LAB REPORT GUIDE MECHANICAL ENGINEERING DEPARTMENT

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1 LAB REPORT GUIDE MECHANICAL ENGINEERING DEPARTMENT The following template, including the title page, has been prepared to guide the students for writing good experimental lab reports in mechanical engineering lab courses. This guide will help to assess how well each student group learning (b) and (g) outcomes. (b) Ability to design and conduct experiments, as well as analyze and interpret data. (g) Ability to communicate effectively, both orally and in writing.

2 TITLE PAGE OF LAB REPORT Mechanical Engineering Department Course Name: Semester and Year: Lab. Group: Material Heat Mechanical Name of Lab Instructor: Date of Experiment Performed: Date of Report Submitted: Title of Experiment: Name of Team Leader: Instructor Comments: Names of Group Members: Grade:

3 EXPERIMENTAL METHODS FORMAT FOR LABORATORY REPORTS Title page: Use the standard cover page downloadable from course website: (0 point) A laboratory report must contain the following sections in the given order: Results: max. 3 pages Give the results of your experiment and discuss them. Compare and contrast your observations with those reported in the relevant literature. Use tables and figures as necessary. (30 point) Discussions:. Answer the questions at the end of your experiment sheet in this section.(50 point) References: References must be numbered in square bracets in the text and figure/table captions in increasing order and must be listed in the same order in the end of your report in the following format: (0 point). W.D. Callister, Jr., Fundamentals of Materials Science and Engineering An Integrated Approach, John Wiley & Sons, Inc., USA, 005.

4 I PANEL RADIATOR Purpose Investigating the heating power of a panel radiator used for heating at the buildings from room temperature to the steady state on time dependent basis. Experiment The experimental set up is depicted in the figure below. Experimental set up includes various type vanes, thermometers, manometer, pump, panel radiator, flow meter and an electric heater. The heating power of the heater is W. After the flow rate of the system reaches a constant value the input and output temperature values of the water will be recorded periodically. Data Sheet Initial Measurement st minute nd minute 3 rd minute 4 th minute 5 th minute 6 th minute 7 th minute 8 th minute 9 th minute 0 th minute T i ( o C) T o ( o C) Question. Determine thermal efficiency of the system.. Draw thermal power time graph.

5 II WATER WATER HEAT PUMP Purpose Calculating the COP value of the heat pump by maing measurements at the water/water heat pump and understanding woring principle of the heat pumps and the laws of thermodynamics. Theoretical Knowledge Mechanical compressor vapor compression heat pump system wors according to the compression condensation and expansion vaporization principles liewise mechanical compressor vapor compression refrigeration machine. Thus refrigerants are used in the heat pump applications. The schematic view of a heat pump is shown below. The refrigerant, whose pressure decreases at the expansion valve, is carried to the evaporator section by the pipes. The heat load of the environment is removed in the evaporator section, so the temperature of the refrigerant rises and it vaporizes. When it is aimed to remove the heat from water, that water is circulated outside of the evaporator or evaporator is submerged. If more heat transfer rate is desired, the outside water is circulated in the opposite direction to the refrigerant. Vaporized refrigerant transferred to the compressor section by the pipes. In the compressor, vaporized refrigerant is compressed that s why the temperature and pressure values of the refrigerant increases. The refrigerant with the high temperature and pressure values carried to the condenser. In the condenser, the refrigerant gives its heat to the environment which is desired to be heated. When it is aimed to achieve hot water, water is circulated outside of the condenser or condenser is submerged. In the condenser section the refrigerant condenses and becomes saturated liquid. Than refrigerant is sent to expansion valve again and its temperature and pressure decreases.

