scholarly journals Effective properties of an isotropic solid weakened by micro-cracks located at inter-granular boundaries

2021 ◽  
pp. 104647
Author(s):  
Joane Meynard ◽  
Marcelle Ibrahim ◽  
Arnaud Monnier ◽  
Michel Bornert ◽  
Etienne Castelier ◽  
...  
Keyword(s):  
Effective Properties ◽  
Isotropic Solid ◽  
Micro Cracks

Stochastic micromechanics-based investigations for the damage healing of unsaturated concrete using electrochemical deposition method

2020 ◽  
Vol 29 (9) ◽  
pp. 1361-1378 ◽  
Author(s):  
Q Chen ◽  
HH Zhu ◽  
JW Ju ◽  
HX Li ◽  
ZW Jiang ◽  
...  
Keyword(s):  
Electrochemical Deposition ◽  
Effective Properties ◽  
Healing Process ◽  
Deposition Method ◽  
Computationally Efficient ◽  
Concrete Material ◽  
Aspect Ratios ◽  
Micro Cracks ◽  
Electrochemical Deposition Method ◽  
Damage Healing

The (micro-) cracks or (micro-) voids will lead to the damage of concrete material. A stochastic micromechanical framework is proposed to investigate the damage healing of the unsaturated concrete with the electrochemical deposition method. Stochastic micromechanical representations are presented based on the material’s random microstructures. Differential scheme-based multilevel homogenization procedures are proposed to quantitatively predict the effective properties of the repaired concrete. The probability density functions are obtained for the material’s effective properties with an efficient stochastic simulation framework, which is composed of the univariate approximation for the multivariate function, Newton interpolations and Monte Carlo simulations. Numerical examples are employed to verify the proposed stochastic micromechanical framework, which indicates that the presented framework is computationally efficient and capable of describing the electrochemical deposition method healing process for the unsaturated concrete considering the material’s inherent randomness. Finally, the influences of the saturation degrees and the equivalent aspect ratios on the probabilistic behavior of the repaired concrete are discussed on the basis of the proposed models.

scholarly journals Additive manufacturing of Ti-alloy: Thermal analysis and assessment of properties

2020 ◽  
Vol 12 (6) ◽  
pp. 168781402093306
Author(s):  
Omer Keles ◽  
SZ Shuja ◽  
Bekir Sami Yilbas ◽  
H Al-Qahtani ◽  
G Hassan ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Large Scale ◽  
Effective Properties ◽  
Stress Fields ◽  
Bottom Surface ◽  
Solid Alloy ◽  
Ti Alloy ◽  
Experimental Conditions ◽  
Air Gaps ◽  
Micro Cracks

In this study, 3D printing of Ti6Al4V alloy is realized and the characteristics of the printed layer are examined. The morphological structures and metallurgical changes in the printed layer are assessed. Temperature and stress fields are simulated in line with the experimental conditions. Since the air gaps are present in between the loose alloy powders prior to the printing, the effective properties incorporating the air fraction are determined and the effective properties are used in the simulations. Thermal conductivity of the loose alloy powders with the presence of air gaps is determined by incorporating the virtual experimental technique. It is found that the printed layer is free from micro-cracks and large scale asperities; however, some small pores sites are observed because of the release of air around the loose powders during the printing. Microhardness of the printed surface is higher in the top surface of the printed layer than that of as-received solid alloy. In addition, the friction coefficient of the printed surface remains lower than that of the conventionally produced solid surface. The columnar structures are formed in the mid-section of the printed layer and slanted grains are developed in the region of the top and the bottom surface of the printed layer.

Mathematical Model of the Effective Properties of a Fiber Reinforced Composite with a Linearly Graded Transition Zone

2010 ◽  
Vol 38 (4) ◽  
pp. 286-307
Author(s):  
Carey F. Childers
Keyword(s):  
Mathematical Model ◽  
Transition Zone ◽  
Effective Properties ◽  
Local Stress ◽  
Stress And Strain ◽  
Fiber Reinforced ◽  
Strain Fields ◽  
Shear Moduli ◽  
Fiber Reinforced Composite ◽  
Reinforced Composite

Abstract Tires are fabricated using single ply fiber reinforced composite materials, which consist of a set of aligned stiff fibers of steel material embedded in a softer matrix of rubber material. The main goal is to develop a mathematical model to determine the local stress and strain fields for this isotropic fiber and matrix separated by a linearly graded transition zone. This model will then yield expressions for the internal stress and strain fields surrounding a single fiber. The fields will be obtained when radial, axial, and shear loads are applied. The composite is then homogenized to determine its effective mechanical properties—elastic moduli, Poisson ratios, and shear moduli. The model allows for analysis of how composites interact in order to design composites which gain full advantage of their properties.

