High Stress Gradients Research Articles

Analysis of initiation and growth of new transverse cracks in high crack density regions in cross-ply laminates

In cross-ply laminates under loading, multiple intralaminar (transverse) cracking in the 90-layers causes laminate stiffness reduction which can be predicted by analytical models studying average of the stress perturbation between transverse cracks. The commonly used analytical models such as shear-lag type or variational-type models assume that stress in damaged 90-layers does not depend on the laminate thickness coordinate. But with increase in crack density, the stress perturbations created by transverse cracks start to interact, generating high stress gradients in through-the-thickness direction in the 90-layers. Location of a new crack and features of its propagation in a high stress gradient region between two cracks in a cross-ply laminate are analyzed in this paper. FEM is used to calculate stress distribution between two cracks. The location of the next crack and its initial orientation is found using principal stresses and orientation of principal axes. Most often these cracks are initiated at ply interface in the middle between already existing cracks. Their propagation across the layer thickness is analyzed using energy release rate based criterion. It is shown that at very high crack density the crack propagation across the layer thickness is unstable in the beginning, but it is stopped when approaching the middle of the layer where the crack opening becomes zero. Presence of local delaminations at the tips of existing cracks changes the energy release rate for propagation of new transverse cracks.

Hydrogen diffusion and precipitation influenced by non-uniformly distributed stress in zirconium alloy with different textures

Hydrogen embrittlement is a crucial factor for the performance and life of zirconium alloys in nuclear industry. During service, the residual stress in the materials induces re-distribution of hydrogen, which further affects the fracture behavior. This study is dedicated to investigating the hydrogen diffusion and precipitation under the meso‑scale non-uniform deformation field. The texture effect of hydrogen behavior was examined by considering three different texture scenarios: grains with c-axis deviating from the tensile direction of random angle, 0°and 90° The cases were termed Random, T000, and T0900 respectively. The crystal plasticity finite element method (CPFEM) was employed to simulate the stress-assisted diffusion of hydrogen atoms in the polycrystalline zirconium alloy. It is determined that the T0900 case gets fewer regions with higher hydrostatic stress gradient, which helps relieve the hydrogen concentration. Compared to the T0900 texture, the interaction between soft and hard grains in the Random and T000 texture conditions results in higher stress gradient and severe hydrogen concentration. Statistical analysis was conducted and the hydrogen concentration in the three textures presents a normal distribution. T0900 gets a relatively lower overall hydrogen concentration while the T000 texture gets severe hydrogen concentration larger than 120 wt.ppm. In Random and T000 textures, hydrogen tends to accumulate at grain interior and boundaries, and continuous hydrogen concentration band forms along adjacent GBs. The T0900 scenario is free of large continuous hydrogen concentration zones, which helps reduces the adverse effects of hydrogen diffusion and precipitation. The findings of the work advance the understanding of the hydrogen behavior affected by stress heterogeneity and texture, which is the basis for the exploration of hydrogen embrittlement.

Influence of corrosion fatigue on the stress gradient effect of the aluminium alloy EN AW-6082 T6

This study investigates the influence of corrosion fatigue on the fatigue strength of the aluminium alloy EN AW-6082 T6 with regard to the stress gradient. The experimental design involves varying loading conditions and specimen geometries to facilitate testing under three distinct stress gradients: tension/compression (0mm-1), rotary bending (0.2mm-1), notched rotary bending (5.3mm-1). Reference constant loading tests in air as well as continuously irrigated corrosion fatigue tests in a 5wt% NaCl-solution are conducted with a constant stress ratio of R =−1. The results reveal a substantial reduction in fatigue strength due to corrosion fatigue across all three stress gradients. The slope of the S-N curves drops by a factor of at least two and no second slope of the S-N curves is found within the tested load cycle range (up to 107). The study demonstrates a significant increase in the support factor for tests conducted in the corrosive environment. This discrepancy becomes more pronounced towards higher stress gradients and lower load cycle numbers. The application of the support factor derived from tests in a non-corrosive atmosphere is shown to be conservative, emphasizing the significance of accounting for corrosion effects in assessing fatigue behaviour.

