| As an important bearing structure,siding and web structures are widely used in various fields.Due to the requirements of the process or structural design,it is necessary to open the wall or the web.For example,in the process of aircraft design,in order to meet the needs of weight reduction,maintenance,pipeline passage,etc.,it is necessary to open holes in the wall panel.However,the opening of the hole causes stress concentration at the edge of the hole,causing a change in the strength of the structure,and fatigue damage occurs at the opening.Strengthening the edge of the structure is a common solution to reduce stress concentration.However,there are few studies on the enhanced form,often relying on experience,and no detailed inquiry.Therefore,it is of great value to explore the impact of enhanced forms on fatigue life.In this paper,the accuracy of fatigue life prediction method is verified by experimental results through the combination of experimental analysis and finite element analysis.The effect of the shape and size of the reinforced form on the fatigue life is analyzed by the fatigue life prediction method.(1)Digital image correlation experiment and establishment and verification of finite element analysis model for reinforcements of web with openings.Firstly,a variety of typical open-web specimens with different reinforcement structures were designed and processed.The digital image correlation method is used to obtain the displacement and strain distribution of specimens with different reinforcement forms under static load.Then the finite element analysis method is used to obtain the displacement and strain distribution of the specimen under static load.The finite element analysis and the digital image correlation method are used to compare the displacement contours and the strain contours.The trends and size are same,which indicates the accuracy of the finite element analysis model.Through the finite element method,the stress contours of different reinforcement forms are obtained,and the stress concentration factor of the hole edge is calculated.Comparing the stress concentration factor with the crack initiation life of the member,it is known that the stress concentration factor reflects the crack initiation life of the test piece.(2)Fatigue test and fatigue life prediction method verification of reinforcements of web with openings.The fatigue life of the specimens of different reinforcement forms was obtained by fatigue test.It can be found through experiments that different reinforcement forms have a great influence on fatigue life.For the specimens of the same reinforcement form,the crack propagation rate is linear with the crack length at the double logarithmic coordinates of the crack growth rate.At the same time,through the fatigue test results,the crack initiation life of the test piece was compared,and the stress concentration factor of the hole edge was verified to reflect the crack initiation life.With the help of Franc3 D software,a fast and efficient solution for calculating the crack propagation life is realized by prefabricating the initial crack on the model.With this scheme,the crack propagation life of the hole-type bosses with different reinforcement forms is analyzed,and compared with the results of previous fatigue tests,the accuracy of the scheme is verified.In the process of calculating the crack propagation life,the stress intensity factor at the crack tip and the change with the crack propagation were analyzed.(3)Analysis and optimization of the influence of shape and size of reinforcements of web with openings on fatigue life.By means of the finite element method for analyzing the fatigue life,the effects of the width and height of the reinforcement form on the fatigue life of different reinforcement forms were analyzed.A graph of the effect of width and height of different reinforcement forms on fatigue life is obtained.Afterwards,the effects of different forms of reinforcement on fatigue life were observed when the reinforcement forms had the same volume or the same cross-sectional area.It was found that the bilateral reinforcement form has a lower stress concentration factor,and the bilateral reinforcement form has a higher The conclusions of crack initiation life and high crack growth life are of great value for guiding people to design fatigue life. |
