Root Hole Research Articles

Design and Experiment of Dry-Farming Cantaloupe Transplanter under Water

To solve the problems of high temperature and drought in the Xinjiang Turpan area and the low survival rate of melon seedlings transplanted into dry soil, existing transplanters for large plant type young melon seedlings can be mechanized. For non-destructive planting for small plant types, such as Hami melon seedlings, there are still poor transplanting effects, planting point precise pile-soil, and other problems. In this study, a water transplanter for laying pipe and film for Hami melons was designed to mechanize the operation of rotating tillage, laying film and covering soil, transplanting potted seedlings on film, and water injection of the seedling root and planting hole, and soil piling and suppression. In this study, a transplanter was designed by coupling the motion of an earth-covering roller and a duck’s mouth planter and realized the precise mound of soil in the planting hole, solved the difficult problem of the precise mound of soil on the membrane, and at the same time carried out water injection on the root of the melon seedlings, which effectively solved the problem of low survival rate of transplanted seedlings in the arid region of Turpan, Xinjiang, China. Field experiments showed that the survival rate of melon seedlings under drip irrigation for 8 h after transplanting into dry soil exceeded 97%. The efficiency of mechanized operation can reach 1 mu/person/hour, which is more than 8 times higher than manual operation. The operation speed of the machine is 1~1.2 m/s, and the qualified transplanting rate is 93.26%, which meets the requirements of cantaloupe transplanting agronomy. This study provides a new method for dry soil cantaloupe transplanting. This article can also provide a design reference for Hami melon transplanting mechanization in arid areas.

Analysis optimization and modelling of CO2 welding process parameters in fabrication of mild steel plates

The point of the current examination is to show the impact of various information parameters, for example, welding current, circular segment voltage and root hole on the mechanical properties during the CO2 welding of gentle steel 1018 evaluation. The microstructure, hardness and rigidity of weld example are researched in this examination. The chose three information parameters were shifted at three levels. On the similarity, nine tests were performed dependent on L9 symmetrical exhibit of Taguchi's technique, which comprise three info parameters. Examination of change (ANOVA) was utilized to discover the degrees of noteworthiness of information parameters. Root hole has most prominent impact on elasticity followed by welding current and bend voltage. Circular segment voltage has most noteworthy impact on hardness followed by root hole and welding current. Microstructure of weld metal comprises of fine grains of ferrite and pearlite.

Failure investigation of a Kaplan turbine blade

Abstract In this paper, an uncommon failure of a Kaplan turbine blade has been analyzed. After the monitoring system detected a sudden increase in vibration levels, the turbine was inspected. The inspection showed that a large crack occurred on one blade starting from the leading-edge side root hole. Moreover, the tip of the blade was also found broken. A comprehensive analysis of the crack surfaces, broken parts and the vibration data revealed a fatigue problem probably caused by rubbing between the blade and the nearby wall. The effect of contacts on the stress distribution of the blade was investigated through a numerical model of the turbine blade. To validate this numerical model an experimental modal analysis was done on a non-damaged blade and the results showed a good agreement with the numerical results. Stress distribution analysis showed that when applying a contact force, the stress at the leading-edge root hole increases drastically. Therefore, experimental evidences as well as numerical simulations confirm that the crack occurred due to rubbing between the blade tip and the nearby wall.

Self‐Assembly of Lotus‐Type Holes Two‐Dimensional NiO Nanosheets and Its Efficient Catalytic Property for Styrene Epoxidation

AbstractLotus‐type holes two‐dimensional NiO nanosheets were fabricated via hydrothermal method followed by calcinations. Three types of surfactants as the structure‐directing agent in an ammonia aqueous solution with calcination, only anionic surfactant sodium dodecyl benzene sulfonate (SDBS), non‐ionic surfactant polyvinyl pyrrolidone (PVP) can form lotus‐type porous NiO nanosheets, cationic surfactant cetyltrimethyl ammonium bromide (CTAB) have no such effect. A series of characterization of the resulting samples revealed that the materials maintained singularly small thickness of only 3–5 nm, lotus root hole diameter 40 nm(SDBS),20 nm(PVP). The formation mechanism of the lotus‐type porous two‐dimensional morphology is investigated. The as‐synthesized NiO without support delivered efficient catalytic property in styrene epoxidation which significantly reduced reaction time. When the catalyst was reused the conversion and selectivity of styrene oxide still remained high.

