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在三维空间中,常规应变状态由3个正应变和3个剪应变来描述。因此,确定一点的应变状态至少需要6个应变测试元件。基于应变状态理论,设计了一种能测试混凝土、岩土等材料内部应变状态的接触式三维应变花。该测试装置的核心由6个常规应变片组成,且应变片的布置需要满足特定条件。根据任一方向上线应变与常规应变表示方法中三维应变各分量之间的关系,建立了三维应变花各测试数据与常规应变之间的转换矩阵。进一步给出了求解该问题的必要条件,并进行了误差分析。考虑施工便利性要求,着重阐明了直角式三维应变花和正四面体式三维应变花的应变片布置方式,并给出了对应的计算方法。两种三维应变花的自身测试和对某试样应变状态的测试表明,该方法可对混凝土、岩土等材料内部的三维应变状态进行测试。
In three-dimensional space, the normal strain state is described by three normal strains and three shear strains. Therefore, a minimum of 6 strain test elements are required to determine a little strain. Based on the theory of strain state, a contact three-dimensional strain flower was designed to test the internal strain state of concrete, geotechnical and other materials. The core of the test device consists of six conventional strain gauges, and the strain gauges are arranged to meet specific conditions. According to the relationship between the on-line strain in any direction and the components of three-dimensional strain in the conventional strain representation method, the transformation matrix between each test data of three-dimensional strain flow and the normal strain is established. The necessary conditions for solving the problem are further given and the error analysis is carried out. Considering the requirements of construction convenience, the arrangement of strain gauges of right-angled three-dimensional strain flower and tetrahedron three-dimensional strain flower is emphatically explained, and the corresponding calculation method is given. The tests of two kinds of three-dimensional strain flower and the test of the strain state of a sample show that the method can test the three-dimensional strain state in concrete, geotechnical and other materials.