Properties of Self-Compacting Cementitious Composite Materials Containing Cement Kiln Dust Powder

2020 ◽  
Vol 38 (6A) ◽  
pp. 879-886
Author(s):  
Ahmed S. Kadhim ◽  
Alaa A. Atiyah ◽  
Shakir A. Salih
Keyword(s):  
Composite Materials ◽  
Total Porosity ◽  
Cement Kiln Dust ◽  
Cement Kiln ◽  
Cementitious Composite ◽  
Cement Dust ◽  
Micro Cracks ◽  
Load Carrying ◽  
Sustainable Materials ◽  
Kiln Dust

This paper aims to investigate the influence of utilization micro cement kiln dust as a sustainable materials additive in order to reduce the voids and micro cracks in the cementitious mortar materials which cause a drastic reduction in the load carrying capacity of the element. Its therefore very important to decrease the pores and enhance the mechanical strength of the cementitious composite materials. In this article, the properties of self-compacting mortar containing micro cement dust additive was experimentally assessed. Micro cement dust powder was added to the self-compacting mortar in (1, 2, 3, 4 and 5 %) percentage by weight of cement to be used as cementitious sustainable materials. The experimental results indicated that the modification and enhancement of the workability of fresh mixture and the mechanical strengths of self-compacting mortar were increased as micro cement dust additives increases. Also; the water absorption and total porosity were decreased with increases of micro cement dust powder.

Temperature and Humidity Dependent Reliability Analysis of RGB LED Chips

2006 ◽  
Author(s):  
Jun-Xian Fu ◽  
Shukri Souri ◽  
James S. Harris
Keyword(s):  
Reliability Analysis ◽  
Printed Circuit Board ◽  
Light Emitting Diode ◽  
Circuit Board ◽  
Light Emitting ◽  
Printed Circuit ◽  
Root Cause ◽  
Micro Cracks ◽  
Temperature And Humidity

Abstract Temperature and humidity dependent reliability analysis was performed based on a case study involving an indicator printed-circuit board with surface-mounted multiple-die red, green and blue light-emitting diode chips. Reported intermittent failures were investigated and the root cause was attributed to a non-optimized reflow process that resulted in micro-cracks and delaminations within the molding resin of the chips.

Detection of Micro-Cracks in Electroluminescence Images of Photovoltaic Modules

2020 ◽  
Author(s):  
Natasha Mathias ◽  
Farheen Shaikh ◽  
Chirayu Thakur ◽  
Sweekrithi Shetty ◽  
Pratibha Dumane ◽  
...  
Keyword(s):  
Photovoltaic Modules ◽  
Micro Cracks

scholarly journals Effective Complex Properties for Three-Phase Elastic Fiber-Reinforced Composites with Different Unit Cells

Technologies ◽  
2021 ◽  
Vol 9 (1) ◽  
pp. 12
Author(s):  
Federico J. Sabina ◽  
Yoanh Espinosa-Almeyda ◽  
Raúl Guinovart-Díaz ◽  
Reinaldo Rodríguez-Ramos ◽  
Héctor Camacho-Montes
Keyword(s):  
Effective Properties ◽  
Elastic Fiber ◽  
Fiber Reinforced Composites ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Effective Coefficients ◽  
Three Phase ◽  
Out Of Plane ◽  
Local Problems ◽  
Unit Cells

The development of micromechanical models to predict the effective properties of multiphase composites is important for the design and optimization of new materials, as well as to improve our understanding about the structure–properties relationship. In this work, the two-scale asymptotic homogenization method (AHM) is implemented to calculate the out-of-plane effective complex-value properties of periodic three-phase elastic fiber-reinforced composites (FRCs) with parallelogram unit cells. Matrix and inclusions materials have complex-valued properties. Closed analytical expressions for the local problems and the out-of-plane shear effective coefficients are given. The solution of the homogenized local problems is found using potential theory. Numerical results are reported and comparisons with data reported in the literature are shown. Good agreements are obtained. In addition, the effects of fiber volume fractions and spatial fiber distribution on the complex effective elastic properties are analyzed. An analysis of the shear effective properties enhancement is also studied for three-phase FRCs.

scholarly journals Effect of Micro Solidification Crack on Mechanical Performance of Remote Laser Welded AA6063 Fillet Lap Joint in Automotive Battery Tray Construction

2021 ◽  
Vol 11 (10) ◽  
pp. 4522
Author(s):  
Tianzhu Sun ◽  
Pasquale Franciosa ◽  
Conghui Liu ◽  
Fabio Pierro ◽  
Darek Ceglarek
Keyword(s):  
Laser Welding ◽  
Fusion Zone ◽  
Aluminium Alloys ◽  
Mechanical Performance ◽  
Lap Joints ◽  
Fatigue Durability ◽  
Micro Cracks ◽  
Remote Laser Welding ◽  
Weld Fatigue ◽  
Weld Root

Remote laser welding (RLW) has shown a number of benefits of joining 6xxx aluminium alloys such as high processing speed and process flexibility. However, the crack susceptibility of 6xxx aluminium alloys during RLW process is still an open problem. This paper experimentally assesses the impact of transverse micro cracks on joint strength and fatigue durability in remote laser welding of AA6063-T6 fillet lap joints. Distribution and morphology of transverse micro cracks were acquired by scanning electron microscope (SEM) on cross-sections. Grain morphology in the weld zone was determined by electron backscatter diffraction (EBSD) while static tensile and dynamic fatigue tests were carried out to evaluate weld mechanical performance. Results revealed that increasing welding speed from 2 m/min to 6 m/min did not introduce additional transverse micro cracks. Additionally, welding at 2 m/min resulted in tensile strength improvement by 30% compared to 6 m/min due to the expansion of fusion zone, measured by the throat thickness, and refinement of columnar grains near fusion lines. Furthermore, the weld fatigue durability is significantly higher when fracture occurs in weld root instead of fusion zone. This can be achieved by increasing weld root angle with optimum weld fatigue durability at around 55°.

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