Goodman Model Research Articles

Experimental investigations of fractured rock deformation: A direct measurement method using strain gauges

Measuring fractured rock deformation under changing loading conditions is important in rock engineering projects to estimate rock strength and permeability. Measurement of deformations at less than micrometer level for rock fractures is difficult. To investigate the feasibility of the resistance strain gauge method, an experimental system was built to measure the fractured rock deformation due to cycling of confining pressure. The test results of different positions were compared and relatively reasonable test locations were selected based on the test data and regression analysis. The measurement tests were conducted on cylindrical samples with diameters of 50 mm and lengths of 100 mm of shale, granite, limestone, and marble containing a single fracture or two parallel fractures. The experimental results show that the strain gauge method and the proposed test point pattern perform well for measuring fractured rock deformation under changing loading conditions. The experimental data for the loading progress for a single fracture fits the existing fractured rock deformation models well (i.e., the Goodman model, Bandis model, and Sun model). For cyclic loading, observed cycles compared with the existing models and the hysteresis loop during deformation under cycling of the confining pressure, the strain-pressure curves of the loading and unloading processes are consistent with existing models. The strain gauge method provides a deformation measurement method of two parallel fractures. Under the pressure 15 MPa for plane α the deformation is in a state of opening with strain value more than 1003 με; but plane β is in a state of closure with strain value near −115 με.

Experimental Study on Interface Model of Asphalt Pavement under Vertical Load

Layered asphalt pavement makes the interlayer contact more complicated. In order to further understand the characteristics of interlayer interface of asphalt pavement under vehicle load, this paper analyzes the change rule of interlayer interface of asphalt pavement under a vertical load condition, based on the Goodman model. According to the characteristics of asphalt pavement, the experiment temperature, gradation, amount of viscosity-level oil, type of viscosity-level oil, and vertical compressive stress are taken as parameters, and the universal testing machine (UTM) and self-modified test fixture are used to carry out the direct interlayer shear test. Experimental results show that the vertical load has a significant effect on the characteristics of the interlayer interface. With an increase in the vertical load, the maximum bonding coefficient changes greatly. Additionally, when the vertical load is constant, the temperature and spreading amount of viscosity-level oil have a strong influence on the interlayer bonding state. With an increase in temperature, the maximum bonding coefficient decreases. The adhesion coefficient increases first and then decreases with increasing spreading amount. The best spreading amounts of oil between the upper and middle layers, the middle and lower layers, and the lower layer and cement-stabilized base layer under different vertical load conditions are recommended. This study offers important guidance for designing pavement structure.

Fatigue life assessment of vehicle coil spring using finite element analysis under random strain loads in time domain

PurposeThis paper aims to assess the fatigue life characteristics of vehicle coil spring under random strain load in the time domain. Cyclic random road loads caused fatigue failure for automotive components during their operating condition. .Design/methodology/approachThe coil spring model is developed through finite element analysis software. The critical region and fatigue life cycle of coil spring is evaluated through finite element analysis. The experimental is set up to capture the random strain signal of the rural, highway and campus road. The sampling rate of the random strain signals data captured were 500 Hz in 150 s. Then, fatigue life is assessed through Goodman, Brown-Miller, Fatemi-Socie, Wang-Brown fatigue life models. Goodman model is evaluated through finite element analysis in order to compare with fatigue experimental results.FindingsThe fatigue life was estimated for Brown-Miller model is the highest (4.32E4, 4.10E4, and 3.73E4 cycles/block for rural, highway and campus respectively) followed by Goodman model, Brown-Miller, Fatemi-Socie and Wang-Brown models respectively. The conservative fatigue life 1:2 and 2:1 data scattering approach is proposed in order to determine the acceptability of the data.Originality/valueHence, the proposed fatigue life models can be used to assess multiaxial fatigue under random strain signals for the automobile coil spring.

