新型单轴拉伸试样制备装置的研制及试验研究

Development and Experimental Research of Sample Preparation Device for New Uniaxial Tensile Specimen

针对单轴拉伸试验中试样形式与拉伸段长度对试验结果影响程度较大,以及目前在该试验中所采用试样形式与拉伸段长度均存在较大差异的问题,研制一组可以制备不同拉伸段长度哑铃状单轴拉伸试样的制样模具;在此基础上,对黏性土试样进行单轴拉伸试验,探讨了黏性土的抗拉特性,以及试样形式与拉伸段长度对其破坏形式、抗拉强度与峰值位移的影响情况。研究结果表明:哑铃状试样可避免拉伸过程中出现的端部松弛与应力集中问题,拉伸断裂面发生在有效拉伸长度范围内;黏性土的破坏形式不是纯脆性破坏,而是在抗拉强度后存在一个软化阶段;抗拉强度随拉伸段长度的增大而减小,峰值位移随拉伸段长度的增大而增大,二者均与拉伸段长度呈对数关系。

For uniaxial tension test result can be largely affected by sample forms and tensile length,both of which are quite different in the current experimental research. A set of dumbbell uniaxial tensile sample preparation mould was developed for preparing samples with different tensile lengths. Sample preparation mould consisted of two horizontal loading section moulds,two vertical stretching section moulds and one sample preparation base plate,in which loading section moulds were connected with stretching section moulds by dovetail slot. Based on this,the uniaxial tensile test of clay specimen was carried out to analyze the tensile properties of clay and discuss the influence of sample forms and tensile length on the failure mode,tensile strength and peak displacement. The results showed that end relaxation and stress concentration issues can be avoided in the tensile process for applying dumbbell specimens and the tensile fracture plane occurs in the range of effective tensile length; failure mode of clay is not pure brittle failure,but there is a softening phrase after tensile strength. With the increase of tensile length,uniaxial tensile strength decreases but peak displacement raises,and both show a logarithmic relation with tensile length.