Test piece for implementing biaxial tension-compression coupling stress state through uniaxial tension

[0016] The present invention provides a test piece that realizes a two-way tension-compression coupling stress state through unidirectional stretching. The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0017] Fig. 1(a) is a top view of the test piece of the present invention; Fig. 1(b) is a cross-sectional view of the A-A surface of the test piece of the present invention. The material of the test piece is low carbon steel, the outer contour is octagonal, and the length of the long axis is L1=150mm, the length of the short axis is W1=80mm, and the length of the side parallel to the long axis is L2=30mm, which is parallel to the short axis. Side length W2=30mm; two circular holes are set symmetrically at both ends of a longer central axis of the test piece, which are used to load the fixture of the tensile testing machine. The distance between the center of the circular hole and the side parallel to the minor axis is D1 =20mm, hole diameter Φ2=7mm; 4 smooth transition holes are symmetrically arranged on the central area of ​​the test piece, so that the central part of the test piece presents a cross shape, and the distance between the center of the four holes and the two axes of the test piece is D2 =15.5mm, hole diameter Φ1=25mm, chamfering radius R=2mm; the upper and lower surfaces of the cross in the central area of ​​the test piece are thinned by grinding, the thickness of the test piece is t1=4mm, and the thickness of the central area t2= 2mm, the distance from the two opposite sides of the center area to the center point of the test piece is equal, the vertical distance from the boundary of the center area to the center point of the test piece is 6mm; the surface of the center area of ​​the test piece and the four cross support arms connected to it are connected by a slope transition , The angle of the inclined plane is 14°.

[0018] During the test, the two ends of the test piece are loaded on the clamps of the unidirectional tensile testing machine, and the testing machine applies tensile force, and the central part of the test piece realizes the stress state of two-way tension-compression coupling. The strain of the center cross can be measured by attaching a strain gauge, and the stress and strain of the central tension and compression working area can also be given by the results of finite element simulation calculation.

[0019] This example gives the results of stress distribution at the central tension-compression coupling part obtained by finite element simulation. figure 2 This is a grid division diagram when using finite element software to perform stress analysis on the specimen of the present invention. A displacement load was applied to the circular holes at the left and right ends of the specimen, the size was 4mm, the loading time was 0.8ms, and the unit was a solid unit. image 3 It is a graph showing the variation curve of each stress component of the cross section of the test piece in the central area of ​​the present invention with the loading displacement. It can be seen that the curve of the tensile stress and the compressive stress with time is basically symmetrical about the S=0 line, and both The absolute value is not much different, the shear stress change curve is always close to the straight line S=0, and the size is basically 0, which can be ignored. Figure 4 It is a graph of the variation curve of each strain component of the cross section of the test piece central area according to the present invention with the loading displacement. Figure 4 The stress changes are the same.