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Technical Paper

Analytical Methods for Durability in the Automotive Industry - The Engineering Process, Past, Present and Future

2001-03-05
2001-01-4075
In the early days of the automotive industry, durability and reliability were hit or miss affairs, with end-users often being the first to know about any durability problems - and in many cases forming an essential part of the development process. More recently, automotive companies have developed proving ground and laboratory test procedures that aim to simulate typical or severe customer usage. These test procedures have been used to develop the products through a series of prototypes and to prove the durability of the product prior to release in the marketplace. Now, commercial pressures and legal requirements have led to increasing reliance on CAE methods, with fatigue life prediction having a central role in the durability engineering process.
Technical Paper

Fatigue Life Prediction of MAG-Welded Thin-Sheet Structures

1998-09-29
982311
A finite-element (FE) based method for numerically predicting fatigue life of MAG-welded thin-sheet structures has been established and tested. The method uses nodal forces and moments calculated along the weld line, together with an analytical expression for the structural stress at the weld toe. The calculated stress is used together with an experimentally determined Wöhler, or S-N, curve. A “stiff” welded joint with structural stress dominated by membrane forces is found to have a steeper S-N curve than a “flexible” joint with structural stress dominated by bending moment. All test results were seen to lie close to one of two different S-N curves. The proportion of bending stress over total structural stress could be used for choosing the appropriate S-N curve.
Technical Paper

Galvanic Corrosion of Die Cast Magnesium Exposed on Vehicles and in Accelerated Laboratory Tests

2006-04-03
2006-01-0255
Galvanic corrosion between die cast AZ91D and AM60B and different fastener systems has been evaluated by exposure on trucks and in accelerated laboratory tests. The exposure time on the trucks was 3 years, corresponding to a mileage of about 300000 km. Samples were retracted and evaluated after 1 and 2 years exposure. Similar samples were also exposed to the Volvo Indoor Corrosion Test and the General Motors GM9540P-cycle B test. The correlation between the field data and the laboratory tests was evaluated, as was the sharp difference in the performance of the fastener systems in the two accelerated laboratory tests.
Technical Paper

Low Cycle Fatigue of Spot Welds Under Constant and Variable Amplitude Loading

2003-03-03
2003-01-0913
Experience from several car projects shows that S-N curves for spot welds generated under load control in the high cycle fatigue regime might be very conservative when used in the low cycle fatigue regime. Therefore, force and displacement controlled low cycle fatigue tests were carried out on peel and shear loaded specimens. Both constant (CA) and variable amplitude (VA) load signals were used. Finally, a method for predicting fatigue life of spot welds with increased accuracy in the low cycle fatigue regime is proposed. The method is simple, fast and accurate and can be used together with linear finite element analysis (FEA) and existing fatigue packages.
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