Browsing by Author "Bikila, Debela"

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    Numerical Simulation for High Cycle Fatigue Life Prediction of Pre-tightened Bolts of Connecting Rod: TOYOTA D4D Dolphin Case
    (Addis Ababa University, 2022-03) Bikila, Debela; Samuel, Tesfaye (PhD)
    The connecting rod (Conrod) bolts are integral components of the engine that are used to connect the piston with the crankshaft through the connecting rod. If the conrod bolts pretension reliability is insufficient or excessive, deformation and fatigue failure will occur, resulting in component breakage and engine failure. At local maintenance shops, they are using different replacement materials than the initial material of the new automobile. The use of improper material is also the problem of engine failure. The focus of this thesis is to estimate the fatigue life of TOYOTA D4D Dolphin connecting rod bolts at high cycle using Finite Element Modeling with the help of software—ANSYS 2020 R 2 and MATLAB tools. The high cycle fatigue life was analyzed at different pretension forces to examine the effect of bolt pretensions and determine the appropriate bolt pretension value. The prediction of high cycle fatigue life was estimated using the Stress-Life approach. Additionally, the total deformation at insufficient and excessive bolt pretension was analyzed. Then the proper bolt pretension has been selected based on the analysis. Again, the existing in-use material for conrod bolts was compared with those the materials used by local automotive maintenance shops as a replacement. Their safety factor was identified to suggest which material is suitable for connecting rod bolts. The study results from the numerical simulation show that the value of bolt pretension has a more significant effect on the fatigue life and total deformation of connecting rod bolts, especially at higher cycles. When bolt pretension changed from 22KN to 30KN, the number of cycles of the materials reduced. The Insufficient values (<22KN)(i.e., 20KN to 0KN) of bolt pretension were applied to the model, and the total deformation increased from 0.16494mm to 0.26291mm, respectively. Again, the excessive values (>22KN) (i.e., 23KN to 50KN) of bolt pretension were applied to the model, and the total deformation increased from 0.16451mm to 0.21111mm, respectively. At the value of 22KN bolt pretension, the total deformation showed the lowest number (0.16449mm), which is the appropriate point to apply the clamping torque. In addition, the applied 22KN to 30KN pretension loads on the existing material (ARP2000), ARP625+, and ARP3.5 resulted in the fatigue life of 498.93*10 6 to 489.13*10 6 , 409.71*10 6 to 399.4*10 6, and 407.59*10 6 to 397.29*10 , respectively. For checking the safety factor of the materials, ARP2000 has a good safety factor. The ARP2000 has a greater number of life cycles than the replacement materials. To avoid early failure, therefore, tightening of the bolt needs to be controlled, and a replacement materials selection requires scientific methods of selection.