Study On The Fatigue Test Method Of Loader Boom

In recent years,with the pace of development of the domestic economic slowdown and the reduction of infrastructure construction,loader demand growth rate also fell,The focus of loader production enterprises from the past production and sales volume to quality,in order to enhance their competitiveness.From the use of experience,the main problem of the domestic loaders are their low reliability.As one of the pivotal parts of the loader,the working device is prone to occurs fatigue failure under the condition of long-term random load,and among them,the fracture of the boom is the most common,which seriously affects the performance and service life of the whole machine.Therefore,it is necessary to study a method acquiring the load spectrum of the boom and testing it's fatigue property use the load spectrum.This paper takes ZL90 loader as object,mainly studies the testing method of load spectrum and the calculation method of the equivalent external load.In the test of boom load spectrum,two methods of measuring the load spectrum of the boom are proposed,which are the pin shaft sensor method and the boom strain gauge method.In the pin shaft sensor method,the force analysis of the loader bucket is carried out,and the working principle and design method of pin shaft sensor,connecting rod sensor and lateral force sensor are discussed in detail,the calibration tool and calibration method of pin shaft sensor is designed,the relevant parts of the bucket is reconstructed,and the strength of which is checked.The boom strain gauge method in which describe the measuring principle of this method,designed and made a boom model and tested it in order to check feasibility of the method,finally,a calibration program of real boom is established.In the calculation of the equivalent external load: according to the parameters of each part of the working device,the coordinates of each hinge point are calculated by geometric method.Based on the force measured by the sensor,the force of each boom hinge point in the geodetic coordinate system is calculated and converted into the boom coordinate system,in which the time history of the neutrosphere bending moment of the boom is made,and then calculate the equivalent bending moment diagram of the boom.Under the excavation posture of the working device,the equivalent load of the boom is obtained according to the equivalent bending moment diagram,and educe the equivalent external load should be bear on bucket when the fatigue test is carried out,finally,the fatigue test scheme of boom is designed base on the equivalent external load.