Estimation of Buckling and Ultimate Collapse Behaviour of Stiffened Curved Plates under Compressive Load

TAPPI test T811 is the specified method to ascertain ECT relative to box manufacturer’s certification compliance of corrugated fiberboard under Rule 41/ Alternate Item 222. T811 test sample heights were derived from typical board constructions at the time of the test method’s initial development. New, smaller flute sizes have since been developed, and the use of lighter weight boards has become more common. The T811 test method includes sample specifications for typical A-flute, B-flute, and C-flute singlewall (and doublewall and triplewall) structures, but not for newer thinner E-flute or F-flute structures. This research explores the relationship of ECT sample height to measured compressive load, in an effort to determine valid E-flute and F-flute ECT sample heights for use with the T811 method. Through this process, it identifies challenges present in our use of current ECT test methods as a measure of intrinsic compressive strength for smaller flute structures. The data does not support the use of TAPPI T 811 for ECT measurement for E and F flute structures, and demonstrates inconsistencies with current height specifi-cations for some lightweight B flute.

Download Full-text

Compressive behaviours of octet-truss lattices

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220913586 ◽

2020 ◽

Vol 234 (16) ◽

pp. 3257-3269 ◽

Cited By ~ 1

Author(s):

Yifan Li ◽

Huaiyuan Gu ◽

Martyn Pavier ◽

Harry Coules

Keyword(s):

Failure Modes ◽

Density Ratio ◽

Three Dimensional ◽

Compressive Load ◽

High Strength ◽

Detailed Comparison ◽

Compressive Response ◽

Beam Elements ◽

Structural Applications ◽

Octet Truss

Octet-truss lattice structures can be used for lightweight structural applications due to their high strength-to-density ratio. In this research, octet-truss lattice specimens were fabricated by stereolithography additive manufacturing with a photopolymer resin. The mechanical properties of this structure have been examined in three orthogonal orientations under the compressive load. Detailed comparison and description were carried out on deformation mechanisms and failure modes in different lattice orientations. Finite element models using both beam elements and three-dimensional solid elements were used to simulate the compressive response of this structure. Both the load reaction and collapse modes obtained in simulations were compared with test results. Our results indicate that three-dimensional continuum element models are required to accurately capture the behaviour of real trusses, taking into account the effects of finite-sized beams and joints.

Download Full-text

Numerical and Theoretical Study of Performance and Mechanical Behavior of PEM-FC Using Innovative Channel Geometrical Configurations

Applied Sciences ◽

10.3390/app11125597 ◽

2021 ◽

Vol 11 (12) ◽

pp. 5597

Author(s):

Hussein A. Z. AL-bonsrulah ◽

Mohammed J. Alshukri ◽

Ammar I. Alsabery ◽

Ishak Hashim

Keyword(s):

Fuel Cell ◽

Cross Section ◽

Rectangular Channel ◽

Compressive Load ◽

Proton Exchange ◽

Channel Cross Section ◽

Channel Height ◽

Cross Sectional ◽

Triangular Channel ◽

Higher Power

Proton exchange membrane fuel cell (PEM-FC) aggregation pressure causes extensive strains in cell segments. The compression of each segment takes place through the cell modeling method. In addition, a very heterogeneous compressive load is produced because of the recurrent channel rib design of the dipole plates, so that while high strains are provided below the rib, the domain continues in its initial uncompressed case under the ducts approximate to it. This leads to significant spatial variations in thermal and electrical connections and contact resistances (both in rib–GDL and membrane–GDL interfaces). Variations in heat, charge, and mass transfer rates within the GDL can affect the performance of the fuel cell (FC) and its lifetime. In this paper, two scenarios are considered to verify the performance and lifetime of the PEM-FC using different innovative channel geometries. The first scenario is conducted by adopting a constant channel height (H = 1 mm) for all the differently shaped channels studied. In contrast, the second scenario is conducted by taking a constant channel cross-sectional area (A = 1 mm2) for all the studied channels. Therefore, a computational fluid dynamics model (CFD) for a PEM fuel cell is formed through the assembly of FC to simulate the pressure variations inside it. The simulation results showed that a triangular cross-section channel provided the uniformity of the pressure distribution, with lower deformations and lower mechanical stresses. The analysis helped gain insights into the physical mechanisms that lead to the FC’s durability and identify important parameters under different conditions. The model shows that it can assume the intracellular pressure configuration toward durability and appearance containing limited experimental data. The results also proved that the better cell voltage occurs in the case of the rectangular channel cross-section, and therefore, higher power from the FC, although its durability is much lower compared to the durability of the triangular channel. The results also showed that the rectangular channel cross-section gave higher cell voltages, and therefore, higher power (0.63 W) from the fuel cell, although its durability is much lower compared to the durability of the triangular channel. Therefore, the triangular channel gives better performance compared to other innovative channels.

