Designing lightweight 3D-printable bioinspired structures for enhanced compression and energy absorption properties

Recent progress in additive manufacturing, also known as 3D printing, has offered several benefits, including high geometrical freedom and the ability to create bioinspired structures with intricate details. Mantis shrimp can scrape the shells of prey molluscs with its hammer-shaped stick, while beetles have highly adapted forewings that are lightweight, tough, and strong. This paper introduces a design approach for bioinspired lattice structures by mimicking the internal microstructures of a beetle’s forewing, a mantis shrimp’s shell, and a mantis shrimp’s dactyl club, with improved mechanical properties. Finite element analysis (FEA) and experimental characterisation of 3D printed polylactic acid (PLA) samples with bioinspired structures were performed to determine their compression and impact properties. The results showed that designing a bioinspired lattice with unit cells parallel to the load direction improved quasi-static compressive performance, among other lattice structures. The gyroid honeycomb lattice design of the insect forewings and mantis shrimp dactyl clubs outperformed the gyroid honeycomb design of the mantis shrimp shell, with improvements in ultimate mechanical strength, Young’s modulus, and drop weight impact. On the other hand, hybrid designs created by merging two different designs reduced bending deformation to control collapse during drop weight impact. This work holds promise for the development of bioinspired lattices employing designs with improved properties, which can have potential implications for lightweight high-performance applications

Multi stages toolpath optimisation of single point incremental forming process

Single point incremental forming (SPIF) is a flexible technology that can form a wide range of sheet metal products without the need for using punch and die sets. As a relatively cheap and die-less process, this technology is preferable for small and medium customised production. However, the SPIF technology has drawbacks, such as the geometrical inaccuracy and the thickness uniformity of the shaped part. This research aims to optimise the formed part geometric accuracy and reduce the processing time of a two-stage forming strategy of SPIF. Finite element analysis (FEA) was initially used and validated using experimental literature data. Furthermore, the design of experiments (DoE) statistical approach was used to optimise the proposed two-stage SPIF technique. Mass scaling technique was applied during the finite element analysis to minimise the computational time. The results showed that the step size during forming stage two have significantly affected the geometrical accuracy of the part, whereas the forming depth during stage one was insignificant to the part quality. It was also revealed that the geometrical improvement had taken place along the base and the wall regions. However, the areas near the clamp system showed minor improvements. The optimised two-stage strategy had successfully decreased both the geometrical inaccuracy and processing time. After optimisation, the average values of the geometrical deviation and forming time were reduced by 25% and 55.56%, respectively

Re-visiting the 'rule of mixture' used in materials with multiple constituting phases: a technical note on morphological considerations in austenite case study

This is a technical note highlighting a method on how to perform averaging the elastic properties. The drawback of the traditional rule of mixture (ROM) is briefly discussed. The technique considers the effect of morphology based on classical continuum mechanics, taking the advantages of fracture mechanics. As an example, a model that simulates the possible configuration of constituting phases commonly found in austenite microstructure is chosen. The result is compared with traditional ROM. It is found that although similar, the result is better due to the stress amplification that is accommodated in the method, unlike the traditional ROM, which merely considers only the volumetric ratio

Integrated ship maneuverability simulation tool for very large crude oil carrier

A good systematic input and output management system is more essential for ship maneuvering simulation to eliminate unnecessary error due to many considered factors such as hull shapes, shallow water, narrow channel, trim in loading and ballast condition, and propulsion system. In this paper, we proposed an Integrated Ship Maneuverability Simulation (SMS) tool to be used in investigating turning circle characteristics of a very large crude oil carrier (VLCC) at 35 degree of rudder angle. The input and output datasets from the surrounding environments of VLCC have been captured using special sensors and converted as input file to the Integrated Ship Maneuverability Simulation tool. The forces and moments acting on the hull which have been induced by propeller and rudder during maneuvering are calculated independently. Then, these forces and moments are integrated to the SMS tool in order to get a total dynamic effect on ship maneuvering performance. The simulation results using SMS tool have been compared with the experimental datasets for validation. From the comparison, the proposed SMS tool has been able to simulate ship maneuvering performance good agreement with the experimental dataset

Influence of silica content on the stabilization of tetragonal zirconia for biomedical applications

