端面摩擦对玻璃压缩强度的影响

为了研究端面摩擦对玻璃压缩强度的影响,采用铜箔和凡士林对压缩接触面进行减摩处理,使用MTS试验机对钠钙硅玻璃样品进行应变率为10^-4 s^-1的准静态压缩试验,利用高速摄影记录了试件的破坏过程,进一步分析了玻璃强度的统计分布规律。试验结果表明:玻璃样品的接触面只有凡士林时,在压缩过程中出现显著裂纹及部分表面碎片脱落;玻璃样品在接触面加入铜箔后再涂凡士林,整个压缩过程受力均匀,未出现显著裂纹或碎片脱落,呈现为理想的均匀压缩状态。端面摩擦力的降低导致玻璃压缩强度的显著降低,这主要是因为减小摩擦力使试样端部所承受的横向约束变弱,试样处于更加接近单轴应力的状态,一定程度上减少了围压引起的强化效应。

Effect of End-Face Friction on Compression Strength of Glass

In order to study the effect of end-face friction on the compression strength of glass, copper foil and vaseline were used to reduce friction on the compression contact face. Quasi-static compression tests at the strain-rate of 10^-4 s^-1 were carried out on soda-lime-silica samples using the MTS testing machine. High-speed photography was used to record the failure process of the glass samples. The statistical distribution of glass strength was further analyzed. The experimental results show that when the contact surface of the glass sample is only lubricated by vaseline, the significant cracks and surface fragments fall off during the compression process. After the copper foil is added to the contact surface of the glass sample, the force is uniform throughout the compression process, and no significant cracks or fragments fall off. The decrease of the friction force of the end-face will lead to a significant decrease in the compression strength of the glass, mainly because reducing the friction force weakens the lateral restraint on the end of the specimen, and the specimen is in a state closer to uniaxial stress, which largely avoids the strengthening effect caused by confining pressure.