3.3.1 Model calibration

To calibrate the finite element model, a load of 3500 N and a moment of 35,000 N-mm were used. The target of the model was to fit the displacement of A point near to the experimental displacement, 2.89 mm along y-direction (Table 3). The range of Young's modulus used to the joints was 6000– 200,000 MPa. The solution converged for a range of Young's modulus between 6000 and 9880 MPa (Table 4).

#### 3.3.2 Model validation

Young's modulus obtained from the calibration process (Table 4) was used to define the rigidity of the joints. The model was validated using the experimental natural frequency (Figure 15), and the first modal shape of the bike frame was out of the plane (Z) with a natural frequency of 38.0 Hz (Figure 15). For the finite element model, the first natural frequency was 35.0 Hz (Figure 16). The difference between the experimental result and the finite element model was 7.9%.

This difference may be due to the difficulty of exactly modeling the supports and material properties, specifically at the fork and the joints. These results show


Table 4. Young's modulus from model calibration. Structural Evaluation of Bamboo Bike Frames: Experimental and Numerical Analysis DOI: http://dx.doi.org/10.5772/intechopen.89858

Figure 15. Experimental first modal mode.

that the model represents satisfactorily the real bike frame. Then, these results can be used to fatigue analysis using the finite element method.
