Expanding with heat and contracting with cold are common physical phenomenon in the nature. Variation in temperature
leads to corresponding variation in physical dimension of mechanical parts. The conventional theories and calculations
of thermal deformation are approximate and linear, can only be applied in normal or low precision field. The shortages
of conventional calculations are pointed out. According to the research results of many years, a theory is given that the
thermal deformation error of mechanical parts doesn't follow the conventional linear formula, it relates to all physical
dimension of the mechanical part, and the deformation can be indicated by a nonlinear formula of physical dimensions.
Studies on some common mechanical parts in precision technology have went on and the mathematical models have
been set up, cylindrical piece, hollow piece and sphere are included. The experimental results also make it clear that
these models are more logical than the traditional one. Because the sphere has only one physical dimension, so the
thermal expansion coefficient can be achieved by detecting the thermal deformation of the sphere, and this method is
more logical than the traditional method.
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