Download Full-text

Experimental and Numerical Analyses on the Buckling Characteristics of Woven Flax/Epoxy Laminated Composite Plate under Axial Compression

Polymers ◽

10.3390/polym13070995 ◽

2021 ◽

Vol 13 (7) ◽

pp. 995

Author(s):

Venkatachalam Gopalan ◽

Vimalanand Suthenthiraveerappa ◽

Jefferson Stanley David ◽

Jeyanthi Subramanian ◽

A. Raja Annamalai ◽

...

Keyword(s):

Environmental Sustainability ◽

Composite Plate ◽

Compressive Load ◽

Laminated Composite ◽

Green Composite ◽

Laminated Composite Plate ◽

Axial Compressive Load ◽

Number Of Layers ◽

Structural Applications ◽

Ply Orientation

The evolution of a sustainable green composite in various loadbearing structural applications tends to reduce pollution, which in turn enhances environmental sustainability. This work is an attempt to promote a sustainable green composite in buckling loadbearing structural applications. In order to use the green composite in various structural applications, the knowledge on its structural stability is a must. As the structural instability leads to the buckling of the composite structure when it is under an axial compressive load, the work on its buckling characteristics is important. In this work, the buckling characteristics of a woven flax/bio epoxy (WFBE) laminated composite plate are investigated experimentally and numerically when subjected to an axial compressive load. In order to accomplish the optimization study on the buckling characteristics of the composite plate among various structural criterions such as number of layers, the width of the plate and the ply orientation, the optimization tool “response surface methodology” (RSM) is used in this work. The validation of the developed finite element model in Analysis System (ANSYS) version 16 is carried out by comparing the critical buckling loads obtained from the experimental test and numerical simulation for three out of twenty samples. A comparison is then made between the numerical results obtained through ANSYS16 and the results generated using the regression equation. It is concluded that the buckling strength of the composite escalates with the number of layers, the change in width and the ply orientation. It is also noted that the weaving model of the fabric powers the buckling behavior of the composite. This work explores the feasibility of the use of the developed green composite in various buckling loadbearing structural applications. Due to the compromised buckling characteristics of the green composite with the synthetic composite, it has the capability of replacing many synthetic composites, which in turn enhances the sustainability of the environment.

Download Full-text

Downdrag Measurements on a 160-Ft Floating Pipe Test Pile in Marine Clay

Canadian Geotechnical Journal ◽

10.1139/t72-014 ◽

1972 ◽

Vol 9 (2) ◽

pp. 127-136 ◽

Cited By ~ 28

Author(s):

M. Bozozuk

Keyword(s):

Skin Friction ◽

Compressive Load ◽

Marine Clay ◽

Positive Skin ◽

Negative Skin Friction ◽

Pore Pressures ◽

Excess Pore Pressures ◽

Test Pile ◽

Excess Pore

Large negative skin friction loads were observed on a 160 ft (49 m) steel pipe test pile floating in marine clay. The test pile was driven, open-ended, on the centerline of a 30 ft (9 m) high granular approach fill on the Quebec Autoroute near Berthierville. Since the installation was made in 1966 the fill has settled 21 in. (53 cm), dragging the pile down with it. Negative skin friction acting along the upper surface of the pile was resisted by positive skin friction acting along the lower end as it penetrated the underlying clay. Under these conditions the pile compressed about [Formula: see text] (2 cm). Analysis of the axial strains indicated that a peak compressive load of 140 t developed at the inflection point between negative and positive skin friction 73 ft (22 m) below the top of the pile. Negative and positive skin friction acting on the upper surface of the pile exceeded the in situ shear strength and approached the drained strength of the soil where excess pore water pressures had dissipated. At the lower end where the positive excess pore pressures were high and relative movement between the pile and the soil was large, the positive skin friction approached the remoulded strength as measured with the field vane. Skin friction was increasing, however, as positive escess pore pressures dissipated.This paper shows that skin friction loads are related to the combination of (a) in situ horizontal effective stresses, (b) horizontal stresses due to embankment loads, and (c) horizontal stresses due to differential settlement of the fill.

