Basquin Law Research Articles

Lifetime prediction for press pack IGBT device by considering fretting wear failure

The reliability of the Press-Pack Insulated Gate Bipolar Transistor (PP-IGBT) device is important to guarantee the safety of modular multilevel converter (MMC). The fretting wear failure is the typical failure mode of long-time operation in the PP-IGBT device. However, the traditional fretting wear lifetime model of the PP-IGBT device only considers the fretting wear failure of the IGBT chip, which is difficult to accurately predict the reliability of the PP-IGBT device. The influence of fretting wear failure of all layers on the device's lifetime is ignored. This paper proposes a lifetime model of the PP-IGBT device by considering the fretting wear failure of all layers using the fault tree method. First, a finite element (FE) model of the PP-IGBT device is established by considering the multi-physics coupling, and the contact surface roughness change of each layer is obtained by power cycling simulation. Then, based on fretting wear failure and Basquin law, the lifetime of each layer is obtained, and a fault tree method is established to build the fretting wear lifetime model of the PP-IGBT device by considering the fretting wear failure of all layers. Finally, the power cycling experiment of the PP-IGBT device is established, and the experiment results are used to verify the effectiveness of the proposed lifetime model. The results show that the relative error between the proposed lifetime model and the experimental results is nearly 5 %.

Breaking down chipping and fragmentation in sediment transport: the control of material strength

Abstract. As rocks are transported, they primarily undergo two breakdown mechanisms: fragmentation and chipping. Fragmentation is catastrophic breakup by fracture in the bulk – either by subcritical crack growth under repeated collisions, or from a single high-energy (supercritical) collision – and produces angular shards. Chipping is a distinct low-energy mechanism of impact attrition that involves shallow cracking; this process rounds river pebbles in a universal manner under bed-load transport. Despite its geophysical significance, the transition from chipping to fragmentation is not well studied. Here, we examine this transition experimentally by measuring the shape and mass evolution of concrete particles of varying strength, subject to repeated collisions in a rotating drum. For sufficiently strong particles, chipping occurred and was characterized by the following: attrition products were orders of magnitude smaller than the parent; attrition rate was insensitive to material strength; and particles experienced monotonic rounding toward a spherical shape. As strength decreased, we observed the onset of a subcritical cracking regime associated with fragmentation: mass of attrition products became larger and more varied; attrition rate was inversely proportional to material strength; and shape evolution fluctuated and became non-monotonic. Our results validate conceptual and numerical models for impact attrition: chipping follows “Sternberg's law” of exponential mass loss through time; for fragmentation, the lifetime of particles increases nonlinearly with material strength, consistent with “Basquin's law” of fatigue failure. We suggest that bedrock erosion models must be clarified to incorporate distinct attrition mechanisms, and that pebble or bedrock-channel shape may be utilized to deduce the operative mechanism in a given environment.

An analytical relation between the Weibull and Basquin laws for smooth and notched specimens and application to constant amplitude fatigue

AbstractStarting from the classical definition of stress‐life Wöhler curve in the form of the Basquin law, an analytical procedure for the calibration of the four parameters' Wöhler curve (the Weibull law) for a plain specimen is proposed. The obtained parameters are then adjusted by means of an additional slope factor preserving the inflection point of the curve while changing its slope in order to model the experimental observations in which an increase of the scatter in life prediction is observed when reducing the stress amplitude. The same approach has then been adopted to calibrate the Weibull law parameters for a notched specimen, and the fitting slope factor has been found to be a value that changes with the material but remains constant with the stress concentration factor. The findings have been validated with existing experimental data on 2024‐T3 aluminum alloy and normalized SAE 4130 steel.

Estimation of the Fatigue Curve of a Wire Rope at Different Scales

The wire rope 19 × 7 is a complex component, it consists of 18 strands in helical from around a central core strand, each strand consist of a 7 wires laid in helical. The friction in wire rope between wire and wire decrease its lifetime. For that, this study is an attempt to present a simplified approach to predict the lifetime of cable in three scale (wire, strand, cable) using unified theory and the Basquin's law, at the level of the strand scale we have estimated its fatigue behavior in the initiation phase and also within the number of the cycle to failure as well as the ratio of the number of cycles to crack initiation Ni to the number of cycles to failure, we based on the tensile test.