Analytical solution for the mechanical responses of transversely isotropic viscoelastic multi-layered asphalt pavement subjected to moving harmonic load

This work aims to develop a wave propagation-based analytical solution that can be effectively used for calculating the mechanical responses of transversely isotropic viscoelastic multi-layered asphalt pavement subjected to moving harmonic load. The material property can be considered transversely isotropic viscoelastic during the analytical solving. The interlayer conditions with different bonding levels are described by the Goodman model. The moving harmonic load is exerted on the surface of the multi-layered medium. The detailed implementation of the mathematical derivation (i.e., integral transforms, formulation of up-coming and down-going wave vectors) and the numerical program for the mechanical responses are presented. The proposed analytical solution is verified by finite element simulation and exhibits computational efficiency and accuracy. In addition, the effects of the load and material parameters on the mechanical responses of the multi-layered medium are investigated. Furthermore, the proposed analytical solution is extended to the study of tire–pavement interaction under random unevenness, and the random mechanical responses of the pavement under moving load with random amplitudes are obtained. In conclusion, the proposed analytical solution can be used as an effective tool for asphalt pavement design and analysis with consideration of the realistic load and material parameters.

Ratcheting Behavior of Sintered Copper Joints for Electronic Packaging

This study experimentally investigated the whole-life ratcheting behavior of sintered copper joints with consideration of the effects of stress rate, stress amplitude, mean stress, maximum stress, and stress ratio. Deformation of joints under cyclic load was measured by a noncontact displacement detecting system. In these joints, ratcheting strain and ratcheting strain rate were found to be sensitive to loading factors. For example, strain decreased as mean stress and stress amplitude decreased, and also as stress ratio and stress rate increased. Meanwhile, larger stress amplitude or mean stress reduced ratcheting fatigue life, while increasing stress ratio and stress rate increased fatigue life. The results indicate the modified Goodman model accounting for the effects of mean stress can usefully predict the ratcheting fatigue life of sintered copper joints at room temperature.

Crankshaft high cycle bending fatigue research based on the simulation of electromagnetic induction quenching and the mean stress effect

Electromagnetic induction quenching is one of the common surface strengthening approaches conducted engineering application, especially for the steel parts. In this paper, first a 3D finite element model was built and the electromagnetic thermal coupling simulation was used to determine the temperature field after quenching and coolant cooling process. Then the mechanical-thermal coupling simulation was used to obtain the residual stress field remaining in the crankshaft after air cooling. Finally the fatigue property of the treated crankshaft was predicted based on the residual stress and the different mean stress models. Validations between the predictions and the experimental results showed that the combination of the simulation and Goodman model can obtain the fatigue property of this type of crankshaft accurately, thus was suitable for actual engineering applications.

Enhancing fatigue strength of welded joints made of SBHS700 by hammer peening with ICR apparatus and HFMI treatment

This paper investigates the fatigue strength enhancement of two types of peening techniques: hammer peening with impact crack-closure retrofit apparatus and high-frequency mechanical impact (HFMI) treatment on out-of-plane gusset-welded joints made of SBHS700. In this work, fatigue tests were continuously carried out using plate specimens that were removed from a previously tested girder specimen. The results showed that the fatigue strength enhancement of these peening techniques on the welded joints was expected to be at least three classes higher compared with as-welded details with similar dimensions. Unexpectedly, the improvement effect of the hammer peening on one specimen was slightly lower than that of the other specimens. According to SEM observation, the cause of the slight reduction was that due to its weld shape, the distance between the crack initiation point and the treatment edge became greater than 2 mm. Finally, evaluations were performed on available data, including the test results from this study, based on an extended Modified Goodman model to estimate the fatigue limits of HFMI-treated joints. Consequently, the estimation results by the model indicated a good agreement with the fatigue strength enhancement of HFMI treatment and a possibility to be able to assess the enhancement of the hammer peening.

