기하학적 공분산(Geometric Covariance)을 고려한 변형 조립체의 공차 해석

Existing sensitivity analysis have done with assumption of independency of the sources of variation. But if the number of welding points is increased, we can see that the assembly variation will increase. This phenomenon is explained because as the number of sources increases the welding points are getting closer to each other and the independency assumption becomes questionable. Intuitively, closer points over the same surface cannot move independently of each other. Moreover intuition shows that if the number of welds increase, the assembly variation should decrease because the stiffness of the assembly increase with the number of welds and the springback will be smaller. So it can be concluded that the covariance among the sources of variation plays an important role in predicting the assembly variation.