Although the temperature dependence of interface strength has not yet been clarified, if the interfacial failure criterion is assumed to have no temperature-dependent characteristic (excluding the effect of the apparent interfacial strength variation induced by a variation of thermal residual stress), the micromechanical validity of the accelerated testing method can be verified theoretically. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard. To save time, some accelerated testing methods have been attempted, but with limited success. Such investigations could be helpful for improving the enameled wire high temperature performances. (For color version of this figure, the reader is referred to the online version of this book.). In this approach, finite element modelling is carried out on the adhesive joint to determine the stress, strain and fluid distributions throughout the bonded structure as a function of time (coupled mechanical-diffusion analyses). Test Temperature (°C) 2. The effect of degradation differs between materials and different material properties. Additionally, models of higher fidelity are to be obtained for the purpose of on-line diagnosis. These environmental conditions may also be cycled in combination. This can be clarified by the same examination at various temperature conditions. For more details on the different models see Brown and Greenwood, 2002; Maxwell et al., 2005. 19.9). The selection of aging conditions (e.g., light spectrum, intensity, temperature, atmospheric gases) can all have a major impact on the resulting degradation dynamics (Hermenau et al., 2010), making comparisons challenging even when following the ISOS protocols (Tanenbaum et al., 2012). Dose-corrected degradation rates have been proposed as a solution by Madsen et al. Although K and G can be related, the stress intensity method is less useful for adhesives, as K values are more difficult to calculate, and is limited to linear–elastic behaviour. [17] also investigated the degradation of fuel cells during OCV durability testing. Referenced Documents (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard. stability of an insulation at lower temperatures. Although a number of analytical models have been proposed for polymers, relating the rate of property change to the level of degrading agent, they tend to be used for comparative purposes and not for design, as there is no conclusive evidence of their universal validity. On one hand, there are pragmatic methods based upon ... coupled with low testing and test personnel budgets have caused a renewed interest in Accelerated Stress Testing. This type of insulation is obtained in 2 passes. Elect. crack initiation and propagation), see Section 19.4.3. Cracks are restricted to propagating along the layer of cohesive elements in a self-similar manner. The main advantage of the fracture mechanics approach in design analysis is that geometry-independent results are generated from the laboratory tests. Fracture mechanics may be considered to be complimentary to stress-based approaches, which are useful in initial design. Capacitance as function of time for insulation aged in 230, E. L. Brancato, “Insulation Aging a Historical and Critical Review,”, G.C. This has led to the development of accelerated testing methods exposing the material to high CO2 concentrations to induce carbonation. The elastic and strength properties and stress–strain response of the adhesive and substrate materials can be measured experimentally and used directly for modelling purposes. Rep. Conf. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. The essential components will include both energy storage devices (fuel cells, batteries and ultra-capacitors) and energy conversion devices (electrical machine drives and power electronics). This method can be used to assess the insulation life of an electromagnetic coil, allowing replacement prior to the formation of harmful shorts or critical coil opens. This paper examines some existing thermal aging tests, which are currently used to obtain data for enamel degradation in order to try to better understand of how the thermal stresses degrade the EIS. Stress-assisted acceleration would lead to damage growth processes. Accelerated Aging calculation is based on Arrhenius’ equation which simply states that a 10C increase in temperature doubles the rate of chemical reaction. The insulation samples have been aged thermally at 200 – 275 OC and for 100 – 1600 hours. Related Products If the matrix strength decreases more significantly than the interfacial strength with an increase in temperature, for a consideration of thermal residual stress effect, more rapid tensile testing is required to make the specimen fail in the interface failure dominant mode; the transition between interface and matrix failure dominant modes moves to the rapid testing speed side as the temperature increases. The time of simulated aging depends on the temperature at which the products are … The specimens were isothermally aged at controlled stress levels in order to accelerate the oxidation and damage growth in the specimen. The paper deals with a new indicator for monitoring the turn-to-turn insulation aging of ac motors. correlated to PDIV for AC motors monitoring,”IEEE Trans. 4.4 Conservative accelerated aging factors (AAFs) must be used if little is known about the sterile barrier system material being evaluated. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Refer to Practice D4332 for standard conditions that may be used to challenge the sterile barrier system to realistic extremes in temperature and humidity conditions. It may also be used for damage tolerance calculations, which are required by certain design codes particularly for military applications. The specimen is maintained under a constant load while the temperature is increased in a series of steps to accelerate the creep. Accelerated aging methods are essential for material such as high temperature polymer matrix composite (HTPMC) as its expected operating life is several thousands of hours. Sample specimens were analysed after ageing for 100 hours in terms of their physical properties (surface roughness, mass), chemical properties (Fourier Transform Infra-Red (FTIR) spectroscopy), dielectric properties (capacitance, dissipation factor and impedance) and electrical properties (voltage breakdown strength and resistance). So far in this chapter we focused on the various effects that our environment has on plastics parts and their properties. aerospace, nuclear, will be reviewed for potential application and/or tailoring for purpose. Table 12.1 shows a summary of the testing methods and protocols used for the assessment of the carbonation resistance of cementitious materials. This result will certainly be helpful for discussing the long-term durability of composite strength, and this issue should be investigated in the near future. for rotating machines, design, evaluation, aging, testing and repair. As an accelerated testing method, the OCV hold test plays an important role in accelerated durability tests [13–18]. This accelerated test does not correlate exactly with the natural aging of the adhesive because of the varied conditions of natural aging and the absence of factors such as moisture and stress. Products and Services / Standards & Publications / Standards Products, Active Standard ASTM D5427 | Developed by Subcommittee: D13.20, Permissions to reprint documents can be acquired throughCopyright Clearance Center   lost its load-carrying capacity). Ida Idayu Muhamad, ... Eraricar Salleh, in Durability and Life Prediction in Biocomposites, Fibre-Reinforced Composites and Hybrid Composites, 2019. With the strain energy release rate method, the nonlinear effects of viscoelasticity and plasticity can be more readily accounted for in the analysis. These mechanisms can be described by fracture mechanics, thus providing a basis for estimating the fracture, fatigue and service life of joints. [16] studied membrane degradation behavior during an OCV hold test and found that Pt bands were formed in their three membrane samples, as shown in Fig. It is evident that the accelerated carbonation conditions vary significantly depending on the protocol adopted, and in those cases where very high concentrations of CO2 are used, it is important to consider the disruption suffered by the material, and to question the real meaning of the results in giving a good representation of a natural carbonation process. (2013), and yet the convolution of light intensity and temperature increases is a fundamental problem in accelerated testing, which complicates the interpretation of the results (Visoly-Fisher et al., 2015). Hence the need for accelerated testing methods and prediction techniques to simulate long-term service conditions. A scalar damage variable, D, which has an initial value of zero and evolves towards one, is used to represent the overall damage. Development of oxide based electric insulation system, Hybrid electric vehicles (HEV) are far more complex than conventional vehicles. ... Electrical insulation materials in machines are subjected to a multitude of stresses over the course of their lifetime, including thermal, electrical, ambient (e.g.