TIME EFFECT OF PILE-SOIL INTERACTION AND ITS ELASTIC-VISCOPLASTIC CONSTITUTIVE MODEL

Pile-soil interaction is considered to be one of the most important problems in the study of the mechanical behaviour of pile foundation. In this paper, the lateral friction resistance and pile-soil relative displacement of bridge piles in deep soft soils are monitored for an extended period by using concrete strain gauges that are embedded in the test pile. Field test results show that both the pile lateral frictional resistance and pile-soil relative displacement increase along with time, while the pile-soil interaction demonstrates a time effect. Therefore, an elastic-viscoplastic constitutive model must be established to better simulate the time-dependent mechanical behaviour of the pile-soil contact. Based on the Goodman model, we developed an elastic-viscoplastic interface constitutive model of the pile-soil interface into the FRIC subroutine through ABAQUS software, which is one of the most commonly used finite element analysis softwares in the world, to simulate a well-recorded pile test in deep soft soils. The calculated pile lateral frictional resistance and pile-soil relative displacement are close to the measured values, and the ability of the interface model to describe the changes in the shear stress-strain of the pile-soil interface along with time is validated.

Effect of Mean Stress on the Fatigue Life Prediction of Notched Fiber‐Reinforced 2060 Al‐Li Alloy Laminates under Spectrum Loading

This paper presents a study on the fatigue life prediction of notched fiber‐reinforced 2060 Al‐Li alloy laminates under spectrum loading by applying the constant life diagram. Firstly, a review on the state of the art of constant life diagram models for the life prediction of composite materials is given, which highlights the effect on the forecast accuracy. Then, the fatigue life of notched fiber‐reinforced Al‐Li alloy laminates (2/1 laminates and 3/2 laminates) is tested under cyclic stress, which has different stress cycle characteristics (constant amplitude loading and Mini‐Twist spectrum loading). The introduced models are successfully realized based on the available experimental data of examined laminates. In the case of Mini‐Twist spectrum loading, the effect of the constant life diagram on the life prediction accuracy of examined laminates is studied based on the rainflow‐counting method and Miner damage criteria. The results show that the simple Goodman model and piecewise linear model have certain advantages compared to other complex models for the life prediction of notched fiber metal laminates with different structures under Mini‐Twist loading. From the engineering perspective, the S‐N curve prediction based on the piecewise linear model is most applicable and accurate among all the models.

A Modified Walker Model Dealing with Mean Stress Effect in Fatigue Life Prediction for Aeroengine Disks

Mean stress effect plays an important role in fatigue life prediction, and it is discovered that maximum stress has nonnegligible influence on mean stress effect. Therefore, a modified Walker model is proposed to account for mean stress effect on fatigue life of aeroengine disks, which contains the influence of stress ratio and maximum stress on mean stress effect. Eight sets of fatigue data for standard smooth bars from six kinds of materials commonly used in aeroengine disks as well as two sets of experimental data from simulated specimens of turbine disks were employed to investigate the prediction capability of the proposed model against other candidate mean stress relationships. It is found that Goodman model generates most conservative results, while Morrow model overestimates fatigue life for most cases. SWT model yields similar results to Walker model but with less accuracy. The results of the modified Walker model turn out to be superior to those of any other candidate models for all cases examined, especially for large mean stress ones. Thus, the modified Walker model can be an effective method to predict fatigue lives of aeroengine disks influenced by mean stresses.

Da Formentini a Sala

The article retraces the last 20 years of direct mayoral election in Milan. It shows how the changes in institutional and electoral settings influenced both the party system and the voters' electoral responses. The first part of the article retraces the strategies of alliances and the choice of candidates made by the main coalitions. The second part estimates the flows of votes using the Goodman model. In order to quantify the mobility of Milanese electorate a typology of voters is proposed (stable, converted, absent, etc.). The third part analyses some indexes to assess the degree of bipolarism, fragmentation and personalisation of the city party system. In a context more and more volatile and tripolar, Milan is now one of the more bipolar city in Italy.

