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Technical Briefs

# Measurement of Young’s Modulus of Human Tympanic Membrane at High Strain Rates

[+] Author and Article Information
Huiyang Luo

School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078

Chenkai Dai, Rong Z. Gan

School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019

Hongbing Lu

School of Mechanical and Aerospace Engineering, Oklahoma State University, Stillwater, OK 74078hongbing.lu@okstate.edu

J Biomech Eng 131(6), 064501 (Apr 29, 2009) (8 pages) doi:10.1115/1.3118770 History: Received July 17, 2008; Revised February 24, 2009; Published April 29, 2009

## Abstract

The mechanical behavior of human tympanic membrane (TM) has been investigated extensively under quasistatic loading conditions in the past. The results, however, are sparse for the mechanical properties (e.g., Young's modulus) of the TM at high strain rates, which are critical input for modeling the mechanical response under blast wave. The property data at high strain rates can also potentially be converted into complex modulus in frequency domain to model acoustic transmission in the human ear. In this study, we developed a new miniature split Hopkinson tension bar to investigate the mechanical behavior of human TM at high strain rates so that a force of up to half of a newton can be measured accurately under dynamic loading conditions. Young’s modulus of a normal human TM is reported as 45.2–58.9 MPa in the radial direction, and 34.1–56.8 MPa in the circumferential direction at strain rates $300–2000 s−1$. The results indicate that Young’s modulus has a strong dependence on strain rate at these high strain rates.

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## Figures

Figure 1

Schematic of the TM strip specimens cut from TM samples: (a) in the radial direction (TM: Tb07–24), (b) in the circumferential direction (TM: TB07–28), and (c) a schematic of the fiber orientation of human TM (revised from Ref. 11)

Figure 2

TM strip specimen mounted on a clamping fixture: (a) schematic of gel glue applied on the bottom clamp fixtures and a TM specimen and (b) assembly of TM strip with two covered plates and tightening screws

Figure 3

Schematic of a miniature split Hopkinson tension bar

Figure 4

Typical recorded signals from incident bar, transmission bar, and X-cut crystal

Figure 5

Typical data for examination of dynamic force equilibrium and constant strain rate history on a TM specimen

Figure 6

Typical oscilloscope signal recorded during TM preconditioning

Figure 7

Stress strain curves of a TM in the radial direction during preconditioning

Figure 8

Stress-strain curves of a TM specimen in the radial direction under similar testing conditions for repeatability examination

Figure 9

Typical stress-strain curves of TM strip specimens in the radial and circumferential directions at high strain rates. Note that TM specimens did not necessarily break at these strain rates. The maximum strain experienced in each experiment was limited by the loading duration time of the miniature SHTB.

Figure 10

Comparison of Young’s modulus of TM in the radial and circumferential directions at different strain rates

Figure 11

Typical failure patterns of TM tensile specimens: (a) a TM specimen in the circumferential direction and (b) a TM specimen in the radial direction

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