Elementos De Máquinas Autor: Bernard J. Hamrock, Bo Jacobson, Steven R. Schmid. Análisis crítico de los problemas que se presentan en el vaciado de. Download Elementos de Maquinas Bernard k. Fundamentals of Fluid Film Lubrication / B.J. Hamrock. Bernard J. Hamrock .. cónicos y de tornillo sinfín; Diversos elementos de máquinas; Principios de.
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Jacobson, Bo Schmid, Steven R. Post on Jan views. There are a number of design considerations that can be included in this problem. Someexamples are considered here, but the student should not be restricted in the types of solutionspursued.
This type of problem is an excellent opportunity for brainstorming, where a group isencouraged to elementls all possible answers to the problem regardless of feasibility.
For example,the materials considered could include wood barrels, ceramic jugs or foil or plastic bags, as inintraveneous fluid containers. The transport containers for milk should be easy to handle and store as well as being easy to pourfrom without spilling. The material should be recyclable or be able to be burned leaving harmlesscombustion products. The obvious material choices are paper or plastic materials, although bernaard and metal cans can be considered as possibilities.
For a one liter container the standardtype Pure Pac maquinqs Tetra Pac Bric made of plastic carton is a good design. A one gallon container has to be compact to be easily stored in a refrigerator.
The width,depth, and height should be similar in size, which would be about mm x mm x mm. That size is too large to grip with one hand. Therefore, a one gallon container is preferably madeof a plastic with an integral handle. It should be able to accommodateboth a winter coat and a pair of trousers. It should function well but also be asinexpensive as possible. See the notes to maquins 1. If they are not hung simultaneously, a steel wire frame of triangular shape with a hook atthe top could be used.
The horizontal portion could be covered with a high friction coating or tapeor glue to keep the trousers from sliding off. For coats, a sturdier frame is needed, requiring either a larger gage of wire or pursuit ofanother alternative such as wood or plastic hangers. If the maquinass got too hot, they would attain a noticeable odor, and an oilerwould give the bearing a squirt of lubricant at the next train stop.
Schmid, Steven R.
What design philosophydoes this illustrate? The most obvious design philosophy is the Doctrine of Manifest Danger. This philosophysuggests that systems be designed so that a failure can be detected before it occurs.
In this case, adry bearing becomes hot, and the bad smell indicates a loss of lubricant before the bearing failureis catastrophic. It should be noted that other answers are possible. For example, the principal of uniformsafety suggests that the level of safety of all components be kept at the same level.
If failure ofone component, in this case a bearing, is imminent, then extra maintenance on this bearing isjustified by the principal of uniform safety.
Which design philosophy isbeing incorporated into the towing system design? Since the safety chain is used in addition to the towbar, it is an example of redundancy,and it is a passive system.
Furthermore, it is an example of a fail-safe design, because if thetowbar fails, the towed vehicle will follow the car and will not swerve into other lanes and collidewith other vehicles. Depending on the number of hours the drill is expected to be used before it isscrapped, different bearing arrangements will be chosen.
A rubber bushing has a hrlife. A small ball bearing has a hr life. A two bearing combination of a ball bearingand a cylindrical roller bearing has a 10, hr life. The cost ratios for the bearingarrangements bernardd 1: What is the optimum bearing type for a simple drill, asemiprofessional drill, and a professional drill?
This problem is fairly subjective, but there should be a realization that there is an increasein expected life for a professional drill versus a simple drill.
In fact, for certain users, a 50 hourlife is probably sufficient. Notice maquinqs the cost per time is highest for the rubber bushing and lowest for the ball bearingcylindrical bearing combination. However, the absolute cost is higher for the longer lastingcomponents, so the expected life must be assessed. Rough estimates based on expected lives areas follows.
The time from first spall to when the wholerolling-contact surface is covered with spalls is hr, and the time from then until a ballcracks is hr. What is the bearing lifea If high precision is required? This problem is fairly subjective, but there should be a realization that there is a decreasein expected life for the high precision drill, etc.
However, safety allowances of hours may be reasonable. Themaximum force transmitted from elemenros foot to the ski is N, but the snow conditionsare not known in advance, so the bending moment acting on the skis is not known.
Theweight of the skier and equipment is kg. Estimate the safety factor needed. There are two different approaches, that of section 1. Using the approach of section 1. Therefore, the largest safety factor, if there ispoor control of materials and loading, and if the consequences are sever, is given by Equation 1.
This means that no overstressing should ever occurdue to bending of the ski, so the safety factor could be chosen just above one. The allowable normal tensilestress in the wire gives an allowable force of ,N.
Find the safety factor that shouldbe used. If the wire breaks, people can be seriously hurtand expensive equipment can be destroyed. If the wire breaks, no peopleor expensive equipment can be damaged. Therefore, the required safety factor is obtained from Equation 1. Therefore, therequired safety factor is obtained from Equation 1.
This maqujnas an open-ended problem, and many different solutions are possible. Examples of fail safe products are: Examples of fail unsafe products include: Failure of the forced air circulation system exposes plant personnel to harmfulfumes. Thecost of the container is dd to the container wall thickness. The safety can beincreased either by making the container wall thicker or by mounting a reserve tray underthe container to collect the leaking acid.
Which is less costly, to increase the wall thickness or to mount a reservetray under the container? This problem uses the approach described by Equation 1.
Therefore, ifA is the cost of the container with thicker walls, then the cost of the container with a reserve trayisA1. How can that unit be rewritten by using the basicrelationships described by Newtons law for force and acceleration?
The only units needed are kg, m, and s. By definition, a Newton is a kilogram-meter per square second. Therefore, the unit for dynamicviscosity can be written as: Find at least one unit for kinematic viscosity. The only units needed are m and s. The units for kinematic viscosity can be written as: How many millimeters,centimeters, and decimeters df 1m? Also, how many square millimeters, squarecentimeters and square decimeters equal one square meter?
This is fairly straightforward; Table 1. Therefore, a square ds is: Calculate how long the sides of a cube must be to containthat volume.
SOLU Elementos de Maquinas – Hamrock, Bernard J. Jacobson, Bo Schmid, Steven R.
A tera mm3 is mm3. How fast will it travel in 1ps, 1 ns, and 1s? An interesting assignment is to have students submit string of the required length for thepicosecond and nanosecond cases. The distance traveled in a picosecond is: The viscosity ofthe lubricant is 0.
SOLU Elementos de Maquinas – Hamrock, Bernard J. Jacobson, Bo Schmid, Steven R. – [PDF Document]
Determine the friction force due to shearing of thelubricant film. Assume the friction force is the viscosity times the surface area timesvelocity of the moving surfaces and divided by the lubricant film thickness. Notes This problem is simple if consistent units are used. A ton can be misperceived; in metric units, a ton is kg, while in English units it is lbf. Since the units in this problem are metric, the metric interpretation is used. Thisproblem is not difficult as long as consistent units are used.
The velocity can be written as: The four passengers in the car weigh It is raining and the additional weight due to the water on the caris 1. Calculate the total weight of the car, maquinxs the weight of the passengersand the weight of the water, using four significant figures. Because slush and mud adhered to the bottom of the car, the weight was estimated to bekg. Calculate the force driving the car and indicate the accuracy. What is the critical sectiona If only P1 is applied?
This solution will ignore advanced concepts such as stress concentrations that would dd the fillet, since this material is covered later in the text.