DMTC has been progressing Australia’s industrial knowledge of four types of additive manufacturing through a detailed benchmarking program. The four additive manufacturing techniques that have been compared for application on metallic components are Selective Laser Melting (SLM), Electron Beam Melting (ARCAM), Direct Metal Deposition (DMD) and Wire and Arc Additive Layer Manufacturing (WALAM). The program has examined the evolution and character of the deposited metal for each of the four processes, and will go on to conduct a cost benefit analysis of their application.
Previous work has identified that additive manufacturing processes create residual stresses in the region in and immediately below the processed area. These stresses when tensile in nature compromise the structural integrity of the component. Due to this, understanding the tension or compression distribution and magnitudes for the different additive manufacturing technologies becomes a critical piece of information when selecting one of the four techniques for a particular application.
The Australian Nuclear Science and Technology Organisation (ANSTO) has provided access to and ‘beam time’ on their neutron strain scanner known as “KOWARI” to measure the residual stresses induced by each of the additive manufacturing techniques. Ti-6AL-4V samples were created in the shape of a wedge to imitate the effect of section thickness on residual stress formation. Strain maps of the four samples were then measured in ANSTOs neutron beam.
The results showed that that ARCAM, DMD and WALAM processes all produce a very low residual stress. SLM on the other hand was shown to produce a compressive stress state. This is exciting as compressive residual stresses are known to increase the structural integrity of metallic structures and therefore extend the fatigue life. This result makes SLM a more promising technology for future production of aerospace components.
Posted by DMTC on July 14th, 2014
Lightweight body armour systems are typically made of high hardness, low density ceramic tiles. Ceramics are arguably the best material for this application as they have a high specific compressive strength and are very effective at blunting or in some cases fracturing projectiles. Despite its overall suitability, a number of challenges with many of the ceramics used in armour systems remain, including limited formability and poor multi-hit capability.
DMTC researchers at VCAMM and Deakin University are looking at alternative materials and systems in an effort to provide new solutions for body armour that can deliver both increased performance and reduced weight. One system under investigation is a material known as ‘Polymer Ceramics’. This material is an aggregate composite produced by infusing hard ceramic particulate with high modulus polymers and nano-technology. The resulting material has been shown to offer a number of advantages over traditional ceramics including low temperature processing, ease of moulding and extreme multi-hit performance. Even in these early stages of assessment the materials has been shown to achieve 80% of the ballistic performance of silicon carbide.
Recent work has focused on improving the interfacial adhesion between the ceramic and the polymer which is believed to be the primary driver of the overall ballistic performance of the composite. To improve the interface, a silane treatment has been developed that modifies the surface of the ceramic particulates at the nano-scale. In combination with a fluidised bed treatment, this nano-scale surface modification is akin to depositing nano-sized hairs on the surface and thereby increasing the area for adhesion. The silane treatment of boron carbide led to 35% higher yield strength at break and 24% increase in modulus compared to untreated formulations. It is anticipated that the improved yield strength and modulus through silane treatment will bring the material to within 90% of the ballistic performance of silicon carbide. The ultimate goal of the research is to achieve equivalent ballistic performance to silicon carbide and thus create a more cost effective and easily fabricated body armour material option.
Posted by DMTC on July 7th, 2014
DMTC has run its first 2 day training workshop in Project Management to develop the skills of current DMTC sponsored postgraduate students and partner organisation employees.
The workshop was aimed specifically at preparing the attendees for a smooth transition to Project Leader roles within DMTC and our partner organisations with a specific focus on preparing for collaborative and research based projects.
The workshop was attended by 25 people and included training in project management tools, techniques, and DMTC project management processes.
This workshop forms part of DMTC’s ongoing program of professional development activities.
Posted by DMTC on June 30th, 2014
DMTC’s Automated Off-Line Programming (AOLP) capability has been successfully deployed on several naval and protected vehicle platforms by Australian defence industry. The capability allows a robotic assembly cell to self-program directly from the digitised assembly drawings and during operation can account for deviations in the component positions when physically jigged compared to the digitised assembly model.
In late May, the next evolution of the technology was successfully demonstrated to senior engineers and managers from Thales Australia. The focus of the AOLP capability has now progressed to application on welded tubular space frames. Space frames are a mass efficient way of constructing and tying together vehicle and platform systems and are gaining popularity in the design of lightweight vehicle chassis. Whilst they are a mass efficient way of building a chassis, the assembly process is difficult due to the numerous pipes and tubes that need to be precisely joined to each other in a 3-D web. AOLP can make this process more efficient by both positioning the tubes for welding and conducting the weld in an accurate and repeatable fashion.
Following the successful demonstration of the concept to Thales Australia at the welding laboratories at the University of Wollongong, DMTC researchers Stephen Pan, Nathan Larkin and their team are continuing to refine the technology for this new application. Beyond tubular space frames the AOLP technology has progressed sufficiently to now have potential application for other forms of assembly such as riveting, bolting and spot-welding. It is a capability that lends itself to future opportunities in cost effective mass-customisation where full scale production efficiencies and economies of scale can be realised while maintaining the option of bespoke one off productions and where configuration is limited only by the creativity of the design engineer.
Posted by DMTC on June 24th, 2014