Search

Verticality of transcervical hip fractures in young patients is usually connected with typically high-energy fractures which are known as Pauwels type III. Artificial femoral head replacement surgery is mostly not considered for treating femoral neck fractures in such patients. The commonly used devices for the fixation of vertical femoral neck fractures are multiple screws or a sliding hip screw with or without an antirotation screw. Size, location and length of the screws are the most effective parameters in terms of the structural performance of internal fixation implants, but the optimal configuration of the screws is necessary to be investigated to direct the clinical practice. The aim of this study is to compare the biomechanical stability of the standard inverted triangle configuration with the various newly proposed x-crossed screw configurations. FEA simulations carried out in this study demonstrated that using an x-crossed right assembly in treating Pauwels type III femoral neck fractures satisfies the biomechanical stability in terms of maximum von Mises stresses and maximum femoral head displacement. However, in terms of maximum relative neck fracture displacement, the x-crossed-right assembly would not entirely suffice the desired biomechanical stability. Therefore, using an x-crossed screw assembly in treating femoral neck fractures would provide the needed biomechanical stability.

Adult distal humerus fractures are infrequent, yet they account for one-third of all humerus fractures. For the treatment of comminuted and osteoporotic fractures, locking plates are claimed to be biomechanically superior to alternative internal fixing techniques. Treatment remains difficult despite recent advancements and the use of locking plates due to frequent comminution, low bone quality, and limited healing ability in osteoporotic bone. An optimal design of the newly constructed plate and the control model were selected. The biomechanical characteristics of non-osteoporotic and osteoporotic synthetic bone were compared on six models. The biomechanical properties of the new plate were tested and compared on 54 osteoporotic synthetic humerus models. The control models were reconstructive and parallel LCPs. The tests were carried out under static and dynamic axial, lateral and bending loads. Fracture displacements were measured by optical measuring system Aramis. The test model is significantly stiffer for lateral load (p = 0.0007) and for bending load at the moment of model failure (p = 0.0002), while for axial load the LCP model showed greater stiffness (p = 0.0017). During lateral dynamic loading, all three LCP models broke and there was a significant difference compared to the test model (p = 0.0125). The LCP model is dynamically significantly more durable under axial load, while the largest displacements were recorded with the test model (p = 0.029). The displacements induced by all three loads are within the limits that fulfil the parameters of appropriate biomechanical stability. A novel locking plate for extra- articular distal humerus fractures may provide an alternative to the traditional two-plate.

The price of material is an important factor when selecting the additive polymer procedure. In selective laser sintering (SLS), the price can be reduced by the recycling of material, i.e., with different shares of original and recycled material, as well as by the orientation of the product during manufacturing. Numerous tests warn that orientation in the direction of z axis should be as low as possible to reduce the total price of the product. The product also has to satisfy the influence of atmospheric conditions to which it is exposed during its lifetime, i.e., UV radiation and humid environment. UV light, with sun being its most common source, and average humidity in different parts of the world can be approximately from 20% to 90%, depending on time, day and geographic location. In this work, the test specimens have been made of original, mixed and 100% recycled material and then exposed to the influences of UV radiation and water absorption. After having been exposed to atmospheric conditions for a longer time, the mechanical properties of the polyamide products made by selective laser sintering were tested. The results show that exposure to UV radiation reduces tensile elongation at all ratios of recycled material and orientation of 70–90% except in the z direction, while in flexural deformation it is the other way around. The effect of water was observed only between the 7th–14th day of absorption with a decrease in strength until the deformation did not change.

A numerical evaluation of stress concentrations of corroded plate surfaces of small-scale corroded steel specimens is compared with the experimentally estimated ones. Eleven specimens were cut from a steel box girder, which was initially corroded in real seawater conditions. The surface of all corroded specimens was analysed applying photogrammetry techniques, and a statistical description of an idealised corroded surface of each specimen was established. Fatigue lives of specimens are determined from the fatigue tests. Based on experimentally obtained fatigue lives, the stress concentration factors are calculated concerning the ideally smooth specimens. The correlation between the statistical parameters of the corroded specimen surfaces and the estimated stress concentration factors is analysed. Idealised corroded surfaces, converted in graphical format, are then used for the finite element modelling in ABAQUS software, and stress concentration factors are estimated from the finite element results. A convergence study is performed to determine the appropriate finite element mesh density. Comparison between experimentally obtained and numerically estimated stress concentration factors is performed as well as correlation analysis between actual and finite element predicted crack locations.