An interlaminar fatigue damage model based on property degradation of carbon fiber-reinforced polymer composites

Interface delamination is a significant damage mechanism in fiber-reinforced polymer (FRP) laminated composites caused by interlaminar normal and shear stresses. This is due to the low interlaminar properties including interface stiffness and strength that continuously degrade to cause fatigue crack nucleation and growth. In this respect, an interlaminar fatigue damage model is proposed to accurately address the reliability aspect of the FRP composite materials and structures. The model considers a damage process that consists of two stages: (1) fatigue damage evolution due to interlaminar properties degradation to the onset of crack nucleation. A cyclic cohesive zone model with a bilinear softening behavior is introduced along with the fatigue life model to capture the mean stress effect of the interface. This is followed by (2) the crack nucleation process leading to the physical separation/debonding of the interface material point, as governed by the cycle-dependent fracture energy dissipation. The mechanical prediction of the interlaminar fatigue damage process is illustrated through finite element simulation of a mixed-mode flexural test of a carbon fiber-reinforced polymer (CFRP) composite beam subjected to fatigue loading. The results indicate that the interlaminar normal and shear crack opening displacement increases exponentially with the larger number of load cycles. In addition, the high-stress gradient is limited to the interface crack front zone with the normal and shear stress peaks at 69.2 and 16.5 % of the respective interlaminar strength. Moreover, controlled interlaminar crack growth is initially foreseen at 7.0 × 10-6 mm/cycle, followed by an abrupt crack “jump” at 287,000 load cycles.

Numerical Simulation Study on the Mechanics and Pore Characteristics of Tectonically Deformed Coal under Multi-Level and Multi-Cycle Loading and Unloading Conditions

Horizontal well cavern completion and stress release is considered a potential technique for efficient development of coalbed methane in tectonically deformed coal (TDC). Pulsating loading and unloading is a key technique for the controlled expansion of caverns and broader stress release within the reservoir. However, current understanding of the mechanical characteristics and pore network structure evolution of TDC under cyclic loading and unloading conditions is still limited. This paper employs numerical simulation methods to study the mechanical behavior and damage characteristics of TDC under cyclic loading and unloading. After obtaining a set of micromechanical parameters reflecting the behavior of TDC samples under triaxial compression in high-stress states, the effects of different stress gradients and cyclic amplitudes on the stress–strain curve, porosity changes, and crack propagation in TDC samples were analyzed. The study results indicate that under various cyclic loading and unloading conditions, the mechanical response characteristics of TDC samples are broadly similar, primarily divided into compression, slow expansion, and accelerated expansion phases. Under low unloading level conditions, the volume expansion of TDC samples is minimal. Also, at the same unloading level, the strain increment decreases with an increasing number of cycles. Correspondingly, under these conditions, the porosity and microcrack expansion in TDC are less than in high-stress gradient scenarios. Under the same unloading level but different amplitudes, the volume expansion rate at 50% unloading amplitude is higher than at 1 MPa unloading amplitude for TDC, with an increased number of crack expansions. Therefore, under cyclic loading conditions, the sensitivity of crack propagation within TDC samples to amplitude is greater than that to unloading level. Under actual pulsating excitation conditions, a low-amplitude, low-stress gradient pulsation method should be used to maintain the stability of horizontal well caverns, and gradually increase the cyclic amplitude to achieve the efficient extraction of coalbed methane in TDC reservoirs. The findings of this study can serve as an important reference for optimizing process parameters in cyclic pulsating stress release engineering for TDC.

Computations of J-integral and T*-integral in elastic–plastic fracture by the quadrature element method

In this paper, J-integral and T*-integral in elastic–plastic fracture are computed by the quadrature element method (QEM). Since high stress gradients exist in the immediate vicinity of the crack front, computing these integrals accurately is not a trivial task. The QEM facilitates the construction of arbitrarily high-order elements, which effectively capture the stress gradients, making it particularly suitable for this computation. After performing an elastoplastic stress–strain analysis of the fracture problem, the stress and deformation states are further formulated to compute the integrals. The integrals are formulated in several forms, including the contour and domain forms, as well as the incremental and total forms. Classical numerical examples are solved to demonstrate the effectiveness and high accuracy of the method. Overall, the equivalent domain integral (EDI) form outperforms the contour integral form because errors at the local contour have less effect on the integral. Moreover, the QEM yields more accurate solutions than the popular finite element method (FEM) that employs low-order finite elements and shares the same number of degrees of freedom. Additionally, it is found that the EDI form solution is not very sensitive to the specific type of the S function. Therefore, a linear function is suggested for convenience.