Download Full-text

Characteristic Study of Briquette Cyanobacteria as Fuel in Chemical Looping Combustion with Hematite as Oxygen Carrier

Applied Sciences ◽

10.3390/app11104388 ◽

2021 ◽

Vol 11 (10) ◽

pp. 4388

Author(s):

Haifeng Zhang ◽

Laihong Shen ◽

Huijun Ge ◽

Hongcun Bai

Keyword(s):

Large Scale ◽

Oxygen Carrier ◽

Compressive Load ◽

Phosphorus Recovery ◽

Chemical Looping Combustion ◽

Chemical Looping ◽

Carbon Conversion ◽

Nitrogen And Phosphorus ◽

Liquid Products ◽

Lower Temperature

Due to the more and more serious cyanobacteria bloom problem, it is particularly urgent to find a technology suitable for large-scale disposal and the efficient recovery of abundant nitrogen and phosphorus resources in cyanobacteria. The combination of chemical looping combustion (CLC) and biomass densification technology is thought to be a promising utilization selection. Based on the experimental results, the mechanical strength and energy density of briquette cyanobacteria are evidently increased with the compressive load; whereas, 10% is the optimal moisture content in the densification process. A higher heating rate in TGA would result in the damage of the internal structure of the briquette cyanobacteria, which are conducive to the carbon conversion efficiency. The presence of a hematite oxygen carrier would enhance the carbon conversion and catalyzed crack liquid products. CO2 yield is increased 25 percent and CH4 yield is decreased 50 percent at 900 °C in the CLC process. In addition, the lower temperature and reduction atmosphere in CLC would result in a lower NO emission concentration. The reactivity and porous property of hematite OC in CLC also increased during 10 redox cycle experiments. The CLC process accelerates the generation of CaH2P2O7 and CaHPO4 in cyanobacteria ash, which is more conducive to phosphorus recovery.

Download Full-text

A novel synergistic multi-scale modeling framework to predict micro- and meso-scale damage behaviors of 2D triaxially braided composite

International Journal of Damage Mechanics ◽

10.1177/10567895211033974 ◽

2021 ◽

pp. 105678952110339

Author(s):

Hongyong Jiang ◽

Yiru Ren ◽

Qiduo Jin

Keyword(s):

Compressive Load ◽

Scale Model ◽

Modeling Framework ◽

Braided Composite ◽

Multi Scale ◽

Scale Modeling ◽

Bridge Model ◽

Multi Scale Modeling ◽

Transverse Damage ◽

Meso Scale

A novel synergistic multi-scale modeling framework with a coupling of micro- and meso-scale is proposed to predict damage behaviors of 2D-triaxially braided composite (2DTBC). Based on the Bridge model, the internal stress and micro damage of constituent materials are respectively coupled with the stress and damage of tow. The initial effective elastic properties of tow (IEEP) used as the predefined data are estimated by micro-mechanics models. Due to in-situ effects, stress concentration factor (SCF) is considered in the micro matrix, exhibiting progressive damage accumulation. Comparisons of IEEP and strengths between the Bridge and Chamis’ theory are conducted to validate the values of IEEP and SCF. Based on the representative volume element (RVE), the macro properties and damage modes of 2DTBC are predicted to be consistent with available experiments and meso-scale simulation. Both axial and transverse damage mechanisms of 2DTBC under tensile or compressive load are revealed. Micro fiber and matrix damage accumulations have significant effects on the meso-scale axial and transverse damage of tows due to multi-scale coupling effects. Different from existing meso-/multi-scale models, the proposed multi-scale model can capture a crucial phenomenon that the transverse damage of tow is vulnerable to micro fiber fracture. The proposed multi-scale framework provides a robust tool for future systematic studies on constituent materials level to larger-scale aeronautical materials.