Background Good clinical outcomes for locking plates as an external fixator to treat tibial fractures have been reported. However, external locking plate fixation is still generally rarely performed. This study aimed to compare the stability of an external locking plate fixator with that of a conventional external fixator for extraarticular proximal tibial fractures using finite element analysis. Methods Three models were constructed: (1) external locking plate fixation of proximal tibial fracture with lateral proximal tibial locking plate and 5-mm screws (ELP), (2) conventional external fixation of proximal tibial fracture with an 11-mm rod and 5-mm Schanz screws (EF-11), and (3) conventional external fixation of a proximal tibial fracture with a 7-mm rod and 5-mm Schanz screws (EF-7). The stress distribution, displacement at the fracture gap, and stiffness of the three finite element models at 30-, 40-, 50-, and 60-mm plate–rod offsets from the lateral surface of the lateral condyle of the tibia were determined. Results The conventional external fixator showed higher stiffness than the external locking plate fixator. In all models, the stiffness decreased as the distance of the plate–rod from the bone surface increased. The maximum stiffness was 121.06 N/mm in the EF-11 model with 30-mm tibia–rod offset. In the EF-7 model group, the maximum stiffness was 40.00 N/mm in the model with 30-mm tibia–rod offset. In the ELP model group, the maximum stiffness was 35.79 N/mm in the model with 30-mm tibia–plate offset. Conclusions Finite element analysis indicated that external locking plate fixation is more flexible than conventional external fixation and can influence secondary bone healing. External locking plate fixation requires the placement of the plate as close as possible to the skin, which allows for a low-profile design because the increased distance from the plate to the bone can be too flexible for bone healing. Further experimental mechanical model tests are necessary to validate these finite element models, and further biological analysis is necessary to evaluate the effect of external locking plate fixation on fracture healing.

Total hip arthroplasty implies proper orientation of both acetabular and femoral components with a range of 25-40° of combined anteversion. The aim of the study was to examine resistance to periprosthetic fracture of the axially loaded cross section rectangular femoral stem (Zweymüller) with respect to different degrees of anteversion, implanted in the artificial bone model, in laboratory conditions. Femoral bone models with implanted femoral stems were divided into 3 groups depending on the degree of stem anteversion (A, control group 13-17°; B, stem retroverted 0°-4°; and C, stem anteverted 26-30°). The amount of axial load leading to periprosthetic fracture (PPFx) of the artificial bone model was determined experimentally for each construct. The results showed that the load at which the PPFx occurred significantly increased with the increase of the endoprosthesis anteversion angle. In our clinical practice, we are often unable to place the acetabular component in an ideal grade of anteversion for intraoperatively determined reasons. The results of this experimental study suggested that increasing rectangular femoral (Zweymüller) stem anteversion lowered the risk of PPFx. This study was limited by experimental design (laboratory conditions, artificial bone) and should be clinically verified., Potpuna zamjena kuka podrazumijeva pravilnu orijentaciju acetabularne i femoralne komponente u rasponu od 25°-40° kombinirane anteverzije. Cilj ovoga istraživanja bio je ispitati otpornost na periprotetski prijelom aksijalno opterećene femoralne komponente endoproteze kuka tipa Zweymüller, pravokutnog poprečnog presjeka s obzirom na različite iznose kutova anteverzije, ugrađene u model umjetne kosti pri laboratorijskim uvjetima. Modeli femura s ugrađenim endoprotezama podijeljeni su u tri skupine ovisno o stupnju anteverzije endoproteze (A, kontrolna skupina 13°-17°; B endoproteza u retroverziji 0°-4°; C, endoproteza u anteverziji 26°-30°). Iznos aksijalnog opterećenja koje dovodi do periprotetskog prijeloma umjetne kosti određen je eksperimentalno za svaki sklop. Rezultati su pokazali da se opterećenje pri kojem je došlo do periprotetskog prijeloma znatno povećalo s povećanjem kuta anteverzije. U našoj kliničkoj praksi često nismo u mogućnosti pozicionirati acetabularnu komponentu u idealan stupanj anteverzije iz intraoperativno određenih razloga. Rezultati ove eksperimentalne studije pokazuju da povećanjem anteverzije pravokutne femoralne (Zweymüller) endoproteze dolazi do smanjenja rizika od periprotetskog prijeloma. Ova studija je ograničena eksperimentalnim dizajnom (laboratorijski uvjeti, umjetna kost) i traži kliničku verifikaciju.

