Single Lug Research Articles

Residual strength prediction of single lug and yoke joints based on the J-A2 method

To examine the effect of fatigue cracks on the residual ultimate strength of 30CrMnSiA steel single lug and yoke joints for pontoons, we developed a residual ultimate strength J-A2 model. This model was constructed by applying fracture mechanics principles, and the law of decay of the residual ultimate strength of aging single lug and yoke joints with crack propagation was obtained. Using this model, the empirical relationships of the remaining ultimate strength engineering applications of a certain equipment joint were determined, and the rationality and practicality of the method were verified by combining fatigue tests and finite-element simulations. The results provide a foundation for further analysis of the influence of crack propagation on the ultimate strength of single lug and yoke joint structures.

Development of Double-Insulated Ring Sensors for Hollow Pin Preload Measurement

The hinge mechanism of aviation flap is composed of joint bearing, single lug, double lugs, hollow pins and self-locking nuts, etc. This hinge mechanism has accurate requirements for the preload of the hollow pin. When no seizure of the joint bearing occurs, the bolts are required to have sufficient preload to clamp the inner ring of the bearing. Meanwhile, when the seizure of the joint bearing occurs, there shall be no movement between the bearing and pin shaft or the end face of the bushing shall arise. This requires that the tension of the hollow pin shaft shall not be too high, otherwise the friction torque isn’t easy to overcome. However, the method to directly measure the preload in the hollow pin is not available, and the influence law of preload decline on the seizure resistance of the bearings also can’t be evaluated. This paper presents a method suitable for measuring the preload of hollow thin-walled pin parts. By applying permanent piezoelectric thin film transducer onto the end face of the hollow pin, the standardization technology is used to measure the propagation time change of the ultrasonic signal generated by the transducer in the pin as a function of the temperature and preload, thus realizing the accurate measurement for the preload of the hollow pin during installation. Finally, the application verification is conducted by using the measurement method proposed in this paper. The results show that this method can effectively optimize the installation and service performance for the hollow pin.

Local stress analysis of tailing lugs in a vertical pressure vessel

During the process of erecting a vertical pressure vessel from a horizontal to vertical orientation (0°to 90°) using tailing lugs, it is necessary to use a tailing lug with low local stress around the lug–shell attachment to prevent damage to the vessel shell during the lifting process. Two methods of local stress analysis, WRC-537 bulletin and FEA using ASME BPVC Section-VIII Division-2 are studied and evaluated in this paper. The WRC-537 method, which is known for being conservative, produced higher stress values compared to the FEA solution. This paper also examined the impact of various dimensional parameters related to tailing lug size and shape on local stress around the lug–shell attachment. In cases where single lug configurations fail to achieve the minimum required local stress values, paired lug configurations are purposed as a possible alternative solution towards reduced local stress. This paper also discusses the benefits of paired lug configurations over single lug configurations regarding the lower localized stress, especially for vessels with thin shells and large diameters. Paired lug configurations are found to have about four times lower localized stress compared to single lug configurations. When comparing rectangular and circular attachments, this study has found that rectangular attachments tend to have lower localized stress.

Crack extension analysis and fatigue life assessment of single lug and yoke joints containing initial defects

To investigate the impact of initial cracks on the fatigue performance of single lug and yoke joints, fatigue testing was performed for defective welding joint models. The crack extension behaviors were investigated based on the theories of fracture mechanics using ANSYS-FRANC3D interactive technology, and the effects of the initial crack location, morphology pattern, and surface angle on fatigue performance were determined. The results showed a fatigue failure mode in which the crack extended along the welding line for single lug and yoke joints. The fatigue life was shorter when the initial crack was in the corner of the single lug plate. Moreover, the crack growth rates during the early stage of crack extension varied significantly with different initial crack morphology patterns. However, the crack growth rates during the later stages were similar to one another. The remaining fatigue life increased with the shape ratio for the same crack depth. Finally, the crack growth rate was the fastest, and the remaining fatigue life was the shortest when the initial crack surface angle was inclined toward the stress concentration area.

An ivory bowl from Early Iron Age Tell es-Safi/Gath (Israel): manufacture, meaning and memory

In 2013, an ivory bowl was discovered in a chalky matrix in the Early Iron Age (Philistine) levels in Area A at Tell es-Safi/Gath. Conservation revealed it to be a shallow vessel with a single lug handle, decorated in the interior and on the base with an incised twelve-petal lotus-rosette surrounded by five concentric circles. Applying an object biography approach, we investigate the history and far-flung socio-cultural connections of the Tell es-Safi/Gath bowl, which is unique within Philistia. Specific reference is made to parallels in the ivory hoard from the Late Bronze/Iron Age transition (c. late twelfth century/early eleventh century bce) palace at Megiddo, Stratum VIIA. It is proposed that the Tell es-Safi/Gath bowl was one of a set manufactured somewhere in Canaan. The vessel became separated from the set, ending up as a foundation offering at this Philistine site.

