Insights on metallic particle bonding to thermoplastic polymeric substrates during cold spray

Metallization of polymers using cold spray technology has reached wide consideration in recent years. However, an effective modeling approach to address the deposition phenomena able to assess bonding formation in polymer metallization is still lacking. This study aims to develop a finite element model to simulate the solid-state deposition of metallic particles on thermoplastic polymeric substrates. Single copper particle impact on the Polyether Ether Ketone substrate was modeled using the coupled Lagrangian-Eulerian approach. Emphasis was given to the polymer material properties and substrate thermal history to account for the sensitivity of the physical and mechanical properties of polymers to temperature. Experimental coating depositions were performed to select an optimized set of spray parameters while single-particle impact tests were conducted for model validation. The substrate temperature was measured using an infrared thermal camera and was used to model the sub-surface temperature gradient during gas spray exposure. The proposed numerical model is shown to be capable of predicting various impact features includi mechanical interlocking and the effect of particle velocity fluctuations and temperature gradients on the extent of bonding. Substrate heating was found to have a distinct effect on the correct prediction of particle bonding. The proposed model enables tuning the appropriate processing conditions for successful copper particle adhesion on PEEK polymeric substrates

An Energetic Approach to Predict the Effect of Shot Peening-Based Surface Treatments

Almen intensity and surface coverage are well-known to be the defining parameters of shot peening-based surface treatments. These parameters are directly affected by material properties, the extension of the contact zone, the geometry of the impact pair, as well as the impact rate and velocity. Such intricate relationships have resulted in often dissimilar predictions of shot peening effects even while using an identical combination of Almen intensity and surface coverage. With the fast pace introduction of new generation impact-based surface treatments, there is a need to find a more widespread parameter that would facilitate the direct comparison of all different treatments and relate the main process parameters to the resultant mechanical characteristics. Herein, we propose to use an energy-based parameter to describe the peening process in a more widespread approach, which collectively incorporates the effects of the Almen intensity and surface coverage, as well as the diameter, material, and velocity of the impact media. A set of finite element analyses was developed to demonstrate the correlation of the peening process effects with this energetic approach. Comparisons with the experimental data served as proof of concept, confirming that the proposed method could provide a quite good estimation of the effect of peening parameters on the treated material

nanostructured akermanite glass ceramic coating on ti6al4v for orthopedic applications

Glass ceramics are widely used to enhance the functionality of inert metallic materials typically used for hard-tissue engineering. Biofunctionality of glass ceramics can in turn be significantly b..

Isolating the Role of Bone Lacunar Morphology on Static and Fatigue Fracture Progression through Numerical Simulations

Currently, the onset of bone damage and the interaction of cracks with the surrounding micro-architecture are still black boxes. With the motivation to address this issue, our research targets isolating lacunar morphological and densitometric effects on crack advancement under both static and cyclic loading conditions by implementing static extended finite element models (XFEM) and fatigue analyses. The effect of lacunar pathological alterations on damage initiation and progression is evaluated; the results indicate that high lacunar density considerably reduces the mechanical strength of the specimens, resulting as the most influencing parameter among the studied ones. Lacunar size has a lower effect on mechanical strength, reducing it by 2%. Additionally, specific lacunar alignments play a key role in deviating the crack path, eventually slowing its progression. This could shed some light on evaluating the effects of lacunar alterations on fracture evolution in the presence of pathologies

2018 Proceedings of the International Conference on Trauma Surgery Technology in Giessen

The overarching goal of the gathering was to define a concept for technology design research in Giessen to improve patient outcomes through the design of assistive technology that assists both patients and surgeons. The emerging field of regenerative rehabilitation where trauma patients are treated by methods of regenerative medicine promises great improvements for our field, but clinical success is yet to be realised. The symposium was specifically organised to acknowledge and address these issues

2020 Proceedings of the 3rd International Conference on Trauma Surgery Technology in Giessen

The 3 rd event of the Giessen International Conference on Trauma Surgery Technology on October, the 17th 2020 was hosted on Zoom in accordance with the worldwide corona situation. Dr Mieczakowski, Dr Yu, and Wolfram drafted in 2018 from Jan’s apartment in Bremen the manuscript which was submitted to and approved for funding by the Deutsche Forschungsgemeinschaft (DFG). At that time, we had no idea what substantial changes the conferencing concept would require. This is why we would like to thank again Michele. She first planned this year’s event after the 2019 date and then in the spring of 2020 had to replan for the new situation

Mediating bone regeneration by means of drug eluting implants: From passive to smart strategies

In addition to excellent biocompatibility and mechanical performance, the new generation of bone and craniofacial implants are expected to proactively contribute to the regeneration process and dynamically interact with the host tissue. To this end, integration and sustained delivery of therapeutic agents has become a rapidly expanding area. The incorporated active molecules can offer supplementary features including promoting oteoconduction and angiogenesis, impeding bacterial infection and modulating host body reaction. Major limitations of the current practices consist of low drug stability overtime, poor control of release profile and kinetics as well as complexity of finding clinically appropriate drug dosage. In consideration of the multifaceted cascade of bone regeneration process, this research is moving towards dual/multiple drug delivery, where precise control on simultaneous or sequential delivery, considering the possible synergetic interaction of the incorporated bioactive factors is of utmost importance. Herein, recent advancements in fabrication of synthetic load bearing implants equipped with various drug delivery systems are reviewed. Smart drug delivery solutions, newly developed to provide higher tempo-spatial control on the delivery of the pharmaceutical agents for targeted and stimuli responsive delivery are highlighted. The future trend of implants with bone drug delivery mechanisms and the most common challenges hindering commercialization and the bench to bedside progress of the developed technologies are covered

Fatigue behavior of a low-alloy steel with nanostructured surfaceobtained by severe shot peening

Severe shot peening aimed to generate a nanograined layer over specimens’ surface has been applied by means of standard air blast equipment but using peening parameters essentially different from typical ones. Different experimental processes including microscopy observation, microhardness, roughness and X-ray diffraction measurements have been performed to characterize the treated surface of specimens. The results confirm the generation of a nanocrystallized surface layer. Rotating bending fatigue tests are then performed on smooth specimens to evaluate the effect of the nanocrystallized layer on fatigue strength. The results indicate improvement of fatigue life notwithstanding the specimen’s very high surface roughness: a refinement of the treatment parameters aimed at reducing the roughness is proposed

Application of different fatigue strength criteria on shot peened notched parts. Part 2: Nominal and local stress approaches

Fatigue life prediction for notched components is an essential step within the design process of machines. In the past years different fatigue criteria have been applied for fatigue behaviour assessment of notched components subjected to shot peening treatment. However, due to complexity of the phenomenon, still an agreed set of standard methods for predicting fatigue endurance of shot peened notched parts is not available. In this work a series of recognized fatigue strength evaluation methods are applied on two notched shot peened specimens under different fatigue loading. After having considered the approaches based on fracture mechanics (see Part 1), now the local stress methods and the FKM guideline (which includes both a nominal stress approach and a local stress one) are considered. The results allow evidencing the criteria able to better consider the effect of SP and to underline the critical points related to the application of the mentioned criteria to shot peened parts. In this regard the FKM guideline and the approach based on critical distance theory are found to provide more accurate results. © 2013 Elsevier B.V