Simplified Thermal Stress Model to Predict Low Temperature Cracks in Flexible Pavement

2014 ◽  
Author(s):  
Md Rashadul Islam ◽  
Umme A. Mannan ◽  
Asma. Rahman ◽  
Rafiqul A. Tarefder
Keyword(s):  
Thermal Stress ◽  
Low Temperature ◽  
Flexible Pavement ◽  
Stress Model

scholarly journals Fatigue Resistance and Cracking Mechanism of Semi-Flexible Pavement Mixture

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5277
Author(s):  
Shiqi Wang ◽  
Huanyun Zhou ◽  
Xianhua Chen ◽  
Minghui Gong ◽  
Jinxiang Hong ◽  
...  
Keyword(s):  
Low Temperature ◽  
Fatigue Resistance ◽  
Stress Ratio ◽  
Asphalt Binder ◽  
Asphalt Mixture ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
The Poor ◽  
Grouting Material ◽  
Cracking Mechanism

Semi-flexible pavement (SFP) is widely used in recent years because of its good rutting resistance, but it is easy to crack under traffic loads. A large number of studies are aimed at improving its crack resistance. However, the understanding of its fatigue resistance and fatigue-cracking mechanism is limited. Therefore, the semi-circular bending (SCB) fatigue test is used to evaluate the fatigue resistance of the SFP mixture. SCB fatigue tests under different temperature values and stress ratio were used to characterize the fatigue life of the SFP mixture, and its laboratory fatigue prediction model was established. The distribution of various phases of the SFP mixture in the fracture surface was analyzed by digital image processing technology, and its fatigue cracking mechanism was analyzed. The results show that the SFP mixture has better fatigue resistance under low temperature and low stress ratio, while its fatigue resistance under other environmental and load conditions is worse than that of asphalt mixture. The main reason for the poor fatigue resistance of the SFP mixture is the poor deformation capacity and low strength of grouting materials. Furthermore, the performance difference between grouting material and the asphalt binder is large, which leads to the difference of fatigue cracking mechanism of the SFP mixture under different conditions. Under the fatigue load, the weak position of the SFP mixture at a low temperature is asphalt binder and its interface with other materials, while at medium and high temperatures, the weak position of the SFP mixture is inside the grouting material. The research provides a basis for the calculation of the service life of the SFP structure, provides a reference for the improvement direction of the SFP mixture composition and internal structure.

AYMA: Mechanistic Probabilistic System To Evaluate Flexible Pavement Performance

1998 ◽  
Vol 1629 (1) ◽  
pp. 137-148 ◽  
Author(s):  
Manuel Ayres ◽  
Matthew W. Witczak
Keyword(s):  
Low Temperature ◽  
Mechanistic Model ◽  
Permanent Deformation ◽  
Probabilistic Approach ◽  
Fatigue Cracking ◽  
Flexible Pavement ◽  
Analysis And Design ◽  
Mechanistic Approach ◽  
Low Temperature Cracking ◽  
User Friendly

A new rational mechanistic model for analysis and design of flexible pavement systems has been developed. Furthermore, a fundamental probabilistic approach was incorporated into this system to account for the uncertainty of material and environmental conditions. The system was integrated in a user-friendly Windows program with a variety of user-selected options that include widely used models and those recently developed in the Strategic Highway Research Program project. Three basic types of distress can be investigated separately or all together, including fatigue cracking, permanent deformation, and low-temperature cracking. The mechanistic approach makes use of the JULEA layered elastic analysis program to obtain pavement response. The system provides optional deterministic and probabilistic solutions, accounts for aging and temperature effects over the asphalt materials, variable interface friction, multiple wheel loads, and user-selected locations for analysis. Tabular and graphical results provide expected distress values for each month as well as their variability, probability of failure, and assessment of the overall reliability of the pavement relative to each type of distress for a user-selected failure criterion. Only the load-associated module of AYMA is presented; a separate work describes the low-temperature cracking analysis.

Structural Analysis and Optimization of Transition Section of Convex Tube Sheet

2016 ◽  
Vol 853 ◽  
pp. 356-360
Author(s):  
Zun Chao Liu ◽  
Ke Wang ◽  
Tong Liu ◽  
Wei Feng Xu ◽  
Min Shan Liu
Keyword(s):  
Thermal Stress ◽  
High Temperature ◽  
Low Temperature ◽  
Heat Recovery ◽  
Sheet Thickness ◽  
Heat Recovery Boiler ◽  
Tube Sheet ◽  
Section Thickness ◽  
Shell Side ◽  
Transition Section

The convex tube sheet which is used in heat recovery boiler consists of three parts: the high temperature tube sheet, the low temperature tube sheet and the transition section.Three-dimensional finite element model of convex tube sheet in new type of heat recovery boiler is established in this paper. Using the ANSYS Workbench software, thermal stress of the convex tube sheet is analyzed. The temperature fields and thermal stress distribution of convex tube sheet are obtained, and its structure strength is checked. The effects of the high temperature tube sheet thickness, low temperature tube sheet thickness and transition section thickness on the maximum equivalent stress of the convex tube sheet are analyzed. The results show that: temperature of most parts of convex tube sheet is close to the tube side fluid temperature, and the large temperature gradient only existed in the thinner regions of shell side of convex tube sheet; temperature distribution shows obvious skin effect. At the transition section, the temperature along the thickness direction is more evenly distributed, with little change in temperature gradient; larger thermal stress mainly concentrated at tube layout area which close to the shell side of the high temperature tube sheet and the connecting parts of transition section and low temperature tube sheet in the tube side. Through checking the strength intensity, convex tube sheet structural strength meets the requirements.The transition section thickness are optimized. The optimum thickness of the transition section analyzed in this paper is 31mm.

