Hydraulic Universal Testing Machine

Features Specifications: Hydraulic Universal Testing Machine

Specification:

Type			WE-300	WE-600
Max Testing Force (KN)			300	600
Accuracy Level			±1.0%
Measuring Range			060	0120
			0150	0300
			0300	0600
Distance between grips in tensile testing (mm)			550
			up to 850	up to 800
Range of specimen dimension	Round Specimen	Standard diameter of clamping(mm)	Φ20Φ35
		optional	Φ4Φ10 Φ8Φ20	Φ6Φ12 Φ10Φ20
	Fiat Specimen		30(Clip width 60)	40(Clip width 60)
Max distance between compression plats in compression test			500	450
Max distance between two bearing supports in bending test(mm)			600
Accessories of Bending test			optional
Max stroke of the piston(mm)			150	200
Max lifting/falling speed of piston(without loading)			100min/min
Lifting/falling speed of moving crossbeam			≥300mm/min
Load keeping time			≥30s
Hydraulic holding			optional
Max output of oil pump			2.9 L/min	3.9L/min
Measuring cabinet			CCTM-D
Size of dynamometer(mm)			1500×810×1920
Total capacity of power(KVA)			2.3	3.2
Gross weight of Main machine(kg)			2000	2600
Gross weight of Dynamometer cabinet(kg)			370

Hydraulic Jar Tester

Features Specifications: Hydraulic Jar Tester

The hydraulic service unit and the hydraulic jar tester are designed and manufactured on the basis of the advanced technolgy from same equipment abroad and the actual situation of the petroleum inustry in China.

The hydraulic service unit is an important tool used for disassembling/assembling,maintaining of all kinds of drill tools,pipe strings and thread connections for all kinds of downhole equipments in petroleum exploration and geolgical prospecting.It has the following functions suc as :high automatic level;large torque of screwing on/screwing out;wide diameter range for tubing fittings;without slippage or biting the working surface;quick-tightening screw thread;provide push-pull force for work piece.

The hydraulic jar tester is an necessary tool for testing of all kinds of drill tools.pipe strings.downhole tools ,Wtih advantages of simple ,reliable operation,large tonnage,it is especially suitable in piping station for testing the pulling and pressure performance of jar,shock absorber and intensifier.

BT-1 Surface

BT-1 Surface Modification System

The BT-1 is a complete industrial solution to medium to large scale surface preparation and processing with Plasma.

The large all aluminum chamber accommodates a generously sized active processing surface and as with our standard configuration of five levels of electrodes, provides you with 2100 square inches of useable plasma processing area

The compact footprint takes up very little space for the work it accomplishes.

Our standard vacuum pump is especially prepared for oxygen service. It is fully equipped with an N2 purge system, preventing any corrosive end products forming in the pump thus extending the service life and reducing the maintenance cycle.

Processing your product, whether it be small or large plastic parts, medical implants, wafers or electrical components, you will find that all are uniformly treated by the BT-1. Benefits to you are better adhesion or marking, cleaner parts with less labor and reduced chemical expense by eliminating unwelcome and often expensive chemical waste associated with cleaning and priming.

Our simple to use, intuitive touch screen interface has control over every aspect of the plasma process ensuring reliability and repeatability. Combined with the optional computer control, we offer process data review via the system PC or network.

We can custom configure the electrode to suit your production needs including custom sized horizontal electrodes, RIE (Reactive Ion Etch) and Semiconductor Lead Frame Carriers.

