Friction Stir Welding
Friction welding processes use the heat generated between contacting surfaces that are in relative motion and pressed together to generate hot and clean surfaces to produce a joint. Rotary Friction Welding (RFW) joins two cylindrical cross sections using a relative rotational motion followed by compression of the cylinders. The most recent friction welding process uses a non-consumable rotating pin to produce heat between adjacent flat surfaces. This is called Friction Stir Welding (FSW).
Members of OxCam Engineering Arc (FTS Engineering Answers Ltd. and Transforming Stress Ltd.) have been developing CFD based methods to model FSW such that it can be easily implemented for a wide range of applications. This approach does not require fudge factors from test welds or extensive data sets for material behaviour and has been validated over a wide range of welding conditions.
It is important that the original joint line is mixed and compressed by the FSW tool during welding, whilst keeping the workpiece temperature controlled to avoid the generation of flash at the edge of the workpiece shoulder. Optimised welding procedures can be developed by welding trials, but there are significant advantages associated with the use of an accurate computer model to develop robust welding procedures.
A computer model of FSW can be used to make sensitivity studies of tool shapes before welding trials and to investigate the effect of variations in workpiece properties that may not be possible in a small welding trial. The methods developed by Oxcam Engineering Arc can be used in a straightforward manner to reduce the costs associated with the implementation of FSW within the requirements of new industrial applications.
We are able to support our clients with these manufacturing activities and more, contact OxCAM Engineering Arc to discuss your challenge!
Aerodynamic Development, Performance and Correlation
The aerodynamic development of road and racing cars is typically carried out through a combination of computational simulations, experimental tests in wind tunnels and road/track testing of the actual vehicle or a full-scale prototype.
OxCAM Engineering Arc has many years of experience working on most aspects of the aerodynamic development, covering design, CFD simulations, wind tunnel and track testing, aerodynamic performance analysis and correlation. Our experience shows that the complementary use of the information from the three domains is by far the most effective way of developing a design which is high performing throughout a wide range of “real world” operating conditions.
We pride ourselves in providing objective aerodynamic development services. Our broad experiences in the many areas of the aerodynamic development allow us to employ a holistic approach for problem-solving, taking into consideration the uncertainty around the input data and variables affecting the performance metrics and the modelling.
We ultimately work with our clients towards a process which is fit for purpose, avoiding overcomplex and over expensive solutions both in terms of resources requirement and turnaround time. We also consider our clients’ long-term ambitions and work with them advising on the steps required to further improve their processes. Contact OxCAM Engineering Arc to discuss your challenge!
Processing of CT and MRI Scans
The objective of the study was to demonstrate the process of taking a Medical Scan (either CT or MRI) extracting physical parts of the scan (in this case the carotid arteries) and carry out a simulation with that geometry.
Using an open source tool (3D Slicer), the CT Scan was segmented to extract the carotid arteries. The segmented carotid arteries are then exported from 3D Slicer and imported into STAR-CCM+ as stl files.
A Fluid Structure Interaction Simulation is then set up within STAR-CCM+. Appropriate boundary conditions are applied. A pulse flow rate at the inlet and a series of windkessel models at the outlets. Material properties are applied to the artery walls, and a pseudo “neck” is added around the artery to give the damping effect the neck does in reality.
We are able to support our clients with converting CT/MRI data to simulations, ensure sensible simulation set up and carry out FSI simulations; contact OxCAM Engineering Arc to discuss your challenge!
Engineering Critical Assessment
AWS D1.1 (‘Structural Welding Code – Steel’) contains design by rule guidance on acceptance criteria for welds that are based on visual, ultrasonic and radiographic inspection. The rules are considered to be suitable for most situations, but the code accepts that a different approach may be used if it is documented and approved by the Engineer (a qualified person with responsibility for the safety of the fabrication). Of significance for many applications is the AWS view that no cracks are acceptable.
Welding is undertaken in a wide range of industries and some of these will exclusively adopt the design by rule approach because of an associated assumption of demonstrable safety. Other concepts have been developed and gained industrial acceptance. These are based upon strength of materials principles. The quality standards of welding codes are known to work, but they may be overly conservative. Methods that demonstrate the strength of welds based upon more fundamental ideas have been called Engineering Critical Assessments (or ECAs).
Welding was being increasingly used in the 1930s because it was found to be a more efficient method of creating structures. But, the implications of locally melting metal were not fully understood and there were some high profile failures. Engineers found that fracture mechanics, which was an evolving discipline at this time, could explain some of the failures. Guidelines were written to show how knowledge of material toughness could be used to assess the conditions under which failure from a from a welding defect might occur. In the UK the British Standards Institution provided the Published Document PD 6493:1980 and the electricity supplier (the CEGB) had released R/H/R6 (npw known as R6) in 1976. From this time, therefore, it was possible to assess a welding flaw using both the design by rule weld quality system (like AWS D1.1), but also to directly judge the effect of weld defects on the load carrying capacity of a fabrication by undertaking an ECA.
Codes and standards today
OxCAM Engineering Arc’s partner Transforming Stress Ltd has significant experience of the application of modern ECA methods to fabrications. Simon Smith first started developing Finite Element Analysis (FEA) methods for application to fracture mechanics in the early 1980s. He has supported ECA project teams where they have needed to augment their assessments using numerical techniques to determine Stress Intensity Factors (SIFs) or collapse loads for complex geometries. Dr Smith has also contributed to the development of the methods contained in standards, including R6, BS 7910:2019 and API 579-1 2016.
Transforming Stress Ltd can contribute to the reductions of conservatisms in ECA methods through their knowledge of the theoretical basis of the methods, and can advise on their safe adoption by your engineers and suppliers. Transforming Stress Ltd have access to the latest versions of both BS 7910 and API 579.
