scholarly journals Experimental Investigation on Nonlinear Flow Anisotropy Behavior in Fracture Media

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Chun Zhu ◽  
Xiaoding Xu ◽  
Xiuting Wang ◽  
Feng Xiong ◽  
Zhigang Tao ◽  
...  
Keyword(s):  
Tensile Tests ◽  
Nonlinear Flow ◽  
Scanning System ◽  
Affine Surface ◽  
Proposed Model ◽  
Indirect Tensile ◽  
New Formula ◽  
Flow Anisotropy ◽  
Flow Experiments ◽  
Forchheimer’S Law

A series of flow experiments were performed on matched fractures to study the problem of non-Darcy flow in fractured media. Five rock fractures of different roughness were generated using indirect tensile tests, and their surface topographies were measured using a stereo topometric scanning system. The fracture was assumed to be a self-affine surface, and its roughness and anisotropy were quantified by the fractal dimension. According to the flow tortuosity effect, the nonlinear flow was characterized by hydraulic tortuosity and surface tortuosity power law relationships based on Forchheimer’s law. Fracture seepage experiments conducted with two injection directions (0° and 90°) showed that Forchheimer’s law described the nonlinear flow well. Both the proposed model and Chen’s double-parameter model gave similar results to the experiment, but the match was closer with the proposed model. On this basis, a new formula for the critical Reynolds number is proposed, which serves to distinguish linear flow and Forchheimer flow.

scholarly journals Optimizing Multi-Item EOQ when the Constraint of Annual Number of Orders is Active

2016 ◽  
Vol 11 (1) ◽  
pp. 55
Author(s):  
Karzan Mahdi Ghafour ◽  
Rezan Hama Rashid
Keyword(s):  
Economic Order Quantity ◽  
Annual Number ◽  
Order Quantity ◽  
Inventory Models ◽  
Lagrange Method ◽  
Left Hand ◽  
Side Condition ◽  
Proposed Model ◽  
The Right ◽  
New Formula

The responsibility in inventory models decides of how much or how many of inventory items to order. An economic order quantity (EOQ) differs from a model to another according to the assumptions and the variables. This paper has developed the EOQ in two deterministic inventory model (Purchases with shortage and production with shortage) of multi-item when the objective function is subjected to annual number of orders. The constraints are assumed to be active if the left hand side does not satisfy the right hand side condition. Thus, Lagrange method is used to find the new multi-item EOQ in each two models with the constraint to achieve the new formula of EOQ. Finally, a numerical example is provided to justify the proposed model.

scholarly journals Bond strength between stell-concrete and between concretes with different ages in structural rehabilitation

2015 ◽  
Vol 8 (5) ◽  
pp. 604-624
Author(s):  
M. R. DORIA ◽  
A. T. C SALES ◽  
N. F. de A. ANDRADE
Keyword(s):  
Bond Strength ◽  
Fresh Concrete ◽  
Tensile Tests ◽  
Bond Stress ◽  
Vertical Shear ◽  
Hardened Concrete ◽  
Pull Out ◽  
Steel Bar ◽  
Different Ages ◽  
Indirect Tensile

ABSTRACTIn inspections of buildings, it is common to find structures that, well before reaching its useful life longer require repairs and reinforcements. This study examined the bond strength between concrete of different ages and between steel and concrete, focusing on the recovery of reinforced concrete structures. To analyze the bond between concrete of different ages, trials with specimens receiving three different types of treatments at the interface between the concrete were performed: brushing; brushing and mortar equal to concrete of substrate and brushing and epoxy layer. Indirect tensile tests and oblique and vertical shear tests at the interface were made . The bond stress between steel and concrete was evaluated by pull out test under the conditions of the bar inserted in the still fresh concrete and when inserted in the hardened concrete with epoxy. Results showed increased bond strength by indirect tensile stress of 15% and 37%; 4% and 12% for the adherence test by oblique shear, and 108% and 178%, for the testing of vertical shear, respectively, for the specimens whose interfaces have received, in addition to brushing, layer of mortar and epoxy bridge, compared to those who received only brushing. Insignificant loss (about 0.52%) of bond stress was noticed for pull out test of steel bar when compared with test results of the specimens that had steel bar inserted in the concrete in the hardened state with epoxy adhesion bridge, with those who had inserted steel bar in fresh concrete.