A Semianalytical Thermal Stress Model for the Czochralski Growth of Type III-V Compounds

2006 ◽  
Vol 66 (5) ◽  
pp. 1533-1562 ◽  
Author(s):  
C. Sean Bohun ◽  
Huaxiong Huang ◽  
Ian Frigaard ◽  
Shuqing Liang
Keyword(s):  
Thermal Stress ◽  
Stress Model ◽  
Czochralski Growth ◽  
Type Iii

scholarly journals Research on Crack Resistance of Semi-flexible Pavement Materials

2021 ◽  
Vol 248 ◽  
pp. 01020
Author(s):  
Wu Jiahong
Keyword(s):  
Low Temperature ◽  
Crack Resistance ◽  
Influencing Factors ◽  
Cement Mortar ◽  
Orthogonal Design ◽  
Flexible Pavement ◽  
Volume Stability ◽  
Pavement Materials ◽  
The Matrix ◽  
Matrix Porosity

Semi-flexible pavement has been widely used in China's road construction due to its excellent rutting resistance. Due to the large difference in volume stability between the matrix asphalt mixture and the cement mortar, the internal stress of the semi-flexible pavement material is concentrated and cracking is likely to occur. To explore the influence of different Influencing factors on the cracking resistance of semi-flexible pavement materials. This paper used the orthogonal design method to design the mix ratio of ordinary cement mortar. On this basis, admixtures (silica fume, ordinary emulsified asphalt, water-based epoxy resin) were added to prepare special cement mortar. Then, using cement mortar type, matrix porosity, matrix asphalt type, matrix aggregate type as the influencing factors, this article has studied his influence on the crack resistance of semi-flexible pavement materials. Tests show that cement mortar type, matrix porosity, matrix asphalt type, matrix aggregate type have varying degrees of influence on the crack resistance of semi-flexible pavement. The effect of matrix porosity on low temperature crack resistance is the greatest, followed by asphalt and cement mortar types, and the lowest by aggregate type. Enhancing the flexibility of cement mortar and enhancing the elastoplasticity of the matrix are conducive to improving the low-temperature performance of semi-flexible pavements.

Prediction of Low-Temperature Cracking of Asphalt Concrete Mixtures with Thermal Stress Restrained Specimen Test Results

1996 ◽  
Vol 1545 (1) ◽  
pp. 50-58 ◽  
Author(s):  
Hannele K. Zubeck ◽  
Ted S. Vinson
Keyword(s):  
Thermal Stress ◽  
Low Temperature ◽  
Asphalt Concrete ◽  
Probabilistic Model ◽  
Deterministic Model ◽  
Crack Spacing ◽  
Test Results ◽  
Concrete Mixtures ◽  
Specimen Test ◽  
Low Temperature Cracking

A deterministic model and a probabilistic model were developed to predict low-temperature crack spacing as a function of time using thermal stress restrained specimen test results, pavement thickness and bulk density, pavement restraint conditions, and air temperature. The effect of aging on pavement properties was incorporated in the models by predicting the field aging with long-term oven aging treatment in the laboratory. The calculation of the crack spacing is based on the theory that the pavement slab cracks when the pavement temperature reaches the cracking temperature of the mixture and the slab is fully restrained. The deterministic model predicts crack spacing with time, whereas the probabilistic model predicts crack spacing and its variation with time and yields the reliability of the design with regard to a minimum acceptable crack spacing criterion defined by road authorities. The probabilistic model is recommended for use in predicting the low-temperature cracking of asphalt concrete mixtures.

Initial development of millet with use of biostimulant under different temperatures

2020 ◽  
Vol 13 (2) ◽  
pp. 20
Author(s):  
P. R. Diesel ◽  
V. N. Silva
Keyword(s):  
Thermal Stress ◽  
Low Temperature ◽  
Seed Treatment ◽  
Stress Condition ◽  
Dry Mass ◽  
Negative Effects ◽  
Germination Test ◽  
Initial Development ◽  
Germination Speed ◽  
Different Temperatures

Millet is an important summer grass used as forage grass due to good bromatological characteristics and easy adaptation to Brazilian environmental conditions. However, when sowing the crop early in the southern region, situations may occur where low temperatures affect germination and seedling development. Thus, the present work had the objective of evaluating the germination and initial development of millet using Biozyme TF® biostimulant as a way to attenuate the effects of different temperatures. The experimental design was completely randomized, in a factorial scheme 3 x 5 (temperatures x doses) with four replicates each. The temperatures used were 15 °C, 20 °C and 25 °C and the doses used were: 0 (control); 0.25; 0.5; 0.75 and 1 ml kg-1. After the treatment, the seeds were evaluated by: germination test, germination speed index, shoot and root length and seedling dry mass. The data obtained were submitted to analysis of variance with Sisvar® software and, when found significant, the regression analysis was performed. The germination of millet seeds is favored, under low temperature stress conditions, with seed treatment at the dose of 0.50 ml kg-1 of biostimulant. The biostimulant does not influence millet germination speed index. Under low temperature thermal stress the biostimulant minimally increases the length and dry mass accumulation of millet seedlings and attenuates the negative effects on root growth. The accumulation of dry mass of the roots decreased with increasing dose of the biostimulant under thermal stress condition.

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