Moisture-Dependent Some Engineering Properties of Soybean Grains

This study was carried out to evaluate the effect of moisture content on some physical properties and mechanical behaviour under compression load of soybean grains. Four levels of moisture content ranging from 6.92 to 21.19% d.b. were used. The average length, width, thickness, arithmetic and geometric mean diameter, surface area, thousand grains mass and angle of repose increased as the moisture content increased from 6.92 to 21.19%. As the moisture content increased from 6.92 to 21.19% d.b., the bulk density and true density were found to decrease from 650.95 to 625.36 kg/m3 and 1147.86 to 1126.43 kg/m3 respectively, while the porosity was found to increase from 43.29 to 44.48%. The static coefficient of friction of soybean increased linearly against various surfaces as the moisture content increased from 6.92 to 21.19% d.b. The rupture energy of the grains increased in magnitude with an increase in moisture content, while rupture force decreased

Interlaminar Shear Properties of Bamboo Composite for Structural Applications

Interlaminar shear strength in bamboo composite (BC) is mainly provided by epoxy resin as the matrix in BC. This may greatly change due to humidity. This study aims at evaluating the shear strength of BC by testing and developing probabilistic relationships. The interlaminar shear strength of bamboo composite (BC) in different moisture conditions was tested according to ASTM D2344. The results show that the maximum shear stress does not generally occur at the centroid of samples, which could be associated with imperfections in BC layers. An extreme value theory-based model is suggested to evaluate the probability of shear failure in BC samples. The shear capacity decreased from 20.4 MPa to 14 MPa as the humidity increased from 60% to 90%. A summary of findings is as follows: It was found that under transient moisture conditions, local failure is likely to happen before the first significant crack occurs. Local failure is suggested to be considered in the design for serviceability. Stress drop caused by the local failure could exceed 10% of total shear strength and, therefore, should be regarded as a serviceability design. The probabilistic model developed in this study could be used for developing structural design safety factors

Precision spray modeling using image processing and artificial neural network

This study employed artificial neural network method for predicting the sprayer drift under different conditions using image processing technique. A wind tunnel was used for providing air flow in different velocities. Water Sensitive Paper (WSP) was used to absorb spray droplets and an automatic algorithm processed the images of WSPs for measuring droplet properties including volume median diameter (Dv0.5) and Surface Coverage Percent (SCP). Four Levenberg-Marqurdt models were developed to correlate the sprayer drift (output parameter) to the input parameters (height, pressure, wind velocity and Dv0.5). The ANN models were capable of predicting the output variables in different conditions of spraying with a high performance. Both models predicted the output variables with R2 values higher than 0.96 indicating the accuracy of the selected networks. Therefore, the developed predictor models can be used in precision agriculture for decreasing spray costs and losses and also environmental contamination

Design, construction and evaluation of a sprayer drift measurement system

Spray drift study for reducing environmental hazards and protecting crops is of high importance as the pesticides used today are more active and many are non-selective. Drift potential can be restricted by assessing and optimizing equipment design, application parameters, the liquid spray properties, type of formulation and environmental conditions. The aim of this research was to design, construct and assess an intelligent system to determine the level of the spraying drift. The main parts of the system were liquid supply mechanism, pipes and nozzles, a controlled pneumatic system to pressurize the liquid, a nozzle moving system with a controlling panel and a tunnel for wind providing and control. To assess the performance of sprayer and drift of droplets, water sensitive papers were placed in different distances from the nozzle considering different environmental conditions including: wind speed, spraying pressure and height. The evaluation results showed that the drift was increased with increasing of sparing pressure and nozzle height.

Interlaminar Shear Properties of Bamboo Composite for Structural Applications

Interlaminar shear strength in bamboo composite (BC) is mainly provided by epoxy resin as the matrix in BC. This may greatly change due to humidity. This study aims at evaluating the shear strength of BC by testing and developing probabilistic relationships. The interlaminar shear strength of bamboo composite (BC) in different moisture conditions was tested according to ASTM D2344. The results show that the maximum shear stress does not generally occur at the centroid of samples, which could be associated with imperfections in BC layers. An extreme value theory-based model is suggested to evaluate the probability of shear failure in BC samples. The shear capacity decreased from 20.4 MPa to 14 MPa as the humidity increased from 60% to 90%. A summary of findings is as follows: It was found that under transient moisture conditions, local failure is likely to happen before the first significant crack occurs. Local failure is suggested to be considered in the design for serviceability. Stress drop caused by the local failure could exceed 10% of total shear strength and, therefore, should be regarded as a serviceability design. The probabilistic model developed in this study could be used for developing structural design safety factors

