Experimental and numerical assessment of two reconstructive techniques for the fragility fractures of the pelvis type Ia

in Medical Engineering and Physics (2024), 119

Anterior pelvic ring fractures are common in geriatric patients. The Supraacetabular External Fixator (SEF) is a relatively simple and effective surgical procedure. On the other hand, there is the option ... [more ▼]

Anterior pelvic ring fractures are common in geriatric patients. The Supraacetabular External Fixator (SEF) is a relatively simple and effective surgical procedure. On the other hand, there is the option of a Subcutaneous Iliopubic Plate (SIP) osteosynthesis. Only limited comparative biomechanical data of these two devices are available. Therefore, this biomechanical study’s objective was to compare the stabilizing effect of the SEF versus the SIP in a model of Fragility Fractures of the Pelvis (FFP) type Ia. A test stand for pelvic biomechanics testing that emulates the gait loading cycle with physiological relevance was used. The osteotomy on the right pelvic ring was stabilized either with the SEF or the SIP. Strain gauges were used to measure strain in the pelvic ring. The osteotomy’s spatial interfragmentary displacement (SID) was monitored using a 3D digital image correlation system. The SEF stabilization reduced the SID by approximately 10%, whereas the locking SIP could reduce displacement by about 62%. Additionally, the SIP reduced the stress/strain levels by 67% in the posterior pelvic ring. We could demonstrate that the SIP is superior to SEF in treating FFP type Ia as it significantly reduced the osteotomy’s SID and the strain in the posterior pelvic ring. [less ▲]

Developing a Biomechanical Testing Setup of the Pelvis, Part I - Computational Design of Experiments

in Journal of Biomechanical Engineering (2023)

Biomechanics of the human pelvis and the associated implants are still a medical and engineering debated topic. Today, no biomechanical testing setup is dedicated to pelvis testing and associated ... [more ▼]

Biomechanics of the human pelvis and the associated implants are still a medical and engineering debated topic. Today, no biomechanical testing setup is dedicated to pelvis testing and associated reconstructive implants with accepted clinical relevance. This paper uses the Computational Experiment Design procedure to numerically design a biomechanical test stand that emulates the pelvis physiological gait loading. The numerically designed test stand reduces the 57 muscles and joints' contact forces iteratively to only four force actuators. Two hip joints' contact forces and two equivalent muscle forces with a maximum magnitude of 2.3 KN are applied in a bilateral reciprocating action. The stress distribution of the numerical model of the developed test stand is very similar to that of the numerical model of the pelvis with all 57 muscles and joint forces. For instance, at the right arcuate line, the state of stress is identical. However, at the location of superior rami, there is a deviation ranging from 2% to 20% between the two models. The boundary conditions and the nature of loading adopted in this study are more realistic regarding the clinical relevance than state-of-the-art. The numerically developed biomechanical testing setup of the pelvis in this numerical study (part I - Computational Design of Experiments) was found to be valid for the experimental testing of the pelvis. The construct of the testing setup and the experimental testing of an intact pelvis under gait loading is discussed in detail in part II - Experimental Testing. [less ▲]

AUSLEGUNG eines BIOMECHANISCHEN TESTSTANDES für das BECKEN einschließlich der MUSKELKRÄFTE des GANGZYKLUS

Scientific Conference (2022, October 28)

DESIGN OF BIOMECHANICAL TESTING DEVICE FOR THE PELVIS INCLUDING GAIT MUSCLE FORCES

Scientific Conference (2022, June 27)

Influence of UV Ageing on Properties of Printed PLA Containing Graphene Nanopowder

in Materials (2022), 15(22), 8135

The present paper analyses the properties of printed polylactic acid (PLA) samples with admixtures of graphene nanopowder (GNP) at wt. 1%, 2% and 4%. The pure polylactide and admixed polylactide printed ... [more ▼]

