Power is transmitted between two steel rollers pressed together, as in Figure

In 1824, Sir Humphry Davy proposed protecting the copper sheathing on the oceangoing HMS Samarang using iron anodes. Explain why this would be effective.

Aluminum plates are fastened together with brass rivets. The aluminum plates have a total exposed area of \(1.5 \ \mathrm{ft.}^2\) and the rivets have a total exposed area of \(2.5 \ \mathrm{in.}^2\). The environment involves moisture and some salt. (a) Which metal will corrode? (b) If twice as many rivets are used, what effect would this have on the total rate of corrosion?

Square metal plates having a total exposed area of \(10.75 \ \mathrm{ft.}^2\) are fastened together with rivets having a total exposed area of \(15.5 \ \mathrm{in.}^2\). The environment involves moisture and some salt. Consider two cases: (1) iron plates with nickel–copper alloy rivets, and (2) nickel–copper alloy plates with iron rivets. (a) For each case, which metal will corrode? (b) How do the rates of corrosion compare for the two cases? (c) If half as many rivets were used, what influence would this have on the total rate of corrosion?

Lead sheet is pop-riveted with special bronze fasteners. The total exposed area of the sheet is 100 times that of the fasteners. The environment for the assembly is seawater. (a) Which metal will corrode? (b) If half as many fasteners are used, what influence would this have on the total rate of corrosion? (c) How could corrosion be reduced?

Galvanized steel sheet metal is fastened together with copper rivets. The galvanized steel sheet has an area of \(1.2 \ \mathrm{ft}^2\) and the rivets have a total exposed area of \(2 \ \mathrm{in.}^2\). The environment contains moisture and some salt. (a) Which metal will corrode? (b) If half as many rivets are used, what effect would this have on the total rate of corrosion? (c) How could corrosion be reduced?

Search www.corrosion-doctors.org, and under the Information Modules section select Corrosion by Environments. Choose one of the listed topics and write a summary of the information covered. Include if costs are addressed, types of materials affected, what type of corrosion can be expected, and how to deter the effects of corrosion.

Review the web site http://www.corrosionsource.com. (a) What types of corrosion phenomena can be identified by visual observation? (b) What methods of controlling corrosion are suggested?

An assembly comprised of circular AISI 301 stainless steel plates having a total exposed area of \(1.5 \ \mathrm{m}^2\) are bolted together with chromium-plated steel cap screws having a total exposed area of \(110 \ \mathrm{cm}^2\). The environment contains moisture, and possibly some salt (see Figure P9.8). (a) Which metal will corrode? (b) If half as many bolts are used, what influence would this have on the total rate of corrosion? (c) How could corrosion be reduced?

Repeat Problem 9.8, except use titanium cap screws.

Some plumbing codes require that an electrical insulator be used when copper tubing is connected to steel pipe. With the aid of a simple sketch, explain the rationale behind this requirement.

A pickup truck tailgate cable having a breaking strength of 4000 lb is fabricated from \(7 \times 19\) braided carbon steel wire. To prevent corrosion, the 5-mm-diameter cable is galvanized and covered with a weather resistant heat shrink tube made of crosslinked polyolefin. The ends of the tailgate cable are sealed with epoxy during manufacturing. Because of its geometry and specific end fixtures, the cable bends and twists when the pickup truck tailgate is raised and lowered. The twisting and bending opens and closes the seven cable wire bundles located within the polyolefin tube. List and then comment on the possible reasons why the galvanized cable might corrode and break within a few years of initial use and describe what could be done to improve the design (see Figure P9.12D).

Corrosion of the internal steel surfaces of the crankcase of a particular engine is a problem. Someone suggests replacing the steel oil drain plug with one made of magnesium. You recommend that the steel plug be retained, but that one end of a small magnesium rod be embedded in the inside surface of the plug (see Figure P9.13D). Explain, briefly.

Illustrate design details to reduce corrosion from: (a) atmospheric corrosion in structural members, corners, welded joints, storage tanks; (b) concentration cell corrosion in liquid containers, baffles, pipes, and connections liquid containers (e.g., water heater); and (c) galvanic corrosion in joints and connections (rivets, bolts, and nuts) of dissimilar materials.

Write a report titled Mechanism of Corrosion addressing six basic causes of corrosion: (1) direct, (2) complex, (3) galvanic, (4) concentrated, (5) dezincification, and (6) fatigue and stress corrosion. Explain what can be done to overcome or minimize each.

Figure P9.16 shows a small pin pressed against a rotating disc. Describe how the friction coefficient between the pin and the disc could be measured. Give one use for such an apparatus.

Figure P9.17 shows two thin-walled cylinders where the top, constrained cylinder is pressed in an axial direction against the bottom, rotating cylinder. Describe how the frictional torque and the specimen temperature could be measured. Give one use for such an apparatus.

