problems_section_6[1]

# problems_section_6[1] - Problems – Mechanical Properties...

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Problems – Mechanical Properties 1. A tensile test is to be performed on a piece of plain-carbon steel plate. Suppose its yield stress is 50 ksi and its ultimate tensile stress is 65 ksi. The plate is 16 gauge (i.e. thickness = 0.05082”). For a flat tensile specimen cut from this plate with a gauge width of 0.75 in, does the tensile test instrument have sufficient capacity to break tensile bars of this steel if the maximum load it can apply is 10,000 lbs.? Quantitatively justify your answer. 2. A plain-carbon steel has a yield strength of 35 ksi, a tensile strength of 52 ksi and a modulus of 29,000 ksi. Suppose a 3 inch diameter rod of this steel with a length of 10 feet is loaded in tension with 10,000 pounds of force. a. Determine the stress in the rod. b. Determine the total strain of the rod. c. What component of this strain is due to plastic deformation? Briefly explain. 3. Steel pipe employed for oil drilling operations is made up of many segments joined sequentially and suspended in an oil well. Suppose the pipe used in one such application has an outer diameter of 7.5cm and an inner diameter of 5cm, a density of 7.90Mg/m 3 , and a yield strength of 900MPa. If the pipe is designed with a safety factor of two [i.e. the maximum stress in the field must be less than half the rated yield stress], what is the maximum depth that can be safely reached for drilling. Where does the maximum elastic strain occur in the pipe? 4. During the growth of silicon single-crystal boules, a small seed of silicon single crystal is immersed in a melt of liquid silicon and then slowly removed from the melt. Silicon atoms from the melt deposit on the solid surface, and the crystal grows at the melt surface as the seed is pulled from the melt. The result is a single-crystal solid with a circular cross section whose length can be as much as 1-2 m. What is the maximum boule length that can be supported by the seed if the boule diameter is 15 cm and the yield stress of Si is 210 MPa? 5. An 18-8 stainless steel is characterized by the following mechanical properties: σ y = 120 ksi; σ T = 180 ksi; elongation to failure = 12%; E = 12,000 ksi Using these four properties as guides, sketch a well-labeled stress-strain diagram for this material. 6. Given the following properties describing Ti-6Al-4V, sketch a possible stress-strain diagram for this material: E = 110 GPa; σ y = 825 MPa; σ T = 895 MPa; % elongation to failure = 10 7. For the 7075-T6 aluminum alloy described in the adjacent diagram, determine:

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a. the yield stress; b. the tensile stress; c. the elongation to failure; and d. the modulus. Suppose a tensile bar of this alloy is deformed in tension to an engineering strain of 0.02, the load is released to F=0, then the same bar is used in a second identical tensile test. Sketch the stress-strain curve for the second test. Identify (i.e. give specific values) the elastic modulus, the yield stress, the ultimate tensile stress, and the percent elongation to
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## This note was uploaded on 10/03/2009 for the course E e 344l taught by Professor Libera during the Spring '09 term at Stevens.

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problems_section_6[1] - Problems – Mechanical Properties...

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