1. Two samples of a low hardness steel were tested using a Rockwell C hardness t

Question

1. Two samples of a low hardness steel were tested using a Rockwell C hardness tester and the Rockwell B scale at the same lab on the same day . The difference between the average hardness of the two samples was 0.5 Rockwell C. Do you think there is a significant difference in the hardness? Justify your answer. Hint: Use the specification!!

2. Two manufacturers produce a steel. Manufacturer B claims their steel is better than manufacturer A because their average Rockwell B hardness is 68.4 HRBW while that of manufacturer B is 60.5 HRBW. Do you think there is a significant difference in their hardness? Justify your answer. Hint: Use the specification!!

3. Find an important engineering failure that involves some of the topics discussed in MSE 350. Describe the failure, why it occurred, the damage (human, environmental, and economic) and the changes that could have been made in the design to avoid the failure. Was the failure caused by lack of engineering knowledge at the time, engineering error, or management/government error? Discuss!!

4.

For each of the following common items, identify what they are commonly made of, the material type (composite, metal, semiconductor, polymer <thermoplastic, thermoset or elastomer>, ceramic, glass. Describe why that material type is used. Include at least two references for your answers (websites are fine, but try and find good ones). If more than one material type is used in the items, include them all! Be careful to use proper engineering vocabulary when answering this question!

Abrasives for grinding metal

Automobiles

Integrated circuits

Airplanes

Bridges

Solar panels

Latex paint

Soda bottles

Polyvinylchloride (PVC) plumbing pipes

Explanation / Answer

1. ANS:

Here two different scales are used they are scale B and scale.C scale B is used for low hardness materials using a steel ball indenter using 100 kg of load. and scale C is used for harder materials using a diamond cone indenter using 150 kg of load.As the diiference between the hardness of the two samples was only 0.5 HRC. So it can be said that there is minimum differenece between the hardness of the two samples.As the diiference between the hardness of the two samples was only 0.5 HRC. So it can be said that there is minimum differenece between the hardness of the two samples.

2.ANS:

Given that manufacturer B claims their steel is better than manufacturer A because their average Rockwell B hardness is 68.4 HRBW while that of manufacturer B is 60.5 HRBW. This range of 60-68 rockwell hardness number is for induction hardened gear material. and the difference is not so large. This range is acceptable for material from specification point of view i.e this tolerance is acceptable.

NOTE:

as per chegg guidelines i answered 2 que

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