Figure P9.18 shows a rotating cylinder pressed against a second rotating cylinder. The cylinders rotate in opposite directions as shown. Describe how such an apparatus might be used.

A latching mechanism has steel mating surfaces of 100 and 300 Bhn rubbing back and forth over a distance of 30 mm each time the latch is operated. Lubrication is questionable (the surfaces are supposed to get a drop of oil every few months). The latch is operated an average of 30 times per day, every day (see Figure P9.19). Estimate the volume of metal that will wear away from the softer steel member during one year of use if the compressive load between the surfaces is 100 N.

Reconsider Problem 9.19, but estimate the volume of metal that will wear away for each of the steel mating surfaces, both of 300 Bhn. All other conditions are the same as in Problem 9.19.

Repeat Sample Problem 9.2, except use a rotating disk made of wrought-aluminum alloy 2014-T6 having a 135 Brinell hardness.

Repeat Sample Problem 9.2, except use a pin made of wrought-aluminum alloy 2011-T3 having a 95 Brinell hardness.

A steel part of 550 Bhn rubs back and forth over a distance of 3 in. in the slot of a 150 Bhn steel link. The link and part are components in a scissor mechanism used to raise and lower an automobile window. The sliding surfaces are unlubricated. The window is to operate an average of 2000 times per year. Estimate the volume of metal that will wear away from the softer steel link during one year if the compressive load between the surfaces is 20 lb.

Figure P4.1 in Chapter 4 (Problems) shows a 0.5-in.-diameter ball loaded in compression by a 4000 lb force against the left end of a bar where the cross section is \(1 \ \mathrm{in.} \times 1 \ \mathrm{in.}\) The balls are hardened steel and the steel bar has a yield strength of 50 ksi. What maximum contact stress will result from the load of 4000 lb?

Figure P4.2 in Chapter 4 (Problems) shows a 0.25-in.-diameter ball loaded in compression by a 1000 lb force against the left end of a bar where the cross section is \(1 \ \mathrm{in.} \times 1 \ \mathrm{in.}\) The balls are hardened steel and the steel bar has a yield strength of 50 ksi. What maximum contact stress will result from the load of 1000 lb?

The ball and socket joint at the end of a rocker arm has a hardened-steel spherical surface of 10-mm diameter fitting in a hard-bronze bearing alloy spherical seat of 10.2-mm diameter. What maximum contact stress will result from a load of 2000 N?

Reconsider Problem 9.27, but compute and plot the maximum contact stress for loads from 1800 N to 2000 N.

Figure P9.29 shows a Geneva indexing mechanism used, for example, on the indexing heads of machine tools. Each time the driving arm makes one revolution, the Geneva wheel (for the four-slot design illustrated) turns \(90^{\circ}\). The arm supports a rolling cylindrical hardened-steel pin that fits into the Geneva wheel slots. The pin is to have the same length and diameter. The wheel is made of heat-treated alloy cast iron (E = 140 GPa, v = 0.25). For a design contact stress of 700 MPa, determine the smallest acceptable pin diameter if the design overload torque (normal torque times safety factor) applied to the arm is \(60 \ \mathrm{N} \cdot \mathrm{m}\).

Repeat Problem 9.30 using a steel pinion and a cast-iron gear.

In a traction drive, a 1.0-in.-diameter cylindrical roller is preloaded against a 3.0-in.-diameter cylindrical roller. The steel rollers are 1.0 in. wide and the preload force is 50 lb. The axes of the cylinders are parallel. Calculate the maximum contact pressure and the width of contact. Also determine the maximum value of the subsurface shear stress.

Power is transmitted between two steel rollers pressed together, as in Figure 9.17. Loading is such that the maximum contact pressure is 2 GPa and the width of contact 1 mm. There is slight slippage, and the coefficient of friction is estimated to be 0.3. (a) What is the maximum completely reversed shear stress, \(\tau_{yx}\) , and how far on either side of the load line does it occur? (b) What is the maximum value of reversed tensile stress developed at the surface? (c) What is the maximum value of shear stress developed at the surface? (d) Explain briefly the kinds of surface deterioration that might occur?

A 15-mm-diameter, 20-mm-long steel roller is subjected to a load of 150 N per axial millimeter, as it runs on the inside of a steel ring of inside diameter 75 mm. Determine the value of the maximum contact pressure and the width of the contact zone.

A 25-mm-diameter cylindrical roller is preloaded against a 75-mm-diameter cylindrical roller in a traction drive. The steel rollers are 25 mm wide and the preload force is 200 N. The axes of the cylinders are parallel. Calculate the maximum contact pressure, the width, and the area of contact. Also determine the maximum value of the subsurface shear stress (see Figure P9.35).