Anti-buckling fatigue test assembly

An antibuckling fatigue test assembly is described for holding a metal specimen which is subjected to compression and to rapid cyclical heating and cooling while permitting visual observation. In an illustrative embodiment of this invention, the anti-buckling fatigue test apparatus includes first and second guide members between which the metal specimen is disposed and held, a heating assembly comprising a suitable heating source such as a quartz lamp and a reflecting assembly directing the heat onto the specimen, and a cooling assembly for directing a suitable cooling fluid such as air onto the specimen. The guide members each have a passage to permit the heat to be directed onto the specimen. An opening is provided in the reflecting assembly to permit visual inspection of that region of the specimen adjacent to the opening onto which the heat is directed

Characterisation of a resonant bending fatigue setup for pipes

This paper discusses the resonant bending fatigue test setup designed at laboratory Soete for full-scale fatigue tests on pipes. Following an enumeration of other types of fatigue test setups an attempt is made to characterise the resonant bending machine. The characterisation is obtained by conducting different tests on a steel pipe of grade API X65. Concordance between measured and calculated stresses and influence of excentre position on stress amplitude is discussed. High frequencies and small power input make this test setup very effective. The analytical model correctly predicts the measured stresses and a stress versus excentre curve is obtained. However not yet fully defined, it gives a first indication for the excentre position when preparing for a fatigue test

Review and classification of fretting fatigue test rigs

There is no standard or generally accepted test rig for fretting fatigue experiments. Therefore, researchers adopt an existing concept, or build a new test rig that meets their specific requirements. However, too many different test rigs may be disadvantageous because the results of two different test rigs are hard to compare. The increasing amount of diversity is mainly caused by the lack of a recent literature survey on fretting fatigue test rigs. In 1994, Hills and Nowell described a few test rigs in Mechanics Of Fretting Fatigue. In this study, the authors made a classification of test rigs based on the contact geometry, which is determined by the test specimens, not by the test rig itself. The authors of this article present a review of the available literature, and present a classification based on the properties of test rigs. Fretting fatigue test rigs are first divided in two categories based on the geometry of the test specimen: full scale and coupon scale test rigs. The latter are mostly used to perform research and are subdivided in categories based on increasing functionalities. This is the ability to apply a fatigue load, a constant normal force, and an alternating slip in the range of some micrometers. In time, from the fifties until now, progress has been seen in the design of fretting fatigue test rigs. More parameters can be controlled during experiments and more measuring techniques are incorporated. State of the art test rigs are classified in the last category with mostffunctionalities, but still have imperfections. Future designers can use this article to classify their needs, or help to design a better test rig knowing the imperfections of the state of the art test rigs

Cryostat modified to aid rotating beam fatigue test

Modified stainless steel Dewar aids rotating beam fatigue test in a cryogenic environment. The Dewar is modified to receive extended specimen supporting members through specially designed rotary seals. The test set can be fully enclosed and pressurized with an inert gas to make the system explosion proof

A comparison of reliability and conventional estimation of safe fatigue life and safe inspection intervals

Both the conventional and reliability analyses for determining safe fatigue life are predicted on a population having a specified (usually log normal) distribution of life to collapse under a fatigue test load. Under a random service load spectrum, random occurrences of load larger than the fatigue test load may confront and cause collapse of structures which are weakened, though not yet to the fatigue test load. These collapses are included in reliability but excluded in conventional analysis. The theory of risk determination by each method is given, and several reasonably typical examples have been worked out, in which it transpires that if one excludes collapse through exceedance of the uncracked strength, the reliability and conventional analyses gave virtually identical probabilities of failure or survival

Heat pipe fatigue test specimen: Metallurgical evaluation

An innovative creep/fatigue test was run to simulate the temperature, mechanical load, and sodium corrosion conditions expected in a heat pipe designed to supply thermal energy to a Stirling cycle power converter. A sodium-charged Inconel 718 heat pipe with a Nickel 200 screen wick was operated for 1090 hr at temperatures between 950 K (1250 F) and 1050 K (1430 F) while being subjected to creep and fatigue loads in a servo-hydraulic testing machine. After testing, the heat pipe was sectioned and examined using optical microscopy, scanning electron microscopy, and electron microprobe analysis with wavelength dispersive x-ray spectroscopy. The analysis concentrated on evaluating topographic, microstructural, and chemical changes in the sodium exposed surfaces of the heat pipe wall and wick. Surface changes in the evaporator, condenser, and adiabatic sections of the heat pipe were examined in an effort to correlate the changes with the expected sodium environment in the heat pipe. This report describes the setup, operating conditions, and analytical results of the sodium heat pipe fatigue test

Fatigue test bench manufacturing by reusing a parallel lathe

Fatigue life of machined parts strongly depends on their surface condition. The rotating bar bending fatigue testing method is widely used to obtain the fatigue behavior of metallic materials due to its simplicity. In this work, the methodology for the design, manufacturing and setup of a fatigue test bench is exposed. The main novelty lies on the reuse of several elements from an old parallel lathe, currently out of order, and their use to manufacture some parts for the test bench. In this way, a double objective is achieved: high quality elements are recycled and the machine manufacturing cost is reduced.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

The pest phenomenon in intermetallics Quarterly report

Single crystal boules of molybdenum disilicide for performing static fatigue test

Design features and results from fatigue reliability research machines

Design and performance tests for reversed bending with steady torque fatigue test machine using notched steel specimen

Design of a fretting fatigue test rig with compliant springs

Fretting is a small amplitude oscillatory movement which occurs between contacting bodies who are subjected to cyclic loading or vibrations. In the contact area arise stresses -normal and tangential- causing stress concentrations and surface degradation. Fretting in combination with ordinary fatigue will reduce the plain fatigue lifetime due to the additional stresses and surface degradation. Applications susceptible to fretting fatigue are for instance connections techniques. By nature they have contacting bodies and transfer loads or vibrations. Connection techniques commonly seen in the field of fretting fatigue are lap-joints, dovetail connections and spline connections. Although mitigating or managing fretting fatigue is industrially relevant, academic research is confined and only revealed basic insights. Therefore, we developed a fretting fatigue test rig at Soete Laboratory. The paper describes the design of the test rig and points out some important features. To study the general phenomenon of fretting fatigue we selected a coupon scale test rig rather than a full scale test rig where only one application can be studied. The specimens used are one dog bone specimen and two indentation pads which make contact with the dog bone specimen. The normal force FN between the specimen and the pads is close loop controlled with a hydraulic actuator. A second hydraulic actuator controls the dynamic force Ffat in the dog bone specimen. A third force FT is introduced during dynamic loading between the dog bone specimen and the pads by means of compliant springs. The combination of these three forces: FN, Ffat, FT in the contact area gives rise to the fretting fatigue phenomenon. The test rig at Soete laboratory can be used to study fretting fatigue and examine mitigations such as surface texturing, surface work hardening, etc