Increasing Travel Speed Research Articles

Characterization and thermal analysis of laser metal deposited γ-TiAl thin walls

The present work focuses on investigating the effect of process variables (power, travel speed, powder flow rate) on microstructure and mechanical properties of Laser Metal Deposited (LMD) γ-TiAl thin walls. To this end, LMD technique was used to deposit γ-TiAl thin walls at different processing conditions. Microstructures of as-deposited samples were investigated using both optical and scanning electron microscopy. X-ray diffraction (XRD) technique was used to determine the phases present. Microhardness measurements were carried out along both longitudinal and build directions. Microstructural analysis of as-deposited samples revealed a fine lamellar structure comprising of γ and α2 phases. Colony size of 30–60 μm and lamellar spacing between 0.1 and 0.7 μm were observed. XRD analysis confirmed the presence of γ and α2 phases. Comparison of elemental analysis results on both powder and as-deposited samples revealed a negligible loss of Al and no oxygen pick up in the deposited thin walls. Hardness values were found to decrease with an increase in wall height, and hardness values increased marginally (5%) with an increase in travel speed. Further, 3D transient thermal analysis was also carried out to complement the LMD of thin walls in terms of melt pool dimensions and cooling rates. It was found that the melt pool depth (MPDc = 0.266 mm) is smaller at the centre than the edge (MPDe = 0.513 mm) of the wall. Cooling rates decrease with increase in the number of layers deposited.

Control of variable rate system of a rotary tiller based on real-time measurement of soil surface roughness

It is required to employ variable rate (VR) tillage because the soil is not uniform and immense spatial variability is available inside the agricultural fields. A conventional rotary tiller was instrumented to instantly vary the tillage intensity based on the tilled soil surface roughness measurement. The random roughness (RR) was estimated as the standard deviation of surface peaks and depressions which were measured using an infrared sensor. The tilling intensity was adjusted based on rising off and lowering down the tiller soil shield that was controlled by a hydraulic actuator. The soil shield could be adjusted from 0° to 80° in 20° increments with an average response time of 0.26 s. The field tests were performed in order to recognize whether the VR tiller can create predefined soil roughness which was assigned in three ranges of 0.5 ≤ RR1 ≤ 1.5, 1.5 < RR2 ≤ 2.5, and 2.5 < RR3 ≤ 3.5 cm. As a reference, a pin-type profiler was utilized to measure the soil roughness created by the VR tiller. The results showed the soil shield tended to be closer when finer predefined roughness was requested. There were no significant differences in RR over the experimental subplots which received similar adjustments, verifying the tiller performance. The results also showed that different surface roughness could be statistically separated when they were created by the tiller at different travel speeds of 2.6, 3.5, and 4.8 km/h (p < 0.01), because the soil shield tends to be closer when the travel speed increases. The tiller developed in this study could perform VR tillage across the field with an overall success of 83.3%.

Effects of Improving Forest Road Standards on Shortening the Arrival Time of Ground-based Firefighting Teams Accessing to the Forest Fires

In fighting against forest fires, it is crucial for the ground-based firefighting team to reach a fire area in critical response time in which the chance of controlling the fires is significantly high. Road networks are the key infrastructures that provide access to the forest areas for the protection of forest resources. In order to benefit from this important function of roads, especially in forested areas with high natural forest fire risk, they should be built in with adequate technical road standards since the low standards limit the fire truck speed that increases the arrival time of the firefighting team to the fire areas. Most of the forest roads in Turkey are Type-B secondary forest roads with low technical road standards (road width, curve radius, surface materials) that limit the speed of fire trucks. This paper aimed to evaluate the potential contribution of improving the standards of Type-B secondary forest roads in terms of increasing accessible forested areas in critical response time in the case of forest fire occurrence. The study area was Kahramanmaraş Forestry Enterprise Directorate (FED), where forests are sensitive to forest fires at the first degree. In the solution process, firstly, accessible forest areas by the firefighting teams (six teams) located in the study area according to the critical response time were determined by considering the existing road network in the study area. In the second scenario, the possible increase in the accessible forest areas with improved forest road standards and increased travel speed in forest roads was investigated. The results indicated that the areas that can be reached promptly by the firefighting teams in critical response time were 21% and 44% for considering existing roads and improved roads in the whole study area. On the other hand, the accessible forested areas in critical response time increased from 17% to 36% when standards of the forest roads were improved. It is indicated that improving road standards has a significant value to contribute the efficiency of firefighting activities if the practitioners implemented presented methodology.

