Load Duration Research Articles

Mechanical behavior investigation of rubberized concrete barriers in impact load

Approximately 1.5 million waste tires are produced annually. Waste tires in landfills and stocks cause toxic chemicals to pollute the soil and cause major fires. Waste tires are a global environmental problem. This problem gave an idea of recycling of waste tires instead of landfills and stocks. In this paper, an experimental study is conducted to review the behavior under impact load of rubberized concrete with conventional concrete. Three different mixes were made by adding crumb rubber (0%, 5% and 10%) by volume to the concrete. Nine cantilever column specimens of three type cross section (10x10, 15x15 and 20x20 cm2) were used to investigate the behavior under impact load. The specimens with higher rubberized concrete have longer impact load duration at the initial peak point. Specimens with rubber content become much flexible than normal specimens. Furthermore, the damage level of columns is greater with increasing rubber content. Therefore, the specimens with higher rubberized concrete absorb more impact energy. The barriers with higher rubber content minimize injury and demise when an accidental impact happens. Using concrete with rubber content reduces costs and produces an environmentally sustainable solution.

Nonlinear Creep Amplification Factor Considering Damage Evolution of Concrete under Compression.

Creep affects the long-term deformation of concrete structures. Nonlinear creep further overestimates the safety factor of structures and affects the safety service performance. The coupling of creep and a damage model considering the rate effect is conducive to accurate prediction of nonlinear creep, but the iterative process of strain makes the calculation method more complex. The purpose of this study is to propose a nonlinear creep explicit method that considers the damage evolution of concrete under compression. Two groups of axial compression members with compressive stresses of 0.2 fc and 0.4 fc were made. Considering the law of concrete damage evolution under uniaxial compression, coupled with elastic creep and damage incremental strain, the lower limit of the medium stress level that gives rise to nonlinear creep is analyzed. The concrete nonlinear creep amplification coefficient with a loading age of 28 days and loading duration of 360 days is studied with consideration for the uncertainty of relative humidity and the theoretical thickness of the component. On this basis, the explicit calculation formula of the nonlinear creep amplification coefficient related to the concrete axial compressive strength and stress level is given. The results indicate that the nonlinear creep amplification coefficient increases nonlinearly with an increase in the stress level, and, when the compressive stress level ratio is higher than 0.6, the nonlinear creep amplification coefficient increases significantly; when the stress level is determined, the creep amplification coefficient decreases gradually with an increase in the compressive strength of the concrete. It is suggested that a stress level range of 0.35~0.75 should be used for the study of a nonlinear creep amplification factor under the medium stress state.

Blast wave interaction with structures – An overview

Blast–obstacle interaction is a complex, multi-faceted problem. Whilst engineering-level tools exist for predicting blast parameters (e.g. peak pressure, impulse and loading duration) in geometrically simple settings, a blast wave is fundamentally altered upon interaction with an object in its path, and hence, the loading parameters are themselves affected. This article presents a comprehensive review of key research in this area. The review is formed of five main parts, each describing: the direct loading of a blast wave on the surface of a finite-sized structure; the modified pressure of the blast wave in the wake region of three main obstacle types – blast walls, obstacles, wall/obstacle hybrids; and finally, a brief description of some methods for predicting loading parameters in such blast–obstacle interaction settings. Key findings relate to the mechanisms governing blast attenuation, for example, diffraction, reflection (diverting away from the target structure), expansion/volume increase, vortex creation/growth, as well as obstacle properties influencing these, such as porosity (blockage ratio), obstacle shape, number of obstacles/rows, arrangement and surface roughness.

Durability Assessment Method of Hollow Thin-Walled Bridge Piers under Rockfall Impact Based on Damage Response Surface

Continuous rigid-frame bridges across valleys are often at risk of rockfalls caused by heavy rainfalls, earthquakes, and debris flow in a mountainous environment. Hollow thin-walled bridge piers (HTWBP) in valleys are exposed to the threat of impact from accidental rockfalls. In the current research, ANSYS/LS-DYNA is used to establish a high-precision rockfall-HTWBP model. The rockfall-HTWBP model is verified against a scaled impact test performed in previously published research. A mesh independence test is also performed to obtain an appropriate mesh size. Based on the rockfall-HTWBP model, the impact force, damage, and dynamic response characteristics of HTWBP under a rockfall impact are studied. In addition, a damage assessment criterion is proposed, based on the response surface model, combined with the central composite design method and Box–Behnken design method. The main conclusions are as follows: (1) the impact force of the rockfall has a substantial impulse characteristic, and the duration of the impulse load is approximately 0.01 s. (2) The impacted surface of the pier is dominated by the final elliptic damage, with conical and strip damage areas as the symmetry axis. The cross-sectional damage mode is from compression failure in the impact area and shear failure at the corner. (3) The maximum displacement occurs in the middle height of the pier. The maximum displacement increases with impact height, impact velocity, and rockfall diameter and decreases with the uniaxial compressive strength of the concrete. (4) The initial impact velocity and diameter of the rockfall are the most significant parameters affecting the damage indices. In addition, a damage assessment method, with a damage zoning diagram based on the response surface method, is established for the fast assessment of the damage level of impacted HTWBP.