Non-monotonic plasticity and fracture in DP1000: Stress-state, strain-rate and temperature influence

Recent studies revealed a complex, non-monotonic relationship between flow stress, and temperature and strain rate for ultra-fine-grained DP1000 steel, including unexpected drops in ductility. Consequently, a comprehensive investigation into the interrelated effects of temperature, strain rate, and stress state on the plasticity and fracture behaviour of DP1000 steel is undertaken. To this purpose, eight purpose-designed specimen geometries, including a shear, a dogbone, a central hole, and various notched samples, are tested at strain rates covering 7 orders of magnitude from the quasi-static over the intermediate to the dynamic regime and in a temperature range from -40 to 400 °C. The experimental design thereby provides 336 unique combinations of stress state, strain rate and temperature. The study reveals phenomena typically associated with dynamic strain aging (DSA), such as flow stress serrations, negative strain rate sensitivity, thermal hardening, and embrittlement. As a result, the present study provides a comprehensive overview of the plastic, damage, and fracture behaviour of DP1000 steel. It also offers unique insights into the influence of external loading conditions on DSA. Increasing strain rates and decreasing temperatures suppressed DSA and its effects. However, a novel and important finding is that the impact of stress state on DSA and, consequently, on the behaviour of DP1000 steel cannot be solely explained by stress triaxiality and Lode angle. Lower stress triaxialities and Lode angle parameters amplify the occurrence and severity of DSA manifestations. However, non-proportional stress states, high-stress gradients and relatively low maximum in-plane shear stresses are also identified as contributing factors.

Residual Stresses in Ribbed Reinforcing Bars.

Ribbed reinforcing bars (rebars) are used for the reinforcement of concrete structures. In service, they are often subjected to cyclic loading. In general, the fatigue performance of rebars may be influenced by residual stresses originating from the manufacturing process. Knowledge about residual stresses in rebars and their origin, however, is sparse. So far, residual stress measurements are limited to individual stress components, viz., to the non-ribbed part of the rebar surface. At critical points of the rebar surface, where most of the fatigue cracks originate, i.e., the foot radius regions of transverse ribs, the residual stress state has not yet been investigated experimentally. To extend the knowledge about residual stresses in rebars within the scope of this work, residual stress measurements were carried out on a rebar specimen with a diameter of 28 mm made out of the rebar steel grade B500B. In addition, numerical simulations of the TempCoreTM process were carried out. The results of the experimental investigations show tensile residual stresses in the core and the transition zone of the examined rebar specimen. Low compressive residual stresses are measured at the non-ribbed part of the rebar surface, while high compressive residual stresses are present at the tip of the transverse ribs. The results of the numerical investigations are in reasonable accordance with the experimental results. Furthermore, the numerical results indicate moderate tensile stresses occurring on the rebar surface in the rib foot radius regions of the transverse ribs. High stress gradients directly beneath the rebar surface, which are reported in the literature and which are most likely related to a thin decarburized surface layer, could be reproduced qualitatively with the numerical model developed.

A continuum mixture model for transient heat conduction in multi-phase composites

The difference between transient thermal responses of each constituent in composites is one of the important factors to cause significant nonuniform deformation, high stress gradient and failure of composites. While direct numerical simulations for transient heat conduction in multi-phase composites are highly costly and even formidable, classical homogenization methods are focused on predicting the effective conductivities and the macroscopic thermal responses of a whole representative volume element, leaving the prediction of this difference at the macroscopic level to be a challenging issue during structural analysis of composite materials. In order to solve this issue, we propose a continuum mixture model for the transient heat conduction in multi-phase composites through dynamic homogenization methods. The derived governing equations retain the identity of each constituent behaviour and relate them to the overall response of each constituent. All the coefficients in the equations can be directly determined by the constituent phases and geometric parameters through explicit relations. The precision of the model is verified by comparison with direct numerical simulations. The results indicate that the model not only captures the disparate thermal responses of each constituent at the macroscopic level, but also accurately predicates the macro-average responses. The methodology can be generalized to other non-equilibrium thermodynamic phenomena such as diffusion and other kinds of conduction in multi-phase systems.