V-notch tip subjected to in-plane mixed mode loading: overview of recent results and possible future outcomes

The fictitious notch rounding concept is applied for the first time to V-notches with root hole subjected to in-plane mixed mode loading. Outof- bisector crack propagation is taken into account. The fictitious notch radius is determined as a function of the real notch radius, the microstructural support length and the notch opening angle. Due to the complexity of the problem, a method based on the simple normal stress failure criterion has been used. It is combined with the maximum tangential stress criterion to determine the crack propagation angle. An analytical method based on Neuber's procedure has been developed. The method provides the values of the microstructural support factor as a function of the mode ratio and the notch opening angle. The support factor is considered to be independent of the microstructural support length. Finally, for comparison, the support factor is determined on a purely numerical basis by iterative analysis of FE models.

A review of the notch rounding approach under in plane mixed mode loading

The fictitious notch rounding approach is widely used for the fatigue assessment of welded joints and for this reason in the present paper a review of the concept applied to inclined lateral V-notches with root hole subjected to in-plane mixed mode loading has been carried out. This is the basis for future applications to welded structures in presence of mixed mode loading.The analytical framework of the method is herein recalled and the fictitious notch radius is determined as a function of the real notch radius, the microstructural support length and the notch opening angle. In order to reduce the complexity of the task, we adopt a method based on the normal stress failure criterion. The method provides the values of the microstructural support factor as a function of the mode mixity parameter and the notch-opening angle. Moreover, the support factor is assumed independent of the microstructural support length. Finite element simulations for various notch shape and configurations are compared to experimental data from pointed V-notches made of polymethylmethacrylate. The model prediction showed good agreement with the experimental results. These results are very promising for the application to welded structures.

The Effect of Friction Stir Processing by Stepped Tools on the Microstructure, Mechanical Properties and Wear Behavior of a Mg-Al-Zn Alloy

Friction stir processing (FSP) which imposes severe plastic strains has been used as a solid-state process to refine the grain structure of a Mg-Al-Zn alloy and therefore to enhance the strength and wear resistance without significant reduction of ductility. The introduced stepped tools result in more uniform microstructure, and therefore higher mechanical properties, as well as enhanced wear resistance. More passes of FSP could lead to more uniform microstructure and finer grains. The grain size was reduced from above 40 µm to below 4 µm. The pin root hole defect is also reduced during FSP by the stepped tools especially by cylindrical one. Microhardness was increased more than two times compared with the as-received sample. The tensile strength and elongation are almost doubled after different conditions of FSP. Coefficient of friction is reduced to 1/13.3, and weight loss has been reduced to about 50% of initial values after friction stir processing. The obtained results also demonstrated the successful dynamic recrystallization during FSP.

Tilted lateral V-notches with root hole subjected to in-plane mixed mode loading: Fictitious notch rounding concept

The fictitious notch rounding concept is applied for the first time to inclined lateral V-notches with root hole subjected to in-plane mixed mode loading. Out-of-bisector crack propagation is taken into account by combining the fictitious notch rounding approach with the maximum tangential stress criterion. Following the guidelines of a previous paper dealing with internal notches, the fictitious notch radius is determined as a function of the real notch radius, the microstructural support length and the notch opening angle. The problem is of formidable complexity and for this reason a simple method based on the normal stress failure criterion is adopted here. The analytical method based on Neuber's procedure proposed for central notches is extended here to tilted lateral notches. The method provides the values of the microstructural support factor as a function of the mode mixity parameter and the notch opening angle. The support factor is considered to be independent of the microstructural support length. To validate the approach about two thousands finite element analyses have been performed varying the notch shape and load configuration. Finally an experimental validation has been performed considering a complete set of data from pointed V-notches made of polymethylmethacrylate.

Crack Initiation at V-Notch Tip under In-Plane Mixed Mode Loading: A Review of the Fictitious Notch Rounding Concept

The fictitious notch rounding concept has been recently applied for the first time to V-notches with root hole subjected to in-plane mixed mode loading. Out-of-bisector crack propagation is taken into account. The fictitious notch radius is determined as a function of the real notch radius (the microstructural support length) and the notch opening angle. Due to the complexity of the problem, a method based on the simple normal stress failure criterion has been used. It is combined with the maximum tangential stress criterion to determine the crack propagation angle. An analytical method based on Neuber’s procedure has been developed. The method provides the values of the microstructural support factor as a function of the mode ratio and the notch opening angle. The support factor is considered to be independent of the microstructural support length. Finally, for comparison, the support factor is determined on a purely numerical basis by iterative analysis of finite element models. The present paper is aimed to give a brief overview of the recent findings on this challenging topic making clear the state of the art.