Impact of travel speed on the microstructure and mechanical properties of adjustable-gap bobbin-tool friction stir welded Al-Mg joints

The butt welds of 4-mm thick 5A06 aluminum alloy plates were produced by adjustable-gap bobbin-tool friction stir travel with travel speeds of 200, 300, and 400 mm/min in this study. The microstructure was studied using optical microscopy and electron backscatter diffraction (EBSD). Tensile tests and microhardness measurements were performed to identify the effect of the travel speed on the joint mechanical properties. Sound joints were obtained at 200 mm/min while voids were present at different positions of the joints as the travel speed increased. The EBSD results show that the grain size, high angle grain boundaries, and density of geometrically necessary dislocations in different regions of the joint vary depending on the recovery and recrystallization behavior. Specific attention was given to the relationship between the local microstructure and mechanical properties. Microhardness measurements show that the average hardness of the stir zone (SZ) was greater than that of the base material, which was only affected slightly by the travel speed. The tensile strength of the joint decreased with increasing travel speed and the maximal strength efficiency reached 99%.

Impact of Increased Travel Speed of a Transportation Set on the Dynamic Parameters of a Mine Suspended Monorail

The method of increasing the efficiency of using one of the most common means of auxiliary transport in underground coal mines—suspended monorails—is presented. Increase of velocity is one of the key parameters to improve the efficiency and economical effect related with the underground auxiliary transport. On the other hand, increasing the velocity results in bigger value of force acting on the suspended monorail route and its suspensions. The most important issue during increasing the velocity is ensuring the required safety for the passengers and not overloading the infrastructure. In order to analyze how increasing velocity influences the level of loads of the route suspension and the steel arch loads, the computational model of suspended monorail was developed. The computational model included both the physical part (embedded in the program environment based on the Multi-Body System method) and the components of the monorail control system. Two independent software environments were cooperating with each other through the so-called co-simulation. This model was validated on the base of results obtained on the test stand. Then, the numerical simulations of emergency braking with different values of velocity were conducted, which was not possible with the use of physical objects. The presented study can be used by the suspended monorail’s producers during the designing process, and leads to increase the safety on underground transportation routes.

Post‐fledging migration and wintering strategies of individual juvenile Lesser Black‐backed Gulls (Larus fuscus)

Research into the patterns and drivers of juvenile migration is important for understanding the development of individual migration strategies. Although several recent studies have tracked adult large gulls throughout the annual cycle, the movements of juveniles remain poorly understood. We fitted Global Positioning System (GPS) devices that transmit locations through the Global System for Mobile Communications (GSM) to ten juvenile Lesser Black‐backed Gulls Larus fuscus prior to fledging on the island of Spiekeroog, Germany, to study their first autumn migration and wintering behaviour. The tracked birds initially departed on similar compass bearings south to south‐west, after which migration routes diverged. Individuals took 38–107 days to reach their wintering sites in Algeria, Morocco or Spain. Birds visited 6.7 ± 3.7 (mean ± sd) stopover sites en route and spent substantial time in northern Europe, with some individuals converging at the same sites over small spatial scales (&lt;1 km), but not over the same time periods. Birds increased travel speeds in the second half of their migration. They showed relatively high site‐fidelity after arrival at wintering sites, and there was no evidence that the size of foraging areas increased over time, suggesting limited exploratory behaviour. Individuals used the same predominant habitats – cropland, open water and built‐up areas – to varying degrees, but showed limited variation in habitat use over time. Overall, the migration routes and timings of juveniles broadly resembled those of previously tracked adults. Given their similar initial bearings and abundance of large gulls on the flyway, we suggest that social learning is likely to be an important process shaping the individual migration and wintering strategies of juvenile gulls.

