Azmi Abdul Wahab

Contact Pressure Evaluation of a Gear Pair along the Line of Action Using Finite Element Analysis

In loaded gears, contact behavior along the line of action changes tremendously. This leads to variation in gear contact conditions along the tooth flank, which may cause the failures such as surface wear, scuffing and pitting at different positions on the tooth surface. Hence, the information on the instant contact behavior along the line of action is crucial. However its evaluation for real gear conditions is very complicated. In this paper, the contact pressure for a pair of mating spur gears has been determined by Finite Element Analysis (FEA) using ANSYS software. The contact pressure results are then verified by twin-disc experimental results and the Hertzian contact pressure equation. The ANSYS results show the similar trend with the twin-disc test results, indicating that the FEA modelling is successful and provides good results.

Estimation of Burst Pressure of Corroded Pipeline Using Finite Element Analysis (FEA)

One major concern in maintaining pipeline structural integrity is failure due to corrosion defects. Various tests and codes had been established to assess the corroded pipelines. Burst test is one of the tests being conducted in the lab to assess the integrity of the pipelines. The advancement in computer technology had made the Finite Element Analysis (FEA) capable to simulate the burst test numerically. The objective of this study is to estimate the burst pressure of a corroded pipeline by using FEA. First, Ultrasonic Testing (UT) scan was carried out to establish the corroded pipe profile. FEA was then conducted to simulate the experimental procedure of the actual burst test. Several models were built and simulated by considering the number of defects, their depth and shape as the varying parameter in each simulation. All models were properly constrained and pressurized internally in determining the burst pressure (pb) of the corroded pipeline. The result obtained by FEA was analyzed and compared to the actual burst test, ASME B31G and DNV-RP-F101 codes. Lastly the best model of FEA was proposed.

Failure Pressure Estimation of Corroded Pipeline with Different Depths of Interacting Defects Subjected to Internal Pressure

Pipelines are one of the most reliable and safest ways to transport oil and gas from one location to another. However, if not handled and maintained properly, they will cause major destruction should one of these pipelines burst. A pipeline which has oil or gas flowing through it will be subjected to internal pressure due to the flow of the oil or gas. Furthermore, the chemical composition of the oil and gas acts as a corrosive agent towards the pipeline. The corrosion eventually becomes defects thus compromising the pipeline integrity. In addition, if two defects are close enough, they are treated as interacting defects. In this work, the pipeline integrity was first calculated using DNV RP-101 codes. After calculating the maximum operating pressure for the pipeline using the codes, Finite Element Analyses using ANSYS were carried out to simulate and model the pipeline with the interacting defects. The maximum operating pressure given by the FEA was then compared to the DNV codes. We found that despite consistency between DNV codes, the FEA analysis showed that geometry plays an important part in determining the values of failure pressure. The FEA analysis showed that by increasing the ratio of depth between the interacting defects, the failure pressure decreases. This was likely because defects of larger depths are more likely to fail at lower pressures. This contradicts the results obtained from DNV codes where the failure pressure is constant for the same effective defect depth over thickness, (d12/t)*.

Development of the Shape Functions for Fatigue Test Using Digital Image Correlation

Mechanical failure of a structure or a machine during the regular working conditions are often related to the fatigue damage. As a consequence, the structural integrity monitoring of a system has always been a laborious task in the field of engineering. Since the strain measurement is one of the most important predictors of fatigue life, a precise strain measurement method is therefore required. There are many strain measurement methods in fatigue analysis; namely strain gauge, brittle coating method, photoelastic-coating and other optical strain measurement methods. However, various advantages and disadvantages have been found in each of the method mentioned above. Hence, there is always a need to develop a precise and yet informative strain measurement method in mechanical testing. The objective of this study is to develop the first-order shape functions for fatigue test using the Digital Image Correlation technique. In this study, sub-pixel accuracy image correlation algorithm was developed by using MATLAB whereby the positions of the points were precisely selected by using the fine-tuned function. As a result, the first-order shape functions were determined by retrieving the information that is stored in the affine transformation matrix. The works presented in this paper were mainly focused on the development of the algorithms, together with the results and the discussions for the validation exercises. In conclusion, a good agreement was achieved and the newly developed algorithm was proven to be accurate.