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İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Anabilim Dalı / Yapı Malzemeleri Bilim Dalı

Ahşap malzemedeki kusurların ultrasonik tomografi ve ultrases deney yöntemiyle irdelenmesi

Examination with ultrasonic tomography and ultrasound experiment method of wooden material failure

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Özet:

Ahşap, gerek canlı ve organik bir malzeme olması, gerekse diğer canlı ve cansız varlıkların etkisinden dolayı bozunma yaşayan bir malzemedir. Yaşadığı bozunmanın etkisiyle yapısında kusurlar meydana gelip bu kusurlar ahşap malzemenin kullanılabilirliği önünde engel oluşturabilmektedir. Bu çalışma kapsamında ahşap malzemedeki kusurların, ahşapta bir kesit kaybı veya kütle azalması yaşatmadan (yani malzemeye tahribat vermeden) tespit edilmesi amaçlanmıştır. Ahşaptaki kusurların tayini için tahribatsız deney yöntemleri olan Ultrasonik Tomografi ve Ultrases kullanılmıştır. Çalışma için öncelikle 36*36*72 cm boyutlarına sahip, 72 cm'lik uzun kenar boyunca 12*12*72 cm boyutlarında delik içeren kare prizma numune oluşturulmuştur. Daha sonra 20*20*20 cm boyutlarına sahip küp numune oluşturulmuştur. Bu iki numune üzerinde deneylerin uygulanması için gerekli işaretlemeler yapılıp deneyler uygulanmıştır. Sonraki aşamada ise 20*20*20 cm boyutlarına sahip küp numunenin üç adet yüzeyine, 0.75 cm çaplı ve 8 cm uzunluktaki matkap ucuna sahip matkapla daha önceden belirlenmiş noktalar tahribat verilerek delikler açılmıştır. Delik açma işleminden sonar ise tahribatlı numune üzerinde gerekli işaretlemeler yapılıp tekrardan Ultrasonik Tomografi ve Ultrases deneyleri uygulanmıştır. Söz konusu iki deney uygulandıktan sonra, Ultrases deneyi için elde edilen süreler ilgili koordinat sistemi oluşturulup tablolar oluşturulduktan sonra tabloda ilgili yerlere yazılmıştır. Daha sonra noktalar arası uzunluklarda belli olduğundan ilgili formül ile hız büyüklüğü tabloların ilgili yerlerine yazılmıştır. Ultrasonik Tomografi deneyi için ise elde edilen B scan, C scan ve D scan görüntüleri numunenin ilgili kesitleriyle birlikte değerlendirme yapılmak üzere şekil olarak oluşturulmuştur. Ultrasonik Tomografi ve Ultrases deney yönteminin ahşap malzemeye tahribat vermeden onun kusurları hakkında bilgi sahibi olmamızı sağlaması, ahşaptaki kesit kaybının oluşmasını engellediği için tahribatlı yöntemlere göre kullanılmasının tercih sebebi olmasına neden olabileceği söylenmektedir. Deney sonuçları değerlendirildiğinde Ultrasonik Tomografi Yöntemi için 36*36*72 boyutlu kare prizma numunede X doğrultusu için düşük mertebede, Y doğrultusu için yüksek mertebede uzunluk değeri elde edilmiş olup 20*20*20 boyutlu küp numunede Y doğrultusu boyutu elde edilememiştir. Elde edilemeyen durumun alt ve üst yansımadan kaynaklı olduğu düşünülmektedir. Ayrıca 20*20*20 boyutlu küp numunenin yapıştırılması esnasında oluşan kusurların da sağlıklı veri elde edilmesini engellediği düşünülmektedir. Ultrases deneyi için ise kusur miktarı arttığında hız değerinin azaldığı tespit edilmiştir. Yapılan her iki deney yönteminden elde edilen gerek görüntülerden gerek ise hız değerlerinden kusurların türü ile ilgili herhangi bir yorum yapılamamıştır. Ahşap yapıların gerek inşaasından kaynaklı gerekse çevresel faktörler ile geçen zamandan kaynaklı olarak yapısından oluşan kusurların Ultrasonik Tomografi ve Ultrases deney yöntemleriyle tespit edilmesi, tadilat ve güçlendirmelerin doğru şekilde yapılması açısından önem arz etmektedir. Bu yüzdendir ki ahşap yapılarda bahsi geçen bu iki deney yönteminin uygulanması tavsiye edilmektedir.

