Estimation of Residual Stress in Spiral Welded Pipe: Regression and Numerical Model

Double submerged spiral-welded pipe (SWP) is used extensively throughout the world for large-diameter pipelines. Fabrication-induced residual stresses in spiral welded pipe have received increasing attention in gas, oil and petrochemical industry. Several studies reported in the literature verify the critical role of residual stresses in the failure of these pipes. Therefore, it is important that such stresses are accounted for in safety assessment procedures such as the British R6 and BS7910. This can be done only when detailed information on the residual stress distribution in the component is known. In industry, residual stresses in spiral welded pipe are measured experimentally by means of destructive techniques known as Ring Splitting Test. In this study, statistical analysis and linear-regression modeling were used to study the effect of several structural, material and welding parameters on ring splitting test opening for spiral welded pipes. The experimental results were employed to develop an appropriate regression equation, and to predict the residual stress on the spiral welded pipes. It was found that the developed regression equation explains 36.48% of the variability in the ring opening. In the second part, a 3-D finite element model is presented to perform coupled-field analysis of the welding of spiral pipe. Using this model, temperature as well as stress fields in the region of the weld edges is predicted.

A Comparative Study of Tribological Behavior of Steel Sliding Against WC Under Mineral and Biodegradable Oil Lubrication

Now a days for machining operations apart from good tribological properties, the lubricant is also expected to be non-hazardous and non-polluting. When considering the ecological and environmental aspects in machining processes, the use of biodegradable oil can be an alternative source of lubricant due to its positive impact to employee health and environmental pollution. In this regard, our research work uses vegetable based cutting fluids developed from canola and sunflower oil, in an attempt to provide an eco-friendly environment. Experiments are carried out on a pin-on-disc tribometer with tungsten carbide (WC) pin against AISI 4340 steel disc for different sliding times under different environments, thus simulating the machining environment. The tribological properties, wear and friction of vegetable based oils were comparatively investigated with a commercially available mineral oil. Wear tracks and roughness profiles of test specimens were compared by using optical microscope and profilometer respectively. Results indicated that vegetable based canola oil demonstrated excellent tribological properties compared to that of commercial mineral oil.

Effects of Within Part Variation on Measurement System Analysis

Inherent variation of the measurement system, part-to-part variation and variation arising due to the operator are considered to be the most common sources of variation in a measurement system analysis (MSA). Often errors due to within part variation are overlooked, or even worse, are assumed to be from the inherent variation of the measurement system. Understanding the sources of variation in a measurement system is important for all measurement applications. It becomes even more critical when the part used to evaluate a gage has a significant within part variation. This is an important source of measurement system error that the current procedures followed for MSA studies do not clearly or adequately address. The primary reason for this is a lack of awareness, and there are no clear guidelines on conducting a MSA study under these circumstances. A detailed analysis of the effects of within part variation on MSA is described in this paper. An improved method for conducting the MSA under these circumstances is also presented. This improved and more effective MSA takes all sources of variations into consideration.

Development of Inner Rotating Core for a Molding Machine With Topology Optimization

Sulfur polymer concrete (SPC) is relatively new material used to replace Portland cement for making drain pipes currently being manufactured by horizontal spun technology which produces non-homogenous material distribution and low strength pipes. Due to drawbacks of existing machine, there is a necessity to design molding machine with improved technology for assuring homogenous compaction of material. In this research, a new machine is designed where inner rotating core is the main component for mixing, compressing and giving final shape of product. So, it is necessary to optimize this part in terms of topology to ensure robust functionality. First, the concept of a new molding machine was designed through problem exploration, idea generation, concept evaluation, and design improvement. The alternative was generated in consideration of customer requirements by applying TRIZ principles to overcome drawback of existing machine. One of the concepts was selected using scoring techniques where concepts are presented and compared with varieties of evaluating criteria. Topology optimization with density method has applied to design inner rotating core part for mass reduction and thereby optimum utilization of design space. Suitable engineering model was built based on loads, boundary condition and constraints. Loads are applied on inner core walls during mixing and compressing of sulfur concrete. Objective is focused to minimize the developed topology by maximizing stiffness. Repeated structural analysis is done to obtain the convergence data for optimal design. Optimized finite element topology is generated as CAD model for size optimization. The optimization study provided response charts of different design variables. Sensitivity analysis of the input variables helped in identifying the importance of each design variable and their respective effects on the output model. Different design points are rated on optimization study and best design points are chosen for the final dimension of structure. CATIA, OptiStruct and ANSYS are tools used for concept design, optimization of topology. To the end optimal topology is compared with the initial designed part in terms of weight and displacement. It is concluded that topology optimized model maximizes overall stiffness resulting in better and innovative product design with enhanced performance.