Download Full-text

New Evaluation Procedure for Multi-Dimensional Mechanical Strains and Tangent Moduli of Breast Implants: IDEAL IMPLANT® Structured Breast Implant Compared to Silicone Gel Implants

Bioengineering ◽

10.3390/bioengineering6020043 ◽

2019 ◽

Vol 6 (2) ◽

pp. 43 ◽

Cited By ~ 1

Author(s):

Harold J. Brandon ◽

Larry S. Nichter ◽

Dwight D. Back

Keyword(s):

Breast Implant ◽

Capsular Contracture ◽

Compressive Load ◽

Evaluation Procedure ◽

Shape Stability ◽

Silicone Gel ◽

Tangent Moduli ◽

Compressive Loads ◽

Cohesive Gel ◽

The Ideal

The IDEAL IMPLANT® Structured Breast Implant is a dual lumen saline-filled implant with capsular contracture and deflation/rupture rates much lower than single-lumen silicone gel-filled implants. To better understand the implant’s mechanical properties and to provide a potential explanation for these eight-year clinical results, a novel approach to compressive load testing was employed. Multi-dimensional strains and tangent moduli, metrics describing the shape stability of the total implant, were derived from the experimental load and platen spacing data. The IDEAL IMPLANT was found to have projection, diametric, and areal strains that were generally less than silicone gel implants, and tangent moduli that were generally greater than silicone gel implants. Despite having a relatively inviscid saline fill, the IDEAL IMPLANT was found to be more shape stable compared to gel implants, which implies potentially less interaction with the capsule wall when the implant is subjected to compressive loads. Under compressive loads, the shape stability of a higher cross-link density, cohesive gel implant was unexpectedly found to be similar to or the same as a gel implant. In localized diametric compression testing, the IDEAL IMPLANT was found to have a palpability similar to a gel implant, but softer than a cohesive gel implant.

Download Full-text

Theory and Application of the Parallel-Plate Plastimeter. Part 2

Rubber Chemistry and Technology ◽

10.5254/1.3539469 ◽

1935 ◽

Vol 8 (4) ◽

pp. 587-596 ◽

Cited By ~ 3

Author(s):

J. R. Scott

Keyword(s):

Plastic Flow ◽

Parallel Plate ◽

Plastic Material ◽

Compressive Load ◽

Flow Equation ◽

Simple Type ◽

Plastic Properties ◽

Further Development ◽

Rubber Stock ◽

Existing Data

Abstract In Part I (loc. cit.) the behavior of a plastic material in the parallel-plate (Williams) plastimeter was studied, and an expression was deduced showing how the rate of decrease in thickness of the sample during compression depends on the volume of the sample, its plastic properties, the compressive load, and the thickness itself. Subsequently, observations were published which showed that the basic principle adopted in this study was incorrect in certain particulars. Peek (loc. cit.), using these observations as a basis, deduced a new expression for the rate of decrease in thickness, though this is too complex for convenient practical use, except in an approximate simplified form. It has now been shown that the expression deduced in Part I, in spite of the inaccurate basis used, is sufficiently near to the truth to render substantially correct the conclusions there stated concerning the plastic properties of unvulcanized rubber stocks. By adopting the more accurate basis used by Peek, moreover, expressions for the rate of decrease in thickness can be deduced for materials showing more complex types of plastic flow than that considered in Part I or by Peek; this had proved impossible by the method previously used. The expression obtained by Peek for the simple type of plastic flow, as well as those now deduced for the more complex types, can be expressed in a form that furnishes a simple and rapid method of examining and analyzing experimental results. As a result of the work described in this paper, it is thus possible to determine, from results obtained with the parallel-plate plastimeter, whether or not a material such as unvulcanized rubber stock exhibits any of the types of plastic flow represented in the general form by Equation 1, and, if so, to find the values of the plastic constants of the material. The procedure is similar to that described in Part I, and consists simply in comparing, by superposition, a set of standard curves drawn on transparent paper with the curve plotted from experimental data. This further development of the method of studying plastic properties by means of the parallel-plate plastimeter should greatly increase its utility as an instrument of research. It has not yet been possible to apply the new method to a systematic study of rubber stocks, but from an examination of existing data it appears that these stocks, tested at 90° C., agree approximately with various forms of the generalized plastic flow equation already referred to.

Download Full-text