Sensitivity analysis of factors affecting motion reliability of manipulator and fault diagnosis based on kernel principal component analysis

As an important index to quantitatively measure the motion performance of a manipulator, motion reliability is affected by many factors, such as joint clearance. The present research utilized a UR10 manipulator as the research object. A factor mapping model for influencing the motion reliability was established. The link flexibility factor, joint flexibility factor, joint clearance factor, and Denavit–Hartenberg (DH) parameters were comprehensively considered in this model. The coupling relationship among the various factors was concisely expressed. Subsequently, the nonlinear response surface method was used to calculate the reliability and sensitivity of the manipulator, which provided an applicable reference for its trajectory planning and motion control. In addition, a data-driven fault diagnosis method based on the kernel principal component analysis (KPCA) was used to verify the motion accuracy and sensitivity of the manipulator, and joint rotation failure was considered as an example to verify the accuracy of the KPCA method. This study on the motion reliability of the manipulator is of great significance for the current motion performance, adjusting the control strategy and optimizing the completion effect of the motion task of a manipulator.

In-Plane Flexibility Factor of 90 Degree Long Radius Elbows With Large Diameter

Bend flexibility factor is defined as the ratio of rotation of a pipe bend to that of a straight pipe of the same diameter, wall thickness and length under the action of the same bending moment. In stress analysis of piping systems with the beam method, this factor is of great importance and plays a direct role in the formation of the stiffness matrix of a system. The exact calculation of this coefficient results in the precise amount of force and moment being obtained on anchor points (i.e., equipment nozzles) and also in stopper and guide restraints. Different codes such as ASME B31.3 and B31.1 present a formula for this factor without consideration of the end effect (constraint of bend ends by the adjacent straight pipe). Another limitation is that these formulas are valid only within the range of D/T ≤ 100 (diameter to thickness). In this paper the effect of adjacent straight pipes on in-plane flexibility factor of long radius 90-degree elbows has been investigated and it has also been demonstrated that the equation presented in ASME B31J-2017 as the minimum required length for the attached straight pipe is highly accurate and greater values do not have much effect on elbow flexibility. Finite element analysis (FEA) studies have been carried out on 31 models with various diameters and thicknesses for both D/T ≤ 100 and D/T > 100 and in all cases the high precision of the given equation in B31J-2017 is indicated. Also, a new formula of in-plane flexibility factor (with consideration of the end effect) for long radius-90degree elbows is presented that has acceptable accuracy in all ranges of D/T. The new formula reveals that the B31 equation also has an acceptable accuracy even for D/T > 100.

Implementing B31J-2017 SIF and Flexibility Factor Changes for B31 Piping Systems

This paper discusses when new SIF and k-Factors from ASME B31J-2017 should be used for operating and new piping systems. Screening guidelines are provided to help plant owners know when current operating facilities may be subject to through-wall leaks as they approach given life milestones. The paper also shows when these same guidelines can be used in new system designs to require the use of more applicable SIF data, of qualified vendor lists and additional inspections.

Elbow Flexibility Factor Calculations: An Update

Widely cited across industry, earlier work by Rodabaugh and Moore, as well as Rodabaugh, Iskander and Moore described the equations to be used during experimental or finite element analysis studies into the flexibility of elbows. The original work was done to determine the flexibility factors commonly used in the piping Codes. However, these equations were only applicable to 45°, 90°, and 180° elbows with equal length of attached pipe. Recently, the authors had need to calculate the flexibility factors for elbows with non-equal lengths of attached piping and angles different from 45°, 90°, or 180°. This paper presents the expanded set, and hence general case, for the elbow flexibility factors.

Dolomitization Associated with Sea Level and Ocean Current Circulation in the Southern Marion Platform, Offshore Ne Australia

On the Southern Marion carbonate platform, dolomitization is triggered by the circulation of normal or slightly modified seawater and is related to changes in sedimentation rate and sea level change. Dolomitization further modifies formation permeability and fluid flow patterns. Dolostone/calcareous dolostone with large vuggy or moldic porosity is formed by fabric-preserving dissolution and recrystallization, which increases the pore space and facilitates the fluid flow effectively, with permeability ranging from 1[Formula: see text]mD to 10,000[Formula: see text]mD. The frame flexibility factor ([Formula: see text]) is a rock physics parameter which is a proxy of pore structure. We find that at given porosity dolostone with larger pores, higher permeability and higher sonic velocity usually has lower values of frame flexibility factor than limestone. After strong compaction and cementation, the limestone frame occludes fluid flow, prevents dolomitization and has permeability as low as 0.02[Formula: see text]mD. Acoustic impedance inversion confirms that the asymmetric geometry of the Southern Marion platform is shaped by the oceanographic currents, which are caused by the southward-flowing East Australian Current. Three layers of dolostone with large pores in the upper platform reveal strong fluid flow within the carbonate platform, leading to dolomitization and dissolution. These three strongly dolomitized zones follow the platform topography, indicating that the diagenetic fluid flow is driven by oceanographic currents. Three large-pore-formation dolomitization events match well with three highstands of sea level events, illustrating that the highstand of sea level induces the formation of dolomitization zones with large pores. This study demonstrates the positive feedback loop of dolomitization and ocean current circulation, as well as the relationship between dolomitization and sea level change, which could be applicable for better understanding subsurface fluid-rock interactions and dolomitization pore systems in other carbonate environments.

Sustained Stress Indices (SSI) in the B31.3 2010 Edition

The 2010 version of B31.3 introduced sustained stress indices (SSI’s) in paragraph 320. Using methods in references [1],[2],[3],[4],[5], and [11], a test procedure was developed to evaluate these SSI’s for standard metallic piping components. The test procedure has been incorporated into draft versions of B31J so that the sustained stress index can be produced at the same time stress intensification or flexibility factor tests are performed for a particular component. This paper describes the sustained stress index and the B31J test procedure used to determine the SSI.

Bend Flexibility Factors of Piping Elbows and Piping Elbows With Trunnion Attachments Using the Boundary Element Method

Flexibility Factor is an important parameter for the design of piping system related to oil, gas and power industry. Elbows give a great flexibility to piping system, but where a trunnion is attached to an elbow in order to support vertical pipe sections, the piping flexibility is affected. Generally, determination of elbow flexibility factors has been performed by engineering codes such as ASME B31.3 or ASME B31.8, or using the Finite Element Method (FEM) and Finite Difference Method (FDM). In this work, bend flexibility factors for 3D models of piping elbows and piping elbows with trunnion attachments using the Boundary Element Method (BEM) are calculated. The BEM is a relatively new numerical method for this kind of analysis, for which only the surface of the problem needs to be discretized into elements reducing the dimensionality of the problem. This paper shows the simulation of 9 elbows with commercially available geometries and 29 geometries of elbows with trunnion attachments, 10 of them using commercial elbow dimensions, with applied in-plane and out-of-plane bending moments. Structured meshes are used for all surfaces, except the contact surface of elbow-trunnion joints, and no welded joints are simulated. The results show smaller values of flexibility factors of elbow and elbow–trunnion attachments in all loading cases if are compared to ASME B31.3 or correlations obtained from other works. The results also indicate that flexibility factor for elbow-trunnion attachment subjected to in-plane bending moment is greater than flexibility factor for out-of plane bending moment. Accuracy of BEM’s results were not good when flexibility characteristic values are lesser than 0.300, which confirm the problems of this numerical method with very thin-walled structures. The method of limit element could be used as tool of alternative analysis for the design of made high-pitched system, when the problem with very thin-walled structures is fixed.