Extended Finite Element Analysis of Journal Bearing Dynamic Forced Performance to Include Fluid Inertia Force Coefficients

Reynolds equation governs the generation of hydrodynamic pressure in oil lubricated fluid film bearings. The static and dynamic forced response of a bearing is obtained from integration of the film pressure on the bearing surface. For small amplitude journal motions, a linear analysis represents the fluid film bearing reaction forces as proportional to the journal center displacements and velocity components through four stiffness and four damping coefficients. These force coefficients are integrated into rotor-bearing system structural analysis for prediction of the system stability and the synchronous response to imbalance. Fluid inertia force coefficients, those relating reaction forces to journal center accelerations, are routinely ignored because most oil lubricated bearings operate at relatively low Reynolds numbers, i.e., under slow flow conditions. Modern rotating machinery operates at ever increasing surface speeds to deliver more power in smaller size units. Under these operating conditions fluid inertia effects need to be accounted for in the forced response of oil lubricated bearings, as recent experimental test data also reveal. The paper presents a finite element formulation to predict added mass coefficients in oil lubricated bearings by extending a basic formulation that already calculates the bearing stiffness and damping force coefficients. That is, a small amplitude perturbation analysis of the lubrication flow equations keeps the temporal fluid inertia effects and develops a set of equations to obtain the bearing stiffness, damping and inertia force coefficients. The method does not impose on the cost of the original formulation which makes it very attractive for ready implementation in existing software. Predictions of the computational model are benchmarked against archival test data for an oil-lubricated pressure dam bearing supporting large compressors. The comparisons show fluid inertia effects cannot be ignored for operation at high rotor speeds and with small static loads.

Experimental Analysis and FEA of Friction Stir Welding on Aluminium Plates

An experimental study and a numerical simulation of friction stir welding (FSW) process on aluminum 6064 plates is presented. The numerical analysis is performed using finite element technique with LsDyna software and the Aleatory Lagrangian Eulerian (ALE) formulation. Input parameters on the FEM are the mechanical properties of the aluminum 6064 as workpiece and H13 steel properties as the tool. The finite element analysis results shown Von Mises stresses and plastic strain developed during the process. An experimental analysis was conducted with the variation of process parameters and the specimens obtained were evaluated by x-ray inspection, tensile tests, and hardness measurements.

Simulation Driven Processing Function Development, Offering and Operation

In today’s industry, functional provision is becoming more and more important, necessitating increased simulation support. In this paper, the objective is to present a modeling and simulation approach for simulation-driven design (SDD) to support function development. The scope of this paper is simulation support for developing hardware equipment used in processing industry. The research is founded on industrial needs identified through two parallel interview-based studies in the Swedish process industry. Both companies explore doing business with functional products rather than hardware, in scenarios where the responsibility for and availability of the functions may remain with the service provider. One as-is and one future (to-be) scenario are presented. A decomposition of a general processing function (applicable to both companies) describes how the companies transfer machine input to output specifications. The decomposition includes customer and provider value and the paper demonstrates, as part of the results and based on the SDD approach, how that value may be increased through evaluation and prioritization. Additionally, the SDD approach shows that it is possible to identify a set of solutions which meet the specified requirements, supporting evaluation and prioritization of business offers and activities.

Multi-Period Turning Interpolation Algorithm for High-Speed Machining of Continuous Line Segments With Limited Acceleration, Jerk and Chord Error

In this paper, a multi-period turning interpolation algorithm, with real-time look-ahead scheme based on S-curve control method, is presented. In this interpolation algorithm, the geometric precision and the dynamic performance are both satisfied. The machining efficiency is improved by multi-period turning transition, and the precision is also improved by S-curve control method. The computational efficiency of this algorithm meets the need of real-time machining. In addition, there is no accumulated error. At last, this algorithm is verified the validation by the experiments on 3-axis CNC machine.

Mitigation of Pore Generation in Laser Welding of Magnesium Alloy AZ31B in Lap Joint Configuration

Magnesium, as the lightest structural metal, has been widely used in the automotive and aerospace industries. Porosity is the main issue in the welding of magnesium alloys and can be caused by surface coatings, hydrogen gas, pre-existing porosity, the collapse of an unstable keyhole and vaporization of alloying elements. In this study, the effect of the oxide layer on pore generation in the welding of AZ31B-H24 magnesium alloy is investigated. A fiber laser with a power of up to 4 kW is used to weld samples in a lap joint configuration. Two groups of samples are studied: as received (AR) surfaces (where an oxide layer remains on the surface) and treated surfaces. The surface treatment includes two techniques: mechanical removal (MR) and the use of a plasma arc (PA) as a preheating source. Also, a separate set of experiments are designed for preheating samples in a furnace in order to investigate whether the pore mitigation effect of a plasma arc is caused by preheating. Observations include a weld bead profile achieved through optical microscopy, chemical compositions tested by Electron Dispersive Spectroscopy (EDS), and mechanical properties measured with a tensile test. The results obtained show that the preheating effect of a plasma arc procedure can effectively mitigate pore generation. The tensile-shear results reveal that PA samples have a higher strength than other groups of samples.

Polyhedral Space Curve Meshing Reducer With Multiple Output Shafts

In recent years, a gear named Space Curve Meshing Wheel (SCMW) has been invented based on the meshing theory of space curves instead of classic space surfaces. Well improved in many aspects after its invention, it has been applied within the Space Curve Meshing Reducer (SCMR). The design method of an invention named polyhedral SCMR is presented in this paper. With single input shaft and multiple output shafts, this SCMR has advantages like compact structure, flexible design and low cost. It is characterized by the application of the SCMW group containing one driving wheel and several driven wheels, whose rotation axes are concurrent at a point and radiate in polyhedral directions. A SCMW group can form a single-stage SCMR, while SCMW groups connected can form a multiple-stage SCMR. In this paper, geometric parameters of the polyhedral SCMR are defined, design formulas are derived, and an example is provided to illustrate the design process.