MCQs for Machine design

1. Question 1

Material	Sy	Sut	E
AISI 4130	100 ksi	125 ksi	29 x 10^3 ksi
AISI 1025	36 ksi	55 ksi	29 x 10^3 ksi​
Aluminum 2014 T6	53 ksi	60 ksi	10.8 x 10^3 ksi
Aluminum 6061 T4	16 ksi	30 ksi	9.9 x 10^3 ksi
Ti-6AL-4V	126 ksi	134 ksi	16 x 10^3 ksi

You have a bar of AISI 4130 steel, a bar of Aluminum 6061 T4, and a bar of Ti-6AL-4V. All of the bars have identical cross section areas of 1 in^2. An axial stress of 20 ksi is placed on each of the bars. Which bar will yield?

AISI 4130 Steel

Aluminum 6061 T4

Ti-6AL-4V

All of the bars will yield

Question 2

1

point

2. Question 2

Material	Sy	Sut	E
AISI 4130	100 ksi	125 ksi	29 x 10^3 ksi
AISI 1025	36 ksi	55 ksi	29 x 10^3 ksi​
Aluminum 2014 T6	53 ksi	60 ksi	10.8 x 10^3 ksi
Aluminum 6061 T4	16 ksi	30 ksi	9.9 x 10^3 ksi
Ti-6AL-4V	126 ksi	134 ksi	16 x 10^3 ksi

You have a bar of AISI 4130 steel, a bar of Aluminum 6061 T4, and a bar of Ti-6AL-4V. All of the bars have identical cross section areas of 1 in^2. An axial stress of 20 ksi is placed on each of the bars. Which bar is the strongest?

AISI 4130 Steel

Aluminum 6061 T4

Ti-6AL-4V

All of the bars have the same strength

Question 3

1

point

3. Question 3

You have a bar of AISI 4130 steel, a bar of Aluminum 6061 T4, and a bar of Ti-6AL-4V. All of the bars have identical cross section areas of 1 in^2. An axial stress of 15 ksi is placed on each of the bars. Which bar will be the stiffest?

AISI 4130 Steel

Aluminum 6061 T4

Ti-6AL-4V

All of the bars have the same stiffness

Question 4

1

point

4. Question 4

A bar of 4340 steel has an Sy = 50 ksi. Which of these statements is true:

If Sy = 50 ksi, than the normal stress in the bar is always 50 ksi.

If a normal stress of 40 ksi is applied to the bar, it will undergo plastic deformation.

The Sy = 50 ksi indicates bar is behaving in a brittle manner.

Any normal stress above 50 ksi will cause plastic deformation in the bar.

Question 5

1

point

5. Question 5

You are designing a rod with a fixed geometry with a 1 inch diameter and a 20 inch length. The current design is made of 2014 T6 aluminum, with an E = 10.5 Mpsi and a Sy = 54 ksi. Your analysis shows that the rod’s deflection is too high. To fix this you should:

Choose a material with a higher Sy.

Choose a material with a lower Sy.

Choose a material with a higher E.

Choose a material with a lower E.

Question 6

1

point

6. Question 6

You are designing a 4340 steel shaft that is going to be press fit into an 2014 T6 aluminum housing. The 4340 steel rod has the following properties: E =29 Mpsi, Sy =75 ksi, and the coefficient of thermal expansion (alpha) = 10.8 x 10-6 K^(-1). The 2014 T6 aluminum housing has the following properties: E =10.5 Mpsi, Sy =54 ksi, and the coefficient of thermal expansion (alpha) =23.1 x 10-6 K^(-1). The operating temperatures range from -30F to 400F. Which of the following statements are true? (Note: more than one statement could be true)

There is a mismatch between the coefficients of thermal expansion between the steel and aluminum, which could lead to problems in the press fit at cold and high temperatures.

The yield strength of the aluminum is less than that of steel, which means the aluminum will behave in a more rigid manner than the steel.

The elastic modulus of steel is greater than that of aluminum, meaning that the aluminum will behave in a brittle manner while the steel will behave in a ductile manner.

Question 7

1

point

7. Question 7

Select all of the following statements that are true about creep: (Note: more than one statement could be true).

Yield will occur below the yield strength.

Yield will never occur below the yield strength

Creep is typically a concern for metals under load for long periods of time at elevated temperatures.

Creep is typically a concern for metals under load for long periods of time at very low temperatures.

Question 8

1

point

8. Question 8

Which of the following statements are true for metals undergoing heat treating and cold working processes: (More than one statement could be true)

An increase in ductility correlates with an increase in yield strength.

A decrease in ductility correlates with a decrease in yield strength.

An increase in ductility correlates with a decrease in yield strength.

A decrease in ductility correlates with an increase in yield strength.