Low cost to maintain equates to low cost of ownership. Rest assured that Plasma Etch will be there for you as long as you own your system

New Honda City: Full details and new photos

New Honda City: Full details and new photos

The City currently competes very well head-to-head with Toyota Vios, despite the Vios being a next generation model, so Honda can be pretty confidence that it will compete well because of the new (and more) sporty look. The sub-compact market section makes up 43% of the sedan market or 47,795 units in the first half of 2008. Considering the size of the market, it is surprising that there are still only three main competitors; Honda City, Toyota Vios and Chevrolet Aveo. The Thai motor industry is made interesting by these compact cars in the market, and of course, Honda is the main contributor to this. Honda sent its Jazz in the beginning of the year and now it’s sending the latest 3rd generation City into the market. At this moment Honda is training their employees and dealers about the new City. This 3rd generation City is different from the previous model in that it doesn’t use the same body design as the Jazz. Although it’s harder to tell from the recent face-lifted model, the initial City shared very similar exterior proportions to the Jazz. This time the City will only share the same chassis and basic structure, along with engine technology. The engine is the same 1.5 ltr i-VTEC with electronic drive-by-wire. Honda is confident that the City will do really well, not only because the engine is good, but also thanks to the safety features on offer.

City Model Line-up The Thai City will share the engine and transmissions from the Jazz, the engine being the i-VTEC 120hp unit, while the transmission options will range from the 5-speed manual on the base S model, to the 5-speed automatic transmission complete with steering-wheel paddle shift on the top spec SV. The vast majority will be sold with the standard 5-speed auto. The base model S and mid-range V spec will be available with a beige interior, while the top-spec SV model will be set apart with black trim. The V will come in two versions, the V AT, and the V AT(SRS), with the SRS version being the first model that safety-conscious buyers will be able to consider, as the first that comes with dual airbags. The SV has airbags as standard. The City will have a new “Advanced Audio” system with 4 speakers, but only on the V and SV models. The SV will also have fog lights, indicator lights on the wing mirrors, paddle shift manual mode automatic transmission, etc.

Pricing In Thailand, the new 2009 City will be priced just below the Jazz. This should be easier for Honda to achieve now that the Jazz has gone up by $300 across the range. Although pricing hasn’t been confirmed yet, we can expect it to be in the $15,500 to $19,500 range.

Styling No surprises in any of these details. The small sedan market is pretty predictable these days. The surprise will probably come from the styling of the new City. The previous model was very awkward looking, and basically it was just a Jazz with a boot. Spy images of the new City would suggest that Honda is making the City much more of an individual, separating the design from the Jazz this time around.

The first photos AutoCar India has been paramount in breaking the news of the new Honda City. Their widely renderings (below) have also proven to be a spot on forecast of the actual Honda City. The whole team deserves a round of applause.

Specifications

Honda city 2008 S model: * beige tone interior * Remote Control Key with Immobilizer * 3rd rear brake indicator * 15 inch wheel with wheels cover * Sterio 2 din mp3 playing enable * Front Dual speaker

Honda City 2008 V model * beige tone interior * Remote Control Key with Immobilizer * 3rd rear brake indicator * 15 inch Alloy wheel * Advanced Audio system Sterio 2 din mp3 playing enable * Dual speaker of front and rear * chromium door handle * Driver seat low-high adjustment enable * Luggage under of rear passenger seat * ABS,EBD,BA * Dual airbag SRS (V AS only)

Honda City 2008 SV model * Black sporty looking tone interior * Remote Control Key with Immobilizer * 3rd rear brake indicator * 16 inch Alloy wheel * Fox lamp in the front and rear bumper * chromium exhaust pipe * Turn light indicator of side mirror * Switch steering * Paddle Shift * Rear seater can be folded 60:40 enable * Incline forward rear back seat * Front armrest * Map lighting * Advanced Audio system Sterio 2 din mp3 playing enable * Dual speaker of front and rear * chromium door handle * Driver seat low-high adjustment enable * Luggage under of rear passenger seat * ABS,EBD,BA * Dual airbag SRS (V AS only)