Fatigue life prediction of metal structures subjected to combined thermal-acoustic loadings using a new critical plane model

In this paper, the fatigue life of metallic structures under combined thermal-acoustic loadings is predicted based on critical plane model. In order to take into account the effect of mean stresses induced by temperature loading, a new critical plane model based on shear strain is proposed. The proposed model is validated with experimental data from literature through testing four metal materials under various strain paths with zero/non-zero mean stress. It has been shown that the results estimated by the proposed model agree well with the experiment. Furthermore, the proposed model is applied to predict the fatigue life of metal structures under combined thermal-acoustic loadings, and compared with the uniaxial Goodman model. The comparison indicates that the proposed model is conservative, and the thermal loading can significantly reduce the fatigue life.

Tracing the electorate of the MoVimento Cinque Stelle: an ecological inference analysis

The 2013 Italian parliamentary election was characterized by the outstanding performance of the MoVimento Cinque Stelle, which in its first participation in a general election obtained a remarkable 25% of the national vote. Where did these votes come from? Furthermore, is it possible to observe different electoral dynamics across geographical areas of Italy? In order to address these questions, we first estimate the flow of votes between the 2008 and 2013 general elections by applying an ecological inference method – the Goodman model – to the entire Italian voting population, and then we take a closer look at the differences in the four geopolitical areas in which Italy is traditionally divided. We find that the extraordinary performance of the MoVimento 5 Stelle was largely due to its capacity of attracting similar amounts of former Partito Democratico and Popolo della Libertà supporters, as well as a considerable amount of voters from their traditional allies: Lega Nord and Italia dei Valori. The MoVimento 5 Stelle was also able to mobilize previous non-voters. We shed light on the territorial features of these dynamics.

CUDA Optimization of Non-local Means Extended to Wrapped Gaussian Distributions for Interferometric Phase Denoising

Interferometric Synthetic Aperture Radar (InSAR) captures hundreds of millions of phase measurements with a single image, which can be differenced with a subsequent matching image to measure the Earth's physical properties such as atmosphere, topography, and ground instability. Each pixel in an InSAR image lies somewhere between perfect information and complete noise; deriving useful measurements from InSAR is therefore predicated upon estimating the quality (coherence) of each pixel, while also enhancing the information-bearing pixels through filtering. Rejecting noisy pixels at the outset and filtering the available information without introducing artifacts is crucial for generating accurate and spatially dense measurements. A capable filtering strategy must accommodate the diversity of manmade and natural ground cover exhibiting noise spawned by vegetation and water interwoven with useable signals echoed by infrastructure, rocks, and bare ground. Traditional filtering strategies assuming spatial homogeneity have lately been replaced by filters that honor discontinuities in ground cover, but two key improvements are needed: a) techniques must be adapted to enhance phase rather than amplitude, and b) runtime needs to be reduced to support deployment for operational land-information products. We present a new algorithm for wrapped phase filtering based on the non-local means algorithm (NLM) of Baudes et al. (2005) and the non-local InSAR (NL-InSAR) algorithm of Deledalle et al. (2011). The new filter, wrapped-NLM (WNLM), extends NLM to wrapped phase data that is inherently lossy due to an unknown integer number of phase ambiguities per pixel. The filter is similar to that of NL-InSAR in that we adopt their procedure of iteratively improving the filtered phase estimates by updating the Bayesian prior based on the previously filtered data (2009). Our filter differs from NL-INSAR in that it does not assume the Goodman model (1963) nor that of speckle noise (Goodman J. W., 2007) which were found to suffer in some areas due to having too many degrees of freedom; instead we use a more general assumption that the phase noise distribution is additive wrapped Gaussian, making the filter more robust to a larger variety of input data. This also simplifies the algorithm making it possible to implement an efficient parallel algorithm on the GPU using CUDA.

