알 수 없는 중요한 방향의 2축 피로 상태 분석
장치 표면의 스트레인은 rosettes와 3개의 측정 그리드(strain gages)를 이용한 피로 시험 분석에서 측정 됩니다.
The three rosettes available in the 0°/45°/90° and 0°/60°/120° designs are designated by the letters a, b and c. 3 strains, ea, eb, and ec are measured accordingly using a rosette with 3 measuring grids.
After the principal normal stresses s1 and s2 are measured, the principal directions are determined. To do this, an angle j is determined. This angle is arranged starting from the axis of the reference measuring grid a in a mathematically positive direction (counterclockwise). The axis of the measuring grid a forms one arm of the angle j. The other arm represents the first principal direction. This is the direction of the principal normal strain s1 (identical with the principal strain direction e1).
The second principal direction (direction of principal normal strain s2) has an angle of j+90°.