6 Experiment The main equipments of the water/water heat pump are listed below. a) Compressor Brand Model : Emerson Copeland KCE444HAG Power : 0 30 V,50 Hz Power Consumption: 5 W Cooling Capacity: 96 cal/h b) Heat Exchanger Brand Model: Uğura 7000 Capacity: 7000 BTU c) Throttling Valve Brand Model: ALCO TI MW55 Refrigerant: R34 a Outlet Diameter: mm Woring Range: o C d) Filter Dryer Brand Model: ALCO FDB 05 e) Low and High Pressure Pressurestat Brand Model: ALCO PS L7A

7 f) Manometer Brand Model: ALCO MR 06 DS g) Ampermeter Brand Model: SAYPORT DP3 96A Auxilary Supply: V Measurement Range: 9000/5A h) Voltmeter Brand Model: SAYPORT DP3 96V Auxilary Supply: V Measurement Range:0 600 V i) Cosψ meter Brand Model: SAYPORT DP3 96A Auxilary Supply: V Measurement Range: İn/Kap j) Digital thermometer channel In this experiment, the water flow rates, which go to the heat exchangers, are adjusted by the help of vanes and the system is operated. When the system reaches steady state conditions, the measurement data will be recorded in the tables that are shown in the following section.

8 Questions According to the collected data from the experiment, a) Compressor power, evaporator and condenser capacities will be calculated b) COP of the heat pump will be calculated Table : Temperature Data No Definition Values T Compressor Gas Outlet Temp. T Compressor Gas Inlet Temp. T 3 Condenser Gas Outlet Temp. T 4 Condenser Water Inlet Temp. T 5 Evaporator Water Inlet Temp. T 6 Throttling Valve Outlet Temp. T 7 Condenser Water Outlet Temp. Evaporator Water Outlet Temp. T 8 Table Compressor Power Data Definition Ampermeter Voltmeter Cosψ meter Values Table 3 Mass flow rates Definition Mass flow rate of condenser Mass flow rate of evaporator Values

9 Humidifying with Water III AIR CONDITIONING Fundamentals of Air Conditioning To choose the right device for air conditioning, it is needed to calculate heating and cooling loads correctly and certain. Basic elements for air conditioning are listed below;. Temperature ( Heating at winter, cooling at summer. Humidity (humidifying at winter, dehumidifying at sumer) 3. Air Movements (circulation) 4. Purification of air (Filtration) 5. Ventilation (Clean air input) HEAT RECOVERY AIR CONDITIONER EDUCATION SET SCHEME exhaust t 5 t 3 Heat exchanger t t 6 t 4 t Pre heater Exhaust damper cooler humidifier t 7 t 8 t 9 t 0 t t radiator fan inner climate Fresh air ent. Final cooler

10 TECHNICAL PROPERTIES Fan brand and model Fan motor power and rpm 45 W, 350 rpm 3 Fan capacity 850 m 3 /h 4 Preheater power 055 W 5 Finalheater power 055 W 6 Humidifier type Water injection type 7 Heatexchanger Type and Material Aluminum plates 8 Heatexchanger Model BT AL 03 N 0 M T AZ SC 9 Dimensions of Heatexchanger 300x300x0 0 Heat exchanger series number and width 7 series 7,5 mm Damper dimensions 00x30 mm

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12 Experiment. Purpose Observing the changes in the air during the humidifying process.. Required Devices and Materials Air speed meter (anemometer) Psychrometric chart 3. Question What is the mass flow rate of the moisture added to the air? Measurement Number Dry Wet h ν ω Inlet temperature, t [ 0 C], t [ 0 C] Heat exchanger exhaust temp., t 3 [ 0 C], t 4 [ 0 C] Cooler hum. ex. Dry temp., t 7 [ 0 C], t 8 [ 0 C] Velocity of air, u [m/s] Specific volume of air,[m 3 /g] Line Voltage, U [V] Measurement