Honda S2000

Honda S2000

Carrying concept of street very racing jell and triffle, modification of Honda conducted S2000 the the owner of To day this Chandra is true spelled out members by impression and is properly placed as one of the King Nominee in Event Auto black through 2008 Field series. More than anything else, in test of dyno that goes on Sunday ( 17 / 8) night, noted from twice attempt, result of experience 195.8 Hp/ 146 kwh can make this roadster as quickest among is fourth [of] nomination of King other. " We enough satisfy with this result, almost matching with the one which we expect," express Jefri ( 30), one of [the] modificator deputizing To day of[is the owner, dyno before test that goes on Sunday ( 17 / 8) evening rather happy. (It) is true, from two [done/conducted] attempt, sport car of year 2002 this without direct hackneyed basa [of] best performance show above machine roller measure of energy race the car. Reliing on some sector modification race like Swap F20C DOHC VTEC, Supercharger Vortech, Koopling Exedy alumunium, radiator panel of ARC, Panel of Brake ARC, Header HKS 4-1 supported also with Twin Muffler Tanabe and final of Drive JS Racing 4.7 : 1, result of which [is] obtained [by] S2000 in both opportunity spelled out members enough impresif. That is [at] first test 175,5 Hp and [both/ second] 195,8 Hp.




This acquirement in comparison with all other King Nominee which is mean only can book number; 88,55 HP ( Honda Civic Tanata); 86,5 HP ( Toyota Harrier Priority-Sabrom) and 49,9 HP ( Kia Picanto), it is true make the the S2000 Illusion roadster as quickest King Nominee in ABT Field 2008.




Modification which also figure in Body Kit C-West, Engine Hood carbon, Mugen Hardtop, holografis rainbow airbrush, Velg Pros of Device Time Attack Edition 18x18", Tires proxes Toyo 225/18/40, Hot Bits Sport of suspension at part of foot/feet foot/feet and eksterior, and also Shift MUGEN knob, Seats Bride Low Max ( cevlar carbon), along with panel of full carbon at its interior sector this previously this can acquirement. in comparison with all other King Nominee which is mean only can book number; 88,55 HP ( Honda Civic Tanata); 86,5 HP ( Toyota Harrier Priority-Sabrom) and 49,9 HP ( Kia Picanto), it is true make the the S2000 Illusion roadster as quickest King Nominee in ABT Field 2008.

Brinell Test

Brinell Test

The Brinell test relies on mechanical or hydraulic loads as large as 3000 Kg. acting through a 10 mm hard steel or carbide ball. In order to compensate for variations in the response of materials to the application of the load, the time for which the load is applied is specified. For hard materials such as steel, a 30-second loading period is adequate. Softer metals and alloys such as brass or aluminum require about 60 seconds. After the load is removed, the diameter of the impression made by the ball is measured in millimeters. The Brinell hardness number, abbreviated as BHN, is the quotient of the load, P (kg), divided by the area, A, of the impression:

	P
BHN =	_______________________________
	( D- (D2 - d2) 1/2 ) p D/2

Where D is the diameter of the ball penetrator (mm) and d is the diameter of the impression(mm). In practice, the BHN is read directly from a table listing different values of d for various values of load, P.

The Brinell test makes a large impression on the surface of the piece tested. Unless such a large impression can be tolerated, and often it can not, the test is destructive. However, the large impression is advantageous because it gives a more representative result than would a smaller impression which would be more sensitive to local soft or hard inhomogeneties. The size of the impression also renders the test less sensitive to the presence of rough surface finish and mill scale than is the case when tests are used which rely on small indentations.

Operation of Brinell Testing Machine:

(1) Turn air on

(2) Set the required load on the dial.

Note: For steel and other hard materials the load is 3,000 kg. for 30 seconds. For non-ferrous materials a 500 kg. load is used for 60 seconds. Thin specimens should not be tested by this method.

(3) Place the specimen on the anvil and apply a preload by bringing the specimen surface to contact with the ball penetrator.

(4) Pull the load knob and apply the appropriate timing at that load level.

(5) Release the load by pushing the load knob back into the initial position.

(6) Remove the specimen and measure the diameter of the indentation. The Brinell Microscope reads in millimeters. Take several readings and average them.

(7) Look up BHN from chart or calculate from the formula.