International audience; The aim of this work is to estimate the parameters of elastoplastic and damage laws for nodular graphite cast iron from a cyclic uniaxial test on a dog-bone sample. The paper focuses on the identification of material parameters coupling finite element models and full-field measurements. The gap between the measured and simulated data is used to estimate the quality of the proposed constitutive postulates. Last, a cyclic uniaxial experiment is carried out in a lab tomograph to reveal the damage micro-mechanism. Digital volume correlation is used to measure displacement fields in the bulk of the sample. The correlation residuals are used to detect the damage mechanism occurring in the heterogeneous microstructure of the material.

The effect of sandblasting and sand paper cleaning on the mechanical properties of corroded steel specimens is studied. An experimental assessment of tensile strength of small scale steel corroded specimens is performed. The specimens were cut from a box girder, initially corroded in sea water conditions and later the specimens were subjected to sandblast and sandpaper cleaning. Tension tests are performed to determine the mechanical properties of three groups of specimens, including non-maintained, sandblasted, and sandpaper cleaned, corroded specimen, allowing the estimation of the modulus of elasticity, yield stress, tensile strength, total uniform elongation and n and K strength parameters. Regression equations of the material properties are derived as a function of the degree of corrosion and maintenance actions. It is shown that these two methods of removing corrosion products from the surface of plate specimens have different effects on their mechanical properties and stress-strain relationships. Based on the achieved results a simplified stress-strain curve accounting for the corrosion degradation and maintenance actions is developed, which may be used for structural assessment of ageing marine structures.

The aim of the study was to assess the influence of gap shape on biomechanical results in extra- articular distal humeral fracture: with contact on the posterior part (by anterior gap) and contact on ulnar column (by radial gap). The goal was to examine if and to what extent did displacements decrease in comparison with previously examined parallel gap without bony contact. The finite element analysis on the three different plate constructs was performed, i.e. parallel, perpendicular and newly designed Y shape plate were considered. Displacements were measured on articular surface and gap point. The most visible decrease of maximum displacements in the distal part of the model was detected in the Y plate model with axial loading: in case of anterior gap 58.5% and especially at radially formed gap 60.9%. Similarly, at axial loading, displacement at the analyzed point on fracture gap most significantly decreased in Y plate model (by 49.4%) at posterior bony contact. Moreover, the latter showed displacement decrease by 68.5% at ulnar bone contact. Furthermore, if a longer radial plate than the ulnar one was used, varus stress could have been avoided. Study results suggested that sufficient stability could be ensured with the newly designed Y shape plate.

This paper presents experimental and numerical investigation of elasto-plastic-damage behaviour of aluminium alloys. The experimental procedure includes static and dynamic tensile tests at different strain rates as well as three point bending tests. Numerical modelling of deformation and failure process of the flat specimens is conducted by using non-isothermal elastoplastic damage constitutive model and two-dimensional plane stress finite elements. During the experiment the displacement and temperature distribution on the specimen's surface is measured by digital image correlation (DIC) method and infrared thermography (IR). This has enabled more precise calibration of material parameters in constitutive relations.

Objective The aim of this study was to compare the biomechanical properties of a novel tibial external bone fracture fixator with a circular locking mechanism with standard dynamic axial external fixator. Material and Methods In order to investigate the prototype usability in experimental conditions, a biomechanical study was performed in which 42 polyacetal tubes set in 14 experimental groups and subgroups represented the fractured tibia that were fixed by a standard dynamic axial external fixator and a novel fixator. Displacements under static and dynamic loads were measured, with static ones corresponding to three directions of fragment movement and dynamic simulating the human gait. Analysis was performed in SPSS v13, with significance set at P Results The novel fixator showed biomechanical superiority in “fragments apart” study groups, while the standard dynamic axial external fixator outperformed the novel one in the situations of bending with “fragments in contact” study groups. There were no significant differences in dynamic load, despite better numerical result of the novel fixator. Conclusion The novel fixator is expectedly faster applicable and offers greater extent of external fixation flexibility. Further developments of this model thus seems justified in both construction improvement and on clinical application.

