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Levodopa-associated motor fluctuations and dyskinesia in patients with Parkinson's disease (PD) are often difficult to control by the oral administration of levodopa. Continuous infusion of a levodopa/carbidopa intestinal gel (LCIG) may represent a feasible treatment option for this patient population. To start LCIG infusion, a temporary nasoduodenal/nasojejunal tube should be considered to show that the patient responds favorably, before a permanent percutaneous endoscopic gastrostomy with jejunal tube (PEG-J) is placed. The present review focuses on recently published key studies on the efficacy and safety of LCIG treatment in advanced PD. The results provide robust evidence of a marked reduction of OFF-fluctuations and dyskinesia, thereby also improving the quality of life of these severely disabled patients. LCIG treatment is therefore a promising alternative to continuous subcutaneous apomorphine infusion or deep brain stimulation in advanced PD patients with severe motor fluctuations. [ABSTRACT FROM AUTHOR]

A procedure to estimate thermo-mechanical fatigue crack growth (TMFCG) rates in a coarse grain nickel-based cast alloy is presented. The implemented model relies on the linear accumulation of temperature dependent and independent crack growth contributions. Isothermal fatigue and creep crack growth experiments were performed to generate the model data base. To quantify oxidation damage, the formation of subsurface γ′-depletion was measured. For validation, TMFCG experiments on corner-crack specimen were conducted. The model gives reasonable estimations for the crack growth of an initial defect. Furthermore it allows the assessment of the causes of the crack growth and associate them to crack propagation characteristics observed from the crack path. [ABSTRACT FROM AUTHOR]

The estimation of crack growth (CG) in conventionally cast nickel-based superalloys is of particular interest, since their low ductility and large grain size makes them prone to quasi-brittle fracture. Components made from this material class are often subjected to complex thermo-mechanic fatigue (TMF) loads. CG-testing under TMF loads is expensive and not yet standardized. In addition, many damage mechanisms contribute to the crack growth process under TMF conditions. Nevertheless the need for validated crack growth estimations increases with the demand for flexible load cases. In this work, isothermal and TMF fatigue CG test data of the nickel-based cast alloy C1023 are described by a linear-accumulative CG-model. In this model, fatigue crack growth is treated as temperature-independent. Additionally, two temperature-dependent CG-contributions from creep crack growth and through oxidation damage are considered. γ′-depletion caused by surface oxidation was found to play a dominant role. By dissecting given load cycles into time steps, a revised calculation procedure was implemented to realize estimations for isothermal and thermo-mechanical crack growth, independent from the cyclic time-temperature evolution. The procedure is validated against a variety of CG-experiments, including various TMF-tests with and without hold times. It is also possible to assess the crack evolution and the dominant driver of crack propagation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Importance of thermal/geometric features of composite structures to effective thermal conductivity is studied. • Effective thermal conductivity is correlated with the features using machine learning. • Using a machine learning model, composites are classified based on the existence of percolation path. • Volume fraction of particles and interface thermal resistance are most influential parameters on effective thermal conductivity. Data-driven thermal and percolation analyses are conducted to elucidate the effects of various characteristics on the effective thermal conductivity of complex 3D composite structures. These characteristics include the thermal and geometric properties of the composite constituents, the interface resistance, and the existence of percolation paths. A series of voxel-wise microstructure samples with various characteristics are generated. Their effective thermal conductivities are evaluated using a diffuse-interface-based computational homogenization method. A voxel-based algorithm is employed to identify the potential percolation paths in the structures. The homogenization results show particularly significant effects of the percolation path in composite samples with higher aspect ratios and interface resistances. The importance of different thermal and geometric features to the effective thermal conductivity is analyzed using a data-driven sensitivity study. The analysis also demonstrates that the particle volume fraction and interface thermal resistance are the most influential characteristics for determining the effective thermal conductivity. Finally, employing a surrogate-based classification model, microstructures with and without percolation can be distinguished with an accuracy of 93%. [ABSTRACT FROM AUTHOR]

