An aircraft component is fabricated from an aluminum alloy that has a plane strain fracture toughness of 38 . it has been determined that fracture results at a stress of 223 mpa when the maximum (or critical) internal crack length is 2.85 mm. a) determine the value of for this same component and alloy at a stress level of 334 mpa when the maximum internal crack length is 1.43 mm. g

The y form of iron is known as: a) ferrite b) cementite c) perlite d) austenite

The mass flow rate of the fluid remains constant in all steady flow process. a)- true b)- false

Air is to be cooled in the evaporator section of a refrigerator by passing it over a bank of 0.8-cm-outer-diameter and 0.4-m-long tubes inside which the refrigerant is evaporating at -20°c. air approaches the tube bank in the normal direction at 0°c and 1 atm with a mean velocity of 4 m/s. the tubes are arranged in-line with longitudinal and transverse pitches of sl- st 1.5 cm. there are 30 rows in the flow direction with 15 tubes in each row. determine (a) the refrigeration capacity of this system and (b) pressure drop across the tube bank. evaluate the air properties at an assumed mean temperature of -5°c and 1 atm. is this a good assumption?