Adam Mazurkiewicz

Microarchitecture Parameters Describe Bone Structure and Its Strength Better Than BMD

Introduction and Hypothesis. Some papers have shown that bone mineral density (BMD) may not be accurate in predicting fracture risk. Recently microarchitecture parameters have been reported to give information on bone characteristics. The aim of this study was to find out if the values of volume, fractal dimension, and bone mineral density are correlated with bone strength. Methods. Forty-two human bone samples harvested during total hip replacement surgery were cut to cylindrical samples. The geometrical mesh of layers of bone mass obtained from microCT investigation and the volumes of each layer and fractal dimension were calculated. The finite element method was applied to calculate the compression force F causing ε = 0.8% strain. Results. There were stronger correlations for microarchitecture parameters with strength than those for bone mineral density. The values of determination coefficient R 2 for mean volume and force were 0.88 and 0.90 for mean fractal dimension and force, while for BMD and force the value was 0.53. The samples with bigger mean bone volume of layers and bigger mean fractal dimension of layers (more complex structure) presented higher strength. Conclusion. The volumetric and fractal dimension parameters better describe bone structure and strength than BMD.

Study of the behavior of the trabecular bone under cyclic compression with stepwise increasing amplitude

This paper presents the results of a study of 61 trabecular bone samples exposed to a cyclic (1 Hz) compression load. The load was increased stepwise. Characteristic patterns of the hysteresis loop for the middle cycles of successive steps of load and for respective steps of load are presented. Characteristic patterns of secant modulus were also determined. The fatigue life results recorded were compared with the indices of bone architecture determined using micro-CT. Using Pearsons correlation, the best relationship between fatigue life and bone volume ratio (BV/TV) and the maximum load for which there was also reported a maximal value secant stiffness were identified. Based on these findings, it was determined that it is possible to use stepwise increasing load for analysis of the fatigue behavior of trabecular bone.

The Relationship between Trabecular Bone Structure Modeling Methods and the Elastic Modulus as Calculated by FEM

Trabecular bone cores were collected from the femoral head at the time of surgery (hip arthroplasty). Investigated were 42 specimens, from patients with osteoporosis and coxarthrosis. The cores were scanned used computer microtomography (microCT) system at an isotropic spatial resolution of 36 microns. Image stacks were converted to finite element models via a bone voxel-to-element algorithm. The apparent modulus was calculated based on the assumptions that for the elastic properties, E = 10 MPa and ν = 0.3. The compressive deformation as calculated by finite elements (FE) analysis was 0.8%. The models were coarsened to effectively change the resolution or voxel size (from 72 microns to 288 microns or from 72 microns to 1080 microns). The aim of our study is to determine how an increase in the distance between scans changes the elastic properties as calculated by FE models. We tried to find a border value voxel size at which the module values were possible to calculate. As the voxel size increased, the mean voxel volume increased and the FEA-derived apparent modulus decreased. The slope of voxel size versus modulus relationship correlated with several architectural indices of trabecular bone.

Nanomultilayer Coatings Based on Vanadium Nitride

Based on the analysis of the research directions in the field of coatings and layers with special operating properties, the production technologies of composite coatings, including the gradient, multi-layer, and multi-component coatings, should be distinct. The paper presents the results of material properties tests of a multi-layer coating Ti / TiN / TiAlNgradient / (TiAlN/VN)multinano obtained on hot working steel EN X32CrMoV3.3. The preparation of the multilayer coating was specially designed to increase the durability of forging dies in the brass forging process. The authors discuss the results of the microstructure tests for the obtained coatings (STEM+FIB) and present the hardness and Youngs modulus as a function of the distance from the surface (nanoHardness Tester CSM) and the results of adhesion tests carried out using a scratch-test method. The obtained multilayer coatings were also subject to a tribological test using a tribometer tester by DUCOM. The authors indicate that the coatings based on vanadium nitride have very high hardness and Youngs modulus (HV = 32–35 GPa, E = 420–450 GPa), a much lower coefficient of friction in combination with brass than steel, and a lower stability of these parameters at elevated temperatures. According to the authors, the coating represents an interesting material solution to increase the durability of forging dies in the process of brass forging.

Fatigue Energy Dissipation in Trabecular Bone Samples with Stepwise-Increasing Amplitude Loading*

Abstract The research method proposed in the paper assumes multi-level loads of trabecular bone, which are similar to the real ones and demonstrate a step-wise amplitude increase. Throughout the study, such loadings were applied to bone structures sampled from 61 donors. The samples were obtained after hip arthroplasty from the neck fragment of femur heads. All the samples were scanned with a desktop microtomographer. The fatigue damage of the sample structures throughout the experiments was seen in changes in the form of the hysteresis loop recorded in the stress-strain system. The dissipation energy, which is calculated based on the hysteresis loop, is present in the fatigue life function. A three-stage sample fatigue damage pattern was demonstrated. The sum of the dissipation energies was calculated for all the hysteresis loops, and thus we obtain the accumulated dissipation energy, which is referred to as the total fatigue life for all the samples. The calculation results were determined to have an exponential-like curve and reported a high value of the coefficient of determinacy. The accumulated dissipation energy is also related to the value of the compressive stress levels applied. Referring the calculated results of the accumulated energy to the structure index BV/TV, we identified the existence of a strong relationship between the quantities.