Maize harvester gearbox design modification for improved fatigue life

The gearbox has the advantage of being able to change the torque and rotational speed according to the gear ratio and has high power transmission efficiency by transmitting power through the contact of the gear pair. When evaluating the strength and fatigue life of a gearbox using a design load or an equivalent load, there is a possibility that the results will be very different from the actual ones. Therefore, in this study, the load duration distribution (LDD) constructed based on the actual workload was used to evaluate the strength and fatigue life of the gearbox reliably. As a result of evaluating the strength and fatigue life of the gearbox using LDD, it was confirmed that the existing gearbox did not satisfy the target lifespan in the operating environment. Therefore, the reasons for these results were analyzed, and design modification was performed based on the analyzed results. As a result of design modification, shaft deflection decreased by rearrangement of the bearings, from an overhung type to a straddle type, thereby improving the fatigue life of gears and bearings. Finally, the load distribution acting on the gear tooth surface was improved through micro-geometry modification of the gears.

Nonlinear forced vibration and dynamic buckling of FG graphene-reinforced porous arches under impulsive loading

Nonlinear forced vibration and dynamic buckling of fixed functionally graded graphene platelet-reinforced (FG-GPLRC) porous arches under impulsive loading are investigated. The porosity coefficient varies along the thickness of arch based on a power law distribution with uniform dispersion of graphene platelets (GPLs) in the whole arch. The FG-GPLRC porous arch is made of closed-cell metal foams whose effective materials properties are determined by the volume fraction distribution of materials together with Halpin–Tsai model. The nonlinear motion equations of the FG-GPLRC porous under impulsive loading are derived by employed Hamilton’s principle, and numerically solved by Runge–Kutta (RK) method combined with the differential quadrature method (DQM). Based on the Budiansky–Roth (B-R) criterion of dynamic buckling, the critical dynamic buckling load of the arch is also determined. Two case studies are conducted to show the determination of the dynamic buckling load of the arch, and good accuracy of the developed method in predicting the critical dynamic buckling load of both shallow and deep arches is also verified. Numerical results show that the nonlinear forced vibration and dynamic buckling of arches are quite sensitive to impulsive load duration. In addition, FG-GPLRC porous arches have significantly higher critical dynamic buckling load when undergoing instantaneous impact loading.

Carbon nanomaterials for drug delivery and tissue engineering.

Carbon nanomaterials are some of the state-of-the-art materials used in drug-delivery and tissue-engineering research. Compared with traditional materials, carbon nanomaterials have the advantages of large specific surface areas and unique properties and are more suitable for use in drug delivery and tissue engineering after modification. Their characteristics, such as high drug loading and tissue loading, good biocompatibility, good targeting and long duration of action, indicate their great development potential for biomedical applications. In this paper, the synthesis and application of carbon dots (CDs), carbon nanotubes (CNTs) and graphene in drug delivery and tissue engineering are reviewed in detail. In this review, we discuss the current research focus and existing problems of carbon nanomaterials in order to provide a reference for the safe and effective application of carbon nanomaterials in drug delivery and tissue engineering.

Insect Wing Buckling Influences Stress and Stability During Collisions

Abstract Flapping insect wings collide with vegetation and other obstacles during flight. Repeated collisions may irreversibly damage the insect wing, thereby compromising the insect's ability to fly. Further, reaction torques caused by the collision may destabilize the insect and hinder its ability to maneuver. To mitigate the adverse effects of impact, some insect wings are equipped with a flexible joint called a “costal break.” The costal break buckles once it exceeds a critical angle, which is believed to improve flight stability and prevent irreversible wing damage. However, to our knowledge, there are no models to predict the dynamics of the costal break. Through this research, we develop a simple model of an insect wing with a costal break. The wing was modeled as two beams interconnected by a torsional spring, where the stiffness of the torsional spring instantaneously decreases once it has exceeded a critical angle. We conducted a series of static tests to approximate model parameters. Then, we used numerical simulation to estimate the reaction moments, angular impulse, and peak stresses experienced by the wing during a collision. When evaluated over the duration of an external load, we found that buckling could reduce reaction moments and angular impulse up to 82% and 99%, respectively, compared to a homogeneous wing. This suggests the costal break can enhance flight stability. On the other hand, buckling maximally increased peak stresses two times compared to a homogeneous wing, indicating the costal break does not reduce likelihood of damage under the simplified loading considered.

