Method for predicting fatigue life of adhesive joint in full-service temperature interval

Abstract

The invention discloses a method for predicting the fatigue life of an adhesive joint in a full-service temperature interval, and the method comprises the following steps: 1, building a function thatthe failure strength changes along with the temperature after the quasi-static failure strength of the adhesive joint at different temperatures is measured in the full-service temperature interval ofa vehicle body; 2, determining the fatigue loading frequency of the bonding joint; 3, carrying out fatigue tests on the bonding joint at different temperatures, and establishing S-N curve functions atdifferent temperatures after obtaining the maximum stress in the cyclic stresses with the specified service life at different temperatures; 4, fitting fatigue parameters in the S-N curve functions atdifferent temperatures into a function related to the test temperature, further obtaining a stress amplitude-temperature-fatigue fracture cycle life fitting function, and fitting the stress amplitudetemperature fatigue fracture cycle life fitting function into a T-S-N fatigue performance curved surface; and step 5, obtaining dangerous point stress during quasi-static stretching of the joint according to the temperature influence factor, judging a corresponding external load cycle characteristic value in the actual joint fatigue life to be predicted, and finally obtaining the actual cycle life of the bonded joint according to the T-S-N fatigue performance curved surface.

Description

technical field [0001] The invention relates to the technical field of fatigue performance testing of bonded joints, in particular to a method for predicting the fatigue life of bonded joints under a full service temperature range. Background technique [0002] Vehicles are subjected to dynamic alternating loads from many aspects during driving, which makes the body bonding structure prone to fatigue damage during long-term service, which seriously affects vehicle safety. At the same time, during the actual operation of the vehicle, the bonding structure of the vehicle body is often affected by factors such as temperature, humidity, salt spray, and ultraviolet rays. Different environmental factors have a greater impact on the performance of the bonding joint. Considering that sealants and coatings can be used to effectively reduce the influence of humidity, salt spray and ultraviolet rays, temperature has become the most important factor affecting the performance of bonded s...

AI Technical Summary

Problems solved by technology

[0003] When studying the force of the adhesive in the actual structure, since the force analysis of the entire bonded structure cannot be carried out in the actual experiment, the force of the adhesive in the actual structure can only be simulated through the bonded joint

The main shortcomings and deficiencies of the current bonded joint fatigue test device are: the existing fatigue loading device can only apply loads in the shear direction and tensile direction to the bonded joint, and cannot make the bonded joint bear pressure, so the existing fatigue The device can only apply a cyclic load with r>0; the existing fatigue device is sensitive to non-axial load, and the specimen is easy to bear the non-axial load; when the existing fatigue device performs fatigue work on the specimen, the specimen stretches It is easy to shake and has a great impact on the life of the loading device; the existing fatigue loading device and test method are mainly aimed at normal temperature conditions, and the influence of temperature is not fully considered; the existing fatigue loading device can usually only load a single specimen; the existing The fatigue loading device can only load a single specimen, and the efficiency is low; the existing fatigue performance test method cannot realize the fatigue life prediction under any stress range within a certain temperature range under any cycle characteristics

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