Bearing capacity of the bonded metal joints in the conditions of Indonesia, North Sumatra province

Transcription

1 EngOpt International Conference on Engineering Optimization Rio de Janeiro, Brazil, June 008. Bearing capacity of the bonded metal joints in the conditions of Indonesia, North Sumatra province David Herak 1, Miroslav Muller, Jindrich Karansky 3, Oldrich Dajbych 1 Department of mechanical engineering 1, department of material science and manufacturing technology, department of technological equipment of buildings 3 Faculty of engineering Czech University of Life Sciences Prague Czech Republic, herak@tf.czu.cz, muller@tf.czu.cz, karansky@tf.czu.cz, dajbych@tf.czu.cz Abstract: An article is focused on the analysis of bonded metal joints capacity in the conditions of equatorial Indonesia North Sumatra province. For a purpose of given article a province was divided into the three main climatic zones: Medan, Balige, Pagarbatu, where the dependency of bonded joints capacity on the time of weather exposure was observed. By the analyses of measured values were predicted joints life and their further usability. Keywords: Capacity, joints, life - durability, usability, tropical area 1. Introduction The development of bonded joints is obvious in all possible industrial branches at present times. Bonding is becoming more important joint technique of classical and perspective materials. Development of new adhesives brings new opportunities of the bonding technologies applications. In many cases is bonding only suitable technology, fulfilling the demands of final joint quality. Bonded joint is a complicated and combined system, which quality is influenced by many factors, reacting during the materials and glues preparation, by the joint assembly and glue setting, by the usage of joint. A large part of industrial production is currently being transferred to the development countries and areas. These countries have quite different geographical, climatic and technological conditions, than are found in the countries where such production import is aimed. In the equatorial countries is increasing usage of bonded joints, mainly in the automobile and naval industry, as well as during the agricultural machines and tools production and last but not least by the production of daily use devices. By the climatic influences and different geographical conditions joint s and materials capacity decreasing appear. Corrosion susceptibility and the decreasing of parts or machines life might be different up to 50% [1]. Bonded joints reach maximal strength after a certain period, dependent on the setting speed, thus by the solidification reactions of the glue. The way and process of the glue solidification is different for each kind of used technique, material or glue. The glue solidification process is influenced by the surrounding temperature in most cases. Glue solidification process of the joint might be simply described as a glue change from the liquid to the solid state, by the concurrent adhesive and cohesive bonds formations. The development of such process is different by the usage of different glues and is influenced by various factors. These might be divided as technological factors and factors by the influences of the bonded joint s surroundings. First group of the factors mentioned above is represented by the fabricating of the glue, amount of the glue used by bonding, connected materials influence. Second group of the influencing factors is represented by the temperature, moisture and other physical properties. However, all of the factors mentioned above act together and mutually influence each other. Their importance and impact depend mostly on the kind of glue used and kind of solidification reaction []. Knowledge of technological properties influencing the bonded joint is important for the successful usage of chosen glues. During the selection of the glue application is also very important to accent the surrounding conditions and long term degrading processes appearing in the joint. Degrading processes significantly influent mechanical properties during the bonded joint s life. Reached strength limits of the bonded joint at the beginning of life span could be decreased by the time [3].. Methods A knowledge obtained during the previous experiments was applied by the preparation of the bonded joints, exposed to the degrading processes. Bonded joints were prepared by optimal values of surface modification, as well as the thickness of the bonded layer. Mentioned parameters significantly influence strength qualities of the bonded joints. During the experiment was tested two component glue Bison epoxy metal, which has provided satisfactory and relatively high values of the strength during previous experiments. Experimental testing is done in concordance with the Czech standard of CSN EN 1465 (Determining of the duct shear strength of the solid adherents at the flashing joints). The matter of the testing was the determination strength of the simple flashing bonded joint, stressed by the tensile force acting parallel with the surface of conglutination and tested sample main axis, till the deformation of the sample. Table 1. Chemical composition of the bonded material (weight %) Element C Mn Cr Ni Al Cu Nb Ti Fe steel