Competition Stress Prolongs Exercise Recovery In Collegiate Soccer Players

Athlete conditioning is vital to success in collegiate soccer. Effective conditioning programs incorporate adequate rest between exercise sessions. The duration of an athlete's recovery may be sensitive to variables beyond training load, including emotional and psychological factors. PURPOSE: To determine the effect of competition stress on recovery time in female collegiate soccer players. METHODS: We monitored 30 Division 1 female soccer players for 35 consecutive days. All athletes wore Polar Team Pro devices (Polar Electro Inc., Bethpage, NY), which recorded duration of exercise, total distance covered, kcals burned, number of sprints performed, average and maximum speed achieved, average and maximum heart rate (HR), and Polar calculations of training load, cardio load, and recovery duration in hours. Data were captured for 20 practices and 7 games, resulting in 858 observations. Linear regression tested the effect of formal competition on recovery duration holding constant time of day and all significant workload variables. RESULTS: Players were 20.1 ± 1.1 years of age. Across all practice and competition sessions, the mean duration of exercise was 59.0 ± 38.8 min, total distance covered was 2,518.9 ± 2,074.5 m, and estimated energy consumption was 381.7 ± 284.8 kcals. Athletes performed 5.9 ± 7.9 sprints per session, maintained an average speed of 2.8 ± 1.2 km/h, and achieved a maximum speed of 20.7 ± 7.3 km/h. Average HR was 131.9 ± 24.3 bpm, maximum HR was 177.4 ± 32.7 bpm, training load was 70.1 ± 59.3, and cardio load was 76.0 ± 62.2. Recovery duration was 12.8 ± 15.7 hr following practice sessions and 51.3 ± 59.6 hr following competitions (p < 0.001). Holding constant all significant predictors (time of day, exercise duration, total distance covered, estimated kcals, number of sprints, average speed, average HR, training load, and cardio load), formal competition corresponded to 33.8 additional hours of recovery (p < 0.001; 95% CI of β = 27.7 to 39.9; model r2 = 0.691; adjusted r2 = 0.687). CONCLUSION: Sufficient recovery is a crucial component of optimal performance in collegiate athletics. Our data indicate prolonged recovery duration following formal competition settings, which could not be explained by workload. Further research on psychological contribution to allostatic load is warranted.

Energy matching: exploring the value of demand flexibility in educational office buildings

This research presents a case study exploring the potential for demand side flexibility at a cluster of university buildings. The study investigates the potential of a collection of various electrical devices, excluding heating and cooling systems. With increasing penetration of renewable electricity sources and the phasing out of dispatchable fossil sources, matching grid generation with grid demand will become difficult using traditional grid management methods alone. Additionally, grid congestion is a pressing problem. Demand side management in buildings may contribute to a solution to these problems. Currently demand response is, however, not yet exploited at scale. In part, this is because it is unclear how this flexibility can be translated into successful business models, or whether this is possible under the current market regime. This research gives insight into the potential value of energy demand flexibility in reducing energy costs and increasing the match between electricity demand and purchased renewable electricity. An inventory is made of on-site electrical devices that offer load flexibility and the magnitude and duration of load shifting is estimated for each group of devices. A demand response simulation model is then developed that represents the complete collection of flexible devices. This model, addresses demand response as a ‘distribute candy’ problem and finds the optimal time-of-use for shiftable electricity demand whilst respecting the flexibility constraints of the electrical devices. The value of demand flexibility at the building cluster is then assessed using this simulation model, measured electricity consumption, and data regarding the availability of purchased renewables and day-ahead spot prices. This research concludes that coordinated demand response of large variety of devices at the building cluster level can improve energy matching by 0.6-1.5% and reduce spot market energy cost by 0.4-3.2%.