A study on the effect of substrate heating and cooling on bead geometry in wire arc additive manufacturing and its correlation with cooling rate

Abstract In the present work, the effect of process parameters, substrate heating and cooling on bead geometry during the wire arc additive manufacturing of Inconel 625 on EN 8 steel is investigated. Further, the molten pool thermal history during the deposition was monitored using an IR pyrometer and the effect of these parameters on cooling rate was investigated and correlated with bead geometry. The cooling rate was found to increase with increase in travel speed from 500 mm/min to 700 mm/min while decreased with increase in energy input by varying the applied current between 190 A and 250 A. Though the bead geometry was found to vary with substrate heating, it was found to saturate with increase in current from 190 A to 250 A. Similarly, with increase in current to 250 A, the cooling was found to be ineffective due to increased amount of heat input. Cooling rates were found to effectively indicate these saturation limits which would help in process monitoring and control.

Safety of e-bikes compared to conventional bicycles: What role does cyclists’ health condition play?

IntroductionThe rising use of e-bikes (EBs) presents an opportunity to increase active transportation but may compromise road safety due to increased travel speed and weight compared to conventional bicycle (CBs). Evidence comparing the safety of EBs and CBs is limited while the influence of cyclists’ health status has been neglected. MethodsThis cross-sectional case-control study compared EB and CB users in the Netherlands. Data were gathered 1) through a survey among crash casualties treated at emergency departments aged >16 (N = 2383) and 2) control group data were collected among cyclists without any known crash experience, randomly drawn from a panel of the Dutch population (N = 1860). Using logistic regressions, we assessed the likelihood of crashes and crash severity while adjusting for bicycle use and health status. ResultsEB users had poorer health than CB users, but they were not more likely to be involved in a crash or to sustain more severe injuries. However, older female cyclists did have an elevated risk on EBs and sustained more severe injuries. Health-related factors such as the presence of morbid conditions, medication use, and the body mass index were neither associated with crash likelihood nor associated with injury severity and accordingly did not explain the findings for older females. However, balance and coordination problems, and the use of anti-epileptic drugs were associated with crashes. ConclusionOur findings provide support that EB users have a poorer health status than CB users, while general health status is unrelated to the likelihood and severity of bicycle crashes. EBs enable more vulnerable groups to cycle or keep cycling but, after controlling for bicycle use, EB users are not more likely to be involved in a crash or to sustain severe injuries. As older females run a higher risk on an EB and are more likely to fall while (dis)mounting, we recommend to promote EBs enabling safer (dis)mounting such as by reduced saddle height.

A high-performance WAAM process for Al–Mg–Mn using controlled short-circuiting metal transfer at increased wire feed rate and increased travel speed

Wire Arc Additive Manufacturing (WAAM) is a method for manufacturing high-scale metal objects. This method utilizes recent developments in welding to achieve better performance and higher process rates. Higher performance requires higher metal deposition rates, which implies higher heat input that negatively affects the manufacturing process. In the present study, a high-performance controlled short-circuiting metal transfer process at a wire feed rate of 12 m/min for WAAM with an Al–Mg–Mn alloying system was developed. The arc current and voltage waveforms were studied by oscillogram processing and then modified to reduce the energy input in comparison with a self-regulated gas metal arc welding process. The newly developed process was implemented to manufacture sample parts at a travel speed of up to 150 cm/min. The modified waveforms in combination with an increased travel speed led to a decrease in heat input, which appeared to be 16% lower than that of a conventional self-regulated process. Decreased heat input led to an improved geometry preservation stability at high process rates (up to 2.2 kg/h). Study of the mechanical properties showed that the elongation of the tensile samples was up to 41%. This increase in elongation was explained through macro- and microstructure analysis.

Испытание компенсирующего устройства со встроенным тормозом при проведении мероприятий по плавке гололеда на проводах контактной подвески

Within the framework of strategy for the development of Russia’s railway transport, one of the priorities is the increase in travelling-speed. For the achievement of results, the research of new devices recommended for putting into operation should be done. The new device for compensating tension in contact suspension with built-in brakes DFCB is given consideration in the article as well as its results of operation when performing actions against ice accumulation are analysed.