scholarly journals Nonlinear Material Model for Quasi-Unidirectional Woven Composite Accounting for Viscoelastic, Viscous Deformation, and Stiffness Reduction

Polymers ◽  
2018 ◽  
Vol 10 (8) ◽  
pp. 903 ◽  
Author(s):  
Zhanyu Zhai ◽  
Bingyan Jiang ◽  
Dietmar Drummer
Keyword(s):  
Material Model ◽  
Tensile Tests ◽  
Experimental Results ◽  
Nonlinear Material ◽  
Weibull Function ◽  
Viscous Deformation ◽  
Stiffness Reduction ◽  
Viscoelastic Strain ◽  
Proposed Model ◽  
The Individual

To clarify the individual contribution of viscoelastic and viscous deformation to the global nonlinear response of composites, multilevel cyclic loading-unloading recovery tensile tests were carried out. The experimental results show that there is a linear relationship between the viscous strain and viscoelastic strain of composites, regardless of the off-axis angle or loading stress level. On the basis of experimental results, a coupled damage-plasticity constitutive model was proposed. In this model, the plasticity theory was adopted to assess the evolution of viscous strains. The viscoelastic strain was represented as a linear function of viscous strains. Moreover, the Weibull function of the effective stress was introduced to evaluate the damage variables in terms of stiffness reduction. The tensile stress-strain curves, predicted by the proposed model, showed a good agreement with experimental results.

scholarly journals Tensile Testing of Soils: History, Equipment and Methodologies

2020 ◽  
Vol 6 (3) ◽  
pp. 591-601
Author(s):  
Ausamah Al Houri ◽  
Ahed Habib ◽  
Ahmed Elzokra ◽  
Maan Habib
Keyword(s):  
Tensile Strength ◽  
State Of The Art ◽  
Retaining Walls ◽  
Tensile Tests ◽  
Testing Methods ◽  
Embankment Dams ◽  
Current State ◽  
Wide Range ◽  
Indirect Tensile ◽  
And Behavior

Tensile strength of soil is indeed one of the important parameters to many civil engineering applications. It is related to wide range of cracks specially in places such as slops, embankment dams, retaining walls or landfills. Despite of the fact that tensile strength is usually presumed to be zero or negligible, its effect on the erosion and cracks development in soil is significant. Thus, to study the tensile strength and behavior of soil several techniques and devices were introduced. These testing methods are classified into direct and indirect ways depending on the loading conditions. The direct techniques including c-shaped mold and 8-shaped mold are in general complicated tests and require high accuracy as they are based on applying a uniaxial tension load directly to the specimen. On the other hand, the indirect tensile tests such as the Brazilian, flexure beam, double punch and hollow cylinder tests provide easy ways to assess the tensile strength of soil under controlled conditions. Although there are many studies in this topic the current state of the art lack of a detailed article that reviews these methodologies. Therefore, this paper is intended to summarize and compare available tests for investigating the tensile behavior of soils.

scholarly journals Differences in the Ageing Behavior of Asphalt Pavements with Porous and Stone Mastic Asphalt Mixtures

2021 ◽  
pp. 036119812110322
Author(s):  
Ruxin Jing ◽  
Aikaterini Varveri ◽  
Xueyan Liu ◽  
Athanasios Scarpas ◽  
Sandra Erkens
Keyword(s):  
Asphalt Pavement ◽  
Tensile Tests ◽  
Asphalt Pavements ◽  
Porous Asphalt ◽  
Mastic Asphalt ◽  
Stone Mastic Asphalt ◽  
Aggregate Packing ◽  
Indirect Tensile ◽  
The Fourier Transform ◽  
Air Void