A Method for Prediction of Femoral Component of Hip Prosthesis Durability due to Aseptic Loosening by Using Coffin/Manson Fatigue Model.

The purpose of this work is to develop a new model estimate of the fatigue life of a hip prosthesis due to aseptic loosening as a multifactorial phenomenon. The formula developed here is a three-parameter model based on Basquin's law for fatigue, eccentric compression formula for the compressive stress and torsion in the prosthesis due to the horizontal components of the contact force. With our model, we can accurately predict the durability of a hip prosthesis due to the following four parameters: body weight, femoral offset, duration, and intensity of daily physical activities of a patient. The agreement of the prediction with the real life of the prosthesis, observed on 15 patients, is found to be adequate. Based on the formula derived for a particular implant, there was a high degree of concurrence between the model-predicted and actual values of aseptic loosening (durability) proved by the Mann–Whitney U test. By virtue of the validated model, it is possible to predict, quantitatively, the influence of various factors on the hip life. For example, we can conclude that a 10% decrease of a patient's body mass, with all other conditions being the same, causes 5% increase of the hip fatigue life.

Modelling the influence of laser drilled recast layer thickness on the fatigue performance of CMSX-4

This paper introduces a novel approach to fatigue life prediction modelling considering the laser drilling effect on film cooling holes of turbine vanes. The methodology proposed is based on a stress-life model such as the Basquin law and the introduction of manufacturing damage effect. The proposed empirical model gives a unique versatility compared to other stress-life models by considering surface damage such as the recast layer produced by the laser drilling process. The proposed empirical model has been thoroughly tested and validated using existing fatigue data. The statistical analysis shows that the proposed model is adequate for estimating the fatigue life of laser drilled specimens considering the recast layer thicknesses effect. The proposed model also can estimate the life of untested specimens even when only a small sample of fatigue data is available, thereby reducing the required testing data.

Fatigue characteristics of sand-cast AZ91D magnesium alloy

The fatigue characteristics of the AZ91D-T6 alloy samples taken from engine blocks have been investigated at 20 °C and elevated temperature (150 °C). The fatigue strength and cyclic stress amplitude of the alloy significantly decrease with the increase of the test temperature, although cyclic hardening occurs continuously until failure for both temperatures. With the increase of the temperature, the decreased fatigue life of the alloy tested at the same stress amplitude is mainly attributed to the decreased matrix strength and the increased hysteresis energies. Fatigue failure of the engine blocks made of AZ91D-T6 alloy is mainly controlled by casting defects. For the defect-free specimens, the crack initiation behavior is determined by the single-slip (20 °C) and by environment-assisted cyclic slip (150 °C) during fatigue, respectively. The low-cycle fatigue lives of the alloy can be predicted using the Coffin-Manson relation and Basquin laws, the three-parameter equation and the energy-based concepts, while the high-cycle fatigue lives of the alloy fitted well with the developed long crack life model and MSF life models.

Effect of Nd additions on fatigue characteristics of a cast Mg–Zn–Zr alloy

Abstract

Fitting fatigue data with a bi‐conditional model

AbstractThe formulation of a probability‐stress‐life (P‐S‐N) curve is a necessary step beyond the basic S‐N relation when dealing with reliability. This paper presents a model, relevant to materials that exhibits a fatigue limit, which considers the number of cycles to failure and the occurrence of the failure itself as statistically independent events, described with different distributions and/or different degree of scatter. Combining these two as a parallel system leads to the proposed model. In the case where the S‐N relation is a Basquin's law, the formulations of the probability density function, cumulative distribution function, quantiles, parameter and quantile confidence interval are presented in a procedure that allows practically any testing strategy.The result is a flexible model combined with the tools that deliver a wide range of information needed in the design phase. Finally, an extension to include static strength and applicability to fatigue crack growth and defects‐based fatigue approach are presented.