The pipes for water and gas distribution are mainly made of polyethylene. An accurate modelling of the nonlinear and time-dependent material responses of such structures represent a key for the prediction of structural integrity and reliability, as well as their design and optimization process. In the present paper the creep fracture mechanisms by slow crack growth in polyethylene PE100 are investigated, both experimentally and numerically. Experimental tests have been performed on the standard specimen type 1BA and axisymmetrically cracked specimen denoted as a full-notched crack tensile (FNCT) specimen [1]. Based on the experimental results, the primary/secondary creep constitutive model is proposed. It is shown that the crucial fracture mechanics parameter for determination of the lifetime of a PE100 material is steady-state creep C*-integral [2]. In addition, the Failure Assessment Diagram in the form of C*–integral versus time to failure is proposed [1]. Computational algorithm for the integration of the primary/secondary creep constitutive law is derived [3] and implemented at the material point level in the finite element code ABAQUS by using the user subroutine CREEP [4]. In order to check the accuracy of the derived algorithm, the creep simulation on a FNCT specimen is performed. Furthermore, the detailed finite element solutions for the C*-integral values are obtained for a thick-walled polyethylene gas pipe with an external axial surface crack.

International audience; In this paper the nonlinear behavior of nodular graphite cast iron is investigated under in-plane biaxial loading regimes. Multiaxial experiments enable a wide variety of loading paths to be investigated. In the presented study two loading histories are proposed, namely, equibiaxial and " snail " loading paths corresponding to proportional and nonproportional regimes. The center gauge zone of the testing cruciform specimen is observed. Mean strain fluctuations are measured and presented in order to determine the material response for the prescribed biaxial loading paths. For the equibiaxial and snail loading histories finite element model updating will couple 2D-DIC measurements with 3D-FE analyses to calibrate material parameters describing elasticity, isotropic or kinematic hardening.

This paper investigates the behaviour of a receding contact when a cylindrical indenter presses an unbonded layer resting on a substrate. The problem is analysed by using FEM within the scope of the linear theory of elasticity and under the assumption of plane strain. This paper presents new and original results in the analysis of influence of load intensity and indenter geometry on the contact parameters. In addition, in the investigation into material properties a reference analysis was carried out for the case of material similarity between all three bodies, and material properties were subsequently varied for each body. This class of problems shows nonlinear behaviour, with both contact pressure distributions and contact half-widths found to depend nonlinearly on the applied load. The experimental analysis was carried out by employing the digital image correlation method and the ARAMIS 4M system was used. The obtained measurement results show good agreement with the numerical results.

Purpose The aim of the present study was to determine whether plates with only 1 screw pair can be used for Le Fort I fracture management. Good postoperative results motivated the direct application of mandible fixation principles to the fractured midface region without additional experimental research. However, the amount and distribution of the forces in the midface region is different from those on the mandible. Materials and Methods Testing was conducted on plastic anatomic models. The validity of the experimental model was tested before the fixation techniques were compared. Standard miniplates and miniscrews were used for fixation of the maxilla. The model surface strain analysis was conducted using the noncontact object grating method, which enabled the surface strain measurement without direct influence on the measured model. Results In 2 screw pair fixation, the outer screw pair has little effect on the local strain distribution, but it lowers the contact forces along the crack. One screw pair fixation is stable enough for fixation, but it has a greater strain peak at the crack edges. Conclusion Our results showed that 1 screw pair per plate was enough for stable fixation, and 2 or more screw pairs should only be used when the bone fragment at the fracture site cannot sufficiently transmit forces along the crack.

An experimental and numerical study of the cyclic deformation and low-cycle fatigue behaviour of the aluminium alloy AlCu5BiPb–T8 is presented. The experimental program included monotonic tensile tests, symmetric and unsymmetric strain-controlled fatigue tests, fracture toughness tests, as well as fatigue crack initiation and propagation tests. Within the framework of numerical investigations an efficient algorithm for modelling of cyclic plasticity is proposed. This algorithm is implemented into the finite element program ABAQUS and applied to the analysis of a crack growth near the notch. The accuracy of the computational procedure is tested by comparing the computed results with the real experimental data.

