In: Mechanical Engineering
Would the four metals: nickel, titanium (well. the three boats I'm using would melt before this would at a pressure of the vacuum pump we have is capable of), iron, or chromium
would they react and cause corrosion to tungsten,
molybdenum, or tantalum boats at temperatures of 1400 celcius or
higher at vacuum pressures of 7.1x10^-2 torr? What would react and
corrode with what? Why?
would any of these 7 metals (the three boats and the
other four) react with what little oxygen is left in the vacuum
chamber at a pressure of 10^-2 torr?
Please help and show where your sources are
ALSO where can I find a table for emissivity values at
VARYING temperatures for tungsten, molybdenum, and
tantalum?
In: Mechanical Engineering
Nitrogen (N2) contained in a piston–cylinder arrangement, initially at 9.9 bar and 421 K, undergoes an expansion to a final temperature of 300 K, during which the pressure–volume relationship is pV1.1 = constant. Assuming the ideal gas model for the N2, determine the heat transfer in kJ/kg.
In: Mechanical Engineering
An as-wound helical-coil compression spring with infinite fatigue life is needed to resist a dynamic load that varies from 8.0 to 24.0 lbf at 45.0 Hz over a dynamic deflection of 0.3 in. Because of assembly considerations, the solid length of the spring cannot be more than 1.2 in. The spring should have squared and ground ends and is to be made from peened music wire. Upon closure, use a design factor of 1.2 guarding against yielding and a fractional overrun to closure x = 0.15. The fundamental critical frequency should be greater than 10 times the frequency of the dynamic load. The springmaker has the following wire sizes in stock: 0.059, 0.063, 0.072, 0.075, 0.085, and 0.090 in. Select a suitable spring with a fatigue design factor of 1.9 using the Goodman-Zimmerli fatigue failure criterion. Calculate the cost of the wire from which the spring is wound and use it as the figure of merit for your selection
In: Mechanical Engineering
A piston-cylinder has a volume of 1 ft3 and contains a substance initially at 50 °F and 1 atm. The system is then heated until the temperature becomes 300 °F. Determine the total heat added (Btu) and final volume (ft3) assuming the substance is: a) water, b) copper, c) neon, d) air.
In: Mechanical Engineering
Refrigerant-134a enters the condenser of a residential heat pump at 900 kPa and 65oC at a rate of 0.018 kg/s and leaves at 750 kPa subcooled by 2oC. The refrigerant enters the compressor at 200 kPa superheated by 3oC. Determine (a) the isentropic efficiency of the compressor in decimal (up to two decimals), (b) the rate of heat supplied to the heated room, and (c) the COP of the heat pump. Also determine (d) the COP if this heat pump operated on the ideal vapour compression cycle between the pressure limits of 200 and 900 kPa
In: Mechanical Engineering
show the correlation between weight percent carbon, volume percent pearlite, and tensile strength for hot rolled carbon
steels by
1- Looking up the tensile strengths in psi for the following hot rolled AISI carbon steels in matweb.com: 1006, 1010,
1020, 1025, 1030, 1035, 1040, 1045, 1050, 1055, 1060, 1065, and 1070.
2- Calculating the volume percent pearlite for each steel (assume that vol.% pearlite = wt.% pearlite) using the lever
rule and the nominal carbon content indicated by the AISI number.
3- Recording the values in an EXCEL Worksheet that has columns for wt. %C, vol.% pearlite, and tensile strength.
4- Plotting EXCEL graphs of vol.% pearlite versus wt. %C, tensile strength versus wt. %C, and tensile strength
versus vol.% pearlite
In: Mechanical Engineering
In: Mechanical Engineering
In: Mechanical Engineering
1. A black thermocouple measures the temperature in a chamber with black walls. If the air around the thermocouple is at 20°C, the walls are at 100°C, and the heat transfer coefficient between the thermocouple and the air is 15 W /m2·°C, what temperature will the thermocouple read
In: Mechanical Engineering
3. A stainless steel sphere of thermal conductivity 16 W/m · K with a diameter of 4 cm is exposed to a convective environment of 15 W/m2 · K, 20?C. Heat is generated uniformly in the sphere at a rate of 1.0 MW/m3 . Determine the steady-state temperature of the sphere at its center and its surface. Also determine the heat flux at a radius of 1.5 cm.
In: Mechanical Engineering
A bicycle rider is interested in the effects of temperature on air density. A change in temperature will also affect the tire pressure.
a) Write a computer program that calculates air density at atmospheric pressure for temperatures from -10?C to 50?C.
b) Assume that a bicycle tire is inflated to an absolute pressure of 450 kPa at 20?C. Assume also that the volume of the tire does not change with temperature. Write a program to show how the tire pressure changes with the temperature in the same range, -10?C to 50?C.
Prepare a table or graph or both.
In: Mechanical Engineering
Which of the following statements are true regarding AMF/3MF files, in comparison to STL files?
Select all that apply.
a) AMF/3MF files can represent overhangs of greater than 45 degrees, while STL files cannot
b) AMF/3MF files do not require the model to be sliced before printing
c) AMF files can specify multiple materials within the same part
d) The 3MF file format can enumerate the structure of a lattice as a periodic unit, making the file size more compact
In: Mechanical Engineering
In: Mechanical Engineering
In: Mechanical Engineering