GeoSPARQL-Jena: Implementation and Benchmarking of a GeoSPARQL Graphstore

This work presents an RDF graphstore implementation for all six modules of the GeoSPARQL standard using the Apache Jena Semantic Web library. Previous implementations have provided only partial coverage of the GeoSPARQL standard. There is discussion of the design and development of on-demand indexes to improve query performance without incurring lengthy data preparation delays. A supporting benchmarking framework is also discussed for the evaluation of any SPARQL compliant queries with interfaces provided for integrating additional test systems. This benchmarking framework is utilised to examine the performance of the implementation against two existing GeoSPARQL systems using the Geographica benchmark. It is found that the implementation achieves comparable or faster query responses than the alternative systems while also providing much faster dataset loading and initialisation durations.

Autumn migrating passerines at a desert edge: Do birds depart for migration after reaching a threshold fuel load or vary it according to the rate of fuel deposition?

Fuel deposition rate is predicted to determine departure fuel load during stopover in two models of optimal behavior of migrating birds. Yet, near ecological barriers, such as wide deserts, birds may switch to a different strategy of departing with just enough fuel to enable the long cross-barrier flight, thus reaching a threshold of fuel load regardless of the rate of fuel deposition. To test these predictions we studied autumn migrating Red-backed Shrikes (Lanius collurio) before they departed for a ∼2,000 km journey across the Sahara Desert. The body mass of fourteen individuals was measured on a daily basis throughout their stopover using field-deployed scales while being tracked by the ATLAS biotelemetry system in the Hula Valley, Israel. Statistical analysis found that the natural log of departure fuel load was positively related to both the capture fuel load and the fuel deposition rate. Hence, the results of this analysis suggest that bird condition at departure depended on the rate of fuel deposition, as predicted by models of time-minimization migration and the minimization of the total energy cost of migration. Departure fuel load and stopover duration were negatively related to each other as birds that remained for a long time in stopover departed with relatively low fuel loads. These findings suggest that even near a wide ecological barrier, departure fuel load is sensitive to the rate of fuel deposition, especially at lower values of fuel deposition rate. Birds that were able to accumulate fuel at higher rates showed a nearly constant departure fuel load and as such we could not exclude the possibility that the birds were trying to reach a certain threshold of fuel stores. Randomized 1,000 repeats of the aforementioned correlation suggest that the correlation between fuel deposition rate and the log of departure fuel load is valid and does not represent a spurious result. Following bird migration simulation using the program Flight, we conclude that fuel loads allowed most individual to accomplish the journey across the desert. Our findings suggest high between-individual variation in stopover parameters with likely consequences for bird migration performance and survival.

Towards the estimation of ultimate compression tolerance as a function of cyclic compression loading history: implications for lifting-related low back injury risk assessment

This study aimed to mathematically characterize the ultimate compression tolerance (UCT) as a function of spinal joint posture, loading variation, and loading duration. One hundred and fourteen porcine cervical spinal units were tested. Spinal units were randomly assigned to subthreshold cyclic loading groups that differed by joint posture (neutral, flexed), peak loading variation (10%, 20%, 40%), and loading duration (1000, 3000, 5000 cycles). After the assigned conditioning test, UCT testing was ­performed. Force and actuator position were sampled at 100 Hz. A three-­dimensional relationship between UCT, loading variation, and loading duration was most accurately characterized by a second order polynomial surface (R2 = 0.644, RMSE = 1.246 kN). However, distinct UCT responses were observed for flexed and neutral postures. A single second-order polynomial most accurately characterized the UCT – loading duration relationship (R2 = 0.905, RMSE = 0.718 kN) for flexed postures. For neutral joint postures, separate second-order polynomial equations were developed to characterize the UCT – loading duration relationship for each variation group (R2 = 0.618–0.906, RMSE = 0.617 kN–0.746 kN). These findings suggest that UCT responses are influenced by joint posture and these data may be used to inform ergonomic tools for the assessment of low back injury risk during occupational lifting.