Deformation Behavior of Recycled Concrete Aggregate during Cyclic and Dynamic Loading Laboratory Tests.

Recycled concrete aggregate (RCA) is a relatively new construction material, whose applications can replace natural aggregates. To do so, extensive studies on its mechanical behavior and deformation characteristics are still necessary. RCA is currently used as a subbase material in the construction of roads, which are subject to high settlements due to traffic loading. The deformation characteristics of RCA must, therefore, be established to find the possible fatigue and damage behavior for this new material. In this article, a series of triaxial cyclic loading and resonant column tests is used to characterize fatigue in RCA as a function of applied deviator stress after long-term cyclic loading. A description of the shakedown phenomenon occurring in the RCA and calculations of its resilient modulus (Mr) as a function of fatigue are also presented. Test result analysis with the stress-life method on the Wohler S-N diagram shows the RCA behavior in accordance with the Basquin law.

Multiple yielding processes in a colloidal gel under large amplitude oscillatory stress.

Fatigue refers to the changes in material properties caused by repeatedly applied loads. It has been widely studied for, e.g., construction materials, but much less has been done on soft materials. Here, we characterize the fatigue dynamics of a colloidal gel. Fatigue is induced by large amplitude oscillatory stress (LAOStress), and the local displacements of the gel are measured through high-frequency ultrasonic imaging. We show that fatigue eventually leads to rupture and fluidization. We evidence four successive steps associated with these dynamics: (i) the gel first remains solid, (ii) it then slides against the walls, (iii) the bulk of the sample becomes heterogeneous and displays solid-fluid coexistence, and (iv) it is finally fully fluidized. It is possible to homogeneously scale the duration of each step with respect to the stress oscillation amplitude σ0. The data are compatible with both exponential and power-law scalings with σ0, which hints at two possible interpretations of delayed yielding in terms of activated processes or of the Basquin law. Surprisingly, we find that the model parameters behave nonmonotonically as we change the oscillation frequency and/or the gel concentration.

Criticality of forcing directions on the fragmentation and resilience of grid networks.

A general framework for probing the dynamic evolution of spatial networks comprised of nodes applying force amongst each other is presented. Aside from the already reported magnitude of forces and elongation thresholds, we show that preservation of links in a network is also crucially dependent on how nodes are connected and how edges are directed. We demonstrate that the time it takes for the networks to reach its equilibrium network structure follows a robust power law relationship consistent with Basquin's law with an exponent that can be tuned by changing only the force directions. Further, we illustrate that networks with different connection structures, node positions and edge directions have different Basquin's exponent which can be used to distinguish spatial directed networks from each other. Using an extensive waiting time simulation that spans up to over 16 orders of magnitude, we establish that the presence of memory combined with the scale-free bursty dynamics of edge breaking at the micro level leads to the evident macroscopic power law distribution of network lifetime.

Creep and fracture of a protein gel under stress.

Biomaterials such as protein or polysaccharide gels are known to behave qualitatively as soft solids and to rupture under an external load. Combining optical and ultrasonic imaging to shear rheology we show that the failure scenario of a protein gel is reminiscent of brittle solids: after a primary creep regime characterized by a power-law behavior whose exponent is fully accounted for by linear viscoelasticity, fractures nucleate and grow logarithmically perpendicularly to shear, up to the sudden rupture of the gel. A single equation accounting for those two successive processes nicely captures the full rheological response. The failure time follows a decreasing power law with the applied shear stress, similar to the Basquin law of fatigue for solids. These results are in excellent agreement with recent fiber-bundle models that include damage accumulation on elastic fibers and exemplify protein gels as model, brittlelike soft solids.

