Application of reliability growth techniques in conjunction with DfR framework to validate heavy truck design

Why have the recalls and field campaigns in the automotive industry been going up over the years despite the strong development of technical knowledge, tools and techniques to design products that meet higher reliability standards? One explanation that stands out and is broadly accepted in the industry is related to the challenge to effectively deal with rapid growth of uncertainties in the product development environment brought mainly by the new customers’ demands, stricter safety and emission regulations, shorter project budget and duration. To deliver trucks that meet new market demands with high reliability, the truck industry has been incorporating in their classic product development process a framework of supporting process to ensure that truck components and systems will be designed to meet the reliability requirements, this framework is known as DfR (Design for Reliability). The most recent version of DfR framework was suggested in 2008 by Mettas and encompasses 6 major process steps as follow: Identify, Design, Verify, Analyze Validate and Control. The focus of this study resides in two steps of this process: Verification and Validation. verification is basically the quantification of reliability and validation is to demonstrate if the target will be met with certain level of statistical confidence by the time the truck mass production starts. The reliability method applied in a case study of a new truck project is based on Crow - AMSAA -NHPP model (L. H. Crow,1974) and it is known as Reliability Growth. This method allowed us to quantify the reliability of complete vehicle by measuring the failure rate of field truck tests. By doing that the failures were identified and fixed in the course of the project to ensure the trend down of the failure rate at SOP (Start of Production).