The present paper analyses the properties of printed polylactic acid (PLA) samples with admixtures of graphene nanopowder (GNP) at wt. 1%, 2% and 4%. The pure polylactide and admixed polylactide printed samples were examined to determine their chemical-physical properties, stiffness, and strength parameters. The tests of tensile, dynamic mechanical analysis (DMA), difference thermogravimetric (TG), and differential scanning calorimetry (DSC) were executed before and after UV (ultraviolet) treatment. The first part of the paper shows the process of manufacturing granulates and filaments mixed with graphene. The second part of the paper concerns the results of the tests made on printed samples. The analysed samples were printed using a Prusa i3 MK3 printer. It transpired that the content of graphene at 1% improved the mechanical parameters of the printed composite by organising its structure. Increasing the amount of graphene caused the values of the measured parameters to drop. This research indicates how important it is to determine the optimal values of nanoadditives in biopolymers. [less ▲]

Biocomposites with Epoxy Resin Matrix Modified with Ingredients of Natural Origin

in Materials (2022), 15

This study aims to present various forms of cellulose, whose shape depends on the source of origin, and to demonstrate the differences in the influence on the properties of materials produced with its ... [more ▼]

This study aims to present various forms of cellulose, whose shape depends on the source of origin, and to demonstrate the differences in the influence on the properties of materials produced with its participation. For this purpose, composites with various plant additives have been designed and obtained. Some of them have undergone chemical and pyrolytic modifications. The results of the mechanical, physicochemical and microscopic tests showed differences in cellulose structure, even in the case of very similar sources, and its diversified influence on the characteristics of the obtained materials. The research shows the effect of the use of natural additives and their modified versions on the mechanical properties of the composite based on epoxy resin. It turns out that cellulose modifiers are not only fillers that reduce the price of the final product but can also increase some mechanical properties, e.g., compressive strength, which is an additional advantage and a reason for wider use. The potential of natural resources is not yet fully understood. Relatively recently, people have started to be interested in cellulose on a nanometric scale, as it turns out that it can exist in several different forms with interesting properties. [less ▲]

INVESTIGATING THE INFLUENCE OF PERSONALIZED MUSCULOSKELETAL MODELS ON THE CALCULATED STRESSES IN THE PELVIC RING

Poster (2021, September)

This study investigates the influence of personalizing musculoskeletal models (MS) on muscles, contact joints forces and on stresses in the pelvic ring bones during normal gait loading cycle. All ... [more ▼]

This study investigates the influence of personalizing musculoskeletal models (MS) on muscles, contact joints forces and on stresses in the pelvic ring bones during normal gait loading cycle. All calculated forces are utilized to predict stress states in pelvis bones using Finite Element (FE) software. Customized MS models provides more precise muscle and contact forces. Additionally, it enables more automatic coupling between MS and FE environments by data transfer. [less ▲]

Practical Implementation of Functionally Graded Lattice Structures in a Bicycle Crank Arm

in 850th International Conference on Science, Technology, Engineering and Management (2020, November 25)

Functionally graded lattice structures (FGLS) were studied thoroughly for the past years, mostly focusing on specific synthetic tests in the context of additive manufacturing while rarely being actually ... [more ▼]

