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What is the distribution of stresses in an artery that has internal stresses such that (a) α = 180°; (b) α = 150°?At what internal pressure will the stress outside and inside the wall become the same? Assume (i) that the stress from the pressure decays linearly to zero at the external surface, and (ii) a linear elastic behavior with E = 400 MPa. Given: ID = 15 mm; OD = 22 mm.
Stress shielding is a serious problem in some implants since bone remodels and the decrease of stress leads invariably to the weakening of the bone. Calculate the stresses in the femur head bone with and without an implant. Consider three cases: titanium implant,
E = 113 GPa; stainless steel implant,
E = 205 GPa;
carbon–polymer (polysulfone–PEEK) composite implant, E = 30 GPa. Given: outer diameter of femur = 3 cm; inner diameter = 1.5 cm; Eb = 20 GPa.
Calculate the maximum strength for the following two cases, using the Griffith equation. Given: (i) mineral platelets have thickness of 1 mm and diameter of 10 nm;
(ii) mineral platelets have thickness of 1 nm and diameter of 50 nm.
Assume γsurf = 1 J/m2 ; EHAP = 100 GPa.
Leonardo’s airplane had a wing span of approximately 7 m; the wings had a width of approximately 2 m. The rule of thumb for birds and other low-velocity flying machines is 5 kg/m2 . Would Leonardo’s plane glide?
An artery with dimensions OD = 20 mm and ID = 17 mm is subjected to pressures ranging from 80 mmHg to 130 mmHg.
(a) Determine the diameter of the artery of the systolic (highest) and diastolic (lowest) points. The material in the artery follows the relationship σ = kε 2 , with k = 25 MPa.
(b) Plot the pressure–radius curve due to the internal pressure from the stress–strain response of the material.
4.1 An interconnected 50 Hz power system consisting of one area has two
turbine-generator units, rated 600 and 800 MVA, with regulation constants
of 0.04 and 0.06 per unit, respectively, based on their respective ratings.
When each unit carries a 350 MVA steady-state load, let the area load
suddenly increase by 250 MVA. Determine:
4.1.1 The area frequency response characteristic on a 1000 MVA base. (5)
4.1.2 ∆
4.1 An interconnected 50 Hz power system consisting of one area has two
turbine-generator units, rated 600 and 800 MVA, with regulation constants
of 0.04 and 0.06 per unit, respectively, based on their respective ratings.
When each unit carries a 350 MVA steady-state load, let the area load
suddenly increase by 250 MVA. Determine:
4.1.1 The area frequency response characteristic on a 1000 MVA base. (5)
4.1.2 ∆
6. A three-phase, 50 Hz, 667 MVA, 22 kV, 4-pole steam driven turbine
generator has an
4.1 An interconnected 50 Hz power system consisting of one area has two
turbine-generator units, rated 600 and 800 MVA, with regulation constants
of 0.04 and 0.06 per unit, respectively, based on their respective ratings.
When each unit carries a 350 MVA steady-state load, let the area load
suddenly increase by 250 MVA. Determine:
4.1.1 The area frequency response characteristic on a 1000 MVA base. (5)
4.1.2 ∆
4.1 A 600 MVA, 50 Hz turbine-generator has a regulation constant R=0.06 per
unit based on its own rating. If the generator frequency increases by 0.02 Hz
in steady-state, what is the decrease in mechanical power output. Assume
a fixed reference power setting. (5)
4.2 A three-phase, 50 Hz, 100 MVA, 4-pole synchronous generator has an
inertia constant H of 3.5 s and is supplying 0.16 pu real power on a system
base of 500 MVA. The input to the generator is increased to 0.18 pu. Determine:
4.2.1 The kinetic energy stored in the moving parts of the generator
4.2.2 The acceleration of the generator