Summary:

Wooden is decomposition material. Because both it is lively, organic material and expose to live and dead factor. Decomposition causes the formation of failure in wooden material. So, this situation effects usage of wooden. Because it prevents usage of it. Failures which form in wood materials cause damage wood. Because of this determination about shape, location, greatness, type of wood materials and depending of these examination of changes about mechanical properties of wood is so important for taking precaution. There are some types of failures about wood. These are spiral fiberness, pith and knot. Although knots have good aesthetic view, they decrease strength of materials depending type, location, dimension, load. Because of this reason knots have negative effect about wood materials. İt is same for piths too. In addition piths causes decrease durability of wood. In this study, it is aimed that determination of wooden material failure without loss of area and mass (without destructive). Ultrasonic Tomography and Ultrasound which are nondestructive experiment methods are used for determination of failure there. Proceq Pundit device was used for Ultrasound Experiment Method. A-1220 Monolith device was used for Ultrasonic Tomography in this study. In Ultrasonic Experiment Method, there is a speciment which is known dimensions. There are two points which is known distance between them. Normally sound wave passes in solid part the fastest and this method utilizes this situation about materials. This method is applied this two points and gets time and results are interpreted dependimg on getting time. (Sound waves are used there) Sound wave goes slower failure part of wood spicement than continued part of it. Because passing time of faliure part is longer than continued part, it can be understood that stress velocity has inverse ratio with time. ( wave does not pass inside of failure. It passes around of failure. Because of this it happens). Information about failures of wood speciment can be taken by utilizing this properties of Ultrasound wave. In this method Proceq Pundit is used. It has two transduser. One of them send sound wave to the wood and the other takes it from wood and time is seen digital display abour device. In addition when the experiment is applied to specimen, ultrasonic gel or gres oil should coat to transdusers to prevent space between specimen and transduser and to form continunity between specimen and transduser. If it does not coat, experiment can not apply. This device apllies three way its experiment. These are direct, semi-direct and indirect methods. In this study, three of ways are applied to get results. In Ultrasonic Tomograhy Method , Waves which have high frequency effect material and results are analyzed in Ultrasonic Tomography Method. In this method, first of all failures determine. Then studies are made about mechanical and phsyical properties of material. After that knowledge is got for getting better of material. Ultrasonic Tomography is used to estimate mostly about production quality of wood material duration processing of it. There are some difficulties about forming of effective Ultrasonic Tomography. These are weakness of ultrasonic energy, having boundary dimension about material and nature of wood. Because high frequency waves decrease even if narrow length, this method more effective wide surface than narrow surface. It is estimated that solve this problem in future. Ultrasonic tomography is made generally about defect and failure on wood material now. But it is estimated that it will make about evaluation structural capacity depending on growing analyze technic in future. In this method A-1220 Monolith device are used. It aims to determine thickness and defect of material by using echo method. Device which has 24 ceramic point probe and half of probe send waves and other takes waves has 6*4 matrix. İmages get with reflection of wave here. when datas which get from device transmit to computer and get images get with Planevisor 4.0 software, interpretation are made about material there. Greatest advantage of this device is working with ''dry contact'' method. Because when the experiment makes, gel is not needed for probes but Proceq Pundit device probes need gel. In addition experiment surface should be clean for A 1220 Monolith device. First of all tetragonal prism specimen which has 36*36*72 cm dimension and contains a blank 12*12*72 cm dimension was produced. After cutting beech, little wooden blocks are compunded which has dimension 36*36*72 cm. When it is produced, A blank is formed which has 12*12*72 cm inside of speciment. Joins are formed by nailing and using carborundum. In addition glue was used on some place. After that cube specimen which has 20*20*20 cm dimension was produced. After cutting beech, little wooden blocks are compunded which has dimension 20*20*20 cm. Joins are formed by using glue and tree stamper. After that 1,2,3,4,5 and 6 numbers are given