Strength versus Toughness
Although counter intuitive increasing yield strength may not prevent failure.
Don't underestimate the complexities of bolting - Pretension your bolts
Incorrectly pretensioned bolts cause leaks, allow relative movement between components, and often result in joint failure when the bolts in question come loose or fail by fatigue or other mechanisms.
The importance of stress analysis in failure investigations
Failure of a component is generally related to a combination of applied load (design and actual loads), operating environment, material properties, the geometry of the component and manufacturing techniques. In order to establish the underlying cause of a failure it is necessary to consider all these aspects.