1P2-A04 砂地におけるラグ作用力に関する実験的研究

Sandy terrain can be seen in various environments. For instance, beaches and deserts, and the surface of other planets are covered by sandy soil. In these types of environments, investigational robots are usually equipped with wheel driving mechanism having some protrusions called lugs or grousers. However, because the lug's motion trajectory and soil deformation interact each other intricately, there is no theory that support the relationships between generated forces and soil deformation or lug's moving trajectory. Therefore, in this study, we isolate the lug from the wheel and focus on a single lug. Based on experiments, the prediction models of generated forces are built and demonstrated the validity as a prediction equation.

Characteristics of normal and tangential forces acting on a single lug during translational motion in sandy soil

Lugs (i.e., grousers) are routinely attached to the surfaces of wheels/tracks of mobile robots to enhance their ability to traverse loose sandy terrain. Much previous work has focused on how lug shape, e.g., height, affects performance; however, the goal of this study is to experimentally confirm the effects of lug motion on lug–soil forces. We measured normal and tangential forces acting on a single lug as functions of inclination angle, moving direction angle, sinkage length, horizontal displacement, and traveling speed. The experimental results were mathematically fitted by using least square method to facilitate quantitative analyses on effects of changes in these motion parameters. Moreover, we compared the measured tangential forces to values calculated from a conventional tangential force model to evaluate the effects of the lug-tip surface, which is generally ignored in existing terramechanics models. The conclusions from this study would be useful for estimating the traveling performance of locomotive mechanisms equipped with lugs, modeling interaction mechanics between lugged wheels and soil, etc.

EFFECTIVENESS OF A CAGE WHEEL AS A TRACTION AID

This study was intended to evaluate the effectiveness of a cage wheel as a traction aid with driving tires of agriculturaltractors in wet paddy fields. The torques transmitted to the cage wheel and driving tire were measured under appliedpull. The torque required by a single lug was also measured. The measurements were made in a wet paddy field with a hardpan30 to 40 cm deep, in which tractors are not likely to operate without a traction aid. Experimental results showed that the cagewheel increased the traction performance of the tractor as the diameter of the cage wheel increased. About 36% to 43% ofthe total torque required by the test tractor was used by the cage wheel when its diameter was 1182 mm and 49% to 56% whenit increased to 1222 mm. The peak torque required by a single lug increased by 5% as the diameter increased from 1182 to1222 mm and by 17% as it increased to 1262 mm. The peak traction also increased by 31% and 59%, respectively, at the sameincreases in diameter. However, the inflation pressure of the driving tire and forward velocity did not significantly affect thecage wheel performance. Increasing the number of lugs increased the traction developed by the cage wheel. However, thetraction developed by individual lugs decreased due to their interferences. Finally, a mathematical model to estimate the grosstraction developed by a cage wheel was proposed.

Investigation of transition radiation from a regular-roughness interface

Transition radiation at the interface between two media having regular inhomogeneities is considered in the framework of perturbation theory, assuming that the dielectric constants of the two media differ insignificantly from each other. The advantage of this approach is that no limitations exist on the characteristic size of the inhomogeneities. The general case of a surface with two-dimensional roughness is considered. Attention is paid to radiation characteristics that are general for periodic structures, independently of their particular features. The physical picture of the radiation from a rough interface is determined by both longitudinal and transverse effects. The case of normal incidence of an electron on a planar interface having either single or multiple rectangular lugs (diffraction grating) is analyzed in detail. For the single lug infinite in one dimension, simple expressions for transition radiation intensity are obtained, for both relativistic and nonrelativistic electrons. They demonstrate that corrections to the plane-surface intensity become significant at small radiation angles. In this case the radiation is also completely unpolarized, i.e., the spectral energy density of the perpendicular component has the same order of magnitude as that of the parallel component. Consideration of these issues is important since rough surfaces, as compared to planar surfaces, give a number of additional results that may be used for the analysis of surface irregularities.

Wet clay soil behaviour under multiple cage wheel lugs

This paper presents the results of studies on the deformation of wet clay soil under the action of multiple lugs. The effect of trench spacing (the distance between trenches cut by successive lugs), lug slip and lug spacing on the soil deformation under cage wheel lugs was studies. Wedge formation under a succeeding lug has also been studied. It was observed that the soil behaviour under multiple cage wheel lugs was significantly affected by lug spacing and slip. The soil wedge formation as well as soil adhering to the succeeding lug was a strong function of lug slip and spacing. In all cases the soil deformation pattern was quite different from that caused by a single lug.

Formation of a boundary wedge on a single lug in wet clay soil

This paper presents the results of studies on soil wedge formation on a single lug surface moving slowly in a cohesive plastic soil. The effect of lug angle, slip and subsequent passing of a lug on soil wedge formation has been studied. The experimental results are compared with existing theories. The existing theories are found to be deficient in describing the mechanics of soil-lug interaction in these soils.

Behaviour of wet clay soil under single cage wheel lugs

This paper presents the results of studies on the deformation of wet clay soil under the action of a single lug. The effect of lug angle on the soil deformation has been investigated. The experimental results are critically compared with the conventional theories of soil failure. It was observed that the existing passive soil pressure theory could not be used to describe soil movement caused by the action of the cage wheel lug. Speculation about the soil failure prediction due to a rigid tine or soil cutting blade has raised doubts about the wisdom of applying this theory to other soil cutting tools.