2 The adjustment of the bonded surface of material with chemical composition mentioned in the Table 1. was realized by the blasting of AL O 3. Size of the blasting particles was F4 and thickness of the bonded layer 0,1 mm. In a case of resins is recommended thickness of the bonded layer between 0,1 and 0, mm. A mixture of the resin and the hardener was prepared by the specified ratio (1:1). Mixture of the glue was applied on the sample s surface at prescribed period, distant wires were applied and other part of bonded joint placed and parts fixed together. Both parts of the bonded joints were fixed by the lead of weight of 70 g. Tested samples of sizes 100 x 5 x 1,5 mm are bonded together, while the recommended length of the overlapped parts is 1,5 mm. In order to found out influences of the degrading processes to the bonded joints was prepared basic set of the samples, solidified at laboratory temperature of 3 ± C in the climatic conditions of Czech Republic. Samples were then transported to Indonesia by air. Measurements were done in Indonesia, North Sumatra region, characterized by the tropical weather throughout the whole year, with minimal changes. Virtually there does not exist fall or winter season. There, the year is divided into the wet and dry period. Dry season is brought from June to the September; rain falls are brought by Eastern monsoons from December to March. In a transition period are beautiful sunny days changed by the days with occasional rains. Even in the middle of wet period temperatures often reach 1 33 C. Exceptional are mountains location with high elevation where the temperatures are frequently lower. Highest number of the rain falls is usually recorded from the December to the January. Average value of the air humidity is fluctuating from % [5]. Figure 1. Main locations of the experiments, pictured on the map of North Sumatra Although Indonesia belongs to the equatorial countries, climatic conditions are not the same throughout the country. Elevation is from the sea level regions to the mountain regions at 3000 m above the sea level. In a different elevation levels are various rain falls, temperatures and humidity. Accordingly to the Fig. 1, Indonesian province of North Sumatra might be divided into three basic climatic parts: 1. Medan- typically tropical area on the shore of Chinese Sea, with the elevation nearly 0 m above the sea level, average daily temperature about 31 C, humidity around 90%. Rain water ratio is 00 mm per year [7].. Balige this location is found in the area 900 above the sea level, close to the Lake Toba, with daily average temperatures around 5 C, humidity app. 80%. Rain water ratio is 1800 mm per year [6]. 3. Pagarbatu such location is located on a mountain plateau 1350 m above the sea level, with daily average temperatures around 5 C, humidity app. 90%. Rain water ratio is 400 mm per year [4]. Each set of the tested samples were exposed to weathering by surrounding environment for a certain period (, 4, 6, 8 months) in each location. Then the change of strength were observed for every of tested samples series. Samples were not loaded by burden except by its own weight, were merely exposed to the surroundings. In so called zero time samples strengths were determined, in the laboratory conditions in Czech Republic. Samples tested in Indonesia were collected in each location in certain time period (mentioned above) and then sent to Czech Republic by air, where their shear stress capacities were laboratory determined. Totally 160 samples were used, by the each collection were 10 samples collected, it means 4x10 samples per one collection in all of the mentioned locations at one time. 3. Measurements Measured values were processed into the following Table. If these values are pictured in a column chart Fig.. is obtained clearly visible dependency of the bonded joint strength capacity on the exposure time and elevation.

3 Time (month) Table. Measured values of the bonded joints strength capacity Location- area Medan Balige Pagarbatu Strength capacity (N) months 4 months 6 months 8 months Strength Capacity (N) Medan 900 Balige 1350 Elevation above see level (m) Pagarbatu Figure. Dependency of the bonded joints strength capacity on the elevation and exposure time Measured values might be expressed by the point chart (Fig.3) as a dependency of strength on the exposure time and observed location area Balige 6000 Pagarbatu Strength Capacity (N) Medan Time (month) Figure 3. Dependency of the bonded joint on the exposure time