Through many stages of development, from conservative to operative treatment, open reduction and internal fixation with dual plating systems are the golden standard for fixation of distal humerus fractures. The plates are placed with a slight offset, posteromedially and posterolaterally. In recent publications, a higher stiffness and strength of osteosynthesis in the parallel plating technique were compared to the perpendicular technique with different plate designs. As noted in previous studies, non-union of the distal humerus usually occurs in the region at the metaphyseal and supracondylar level of radial columns due to varus stresses. Therefore the hypothesis is that in the case of extraarticular methphyseal fractures, which are treated with two plates perpendicular or parallel to form, the radial side of the plate should be longer than the ulnar side in order to prevent varus stresses as the main cause of the distal humeral pseudoarthrosis. Sufficient stability can be ensured with newly designed Y-shaped plate which should have a longer radial arm and be configured to prevent varus stresses. To prove this hypothesis, biomechanical studies at the supracondylar metaphyseal level on the border of the distal humerus diaphysis should be performed., U razvojnom procesu od konzervativnog pa do operativnog liječenja prijeloma distalnog humerusa, otvorena repozicija te unutrašnja fiksacija pločicama i vijcima su se pokazale kao najbolja metoda liječenja. Pločice se postavljaju uz blagi pomak posteromedijalno i posterolateralno. U posljednjim biomehaničkim studijama uglavnom je analizirana i uspoređivana krutost i stabilnost osteosinteze s različitim pločicama u paralelnoj i perpendikularnoj konfiguraciji. Dosadašnja istraživanja su također pokazala da su loši rezultati liječenja prijeloma distalnog humerusa uglavnom posljedica neadekvatnog cijeljenja u metafizarnoj i suprakondilarnoj regiji radijalne kolumne zbog varusnih naprezanja. Stoga je hipoteza rada da kod ekstraartikularnih metafizarnih prijeloma koji se liječe s dvije pločice u paralelnoj ili perpendikularnoj konfiguraciji, pločica na radijalnoj strani treba biti dulja od ulnarne kako bi se izbjegla varusna naprezanja koja su u većini slučajeva glavni uzročnik pojave pseudoartroze distalnog humerusa. Dovoljna stabilnost koštanih ulomaka može se osigurati novodizajniranom Y pločicom koja je konfigurirana na način da ima dulji radijalni krak, čime se znatno smanjuju varusna naprezanja. Da bi se navedena hipoteza dokazala, potrebno je provesti biomehanička istraživanja u suprakondilarnoj i metafizarnoj regiji na prijelazu u dijafizarnu regiju distalnog humerusa.

Aim. Incisional ventral hernia (IVH) formation has a unique biomechanical disturbance which can be described by "early wound failure" mechanism. Therefore, we suggest that stable gastric pentadecapeptide BPC 157 (used in trials: IBD ; now, multiple sclerosis) known to heal various internal and external wounds and muscle injuries and interact with NOsystem (Curr Med Chem 2012 ; 19(1):126-32 ; Curr Pharm Des 2011 ; 17(16):1612-32 ; Curr Pharm Des 2014 ; 20(7):1126-35) rescues IVH in rats. To demonstrate that that rescue of IVH is also a particular NO-system related effect, NOS- blocker L-NAME and NOS-substrate Larginine were also given alone and/or combined. Methods. Wistar Albino male rats underwent ingrained method (Ann Surg. 2004 Jul ; 240(1):179-86.) of early wound failure induction (satisfactory IVH incidence) received medication/kg (BPC 157 (10ug, 0.16ug/mL, 12mL/ day/rat, in drinking water), L-NAME (5mg/day), L-arginine (100mg/day) both intraperitoneally, alone and/or combined ; or drinking water only (controls)) through 14 days. IVH size, cutaneous wound healing (CVH) quality and intraabdominal adhesions (IA) were scored. Results: IVH size was 6.8±4.8mm in controls. BPC 157 exhibited size 0.8±1.9 (vs. control p