Lifetime estimation in the low/medium-cycle regime using the Carpinteri–Spagnoli multiaxial fatigue criterion

A critical plane-based high-cycle multiaxial fatigue criterion, known as the Carpinteri–Spagnoli (C–S) criterion, is here extended to evaluate the fatigue lifetime of plain metallic components under constant amplitude loading in the low/medium-cycle regime. This extended criterion, based on strain components, resolves the strain tensor into the normal and shear components acting on the critical plane, which is determined on the basis of the principal strain courses over the loading cycle. An equivalent normal strain amplitude, computed through a quadratic combinations of strain components in the critical plane, is taken as the fatigue damage parameter. The required input parameters of the criterion are obtained from the classical Manson–Coffin–Basquin law for axial loading. A validation by experimental data pertaining the biaxial fatigue of plain steel specimens under both proportional and non-proportional loadings is performed.

Multiaxial ratcheting-fatigue interaction on acrylonitrile-butadiene-styrene terpolymer

A series of multiaxial tests on an industrial acrylonitrile-butadiene-styrene (ABS) tube were conducted at room temperature. The ratcheting strain accumulation was found to be closely related to the shear strain amplitude and axial mean stress. The ratcheting strain and its rate increased with increasing shear strain amplitude as well as axial mean stress. At the same time, the ratcheting strain accumulation was retarded with a negative mean stress, and the ratcheting shakedown appeared when the negative mean stress reached −10 MPa. To understand the influences of loading history on axial ratcheting strain, a series of multistep loading tests under constant symmetrical torsion at different axial mean stresses of 5, 0, and −5 MPa were performed. The results showed that both the compressive viscous strain and strain relaxation of ABS could lead to the decrease of axial ratcheting strain. Furthermore, the compressive viscous strain and strain relaxation are independent of the loading history. Considering the influence of mean stress, a modified fatigue life model based on the Basquin law was presented to predict the pure torsional fatigue and multiaxial fatigue of ABS. The results of the modified fatigue life model show it can give relatively accurate fatigue life predictions. POLYM. ENG. SCI., 55:664–671, 2015. © 2014 Society of Plastics Engineers

High-cycle fatigue behavior of severe plastically deformed binary Zn–60Al alloy by equal-channel angular extrusion

High-cycle fatigue properties, mainly the fatigue strength and fatigue life, of two-phase Zn–60Al alloy subjected to severe plastic deformation (SPD) via multi-pass equal-channel angular extrusion (ECAE) using two different routes, route-A and route-BC, were studied. The effect of ECAE processing parameters on the fatigue behavior of the alloy was investigated, and the stress amplitude versus number of cycles to failure (S–N) curves of the alloy were determined in the as-cast and multi-pass ECAE-processed conditions. The results showed that the fatigue performance of the alloy improved significantly through multi-pass ECAE. The fatigue endurance limit of the as-cast alloy reached to 146MPa from 79MPa. On the other hand, the fatigue properties of the ECAE-processed alloy were affected by ECAE parameters, and showed sensitivity to number of cycles and stress levels. Correlation of fatigue data showed that Basquin's law can be used to express the fatigue behavior of the multi-pass ECAE-processed alloy. Also, the ECAE processing changed the nature of fracture characteristics of the as-cast Zn–60Al alloy.

Unified nano-mechanics based probabilistic theory of quasibrittle and brittle structures: II. Fatigue crack growth, lifetime and scaling

This paper extends the theoretical framework presented in the preceding Part I to the lifetime distribution of quasibrittle structures failing at the fracture of one representative volume element under constant amplitude fatigue. The probability distribution of the critical stress amplitude is derived for a given number of cycles and a given minimum-to-maximum stress ratio. The physical mechanism underlying the Paris law for fatigue crack growth is explained under certain plausible assumptions about the damage accumulation in the cyclic fracture process zone at the tip of subcritical crack. This law is then used to relate the probability distribution of critical stress amplitude to the probability distribution of fatigue lifetime. The theory naturally yields a power-law relation for the stress-life curve (S-N curve), which agrees with Basquin's law. Furthermore, the theory indicates that, for quasibrittle structures, the S-N curve must be size dependent. Finally, physical explanation is provided to the experimentally observed systematic deviations of lifetime histograms of various ceramics and bones from the Weibull distribution, and their close fits by the present theory are demonstrated.

