Knee replacement surgery was performed on a patient suffering from cartilage damage. The bottom or stemmed...

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Knee replacement surgery was performed on a patient suffering from cartilage damage. The bottom or stemmed tibial component of the knee replacement consists of a flat metal platform with protruding stem, as shown. The stem is circular in cross section (diameter = 1.5 cm) and is covered by a beaded surface. During surgery. The implant is poorly positioned in the patient's knee, causing the one side to be loaded by 100 N more than the other side. After 1 year, a crack forms in the stem as indicated. Implant in Knee Thigh/ Knee Stemmed Tibial Plate F=100N Stemmed Tibial Plate Crack 2 cm Beaded surfage • Identify two sources of stress concentration on the implant. • What would you expect the stress concentration, Kt, to be at the crack? - Less than 3, equal to 3 or more than 3. Explain briefly....and why 3 is the magic number here? • Sketch a typical S-N curve (S: fatigue strength, N: number of cycles) for the stemmed tibial, using the following information: o Suit = 500 MPa o At 10³ cycles, the fatigue stress is 450 MPa o Endurance limit = 100 MPa Note: be sure to label your x and y axes! • Estimate the life of the un-cracked component if the applied stress is 68 MPa. Knee replacement surgery was performed on a patient suffering from cartilage damage. The bottom or stemmed tibial component of the knee replacement consists of a flat metal platform with protruding stem, as shown. The stem is circular in cross section (diameter = 1.5 cm) and is covered by a beaded surface. During surgery. The implant is poorly positioned in the patient's knee, causing the one side to be loaded by 100 N more than the other side. After 1 year, a crack forms in the stem as indicated. Implant in Knee Thigh/ Knee Stemmed Tibial Plate F=100N Stemmed Tibial Plate Crack 2 cm Beaded surfage • Identify two sources of stress concentration on the implant. • What would you expect the stress concentration, Kt, to be at the crack? - Less than 3, equal to 3 or more than 3. Explain briefly....and why 3 is the magic number here? • Sketch a typical S-N curve (S: fatigue strength, N: number of cycles) for the stemmed tibial, using the following information: o Suit = 500 MPa o At 10³ cycles, the fatigue stress is 450 MPa o Endurance limit = 100 MPa Note: be sure to label your x and y axes! • Estimate the life of the un-cracked component if the applied stress is 68 MPa.

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Solution 1 Two sources of stress concentration on the implant are a The beaded surface of the stem w... View the full answer