Numerical analysis of hydrogen atom diffusion and trapping at an unconstrained dent on pipelines

In this work, a three-dimensional finite element-based mechanics-diffusion coupling model is developed to determine the stress/strain distribution and hydrogen (H) atom concentration at an unconstrained dent on an X52 steel pipe which is to be used for transport of high-pressure hydrogen gas. Both von Mises stress and equivalent plastic strain concentrations and a high hydrostatic stress gradient exist at the dent. The distribution of H atom concentration coincides with that of the hydrostatic stress. The maximum H atom concentration in the steel lattice locates at the dent bottom, while the distribution of the H atom concentration at metallurgical traps is consistent with that of the equivalent plastic strain. A competitive effect exists between the hydrostatic stress and the plastic strain on the H atom distribution. At low initial H atom concentrations (e.g., 0.001 mol/m3), the equivalent plastic strain dominates the distribution of H atoms. At high initial H atom concentrations (e.g., 0.1 and 1 mol/m3), the hydrostatic stress is more important to determine the distribution of H atom concentration. As the dent depth increases, both the von Mises stress and plastic strain at the dent increases, while the total H atom concentration decreases due to decreased hydrostatic stress. When the internal pressure increases from 5 MPa to 15 MPa, there are slightly increases in von Mises stress, equivalent plastic strain and the total H atom concentration.

Imaging the 2007 Mw 7.7 Tocopilla earthquake from short-period back-projection

The 14 November 2007 Tocopilla (MW 7.7) earthquake was the first large rupture (M > 7.5) in the 1877 Northern Chile seismic gap. The event only ruptured the lower seismogenic part of the megathrust, raising questions about the mechanism that prevented the trenchward rupture propagation. Here, we present the short-period rupture process of the Tocopilla earthquake from local strong-motion (2.0–8.0 Hz) and teleseismic (0.5–2.0 Hz) back-projections. P and pP teleseismic back-projections were combined from two arrays formed on broadband networks in North America and Africa. The kinematics of the earthquake rupture was also characterized by back-propagating S-wave envelopes from local accelerometers (≤ 200 km from the mainshock). The results show a complex rupture process, including a sub-event, from the distribution of short-period rupture emissions and the main slip asperities. The sub-event location agrees with published estimates based on S-wave arrivals and kinematic inversion. We also observed rupture emissions around the slip patches and systemically classified them relative to the asperities, i.e., down-dip, up-dip, and inside. The short-period emissions are balanced around the asperities, highlighting up-dip rupture emissions. We interpreted the up-dip emissions as a proxy of the high-stress gradient caused by a kink in the slab interface, proposed in previous literature to be the mechanism that arrested the trenchward propagation of the 2007 rupture. The down-dip limit of the Tocopilla event coincided approximately where the slab interface intersects the continental Moho. Thus, it is a region expected to be extensively serpentinized, i.e., the most seaward part of the mantle wedge, defining a velocity-strengthening margin and a source of short-period radiation. The high-stress gradient around the asperities is proposed to define a third source of short-period radiation that may contribute to rupture encircling emissions.

Numerical Analysis of Fracture Behaviour for Cracked Joints in Corrugated Plate Girders Repaired by Stop-Holes.

The efficient crack eliminated stop-hole measure was proposed to repair and reduce the stress concentration associated fracture risk of the corrugated plate girders by setting it at the critical joint of flange plate with tightened bolts and gaskets under preloading. To investigate the fracture behaviour of these repaired girders, parametric finite element analysis was conducted, focusing on the mechanical feature and stress intensity factor of crack stop-hole in this paper. The numerical model was verified against experimental results first, and then the stress characteristics due to the presence of crack open-hole were analysed. It was found that the moderate-sized open-hole was more effective than the over-sized open-hole in the reduction of stress concentration. For the model with prestressed crack stop-hole through bolt preloading, the stress concentration was nearly 50% with the prestress around open-hole increased to 46 MPa, but such a reduction is inconspicuous for even higher prestress. Relatively high circumferential stress gradients and the crack open angle of oversized crack stop-holes were decreased owing to additional prestress effects from the gasket. Finally, the shift from the original tensile area around the edge of the crack open-hole that was prone to fatigue cracking to a compression-oriented area is beneficial for the reduction of stress intensity factor of the prestressed crack stop-holes. It was also demonstrated that the enlargement of crack open-hole has limited influence on the reduction of stress intensity factor and crack propagation. In contrast, higher bolt prestress was more beneficial in consistently reducing the stress intensity factor of the model with the crack open-hole, even containing long crack.

