Malzeme 1

Malzeme 1 - 30.11.2011 tarihli derste işlenen "Yapı Kusurları" adlı powerpoint dosyası.

http://hotfile.com/dl/136391845/84e0c08/yapkusurlar.ppt.html

Mukavemet 1

Doç.Dr. Recep Güneş'hocamızın kişisel sitesinde(http://me.erciyes.edu.tr/recepgunes/) yayımladığı mukavemet 1 soru ve cevapları tek dosya halinde buradan indirebilirsiniz.


http://hotfile.com/dl/136031887/fe83baf/mukavemet.zip.html

Friction

 Whenever one surface moves over another, a force is set up which resist the movement.This force, which we call friction always opposes motion.It exists in every machine.It can be reduced by lubrication but never  completely removed.In general, the force opposing motion is slightly greater before one surface starts moving over another surface than after movement has started.This slightly greater force is called static friction.The force which must be overcome to keep one surface moving over another is known as sliding friction.Static friction is greater than sliding friction.
 The value of sliding friction depends on the nature of the two surfaces which touch each other.Thus friction between two rough planks can be lessened if they are made smooth.Sliding friction is independent of the area of surface in contact.In theory a small brake pad will exert as much braking force as a large one of greater surface area.In practice a small pad will wear down more quickly and therefore is not used.One other law of friction should be noted.We can make normal reaction between two surfaces in contact twice  as large by doubling the mass carried by one surface.If we do so we find that sliding friction between the surface is also doubled.If we halve the mass carried, sliding friction is also halved.This shows that sliding friction is proportional to the reaction between the surface in contact.

Vectors

There are many complex parts to vector analysis and we aren't going there. We are going to limit ourselves to the very basics. Vectors allow us to look at complex, multi-dimensional problems as a simpler group of one-dimensional problems. We will be concerned mostly with definitions The words are a bit strange, but the ideas are very powerful as you will see.

Math and science were invented by humans to describe and understand the world around us. We live in a (at least) four-dimensional world governed by the passing of time and three space dimensions; up and down, left and right, and back and forth. We observe that there are some quantities and processes in our world that depend on the direction in which they occur, and there are some quantities that do not depend on direction. For example, the volume of an object, the three-dimensional space that an object occupies, does not depend on direction. If we have a 5 cubic foot block of iron and we move it up and down and then left and right, we still have a 5 cubic foot block of iron. On the other hand, the location, of an object does depend on direction. If we move the 5 cubic foot block 5 miles to the north, the resulting location is very different than if we moved it 5 miles to the east. Mathematicians and scientists call a quantity which depends on direction avector quantity. A quantity which does not depend on direction is called a scalar quantity.

Vector quantities have two characteristics, a magnitude and a direction. Scalar quantities have only a magnitude. Whencomparing two vector quantities of the same type, you have to compare both the magnitude and the direction. For scalars, you only have to compare the magnitude. When doing any mathematical operation on a vector quantity (like adding, subtracting, multiplying ..) you have to consider both the magnitude and the direction. This makes dealing with vector quantities a little more complicated than scalars.

On the slide we list some of the physical quantities discussed in the Beginner's Guide to Aeronautics and group them into either vector or scalar quantities. Of particular interest, the forces which operate on a flying aircraft, the weight, thrust, andaerodynmaic forces, are all vector quantities. The resulting motion of the aircraft in terms of displacement, velocity, and acceleration are also vector quantities. These quantities can be determined by application of Newton's laws for vectors. The scalar quantities include most of the thermodynamic state variables involved with the propulsion system, such as thedensity, pressure, and temperature of the propellants. The energy, work, and entropy associated with the engines are also scalar quantities.

Vectors have magnitude and direction, scalars only have magnitude. The fact that magnitude occurs for both scalars and vectors can lead to some confusion. There are some quantities, like speed, which have very special definitions for scientists. By definition, speed is the scalar magnitude of a velocity vector. A car going down the road has a speed of 50 mph. Its velocity is 50 mph in the northeast direction. It can get very confusing when the terms are used interchangeably! Another example is mass and weight. Weight is a force which is a vector and has a magnitude and direction. Mass is a scalar. Weight and mass are related to one another, but they are not the same quantity.`

While Newton's laws describe the resulting motion of a solid, there are special equations which describe the motion of fluids, gases and liquids. For any physical system, the mass, momentum, and energy of the system must be conserved. Mass and energy are scalar quantities, while momentum is a vector quantity. This results in a coupled set of equations, called the Navier-Stokes equations, which describe how fluids behave when subjected to external forces. These equations are the fluid equivalent of Newton's laws of motion and are very difficult to solve and understand. A simplified version of the equations called the Euler equations can be solved for some fluids problems.

Corrosion

 Corrosion attacks all engineering materials, especially metals.Corrosion is any chemical action which harms the properties of a material.It reduces the life of a material and increases the cost of a structure.For example, a steel bridge must be repainted regularly to protect it from rust.Various metals have therefore been developed to resist corrosion.Among them are the stainless steels.These metals contain from 12 to 35% chromium which forms a very thin layer or film of chromium oxide on the surface of the metal.This film protects the metal from corrosion.Alloys made from copper and nickel are also corrosion-resistant.For example Monel metal, which contains roughly 60% nickel and 30% copper, is resistant to both fresh and salt water corrosion.It is therefore used for marine engine parts, and for surface like ship' propellers which are in contact with sea water.Cupronickels, which contain a smaller proportion of nickel, have a similar resistance to fresh  and sea water.They are mainly used to make tubes.

 When two different metals touch other in the presence of moisture, corrosion occurs.This type of corrosion is known as galvanic or electrolytic corrosion because it has an electrical cause.The metals and the moisture act like a weak battery and the chemical action which results corrodes one of the metals.If, for example, aluminium  sheets are riveted with copper rivets, the aluminium near the rivets will corrode in damp conditions.

 No material can be completely corrosion-resistant.Even stainless steels will corrode.Engineers can, however, fight corrosion.For example, they can use high-purity metals because these metals are more resistant than alloys.They can also make sure that two dissimilar metals are not allowed to touch each other.Finally engineers can protect the surfaces of metals in many different way.One of the most common methods is to paint them.