Crack initiation at V-notch tip subjected to in-plane mixed mode loading: An application of the fictitious notch rounding concept

The fictitious notch rounding concept is applied for the first time to V-notches with root hole subjected to in-plane mixed mode loading. Out-of-bisector crack propagation is taken into account. The fictitious notch radius is determined as a function of the real notch radius?? the microstructural support length and the notch opening angle. Due to the complexity of the problem, a method based on the simple normal stress failure criterion has been used. It is combined with the maximum tangential stress criterion to determine the crack propagation angle. An analytical method based on Neuber's procedure has been developed. The method provides the values of the microstructural support factor as a function of the mode ratio and the notch opening angle. The support factor is considered to be independent of the microstructural support length. Finally, for comparison, the support factor is determined on a purely numerical basis by iterative analysis of FE models.

Fictitious notch rounding concept applied to V-notches with root hole subjected to in-plane mixed mode loading

The fictitious notch rounding concept is applied for the first time to V-notches with root hole subjected to in-plane mixed mode loading. Out-of-bisector crack propagation is taken into account. The fictitious notch radius is determined as a function of the real notch radius, the microstructural support length and the notch opening angle. Due to the complexity of the problem, a method based on the simple normal stress failure criterion has been used. It is combined with the maximum tangential stress criterion to determine the crack propagation angle. An analytical method based on Neuber’s procedure has been developed. The method provides the values of the microstructural support factor as a function of the mode ratio and the notch opening angle. The support factor is considered to be independent of the microstructural support length. Finally, for comparison, the support factor is determined on a purely numerical basis by iterative analysis of FE models.

State‐of‐the‐art review on extended stress intensity factor concepts

ABSTRACTThe stress intensity factor concept for describing the stress field at pointed crack or slit tips is well known from fracture mechanics. It has been substantially extended since Williams' basic contribution (1952) on stress fields at angular corners. One extension refers to pointed V‐notches with stress intensities depending on the notch opening angle. The loading‐mode‐related simple notch stress intensity factors K1, K2 and K3 are introduced. Another extension refers to rounded notches with crack shape or V‐notch shape in two variants: parabolic, elliptic or hyperbolic notches (‘blunt notches’) on the one hand and root hole notches (‘keyholes’ when considering crack shapes) on the other hand. Here, the loading‐mode‐related generalised notch stress intensity factors K1ρ, K2ρ and K3ρ are defined. The concepts of elastic stress intensity factor, notch stress intensity factor and generalised notch stress intensity factor are extended into the range of elastic–plastic (work‐hardening) or perfectly plastic notch tip or notch root behaviour. Here, the plastic notch stress intensity factors K1p, K2p and K3p are of relevance. The elastic notch stress intensity factors are used to describe the fatigue strength of fillet‐welded attachment joints. The fracture toughness of brittle materials may also be evaluated on this basis. The plastic notch stress intensity factors characterise the stress and strain field at pointed V‐notch tips. A new version of the Neuber rule accounting for the influence of the notch opening angle is presented.

The fictitious notch rounding approach applied to V-notches with root holes subjected to mode I loading

The fictitious notch rounding concept is applied here to V-shaped notches with root holes subjected to mode I loading. The fictitious notch radius ρf is determined as a function of the real notch radius ρ, the microstructural support length ρ* and the notch opening angle 2α, at first using the normal stress criterion. Two analytical methods have been developed resulting in closed-form expressions for the multiaxiality factor s in the well-known relationship ρf = ρ + sρ*. The first method expresses the notch stress averaged over the microstructural support length at pointed V-notches by the maximum notch stress of fictitiously rounded V-notches (with root hole), taking advantage of a newly developed analytical solution. The second method considers V-notches with root holes both in the real and in the fictitious configuration. It uses a procedure given by Neuber. Finally, different failure criteria are considered using the first method. Plane stress and plane strain conditions, respectively, are evaluated.

