a) A bicycle frame is being designed to carry a pedal force of 800N. Assuming axial loading only, which material will produce the lightest frame out of the two in the table below? Assume a design factor of 1.2 b) If the bicycle frame is being welded together and an internal flaw size of 30mm results, which material will produce the lighter section? (Apply a design factor of 1.2 If the bicycle frame needs to last a minimum 3 x 105 cycles, with an average stress of 150MPa and an alternating stress of 200MPa, use the Soderberg criterion to pick a suitable material from the two alloys listed above. Show all your working
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.
- a) A bicycle frame is being designed to carry a pedal force of 800N. Assuming axial loading only, which material will produce the lightest frame out of the two in the table below? Assume a design factor of 1.2
- b) If the bicycle frame is being welded together and an internal flaw size of 30mm results, which material will produce the lighter section? (Apply a design factor of 1.2
- If the bicycle frame needs to last a minimum 3 x 105 cycles, with an average stress of 150MPa and an alternating stress of 200MPa, use the Soderberg criterion to pick a suitable material from the two alloys listed above. Show all your working.
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