The following is a sample hardness data as presented in a laboratory report. Use the same format in your report.

Material	Rockwell Hardness Scale, Major Load, Type of Penetrator	Rockwell Hardness Number	Brinell Hardness Number	Brinell Load, Indentation Diameter	Tensile Strength (Ksi)
Example 1 (steel)	Rc 150 Kg C-Brale	51 or Rc 51			253
Example 2 (steel)	15 N 45 Kg N-Brale	42 or 15N42			182
Example 3 (Steel)			352	3000 Kg 3.25 mm	176

Hardness Testing

Hardness Testing

Objectives:

1. To understand what hardness is, and how it can be used to indicate some properties of materials.

2. To conduct typical engineering hardness tests and be able to recognize commonly used hardness scales and numbers.

3. To be able to understand the correlation between hardness numbers and the properties of materials.

4. To learn the advantages and limitations of the common hardness test methods.

Introduction:

It is a common practice to test most materials before they are accepted for processing, and before they are put into service to determine whether or not they meet the specifications required. One of these tests is for hardness. The Rockwell and Brinell machines are those most commonly used for this purpose.

Equipment:

1. Rockwell Standard Hardness Testing Machine,

2. Rockwell Superficial Hardness Testing Machine,

3. Rockwell Calibration Test Blocks,

4. Hardness Test Specimens of various metal alloys.

Procedure and Laboratory Report:

1. Understand thoroughly the operation of each machine, and check its operation before proceeding.

2. Check the calibration of the Rockwell Machines with Standard Calibration Test Blocks for the scale selected.

3. Using the appropriate scale

(a) Check the hardness of each test specimen on a Rockwell Test Machine.

(b) Tabulate the results.

(c) Convert all readings to either R_B or R_C values.

4. Using Brinell Machine

(a) Find the hardness of the cast aluminum by converting the diameter of the impression to Brinell Hardness Number (BHN).

(b) Convert the BHN to Rockwell B (R_B) scale.

(c) Repeat step 4(a) for steel sample and find the BHN.

(d) Convert BHN for steel sample to Rockwell C scale (R_c).

5. Using the hardness conversion chart, find the Tensile Strength of the steel samples.

Note: For each hardness number, select three locations on the sample. Read the hardness number at each location and take the average of the three readings.

Background:

A commonly accepted engineering definition of hardness is the resistance to indentation. Resistance to indentation is a function of the mechanical properties of the material, primarily its elastic limit and to a lesser extent, its work-hardening tendency, and the modulus of elasticity. For a given composition with a known history it is possible to relate the elastic limit (for practical purposes, the yield strength) to the tensile strength, ductility, and toughness. Hence, the hardness tests can provide information from which many important mechanical properties can be derived. Since the hardness test can be conducted easily and quickly, they are very popular and are used to control processing and for inspection and acceptance of materials and components.

The common hardness tests rely upon the slow application of a fixed load to an indenter which is forced into the smooth surface of the specimen. Upon removal of the load either the area or the depth of penetration is measured as an indication of resistance to the load. Three types of tests are discussed below.

Rockwell Tests:

The Rockwell tests depend upon the measurement of the differential depth of a permanent deformation caused by the application and removal of differential loads. Various penetrator and load combinations are used to adapt different Rockwell tests to materials of varying hardness and thickness. The penetrators include a cone-shaped diamond , known as a Brale, and hard steel balls from 1/16-inch to 1/2 -inch in diameter.

Standard Rockwell Test:

The Standard Rockwell tests use a light load of 10 Kg to seat the penetrator firmly in the surface of the specimen. This load is known as the minor load. After the application of the minor load, the depth gauge is zeroed and a larger load, known as major load, is applied and then removed. While the minor load still acts, the depth of permanent penetration is measured. The depth gauge which measures the penetration is calibrated to read in hardness numbers directly rather than in inches. Major loads for Standard Rockwell tests are 60, 100 or 150 Kg. The diamond penetrator is marked as "C-Brale".

