Introduction and analysis of bolt tensile test

The bolting test is carried out on the tensile test of the two-dimensional woven fabric reinforced composite material with reference to the national standard GB1447-83. The experiment was carried out on a Shimadzu AG-250KN universal material testing machine in Japan. The computer controlled test machine automatically collects data and processes it. The stretching rate of the machine was set at 2 mm/min, the ambient temperature during the experiment was 22 e, and the relative humidity of the atmosphere was 65%. There were 4 sets of 20 samples in the experiment. After the stretching is completed, the connecting plate is disassembled, and it is found that the edges of the holes are crushed and broken. This is because tensile or shear failure occurs rapidly and expands, and extrusion failure is gradually developed. It may not have a significant reduction in the load carrying capacity of the connecting plate. The three main forms of destruction may exist in the same connection area.

Experimental results The strength of bolted laminates is not only related to the characteristics of the composites and the layup parameters. The clamping force of the bolts, the size of the gaskets and the material factors of the bolts have a greater influence on the strength, while the bolts are on the board. The lateral pressure has the greatest influence on the compressive strength, and the lateral pressure constrains the expansion of the crushed damage zone. The clamping force of the gasket to the plate can increase the overall strength of the composite. Collings studied the HTS/914 laminates, comparing the finger-tightened bolted plates with the higher-bolt lateral tensioning plates obtained with wrenches and found that the latter increased the extrusion strength by about 30% compared to the former; Crews It was found that in the case of the T300/5208 anisotropic plate, when using the 5.65N#m bolt lateral preload, the extrusion strength was 33% higher than that using the hand screw, and 10% higher than the 2.825 Nm. Due to the mutual squeezing, the upper and lower sides are displaced, that is, the obvious bulge. Therefore, the contact of the bolt with the connecting plate is actually a three-dimensional distribution problem of stress. Although many researchers have studied and analyzed this problem, there is no ideal model combined with three-dimensional stress analysis to satisfactorily predict the strength of the connecting plate.

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