Proximal humerus fractures are represented as 4-5% of all fractures, with incidence notably growing with age. Since surgical internal fixation in treatment of proximal humeral fractures is used, fractures of osteoporotic bone and choice of plate for their osteosynthesis represent particular problem. The aim of the study was to test two locking plates: Philos plate with locking screws with determinated direction, and Arthrex plate with poliaxial locking screws, using the finite element method.This study used version 6.10 of Abaqus FEA software package for simulation and fine element analysis of Philos and Artrex plates attached to the osteotomy models of proximal humerus with fracture gap at 0°, 10° and 20° in four types of static load: abduction, adduction, axial compression and flexion. Simulation results of loads in abduction, adduction, axial loads and flexion, were described with the total bone displacement (U) and maximum bone displacement in the fracture gap (Uf).When examining the Philos plate in axial load on the bone with fracture gap angle from 0°, 10° and 20° no significant differences between the results for the displacements were observed. Therefore, results for other loads are related to total displacements of the bone only at the angle of 0°. Given that the results of the total bone displacement and maximum bone displacement in the fracture gap with Artrex plate were mostly higher, for comparison with the results of bone displacement in Philos plate it was taken that total bone displacement and maximum displacement in the fracture gap in Artrex plate represent 100% of the total displacement. Philos plate showed 60.71% for abduction, 76.07% for adduction, 102.24% for axial loads and 79.59% for flexion of total bone displacement in Artrex plate, and 60.48% for abduction, 76.07% for adduction, 96.05% for axial load and 79.96% for flexion of maximum displacement in the fracture gap in Artrex plate.Osteosynthesis for osteoporotic fractures of proximal humerus with Philos plate in computer simulation proved to be more stable than with Arthrex plate.

To investigate the applicability of infrared thermography as a tool for acquiring dynamic yielding in metals, a comparison of infrared thermography with three dimensional digital image correlation has been made. Dynamical tension tests and three point bending tests of aluminum alloys have been performed to evaluate results obtained by IR thermography in order to detect capabilities and limits for these two methods. Both approaches detect pastification zone migrations during the yielding process. The results of the tension test and three point bending test proved the validity of the IR approach as a method for evaluating the dynamic yielding process when used on complex structures such as cellular porous materials. The stability of the yielding process in the three point bending test, as contrary to the fluctuation of the plastification front in the tension test, is of great importance for the validation of numerical constitutive models. The research proved strong performance, robustness and reliability of the IR approach when used to evaluate yielding during dynamic loading processes, while the 3D DIC method proved to be superior in the low velocity loading regimes. This research based on two basic tests, proved the conclusions and suggestions presented in our previous research on porous materials where middle wave infrared thermography was applied.

Tensile strength tests are performed on small scale corroded specimens, so as to derive their mechanical properties. The specimens were cut from a box girder that was initially corroded in real sea water conditions. As a result of the tensile tests the mechanical properties of the specimens are determined, namely modulus of elasticity, yield stress, tensile strength, resilience, fracture toughness and total uniform elongation. Regression equations are derived for the properties as a function of the degree of corrosion degradation. It is identified that those material parameters are influenced by the severity of corrosion degradation.

The present paper evaluates the fatigue life of ductile nodular cast iron EN-GJS-400-18LT with four different microstructures. Characterisation of the graphite morphology and the matrix microstructure is performed on 50 samples for every material type. Tensile stress–strain curves, symmetrical and unsymmetrical stress–strain hysteresis loops, cyclic stress–strain curves, crack resistance curves and fatigue life curves of these four microstructures are obtained. Experimental results show that size, shape and distribution of the graphite nodules has no significant influence on cyclic hardening of the material but they play a great role in the crack initiation and propagation process. It is shown that the larger irregularly shaped nodules reduce fracture toughness and fatigue strength. Furthermore, the results demonstrated that pearlitic phase does not strongly affect fatigue life if its proportion does not exceed 10%. The monitoring of crack length during the tests is performed by an optical method developed in the present work.

