## 5aPA7. Voigt stiffnesses and amplitude-dependent internal friction in monocrystal silicon.

### Session: Friday Morning, May 17

### Time: 10:40

**Author: Hassel Ledbetter**

**Author: Sudook Kim**

**Author: Christopher Fortunko**

**Location: NIST, 325 Broadway, Boulder, CO 80303**

**Author: Paul Heyliger**

**Location: Colorado State Univ., Fort Collins, CO 80523**

**Author: Mitsuru Tanaka**

**Location: NRLM, Tsukuba, Ibaraki, 305 Japan**

**Abstract:**

The specimen consisted of a 1-cm-diam monocrystal silicon sphere. Voigt
elastic stiffnesses C[inf 11], C[inf 12], C[inf 44] were determined from the
macroscopic eigenvibration frequencies. The C[inf ij] results agree closely with
previous measurements by conventional acoustic methods. The internal frictions
Q[sup -1] were determined for two nondegenerate eigenfrequencies. One depends
only on the shear modulus C[inf 44]. The other, composed of 0.64C[inf 11]+0.32
C[inf 12]+0.04 C[inf 44], is nearly independent of C[inf 44]. Granato--Lucke
plots of ln (epsilon) Q[sup -1] vs ln (epsilon)[sup -1] showed two regions. The
higher strain region showed a slope of approximately 3.5 times that of the lower
strain region. A dislocation-model explanation will be offered for higher Q[sup
-1] at higher (epsilon).

from ASA 131st Meeting, Indianapolis, May 1996