4 If these measured dependencies are smooth by the polynomial function, mathematical equations, describing dependencies of joint capacity on the exposure time, are obtained. Where C B is capacity at Balige area (N) and t is time of the exposure (month). CB = 7,8869 t 14,31 t ,9 (1) RB = 0,9978 () Where C P is capacity at Pagarbatu area (N) and t is time of the exposure (month). 3 CP = 4, 7188 t + 49,455 t 463,64 t ,9 (3) RP = 0,9887 (4) Where C M is capacity at Medan area (N) and t is time of the exposure (month). 3 CM = 13,04 t + 0,5 t 113,3 t ,4 (5) RM = 0,9901 (6) 4. Discussion Decreasing of the strength capacity is obvious from the measured values, leading to the decreasing of joints life in the dependency of time exposure. By the equations Eq.(1), Eq.(), Eq.(3) of dependencies pictured above is possible to predict qualities of each joint in longer time line. Calculated values of the strength capacities dependent on time exposure are presented in the Table 3. Table 3. Supposed strength capacity of the bonded joints Time (month) Area 5 10 Strength capacity (N) (%) (N) (%) (N) (%) Balige % % % Pagarbatu % % % Medan % % % Figure 4. Supposed strength capacity of the bonded joints There are also pictured percentual values of the strength capacity decreasing toward zero time conditions. By the measurements is obvious fact, that the samples in Balige area are characterized by low value of strength capacity decrease. By the equation Eq.(1) could by set presumptive time when the rapid decrease of the bonded joint appears. Such time is actually life span of the bonded joint and is 9 months for Balige area. In the area of Pagarbatu rapid strength capacity loss appeared already after two months of exposure

5 time. If the life span of bonded joint is set for Pagarbatu area, by the equation Eq.(3), is found out that the life span of joints there is merely 1 months. Bonded joint in Medan area has shown most rapid loss of the strength capacity, when 5% decrease of strength capacity appeared within first two months. By the equation Eq.(5), life span of such joint is only 11 months for this location. During real constructional practice is also important to set a belt of strength capacity. Constructor may calculate 15% variance of the tabled values during the bonded joint proposing and calculating. If the equations of supposed strength capacity of each joints Eq.(1), Eq.(), Eq.(3), together with the belt of applicability (Fig.4). In presented case by the application of 15% from the so called zero capacity is found out real time of the usability of the bonded joints in chosen areas. By the graphical expression is obvious that possibility of the real usage of the bonded joint is merely 0,93 months in Medan,,64 months in Pagarbatu and 10,5 months in Balige. 5. Conclusion By the experimental setting of metal bonded joint in the three climatic locations in Indonesia North Sumatra province might be stated following: 1. Usage of the bonded joints, which are bonded and solidified in Czech Republic (area of moderate belt) with the usage of standard glues of European production, is quite inadvisable in all of three described locations of Indonesia, North Sumatra region.. Joints were tested without a stress. By the experiment with usage of loaded samples or samples dynamically strained, are worse results of life span or stress capacity expected. 3. Appearance of the corrosion was observed on the surface of the tested steel samples. Samples in Medan area were covered by the overall layer of the corrosion. Corrosion had the same progress on the whole surface. Corrosion also appeared on the samples placed in Balige and Pagarbatu, however its appearance was not regular but spots with strong or light corrosion were observed. The work on experiment is ongoing. At present time are tested samples bonded and solidified hardened in Indonesia and then placed in mentioned areas. Degree of corrosion rate is also part of the research dependent on the exposure time in each of climatic area. An article was supported by the support of CUA grant Prague IGA 31140/131/ Stanoveni pricin destrukce lepenych spoju. 6. References 1. Faires, V., M.: Design of machine elements, New York, The Macmillan Company 1955, 64. Marghitu, D., B.: Mechanical engineers handbook, Auburn, Auburn University Alabama, Academic press, Auburn 001, Oberk, E., Jone, F., D., Horton, H., L., Ryffel, H., H.: Machinery s Handbook, 6th edition, New York, Industrial press Inc, New York 000, Situmorang, S.: Profile and potency of North Tapanuli Regency, Tarutung, The Regency of North Tapanuli 007, Stone, D., et al.: Biodiversity of Indonesia: Tanah Air, Oxford, Butterworth-Heinemann 1994, Syarbaini, N.: Sumatera Utara in figures 004, Medan, Statistics of Sumatera Utara province 004, Vaisutis, J., et al.: Indonesia, London, Lonely Planet Publications 007, 94