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Title:	Fatigue crack growth behaviour for additive manufacturing ALS110MG material using s-version finite element method
Authors:	Mohd Shamil Shaari (P80296)
Supervisor:	Ahmad Kamal Ariffin Mohd Ihsan, Prof. Ir. Dr.
Keywords:	Three-dimensional printing Aluminum alloys -- Fatigue Finite element method Universiti Kebangsaan Malaysia -- Dissertations Disertations Academic -- Malaysia
Issue Date:	23-Jul-2018
Description:	Additive manufacturing (AM) is considered the current research interest among researchers nowadays because it is beneficial for aerospace, automotive and medical sectors. AM is introduced, concentrating on producing prototype products using polymers. The polymer is replaced with metals such as aluminium alloy to accommodate the needs from manufacturing industries. Direct metal laser sintering (DMLS) is one of the existing methods to manufacture metal products using AM. Still, due to limitation of scientific information to determine the credibility of AM materials, further studies are needed to support this manufacturing technology. One of the most critical investigations is the fatigue crack analysis to determine the structural integrity and reliability for all types of engineering materials. This is to overcome the catastrophic failures of engineering structures that are caused by fatigue crack growth. In this present study, the surface crack growth behaviour is predicted using the sversion finite element method (S-version FEM) for AM material. The AlSi10Mg material is selected since this aluminium alloy is commonly applied for making parts in the automotive and aerospace manufacturing industries. Therefore, the metallography, material characteristics and fatigue crack propagation are among the necessary investigations that are performed prior to the fatigue crack growth prediction. First is to establish the material properties as input parameters for the numerical analysis (S-version FEM). Second is to accommodate the credibility of DMLS using aluminium alloy. Therefore, the effect of heat treatment is observed and analysed for the metallography, material characteristics and fatigue life behaviour between as-built and heat-treated to T6 condition. All the specimens for the microstructural analysis and mechanical testing are produced by DMLS using AlSi10Mg material. From the tensile testing, the ultimate tensile strength (UTS) for the as-built specimen is recorded at 296.9 MPa while compared to heat-treated, it increased to 310.2 MPa. This is because of the spheroidisation phenomenon of the silicon particles during heat treatment to T6 condition. Furthermore, the fatigue crack propagation testing is performed to acquire the material constant for fatigue crack growth following the Paris' Law. From the result, the material constant of is evaluated for 1.85 x 10-9 while the is 3.69. Thus, the fatigue crack growth behaviour predicted using S-version FEM is simulated and compared with analytical solution based on stress intensity factors (SIF). From the SIF comparison, the normalized root mean square errors (NRMSE) are performed to support the validation and shows relatively small errors of 0.0675, 0.0493 and 0.0529 according to aspect ratios ( ) of 0.5, 1.0 and 1.5. In addition, the S-version FEM is compared with experimental findings based on the fatigue crack growth behaviour. The behaviour shows good agreement between both methods with small error calculated using NRMSE of 0.0432. Extended investigation on fatigue crack growth prediction using S-version FEM is performed for embedded crack inside a structure. Subsequently, SIF behaviour is compared with analytical solution with 0.216, 0.138 and 0.31 produced by NRMSE according to of 0.5, 1.0 and 2.0.,Ph.D.
Pages:	130
Call Number:	TS171.95.M84485 2018 3 tesis
Publisher:	UKM, Bangi
Appears in Collections:	Faculty of Engineering and Built Environment / Fakulti Kejuruteraan dan Alam Bina

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