Therefore, the root of the incision is the uniaxial tension state, and the maximum tensile stress is equal to the first

principal stress. The theory of maximum tensile stress considers the main reason for the brittle fracture is that the maximum tensile stress reaches the ultimate tensile stress when the material is uniaxial stretched.

In all the models, the minimum

principal stress (FRD: -2.025 MPa, screwed-FRD: -1.627 MPa, TFBC: -1.525 MPa, and screwed-TFBC: -1.074 MPa) in the buccal neck of the first upper molar is more active; hence, the compressive stress is observed in the buccal of the first upper molar teeth.

In fact, many studies have shown that the magnitude and direction of the

principal stress can be obtained by the formula transformation based on knowing the normal stress of three different cross sections.

These two theories are based on the Mohr-Coulomb (M-C) criterion without considering the intermediate

principal stress.

Von Mises analysis was used to assess the stress distribution in implant/abutment/crown, whereas the cortical bone tissue was evaluated using maximum

principal stress and are distinguished between tensile stresses (positive values) and compressive stresses (negative values).

As we can see from Figures 13 and 14, for both covered layer and original surface layer, the

principal stress curves almost coincide with the Y-direction stress curves, which means that the maximum

principal stress of ACCSSPS is in the longitudinal direction.

Figure 6a presents the simulation results of maximum first

principal stress during the process.

By means of von-Mises criteria, the figures of material failure stress, the maximum shear stress and maximum

principal stress are shown in Fig.

Biaxiality indication is defined as the

principal stress smaller in magnitude divided by the larger

principal stress with the

principal stress nearest zero ignored.

He led the first quantitative study describing the direction of the major

principal stress in soil as it is traversed by tractor tires.

The effect of this parameter can be observed in Figure 5, which shows the difference in the maximum

principal stress values calculated along the alignment at two points on either side of the discontinuity.

The results show that the changes of maximal displacement are less than a 0.1%, whereas for the maximum

principal stress is less than 2.5%, demonstrating the adequacy of the used mesh.