工装对前端模块约束模态试验影响分析

Analysis of the Influence of Tooling on Constraint Modal Test of Front End Module

针对某主机厂生产的轿车前端模块在约束模态试验中所测频响函数稳态极点不清晰、模态置信度(Modal ssurance riterion,MAC)较差问题,采用有限元仿真及实测相结合的方法,分析前端模块模态特性,找出影响前端模块约束模态试验结果的原因。改进工装设计,加强工装与前端模块间的约束刚度,实测模态及理论计算所得模态互相对照,有效提高有限元模型的可信度,据此模型计算出不同工装约束刚度对约束模态试验结果的影响程度。试验结果表明:增加工装约束刚度能有效提高前端模块约束模态试验结果准确性,不仅各阶模态独立性更高,实验数据与有限元分析结果也更接近,从而验证了工装约束刚度对前端模块约束模态试验的影响,对约束模态试验工装设计具有参考意义。

The constraint modal characteristics of the front end module of a car are analyzed by means of finite element simulation and experimental test. The factors influencing the test results are found. The tooling design is improved and the constraint stiffness between the tooling and the front end module is strengthened. The test modals and the simulated modals are mutually compared and the reliability of the results of the finite element simulation is effectively raised. Based on the finite element model, the influence degree of different tooling constraint stiffness on the constraint modal test results is calculated. The results of the restraint stiffness test show that increasing the tooling constraint stiffness can effectively raise the accuracy of the test results of the front end module’s constrained modal, make the modals of different orders more independent and make test results and simulation results closer. Thus, the influence of the tooling constraint stiffness on the constrained modal test results is verified. This paper has a reference significance for the constrained modal test tooling design.