Fictitious notch rounding concept applied to V-notches with root holes subjected to in-plane shear loading

The fictitious notch rounding concept is applied here for the first time to V-shaped notches with root hole subjected to in-plane shear loading. The fictitious notch radius is determined as a function of the real notch radius, the microstructural support length and the notch opening angle, at first using the normal stress criterion in combination with the maximum tangential stress criterion for finding the crack propagation angle. Two analytical methods have been developed resulting in closed form expressions for the multiaxiality factor s. Finally, for comparison, the factor s is determined also on a purely numerical basis by iteration of FE-models.

진동 해석을 통한 300 MW급 저압터빈 블레이드의 손상 원인 규명

The failure of blades frequently happened in the 300 MW LP(low pressure) turbine until now and they are maintaining the blades periodically during outage. So the blade-disk system is analysed by FEM in order to identify the main cause of failure of blade row. It is found that the stress of root's hole is highest in comparison with other parts from the result of the steady stress analysis. Also, the two dangerous frequencies which is related to the resonance condition are found in the interference diagram. One is 1,316 Hz. The other is 2,981 Hz which is related to the 1 nozzle passing frequency. The dynamic stress analysis is performed to identify more accurate root cause for failure of blade row It is confirmed that the dynamic stress of the former is higher than one of the latter From these results, it is concluded that the former has deeply something to do with the failure of blades more than the tatter. Based on versatile investigation and deliberation, the change of blade's grouping is determined to avoid the resonance condition with the operating speed. After the blade grouping is changed, the former frequency vanish completely but the latter is still in existence in the interference diagram. Fortunately, It is confirmed that the dynamic stress of the new blade grouping is lower than one of the old blade grouping. 2 years has passed since modification and the LP turbine is operated well without failure so far.

Roots in irrigated clay soils: Measurement techniques and responses to rootzone conditions

This paper reviews research carried out at the Griffith Laboratory in Australia over the last decade on techniques for, and results of, observations of roots in irrigated clay soils. Our results emphasise the adaptability of root systems to rootzone conditions. Experiences with techniques for observing roots non-destructively in the field and both non-destructively and destructively in lysimeters are described. We concluded that the minirhizotron technique, applied in the field, was unreliable under our conditions. Horizontal root observation tubes were used in lysimeters to measure root length density (RLD) and to assess whether roots were clumped together or randomly distributed. Destructive sampling and measurement of RLD was used to establish a theoretical relationship between root intercept counts along the tubes and RLD. The application of image analysis to both destructive and non-destructive sampling in the lysimeters is outlined. The non-destructive lysimeter studies showed that roots were significantly clumped. Analysis of root intercept and root hole counts on the faces of sample cubes taken from the lysimeters showed root distribution was anisotropic over the whole soil profile for both safflower and wheat. There were many more roots and root holes present in the sampled soil cubes than was indicated by independent sampling for washed out RLD. Safflower appeared to have a faster turnover of roots than did wheat or maize. Lysimeters, equipped with horizontal root observation tubes, enabled studies to be made of many factors affecting root growth. Soils affect where and how fast roots grow, although there is also a strong species interaction. For example, soybean roots proliferated above a fresh water table in one soil but not in another; wheat had little tendency to proliferate above the water table in either soil. In wet soils, roots cease to grow once soil oxygen levels decrease below 10 mg O2 lsoil-1. This level should form the basis for soil drainage criteria. In drying soils, roots will grow successively into soil regions containing soil water: the level of adaptation being determined by soil conditions, crop growth stage and level of evaporative demand. The methods of root observation used in our studies have given quantitative assessment of root distribution. However, further research is needed to link horizontal and vertical root distribution and root adaptation more strongly to crop development and soil conditions.

Auger Hole Seepage Theory

AbstractWe solve the problem of water flow into a soil cavity, as an auger hole or any cylindrically shaped hole, e.g., a vertical root hole or a large circular pit, in a surrounding water‐saturated, homogeneous, porous medium. We consider the top boundary of the saturated flow medium to be a water table, with the assumption that drawdown of the water table about the auger hole during flow is small. We consider flow when (i) there is an impermeable barrier at a finite distance below the auger hole and (ii) there is an artesian source at a finite distance below the auger hole. By letting the finite distance become large in (i) and (ii) we solve the problem of a finite auger hole in a medium of infinite depth. The analysis yields, both for finite depth of soil below the auger hole and infinite depth of soil below the auger hole, a table of shape factors C. When a shape factor C is multiplied by an observed rate of rise of water in the hole, the multiplication gives the hydraulic conductivity of the soil. We compare our work, when applicable, with that of others. Our C values agree in the main with earlier C values for their limited range.