13 ROUGHNESS MEASUREMENTS Objectives. To expose student about surface roughness measurement theory..introduction Roughness is a measure of the texture of a surface. It is quantified by the vertical deviations of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small the surface is smooth. Roughness is typically considered to be the high frequency, short wavelength component of a measured surface (see surface metrology).roughness plays an important role in determining how a real object will interact with its environment. Rough surfaces usually wear more quicly and have higher friction coefficients than smooth surfaces. Roughness is often a good predictor of the performance of a mechanical component, since irregularities in the surface may form nucleation sites for cracs or corrosion. Although roughness is usually undesirable, it is difficult and expensive to control in manufacturing. Decreasing the roughness of a surface will usually increase exponentially its manufacturing costs. This often results in a trade off between the manufacturing cost of a component and its performance in application. Measurement. Roughness may be measured using contact or non contact methods. Contact methods involve dragging a measurement stylus across the surface; these instruments include profilometers. Non contact methods include interferometry, confocal microscopy, electrical capacitance and electron microscopy. Principle of a contacting stylus instrument profilometer: A cantilever () is holding a small tip () that is sliding along the horizontal direction (3) over the object's surface (5). Following the profile the cantilever is moving vertically (4). The vertical position is recorded as the measured profile (6) shown in light green.

14 Setch depicting how a probe stylus travels over a surface. For D measurements, the probe usually traces along a straight line on a flat surface or in a circular arc around a cylindrical surface. The length of the path that it traces is called the measurement length. The wavelength of the lowest frequency filter that will be used to analyze the data is usually defined as the sampling length. Most standards recommend that the measurement length should be at least seven times longer than the sampling length. The assessment length or evaluation length is the length of data that will be used for analysis. Commonly one sampling length is discarded from each end of the measurement length. Roughness Parameters. Each of the roughness parameters is calculated using a formula for describing the surface. There are many different roughness parameters in use, but R a is by far the most common. Other common parameters include R z, R q, and R s. Some parameters are used only in certain industries or within certain countries. For example, the R family of parameters is used mainly for cylinder bore linings, and the motif parameters are used primarily within France. Since these parameters reduce all of the information in a profile to a single number, great care must be taen in applying and interpreting them. Small changes in how the raw profile data is filtered, how the mean line is calculated, and the physics of the measurement can greatly affect the calculated parameter. Amplitude Parameters. Amplitude parameters characterize the surface based on the vertical deviations of the roughness profile from the mean line. Many of them are closely related to the parameters found in statistics for characterizing population samples. For example, Ra is the arithmetic average of the absolute values and Rt is the range of the collected roughness data points.

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16 Tests and Results. Measure the surface roughness after each grinding step.. Record these readings in Table. Table. Roughness measurement of normalized steel Measurement Number 3 Mean Value After 400 grit grinding After 800 grit grinding After polishing Discussion. What is purpose the surface roughness measurement?. What are the different methods to measure the roughness of a surface? 4

17 METALLOGRAPY Objectives. To learn and to gain experience in the preparation of metallographic specimens.. To examine and analyze the microstructures of metals and metallic alloys..introduction Microscopical Examination The microstructural study of a material can provide information regarding the morphology and distribution of constituent phases as well as the nature and pattern of certain crystal imperfections. Optical metallography is a basic tool of material scientists, since the equipment is relatively inexpensive and the images can be obtained and interpreted easily. Distribution and morphology of the phases can be studied and, if their properties are nown, a quantitative analysis of the micrographs provides some information about the bul properties of the specimen. A limited study of line and surface informations is also possible with the optical microscope. In order to obtain reproducible results, with good contrast in the image, the specimen surface is polished and subsequently etched with appropriate reagents before microscopic examination. In a polished specimen, the etching not only delineates grain boundaries, but also allows the different phases to be distinguished by differences in brightness, shape, and color of the grain. Differences in contrast may result from differences in light absorption characteristics of the phases. Etching results in preferential attac or preferential colouring of the surface. The preferential attac is electrochemical corrosion; it is well nown that different materials corrode at different rates. Grain boundaries are often anodic to the bul metal in the interior of the grain and so are etched away preferentially and delineated. Staining is produced by the deposition of solid etch product on the specimen surface. This is formed by chemical reaction between the etchant and the specimen. Under favorable conditions the use of a proper etchant enables the identification of constituents. Failure analysis depends a great deal on metallographic examination. Microstructural examination can provide quantitative information about the following parameters: ) The grain size of specimens ) The amount of interfacial area per unit volume 3) The dimensions of constituent phases 4) The amount and distribution of phases. Magnifications up to 000x can be obtained with a resolution of µ. For grain size measurements, the grains along a line, circle, or within a nown area are counted. It would be useful to obtain an

