The research is aimed to 1) study the level and priority of the factors affecting the delay of construction projects and 2) provide suggestions in relation to the prevention of such delay. The sample is 520 people who were working for different construction projects. They were project managers project engineers field engineers and foremen. The data were collected by using online questionnaires and analyzed to find out mean standard deviation (SD) frequency correlation coefficient and confirmatory factor analysis. The findings reveal two significant aspects. First those who were working in the construction projects concerned about the factors affecting the delay of the projects at high level. Respectively the factors related to design resource external factors and others were taken into consideration. The factor regarding to work performance is regarded affecting the project delay at the highest level. Other factors i.e. the design external factors and others and resource have the affects at the lower level. Second the work-related factors can help prevent the project delay. In other words the construction plan and methods as well as the project management should be well-implemented in accordance with the design. The construction site should be on inspection considering its drawing. Regarding the external factors and others the public voices of those living around the construction site should be taken into consideration. Furthermore the effective use of the resources can be carried out by sufficiently preparing all materials tools and equipment for constructing any project effectively as a consequence.

This research is to test the fatigue endurance of the material by using end bending of specimen. The testing material is S45C steel and forming to the standard size for testing. The specimens with a diameter of 8 mm required a different bending moment. It was found that the large bending moment affects the fatigue of the specimen. The specimen quickly damaged due to the high bending stress and there were a small number of load cycles. If the bending moment acting on the specimen was reduced to the bending stress decreased and the number of load cycles increasing. It was shown that the bending stress and the magnitude of the bending moment affected the fatigue of the material. Also the appearance of damage marks of the specimen will have a flaw around the fracture surface. Then the flaw will be enlarged until the specimen will be damaged by fracture.

The fatigue testing machine that uses the force of torsion is invented to be a compact machine that uses the torsion as the force in the test. From the tests it achieved the highest of 200 newton meters using pneumatics to test the metal materials i.e. the steel S45C molded in accordance with the JIS Z 2274 standard. To find out the capacity of the fatigue testing machine that uses the force of torsion with 8 mm 10 mm and 12 mm diameter test pieces the machine was tested with different levels of the force of torsion and the percentage of the deviation of the tests did not exceed the limit of + 10 percent. This research could reduce the cost of the procurement of the fatigue testing machine that uses the force of torsion and could be used in the instruction in the department of mechanical engineering faculty of engineering Rajamangala University of Technology Phra Nakhon in the future.

The purpose of this research was to construct the rotating bending fatigue testing machine for metal material to find out the built-in machine performance and compare it with machines that meet international standards. The machine built into a compact machine using weight knob for a heavy load in testing. It can test the force range 50-300 Newton (N) the motor is a 1 HP transmitter with a speed of 2800 rpm. Start by pressing the Start button to release the weight that sends power to the workpiece and attend a sensor counting is available to detect the lack of testing material. For the efficiency performance of the machine uses 10 piece steel shafts diameter of 8 mm according to the standard of the material fatigue tester by independent end bend rotation. For testing to compare with the test international standard machine also uses 10 piece steel shafts using force 150 N. For the analysis to test statistical hypotheses with the Minitab computer program at the significance level of 0.05 it was found that the values obtained from be made the rotating bending fatigue testing machine for metal material there is no difference with standard machines from statistically significant. All values are within the set limits. In conclusion the machine was created to be as effective as the international standard machine.

The damaged propeller shafts caused by the fatigue failure will be repaired by shield metal arc welding process. The service life dependeds on fatigue endurance limit of welding surface. This study was aimed to compare the fatigue resistance of two types of hard facing electrodes using the same arc welding repair process. The investigation of fatigue stress at 517 MPa in failure criteria showed that the propeller shafts repair by Flux core arc welding Process using electrode grade E110T5-K4H4 provided the approximate same service life as that using electrode grade X111-T5-K4 but lowered the repair costs up to thirty-five bath per kilogram electrode. As a result the total maintenance cost decrease 68250 baht per year.