Research Papers

Tension–Torsion Combined Loading Test Equipment for a Minute Beam Specimen

[+] Author and Article Information
Takahiro Namazu

Associate Professor
Division of Mechanical Systems,
Department of Mechanical and Systems Engineering,
University of Hyogo,
2167 Shosha, Himeji,
Hyogo 671-2201, Japan;
Japan Science and Technology Agency,
4-1-8, Honcho, Kawaguchi,
Saitama 332-0012, Japan
e-mail: namazu@eng.u-hyogo.ac.jp

Shozo Inoue

Division of Mechanical Systems,
Department of Mechanical and Systems Engineering,
University of Hyogo,
2167 Shosha, Himeji, Hyogo 671-2201, Japan

1Corresponding author.

Contributed by the Materials Division of ASME for publication in the Journal of Engineering Materials and Technology. Manuscript received May 9, 2012; final manuscript received October 1, 2012; published online December 21, 2012. Assoc. Editor: Hanchen Huang.

J. Eng. Mater. Technol 135(1), 011004 (Dec 21, 2012) (9 pages) Paper No: MATS-12-1087; doi: 10.1115/1.4007811 History: Received May 09, 2012; Revised October 01, 2012

In this article, the development of quasi-static tension–torsion combined loading test equipment for a microscale beam specimen is described. The equipment is composed of a piezoelectric actuator in actuator case for uniaxial tensile loading, a load cell for measuring X-Y-Z-axes forces and θ-axis torque, a stepping motor for rotating sample stage, X-Y-Z-stages for alignment, and a CCD camera for measuring tensile elongation using original image analysis software. The shape and dimension of all the mechanical jigs were designed by means of finite element analysis (FEA). The tension and torsion loading systems are able to be individually operated, so that uniaxial tension, pure torsion, and combined tension–torsion loadings can be realized. The specimen that was designed in consideration of typical optical microelectromechanical systems (MEMS) devices consists of a mirror plate supported by two microbeam structures, four springs, and a frame with chucking holes. Single crystal silicon (SCS) specimens were fabricated by deep reactive ion etching (DRIE). It was confirmed that the above-described three types of loadings were able to be successfully applied to the beam specimens. All the specimens fractured in a brittle manner and showed different-shape fracture surfaces under different deformation modes.

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Fig. 1

Schematic of pure torsion, uniaxial tension, and tension–torsion combined loading test for investigating the mechanical characteristics of a microscale beam specimen. The three types of the materials test are able to be realized by the combination of uniaxial tension and twisting mechanisms.

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Fig. 2

Schematic of the test specimen designed in consideration of an optical MEMS mirror device along with the dimensions. The specimen is composed of a mirror plate, two beam specimens, four springs, and a frame with chucking holes.

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Fig. 3

Process flow for fabricating the specimen made of SCS along with the photograph of the produced specimen. DRIE was used for the fabrication.

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Fig. 4

The developed tension–torsion combined loading test equipment for a microscale beam specimen. The equipment that includes a piezoelectric actuator, X-Y-Z motor stage, rotation motor stage, X-Y-Z-θ load cell, chucking jig, and CCD camera can be classified broadly into two mechanisms for uniaxial tension test and pure torsion test.

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Fig. 5

Distributions of X displacement and equivalent stress derived from FEA. The maximum equivalent stress was generated at the curvature portion of spring. The value was 45.5 MPa, which was one-eleventh of the yield stress of A7075T6.

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Fig. 6

Schematic of the mechanical component for rotation loading along with Z displacement distribution in the component calculated by FEA

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Fig. 7

Representative verification test results showing (a) the influence of repulsive force on the actuator displacement, (b) the displacement of actuator case and load cell when a tensile force was applied to a specimen, and (c) the comparison in rotation angle between estimation and experiment

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Fig. 8

Snapshots of sample setting procedure. First, two rhombic-shape chucking holes in both ends of a specimen chip are individually hooked to cylindrical poles on tensile jigs. After the alignment between specimen longitudinal direction and tension direction, those two chucking portions are then fastened mechanically. At the same time, the backside of a mirror plate is supported by a rotation jig. Finally, a rotation chuck jig is fixed to the rotation jig, and the plate is supported from both surface sides.

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Fig. 9

Representative loading test results showing (a) the tensile force–displacement relation obtained in uniaxial tensile test, (b) the torque-rotation angle relation obtained in pure torsion test, and (c) the relationships between torque, tensile force, and rotation angle obtained in tension–torsion combined loading test

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Fig. 10

SEM photographs of the fracture surface of the specimens after uniaxial tension, pure torsion, and tension–torsion combined loading tests




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