On-line nondestructive inspection techniques for lightweight automotive structures

摘要

The ability to ensure the integrity of lightweight structures is essential for increased use of aluminum, magnesium, composites, and other lightweight materials in automotive applications. Fast, reliable, robust inspection techniques are necessary to confirm product quality and reliability, and gain consumer acceptance. While automobile manufacturers have extensive experience in joining steel and ensuring the integrity of spot-welded steel structures, the industry has much less experience in joining dissimilar and lightweight materials, which are usually joined with adhesive. Development of nondestructive evaluation (NDE) methods is particularly critical for inspection of these adhesive-bonded joints, which cannot be inspected using destructive techniques or conventional pry tests. It is also more difficult to build in a safety factor for adhesive joints than for spot-welded joints; in many conventional steel applications, using a large number of "redundant" welds is a cost-effective means of achieving an acceptable factor of safety. The research described here is being performed as part of the Partnership for a New Generation of Vehicles (PNGV) between the United States Government and the U. S. Council for Automotive Research (USCAR). USCAR is the umbrella organization of Daimler Chrysler, Ford, and General Motors formed in 1992 to strengthen the technology base of the domestic auto industry through cooperative, pre-competitive research. The goal of PNGV is to develop technology that can be used to create low-emission vehicles with triple the fuel efficiency of today's vehicles, without impacting affordability, performance, or safety. Two other primary objectives of the program are to significantly improve national competitiveness in automotive manufacturing, and to apply commercially viable innovation to conventional vehicles. NDE has consistently been identified as a critical issue at PNGV workshops convened to determine basic research needs to meet PNGV's goals. For manufacturing applications, the need is for on-line, production capable, nondestructive test methods effective with only limited access to parts and available at reasonable cost. Manufacturers have specifically called for NDE methods to perform real-time diagnostic analysis; ensure product quality, consistency and performance; minimize variation in material properties due to processing variation; perform rapid and inexpensive on-line inspection of joints and bonds; and monitor production processes.