Standardised load‐time histories – a contribution to durability issues under spectrum loading

Abstract

It is well established that the fatigue performance of materials and structures may be very sensitive to the specifics of the loading encountered. Beside constant amplitude testing, therefore, tests with realistic load sequences are often requiered in order to to assess any susceptibility to the specifics of variable amplitude loading and to demonstrate the in-service integrity for given materials and sructures .For these purpose standardised load-times histories (SLH`s) have been developed for 30 years since it has been recognised that the use of SLH`s a series of adventages - both for studies of a more generic nature and practical applications. Starting with Gassner`s block programm test, some features of standardised load-time histories availible at present and their relevance for fatigue behaviour of materials and structures are reviewed

Load spectra and fatigue damage: applications to the automotive industry

“…Heuler & al. [12,13,14,15] published a comprehensive review where each cited example is collected with its own purpose, the intended structural application, a brief qualification, and some more technical details like the block size.…”

“…According to [13,14], we make use of the following equation: (6) where the pattern of the spectrum is based on an exponential law and ν is the sole spectrum parameter, called the shape exponent. This equation may be plotted in a dimensionless field, see figure 4, considering the amplitude load ratio r i = S i / S max on the Y-axis and the occurrences ratio log H i / log H 0 on the X-axis.…”

“…Standard load spectra according to [13,14] -effective occurrences, N. Figure 5 allows us to give a physical meaning at the shape parameter, ν . A unit value is associated to a linear pattern (please note that abscissa is in log scale), so that ν < 1 corresponds to ∂²N/∂S² < 0 and a concave spectrum, for which the lower the load, the greater is the occurrence, whereas ν > 1 corresponds to ∂²N/∂S² > 0 and a convex spectrum, for which the larger occurrence is not associated to the weakest load anymore.…”

Effects of variable amplitude loading on fatigue life

“…WISPER has been designed to describe the load spectrum of wind turbine blades. A summary of standardised spectra for multiple purposes can be found in [6]. Load spectra are often counted by different methods, such as the level crossing counting method or the rainflow method [7,8] to evaluate linear damage accumulation or to execute data reduction.…”

Analysis of Vibrations in Interior Permanent Magnet Synchronous Motors Considering Air-Gap Deformation

“…The main parameters of the machine are given in Table 1. The stator core of the IPMSM used in the in-wheel motor system may deform because of the impacting loads from the excitations of different road surfaces [23][24][25]. The relationship between the magnitude of the deformation and the impacting loads will be discussed in the further investigations.…”