工程现场或实验室中,为了测量力学构件某点的剪应力,常常要在构件被测点粘贴直角和45°电阻应变片（即应变花）。根据实验应力分析的电测原理和平面应力分析,可知道若测量得0°、45°、90°三个方向的线应变分别为ε_(0*)、ε_(45*)、ε_(90*),则该点的剪应力为: τ_(xy)=E（ε_(0*)+ε_(90*)-2ε_(45*)）/2（1+μ）式中E为构件的杨氏弹性模量,μ为构件的泊松比。 通常的测量方法是:另外选取一块与构件相同的材料,贴上一片相同规格的电阻应变片,作为公共温度补偿片使用。具体测量时,需在电阻应变仪上接成图1现示的三个测量电 Engineering site or laboratory, in order to measure the mechanical components of a point of shear stress, often points to be measured at the component paste the right angle and 45 ° strain gauges (ie, strain flower). According to the principle of electric measurement and plane stress analysis of the experimental stress analysis, it can be seen that the linear strain in the three directions of 0 °, 45 ° and 90 ° are ε_ (0 *), ε_ (45 *) and ε_ (90 * ), The shear stress at this point is: τ_ (xy) = E (ε_ (0 *) + ε_ (90 *) - 2ε_ (45 *)) / 2 Elastic modulus, μ is the Poisson’s ratio of the member. The usual method of measurement is: In addition, select a piece of the same material as the component, affix a piece of resistance strain gauge of the same specification, and use it as a common temperature compensation piece. Specific measurement, the resistance strain gauge to be connected as shown in Figure 1 shows the three measurement of electricity