18 average value of grain diameter from a microstructural section. In linear intercept method, the grains intercepted by a theoretical line on the specimen surface are counted (Fig. ). The number of grain boundaries intersected per unit length of a test line (nl) can be noted. The average grain size; NL=Ni/(L/M) NL: mean number of interceptions per unit length, Ni: the number of interceptions counted on the field, L: the length of the test line(s) used in mm, M = the magnification. Fig. Linear intercept method for grain size determination Specimen preparation for Microscopical Examination Grinding A small piece of specimen is cut by a metal cutting saw. After cutting operation, burrs on the edges of the specimen should be carefully removed by a fine file or coarse grinding paper. The silicon carbide grinding papers are held flat in a unit containing water facility for lubrication purpose. Each unit contains four grades of papers, starting with grade 400 (coarse) and finishing with grade 00 (fine). Grinding of the wor piece is done by starting with the coarse papers and then continuing with the fine papers. In each stage, grinding is done by rubbing the specimen bacwards and forwards on the grinding paper in one direction only, until the surface is completely ground, that is, until only grinding mars due to this particular paper can be seen to cover the whole surface. The specimen is washed thoroughly to remove coarse silicon carbide particles before proceeding to a finer paper. The direction of grinding is changed from paper to paper, so that the removalof previous grinding mars is easily observed. The extra time spent on each paper should be increased as the finer papers are used. At the end of the grinding sequence, the specimen is washed thoroughly and dried. Now, the specimen is ready for polishing.

19 Polishing The polishing is done on rotating wheels covered by a special cloth. Alumina is employed as polishing agent. The micron size is commonly used, but the total polishing time shortened by starting on the 7 or 3 micron grade. The pad should be ept well supplied with lubricant. The specimen should be held firmly in contact with the polishing wheel, but excessive pressure should be avoided. During polishing the specimen should be rotated or moved around the wheel so as to give an even polish. The specimen should be thoroughly cleaned and dried between each wheel. Etching Before etching, it is essential to ensure that the polished surface is grease and smear free. If the final polishing has involved the use of magnesia ( in the form of an aqueous paste of fine magnesia) or alumina (in the form of an aqueous suspension of fine alumina), then thorough washing followed by drying off with acetone or alcohol will give a suitable surface, although it must not be fingered afterwards. Etching is generally done by swabbing. Etching times will vary from specimen to specimen, however, a good general, procedure is to observe the surface during etching, and to remove the specimen when evidence of the grains first appears. Microscopical examination will then reveal whether the degree of etching is sufficient. Further etching can then follow to strengthen up the details as required. After each etching, the specimen should be thoroughly washed in running water, followed by drying off with acetone or alcohol..tests and Results. Put microstructure photos with correct magnification bar.. Explain the specimen typical microstructure. 3. Calculate the average grain diameter of the micrograph, using linear intercept method. 3.Discussion. Why must metallographic samples be washed and carefully dried before proceeding from one grinding or polishing operation to the next?. What is the purpose of etching metallographic samples? 3. Why are metallographic samples sometimes mounted in plastic? 4. What is the difference between a Eutectoid steel and a Hypoeutectoid steel? 5. At room temperature : What are the phases of a eutectoid steel? What are the constituents of a eutectoid steel? What are the phases of a hypoeutectoid steel? What are the constituents of a hypoeutectoid steel? 6. Briefly explain the effect of grain size on the strength of a metal. 4. What is Grain Size and Grain Number? Relation between ASTM Grain Size and Grain number? 7. How to reduce the grain size? 8. Why with decreasing grain size there is decrease in impact transition temperature? Please explain it by using Hall Petch equation. 3