Cross-layer distributed power control: a repeated game formulation to improve the sum energy efficiency

The main objective of this work is to improve the energy-efficiency (EE) of a multiple access channel (MAC) system, through power control, in a distributed manner. In contrast with many existing works on energy-efficient power control, which ignore the possible presence of a queue at the transmitter, we consider a new generalized cross-layer EE metric. This approach is relevant when the transmitters have a non-zero energy cost even when the radiated power is zero and takes into account the presence of a finite packet buffer and packet arrival at the transmitter. As the Nash equilibrium (NE) is an energy-inefficient solution, the present work aims at overcoming this deficit by improving the global energy-efficiency. Indeed, as the considered system has multiple agencies each with their own interest, the performance metric reflecting the individual interest of each decision maker is the global energy-efficiency defined then as the sum over individual energy-efficiencies. Repeated games (RG) are investigated through the study of two dynamic games (finite RG and discounted RG), whose equilibrium is defined when introducing a new operating point (OP), Pareto-dominating the NE and relying only on individual channel state information (CSI). Accordingly, closed-form expressions of the minimum number of stages of the game for finite RG (FRG) and the maximum discount factor of the discounted RG (DRG) were established. The cross-layer model in the RG formulation leads to achieving a shorter minimum number of stages in the FRG even for higher number of users. In addition, the social welfare (sum of utilities) in the DRG decreases slightly with the cross-layer model when the number of users increases while it is reduced considerably with the Goodman model. Finally, we show that in real systems with random packet arrivals, the cross-layer power control algorithm outperforms the Goodman algorithm.

Health economic evaluations in orthodontics: a systematic review.

Economic evaluation is assuming increasing importance as an integral component of health services research. To conduct a systematic review of the literature and assess the evidence from studies presenting orthodontic treatment outcomes and the related costs. The literature review was conducted in four steps, according to Goodman's model, in order to identify all studies evaluating economic aspects of orthodontic interventions. The search covered the databases Medline, Cinahl, Cochrane, Embase, Google Scholar, National Health Service Economic Evaluation Database, and SCOPUS, for the period from 1966 to September 2014. The inclusion criteria were as follows: randomized controlled trials or controlled clinical trials comparing at least two different orthodontic interventions, evaluation of both economic and orthodontic outcomes, and study populations of all ages. The quality of each included study was assessed as limited, moderate, or high. The overall evidence was assessed according to the GRADE system (The Grading of Recommendations Assessment, Development and Evaluation). The applied terms for searches yielded 1838 studies, of which 989 were excluded as duplicates. Application of the inclusion and exclusion criteria identified 26 eligible studies for which the full-text versions were retrieved and scrutinized. At the final analysis, eight studies remained. Three studies were based on cost-effectiveness analyses and the other five on cost-minimization analysis. Two of the cost-minimization studies included a societal perspective, i.e. the sum of direct and indirect costs. The aims of most of the studies varied widely and of studies comparing equivalent treatment methods, few were of sufficiently high study quality. Thus, the literature to date provides an inadequate evidence base for economic aspects of orthodontic treatment. This systematic review disclosed that few orthodontic studies have presented both economic and clinical outcomes. There is currently insufficient evidence available about the health economics of orthodontic interventions. Further investigation is warranted.

Finite element analysis of deepwater conductor bearing capacity to analyze the subsea wellhead stability with consideration of contact interface models between pile and soil

Bearing capacity of deep-water conductor belongs to the research category of pile soil mutual interaction, which indicated that reasonable pile soil contact interface model is of great significance to calculate the bearing capacity correctly. In this paper, theoretical models have been established to calculate the lateral displacement and vertical bearing capacity. Two different pile and soil contact interface models are taken into consideration to calculate conductor lateral displacement and vertical bearing capacity using ABAQUS software by writing corresponding computer programs of constitutive model of interface model. The two different models calculating lateral displacement are contact mechanics model and contact element model. The two different models calculating vertical bearing capacity are coulomb friction model and Goodman element contact model. The results show that the lateral displacement calculated with the contact element method is greater than that calculated with contact mechanics model. However, the vertical bearing capacity calculated by Goodman model is greater than that calculated by the coulomb friction model. Moreover, the variation of vertical bearing capacity with jetted depth calculated by theoretical model, coulomb friction model and Goodman element contact model are different with one another. The variation of conductor lateral displacement with wellhead load and the variation of conductor vertical maximum bearing capacity with conductor size have also been figured out. In order to improve the subsea wellhead stability, the suggestion is calculating conductor bearing capacity with different contact models between pile and soil and take the minimum value as conductor design bases. The method introduced in this paper has a significant reference value to analyze the safety of subsea wellhead.

PROBABILISTIC FATIGUE DESIGN OF SHAFT FOR BENDING AND TORSION

The ever increasing demand for better and reliable mechanical systems necessitates the explicit consideration of reliability in the modeling and design of these systems. Design for reliability (DFR) has been receiving a great deal of attention for several years and companies are deploying resources to the design for reliability process because of the need to satisfy customers and reduce warranty costs. In traditional or deterministic design, safety or design factors are usually subjectively assigned in product design so as to assure reliability. But this method of design does not provide a logical basis for addressing uncertainties, so the level of reliability cannot be assessed quantitatively. This paper presents a probabilistic design approach for shafts under combined bending and torsional loads using the generalized Gerber fatigue failure rule. The design model parameters are considered as random variables characterized by mean values and coefficients of variation (covs). The coefficient of variation of the shaft design model is obtained by using first order Taylor series expansion for strength and stress in a stress-life fatigue design. A reliability factor is defined and related to the covs of design parameters and a failure probability. The design model assumes a lognormal probability density distribution for the parameters. This approach thus accounts for variability of design model parameters and provides quantitative assessment of product reliability. The approach is flow-charted for ease of application. This study shows that deterministic engineering models can be transformed into probabilistic models that can predict the risk in a design situation. From the design examples considered, it is shown that the popular modified Goodman model (MGM) for stresslife fatigue design is slightly on the conservative side. The study indicates possible reduction in component size and hence savings in product cost can be obtained through probabilistic design. Probabilistic design seems to be the most practical approach in product design due to the inherent variability associated with service loads, material properties, geometrical attributes, and mathematical design models. The computations in the present model were done using Microsoft Excel. This demonstrates that probabilistic design can be simplified so that specialized software and skills may not be required, especially at the preliminary design phase. Very often, available probabilistic models are intensive in numerical computation, requiring custom software and skilled personnel. The model approach presented needs to be explored for other design applications, so as to the make probabilistic design a common practice.

Statistic of a Gaussian beam from an arbitrary rough target in the single passage atmospheric turbulence

The extended Huygens-Fresnel principle and Goodman model was utilized for target surface to derive the mutual coherence function (MCF) of a Gaussian beam reflected from an arbitrary rough target in atmospheric turbulence. According to the MCF, expressions of the mean irradiance and average speckle size at the receiver were obtained. The analysis indicated that the mean intensity is closely related to the ratio of root mean square (rms) height to the lateral correlation length. In addition, the speckle size at the receiver is associated with turbulence strength, propagation distance and roughness of the target. The results can be reduced to the result of a Gaussian beam illuminating rough target and scattering from a target in free space.

Reliability comparison between SAC305 joint and sintered nanosilver joint at high temperatures for power electronic packaging

Ratcheting behavior of sintered nanosilver joints was examined by cyclic shearing tests at different temperatures. Fatigue lives of sintered nanosilver joints were compared with those of soldered SAC305 joints. An improved non-contact displacement detecting system combining infrared heating was developed to measure the deformation of the joints. Effects of temperature, mean stress, and stress amplitude on the ratcheting behavior of both kinds of the joints were analyzed. Shear strength of the sintered nanosilver joints is larger than that of the soldered SAC305 ones. The ratcheting displacement and its rate in both kinds of the joints increase with increase in temperature, mean stress, and stress amplitude. The fatigue life of sintered nanosilver joint is much longer than that of soldered SAC305 one under the same loading conditions. It is concluded that sintered nonosilver joint has demonstrated a longer fatigue life and better response to shearing and cyclic loading than SAC305 joint, especially at high temperatures. An improved temperature-dependent modified Goodman model is proposed and is proved to be able to accurately predict the fatigue life of the sintered nanosilver joints and the soldered SAC305 joints by introducing the temperature-dependent fatigue strength exponent and the fatigue strength coefficient.