Effect of Weak Zones on Resilience of Sustainable Surface Course Mixtures of Fresh-Reclaimed Asphalt Pavement

The use of reclaimed asphalt pavement (RAP) is necessary for sustainable and cost-effective road infrastructure construction. This research investigates the effect of the area of weak zones (WZ) on the resilient modulus (MRT) of mixtures of fresh asphalt with 20% RAP. Experimentation on fresh asphalt–RAP mixtures comprising Superpave (SP-A, SP-B) and Asphalt Institute (MS-2) gradations with 20/30, 40/50, 60/70 and 80/100 penetration grade binders was carried out. WZ were determined based on the analysis of magnified digital images of asphalt specimens obtained using optical microscopy. This study demonstrates that the 20/30 grade binder caused an increase in the MRT at 25 °C up to 1.8, 2.9 and 9.2 times for a 0.1 s load duration, and 2.4, 3.0 and 9.7 times for a 0.3 s load duration. In contrast, improvement at 40 °C was observed to be up to 1.9, 3.1 and 9.7 times for a 0.1 s load duration, and 1.9, 3.0 and 12.4 times for a 0.3 s load duration in comparison with 40/50, 60/70 and 80/100 grade binders, respectively. Experimental data were validated by factorial analysis. Power trendline equations were also developed between MRT and WZ to explain the effect of gravel particle orientation on the sustainable resilience of surface course mixtures.

Two-Stage Stochastic Optimization for the Pre-Position and Reconfiguration of Microgrid Defense Resources against Natural Disasters.

With the aggravation and evolution of global warming, natural disasters such as hurricanes occur more frequently, posing a great challenge to large-scale power systems. Therefore, the pre-position and reconfiguration of the microgrid defense resources by means of Mobile Energy Storage Vehicles (MEVs) and tie lines in damaged scenarios have attracted more and more attention. This paper proposes a novel two-stage optimization model with the consideration of MEVs and tie lines to minimize the shed loads and the outage duration of loads according to their proportional priorities. In the first stage, tie lines addition and MEVs pre-position are decided prior to a natural disaster; in the second stage, the switches of tie lines and original lines are operated and MEVs are allocated from staging locations to allocation nodes according to the specific damaged scenarios after the natural disaster strikes. The proposed load restoration method exploits the benefits of MEVs and ties lines by microgrid formation to pick up more critical loads. The progressive hedging algorithm is employed to solve the proposed scenario-based two-stage stochastic optimization problem. Finally, the effectiveness and superiority of the proposed model and applied algorithm are validated on an IEEE 33-bus test case.

A comparison of two manual catching methods of broiler considering injuries and behavior

The aim of this study was to compare the 2 manual catching methods in terms of injuries and behavior. Throughout 12 loadings on practical farms with the same standard, 1 container each was caught using the one-legged (1LCM) and 1 using the two-legged catching method (2LCM). The animals were filmed during loading to evaluate their behavior and subsequently examined regarding injuries. Wing flapping was observed more frequently in broilers caught with the 1LCM than 2 LCM. Carrying animals with neighbors (1 neighbor: P < 0.001; 2 neighbors: P < 0.001) and a grasping position at or above the tarsal joint (P < 0.001; P < 0.054) reduced wing flapping in both methods. A short grasping duration (P = 0.004), settling the broilers into the crate (P = 0.005) and avoiding striking the broilers against the crate (P < 0.001) reduced the occurrence of wing flapping. About 1.1% of 1LCM and 0.43% of 2LCM broilers were diagnosed with an epiphysiolysis. Catching with the 1LCM (P = 0.042), loading in lower crates (low vs. middle: P = 0.005; low vs. high: P = 0.008), a longer catching duration (p = 0.025) and female broilers (P = 0.007) had a higher chance for epiphysiolysis. Broilers loaded in lower crates (P = 0.007) and ones which showed more wing flapping (P = 0.015) had a higher chance for hematomas. A higher loading duration led to a higher risk of hematomas (prevalence: 1.5%) and a prevalence of 1.0% of broilers with severe injury in 2LCM in a simultaneously performed study (mechanical loading vs. 2LCM), in which manual loadings of entire barns were evaluated. This may be caused by fatigue of the workers. In summary, the catching method or number of grasped legs is not the decisive factor, but the compliance and implementation of the identified risks and careful handling of the animals are determining factors to reduce wing injuries caused by loading and wing flapping.

Hydroelectricity Modeling for Low‐Carbon and No‐Carbon Grids: Empirical Operational Parameters for Optimization and Dispatch Models