20 JOMINY HARDENABILITY TEST Objectives. Introduce students to the concepts of hardenability. Demonstrate hardenability in a steel 3. Display the effects on microstructure of the hardening process 4. Provide instruction for a full lab experiment on hardenability (if equipment is available).introduction The hardenability of a steel is defined as that property which determines the depth and distribution of hardness induced by quenching ftom the austenitic condition. The dependence of hardness upon quenching rate can be understood ftom the time temperature transformation characteristics of steel, and, for a particular steel, can be estimated from the T T T diagram. A part may be hardened by quenching into water, oil, or other suitable medium. The surface of the part is cooled rapidly, resulting in high hardness, whereas the interior cools more slowly and is not hardened. Because of the nature of the T T T diagram, the hardness does not vary linearly from the outside to the center. Hardenability refers to capacity of hardening (depth) rather than to maximum attainable hardness. The hardenability of a steel depends on () the composition of the steel, () the austenitic grain size, and (3) the structure of the steel before quenching. In general,hardenability increases with carbon content and with alloy content. The most important factor influencing the maximum hardness that can be obtained is mass of the metal being quenched. In a small section, the heat is extracted quicly, thus exceeding the critical cooling rate of the specific steel and this part would thus be completely martensitic. The critical cooling rate is that rate of cooling which must be exceeded to prevent formation of nonmartensite products. As section size increases, it becomes increasingly difficult to extract the heat fast enough to exceed the critical cooling rate and thus avoid formation of nonmartensitic products. Hardenability of all steels is directly related to critical cooling rates. Procedure Sample of medium carbon steel machined to the shape shown in Fig.. It is a cylindirical bar with a 5 mm. diameter and 00 mm. length. The specimen is placed in the furnace at C for about /

21 hour. The water flow rate is adjusted so that the water column is approximately the distance 50 mm above the end of the pipe, when water is flowing freely. After the sample has been austenitized, it is removed from the furnace and placed directly into the quenching apparatus. A jet of water is quicly splashed at one end of the specimen. After the entire sample has cooled to room temperature, the scale oxidation is removed; two opposite and flat parallel surfaces are ground along the length of the bar. Rocwell C hardness measurements are then made every mm and these readings are recorded. Results Plot a hardenability curve of Rocwell hardness vs. distance from the quenched end.

22 .Tests and Results. Evaluate the hardenability of the steel used in this experiment using the plotted hardenability curve. 3.Discussion. How is the role of carbon and various alloy elements on the hardenability of steels (Give examples of different hardenability curves ).. Why is hardness important? When is hardness important? 3. What is hardenability? Where is it used in industry? 4. Do all steels have the same hardenability? Why or Why not? 5. How does the hardness change as a function of distance from the quenched end? 6. How does grain size relate to hardness? What would a graph of grain size as a function of distance loo lie? 7. Does the hardness of the martensite phase change with steel composition, or is the hardness value a constant? References. Shacelford, IF, Introduction to Materials Science. Smith, W.F., Principles of Materials Science and Engineering 3. ASM, Heat Treater's Guide S 3