The use of magnesium alloys has enormous potential in terms of weight saving, resource availability and sustainability. This contrasts with the need to protect the surface from wear and corrosion, which is necessary to increase the depth of application of this promising material in industrial applications. The general requirements for the surface protection and surface functionalization can be fulfilled in particular by PVD coatings. However, so far there are no industrial PVD coatings available that meet the requirements for corrosion protection of the magnesium substrate. Common PVD coatings cannot be applied to magnesium due to the risk of severe galvanic corrosion between substrate and coating. In previous studies, TiMgN was identified as a prospective layer material for the corrosion protection of magnesium alloys as well as for the functionalization of the surface with regard to wear resistance and decoration. In the present work, the TiMgN coating concept has been applied to an industrial 4-cathode magnetron sputter unit of the type Cemecon CC800/9-HiPIMS. As substrate material the magnesium alloy AZ31hp was used. In addition to pure TiMgN, the rare earth elements Y and Gd were alloyed to the TiMgN coating in order to improve the corrosion properties. The influences of coating composition, target design and sputtering mode ( D irect C urrent — DC and Hi gh P ower I mpulse M agnetron S puttering — HiPIMS) were examined with regard to the chemical, mechanical and structural properties as well as the corrosion properties. It will be shown, that the corrosion properties of the TiMgN coated magnesium alloys depend significantly on the deposition conditions and on the coating microstructure, while the defect density seems to be of minor influence. Alloying of Gd to the coating leads to a further increase in corrosion resistance to more than 300 h in the salt spray test, while alloying of Y shows no positive effect. [ABSTRACT FROM AUTHOR]

The growth of short cracks in round bar specimens with a circumferential notch has been investigated by an extensive experimental study. This specific specimen geometry has been applied to determine notch support based on a reduced crack growth rate due to the induced stress gradient compared to situations without a notch. At the same time, this investigation of crack growth in low cycle creep-fatigue conditions reveals a significant influence of dwell times on crack closure, which is discussed in detail in this paper. Therefore, a fracture mechanical approach based on an elastic-(visco)plastic crack growth simulation is used to compute the cyclic effective fatigue and creep crack tip loading. The crack growth rates are then determined by a Paris and Nikbin–Smith–Webster model. All investigations are based on strain controlled conditions at different loading levels. The shape of the applied cycles is trapezoidal, having a dwell time of three minutes at maximum and minimum load, and is symmetric in tension and compression. It turns out that a separate consideration of crack opening and closure reveals an important difference in effective crack tip loading range and therefore has a significant impact on fatigue crack growth. Moreover, this paper shows that the effect of dwell times is linked to the influence on plasticity induced crack closure and to the stress relaxation during the dwell time in compression, yielding less crack closure. • Impact of creep in dwell times on plasticity induced crack closure. • Effectiveness of crack tip loading by cyclic J -Integral. • Crack growth simulation with elastic–viscoplastic behavior. • Analysis of contact stresses along crack flank. • Application and comparison of different crack closure criteria. [ABSTRACT FROM AUTHOR]

• Accumulative prediction of preload loss due to self-loosening in bolted joints. • Standardized experimental characterization of bolted joints. • Handle variable amplitudes caused by vibration and overload peaks. This paper presents a new method to experimentally characterize the rotational self-loosening behavior of bolted joints. Furthermore, a method to calculate the preload loss due to certain relative displacements of the clamped parts was developed. The method obtains all required calculation parameters from the experimental tests performed and neither needs further experimental determination of friction coefficients nor numerical simulations to predict the preload loss. The method accumulates the preload loss of load cycles. Thereby, it can be used to estimate the time a machine can operate until a critical amount of preload is lost. Non-linear dependencies of the preload loss to the displacement amplitude and the remaining preload are considered. The calculation method also applies to load cases with variable load amplitudes. This is validated experimentally. [ABSTRACT FROM AUTHOR]

• Grooved round bars are pre-charged with hydrogen for different times t H and then tensioned at a minimum load to failure L H A C . • The resulting circumferential cracks are highly symmetrical and centric. • The minimum pre-load to failure L H A C initially decreases with increasing t H , passes through a minimum and then increases. • The time to failure t F decreases continuously with increasing t H and approaches zero. • The symmetry of the cracks and the results for L H A C and t F can be used to develop a fracture mechanics approach to HAC. This work demonstrates that by performing hydrogen-assisted cracking (HAC) as a function of hydrogen pre-charging time, highly symmetric circumferential cracks can be generated in circumferentially notched or grooved round bars made of high-strength steels, which can be used to study HAC in terms of fracture mechanics. Using the simple-to-perform method, control over hydrogen-assisted crack initiation is achieved by applying low hydrogen pre-charging times and by determining a threshold minimum preload to failure L H A C . The uniaxial tensile testing at L H A C under constant displacement results in a characteristic load-time-curve as well as a high-symmetry circumferential crack for each material investigated in this study. Finally, the minimum preload to failure, the time to failure and the critical crack length are each exhibited as a function of hydrogen pre-charging time and an approach to the application of fracture mechanics with the aim of determining the threshold stress intensity K I H A C is discussed. [ABSTRACT FROM AUTHOR]