Superficial Rockwell Test:

Superficial Rockwell tests are used for measuring the hardness of thin specimens and specimens which have only a thin hardened surface layer )known as a case) on a soft base (known as a core). The ball penetrators available for superficial testing are the same as for standard testing. The diamond brale is marked as "N-Brale". The loads for superficial testing are much lower than for standard testing, being 3 Kg for the minor load and 15, 30 or 45 Kg for the major load.

The wide range of combinations of penetrators and loads permit application of Rockwell Test to an equally wide range of materials of varying hardness. The diamond penetrator makes it practical to test the hardest steels and the large balls permit testing of soft metals and even plastics. Generally the Rockwell test is considered to be nondestructive because the light loads and small penetrators produce very small impressions. However, because of the small impressions several readings should be taken to obtain a representative result. Furthermore, the smaller the impression, the greater is the care necessary in preparing the surface. Apart from any special effort required for surface preparation, the Rockwell test is easier and more quickly performed than the Brinell test.

Operation of Hardness Testing Equipment:

(1) Select the correct combination of weights (at the rear of the machine) and penetrators (diamond brale, 1/16-inch ball, etc.) for the hardness scale you wish to use. The numbers given in black represent the scales that use brale and the numbers given in red represent the scales that use ball penetrators.

(2) Make certain that the crank(4) is in forward position (nearest to you).

(3) Place sample on the anvil.

(4) Slowly turn the wheel spokes(1) clockwise. This raises the anvil and sample toward the penetrator tip. After contact is gently made, continue raising sample until small pointer(5) is about in line with small black dot and large pointer(6) is within colored sector(7). The minor load has now been applied to the sample.

(5) After step 4, large pointer(6) on the dial is nearly vertical. Now, turn the knurled collar(2) until "SET" line on the dial scale is in line with large pointer(6).

(6) Depress trip lever(3). This triggers the mechanism that applies the major load. Crank(4) will automatically move away from you.

(7) After the crank(4) has come to rest (against a "stop" and away from you), gently pull the crank toward you as far as it will go. If this is done abruptly, a false reading will be obtained because of jarring.

(8) Now record the scale reading of large pointer(6). The black scale is read for the diamond penetrator (Example: Rockwell C), and the red scale is for ball penetrators (Example: Rockwell B).

(9) Remove the minor load, which remains on the specimen, by lowering the anvil (Turn the wheel(1) counterclockwise). Move the sample to position for next test and repeat the steps above.

Crystal Imperfections

Crystal Imperfections

The most important crystal imperfections are:

Vacancies

Interstitials

Dislocations

Vacancies:

Vacancies are simply empty atom sites as shown in Figure 1.The lattice vacancies are a stable feature of metals at all temperatures above absolute zero. By successive jumps of atoms, just like playing Chinese checkers, it is possible for a vacancy to move in the lattice structure and therefore play an important part in diffusion of atoms through the lattice.

Vacancies are not only present as a result of solidification but can be produced by raising the temperature or by irradiation with fast moving nuclear particles.

Figure 1. Vacancy crystal defect.

Interstitials:

It is possible that some atoms may fall into interstitial positions or in the spaces of the lattice structure which may not be used by the atoms of a specific unit cell as shown in Figure 2. Interstitials tend to push the surrounding atoms farther apart and also produce distortion of the lattice planes.

Interstitial atoms may be produced by the severe local distortion during plastic deformation as well as by irradiation.

Figure 2. Interstitial crystal defect.

Dislocations:

A dislocation may be defined as a disturbed region between two substantially perfect parts of a crystal. A dislocation is a linear defect around which some of the atoms are misaligned.

Two simple types of dislocation are :

Edge dislocation

Figure 3. Edge dislocation

Screw dislocation

Figure 4. Screw dislocation

Dislocations can be observed in crystalline materials using electron-microscopic techniques. Virtually all crystalline materials contain some dislocations that were introduced during solidification, during plastic deformation, and as consequence of thermal stresses that result from rapid cooling.