23 DENEY : DENGESİZLİK. DENEYİN AMACI Mainalardai dengesizliğin, titreşim spetrum grafiğinde mil dönme hızında tepe oluşturacağını gösterme..teorik BİLGİ Mainalarda dönen elemanlar tarafından oluşturulan tüm uvvetlerin denge halinde oluşuna denge (balans) denir. Bu denge halindei herhangi bir değişme balanssızlığı oluşturur. Dengesizli mainalarda görülen en yaygın titreşim şelidir. Teori olara, müemmel dengelenmiş bir mainada hiç titreşim oluşmaz. Pratite müemmel olara dengelenmiş maina yotur. Tüm mainalar az seviyede de olsa dengesizdirler. Bu dengesizli spetrum grafiğinde mil dönme hızında (x) bir tepe oluşturur. Stati Dengesizli Spetrum grafiğinde basın olan x titreşim freansını oluşturur. Yalnızca bir nota dengesiz olduğu için, rotorun her dönüşünde yalnızca bir işaret oluşur. Yataların fazı aynıdır. Genellile radyal doğrultuda x in genliği daha büyütür. Stati dengesizli için verilece en basit örne şeil. de gösterilmiştir. İi tarafından mafsallanmış ve ütlesi ihmal edilebilen bir milin tam ortasına yerleştirilmiş ince bir dis düşünelim. Şeil. Stati Dengesizli Dis ütlesinin M (g) olduğunu ve dönme esenine göre tam bir dönel simetriye sahip olduğunu abul edelim. İmalat hataları veya disin ütlesinin homojen yayılı olmaması gibi nedenlerle dönme eseninden e adar saptığını abul edelim. e büyülüğüne esantrisite de denir. C g ağırlı merezinin

24 Ağırlı merezinin dönme eseniyle çaışmaması sonucu disimiz ( rad / s) li hızla dönüyorsa oluşaca atalet uvveti F Me (N) () ile ifade edilecetir. Bu durumda dis her döndürüldüğünde C g ütle merezi şeil. de görüldüğü gibi düşey doğrultu üzerinde ve dönme esenin altında duracatır. O halde dönme eseninden r (mm) adar uzalığa bir m (g) elediğimizi düşünelim. Eğer bu yerleştirdiğimiz m ütlesini denlem. de i gibi seçerse dis dengelenmiş olacatır. F mr () İlave edilen dengeleme ütlesi disin ağırlı merezi ile dönme eseninin çaışmasını temin etmiştir. Görüldüğü gibi problem esas itibariyle stati bir problemdir ve bu nedenle bu tip dengesizli problemine stati dengesizli denir. Diste var olan dengesizli u (gmm) olara tanımlanmıştır. Dengeleme büyülüğü olara tarif edilen bu büyülü denlem 3. e eşittir. u mr (3) Denlem ve 3 orta çözülür ise esantrisite yani birim dengeleme büyülüğü ortaya çıar. mr e ( gmm / g) (4) M Birim dengeleme büyülüğü, birim ütledei dengesizliği gösterir. e büyülüğü Tür Standartlarında özgül balanssızlı olara geçmetedir. Dengesizli, daha öncede belirtildiği gibi şeil. de görüldüğü üzere spetrum grafiğinde mil dönme hızında (x) bir tepe oluşturur. Şeil. Dengesizli spetrum grafiği

25 3. DENEY MALZEMESI ve TECHİZATLAR Titreşim Deney Seti İvme ölçer eipmanına sahip titreşim test cihazı 4. DENEYİN YAPILIŞI İvme ölçer diatli bir şeilde titreşim test cihazına bağlandıtan sonra altındai mınatıs yardımı ile deney setinin yata ısmına tespit edilir. Titreşim test cihazı açılır ve menüden spetrum/cepstrum seçeneği seçilir. Start a basıldıtan bir süre sonra test cihazı titreştiği freansları grafisel olara gösterir. Spetrum grafiğinde mil dönme devri ve harmonileri görülmesi belenir. 5.DEĞERLENDIRME Elde edilen spetrumda teoridei belirtildiği gibi mil dönme devrinde ve harmonilerinde pi görülmüştür. 6. RAPORDA BULUNMASI GEREKEN BİLGİLER Deney sonrası hazırlanaca raporda, genel açılamaların dışında şu bilgiler bulunmalıdır : FFT analizi haında genel bilgi Test cihazı haında genel bilgi İvmemetreler haında bilgi Elde edilen spetrum haında yorumlar 7.DENEYLE İLGİLİ YARARLANILABİLECEK KAYNAKLAR Pro-Plan, Titreşim Ölçümüne Dayalı Maina Baımı, Eğitim Semineri Notları, İstanbul, 004

