Experimental study to investigate the structural integrity of welded vehicle structure for BSR (Buzz, Squeak, Rattle) noise by vibration measurement

진동 특성을 이용한 접합된 차량 구조의 BSR(Buzz, Squeak, Rattle) 소음 강건성 관측에 대한 실험연구

Abstract

In this study, the vibration test method to nondestructively evaluate the possibility of vehicle BSR (Buzz, Squeak, Rattle) noise generation in spot-welded structures was proposed. The weld quality was predicted by analyzing the local vibration transmission characteristics for the beam-shaped structure attached to testing spots. The bending stiffness was evaluated from the identified vibration properties. From the change in the stiffness, the weld quality was evaluated. For verification of the proposed method, the welded specimens were fabricated with partial changes in welding parameters. The local vibration transfers were measured. The frequency bands affected by the weld quality was identified. The capability of evaluating the welding parameters including defect position and quality variations was investigated. The proposed method enables fast quality evaluation to minimize the possibility of BSR noise generation in the manufactured vehicle.

차량 점용접 부위에서 BSR(Buzz, Squeak, Rattle) 소음 발생 가능성을 국부 진동을 사용하여 비파괴적으로 추정하는 진동기반 계측법을 제시한다. 용접부에 부착된 구조물에 의한 점용점 부위의 국부적인 진동을 유발하고 진동전달 특성을 파악한다. 관측된 진동 특성으로부터 국부 구조의 굽힘강성값을 도출하였다. 강성값의 변화로부터 점용접의 상태 강건성을 파악하였다. 제시되는 방법의 검증을 위해 부분적으로 용접품질이 변화된 시편을 제작하였다. 제작된 시편에서 계측된 진동 특성을 분석하였다. 용접 강건성에 의해 변화하는 특정 주파수 대역을 파악하였다. 구조별, 위치별 계측을 통해 제시된 방법으로 분별이 가능한지 검증하였다. 국부 진동 평가방법은 구조물의 용접 강건성을 생산 현장에서 파악하게 하는 평가방법으로써 BSR발생 가능성을 저감하기위한 생산 품질 확보에 사용될 수 있다.

Fig. 1. Experimental setup for measuring vibrations occurred by the generation of BSR noise. Two types of welded specimens were fabricated with different number of missing joints. (a) The specimens without and (b) with missing welded joints.

Fig. 2. Measured vibrations of two types of spot-welded specimens when the 5 Hz harmonic vibration was applied on the specimens.

Fig. 3. Parameters and experimental setup for measuring vibrations using the attached structure. The welding currents at ζ₇ were controlled from 0 to 10 kA. All spot welds except for the weld at ζ₇ were performed with a welding current of 7 kA.

Fig. 4. Measured vibration responses using the attached structure. (a) Attached on a rigid body and (b) attached on the welded structure.

Fig. 5. Measured vibration responses according to attached locations (ζ_D) when the welding current at ζ₇ was (a) 7 kA and (b) 0 kA. The frequency shifting in the specific band occurred only at the vibration response on the defected spot (ζ_D = 0.6).

Fig. 6. The measured vibration responses at ζ_D = 0.6 according to welding currents from 0 to 10 kA. Only the frequency band in the shaded section varied with the welding currents.

Fig. 7. The measured bending stiffnesses with the welding currents. The estimated bending stiffness of welded joints was closer to that of a 2 mm thickness as the welding current increased.