Inspection of Crane Rails with Use of Monorail Mobile Platform

Ensuring adequate technical and operational safety of the crane requires, among others, periodic track survey. The inspection of the crane track is to detect defects in the shape of the rail head resulting from plastic deformation and the surface wear as well as cracks in the structure of the rail. An important issue is the possibility of recording and archiving the results of periodic measurements in order to assess the wear of the rails during operation. The developed inspection system enables the determination of the rail profile using the laser scanning method, as well as the assessment of the condition of the rail head surface on the basis of the image recorded by the vision system. The stand-alone inspection system was installed on a mobile platform that traverses the rail. The article presents the developed inspection system and the results of the experimental tests.

Universal Research Instrumentation for Erosion Tests

The research on erosion resistance can be classified into two groups, i.e. standardized research, conducted with specific parameters of the test and dedicated to commercially available products, and experimental studies whose the aim is to investigate different mechanisms of erosion (e.g. micro-cutting, the formation of grooves, fatigue wear, and cracking and chipping of brittle materials) with different parameters of the process, i.e. the angle of impact of the particles, the speed and particle size, the particle temperature, and the temperature of the eroded material. Devices available on the market allow the implementation of erosion tests in accordance with the requirements of the standards. Experimental studies are carried out exclusively on laboratory equipment with incomparable characteristics. The Institute for Sustainable Technologies - National Research Institute in Radom designed and produced a universal testing device enabling investigations both in accordance with the requirements of the applicable standards: ASTM-G76, PN-76/C-81516, PN-EN ISO 16282, as well as experimental research. The device enables the execution of experiments in a wide range of parameters relevant to the processes of erosion, i.e. temperature (≤ 600 °C), the angle of the sample relative to the abrasive particles (25o to 90o), the speed of abrasive particles (10 to 130 m/s) and abrasive particles flow (2 to 10 g / min). In the paper, the authors described the construction of the device and the reported ranges of the erosive wear test parameters and presented examples of the results of tests for selected solid materials and selected coatings produced by PVD methods.

The Influence of Microstructure of Nanomultilayer AlN-CrN-TiN Coatings on their Tribological Properties at Elevated Temperature

One of the most effective ways of shaping the operating parameters of functional elements is to modify the properties of a surface layer using modern technologies of surface engineering. The prospective directions in the development of surface engineering solutions are nanomultilayer coatings that enable effective shaping of surface layer properties. A very important factor in designing properties of PVD coatings, apart from their chemical composition, is their microstructure.The paper presents the influence of the microstructure of the nanomultilayer AlN-CrN-TiN coating on their tribological properties at elevated temperatures. The research methods were concentrated on the analysis of mechanical properties, microstructure, and tribological properties at increased temperatures. The studies on mechanical properties included tests on hardness using the nanoindentation method and tests on adhesion using the scratchtest method. The analysis of microstructure was performed using scanning microscopy. The tribological properties at high temperature were examined using the ball-on-disc method. The authors indicate that the AlN-CrN-TiN layers are characterised by excellent mechanical properties and tribological resistance. In this paper, the authors confirm that the microstructure of a nanomultilayer coating is important in shaping the mechanical and tribological properties of a PVD coating.

The Study on Erosive and Abrasive Wear Resistance of Different Multilayer Coatings Obtained on Titanium Alloy Ti6Al4V

One of the areas in which increased durability is of particular significance is the use of machine elements in conditions of intensive exposure to erosive wear, for example, turbine blades of aircraft engines and power turbines in ventilation systems, and machine elements working in a dusty environment. As it is apparent from the analysis of the state of the art, high possibilities to increase the erosive and abrasive wear resistance of machine elements are created by appropriately designed coatings and layers, especially multilayer coatings composed on the base of materials with different plasticity properties. This is associated with particular characteristics of this type of multilayer coatings that allow the absorption of external energy reaching the surface without causing permanent damage to the coating, while significantly reducing the erosive wear rate.The article presents the results of material research and the results of erosion test of three different materials solutions of surface engineering, i.e. multilayer coatings (Cr / CrN) x8, (TiN / ZrN)multinano and a (Ti-Al) intermetallic / AlCrTiN hybrid layer, obtained on titanium alloy Ti6Al4V. The (Cr / CrN) x8 and (TiN / ZrN)multinano multilayer coatings were obtained by arc evaporation, and the (Ti-Al) intermetallic / AlCrTiN hybrid layer was prepared using a hybrid technology combining diffusion saturation in aluminium powders and arc evaporation in a single technological process. The selected material solutions of the surface layer were subjected to the analysis of the structure by scanning electron microscopy (Hitachi 3000). Measurements of hardness and Youngs modulus were conducted using the nanohardness Tester CSM. The results of this study allowed the authors to compare the erosive wear resistance and wear resistance of selected material solutions, and this led to the conclusion that the (Ti-Al) intermetallic / AlCrTiN hybrid layer is the most effective solution.

Mechanisms for the Transfer of Innovative Surface Engineering Solutions to Industrial Practice on the Example of Hybrid Layers

Advanced surface engineering technologies are the basis of the intense technological development in the world over the past several decades. The rapid development of surface engineering resulted in the appearance of many new top layer solutions, such as multi-layer coatings, nanostructured coatings, and hybrid layers, which prove to be very effective in their applications. The production of layers and coatings with complex microstructure and application requirements (related to coated materials, the geometry of the engineered elements, economic viability) create a need for advanced technological and organizational solutions.This article presents a technology of manufacturing a hybrid layer: “nitrided layer + (Cr/CrN) multilayer,” intended to increase the durability of hot forging dies. Based on this example, those surface engineering fields are presented where simultaneous intensive development is necessary to ensure an efficient process of transferring innovative surface engineering solutions to the industry.