In the Additive Manufacturing (AM) industry structural simulation engineers are increasingly confronted with the question “Can you simulate how long the part will last under given loading?". This is a reasonable question to be addressed to the engineer, however, in case of 3D printed parts it is much harder to answer than for parts from traditional manufacturing industries such as milling, welding, forging or casting. The reason why it is harder to answer is that there is a complete lack of standardized assessment strategies for 3D printed structures that allow for prediction of structural integrity behavior.
Structural integrity assessment strategies are tools which allow for static and fatigue life prediction. Besides a common mistaken belief that structural life behavior is solely simulated, it must be clarified that the structural integrity is assessed based on simulation results via assessment criteria. For structure mechanical problems that means one has to perform a simulation first to determine maximum stresses and then use a proper assessment criteria to evaluate the stresses. Structure mechanical assessment criteria are commonly developed based on extensive experimental tests of materials on micro-, macro-, feature and component size level under all kinds of static and dynamic loading scenarios. Statistical models are then used to further investigate the likelihood of failure for various combinations of loads, material conditions and designs and design features, and based on that, mathematical equations are developed that will predict the maximum allowable stresses in the structure. The complete compilation of all formulas, tables and figures to predict the allowable stresses is referred as assessment guideline. Such assessment guidelines can be developed for any field in industry and quite a broad range of commercial, publicly available assessment guidelines exists for traditional industries. Quite often guidelines are developed for specific applications such as reinforced composites or welded steel and aluminum structures. Some commercial guidelines are for example the FKM Guideline, DVS1608 or DIN 15018. However, currently there is no publicly accesable structural integrity assessment guide available for additively manufactured components. Thus, for now, any serious static and fatigue strength prediction for 3D printed components is based on extensive tests and proper structural integrity prediction models that industrial AM players develop themselves.
There are a few practical reasons why a general structural integrity assessment guideline has not been developed for AM designs yet. First of all, AM is still a fairly new technology and recently found its way to manufacturing of structurally critical components. Ten years ago there was simply no need for such guidelines. Then, the output of 3D printing is not standardized yet. There is still a considerably strong variability in part quality with regard to material properties (e.g E-Modulus) and structural strength (e.g UTS, fatigue limit, elongation at break) depending on the AM machine, it's setting during the print, and post printing treatment. Even though the research has been fundamentally progressed in the last five years and provided better understanding of machine settings, post printing treatments and their effect on printed designs, yet there is no global standard that links the machine settings with the strength of 3D printed designs.
The fact that the growing AM marked is increasingly pushing into high-end applications in automotive-, powertrain- and aerospace industry, will cause an increasing assessment strategy demand, where structural assessment methodologies for traditional manufacturing processes have been well established and widely used.
Structural integrity assessment strategies are tools which allow for static and fatigue life prediction. Besides a common mistaken belief that structural life behavior is solely simulated, it must be clarified that the structural integrity is assessed based on simulation results via assessment criteria. For structure mechanical problems that means one has to perform a simulation first to determine maximum stresses and then use a proper assessment criteria to evaluate the stresses. Structure mechanical assessment criteria are commonly developed based on extensive experimental tests of materials on micro-, macro-, feature and component size level under all kinds of static and dynamic loading scenarios. Statistical models are then used to further investigate the likelihood of failure for various combinations of loads, material conditions and designs and design features, and based on that, mathematical equations are developed that will predict the maximum allowable stresses in the structure. The complete compilation of all formulas, tables and figures to predict the allowable stresses is referred as assessment guideline. Such assessment guidelines can be developed for any field in industry and quite a broad range of commercial, publicly available assessment guidelines exists for traditional industries. Quite often guidelines are developed for specific applications such as reinforced composites or welded steel and aluminum structures. Some commercial guidelines are for example the FKM Guideline, DVS1608 or DIN 15018. However, currently there is no publicly accesable structural integrity assessment guide available for additively manufactured components. Thus, for now, any serious static and fatigue strength prediction for 3D printed components is based on extensive tests and proper structural integrity prediction models that industrial AM players develop themselves.
There are a few practical reasons why a general structural integrity assessment guideline has not been developed for AM designs yet. First of all, AM is still a fairly new technology and recently found its way to manufacturing of structurally critical components. Ten years ago there was simply no need for such guidelines. Then, the output of 3D printing is not standardized yet. There is still a considerably strong variability in part quality with regard to material properties (e.g E-Modulus) and structural strength (e.g UTS, fatigue limit, elongation at break) depending on the AM machine, it's setting during the print, and post printing treatment. Even though the research has been fundamentally progressed in the last five years and provided better understanding of machine settings, post printing treatments and their effect on printed designs, yet there is no global standard that links the machine settings with the strength of 3D printed designs.
The fact that the growing AM marked is increasingly pushing into high-end applications in automotive-, powertrain- and aerospace industry, will cause an increasing assessment strategy demand, where structural assessment methodologies for traditional manufacturing processes have been well established and widely used.
