Manufacture of Defined Residual Stress Distributions in the Friction-Spinning Process: Investigations and Run-to-Run Predictive Control

Friction-spinning as an innovative incremental forming process enables high degrees of deformation in the field of tube and sheet metal forming due to self-induced heat generation in the forming area. The complex thermomechanical conditions generate non-uniform residual stress distributions. In order to specifically adjust these residual stress distributions, the influence of different process parameters on residual stress distributions in flanges formed by the friction-spinning of tubes is investigated using the design of experiments (DoE) method. The feed rate with an effect of −156 MPa/mm is the dominating control parameter for residual stress depth distribution in steel flange forming, whereas the rotation speed of the workpiece with an effect of 18 MPa/mm dominates the gradient of residual stress generation in the aluminium flange-forming process. A run-to-run predictive control system for the specific adjustment of residual stress distributions is proposed and validated. The predictive model provides an initial solution in the form of a parameter set, and the controlled feedback iteratively approaches the target value with new parameter sets recalculated on the basis of the deviation of the previous run. Residual stress measurements are carried out using the hole-drilling method and X-ray diffraction by the cosα-method.

Residual Stresses from Incremental Hole Drilling Using Directly Deposited Thin Film Strain Gauges

Background Commonly, polymer foil-based strain gauges are used for the incremental hole drilling method to obtain residual stress depth profiles. These polymer foil-based strain gauges are prone to errors due to application by glue. For example zero depth setting is thus often erroneous due to necessary removal of polymer foil and glue. This is resulting in wrong use of the calibration coefficients and depth resolution and thus leading to wrong calculations of the obtained residual stress depth profiles. Additionally common polymer foil-based sensors are limited in their application regarding e.g. exposure to high temperatures. Objective This paper aims at a first step into the qualification of directly deposited thin film strain gauges for use with the incremental hole drilling method. With the directly deposited sensors, uncertainties regarding the determination of calibration coefficients and zero depth setting due to the absence of glue can be reduced to a minimum. Additionally, new areas of interest such as the investigation of thermally sprayed metallic layers can be addressed by the sensors due to their higher temperature resilience and their component inherent minimal thickness. Methods For the first time, different layouts of directly deposited thin film strain gauges for residual stress measurements were manufactured on a stainless steel specimen. Strain measurements during incremental hole drilling using a bespoke hole drilling device were conducted. Residual stress depth profiles were calculated using the Integral method of the ASTM E837 standard. Afterwards, strain measurements with conventional polymer foil-based strain gauges during incremental hole drilling were conducted and residual stress depth profiles were calculated accordingly. Finally the obtained profiles were compared regarding characteristic values. Results The residual stress depth profiles obtained from directly deposited strain gauges generally match the ones obtained from conventional polymer foil based strain gauges. With the novel strain gauges, zero depth setting is simplified due to the absence of glue and polymer foil. With the direct deposition, a wide variety of rosette designs is possible, enabling a more detailed evaluation of the strain field around the drilled hole. Conclusions The comparative analysis of the obtained residual stress depth profiles shows the general feasibility of directly deposited strain gauges for residual stress measurements. Detailed investigations on uncertainty sources are still necessary.

Advances in Laser Drilling of Structural Ceramics

The high-quality, high-efficiency micro-hole drilling of structural ceramics to improve the thermal conductivity of hot-end parts or achieve high-density electronic packaging is still a technical challenge for conventional processing techniques. Recently, the laser drilling method (LDM) has become the preferred processing tool for structural ceramics, and it plays an irreplaceable role in the industrialized processing of group holes on structural ceramic surfaces. A variety of LDMs such as long pulsed laser drilling, short pulsed laser drilling, ultrafast pulsed laser drilling, liquid-assisted laser drilling, combined pulse laser drilling have been developed to achieved high-quality and high-efficiency micro-hole drilling through controlling the laser–matter interaction. This article reviews the characteristics of different LDMs and systematically compares the morphology, diameter, circularity, taper angle, cross-section, heat affect zone, recast layer, cracks, roughness, micro–nano structure, photothermal effect and photochemical reaction of the drilling. Additionally, exactly what processing parameters and ambient environments are optimal for precise and efficient laser drilling and their recent advancements were analyzed. Finally, a summary and outlook of the LDM technology are also highlighted.

