An experimental investigation is presented for the stress distributions in functionally graded plates containing a circular hole. On the basis of the authors’ previously constructed theoretical model, two kinds of graded plates made of discrete rings with increasing or decreasing Young’s modulus were designed and fabricated in virtue of multi-material 3D printing. The printed graded plates had accurate size, smooth surface, and good interface. The strains of two graded plates under uniaxial tension were measured experimentally using strain gages. The stresses were calculated within the range of linear elastic from the measured strains and compared with analytical theory. It is found that the experimental results are consistent with the theoretical results, and both of them indicate that the stress concentration around the hole reduces obviously in graded plates with radially increasing Young’s modulus, in comparison with that of perforated homogenous plates. The successful experiment in the paper provides a good basis and support for the establishment of theoretical models and promotes the in-depth development of the research field of stress concentration in functionally graded plates.

The out-of-plane bending problems of functionally graded thin plates with a circular hole are studied for two-dimensional deformations. The thin plates have arbitrary variations of elastic properties along the radial direction. The general solutions of the stresses and moments are presented for the plates subjected to remote bending moments based on the theory of complex variable functions. Two different cases—a whole functionally graded plate with a circular hole and a functionally graded ring reinforced in a homogeneous perforated plate—are considered by numerical examples. The influence of parameters like Young’s modulus and Poisson’s ratio, function types of these elastic properties, and width of the reinforcing ring on the moments around the hole is presented. It is shown that the moment concentration, caused by the geometric discontinuity of the hole in the traditional homogeneous plate, can be well relieved or even eliminated by careful selection of the above parameters. The results for some special cases are compared with previous literatures and are found in good agreement.

Experiments were conducted on the pressure drop fluctuations of R245fa boiling through a horizontal microchannel with a diameter of 0.94 mm and a heated length of 170 mm at various gravity levels. The visualization results show that under inlet saturation conditions, three typical periodic oscillation modes are observed: continuous two-phase flow, bubbly/annular alternating flow, and churn/annular alternating flow. The flow oscillation characteristics within the channel are closely related to bubble dynamics, the vapor–liquid interface evolution, and the upstream compressible vapor volume. It has also been found that increasing the mass flux or decreasing the heat flux can enhance the suppression effect on pressure drop oscillation. In addition, under inlet subcooling conditions, although the total pressure drop increases with the increase in gravity level (1–2.78 g), and the amplitude of pressure drop fluctuation first increases and then decreases with the increase in gravity level, with the transition point occurring approximately at an = 1.10 g. The impact of gravity level on the amplitude of pressure drop fluctuation is primarily determined by the relative dominance of bubbly flow and annular flow within the channel.