Introduction
The word ‘topology’ is formed by the combination of two Greek words - 'topo' and 'logy'. Topo means 'place' in Greek and logy means 'study'. In mechanical engineering terms, 'topology' therefore means the study of the placement of various elements / parts in a component / assembly. Study of topology plays a very critical role in the design of a new component. With competition getting keen, organizations are looking at avenues to reduce costs. Take the case of aerospace engineering or automobile engineering. Manufacturers would be happy with components that are fully functional, yet lightweight. This would ensure better fuel efficiency, and is especially an important consideration in the aviation sector. When mechanical engineers say ‘fully functional’, what it means is that the component / assembly is capable of doing its job satisfactorily, and involves parameters like tensile strength, elastic modulus, fracture toughness, strain at maximum strength, shear modulus, etc. It is an engineering challenge to optimize a part / component so that it is fully functional, as lightweight as possible and still cost less to manufacture. From an engineering perspective, topology optimization can be defined as a mathematical method that involves the study of geometrical properties and spatial relations for a given system for a set of defined loads, boundary conditions, and constraints, in order to optimize performance. The three important elements involved in topology optimization are design variables, the cost function and the constraints.
Basic engineering optimization methodologies
There are three basic categories of engineering methodologies to optimize a design. Sizing optimization is one of the most popular methods as it is relatively less complex. It is easy to conduct sizing optimization by choosing cross-sectional dimensions of beams and frames, or the thicknesses of membranes, plates and other such components as design variables. Sizing optimization can be regarded as a detailed design procedure of the structural model involving a large number of design variables. Much research has gone into it, and the model is now mature. It is one of the most popular methods in engineering community today.
Shape optimization aims at designing structural boundaries or holes in a structure. It improves analysis of local phenomenon like stress distribution. Both sizing and shape optimization methods are detailed design procedures without changing the specific topology of a structure.
Topology optimization is a technology for developing optimized structures considering design parameters like expected loads, available design space, materials, and cost, while controlling the part / component weight. It works very well for all types of linear analysis. While being mesh sensitive, topology optimization is not overly limited by size. Topology optimization has been increasingly used for mechanical part design in recent years due to its simplicity and usefulness. Most engineers believe that topology optimization gives a wider set of possibilities and a larger degree of freedom with regard to the design space availability, as compared to size optimization or shape optimization. It reduces design efforts to review concepts of the geometrical models of the parts in accordance with the targets defined in the list of requirements. Thanks to advanced software like Altair Inspire Platform and Altair OptiStruct, this method has now grown most popular at the conceptual design stage as it helps designers come up with several design solutions. Engineers can then evaluate the most optimal solution and choose the best one that serves the purpose.
Let us now understand how 3D printing helps topology optimization.
Advantages of 3D Printing in Topology Optimization
As far as topology optimization goes, one of the most important reasons 3D printing scores over traditional manufacturing is that it is additive manufacturing process, unlike traditional manufacturing, which is subtractive. There are many popular 3D printing processes and machines, but very few have the required material and capability to build an actual functional part This makes a vast different to engineers for trying out topical optimization models. Since traditional design are geared for subtractive manufacturing product engineers were restricted to design a component considering the traditional machines, tools required, material flow which would be production feasible. It is also possible to use composite materials, which are formed by combining two or more materials that have different properties, for 3D printing.
3D printing gives engineers the latitude to design products that cannot be manufactured in traditional way as the process of adding material, allows for more intricate shapes. This has given engineers a huge advantage in experimenting with designs that are robust, yet lightweight and functional. If you take a look at the latest prototypes of automobiles, motorcycles and aircrafts, you will come to know that such intricate and kind of esoteric designs cannot be manufactured using regular processes; only 3D printing works. And with 3D printing leaders introducing 3D printers that work with metals and other high end material like Ultem, Diran, nylon carbon fibre and other fancy raw material like wood, rubber, glass, etc. and print very large parts like an entire aeroplane wing or even a house, topology optimization takes on a new meaning.
Before the advent of 3D printing, manufacturing of the topologically optimized designs was a challenging task, sometimes not totally achievable, due to complex geometrical features and hidden cavities. These constraints led to not only in an increase of the final mass of the component to be designed, but also in an increase of the design processing time and cost.
In the upcoming future, it is believed that aircraft and aerospace structures, especially most Unmanned Aerial Vehicle (UAV) structures, customized automobiles, will be designed and fabricated as unconventional integral structures to save weight and simplify the assembling procedure. With this new concept, the combination of topology optimization and additive manufacturing will surely play an important role in developing high-performance and lightweight structure systems.
Software
With increased computing power, it is now possible to apply numerical methods to optimize product design. The latest technological advancements like artificial intelligence (AI), parametric CAD tools and numerical solvers have further enhanced the design process with regard to fast computations and complex simulations with the help of topology optimization. It has bought to fore topology optimization as one of the most promising techniques for designing products. Coupled with the right software - for example the Altair Inspire™ platform and Altair OptiStruct™ - 3D printing is revolutionizing manufacturing with designs that are innovative, lightweight, inexpensive, and yet fully functional.