Numerical simulation of the effect of surface microgeometry and residual stress on conformal contact fretting fatigue crack initiation behavior

AbstractConformal contact is a commonly presented contact form in assemblies. Non‐proportional loading is the main characteristics of conformal contact, which leads to prominent difficulty in revealing fretting crack behavior. In this paper, a finite element prediction model for Ti‐6Al‐4V pin‐hole contact fretting fatigue crack initiation was developed, which simultaneously considered the effect of fretting wear, surface roughness, surface skewness, surface kurtosis, and residual stress. The results show that phase differences of stress component, change in direction of principal stress, and high stress gradient are the main reasons for the initiation of fretting fatigue under conformal contact condition. The model based on the Fatemi–Socie (FS) parameter successfully predicted the location, orientation, and fatigue life of crack initiation, which agrees well with the experimental results. Additionally, machining‐induced residual stress can effectively inhibit mode I crack initiation at valleys. Moreover, ignoring the surface microgeometry characteristics reduces the prediction accuracy of the crack behavior.

Numerical modelling of microstructure inhomogeneity to reproduce experimentally observed scatter in fretting fatigue lifetimes

Experimental fretting fatigue lives exhibit large degree of scatter. One of the aspects behind this is the microstructural inhomogeneity which affects the stresses in the material. Variance in stress values can greatly impact crack initiation speed, leading to changes in fretting fatigue lifetimes, as well as the crack propagation behaviour. This research aims to study this issue in more detail and recreate the experimentally observed scatter using numerical modelling. In this work, Voronoi tessellation is used to simulate microstructural topologies of low carbon steel, where each grain is assigned elasto-plastic properties at random, from a predetermined range. In total, 60 finite element models are created and the effect of microstructural inhomogeneity on fretting fatigue lifetime dispersion is evaluated using a Continuum Damage Mechanics approach. Additionally, crack propagation is studied with XFEM combined with Smith-Watson-Topper fatigue parameter to determine crack path under multiaxial, non-proportional loading conditions. For both crack initiation and propagation investigation, the Theory of Critical Distances is applied to overcome the effect of high stress gradients. Simulation results show that microstructural inhomogeneity has significant impact on the contact stress distributions and subsurface stress and strain fields. Scatter observed in the predicted lifetimes matches well with that observed in practical experiments and is used to propose a design curve for the studied material. The applied crack path prediction approach captures the variance in crack paths originating from microstructural inhomogeneity and shows good correlation with reference experimental results at low bulk stress levels.

Notch Fatigue Life Prediction Model Considering Stress Gradient Influence Depth and Weight Function

Notch characteristics significantly affect the fatigue performance of engineered components, for which the stress gradient effect is worth careful consideration. The traditional stress gradient analysis method based on the Coffin–Manson equation does not take into account the stress gradient influence range regarding the definition of the stress gradient correction factor, nor the high-stress gradient region, which has a greater influence on fatigue life. To address the aforementioned problems, a new notch fatigue life model is proposed in this paper. First, the stress–strain field at the root of the notch is analyzed to define the depth of stress gradient influence, following which the influence of the low-stress gradient region is reduced by a weighting function in the calculation of the stress gradient correction factor. Finally, to validate the method, three sets of experimental data, including TC4, GH4169, and EN8B, were used and compared with three other models. The results demonstrate that the predicted lifetimes of the new model are all within a 2-fold dispersion band, and the prediction ability is better than that of the other three models.

Statistical volume-based failure prediction of a quasi-brittle epoxy resin

Failure prediction of epoxy-based compounds becomes challenging when considering a highly divergent stress field and model singularities. In these cases, fracture and damage mechanics based failure models may be useful, though they have limited applicability and generalizability in complex architectures. In this study we propose a probabilistic volume-sensitive failure prediction approach which relies on the phenomenological behavior of rigid, quasi-brittle epoxy resins. The proposed model is based on a Weibull distribution, with a stress triaxiality modified equivalent strain failure criterion. We devise an experimental and numerical calibration method based on a test specimen subjected to high stress gradients. The scale sensitivity of a glassy epoxy resin under plastic flow with respect to failure strain is demonstrated. The model’s prediction of the failure load and the failure variability is verified. This approach shows great promise for failure prediction in various scales, loading conditions and configurations.

