Study On Mechanical Properties Of Single-lapped And Single Bolted Joint Plate

In the field of aerospace and mechanical engineering,bolt connection is often used to combine two or more plates.But,due to some reasons,such as machining,heat treating,assemblage or working environment,the safe reliability of bolted joint plates are affected by many uncertainty parameters,such as the clearance of bolt hole,varying of pre-tighting force,the co-axial of bolt and hole.In order to investigate the effects of uncertainty parameters on the mechanical properties of bolted joint plate,such as,the stress level around bolt hole,the sliding stiffness and the mode frequency of system,a single-lapped and single bolted joint plate is used as the study object.First,the analytical model of stress around hole,the equivalent stiffness model in micro sliding phase,and the vibration mode equation of bolted joint plate were derived.And subsequently,the impact mechanism of bolt-hole clearance,value of pre-tighting force,and the misalignment of bolt on the stress level around hole,micro-sliding equivalent stiffness and mode frequencies of bolted plate were discussed qualitatively.Then,the ABAQUS soft package was used to develop a parametric finite element model for a single-lapped and single bolted joint plate with some uncertainty parameters through Python programming.The effectiveness of the model was verified via experimental data at the same time.Thereafter,the degree of effects of the bolt-hole clearance,the value of pre-tighting force and the degree of misalignment on the stress level around hole,the micro-sliding equivalent stiffness and the mode frequency were discovered in the end.Results indicate that the site of stress concentration around hole won't change by the influence of the size of bolt hole,the pre-tighting force and the misalignment of bolt.As the ratio of diameter of bolt hole and bolt shank is in from 1 to 1.3,the stress around hole at 0mm and 1.5mm position is decreased to 30%~40% by the increasing of diameter of bolt hole.As the ratio of diameter of bolt hole and bolt shank is in from1.1 to 1.2,the relation of stress level around hole and the diamerter of bolt shows as a parabola surface,and the stress level won't be changed by increasing the diameter of bolt hole.The relation of stress peak around hole depends on the nearless of bolt axial and the bolt-hole axial under misalignment condition.The stress around bolt hole is increased by increasing the pre-tighting force.As the diameter of bolt hole and bolt shank is in from 1 to 1.1,1.12 to 1.2 or 1.22 to 1.28,the equivalent stiffness increases with the incrasing of tranverse displacement if the micro displacement is smaller than0.035 mm.Otherwise,the equivalent stiffness decreases.The effects of misalignment on equivalent are very tiny.As the pre-tighting force is in from 0.15 to 0.33 or0.45~0.7 propotion to the maximum pre-tighting force which caused yield to the bolt,the effects of pre-tighting force is very small.Otherwise,the effects ratio might reach to 50%.As the ratio of diameter of bolt hole and bolt shank is in from 1.04 to 1.16,the effects of diameter on mode frequencies can be ignored.However,when the ratio of diameter of bolt hole and bolt shank is larger than 1.21,the effects of diameter of bolt hole on the mode frequency relies on the boundary condition.Finally,using the relation of uncertainty parameters and mechanical properties of bolted joint plate,an optimized design method of bolt-hole diameter by anti-vibration fatigue was proposed.An optimized design method for pre-tighting force via the connectiong rigidity was also proposed.The expected research results provide a new idea for dynamic and anti-vibration fatigue design of bolted joint plate.