Test method fatigue

Altstadt V, Loth W, Schlarb A (1996) Comparison of fatigue test methods for research and development of polymers and polymer composites. In Cardon AH, Fuduka H, Reifsnider KL (eds) Progress in Durability Analysis of Composite Systems. Balkema, Rotterdam, pp 75-80... 

H. Helmi Attia, R.B. Waterhouse Standardization of Fretting Fatigue Test Methods... 

G.D. Sims and A. Vanas, Round-robin on fatigue test methods for polymer matrix composites. Part I, Tensile and flexural tests of unidirectional material, NPL Report DMM(A)180, 1989. 

Fig. 5.16 Up-and-down or stair case fatigue test method used to determine mean fatigue limit at 2-10 cycles (the example refers to a carbon steel)...

ISO/DIS 12111 Metallic materials—Fatigue testing—Strain-controlled thermomechanical fatigue testing method... 

Data for thermal movement of various bitumens and felts and for composite membranes have been given (1). These describe the development of a thermal shock factor based on strength factors and the linear thermal expansion coefficient. Tensile and flexural fatigue tests on roofing membranes were taken at 21 and 18°C, and performance criteria were recommended. A study of four types of fluid-appHed roofing membranes under cycHc conditions showed that they could not withstand movements of <1.0 mm over joiats. The limitations of present test methods for new roofing materials, such as prefabricated polymeric and elastomeric sheets and Hquid-appHed membranes, have also been described (1). For evaluation, both laboratory and field work are needed. 

Tire cords are characterized for their physical, adhesion, and fatigue properties for use in tires. These characterizations are conducted under normal and varying test conditions to predict their performance during tire operation. Various test methods used to characterize tire cords are described. 

Rotating Beam Fatigue Test for Steel Cords. The purpose of this test method is to evaluate steel cord for pure bending fatigue (121). The test sample consists of a 3-mm diameter mbber embedded with steel cord. Different bending stress levels are appHed and the time to failure is recorded. The test stops at 1.44 million cycles. The fatigue limit is calculated from S—N (stress—number of cycles) curve. 

In the case of a pressure vessel subjected to cyclic loading (as here) cracks can grow by fatigue and a vessel initially passed as safe may subsequently become unsafe due to this crack growth. The probable extent of crack growth can be determined by making fatigue tests on pre-cracked pieces of steel of the same type as that used in the pressure vessel, and the safe vessel lifetime can be estimated by the method illustrated in Case Studv 3. 

Special requirements for fatigue testing in aqueous environments are addressed in the Annexe to ASTM E647 1986a Standard Test Method for Measurement of Fatigue Crack Growth Rates . 

Test method for measurement of fatigue crack growth rates... 

There are several other comparable rheological experimental methods involving linear viscoelastic behavior. Among them are creep tests (constant stress), dynamic mechanical fatigue tests (forced periodic oscillation), and torsion pendulum tests (free oscillation). Viscoelastic data obtained from any of these techniques must be consistent data from the others. 

In order to accurately model the fatigue behavior of rubber, fatigue analysis methods must account for various effects observed for rubber during constant amplitude testing. Effects associated with load level, 7 -ratio (ratio of minimum to maximum loading level), and crack closure are presented in this section. 

Fatigue testing can be adapted to the application, by using special loading sequences derived from studies of the service conditions. Examples are in aircraft, trucks and prostheses. The fatigue of composite materials for use in aircraft has been studied extensively and methods proposed for the calculation of lifetime under variable or random loads. 

ISO 9653 1998 Adhesives - Test method for shear impact strength of adhesive bonds ISO 9664 1993 Adhesives - Test methods for fatigue properties of structural adhesives in tensile shear... 

Dimensional methods having use in the laboratory have been reviewed in connection with swelling measurements.17, 18 The length of cracks can in fatigue tests can be manually measured by conventional methods or continually recorded with a video camera. An electrical method of crack measurement has been used for plastics19 that in principle could be applied to rubbers. 

Methods G and H are obviously not directly comparable with the other adhesion methods. They could be called static fatigue tests, or perhaps creep... 

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