Tetragonal phase of Zirconia (ZrO 2 ) attracts more attention when referring to the phase development compared to the monoclinic and cubic phase. Tetragonal phase offers many favorable features such as high chemical and wear resistance, high fracture toughness and hardness. However, tetragonal ZrO 2 is not stable at room temperature, make it having issues in cooling process. The difficulty to maintain tetragonal phase at room temperature was assisted by the reversible process of ZrO 2 . This reversible process that happened at tetragonal to monoclinic phase transition, caused the monoclinic phase alone are presented after cooling process. The transformation of tetragonal to monoclinic is accompanied by the increase in volume, in which can lead to the propagation of cracks. Thus, ZrO 2 ceramic became a brittle material instead of their high fracture toughness and hardness. Silica (SiO 2 ) was introduced as the dopant component to overcome this transformation-induced cracking when ZrO 2 was sintered above 800 °C. An attempt was made in this work to investigate the effect of calcination temperature and SiO 2 concentrations toward ZrO 2 stabilisation by using sol-gel method. The phase transformation of ZrO 2 and its morphology were characterized via X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). From the XRD analyses, it was determined that SiO 2 with 0.5 M concentration has played a crucial role in the stabilisation of tetragonal ZrO 2 . However, both monoclinic and cubic were found when the concentration of SiO 2 is lower than 0.5M

Tailoring 3D star-shaped auxetic structures for enhanced mechanical performance

Auxetic lattice structures are three-dimensionally designed intricately repeating units with multifunctionality in three-dimensional space, especially with the emergence of additive manufacturing (AM) technologies. In aerospace applications, these structures have potential for use in high-performance lightweight components, contributing to enhanced efficiency. This paper investigates the design, numerical simulation, manufacturing, and testing of three-dimensional (3D) star-shaped lattice structures with tailored mechanical properties. Finite element analysis (FEA) was employed to examine the effect of a lattice unit’s vertex angle and strut diameter on the lattice structure’s Poisson’s ratio and effective elastic modulus. The strut diameter was altered from 0.2 to 1 mm, while the star-shaped vertex angle was adjusted from 15 to 90 degrees. Laser powder bed fusion (LPBF), an AM technique, was employed to experimentally fabricate 3D star-shaped honeycomb structures made of Ti6Al4V alloy, which were then subjected to compression testing to verify the modelling results. The effective elastic modulus was shown to decrease when increasing the vertex angle or decreasing the strut diameter, while the Poisson’s ratio had a complex behaviour depending on the geometrical characteristics of the structure. By tailoring the unit vertex angle and strut diameter, the printed structures exhibited negative, zero, and positive Poisson’s ratios, making them applicable across a wide range of aerospace components such as impact absorption systems, aircraft wings, fuselage sections, landing gear, and engine mounts. This optimization will support the growing demand for lightweight structures across the aerospace sector

Formation of titanium oxide by thermal-electrochemical process on the blasted titanium alloys substrate

Titanium oxide is believed as one of the key factors that influence the excellent corrosion properties as well as biocompatibility of titanium alloy. In the present research, thermal-electrochemical anodizing processes were performed in order to form thick layer of titanium oxide on titanium alloys (Ti6Al4V) surface. Oxidation temperature, blasting and anodizing voltage were selected as the evaluated parameters process at the present study. It was observed that temperature plays important role in the formation of oxide layer, where the thickness of the oxide increases significantly as temperature increases. However, for the case of oxide layer formed by thermal oxidation at temperature of 950oC, oxide layer on the non-blasted sample become easily peel off, whereas oxide layer on the blasted sample shows good adhesion properties. In addition, oxide layer on the blasted samples also have thicker layer as compared with oxide on the non-blasted sample. On the other hand, it was observed that further oxidation by anodizing at 43V and 63V create finer oxide layer by the filled up of porosity on the existing oxide layer. However decreasing of oxide layer thickness was also observed after anodizing, which is predicted due to the breaking up the outer oxide layer during anodizing process

Assessment of compressive failure process of cortical bone materials using damage-based model

The main failure factors of cortical bone are aging or osteoporosis, accident and high energy trauma or physiological activities. However, the mechanism of damage evolution coupled with yield criterion is considered as one of the unclear subjects in failure analysis of cortical bone materials. Therefore, this study attempts to assess the structural response and progressive failure process of cortical bone using a brittle damaged plasticity model. For this reason, several compressive tests are performed on cortical bone specimens made of bovine femur, in order to obtain the structural response and mechanical properties of the material. Complementary finite element (FE) model of the sample and test is prepared to simulate the elastic-to-damage behavior of the cortical bone using the brittle damaged plasticity model. The FE model is validated in a comparative method using the predicted and measured structural response as load-compressive displacement through simulation and experiment. FE results indicated that the compressive damage initiated and propagated at central region where maximum equivalent plastic strain is computed, which coincided with the degradation of structural compressive stiffness followed by a vast amount of strain energy dissipation. The parameter of compressive damage rate, which is a function dependent on damage parameter and the plastic strain is examined for different rates. Results show that considering a similar rate to the initial slope of the damage parameter in the experiment would give a better sense for prediction of compressive failure