压缩应力下石墨IG-110热膨胀系数的测量及验证

采用应变电测法测量压缩应力状态下石墨IG-110的热膨胀系数,分析不同压缩应力对IG-110热膨胀系数的影响.结果表明,压缩应力对IG-110的热膨胀系数影响显著.与未加载时相比,分别加载20、30、40 MPa压缩应力石墨试样平行加载方向的平均热膨胀系数由3.71×10~(-6) K~(-1)逐渐增大至4.20×10~(-6)、4.41×10~(-6)、4.78×10~(-6) K~(-1),分别提高约13.2%、18.9%和28.8%;而垂直加载方向的平均热膨胀系数则由4.03×10~(-6)K~(-1)逐渐减小至3.80×10~(-6)、3.79×10~(-6)、3.75×10~(-6)K~(-1),分别降低约5.7%、6.0%和6.9%.压缩应力状态下石墨热膨胀系数的变化可能与应力导致石墨内部微裂纹的张开和闭合有关.

Measurement and Validation of Coefficient of Thermal Expansion of Graphite IG-110 under Compressive Stress

Coefficient of thermal expansion (CTE) of nuclear graphite IG-110 under compressive stresses was measured with the strain gauge method, and the corresponding effects of stresses on the CTE of IG-110 were analyzed. Results indicate that the strain gauge method is feasible and reliable in the CTE measurement of IG- 110. Compressive stresses have significant effects on the CTE of graphite IG- 110. Compared with those of the unloaded specimens, CTE parallel to the loading direction of specimens increases from 3.71 × 10~(-6) K~(-1) to 4.20×10~(-6) K~(-1), 4.41×10~(-6) K~(-1) and 4.78×10~(-6) K~(-1) for compressive stresses of 20, 30, 40 MPa which increases by about 13.2%, 18.9% and 28.8%, respectively. Meanwhile, CTE perpendicular to the loading direction de-creases from 4.03×10~(-6) K~(-1) to 3.80×10~(-6)K~(-1), 3.79×10~(-6)K~(-1) and 3.75×10~(-6) K~(-1) which decreases by around 5.7%, 6.0% and 6.9%, respectively. CTE changes of nuclear graphite under stresses are probably due to the opening or closure of micro-cracks induced by stress in graphite.