Effect of coarse aggregate grading optimization on temperature, thermal stress and compressive strength of carbon fiber-reinforced concrete by ohmic heating curing

The ohmic heating (OH) method is demonstrated to be promising for the curing of carbon fiber-reinforced mortar under ultra-low temperature condition. For the large-scale application in engineering and the reduction of carbon emission, the addition of coarse aggregates is necessary. However, coarse aggregates also influence on the temperature distribution and mechanical strength of OH cured concrete. This study proposed an optimization process of coarse aggregate gradation by combining particle packing theory with thermal simulation. The gradation was firstly decided by modified Andreasen & Andersen curve, and then optimized by the numerical simulation of temperature and thermal stress, in order to relieve the high thermal stress gradient in cold condition. The experimental results showed that the compressive strength of the samples with coarse aggregates of both 5–10 mm and 10–16 mm cured by 2 days OH curing at −20 °C reached 51.94 MPa, which was higher than samples including single aggregate diameter level, presenting a comparable strength value with 7 days room temperature (RT) curing. In addition, the microstructure and hydration products of concrete with OH and RT curing were compared and analyzed. This work will provide better guidance on the optimization design of mix proportion of carbon fiber-reinforced concrete for promoting the development of OH curing of concrete in large-scale practical applications.

Uniform Domain Equilibrium Equation with Finite Deformations

In corner areas of structures, high stress values and gradients occur, and lead to stress concentrations. Infinite stress and deformations are determined by a solution of the linear elasticity theory problem in the area with a wedge-shape boundary notch. Infinite solutions of the elasticity problem occur under impact of forced deformations, when a surge of the deformation value reaches beyond the area boundary. Relative values of stress concentrations for corner area zones make no more sense. At finite displacements, high deformation and stress values occur in the corner zones of the area. For a linear statement of the elasticity theory problem, at minor deflections, not only first-order, but also second-order derivatives of the displacements function are significant. To account for finite deformations of such corner zones of the area, correct formulations of elasticity problems are required. Study objective: influence determination of the infinitesimal order of the deformation on the appearance of equilibrium equations of an area with induced (temperature) deformations. This allows for the analysis of the influence of linear, shear deformations, and of the swing on the solution of the elasticity problem with induced deformations.

Component Tests and Numerical Investigations to Determine the Lifetime and Failure Behavior of End Stage Blades

Abstract The paper focuses on experimental and numerical fatigue assessment procedures to evaluate the influence of multi-axial stress state caused by high centrifugal forces superimposed with bending loads due to blade vibrations on the lifetime of end stage blades from steam turbines. The experimental investigations on original-sized end stage blades were carried out on a test rig specially developed for high forces and multicomponent force application. This was based on detailed numerical simulations by the MPA University of Stuttgart. During the fractographic postexaminations of the tested blades using magnetic particle inspection, light and scanning electron microscopes, two competing damage mechanisms were identified that occurred at different locations. Numerical investigations by means of elastic–plastic finite element analyses were carried out to estimate the local stress conditions acting in the blade root. The local stresses and strains were postprocessed using the critical plane approach and advanced multi-axial fatigue damage parameters. Due to the high stress gradients at the edge of contact, over-conservative predictions may result if their effects are not taken into account. Based on the critical plane method in conjunction with fatigue damage parameters, an approach taking the stress gradient into consideration was developed to predict the fatigue life of the end stage blades. The approach is verified by the component tests on original-sized blades.

Very high cycle fatigue assessment at elevated temperature of 100 μm thin structures made of high-strength steel X5CrNiCuNb16-4

Many components and structures are exposed to very high number of cycles and challenging environmental conditions during operation. This study contributes to a better understanding of the very high cycle fatigue (VHCF) properties of high-strength steel X5CrNiCuNb16-4 at room temperature (RT) and 350 °C. For this purpose, conventional specimens and thin-walled structures are extensively examined with novel high-frequency fatigue testing techniques at elevated temperature. Tests with unnotched specimens at 350 °C show a 21.7% reduction in fatigue strength for 107 cycles and a different failure mechanism compared to RT. In contrast, no temperature influence is observed for mildly notched specimens and even a higher local fatigue strength is found for sharply notched specimens at 350 °C. The decrease in fatigue strength for 109 cycles is more pronounced at 350 °C (−10%) than at RT (−5%), and it is proven that notched specimens adequately represent the VHCF behaviour of structures. The transferability of specimen results to components and structures is given great attention. A new proposal for the VHCF strength assessment of structures with high stress gradients is presented, which is based on specimen results, an extended material-mechanical support factor and a VHCF reduction factor. The prediction model gives conservative fatigue strength estimates for 109 cycles with a maximum deviation of 5.8%. This demonstrates that even complex shaped structures can be successfully evaluated with suitable specimens and methods.