Development of in-situ fatigue crack observing system for rotating bending fat.PDF (original) (raw)

Design and Development of Fatigue Machine: Rotating Bending Fatigue Testing of Different Materials

international journal of advanced engineering and management, 2019

Fatigue fracture is the most common type of failure as more than 75-90% of documented materials' failure in engineering components due to cyclic loading. So, it is preeminent to test the materials before use. This research work has been done in order to design and fabricate "Rotating Bending Fatigue Testing Machine" which is simple to understand, perform, portable, safe for use and more economical than others. A rotating bending fatigue testing machine was developed by keeping in mind the basic concepts of technical theory of bending of elastic beams. Different specimens of 6mm to 8mm diameter of different materials were tested under various loads to analyse the performance of this machine. The experimental readings and theoretical calculations indicate that the results were promising to agreement of the objective had been achieved. It was detected that the machine has the abilities of generating reliable bending stress-number of cycles data; and the cost of design (31,500 PKR) was lower in evaluation to that of rotating bending machines from abroad.

Design and Development of Fatigue Machine: Rotating Bending Fatigue Testing on different Materials

2019

Fatigue fracture is the most common type of failure as more than 75-90% of documented materials' failure in engineering components due to cyclic loading. So, it is preeminent to test the materials before use. This research work has been done in order to design and fabricate "Rotating Bending Fatigue Testing Machine" which is simple to understand, perform, portable, safe for use and more economical than others. A rotating bending fatigue testing machine was developed by keeping in mind the basic concepts of technical theory of bending of elastic beams. Different specimens of 6mm to 8mm diameter of different materials were tested under various loads to analyse the performance of this machine. The experimental readings and theoretical calculations indicate that the results were promising to agreement of the objective had been achieved. It was detected that the machine has the abilities of generating reliable bending stressnumber of cycles data; and the cost of design (31,500 PKR) was lower in evaluation to that of rotating bending machines from abroad.

Design and Fabrication of Rotating Bending Fatigue Testing Machine-A Laboratory Development Project

Fatigue failures are reported to account for more than 75% of documented materials failures of which a great percent occur catastrophically. Study of fatigue life is essential in many industrial and specialized fields such as aerospace, defense, power generation etc. Fatigue life of a component can be found by various fatigue testing machines based on the loading condition. In the present study a low-cost four point loading rotating bending fatigue testing machine is designed, fabricated and tested. The design principle is based on the adaptation of the technical theory of bending of elastic beams. The machine performance was evaluated using test specimens which were machined in conformity with standard procedures. It was observed that the machine has the potentials of generating combined bending and torsional stress. Specimens of diameter varying between 6 to 8 mm where subjected to loads between 30Kgs to 90Kgs and the number of cycles to failure was found by both experimental meth...

A Review on Design and Fabrication of Fatigue Testing Machine

2018

Simpler Design arrangement was used and Rotating Bending Fatigue Test (R.B.F) machine was fabricated using local availability of raw materials to make design arrangement simpler, due of its higher market Price. The design approach was simpler in construction .Power was transmitted though vertically arranged pulley arrangement where it is further transferred to load transmitting members through universal joint. Rotating Mandrel for specimen holding , was press fitted inside the two bearings which are separated apart. Bearing Hub was supported on horizontal lever through bolted connection at either side .One end of Lever is hinged and supported on vertical structure. This design helped in understanding Dynamic scatter and their Prevention on these fatigue machines. Frequent Maintenance showed better performance for longer runs. Scatter observed in Machine can help to overcome by the operator itself. This design made a better understanding for correlation with experiment results. Exper...

Continuous Estimation of the Crack Growth Rate during Rotating‒Bending Fatigue Testing

Metals, 2019

A method for estimating the crack growth rate in steel during rotating‒bending fatigue testing is presented. Constant deflection tests were conducted in which the initial load remained constant prior to crack nucleation, when it decreased as the crack grew. In the proposed approach, steel samples were sharp-notched to produce a characteristic circular fracture upon loading and the final fracture area was correlated with a ratio of the load prior to fracture and the initial load. In this method, the deflection imposed is a function of a material’s elastic modulus rather than its yield strength and the correlation obtained to estimate the average crack length as a function of the instantaneous load is independent of the applied stress or steel grade.

A New Fatigue Testing Machine for Investigating the Behavior of Small Shear-Mode Fatigue Cracks

Experimental Techniques, 2015

The investigation of the behavior of small shear-mode fatigue cracks in the high-cycle fatigue regime is essential to understand the mechanism of rolling-contact fatigue failures, such as flaking in bearings and shelling in rails, from the fracture mechanics point of view. The stable growth of a shear-mode fatigue crack was achieved by applying static compression to a specimen in a cyclic torsion fatigue test. This loading condition is usually obtained by a combined tension-torsion testing machine with a servo-hydraulic control system. In this study, a new testing machine was developed and found to be superior to the servo-hydraulic testing machine in terms of price, operation/maintenance costs, operating speed, and installation volume. For substantiation and demonstration purposes, a shear-mode fatigue crack growth test with a bearing steel was also carried out using both the new and the conventional servo-hydraulic testing machines. The experiments revealed that under the same loading conditions, nonpropagating shear-mode cracks of similar size and geometry could be obtained by the respective testing machines. Thus, it was concluded that the new testing machine has equivalent capabilities to the servo-hydraulic testing machine in performing shear-mode fatigue crack growth tests.

metals Continuous Estimation of the Crack Growth Rate during Rotating-Bending Fatigue Testing

A method for estimating the crack growth rate in steel during rotating-bending fatigue testing is presented. Constant deflection tests were conducted in which the initial load remained constant prior to crack nucleation, when it decreased as the crack grew. In the proposed approach, steel samples were sharp-notched to produce a characteristic circular fracture upon loading and the final fracture area was correlated with a ratio of the load prior to fracture and the initial load. In this method, the deflection imposed is a function of a material's elastic modulus rather than its yield strength and the correlation obtained to estimate the average crack length as a function of the instantaneous load is independent of the applied stress or steel grade.

Fabrication and Analysis of Fatigue Testing Machine

Engineering of machines and structures needs to consider the impact of fatigue stresses to prevent catastrophic failures for this we make use of fatigue testing machine, this machine will determine the strength of materials under the application of cyclic load. Specimens are subjected to repeated varying forces or fluctuating loading of specific magnitude and the stress cycles to destruction are counted. In this project we have fabricated and analyzed the performance of the fatigue testing machine. To determine the efficiency of the machine, specimens various materials were taken and tested with initial test, at a stress value that is under the material's ultimate strength. Then the next test is made at a stress that is less that than that used in the first. The process is repeated with the values of stress decreasing and results are plotted.