26 DENEY : DİNAMİK TİTREŞİM YUTUCUSU. DENEYİN AMACI Rezonans freansında titreşen bir sistemin titreşimlerini yine o sisteme bağlı bir ütle-yay sistemine atarma ve böylece ana ütlenin titreşimini önleme..teorik BİLGİ Bu deney, uçlarında birer ütle olan ii ince saç levhadan oluşan parçanın irişin orta ısmına bağlanmasıyla gerçeleştirilmetedir. Zorlanmış titreşimlerin tahri freansı ile ucuna ütle bağlı anastre iriş olara modellenebilen ince saç levhaların doğal freansı çaıştığında irişin titreşmeyip saç levhaların titreştiği gözlemlenecetir. İşin teorisini anlama için şeil dei basit ütle-yay sistemini ele alalım. Bu sistem ii serbestli derecelidir. Şeil Sistemin hareet denlemi çıarılırsa diferansiyel denlemlerden birinin homojen olmadığı görülecetir. Bu durumda matris formunda aşağıdai çözüm önerilebilir: x x x x hom ojen x x özel () Sistemde ufa bir sönüm olduğunda homojen ısma ait çözüm zamanla yo olacağından özel çözüm bizim için daha rititir. Bu durumda deplasmanlar için aşağıdai çözümler önerilebilir: x (t) X Sin( t) () x (t) X Sin( t) (3) Burada X ve X sabitlerinin bulunması gerelidir. Bunun için çözümler hareet denlemlerinde yerine onursa aşağıdai ii bilinmeyenli ii denlem elde edilir:

27 0 F X X m m (4) Bu sistem ramer uralı veya bilinen matris aideleri ile çözülebilir. Sonuç: m m m 0 F X (5) m m 0 F m X (6) Titreşimleri yutma için gere ve yeter şart, ana ütlenin deplasmanının sıfır olmasıdır. O halde bu ütleye ait genli sıfıra eşitlenmelidir: Bu durumda aşağıdai ifadeler elde edilir.; 0 m F X (7) m (8) Deney setindei yapra yay olara düşünülebilece saç levhanın rijitli atsayısını hesaplama gerelidir. Bu saç levha, anastre-serbest sınır şartlarına sahip bir iriştir. Böyle bir irişin yay sabiti: 3 L 3E I Burada, E: yay malzemesinin elastisite modülü, I : yayın (levhanın) alan atalet momenti, L= uvvetin uygulandığı notanın anastre mesnete uzalığı, m : yayın (levhanın) ucundai onsantre ütle zorlama freansı deney setinde irişi titreştirme amacıyla ullanılan miline açı ütle bağlanmış eletri motorunun rad/san. cinsinden devridir. Titreşimleri yutma için (8) eşitliğinin sağlanması yeterlidir. 3. DENEY MALZEMESI ve TECHİZATLAR Titreşim Deney Seti Kumpas, alyan, anahtar 4. DENEYİN YAPILIŞI Deney setindei saç levhanın boyutları umpas yardımı ile ölçülür. Eletri motoru irişin üstünde herhangi bir notada onumlandırılır. Eletri motorunun titreşim yaratabilmesi için ucuna açı ütleye sahip bir dis tespit edilmiştir.

