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Fatigue testing is a method for determining the behavior of materials under fluctuating loads, applied in an alternating cycle until the material fails. Typically, the number of loading cycles to cause failure are recorded, along with the mean load and the alternating load applied to the specimen at failure. Data from fatigue testing is usually presented in an S-N diagram which is a plot of the number of cycles required to cause failure in a specimen against the amplitude of the cyclical stress developed.
RR Moore Rotating Beam Fatigue Testing System
This tool is intended for the study of flexural fatigue analysis. It has weights available in both English or metric units, adjustable rotational speeds from 500 - 10,000 RPM, a digital counter to provide the total number of cycles, and automatic shut-off upon specimen failure.
Bose ElectroForce® 3510 Test System
Localized corrosion fatigue testing at the Advanced Engineered Materials Center was enhanced with the purchase of Bose ElectroForce® 3510 test machine at the Mechanical Engineering Department of UND. It uses electromagnetic actuation (as in audio speakers) and has a capacity of ± 7500 N (~1500 lb). It was supplied with a custom-designed flow-through bath for corrosion fatigue testing in 4 point bending tension and compression.
|UND has two test jigs for the new Bose tester. The first is an acrylic cylindrical tank manufactured by Bose and supplied with the new test system. It can be used with either a static pool of electrolyte or with a flow through the tank. The tank was designed for a larger sample size than was used for some of the samples being tested, which required casting new silicone polymer seals for the tank.|
|The second is a new four-point bend fatigue corrosion tank. It is similar in design to the tank that was used on a Shimadzu test machine, but its size has been increased for more convenient access and to increase clearance between moving parts. The most noticeable change in the structure itself is in the sealing system. The rubber gasket design was modified for simplicity and to lessen the chance of leaks.|
Direct-Rolling Contact Fatigue Test System
Gear life is determined by a combination of design attributes, which determine tooth root bending fatigue, wear, and rolling contact fatigue (RCF). These parameters are affected by loading conditions, gear and tooth geometry, lubricant, and material. Failure occurs either by a single, dominant failure mode, such as tooth fracture, wear, pitting, micropitting or by a combination of these modes. The failure mode in RCF testing has been defined as the occurrence of catastrophic, visual pits which lead to excessive vibration of the test rig, and termination of the test. More recently however, in situ eddy current has been employed to detect cracks in the very early stages of initiation and to study crack growth resulting in a potentially new determination of material failure: crack initiation instead of pit formation.
The testing system pictured to the right was designed and built in-house by UND students under faculty supervision. It is capable of testing for rolling surface fatigue (without slip) and sliding and rolling fatigue with a variable slip rate. The system is also able to test samples in the presence or the absence of oil. The tester has been equipped with a data logger and a monitoring system to control and collect data, such as: loading, oil temperature, test speed, and specimen surface condition. Fabrication was completed and after performance testing, the instrument was commissioned for use by the Advance Engineered Materials Center.