Test and Calculation Model of Thermal Conductivity of Concrete

In order to study the influence of water content and hydration degree on the thermal conductivity of concrete, based on the steady-state plate method, the influence of water content, temperature, hydration degree and other factors on the thermal conductivity of early concrete was studied, and the calculation model of thermal conductivity of early concrete was established according to the test results and influence rules. The results show that there is a linear relationship between the thermal conductivity and water content at 28d, the higher the hydration degree is, the lower the thermal conductivity of concrete is; the difference between the measured value and the calculated model value is small, and the calculation formula can meet the requirements of engineering calculation.

Download Full-text

Influence of Strength Attenuation for Silt Soil on the Fatigue Life of Semi-Rigid Base

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.353-356.120 ◽

2013 ◽

Vol 353-356 ◽

pp. 120-124

Author(s):

Xiao Ming Yi ◽

Song Gen Wang ◽

Xiu Guang Song ◽

Zhen Qing Liu

Keyword(s):

Fatigue Life ◽

Water Content ◽

Yellow River ◽

Asphalt Pavement ◽

Rigid Base ◽

Influence Of Water ◽

Design Value ◽

The Difference ◽

Early Damage ◽

Resilience Modulus

Influence of water content on the resilience modulus for silt soil in Yellow River alluvial plane is studied by laboratory tests. And its found that resilience modulus decrease dramatically when the water content exceeds the optimum. So the subgrade cant support the pavement structure enough, which could make the fatigue life of semi-rigid base little than the design value. Basing on the distribution of the water content in real, the silt subgrade is divided into three parts in accordance with the difference of resilience modulus. Then, the tensile stress and fatigue life of semi-rigid base is gotten, and results show the strength decay of subgrade reduced the fatigue life of semi-rigid base up to 50%, which exposes the causes of early damage of semi-rigid base asphalt pavement on silt subgrade.

Download Full-text

Study on the Dynamic Response of Gravel Soil Low Embankment under a Long-Time Dynamic Loading Based on Model Test

Advances in Materials Science and Engineering ◽

10.1155/2021/6668028 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Dapeng Liu ◽

Jing Wang ◽

Feng Du

Keyword(s):

Water Content ◽

Dynamic Loading ◽

Dynamic Stress ◽

Calculation Model ◽

Strain Accumulation ◽

Test Results ◽

Desert Area ◽

Time Dynamic ◽

Gravel Soil ◽

Long Time

The low embankment is an important technique for road development in subgrade engineering due to its small fill height and applicability to the natural landscape in the oasis desert area of Xinjiang, China. A reasonable development of the gravel soil low embankment design requires the study of its dynamic response under a long-time dynamic loading. In the paper, a 1 : 1 full-scale low embankment model was established and tests of 100000 loading cycles with 50 kN peak value were carried out, taking into account three kinds of foundation moisture contents: 18%, 23%, and 28%. The test results show that the dynamic stress in the gravel soil low embankment attenuates nonlinearly with the increase in depth. The dynamic stress at each depth is the smallest for the water content value of 28% in the foundation. The stress attenuation rate is inversely proportional to the loading cycles and directly proportional to the water content of the foundation. The dynamic stress and dynamic strain in the gravel soil low embankment show cumulative effects with an increase of the loading cycles. The rate of stress and strain accumulation is faster for low loading cycles. The strain accumulation effect of each structural layer in the foundation is the largest for the water content value of 28%. The strain accumulation rate at the top layer of the foundation reaches 2.648. Based on the model test results, the dynamic stress calculation model for the gravel soil low embankment under dynamic loading is proposed. The calculation model was experimentally verified. The research results are important for the application of gravel soil low embankment in the oasis desert area of Xinjiang, China.

Download Full-text

Effect of steam autoclaving on laser sintered polyamide 12

Rapid Prototyping Journal ◽

10.1108/rpj-11-2019-0288 ◽

2020 ◽

Vol ahead-of-print (ahead-of-print) ◽

Author(s):

James Robert Wingham ◽

Maha Omran ◽

Joanna Shepherd ◽

Candice Majewski

Keyword(s):

Mechanical Properties ◽

Water Content ◽

Elongation At Break ◽

Content Type ◽

Polyamide 12 ◽

Root Cause ◽

Medical Sector ◽

Influence Of Water ◽

The Difference ◽

Direct Use

Purpose The use of laser sintering (LS) in the medical sector has increased dramatically in recent years. With the move towards direct use of these parts in clinical applications, there is a greater need to understand the effects of standard processes on the part properties. The purpose of this study is to determine the effect that steam sterilisation has on the mechanical properties of LS polyamide 12 parts. Design/methodology/approach The research presented here focusses on the effect of a single steam sterilisation cycle on the mechanical properties of polyamide 12 parts manufactured using LS. The influence of water content on the properties was investigated, with additional drying steps trialled to establish the potential to reverse any changes observed and to determine their root cause. Findings The results show that steam sterilisation has a significant effect on the mechanical properties of LS polyamide 12 parts, with a 39% reduction in elastic modulus, a 13% decrease in ultimate tensile strength and a 64% increase in the elongation at break. These properties were also all found to correlate with the water content, suggesting that this was the cause of the difference. The original properties of the parts were able to be recovered after oven drying. Practical implications These results show that with an additional drying step, LS polyamide 12 parts can be steam sterilised with no effect on the mechanical properties. Originality/value This is believed to be the first investigation into the effects of steam sterilisation in isolation on LS polyamide 12 parts, the first instance of drying parts to recover mechanical properties and the first instance of multiple water content measurements being directly linked to the mechanical properties.

Download Full-text

The influence of water content on thermal conductivity of paper used as transformer windings insulation

2012 IEEE 10th International Conference on the Properties and Applications of Dielectric Materials ◽

10.1109/icpadm.2012.6318991 ◽

2012 ◽

Cited By ~ 11

Author(s):

R. Lopatkiewicz ◽

Z. Nadolny ◽

P. Przybylek

Keyword(s):

Thermal Conductivity ◽

Water Content ◽

Influence Of Water

Download Full-text

Full-Scale Dynamometer Test of Composite Railway Brake Shoes – Study on the Effect of the Reinforcing Fibre Type

Acta Mechanica et Automatica ◽

10.2478/ama-2018-0031 ◽

2018 ◽

Vol 12 (3) ◽

pp. 204-208 ◽

Cited By ~ 1

Author(s):

Piotr Wasilewski

Keyword(s):

Thermal Conductivity ◽

Glass Fibre ◽

Steel Fibre ◽

Friction Material ◽

Full Scale ◽

Test Results ◽

Friction Materials ◽

Average Temperature ◽

The Difference ◽

Dynamometer Test

Abstract When designing or developing friction materials, it is crucial to predict how the modification of the formulation will affect their properties. Fibres are introduced in the composition of the phenolic-based brake friction materials to improve their mechanical strength. Apart from reinforcing the composite, fibres can also affect its tribological and thermophysical properties. In this study two composite friction materials are compared. The difference between the materials was the type of reinforcing fibre used in the formulation – in one case it was glass fibre, in the other steel fibre. Thermal diffusivity of both materials was measured and thermal conductivity was calculated. Frictional characteristics determined by means of full-scale dynamometer tests are analysed and discussed. Substitution of glass fibre with steel fibre led to increase in the friction coefficient. Maximum average temperature below wheel surface, observed during the test of the material containing steel fibre, was lower as compared to the test results of the material with glass fibre in its formulation, despite higher heat flux in the course of brake applications. Thermal conductivity of the friction material was enhanced by including steel fibre in the formulation.

Download Full-text