28 Daha sonra motor çalıştırılır. Deney setindei ayar düğmesi yardımı ile motorun devri yavaş yavaş arttırılır. Kiriş titreşim hareeti yapmaya başlar. Genlilerin büyüdüğü bölge gözlemle tespit edilir. Motor, devir ayarı ile oynanmadan stop butonuna basılara durdurulur. Deney setindei ütle mitarı değiştirilemediği için (8) eşitliğinin sağlanması amacıyla gereli L uzalığı hesaplanır. Kumpas bu uzalığa ayarlanara ütleler uygun şeilde onumlandırılır. Start butonuna basılara motorun yeniden aynı devre gelmesi sağlanır. Böylece deney setindei irişin titreşmeyip sadece saç levhaların titreştiği gözlenir. 5.DEĞERLENDIRME Teoride bilinenleri uygulayara ana ütlenin (deney setindei iriş) hiçbir şeilde hareet etmeyip sadece yutucu ütlenin titreştiğinin gözlemlenmesi böylece teorinin doğru olduğunun ispatı. 6. RAPORDA BULUNMASI GEREKEN BİLGİLER Deney sonrası hazırlanaca raporda, genel açılamaların dışında şu bilgiler bulunmalıdır : Deneyde ullanılan teçhizatlar haında ısa tanıtıcı bilgi Deneyde bulunan sonuçlar Şeil de gösterilen ii serbestli dereceli ütle-yay sisteminin hareet denlemi 7.DENEYLE İLGİLİ YARARLANILABİLECEK KAYNAKLAR

29 DENEY 3: İNCE NARİN KİRİŞ TİTREŞİMLERİ. DENEYİN AMACI İnce narin iriş titreşimlerinde. mod freansının (temel doğal freans) deneysel olara ölçülmesi ve sonucun yalaşı metot ullanılara hesaplanan teori değerle arşılaştırılması.teorik BİLGİ İnce narin çubular titreştirici ile zorlandırılmıştır. Titreşimi etileme için Lazer Vibrometre ve pulse analiz sistemi ile düzlem içi titreşimler temas edilmeden ölçülere sistemin freans tepi grafileri elde edilmiştir. Şeil. Deney Düzeneği Anastre-serbest sınır şarlarına sahip iriş için doğal freans denlemini elde etti; ( l) n n EI Ml 4 ( ) l n =3,560 β ifadesi ω ile ilişilidir. Buradai β ifadesi öz değerdir. E, Elastili Modülü (Pa) I, alan atalet momenti (m 4 ) M, Birim uzunluğa düşen ütle ( g m ) l, çubuğun boyunu (m) temsil eder. Sistemin düzgün rejim genlilerinin bulunabilmesi için Şeil de gösterilen deney düzeneği hazırlanmıştır. Çubuğun elastili modülünü bulabilme için çeme testi yapılmış, gerilme-şeil değiştirme grafiğinden elastili modülü yalaşı olara hesaplanmıştır.

30 3. DENEY MALZEMESI ve TECHİZATLAR Lazer Vibrometre Titreştirici (sarsıcı ve genli ölçer) Pulse Analizör Parla Bant 4. DENEYİN YAPILIŞI Deney setine ebatları umpasla ölçülmüş olan iriş monte edilir. Kiriş üzerine lazer vibrometrenin netliğini sağlama amaçlı parla bant yapıştırılır. Titreştirici üzerinden genli ve freans ayarları yapılara iriş titreştirilir ve rezonans durumundai deplasmanı bulunur. 5.DEĞERLENDIRME Test cihazı ile ölçülen değerle teori olara bulunan değer arasındai far hesaplanır. Yalaşı metodun doğruluğu tespit edilir. 6. RAPORDA BULUNMASI GEREKEN BİLGİLER Deney sonrası hazırlanaca raporda, genel açılamaların dışında şu bilgiler bulunmalıdır : Kirişin enine titreşimlerini modelleyen denlemin çözümü Test edilen malzemenin alan atalet momenti ve doğal freansı Deneyde ullanılan teçhizatlar haında ısa tanıtıcı bilgi Elde edilen spetrum grafiğinin yorumlanması Ölçülen değerlerle teori değerler arasındai sapma, sonuç haında yorum 7.DENEYLE İLGİLİ YARARLANILABİLECEK KAYNAKLAR Analiti Metotlarla Titreşimlerin Etüdü Doç. Dr. Metin Gürgöze İstanbul Teni