The importance of dislocations to the metal user is that dislocation interactions within a metal are a primary means by which metals are deformed and strengthened. When metals deform by dislocation motion, the more barriers the dislocations meet, the stronger the metal.

Deformation by dislocation motion is one of the characteristics of metals that make them the most useful engineering materials. The metallic bond is such that strains to the crystal lattice are accommodated by dislocation motion. Many metals can tolerate significant plastic deformation before failing.

Crystal Formation

Crystal Formation

Crystallization is the transition from the liquid to the solid state and occurs in two stages:

1. Nucleus formation

2. Crystal growth

Atomic motion in the liquid state of a metal is almost completely disordered. Although the atoms in the liquid state do not have any definite arrangement, it is possible that some atoms at any given instant are in positions exactly corresponding to the space lattice they assume when solidified. As the energy in the liquid system decreases, the movement of the atoms decreases and the probability increases for the arrangement of a number of atoms into a characteristic lattice for that material. The energy level at which these isolated lattices form is called the freezing point.

(a)	(b)
(c)	(d)

Figure 1. Mechanism of solidification (square grids represent the unit cells)

(a) Nucleus formation

(b), (c) Growth of the crystallites

(d) Grain boundaries

Now consider a pure metal at its freezing point where both the liquid and solid states are at the same temperature. The kinetic energy of the atoms in the liquid and the solid must be the same, but there is a significant difference in potential energy. Kinetic energy is related to the speed at which the atoms move and is strictly a function of temperature. The higher the temperature, the more active are the atoms and the greater is their kinetic energy. Potential energy, on the other hand, is related to the distance between atoms. The greater the average distance between the atoms, the greater is their potential energy. The atoms in the solid are much closer together, so that solidification occurs with a release of energy. This difference in potential energy between the liquid and solid states is known as the latent heat of fusion.

When the temperature of the liquid metal has dropped sufficiently below its freezing point, stable aggregates or nuclei appear spontaneously at various points in the liquid. These nuclei, which have now solidified, act as centers for further crystallization. As cooling continues, more atoms tend to freeze, and they may attach themselves to already existing nuclei or form new nuclei of their own. Each nucleus grows by the attraction of atoms from the liquid into its space lattice. Crystal growth continues in three dimensions, the atoms attaching themselves in certain preferred directions, usually along the axes of a crystal. This gives rise to a characteristic treelike structure which is called dendrite.

Figure 2. Process of crystallization by nucleation and dendritic growth.

Since each nucleus is formed by chance, the crystal axes are pointed at random and the dendrites will grow in different directions in each crystal. Finally, as the amount of liquid decreases, the gaps between the arms of the dendrite will be filled and the growth of the dendrite will be mutually obstructed by that of its neighbors. This leads to a very irregular external shape. The crystals found in all commercial metals are commonly called grains because of this variation in external shape. The area along which crystals meet, known as the grain boundary, is a region of mismatch. The boundaries are formed by materials that are not part of a lattice, such as impurities, which do not show a specific grain pattern. This leads to a noncrystalline (amorphous) structure at the grain boundary with the atoms irregularly spaced. Since the last liquid to solidify is generally along the grain boundaries, there tends to be a higher concentration of impurity atoms in that area.

Figure 3. Grain Boundary

Figure 4. Formation of dendrites in a molten metal.

Figure 5. Dendrites observed at a magnification of 250 x.

Secondary Bonds

Secondary Bonds:

Secondary bonds are much weaker than primary bonds. They often provide a "weak link" for deformation or fracture. Example for secondary bonds are:

Hydrogen Bonds

Van der Waals Bonds

Hydrogen Bonds

Hydrogen bonds are common in covalently bonded molecules which contain hydrogen, such as water (H2O). Since the bonds are primarily covalent, the electrons are shared between the hydrogen and oxygen atoms. However, the electrons tend to spend more time around the oxygen atom. This leads to a small positive charge around the hydrogen atoms, and a negative charge around the oxygen atom. When other molecules with this type of charge transfer are nearby, the negatively charged end of one molecule will be weakly attracted to the positively charged end of the other molecule. The attraction is weak because the charge transfer is small.