• Fatigue strength depends on the nut material, the length of engagement and the level of pre-loading. • More resilient materials lead to a more homogenous load distribution. • Increased fatigue strength by using pre-formed nuts instead of cut nuts. • By means of the effect of load-induced compressive residual stresses enhance the fatigue strength significantly. • Simulations prove the dependency of the fatigue strength on the load-distribution. The fatigue properties of metric steel screws are investigated experimentally regarding the impact of the length of thread engagement, the nut thread type and the nut material. The load capacity of the screw up to fatigue failure depends significantly on the load distribution resulting from the varied parameters by an impact of the applied pre-load. An over-elastic pre-load of the screw-nut connection leads to a significantly higher load capacity due to a homogenization of the load introduction and load-induced compressive residual stresses at the thread root. The numerical simulations for determining the load distribution and the calculation of local stresses and strains lead to a lifetime evaluation. [ABSTRACT FROM AUTHOR]

With the onset of VHCF research, material behavior inconsistent with conventional versions of the Miner rule started occurring repeatedly: instead of decreasing the residual lifetime of a specimen, load cycles just below the so-called endurance limit increase lifetime compared to CA tests even if only the cycles of the highest load step are counted; the low load cycles contribute a negative amount of damage in damage accumulation computations. We give an overview over related observations on carbon steel, martensitic precipitation–hardening steel and aluminum and discuss conditions of occurrence and possible mechanisms. We show experimentally that tensile dwell stresses enhances static strain aging compared to dwelling at zero stress. [Display omitted] • Hypothesis: low load cycles and dwell times may increase residual lifetime of steel and aluminum at room temperature. • A variety of datasets supporting this hypothesis is presented. • Possible causes including strain aging, crack closure and cyclic plasticity are discussed. [ABSTRACT FROM AUTHOR]

The impact of crack closure and environmental effects on the experimental determination of the fatigue crack propagation threshold is a major problem for the assessment of cyclically loaded components, especially at low stress ratios R. In this work, the influence of the experimental procedure and air humidity on d a / d N − Δ K data at different R is discussed. Unlike the results at R = − 1 , the threshold values obtained at R ≈ 0. 8 , i.e. under negligible crack closure levels, show a very small scatter band regardless of the variation of the test parameters and environmental conditions. • Effective data obtained at R ≈ 0. 8 do not depend on the testing method and humidity. • A large data scatter is observed at R ≪ 0. 8 for different test configurations. • Smaller frequencies generate higher Δ K th independent of the test procedure at R ≪ 0. 8. • Massive oxidation at higher frequencies leads to a kink of the d a / d N − Δ K curves at R ≪ 0. 8. • The determination of the long crack Δ K th requires a minimum crack extension. [ABSTRACT FROM AUTHOR]

• Peculiarities of Al alloy temperature-induced localized chemical corrosion are discussed. • Pre-processing procedure of experimental data is developed. • Statistical extreme value analysis is employed for characterization of pit initiation and growth. • The results allow prediction of expected maximum pit sizes after corrosion reaction. Temperature-induced localized chemical corrosion of AA-1050 in anhydrous ethanol is examined experimentally at 105 °C and 110 °C and the generated data is analyzed based on statistical methods. Initiation times are described by a Weibull distribution whereas pit maxima are proven to be drawn from Gumbel parent distribution which is confirmed by modified Anderson-Darling test. Expected values and Gumbel parameters are correlated to reaction times in order to predict maximum pit sizes. Moreover, alcoholate corrosion reaction mechanism is postulated based on published literature and our observations. The statistical methodology can presumably be applied to other fuel-material combinations. [ABSTRACT FROM AUTHOR]