Question 3 (a) Figure 4 on the right shows a large Metal Z alloy plate with a critical stress-intensity factor of 50 (MPa ✓m). Given the value of the geometrical function, f= 5.15 and the fact that this plate fractures at a stress of 200 MPa, i. Calculate the maximum center crack length of this plate. ii. Metal Z will/will not fracture when put under the following conditions: 1 1 1 K₁=fo Ja geometrical function H↓↓ Condition 1: Undergo fracture at a maximum center crack of 1.2mm Condition 2: Does not undergo fracture at a maximum centre crack of 0.8 mm. Figure 4 Determine the minimum stress level that will lead to fracture in Condition 1 and the maximum stress level that will not lead to fracture in Condition 2. Explain and show all your working clearly.
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.
The subject is corrosion and protection of materials.
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