Figure 6. Hydrogen bonds.

Van der Waals Bonds

Van der Waals bonds are very weak compared to other types of bonds. These bonds are especially important in noble gases which are cooled to very low temperatures. The electrons surrounding an atom are always moving. At any given point in time, the electrons may be slightly shifted to one side of an atom, giving that side a very small negative charge. This may cause an attraction to a slightly positively charged atom nearby, creating a very weak bond. At most temperatures, thermal energy overwhelms the effects of Van der Waals bonds.

Van Der Waals bonding is a secondary bonding, which exists between virtually all atoms or molecules, but its presence may be obscured if any of the three primary bonding types is present. Secondary bonding forces arise from atomic or molecular dipoles. In essence, an electron dipole exists whenever there is some separation of positive and negative portions of an atom or molecule. When an electron cloud density occurs at one side of an atom or molecule during the electron flight about the nucleus, Van Der Waals forces are generated. This creates a dipole wherein one side of the atom becomes electrically charged and the other side has deficiency of electrons and is considerably charged positive. The atom is distorted as shown in Figure 7.

Figure 7. Van der Waals Bond

Lattice Structures

Atoms are the building blocks of all materials. They are put together in a great variety of ways and bonded or "held together" by cohesive forces in a manner characteristic of a particular material. In a liquid state the atoms of metal are said to be in somewhat random arrangement, having short-range order. At times several unlike atoms will arrange themselves in the characteristic pattern of a particular metal. However, this is a probability event. Since the forces are weak and there is much activity taking place, they soon separate and re-form again. This phenomenon of random grouping, scattering, and regrouping for short periods of time is characteristic of the liquid state. As the random grouping mechanism becomes less frequent and the atomic movement of unlike atoms become more agitated, the material may become a gas.

As the energy input decreases, the random movement of the unlike atoms becomes less frequent, the bonding becomes stronger, and ordered arrays of atoms form lattices.

A crystal is a repeating array. In describing this structure we must distinguish between the pattern of repetition (the lattice type) and what is repeated (the unit cell). The most fundamental property of a crystal lattice is its symmetry. In three-dimensions, unit cells stack like boxes, filling the space, making the crystal. The different colors are just to show the separate boxes - each unit cell is identical.

Figure 1. Cubic Lattice Structure	Figure 2. Hexagonal Lattice Structure

If we take a unit cell and stack it, we produce a lattice. Notice that once we begin stacking the unit cells, we never change the orientation of any subsequent unit cells as they stack. In other words, once the orientation of a unit cell is determined, all unit cells within that lattice have the same orientation.

Figure 3. Orientation of the unit cells in a lattice.

Unit Cell: When a solid has a crystalline structure, the atoms are arranged in repeating structures called unit cells, which are the smallest units that show the full symmetry of a crystal.

Lattice: The three dimensional array formed by the unit cells of a crystal is called lattice.

When a crystalline solid starts to form from the molten or gaseous state, these unit cells will tend to stack in a three-dimensional array, with each cell perfectly aligned, and they will form a crystal. If crystals are growing in a melt at the same time, the crystals will eventually meet and form grains. The junction of the grains is called grain boundaries.

The majority of metals have one of three well-packed crystal structures:

Face-centered cubic (F.C.C.)

Body-centered cubic (B.C.C.

Hexagonal-close-packed (H.C.P.)

Figure 4. Face Centered Cubic (F.C.C) Lattice Structure

To view the FCC crystal structure visit the following links:

Figure 5. Body Centered Cubic (B.C.C) Lattice Structure

To view the BCC crystal structure visit the following links:

Figure 6. Closed Packed Hexagonal (C.P.H) Lattice Structure To view the CPH lattice structure visit the following links: