Effect of in-Plane Shear Modulus of Elasticity on Buckling Strength of Paperboard Plates

In previous research, a thin-plate theory was derived for analyzing corrugated fiberboard under edgewise compression and subjected to localized buckling. In this note, buckling formulas for thin paperboard plates characterized by an approximate in-plane shear modulus of elasticity are further generalized to allow for arbitrary levels of shear modulus. The results have applications in the design of paper products made of composite plates

Box Compression Analysis of World-Wide Data Spanning 46 Years

The state of the art among most industry citations of box compression estimation is the equation by McKee developed in 1963. Because of limitations in computing tools at the time the McKee equation was developed, the equation is a simplification, with many constraints, of a more general relationship. By applying the results of sophisticated finite element modeling, in this current study we derive a more general box compression formula that preserves the underlying theory of the McKee equation but removes the constraints. This formula is solvable with modern spreadsheet software, and we present an implementation method and example outputs as we relax or impose the various constraints. We analyze data obtained from multiple literature sources containing the traditional McKee equation inputs. We quantify the disparity between the McKee equation and the various sources of data and present an improved model for single-wall box-compression strength. The model attaches physical meaning to what were previously only fitting parameters, and it can serve as a tool for additional explorations in box optimization

Finite Element Corroboration of Buckling Phenomena Observed in Corrugated Boxes1

Conventional compression strength formulas for corrugated fiberboard boxes are limited to geometry and material that produce an elastic postbuckling failure.Inelastic postbuckling can occur in squatty boxes and trays, but a mechanistic rationale for unifying observed strength data is lacking. This study combines a finite element model with a parametric design of the geometry and material characteristics affecting the critical buckling stress of box panels to examine their postbuckling response. The finite element model enables a broad scope of simulated panels to be examined economically. Results lead to a postbuckling model fit to the predictions and a better understanding of how to unify elastic and inelastic failure data from actual experiments and form a more general box strength formula

Swept Sine Humidity Schedule for Testing Cycle Period Effects on Creep

The stacking life of corrugated containers under load decreases as relative humidity (RH) increases and when RH cycles, compared with when RH remains stable. Conventional RH test schedules that rely on fixed cycle periods do not adequately reflect the significance of moisture diffusion and hygroexpansion rate phenomena on the creep of corrugated containers and general wood fiber products. With cycle periods shorter than a critical period, materials are relatively unaffected by cyclic changes in RH. Longer periods amplify material hygroexpansion and accelerate creep. In this study, we propose a swept sine RH schedule in which the cycle frequency varies logarithmically with time and set forth equations for generating a numerical control signal. Data from creep tests of corrugated fiberboard reveal the frequency dependence of the amplitude and phase relationships between cyclic hygroexpansion and cyclic RH. A swept sine RH schedule yielded the continuous form of the response characteristics varying with cycle period that could not be acquired with multiple constant period schedules. The critical cycle period and the hygroexpansion response to moisture as a function of cycle period are proposed as criteria for discriminating among hygroexpansion-creep models

Buckling of Axially Loaded, Long Rectangular Paperboard Plates

This study examines the elastic buckling of long rectangular plates made of paper and subjected to compressive axial loading. The model is appropriate for the facing and flute components of corrugated fiberboard. A dimensionless stiffness, S, and mean Poisson's ratio, v, characterize the dimensions of the plate and the nonlinear orthotropic stress-strain relation of paper. The dimensionless buckling stress σ depends on S, v, and the plate edge condition, which can be fixed or simply supported. An examination of σ versus S predicts the stiffness needed to prevent elastic buckling and shows how the significance of edge restraint and material nonlinearity vary with S. An iterative solution is given for doing the analysis. Comparing the results obtained assuming fixed edges to those obtained assuming simply supported edges explains how fiberboard strength may vary due to component variations. Comparing the results obtained for nonlinear materials to those obtained for linear materials explains why fiberboard edgewise compressive strength cannot be accurately predicted from only the components' strengths

FE Analysis of Creep and Hygroexpansion Response of a Corrugated Fiberboarad to a Moisture Flow: a Transient Nonlinear Analysis

This paper presents a model using finite element method to study the response of a typical commercial corrugated fiberboard due to an induced moisture function at one side of the fiberboard. The model predicts how the moisture diffusion will permeate through the fiberboard's layers (medium and liners) providing information on moisture content at any given point throughout the structure. The hygroexpansion response and the creep response were predicted through the development of a finite element model capable of capturing the behavior of the fiberboard. Comparing the results generated from the model with actual experimental results validates the accuracy of the computational model. The model predicts the deformation response due to combined hygroexpansion and creep as the relative humidity rises from 38% RH to 86%. The parameters studied and calibrated include: the coefficient of moisture diffusion of the liner and the medium boards, the coefficient of moisture expansion, and the constants in the creep constitutive law. The results generated from the finite element model showed excellent agreement with the experimental results for a short column corrugated fiberboard and a board model representing a container box side-panel dimension. The results were generated in a cyclic relative humidity condition. A successful development of a reliable computational model holds the promise for analyzing collapse mechanism of container boxes in the service field under real weather condition data without dependency on expensive time-consuming experimental investigations. This is of great benefit to the shipping industry and the public

Variants at APOE influence risk of deep and lobar intracerebral hemorrhage

Objective Prior studies investigating the association between APOE alleles ε2/ε4 and risk of intracerebral hemorrhage (ICH) have been inconsistent and limited to small sample sizes, and did not account for confounding by population stratification or determine which genetic risk model was best applied. Methods We performed a large-scale genetic association study of 2189 ICH cases and 4041 controls from 7 cohorts, which were analyzed using additive models for ε2 and ε4. Results were subsequently meta-analyzed using a random effects model. A proportion of the individuals (322 cases, 357 controls) had available genome-wide data to adjust for population stratification. Results Alleles ε2 and ε4 were associated with lobar ICH at genome-wide significance levels (odds ratio [OR] = 1.82, 95% confidence interval [CI] = 1.50–2.23, p = 6.6 × 10 −10 ; and OR = 2.20, 95%CI = 1.85–2.63, p = 2.4 × 10 −11 , respectively). Restriction of analysis to definite/probable cerebral amyloid angiopathy ICH uncovered a stronger effect. Allele ε4 was also associated with increased risk for deep ICH (OR = 1.21, 95% CI = 1.08–1.36, p = 2.6 × 10 −4 ). Risk prediction evaluation identified the additive model as best for describing the effect of APOE genotypes. Interpretation APOE ε2 and ε4 are independent risk factors for lobar ICH, consistent with their known associations with amyloid biology. In addition, we present preliminary findings on a novel association between APOE ε4 and deep ICH. Finally, we demonstrate that an additive model for these APOE variants is superior to other forms of genetic risk modeling previously applied. ANN NEUROL 2010Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/78478/1/22134_ftp.pd

Comparison of 1.0 M gadobutrol and 0.5 M gadopentate dimeglumine-enhanced MRI in 471 patients with known or suspected renal lesions: Results of a multicenter, single-blind, interindividual, randomized clinical phase III trial

The purpose of this phase III clinical trial was to compare two different extracellular contrast agents, 1.0 M gadobutrol and 0.5 M gadopentate dimeglumine, for magnetic resonance imaging (MRI) in patients with known or suspected focal renal lesions. Using a multicenter, single-blind, interindividual, randomized study design, both contrast agents were compared in a total of 471 patients regarding their diagnostic accuracy, sensitivity, and specificity to correctly classify focal lesions of the kidney. To test for noninferiority the diagnostic accuracy rates for both contrast agents were compared with CT results based on a blinded reading. The average diagnostic accuracy across the three blinded readers ('average reader') was 83.7% for gadobutrol and 87.3% for gadopentate dimeglumine. The increase in accuracy from precontrast to combined precontrast and postcontrast MRI was 8.0% for gadobutrol and 6.9% for gadopentate dimeglumine. Sensitivity of the average reader was 85.2% for gadobutrol and 88.7% for gadopentate dimeglumine. Specificity of the average reader was 82.1% for gadobutrol and 86.1% for gadopentate dimeglumine. In conclusion, this study documents evidence for the noninferiority of a single i.v. bolus injection of 1.0 M gadobutrol compared with 0.5 M gadopentate dimeglumine in the diagnostic assessment of renal lesions with CE-MRI

Genetic Variants in CETP Increase Risk of Intracerebral Hemorrhage

OBJECTIVE: In observational epidemiologic studies, higher plasma high-density lipoprotein cholesterol (HDL-C) has been associated with increased risk of intracerebral hemorrhage (ICH). DNA sequence variants that decrease cholesteryl ester transfer protein (CETP) gene activity increase plasma HDL-C; as such, medicines that inhibit CETP and raise HDL-C are in clinical development. Here, we test the hypothesis that CETP DNA sequence variants associated with higher HDL-C also increase risk for ICH.METHODS: We performed 2 candidate-gene analyses of CETP. First, we tested individual CETP variants in a discovery cohort of 1,149 ICH cases and 1,238 controls from 3 studies, followed by replication in 1,625 cases and 1,845 controls from 5 studies. Second, we constructed a genetic risk score comprised of 7 independent variants at the CETP locus and tested this score for association with HDL-C as well as ICH risk.RESULTS: Twelve variants within CETP demonstrated nominal association with ICH, with the strongest association at the rs173539 locus (odds ratio [OR] = 1.25, standard error [SE] = 0.06, p = 6.0 × 10(-4) ) with no heterogeneity across studies (I(2) = 0%). This association was replicated in patients of European ancestry (p = 0.03). A genetic score of CETP variants found to increase HDL-C by ∼2.85mg/dl in the Global Lipids Genetics Consortium was strongly associated with ICH risk (OR = 1.86, SE = 0.13, p = 1.39 × 10(-6) ).INTERPRETATION: Genetic variants in CETP associated with increased HDL-C raise the risk of ICH. Given ongoing therapeutic development in CETP inhibition and other HDL-raising strategies, further exploration of potential adverse cerebrovascular outcomes may be warranted. Ann Neurol 2016;80:730-740