Question & Answer

In a tensile test a metal begins to neck at a true strain = 0.28 with a corresponding true stress = 345.0 MPa. Without knowing any more about the test, can you estimate the strength coefficient and the strain-hardening exponent in the flow curve equation?

During a tensile test, a metal has a true strain = 0.10 at a true stress = 37,000 lb/ⁱⁿ² . Later, at a true stress = 55,000 lb/ⁱⁿ² , true strain = 0.25. Determine the strength coefficient and strain-hardening exponent in the flow curve equation.

In a tensile test on a metal specimen, true strain = 0.08 at a stress = 265 MPa. When true stress = 325 MPa, true strain = 0.27. Determine the strength coefficient and the strain-hardening exponent in the flow curve equation.

In Problem 3.3, determine the strength coefficient and the strain-hardening exponent in the flow curve equation. Be sure not to use data after the point at which necking occurred.

During a tensile test in which the starting gage length = 125.0 mm and the cross-sectional area = 62.5 ^mm2 , the following force and gage length data are collected (1) 17,793 N at 125.23 mm, (2) 23,042 N at 131.25 mm, (3) 27,579 N at 140.05 mm, (4) 28, 913 N at 147.01 mm, (5) 27,578 N at 153.00 mm, and (6) 20,462 N at 160.10 mm. The maximum load is 28,913 N and the final data point occurred immediately prior to failure. (a) Plot the engineering stress strain curve. Determine (b) yield strength, (c) modulus of elasticity, and (d) tensile strength.

A test specimen in a tensile test has a gage length of 2.0 in and an area = 0.5 in2 . During the test the specimen yields under a load of 32,000 lb. The corresponding gage length = 2.0083 in. This is the 0.2 percent yield point. The maximum load of 60,000 lb is reached at a gage length = 2.60 in. Determine (a) yield strength, (b) modulus of elasticity, and (c) tensile strength. (d) If fracture occurs at a gage length of 2.92 in, determine the percent elongation. (e) If the specimen necked to an area = 0.25 in2 , determine the percent reduction in area.

A tensile test uses a test specimen that has a gage length of 50 mm and an area = 200 mm² . During the test the specimen yields under a load of 98,000 N. The corresponding gage length = 50.23 mm. This is the 0.2 percent yield point. The maximum load of 168,000 N is reached at a gage length = 64.2 mm. Determine (a) yield strength, (b) modulus of elasticity, and (c) tensile strength. (d) If fracture occurs at a gage length of 67.3 mm, determine the percent elongation. (e) If the specimen necked to an area = 92 mm² , determine the percent reduction in area.

There are 15 correct answers in the following multiple choice questions (some questions have multiple answers that are correct). To attain a perfect score on the quiz, all correct answers must be given. Each correct answer is worth 1 point. Each omitted answer or wrong answer reduces the score by 1 point, and each additional answer beyond the correct number of answers reduces the score by 1 point. Percentage score on the quiz is based on the total number of correct answers

3.1 Which of the following are the three basic types of static stresses to which a material can be subjected (three correct answers): (a) compression, (b) hardness, (c) reduction in area, (d) shear, (e) tensile, (f) true stress, and (f) yield?

3.2 Which one of the following is the correct definition of ultimate tensile strength, as derived from the results of a tensile test on a metal specimen: (a) the stress encountered when the stress-strain curve transforms from elastic to plastic behavior, (b) the maximum load divided by the final area of the specimen, (c) the maximum load divided by the original area of the specimen, or (d) the stress observed when the specimen finally fails?

3.3 If stress values were measured during a tensile test, which of the following would have the higher value: (a) engineering stress or (b) true stress?

3.4 If strain measurements were made during a tensile test, which of the following would have the higher value: (a) engineering strain, or (b) true strain?

3.5 The plastic region of the stress-strain curve for a metal is characterized by a proportional relationship between stress and strain: (a) true or (b) false?

3.6 Which one of the following types of stress strain relationship best describes the behavior of brittle materials such as ceramics and thermosetting plastics: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above?

3.7 Which one of the following types of stress strain relationship best describes the behavior of most metals at room temperature: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above?

3.8 Which one of the following types of stress strain relationship best describes the behavior of metals at temperatures above their respective recrystallization points: (a) elastic and perfectly plastic, (b) elastic and strain hardening, (c) perfectly elastic, or (d) none of the above?

3.9 Which one of the following materials has the highest modulus of elasticity: (a) aluminum, (b) diamond, (c) steel, (d) titanium, or (e) tungsten?

3.10 The shear strength of a metal is usually (a) greater than or (b) less than its tensile strength?

3.11 Most hardness tests involve pressing a hard object into the surface of a test specimen and measuring the indentation (or its effect) that results: (a) true or (b) false?

3.12 Which one of the following materials has the highest hardness: (a) alumina ceramic, (b) gray cast iron, (c) hardened tool steel, (d) high carbon steel, or (e) polystyrene?

Viscosity can be defined as the ease with which a fluid flows: (a) true or (b) false?

3.13 Viscosity can be defined as the ease with which a fluid flows: (a) true or (b) false?

What is viscoelasticity, as a material property?

What is the defining characteristic of a Newtonian fluid?

Define viscosity of a fluid.

Define the recrystallization temperature for a metal.

Why are different hardness tests and scales required?

What is hardness, and how is it generally tested?

How is shear strength S related to tensile strength TS, on average?

How is the shear modulus of elasticity G related to the tensile modulus of elasticity E, on average?

Tensile testing is not appropriate for hard brittle materials such as ceramics. What is the test commonly used to determine the strength properties of such materials?

What is the complicating factor that occurs in a compression test?

How does the change in cross-sectional area of a test specimen in a compression test differ from its counterpart in a tensile test specimen?

In what case does the strength coefficient have the same value as the yield strength?

What is work hardening?

Why cannot a direct conversion be made between the ductility measures of elongation and reduction in area using the assumption of constant volume?

Define yield strength of a material.

Define tensile strength of a material.

What is the difference between engineering stress and true stress in a tensile test?