Strain Based Design (SBD)
Typically, engineering structures undergo cycles of loads and engineering design codes ensure that the material and geometry of the components of the structure resist the applied load at primary stress levels that are below the material yield strength.
There has been significant recent interest in the resistance of structures to higher nominal loads. Pipeline installation and in-service design conditions in some instances require a demonstration of resilience under levels of applied strain that are greater than the material yield strain.
It has therefore been necessary to develop advanced integrity assessment methods so that safety can be demonstrated under these more extreme levels of loading. For welded structures, assessments should demonstrate defect tolerance, at least for the defects that could be missed by the associated inspection procedures. Generally, weld defect tolerance calculations have been called Engineering Critical Assessments (ECAs) and their application to post yield loading is known as Strain Based Design (SBD).
OxCAM Engineering Arc’s partner Transforming Stress Ltd has significant experience of SBD including the use of Finite Element Analysis (FEA), the development and review of full scale tests and the application of analytical methods. Transforming Stress Ltd wrote a discussion paper for the International Journal of Pressure Vessels and Piping which described a validated method of SBD (see HERE).
The method proposed by Transforming Stress Ltd has been accepted by committee WEE/37 (‘Acceptance levels for flaws in welds’) of the British Standard Institution (BSI) and is now the SBD ECA procedure in Annex V of BS 7910:2019 (HERE).
For more information on SBD and on Annex V of BS 7910:2019 get in touch with OxCAM Engineering Arc.
The treatment of sewage typically consists of several stages of filtering and separation of phases. One of these stages was analysed by OxCAM Engineering Arc, it consisted of an input flow containing predominantly a mixture of water and fats, the objective being to separate the phases. The tank was designed to output water through a lower outlet and a high fat content mixture through an upper outlet duct.
The design was exposed to an extreme operating condition in which the input volumetric flow was increased by 10x compared to the baseline condition, which resulted in very poor phase separation performance.
We were able to evaluate design variations while considering others engineering constraints which included installation cost and impact on the tank maintenance. An add-on flow diverter was added to the unit near the flow entry point, this significantly improved the phase separation performance within the problematic operating condition while resulting in only a small implementation cost for the client.
We are able to support our clients with multiphase flow simulations, contact OxCAM Engineering Arc to discuss your challenge!
One option for corneal transplants is DMEK (Descemet Membrane Endothelial Keratoplasty). The procedure is outlined here. As described, once the replacement cornea is unrolled and positioned in the anterior chamber of the eye, SF6 or Air is injected below the cornea graft to push it up to the graft site. SF6 or Air is then left in the chamber until it is naturally replaced by the aqueous fluid of the eye. This takes a few days.
During the recovery period the patient is instructed to lie down for longer periods especially in the immediate period after surgery. Following this period the patient is allowed to move freely. It is known that some grafts peel away from the graft site, and the surgery must be repeated.
OxCAM Engineering Arc member, FTS Engineering Answers, is working with Moorfields Eye Hospital to investigate the problem using CFD.
We are helping to show that the presence of both liquid and gas in the anterior chamber during the motion, as a patient moves from horizontal to vertical, may causes a force that effectively drags the cornea graft off the graft site. Removing the air/gas reduces or eliminates the force. This discovery may potentially lead to a change of surgical procedure.
Contact OxCAM Engineering Arc to discuss your biomedical challenge!
Formula 1 Brakes Thermal Management
High performance braking systems such as those employed in Formula 1 cars are responsible for converting high levels of kinetic energy into heat, which is then rejected to the environment through the cooling flow.
Sabe Fluid Dynamics has many years of experience working with development of the cooling flow for these complex systems, which includes the design, simulation, testing, correlation and on-track performance analysis. The case study for download offers more details on the engineering challenges and our experience working with such systems.
We are able to support our clients with any of the above-mentioned activities, contact OxCAM Engineering Arc to discuss your challenge!
Aerodynamic Damping Calculation
Aerodynamic performance maps are often used for the simulation of the behaviour of a given vehicle or craft within the expected operating conditions. These maps are typically created based on experimental tests or simulations at several static or near-static conditions measuring the loading dependency on variables such as attitude, wind speed, wind direction and others.
These performance maps are called quasi-static, the fundamental assumption being that the measured loading does not depend significantly on the rate of change of the input variables. While this assumption can certainly be valid within most stable steady-state operating conditions, the uncertainty increases when considering transient manoeuvres or steady-state conditions subjected to large amplitude oscillations.
OxCAM Engineering Arc’s partner Sabe Fluid Dynamics has developed a methodology using CFD simulations with an imposed oscillatory motion for extracting the viscous and inertial aerodynamic components of a sailing boat. These, when added to the quasi-static map, tend to improve the performance prediction through the transient stages of the boat operation.
We are able to support our clients with performance mapping, contact OxCAM Engineering Arc to discuss your challenge!
Automated CFD Process for Aerodynamics
OxCAM Engineering Arc has developed a fully automated CFD process for aerodynamics simulations. This takes the CAD input and returns the results without any intermediate user intervention. The main challenge was combining a routine which could robustly process highly complex input geometries, locally repairing critical areas while maintaining adequate surface representation and obtaining consistent and repeatable solutions throughout the development program.
The methodology was developed around the CFD software STAR-CCM+ using Java classes, objects and macros to drive the process. The information regarding geometrical topology and key setup parameters are provided to the process through an input file which is created through an UI developed. The process is able to run straight-line or cornering conditions, with or without thermal input.
The process was benchmarked against a reference project and approved to be deployed. We supported the client during its first aerodynamic development project with the newly developed process, in which over 200 simulations were successfully carried out.
We are able to support our clients with the development of data infrastructure and process automation, contact OxCAM Engineering Arc to discuss your challenge!