Functionally graded lattice structures (FGLS) were studied thoroughly for the past years, mostly focusing on specific synthetic tests in the context of additive manufacturing while rarely being actually applied outside of this specific domain. This paper examines a way to practically implement them in a commonly used appliance and study their potential for its improvement. A bicycle crank arm was chosen for this purpose, and a solid aluminium reference model (Shimano FC-R450-453) is used as a performance baseline. The novel design is composed of a hollow body containing a beam-based, non-stochastic, functionally graded lattice structure and is planned to be manufactured on a Markforged Metal X system using 17-4 PH stainless steel. It aims to increase the total stiffness under EN ISO 4210-8 norm loading conditions compared to the reference model while limiting mass and stress values to acceptable degrees. Two crank arm variants, containing a face-centred cubic (FCC) and re-entrant auxetic lattice respectively, are optimised by locally altering their beam radii in eight separate regions. The displacement at the load application point is minimised using Altair OptiStruct and HyperStudy. The reference crank, weighing 213g, exhibits a deflection magnitude of 7.1mm in the most demanding load case while the newly designed and optimised versions only showed displacements of 2.52mm (FCC lattice, 340g) and 2.58mm (re-entrant lattice, 339g) respectively. In addition, the stress distribution was significantly enhanced compared to the reference model, as the latter would not pass the fatigue tests required by the norm. This demonstrates that FGLS, in combination with high-strength materials and additive manufacturing, can increase the performance of many parts, although in this case, with a trade-off in terms of its mass. In future projects, it might be considerably reduced by utilising alternative lattice types lattices or other materials while preserving the benefits of FGLS. [less ▲]

Optimization assisted redesigning a structure of a hydrogen valve: the redesign process and numerical evaluations

in International Journal on Interactive Design and Manufacturing (2020)

This study introduced the redesign process of an automotive hydrogen valve. The process relied on the structural optimization approach, which used to build up the new valves having promising stiffness and ... [more ▼]

This study introduced the redesign process of an automotive hydrogen valve. The process relied on the structural optimization approach, which used to build up the new valves having promising stiffness and the lowest possible weights. To achieve the goals, the study was proposed to be taken place via the three main stages. These stages included topology optimization, lattice optimization, as well as numerical evaluations. The achieved results firstly indicated that the two newly designed valves possessed longer life and lower mass than the original valve. Especially, the topology optimized one could withstand more than 5E4 working cycles in the pre-treated condition before the first crack would be nucleated. The results also pointed out the influences of the pre-treatment pressure on the fatigue performance of the hydrogen valve. Within the examined ranges of the pressure, increasing the pressure’s magnitudes tended to shorten the fatigue life of the topology optimized valve. Additionally, the results highlighted the impact of the employed materials on the estimated fatigue life of such a non-treated structure. In the highlights, the considered steel valves could function normally far beyond 1.5E5 working cycles while the aluminum valves would have an initial crack formation prior to reaching 3E3 cycles. The results also suggested that further practical evidence is needed to not only confirm whether the selected printed aluminum is among the promising candidate materials of the hydrogen valve but also to support the described evaluations. [less ▲]

Designing an early failure indicator channel for an in-tank hydrogen valve via a fatigue-based approach

in Journal of Computational Design and Engineering (2020)

This study introduced a fatigue-based approach to design and implement an indicator channel into an in-tank hydrogen valve. It was aimed at providing a mean to point out multiple early valve’s damages. To ... [more ▼]

This study introduced a fatigue-based approach to design and implement an indicator channel into an in-tank hydrogen valve. It was aimed at providing a mean to point out multiple early valve’s damages. To achieve the goal, the study was proposed to handle via three main phases. They included (i) the risk point determinations, (ii) the new valve design and the crack nucleation life estimations, as well as (iii) the simplified crack growth analyses. The obtained results firstly highlighted the construction of the test channel (TC), whose branches were located close to the predicted damage’s sites. The damages could be identified either when a crack reaches the TC (then forms a leakage) or indirectly via the crack propagations’ correlation. The results also pointed out that the TC-implemented valve could perform as similarly as the non-TC one in the non-treated condition. More importantly, this new structure was proved to have a capacity of satisfying the required minimal life of 1.5E5 cycles, depending on the combined uses of the specific material and the pre-treatment, among those considered. In addition, the results emphasized the complexity of the TC that could not be formed by the traditional manufacturing process. Hence, direct metal laser sintering was proposed for the associated prototype and the final TC was issued based on the fundamental requirements of the technique. Finally, it was suggested that practical experiments should essentially be carried out to yield more evidence to support the demonstrated results. [less ▲]