Significant Reduction in Energy Consumption and Carbon Emission While Improving Productivity in Laser Drilling of CFRP Sheets with a Novel Stepped Process Parameter Parallel Ring Method

Although laser drilling of carbon fibre-reinforced polymer (CFRP) composites offers the advantages of zero tool-wear and avoidance of fibre delamination compared with mechanical drilling, it consumes considerably more energy during the drilling process. This research shows that by using a new, stepped parameter parallel ring laser hole drilling method, an energy saving of 78.10% and an 18.37 gCO2 reduction for each hole, while improving productivity by more than 300%, can be achieved in laser drilling of 6 mm diameter holes in CFRP sheets of 2 mm in thickness, compared with previous laser drilling methods under the same drilling quality. The key reason for this is an increase in energy input to the inner rings enabling more rapid removal of the material, while the lower energy input for the outer ring provides a shielding trench to reduce the heat loss into the parent material. The results are compared with single-ring laser drilling and multiple-ring laser drilling with constant processing parameters, and a discussion is given on comparing with mechanical drilling and future prospects, including a combined mechanical drilling and laser pre-scribing process.

FINITE ELEMENT ANALYSIS OF TOOLS FOR DEEP DRILLING TECHNOLOGY

Using the ANSYS software package, the issues of strength of the drill head and temperature distribution were considered, the design of a modern tool for deep hole drilling was analyzed, and modal analysis was carried out to exclude possible resonance phenomena.

Hydraulic Workover Unit Utilization for New Well Openhole Drilling with Directional Motor and Logging-While-Drilling Bottom-Hole-Assembly in M Area

Achieving a number of well targets in M Area is an important objective for MK, one of the oil and gas operators in Indonesia. An economic challenge is present due to marginal gas reservoirs in shallow zone. The conventional swamp rig unit requires significant costs for site preparation work and in some cases no longer fulfils the economic criteria. The objective was to drill the same one-phase well (OPW) architecture as the swamp rig normally drills, but at lower costs using a hydraulic workover unit (HWU). Drilling the 8½-in hole section OPW architecture using HWU was challenging, not only on the equipment rating and capability, but also on the deck space limitation part. The fit-for-purpose directional and logging-while-drilling (LWD) system was utilized in this project consisting of customized low-torque excellent hydraulics drill bit design, a positive displacement motor (PDM) with aggressive bend setting to achieve directional objective (with max 3.8°/30-m dogleg severity), annular-pressure-while-drilling (APWD) measurement to ensure equivalent circulating density (ECD) is maintained, and combined electromagnetic propagation resistivity and sonic slowness measurement coupled with high-speed telemetry measurement-while-drilling (MWD) tool to get an accurate and timely formation evaluation. The HWU deck space limitation was solved by implementing a single combined directional drilling (DD), MWD, mudlogging cabin, in addition to the remote operation control implementation to further reduce carbon footprint. Five wells were drilled safely and successfully in this campaign. Drilling efficiency improved with up to 109% ROP increase as compared to the first well, showing the progressive learning curve and excellent teamwork from all involved parties. The directional bottom hole assembly (BHA) was capable of delivering up to 4–5°/30-m dogleg, not only achieving the directional objective, but also penetrating the reservoir targets with tight tolerances. The drill bit delivered very good ROP, reaching 60.4 m/h (about 66% of average OPW ROP achieved by swamp rig). This campaign also successfully reduced the overall site preparation cost by up to 30%, enabling MK to drill wells that were initially not feasible to be drilled using swamp rig within the time frame and budget. Thanks to the success, this new method is currently under study for industrialization. The HWU drilling campaign provided a valuable learning experience, is considered as a proven drilling method, and served as a benchmark for other operators in Indonesia. HWU drilling has proven to be an efficient drilling method and capable of delivering the one-phase-well. This paper presents a unique case study of new well open hole drilling with the HWU and its applicability in M Area. Most studies in the past were HWU drilling in re-entry or sidetrack cases.