This report firstly presents the rule based scantlings and sectional properties of the example ship defined by using the nominal properties of mild shipbuilding steel. It also describes the way of collection of characteristic material specimens of rolled steel plates and bars delivered by the steel manufacturer to the shipyard for to the example ship. Secondly it summarizes the results of tensile testing in the Laboratory for experimental mechanics of the Faculty of Mechanical Engineering and Naval Architecture in Zagreb of plates and bars denoted here as ‘in-built’ material properties for the example ship according to the production plans. The report then reminds on the rule based material properties for acceptance purposes. Next it considers the influence of ‘in-built’ mechanical properties with respect to the rule requirements on local, global and ultimate strength of ships. The report discusses material properties other than yield strength, which participate in the assessment of the overall ship safety such as the weld strength, buckling and fatigue strength, low temperature behavior, corrosion and reliability. The results of the tensile testing of ‘in-built’ materials are then applied to checking of the local, global and ultimate ‘as-built’ strength of the example ship’s hull instead of the ‘as-designed’ strength defined by the nominal material properties. The report at the end discusses the differences between the ‘as-designed’ and the ‘as-built’ hull strength, fatigue life and reliability. It suggests minimization of the hull strength uncertainties by adopting the mechanical properties of ‘inbuilt’ materials. The conclusion supports the stirring idea of this report that in addition to the ‘as-designed’ strength, a ship deserves individualized assessment of the “as-built” ship hull strength based on the measured realistic ‘in-built’ properties.

This paper presents an experimental and numerical study on two different types of the nodular cast iron EN-GJS-400-18-LT. The experimental procedure includes symmetrical and unsymmetrical strain controlled tests on the cylindrical specimens as well as crack initiation and propagation tests on the compact tension and single edged notched specimens. Different loading regimes are applied, and monitoring of the crack length during the tests is performed by an optical system. Within the framework of numerical investigations an efficient algorithm for modelling of cyclic plasticity is examined. Experimental results show that two material types have significantly different the crack behaviour.

Background and Purpose: Human walking has been extensively studied by many investigators and numerous mathematical models of lower limb movements have been developed but few reports have been written about contribution of the upper limbs to the locomotion process. The aim of this study was to investigate the influence of walking speed and effect of the upper limb swing on the trajectory of the whole body mass center, as well as on ground reaction forces during human walking. Material and Methods: An automatized method for determination of the whole body mass center has been established. Gait analysis was performed on 52 subjects using the Elite system and Kistler force platform. The recording of trajectories of characteristic body points on subjects and measurement of ground reaction forces were performed at normal speed walking with natural and emphasized rhythmic upper limb swing and at fast walking speed. The determined mean values of normalized components of trajectory of the body mass center and ground reaction forces were compared. Result and Conclusion: The study showed that components of ground reaction forces and trajectory of the whole body center of mass are influenced by changes in arm swing and gait velocity. Maximum magnitudes of components of ground reaction force increased for normal speed walking with emphasized upper limb swing. The emphasized upper limb swing decreased the magnitude of vertical oscillations of the body center of mass and thus may influence energy expenditure.

The aim of this study was to investigate the influence of the upper limb swing on human gait. Measurements were performed on 52 subjects by using the Elite system with two cameras and a Kistler force platform. The recording of trajectories of characteristic body points on the subjects and the measurement of ground reaction forces have been performed at normal walking and at walking with emphasised rhythmic upper limb swing. The trajectory of the whole body mass centre, central dynamic moments of inertia and ground reaction forces have been calculated for every subject and mean curves of the entire group have been determined for walking with the natural and the emphasised upper limb swing. The determined mean values of normalised mechanical parameters have been compared and differences between the gait with the natural and the emphasised upper limb swing have been described.

The effects of smoothing non-smooth function on estimation of dynamical stability of the periodic response determined in the frequency domain are considered in this paper. For that purpose, a simple single-degree-of-freedom system with piecewise-linear force-displacement relationship subjected to a harmonic force excitation is analyzed. Stability of the periodic response obtained in the frequency domain by the incremental harmonic balance method is determined by using the Floquet-Liapounov theorem. Results obtained are verified in the time domain by the method of piecing the exact solutions and Runge-Kutta integration routine.

In order to reduce damage of the periosteum of the bone the contact surface on the osteosynthetic plates are usually grooved. Here, it was investigated how different kind of grooves influence bending stiffness and dynamic endurance of osteosynthetic plates. Four point bending tests were carried out according ISO 9585 also as three point dynamic bending tests. The results are presented and discussed.