AbstractHydroelectric power has unusual technical characteristics that could become more valuable as the penetration of variable generation renewables grows, but its use for electricity generation is constrained by complex physical, safety, and socioenvironmental considerations. Hydroelectricity can therefore be difficult to represent in national‐scale energy models, and is frequently presumed to be either overly flexible or inflexible. While a few grid models address this complexity via detailed hydraulic process models, more simplified optimization and dispatch models could benefit from the use of empirical parameter values. In this study, we combine a new data set comprising 7.8 million flow‐hours of data from 2011 to 2016 at 158 dams across the United States with monthly and hourly generation data from the U.S. Energy Information Administration (EIA) to elucidate such empirical constraints for the continental United States. We introduce an approach for estimating power generation from hourly water discharge, then present regionally resolved interannual seasonal and diurnal generation patterns; frequency analyses of ramp rates; minimum and maximum generation rates; daily reversals; and load duration curves, all available interactively with a new data visualization tool. We suggest that due largely to hydropower's role as power generation that also serves non‐energy purposes, it acts as a predictable variable generator with constrained dispatchability, more like a supply side analog to demand response resources than like a battery. This observation is particularly relevant for high penetration renewable energy scenarios, given hydroelectric generators' expected value for grid stabilization and load balancing.

Numerical Modelling of the Effects of Liquefaction on the Upheaval Buckling of Offshore Pipelines Using the PM4Sand Model

The buckling tendency of an offshore pipeline buried in a liquefiable soil aggravates under earthquake situations. Moreover, to understand the upheaval displacement behavior of an offshore pipeline under dynamic loading, it is crucial to understand the variation of liquefaction potential within the soil bed. Thus, in the present study, the variation of the liquefaction potential within the soil body and its effect on the pipeline upheaval displacement (u) and post-shake uplift resistance (Vup) is investigated using a finite element package called PLAXIS 2D. The study was performed for different seismic and soil conditions. To define the soil, two advanced constitutive models are used. The static stages are modelled with the ‘Hardening Soil Model with small strain’ (HSS model), while the dynamic stage is modelled with the PM4Sand model. Moreover, the problem is defined as a 2d plane strain problem. The pipe is considered to be covered with Nevada sand. Several parameters such as a sand-density index (Dr), pipe embedment depth (H), seismic frequency (f) and amplitude are varied to study the variation of the soil liquefaction potential, the pipe upheaval buckling and the post-shake uplift resistance. The model is validated with past studies and a considerable match is obtained. The liquefaction potential is shown using the shadings of a user-defined parameter called a pore water pressure ratio (ru). Moreover, the variation of pipe upheaval displacement (u) and pipe uplift resistance (Vup) are shown using various plots. Thus, it is observed that the liquefaction potential is reduced with an increase in the frequency and the amplitude of the seismic signal. Moreover, the peak upheaval buckling, and the duration of earthquake loading to reach the peak upheaval buckling, decreased with an increase in the earthquake signal frequency. Again, the variation of post-peak uplift resistance of the buried pipeline with the pipe embedment depth is observed to be independent of the signal parameters. However, the variation of uplift resistance of the pipeline with the soil relative density is influenced by the signal parameters.

Surface evolution of vermicular cast iron in ultra-high temperature combustion with different single-pulsing duration

The key components in combustion chamber of high power density diesel engines are apt to be damaged rapidly under abnormal combustion. To investigate the surface damage behavior and evolution mechanism of vermicular graphite cast iron in unsteady combustion, a self-developed plasma thermal shock test method was adopted. And the effect of the single-pulsing duration (0.2, 0.5, 5, and 50 s) of combustion on reciprocating thermal shock characteristics was mainly studied. Results showed that as the sample with the longest loading duration (50 s) exhibited the highest mass gain rate (0.05 mg/s), thickness growth rate (0.096 μm/s), roughness (1.889 μm), and hardness (515 HV). The cumulative thickening and spalling of the oxide layer during the plasma impact is the main cause of the changes in ablation rate and surface roughness. And the bainite phase transformation in the heat affected zone increased the hardness of the material.

Einfluss von Eiskollisionslasten am Propeller auf die Kontaktzustände in den Antriebsstranggleitlagern von Schiffen

Journal bearings in drive trains of ships in Arctic and Antarctic operations show wear and fatigue damage resulting from collision between the propeller and drift ice. The damage requires costly drivetrain maintenance in dry dock, which can be reduced by loadappropriate design and predictive maintenance measures However, this requires a reliable life time calculation of marine drive train bearings subjected to stochastic ice loads. In the following investigations, the influence of different load characteristics of a propeller-ice collision on the contact states in the drive train bearings of ships is investigated in order to be able to estimate the influence of different load characteristics in terms of the development of future life time models. For the investigations, a MBD and EHD model of the drive train of the research vessel SA Agulhas II was built. The results show that the load characteristics “load duration”, “load height” and “load orientation” and the operating parameter “oil temperature” have a high influence on the contact states in the drive train bearings and must be taken into account for future life time calculations.