成熟期油菜角果角裂极限应力的试验测定

Limit stress at corner cracking of rape's pod in mature period measured by mechanical test

利用微机控制万能材料试验机、扭转试验机、静态数字应变仪等测定油菜品种油利6号、早熟420、湘杂油1613成熟期角果切变模量及角裂极限应力。将油菜角果简化为各向同性线弹性材料,通过拉伸试验测定角果的弹性模量、泊松比,得到其切变模量;通过角果的扭转结合电测应变试验,测量出角裂时的2个主应变,利用平面应变理论得到角裂时的极限切应变,分析计算得到角果角裂极限切应力。结果表明:成熟期油菜角果含水率8%~10%,成熟度95%~98%油利6号角果切变模量约为116 MPa,角裂极限应力为0.180 MPa;早熟420、湘杂油1613切变模量分别为137 MPa和142 MPa,角裂极限应力分别为0.213 MPa和0.221 MPa。

Shear modulus and corner limit crack stress of matured pod corner for Youli6, Zaoshu420, and Xiangzayou1613 was measured by using microcomputer controlled universal material testing machine, torsion testing machine, and the static digital strain gauge. The rape pod is simplified as isotropic linear elastic material. The elastic modulus and poisson＇s ratio was measured by the tensile test to determine the shear modulus. Two principal strains at the corner cracking were measured by torsion combined with electrical strain test. Using plane strain theory, the limit shear strain at the corner cracking was obtained to calculate the limit shear stress. The results showed that the water content of rape was 8%–10% in the matured period. The shear modulus of Youli6 was about 116 MPa, and the limit stress at corner cracking was 0.180 MPa. The shear modulus of Zaoshu420 and Xiangzayou1613 was 137 MPa and 142 MPa, and the limit stress at corner cracking was 0.213 MPa and 0.221 MPa, respectively.