Describe what you see in the fracture surfaces of these two HSLA bolts shown in image 2a and 2b. Comment on the fracture surface features that you see that help you distinguish whether this is a ductile or brittle failure, the type of loading, the magnitude of loading (high or low) and the expected fracture origin.
Design Against Fluctuating Loads
Machine elements are subjected to varieties of loads, some components are subjected to static loads, while some machine components are subjected to fluctuating loads, whose load magnitude tends to fluctuate. The components of a machine, when rotating at a high speed, are subjected to a high degree of load, which fluctuates from a high value to a low value. For the machine elements under the action of static loads, static failure theories are applied to know the safe and hazardous working conditions and regions. However, most of the machine elements are subjected to variable or fluctuating stresses, due to the nature of load that fluctuates from high magnitude to low magnitude. Also, the nature of the loads is repetitive. For instance, shafts, bearings, cams and followers, and so on.
Design Against Fluctuating Load
Stress is defined as force per unit area. When there is localization of huge stresses in mechanical components, due to irregularities present in components and sudden changes in cross-section is known as stress concentration. For example, groves, keyways, screw threads, oil holes, splines etc. are irregularities.
Describe what you see in the fracture surfaces of these two HSLA bolts shown in image 2a and 2b. Comment on the fracture surface features that you see that help you distinguish whether this is a ductile or brittle failure, the type of loading, the magnitude of loading (high or low) and the expected fracture origin.
The given figure depicts the fracture of 2 High strength Low alloy steel.
There are several reasons and mechanisms for bolt failure. But the shape and surface of the fracture provides information on the type of failure and sheds light on the reason for failure.
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