Improved Quality Assurance of Fatigue Loaded Structures - The Necessary Shift from Technology Focus towards Information Driven Weld Evaluation

Licentiate thesis, 2013

The research has shown that the insufficient use of process information leads to unnecessary and costly safety margins in each step of production. This is, in short term, affecting the productivity of the company. Even more serious is the effect that insufficient use of process information has on product and process development in the long term. This situation is restricting welding companies from reducing weight of their fatigue loaded structures. The consequences can be higher fuel consumption and fewer payloads than possible which is affecting the companies’ competitiveness. A model is presented that emanates from the internal customer’s need for information about the product or the process. Several aspects should be decided on before the evaluation method is chosen, such as what information is needed and suitable ways to present that information. The thesis is describing six empirical studies. Four of them were investigating evaluation methods. The theoretical and empirical studies show that the current situation is highly affected by variation. The evaluation methods used are in some cases not reliable and there is a lack of evaluation method for certain defects. In one study an alternative evaluation method, developed according to the suggested model, was presented. The financial impact achieved by using the retrieved information, was shown. Obstacles preventing quality assurance of welds were identified in one of the studies. It showed not to be technical but rather methodological obstacles. The way the evaluation information is presented is influencing the possibility to make correct decisions. This was exemplified in the last study about using control charts on key performance indicators. Implemented result from the research indicates significant financial effect.