Effects of Ca, K and water table depth on tomato mechanical properties

Two series of tests were performed in summer 1993 and repeated in summer 1994 to investigate effects of potassium, calcium and water table depth on mechanical properties of tomato fruit. In the first group of tests five mechanical properties stress, strain, ER (ratio of stress to strain at break), energy and toughness were calculated from the force-deformation curve obtained by compression of pericarp disks taken from tomato fruits (cv New Yorker) at the breaker stage. In the second group of tests force, deformation and energy were obtained from puncture tests on whole tomato fruit. The textural parameters were used to compare the effects of the potassium, calcium and water level depths on the mechanical properties of tomatoes. Results showed the effects of calcium and water table depths on the mechanical properties were significant. Tomato fruits exposed to increasing moisture stress levels by increasing water table depth exhibited increased firmness. Increased application of calcium also resulted in increased firmness. Application of different potassium levels had in general no significant effect on breaking stress, strain, ER, energy and toughness of tomato fruit pericarp.A new method of measuring skin strength of tomatoes is described. The method, refered to as loop method, overcame the problems with the existing method using mechanical grips. Further, the loop method was applied to measure the effect of potassium and calcium on skin strength of tomato. Using the loop method, data were collected on relaxation of tomato skin (epidermis). A computer program was written to model th tensile stress relaxation behaviour of tomato skin. The program was employed to calculate linear and non-linear coefficients of a relaxation model. The fitted values were in a very good agreement with experimental data (R$sp2>$0.99)

Service life prediction of corrosion pitted pipes

Research Doctorate - Doctor of Philosophy (PhD)In this study a Linear Elastic Fracture Mechanics (LEFM) based model is used to estimate the service life of pipes affected by corrosion pitting and influenced by Hydrogen-Assisted Fatigue Cracking. The main idea of the model can be summarised as follows. Firstly, the likely cracking patterns of a hydrogen affected pipe are estimated using the cracking pattern in the equivalent unaffected pipe. Secondly, the failure state of a pitted pipe is defined, based on the state of crack development from the pits. In the third step, the rate of cracking under HA-FC is estimated by reducing the material fracture toughness due to hydrogen diffusion from the crack front. Finally, having available the rate of crack development from the previous step, the location of the crack front is estimated under a HA-FC mechanism and the time required to reach the failure state is estimated. This methodology is novel and is employed herein to predict the service life of pitted brittle material pipes such as cast iron pipes. These are the main focus of this study since they have been used widely in water industry networks. For example, it is estimated that cast iron pipes account for more than 60% of the water mains in UK. In spite of a considerable number of reports on failure of cast iron pipes rigorous approaches to estimating the service life of such pipes have only recently become of research interest. It is anticipated that the present study will contribute to that work. In the last chapter numerical modelling of pipes under increasing axial load and constant internal pressure when there is corrosion pits on the exterior surface of the pipe is reported. It is shown that for the assumed ideal elastic-plastic material the shape and volume of the plastic field depend on pit depth and its geometry. Pipe wall fracture around a pit can be associated with a critical plastic section. The results reported herein should be relevant for estimating of the risk of perforation and of loss of contents for steel pipes under different loading which eventually can be used to estimate the service life time of the corrosion pitted pipes

A numerical study of damage caused by combined pitting corrosion and axial stress in steel pipes

Localized pipe wall damage accounts for many failures. Numerical modelling of pipes under increasing axial load and constant internal pressure when there is corrosion pits on the exterior surface of the pipe is reported herein. It is shown that for the assumed ideal elastic–plastic material the shape and volume of the plastic field depend on pit depth and its geometry. Pipe wall fracture around a pit can be associated with a critical plastic section. The results reported herein should be relevant for estimating of the risk of perforation and of loss of contents for steel pipes under different loading

Failure prediction of pitted brittle metal pipes

Numerical modelling is used to trace the development of cracks starting from pits that from on the surface of corroded, brittle metal pipe. Under internal pressure applied to the pipe, two general cracking patterns are found to occur and these are related to pit shape. The numerical analysis used allows estimation of the area of the cracked region and of the pressure under which failure occurs. These results also facilitate Stress Corrosion Cracking (SCC) studies by estimating the critical area of the crack stemming from a pit. This may result in a more realistic approach to estimating the likelihood of occurrence of critical cracks in brittle pitting corroded pipes

Service life of pitted pipes subject to pressure fluctuations and hydrogen embrittlement

For estimating the likely service life of brittle material pipes with exterior corrosion pits and subject to hydrogen embrittlement crack propagation from the pits is of interest. Similarity of pattern of fatigue cracking from these pits under pressure fluctuations to that under monotonically increasing pressure is referred to. This similarity permits the effect of hydrogen on the cracking rate to be formulated. The depth of cracks initiated from surface pits is estimated as a function of pipe service time, based on the proposed formulation for Hydrogen-Assisted Fatigue Cracking