Multi-Axial Fatigue Properties under Tension-Torsion Loading for Short-Glass-Fiber-Reinforced Phenolic-Resin Matrix Composite

Static and fatigue tests under varying load ratio of tension and torsion at room temperature were carried out with short-glass-fiber-reinforced phenolic-resin matrix composites (GF/Phenol) made by injection-molded (S-series) and transfer-molded (P-series) processes. We investigated the short fiber content (Vƒ = 0%, 20%, and 50%) and stress ratio α = τ/σ effect on static and fatigue properties. Static strength and elastic modulus in uniaxial loading conditions were higher with increasing short fiber content. Furthermore, sensitivity for short fiber content of the injection-molded process was higher than that of the transfer-molded one. Static strength showed good agreement with the Tsai-Hill criterion. Relationships between the maximum principal stress σp1, max and number of cycles to failure Nf were approximately linear in the whole range of fatigue life. Normalizing σp1, max with the principal stress of static strength σp1, 0 gave S-N curves that depended on Vƒ, α and the molding processes. For unified evaluation of multi-axial fatigue life for GF/Phenol, non-dimensional effective stress σ* by the Tsai-Hill criterion was applied. Relationships between the σ* and N onto a double logarithmic chart was presented in the form of Basquin's exponential law without dependence on molding-process, Vƒ and α. The material constant n in Basquin's law showed a slope of σ*-N curves of S-series (n = 26.3) was equivalent to P-series (n = 27.0). It has been confirmed the multi-axial fatigue life of GF/Phenol could be predicted by using σ* with unique S-N curve.

Strain fluctuations from DIC technique applied on paper under fatigue or creep

We study the evolution of deformation on a quasi 2D paper sample during fatigue and creep experiments. Paper is a fibrous material, sensitive to various parameters (humidity, temperature, history effect). As for many materials, the lifetime varies a lot. Basquin's law claims that the number of cycles at break in fracture tests has a power-law dependence on the external load amplitude; Monkman-Grant relationship predicts that lifetime is proportional to the minimum strain rate during creep. The main question is therefore: is it possible to predict the time-dependent rupture? We perform creep and cyclic tests on paper samples. The main tools of investigation are acoustic emission (AE) -based analysis and digital image correlation (DIC). Via the AE, one can follow the damage evolution in samples, like microcrack formation that releases elastic energy. The DIC instead works well as a tool to measure at great accuracy both global and local deformation fields. From these, local strain rates can be derived, which then can be used to understand the microscopic dynamics that lie behind a certain rheology or sample response. The issue is to predict the break by looking at the sample-to-sample variation and by comparing experiments.

Comparison of low cycle fatigue of ductile cast irons with different matrix alloyed with nickel

Total strain controlled tests have been performed on cylindrical specimens of austempered ductile cast iron (ADI) and ductile cast iron with the ferritic matrix, both alloyed with 2.75% Ni, with the aim to compare cyclic plasticity and the fatigue life at temperatures 23 °C and–45 °C. Microstructure and its features are documented using light microscope (image analysis) and neutron diffraction. In ADI the measurement of retained austenite by neutron diffraction before and after fatigue tests is used to discuss the cyclic stress-strain response. Cyclic hardening/softening curves, cyclic stress-strain curves and fatigue life curves were obtained for both temperatures and materials. Cyclic stress-strain curve obtained at–45 °C is shifted to higher stress amplitudes relative to room temperature curve. The fatigue life curves at both temperatures can be well approximated by the Manson-Coffin and Basquin laws. The Manson-Coffin curves are identical for both materials and temperatures while the Basquin curve is shifted to longer fatigue life for ADI. The surface relief developed during fatigue was studied using SEM. Fatigue cracks initiated preferably from persistent slip markings at the interface of graphite nodule.