Abstract
Research and/or Engineering Questions/Objective
Cohesive Zone Model (CZM) is well used material model for adhesion in adhesively bonded structures. To apply this feature for crash simulation of automobile applications, high strain rate property of adhesion is required. However the current standard tests of adhesion are conducted under the quasi-static condition. In this study, high strain rate properties were acquired by newly developed method corresponding to dynamic loading. These properties were applied to the crash simulation of adhesively bonded T-Joint structure with CZM, and it showed the good agreement with T-Joint test results.
Methodology
Acquiring the high strain rate CZM parameters for adhesion is difficult from standard test methods (DCB, ENF and MMB) because of their configurations, so the new test method was developed to correspond to the dynamic loading. This newly developed method was designed to apply dynamic tension and torsion load simultaneously with variable ratio to the cylindrical specimen. High strain rate CZM parameters were identified by using the virtual cylindrical specimen of newly developed method. Stress-displacement diagram acquired from this simulation was compared to that of actual test, and the CZM parameters were adjusted repeatedly until these stress-displacement diagrams are matched. Those identified CZM parameters were applied to the simulation of T-Joint structure.
Results
Comparison between the drop weight experimental results and that of the simulation results in aluminum T-Joint structure was conducted. CZM parameters were performed as “quasi-static” and “high strain rate” in this comparison. From these results, the influences of the strain rate were presented in the force-stroke diagrams and the destruction process. This comparison showed that the accuracy of the simulation about the destructive mode and the force-stroke characteristic of the whole structure are affected by the destruction process of bonded area. Namely, the high strain rate CZM parameters which can precisely predict the destruction process are much effective to simulate the crash phenomenon of adhesively bonded structure.
Limitations of this study
In this study, two CZM parameters namely "quasi-static" and "high strain rate" has been used to show the difference of strain rate clearly. However the CZM parameters have to be changed continuously according to the strain rate at each adhesive location, so the methodology of acquiring the CZM parameters under various strain rates and applying the properties to the simulation continuously are needed in next step.
What does the paper offer that is new in the field including in comparison to other work by the authors?
Application example to the aluminum T-Joint structure with high strain rate CZM parameters acquired from newly developed method is new for confirmation of practicality.
Conclusions
In the crash simulation of adhesively bonded structure, more accurate destruction process of adhesive area is important to improve the accuracy. High strain rate CZM parameters contribute to this accuracy.
KEYWORDS : Crash simulation, Adhesion, Cohesive Zone Model (CZM), Strain rate dependency