high-resolution micro-torsion tester for measuring the shear modulus of metallic glass fibers

A high-resolution micro-torsion tester is developed based on electromagnetism, and the shear modulus of metallic glass fiber (Pd40Cu30Ni10P20) is measured using this tester. The torque is measured by a coil-magnet component and the rotation angle is measured by an inductive angular transducer. The calibration results show that the torque capacity of this tester is 1.1 x 10(-3) N m with resolution of 3 x 10(-8) N m and the rotation angle capacity is 90 degrees with a resolution of 0.01 degrees. A set of metallic glass fibers, with diameter of about 90 mu m, are tested using this tester. The average shear modulus is obtained as 20.2 GPa (+/- 6%).

Micro/Nanomechanical and Tribological Properties of Thin Diamond-Like Carbon Coatings

The diamond-like carbon (DLC) films with different thicknesses on 9Crl8 bearing steels were prepared using vacuum magnetic-filtering arc plasma deposition. Vickers indentation. nanoin-dentation and nanoscratch tests were used to characterize the DLC films with a wide range of applied loads. Mechanical and tribological behaviors of these submicron films were investigated and interpreted. The hardnesses of 9Crl8 and DLC, determined by nanoindentation, are approximately 8GPa and 60GPa respectively; their elastic moduli are approximately 25OGPa and 600GPa respectively. The friction coefficients of 9Crl8, DLC. organic coating, determined by nanoscratch, are approximately 0. 35, 0. 20 and 0. 13 respectively. It is demonstrated that nanoindentation and nanoscratch tests can provide more information about the near-surface elastic-plastic deformation, friction and wear properties. The correlation of mechanical properties and scratch resistance of DLC films on 9Crl8 steels can provide an assessment for the load-carrying capacity and wear resistance

Effect of Deformation Induced Microstructure Faults on the Elastic Mechanical Parameters of Micro-Scale Copper

The elastic mechanical parameters of initial and pre-twisted copper wires were investigated with the aid of a self-developed micro-torsion tester. It was found that the apparent elastic shear modulus and the apparent Young tensile modulus of the copper wires decrease by 13.3 and 8.4% after pre-twist deformation, respectively. In addition, the indentation modulus also decreases as the deformation is increased. When the deformation is more than 30%, the indentation modulus of pre-twisted copper wires is smaller than that of initial copper wires. Microstructural analyses show that the elastic modulus decreases with the proportion of faults.

The Influence of Boundary Conditions on Modulus Measurement in Uniaxial Compression Tests

There is distinct deviation between the intrinsic and measurement value of Young’s modulus in uniaxial compression tests. The key influence factor has always been owned to the friction between compression platens and specimen. However, we found this is not true by Finite element analysis (FEA) and experiments. FEA results show that the friction only makes a major influence on the plastic behavior, resulting in a barreling deformation, rather than on the elastic deformation behavior of specimen. In fact, the oblique contact between compression plate and specimen will severely influence the homogeneity of the stress field in specimen, and result in the deviation of the measured modulus value. This study can well interpret the relevant provision in ASTM E9-09 that only slim specimens (with aspect ratio ≥ 8) are suitable for the compression modulus tests.

Micromechanical Characterization of TiN Films on 9Cr18 Steels

TiN coatings 0.5mum thick were deposited by plasma are deposition on 9Cr18 steels. Vickers indentations, depth-sensing indentations and nanoscratches were produced with different tips on a broad range of applied load. Mechanical behavior of hard and brittle thin coatings on soft and ductile metallic substrates was investigated and interpreted. It is demonstrated that depth-sensing indentation and nanoscratch tests can provide more information about the near-surface elastic-plastic deformation, friction and wear properties. Compared with 9Cr18 steels, solid lubricating effects for TiN and organism/TiN coatings are very marked.