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A Bad Example #49

Mechanics Corner A Journal of Applied Mechanics & Mathematics, #49 A Bad Example Most of us are inclined to trust an established textbook. We assume (1) the author knows what he is talking about, (2) the book has been carefully vetted by several editors and reviewers, and finally (3) the fact that it is well established in the market means that thousands of other readers have tacitly endorsed it as well. While these assumptions are usually true, they are no guarantee, and they

DrD

DrD

 

New Help Site

I'd like to invite all readers to visit my new website: Machinery-Mechanics-Professor.site I'm offering free help for engineering students through that site, so come on over and take a look. DrD

DrD

DrD

 

When You Ask for Help ....

Today, I have a question for readers. I'd like to get everyone who is willing to answer the same question, but also tell me whether you are a practicing graduate engineer or if you currently a student. I think these two groups will answer somewhat differently, so it is important that you identify which one you fall into. The question is really simple: When you ask for help, what do you really want? Are you asking for someone to step in and solve a problem for you? Or, are you asking for a f

DrD

DrD

 

Mechanical engineering login contest 1

To Encourage participation on Mechanical-engg.com, knowledge community for mechanical engineering professionals. 1 Login on 22 or 23rd January 2020 Mechanical-engg.com and update your profile. login link : https://mechanical-engg.com/login/ One Lucky winner will get Amazon Gift card (Rs 300 or 5 USD) This is the first contest and we are testing our mechanism... Be prepared for some exciting prizes in the upcoming contest. Make sure you are a mechanical engineer

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What Would You Like to Know?

What Would You Like  to Know? If you could ask me any question you want, what would you like to know that you think I might know? I certainly do not know everything, but through the years I have accumulated a certan amount of knowledge that I'd like to pass on to you. Therefore, I ask, what would you like to know? Many readers are still in college, and no doubt they would like to know what is going to be on the next exam. I'm sorry, but I have no way to know that. What I might be able

DrD

DrD

Mechanical Engineering Forum Invitation

Mechanical Engineering Forum Invitation

*Invitation - Only for Mechanical Engineers* Mechanical Engineering Discussion forums  *Forums Link*  https://mechanical-engg.com/forums/ To Login  https://mechanical-engg.com/login/ For quick login - you can login with Facebook, Twitter, Google etc. To Start new discussion : Click Start new topic button Start with Profile and status updates *Special Offer to encourage participation in the field of Mechanical Engineering*   Two Lucky members who logged in between 5

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get updates via whatsapp - Join whatsapp groups for Mechanical engineers

Dear Members, we will share quiz links,  questions, and discussion topics directly with whatsapp group. Please join only 1 group as - all groups will receive same posts  Only for Mechanical Engineers  They will be admin only groups ... you will not be allowed to post - Marketing people should not join these groups. All interaction will take place via websites Mechanical Engineering Group 101 https://chat.whatsapp.com/GUCrHpf4igeJxRXjthnzXw Mechanical Engineering Gro

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Describe the steps usually considered in the process of material selection.

(a) Describe the steps usually considered in the process of material selection. (b) How material selection is done using decision theory.   Ans. (a) Like any other aspect of engineering design, material selection is also equally important aspect. Material of part depends on the requirements of the part, number of parts needed, and manufacturing process to be adopted to make the part. The material selection primarily depends upon its properties and several other factors like availa

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Discuss the effect of temperature on zinc and zinc alloys.

Temperature has pronounced effect on the properties of zinc and zinc alloys. The creep resistance, in particular, decreases rapidly with increasing temperature. Ductility and general fabricating characteristics increase with temperature. Drawing and forming operation should never be attempted below 20°С. More severe operations can be performed readily at temperatures above 50°C. Zinc alloys become somewhat brittle below 0°C, depending on the particular composition, but recover their normal prope

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What do you understand by season cracking in brasses and how it can be prevented ?

Season cracking is spontaneous cracking which occurs on exposure to atmospheric corrosion in brass objects with high residual tensile stresses at the surface. It occurs with high-zinc brasses but rarely with 15 per cent zinc or below. Alloys susceptible to spontaneous season cracking will crack when exposed to corrosive conditions under high service stress, even if they are free from internal strains. Season cracking can be prevented by avoiding the production of internal microstresses or by rem

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State, with reasons, suitable material for the manufacture of each of the following, giving the approximate composition : (a) a brass for deep pressed containers;

State, with reasons, suitable material for the manufacture of each of the following, giving the approximate composition : (a) a brass for deep pressed containers; (b) a brass for small machined bolts ; (c) a bronze for the impeller of a sea-water pump.   (a) The suitable brass for deep pressed containers is the admiralty brass containing copper and zinc in the proportion of 7 to 3, with 1% of tin. The addition of tin to the basic cartridge brass (70% copper, 30% zinc), gives

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What is the main difference between a brass and a bronze ?

(a) What is the main difference between a brass and a bronze ? (b) State the composition, and two common uses of a bronze commonly used in engineering. (c) What is the general effect of adding a small proportion of (1) phosphorus, (ii) lead, to a bronze ?   (a) A brass is an alloy of copper and zinc, the major constituent being copper. A bronze is an alloy of copper and tin, the major constituent being copper. (6) A bronze commonly used in engineering and commonly known

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Which two elements are alloyed to form a brass ?

(a) Which two elements are alloyed to form a brass ? (b) What are the differences (i) in composition, (ii) in uses, of an 'alpha' and an 'alpha-beta' brass ?   (a) A brass is essentially an alloy having major constituents as copper and zinc. Minor proportions of elements such as lead and tin may be included to promote special properties. (b) An alpha brass is an alloy in which zinc does not exceed by 38%. This brass is ductile and, therefore, used for cold-rolled sheets, wire

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What do you understand by a free-cutting steel?

What do you understand by a free-cutting steel? What elements are usually added to make a steel free cutting, and how they make the steel free. cutting?   A free-cutting steel is one in which an element like lead or sulphur is deliberately added to promote rapid machining When sulphur is added to steel, it forms a brittle constituent with manganese, known as manganese sulphide, which being brittle, allows chip cracks to propagate and breaks chips into easily handled lengths.

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What is the composition of following alloys ? What are their special characteristics and what for these are used ?

(i) Permalloy, (ii) Invar, (iii) Elinvar, (iv) Platinite, (v) Dumet wire. Ans. (i) Permalloy has 78.5% nickel. It has a high permeability and low hysteresis loss. (i) Invar contains 36% nickel and has an exceedingly low coefficient of linear expansion. Since its expansion is proportional to the temperature within limits of atmospheric temperature change, it is used for secondary standards of length. (ii) Elinvar contains 32% nickel with small percentage of Cr, W, Mn, Si and C. In addit

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