opposing surface (for example 1 surface is opposite 2 surface ( 3-4, 5-6 are same way)) for preventing confusion. After producing 20*20*20 cm dimension speciment, 3 surface is drilled at 6.5 cm distance from one side with a.7.5 cm diameter and 8 cm depth. It is apllied same way for opposite side. After that it is applied that same way 6.5 cm below of these two bores. In the last step, it is apllied that same way for 4 and 5 surface and destructive cube speciment is formed. Applying ultrasound experiment for 36*36*72 specimen, First of all grid system is formed above surface of speciment. First point is marked on distance which is 5 cm below from long side and 1 cm right from short side. Other points are marked distance at 5 cm right from before point and 15 points are marked in this way. First row is completed in this way too. After that second row which is below 10 cm of first row and third row which is below 20 cm of first row are completed in this way too. In the end indirect experiment method is applied the above surface. When the experiment is applied, first probe stays stable on first point and second probe moves to being put over from before point for first row. After that two probes moves in distance 10 cm. It is applied with same way for second and third row too. (Same thing is made for side surface and apllied semi-direct and direct method but no data gets from this surface) Applying ultrasound experiment for 20*20*20 specimen, First of all grid system is formed above surface of speciment. First point is marked on distance which is 3 cm distace from side. Other points are marked distance at 7 cm right from before point and all points are marked for all row and all surface. The next step direct method is apllied to specimen. Then indirect method is applied to specimen like 36*36*72 specimen. Applying ultrasound experiment for destructive 20*20*20 specimen, everything is same with 20*20*20 speciment. But the cube specimen was drilled in three faces at determinate points by drill which has drilling bit 0.75 cm diameter and 8 cm length. Applying ultrasonic tomography experiment for 36*36*72 specimen, First of all griding are made on plexi plate which has a distance between horizontal axis is 3 cm and vertical axis is 5 cm. After that plexi plate is brought on surface which will apply experiment and grids are generated on surface by squeezing spray on plexi plate. The next step the first probe of device is brought on first grid of speciment and data are taken. In the end device is put over one grid on surface and second reading is realized at first horizontal axis. So all readings are completed in this way. The most important thing there is after 4 probe touch first 4 grid, first probe should touch second grid not fifth grid for horizontal axis. If first probe touch fifth grid, the display is not got. After finishing first horizontal axis, one grid is gone down and reading completed same way for all horizontal axis. After them datas are transimitted to computer to interpret the results. Applying ultrasonic tomography experiment for 20*20*20 specimen, same methods with 36*36*72 specimen are applied to cube specimen but it is made only for 6 surface. In the last step, datas are transimitted to computer to interpret the results. Applying ultrasonic tomography experiment for destructive 20*20*20 specimen, same methods with 20*20*20 specimen are applied to specimen. In the last step, datas are transimitted to computer to interpret the results. After applying two experiments, obtained times with relevant coordinate system were written on the formed tables. After that speed vectors were got and written on tables for Ultrasound experiment. B scan, C scan, D scan and specimen views were formed and put on the relevant pages for evaluating in Ultrasonic Tomography experiment. Ultrasonic tomography and Ultrasound experiments method get know about specimen without destructive and preventing loss of surface. Because of this they can be preffered as experiments method. According to Ultrasonic Tomography experiment results; If the results were compared with real length, the length of X axis has lower level and the length of Y axis has higher level for 36*36*72 cube specimen. The length of Y axis did not get for cube specimen. The reason of it is though because of reflection of waves. In addition formation of defects about duration gluing for cube specimen prevented to get datas. According to Ultrasound, when quantity of defects increased the value of speed decreased. Comments about type of defects did not get from both of experiments. It is important to determine defects with ultrasonic and ultrasound caused by the construction of timber structures due to time lapse depending environment in terms of correcting the modifications and strengthening. It is advisable to apply these two methods which are based on wooden structures. There are lot of historical timber buildings in the world. Because of this utilizing these methods are important.