The degradation of bituminous materials as a result of ageing has a significant effect on asphalt pavement performance. In this study, one porous asphalt (PA) section and one stone mastic asphalt (SMA) asphalt pavement section were designed and constructed in 2014 and exposed to the actual environmental condition. To study the change in the pavement’s mechanical properties, asphalt cores were collected from both test sections annually. The change in stiffness modulus was determined via cyclic indirect tensile tests. To investigate the ageing behavior across the pavement depth, the bitumen was extracted and recovered from 13 mm slices along the depths of the cores. The chemical composition and rheological properties of the field-recovered bitumen, and that of original bitumen aged in standard short- and long-term ageing protocols, were investigated by means of the Fourier Transform Infrared (FTIR) spectrometer and Dynamic Shear Rheometer. The results show that the effect of mineral aggregate packing, and therefore of air-void distribution and connectivity, on the ageing sensitivity of the pavements with time was significant, as the changes in the stiffness of the PA mixture were greater than that of SMA mixture. In addition, the results of field-recovered bitumen show that there is an ageing gradient inside the porous asphalt layer, however, the ageing of SMA mainly happens on the surface of the layer. Finally, the field-recovered and laboratory-aged bitumen results demonstrate a weak relation between field and standard laboratory ageing protocols.

scholarly journals Modeling Framework for Capacity Analysis of Freeway Segments: Application to Ramp Weaves

2020 ◽  
Vol 2674 (1) ◽  
pp. 148-159
Author(s):  
Dezhong Xu ◽  
Nagui M. Rouphail ◽  
Behzad Aghdashi ◽  
Ishtiak Ahmed ◽  
Lily Elefteriadou
Keyword(s):  
Flow Speed ◽  
Segment Length ◽  
Estimation Model ◽  
Modeling Framework ◽  
Basic Segment ◽  
Proposed Model ◽  
Highly Sensitive ◽  
New Formula ◽  
Very High ◽  
New Framework

This research proposes a new modeling framework for the analysis of freeway segments. The framework provides a continuum from the operation of ramp weave segments to an equivalent basic segment serving the same traffic with the same number of lanes and free-flow speed. This approach distinguishes between congestion effects caused by high v/c ratios from turbulence caused by merging, diverging, and weaving traffic, thus greatly simplifying the model form, and its extensibility to other freeway segment types. The paper presents an application of this new framework to the analysis of ramp weaves, which were not sufficiently sampled in the development of the HCM6 methodology. The proposed model is shown to be superior to the HCM6 method both in relation to explaining field observations of speeds and in its simplicity in application. The results include a new formula for capacity estimation that is highly sensitive to segment length, and a speed estimation model that converges for low weaving volumes or at very high weaving segment lengths to that observed at a basic segment. Because the proposed model is calibrated with data mostly from North Carolina, it is recommended that data at additional sites be included in a larger calibration effort to ensure its applicability to a broader set of weaving segment configurations.

scholarly journals Multiphase-field modelling of crack propagation in geological materials and porous media with Drucker-Prager plasticity

2020 ◽  
Author(s):  
Michael Späth ◽  
Christoph Herrmann ◽  
Nishant Prajapati ◽  
Daniel Schneider ◽  
Felix Schwab ◽  
...  
Keyword(s):  
Crack Propagation ◽  
Tensile Tests ◽  
Plasticity Model ◽  
Two Phase ◽  
Ductile Materials ◽  
Pressure Sensitive ◽  
Plastic Materials ◽  
Proposed Model ◽  
Mechanical Jump Conditions ◽  
Plastic Components

Abstract A multiphase-field approach for elasto-plastic and anisotropic brittle crack propagation in geological systems consisting of different regions of brittle and ductile materials is presented and employed to computationally study crack propagation. Plastic deformation in elasto-plastic materials such as frictional, granular or porous materials is modelled with the pressure-sensitive Drucker-Prager plasticity model. This plasticity model is combined with a multiphase-field model fulfilling the mechanical jump conditions in diffuse solid-solid interfaces. The validity of the plasticity model with phase-inherent stress and strain fields is shown, in comparison with sharp interface finite element solutions. The proposed model is capable of simulating crack formation in heterogeneous multiphase systems comprising both purely elastic and inelastic phases. We investigate the influence of different material parameters on the crack propagation with tensile tests in single- and two-phase materials. To show the applicability of the model, crack propagation in a multiphase domain with brittle and elasto-plastic components is performed.

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