Loss of elemental Mg during wire + arc additive manufacturing of Al-Mg alloy and its effect on mechanical properties

Elemental Mg is easily evaporated or burnt during welding or wire + arc additive manufacturing (WAAM), and results in a fluctuation of the composition and mechanical performances. Elemental Mg loss during the WAAM of Al–Mg alloy was investigated and the effect of Mg loss on the mechanical properties was discussed based on results from the chemical composition measurement and mechanical properties test. The loss of elemental Mg was non-negligible because of remelting during WAAM, and the loss rate of elemental Mg increased with an increase in current and decreased with an increase in travel speed. The elemental Mg distribution in the WAAM component was uniform, but obvious element enrichment occurred near the fusion zone of the substrate. With an increase in the loss rate of elemental Mg, the tensile strength and average hardness of the WAAM component decreased, whereas the elongation increased. During the WAAM of the Al–Mg alloy, with an increase in the Mg loss rate, the lattice parameters decreased because the solid solubility decreased in the Al matrix during the WAAM.

Effect of Travel Speed on Microstructure and Mechanical Properties of FSW Joints for Al-Zn-Mg Alloy.

The microstructures and mechanical properties of friction stir welded (FSW) Al–Zn–Mg alloy plate under different travel speeds were investigated. Both the average grain sizes (AGSs) of the shoulder affected zone (SAZ), nugget zone (NZ), and the widths of thermo-mechanically affected zone (TMAZ) decreased with the increase of travel speed. Moreover, the AGSs of NZ are always about 60% of that of SAZ at different travel speeds. The fractions of high-angle grain boundaries (HAGBs) in the FSW joints reduce with the distance away from the stir zone (SZ). Furthermore, the initial η’ strengthening precipitates in NZ and TMAZ dissolve and GP zones form during subsequent natural aging, so that the hardness is similar in the two zones. The precipitate evolution in the heat-affected zone (HAZ) at hardness minima are affected by travel speeds, which induce the hardness minima and ultimate tensile strength (UTS) of FSW joints and increase with the increase of travel speed, and a fracture tends to occur at hardness minima location of HAZ during tensile testing.

Ductile fracture based joint formation mechanism during friction stir welding

Material movement during friction stir welding plays a significant role towards joint formation. However, there is little clarity on periodic or continuous nature of material movement. The objective of this work is to understand the mechanism of joint formation during friction stir welding, by investigating the periodic formation of a cavity and if formed, cavity's role towards the joint formation. A two dimensional numerical methodology is developed to capture the material flow around the tool pin. The plastic limit load model is used to predict the formation of microvoids, growth and coalescence. Friction stir welds are made with AA 1050 at different tool travel speeds, for same tool rotation frequency across experiments. Computed tomography of friction stir welded samples is performed to study the size and morphology of the discontinuities. The chemical constituents, size and distance between inclusions are determined from scanning electron microscopy and energy dispersive spectroscopy of the as-received AA 1050. The numerical model suggests that the stress and strain during friction stir welding of AA 1050 is sufficient for nucleation and growth of the voids at the inclusion sites. Further the voids coalesce to form a cavity in all the cases. The incoming material fills the cavity per revolution. However, in some cases the cavity is partially filled which leads to the discontinuities in the weld. For the welds with discontinuities, the area of unfilled cavity is predicted to be larger in advancing side as compared to retreating side. The discontinuity size increases as the travel speed increases. The tunnel discontinuity is predicted by super-positioning of the discontinuities formed over consecutive passes along the feed direction. The discontinuity size and shape trends compare well against the experimental observations. This work would be helpful towards developing strategies for detecting and mitigating the discontinuities formed during friction stir welding.

Long-Term Study on the Cost-Effectiveness of Dust Control and Untreated Aggregate-Surfaced Resource Roads

A long-term study of treated and untreated aggregate resource roads in Canada was conducted. The objective was to investigate the cost-effectiveness of annual dust control treatments where the hypothesis is that annual applications may prolong aggregate life. Seven sections along two road segments with different traffic levels were studied over five years. A survey of road users revealed that 88% agreed that the treated sections were safer because of the increase in visibility and quicker dust settlement times. Evaluation of surface aggregate indicated some aggregate wear but there were no significant differences between treated and untreated sections. The source and quality of crushed aggregate has an impact on road performance. The condition of the running surface did not indicate any major performance differences between the treated and untreated sections. Regardless of treatment, age, or aggregate sources, a general downward trend in Unsurfaced Road Condition Index was observed, indicating wearing course degradation over time. The study revealed a strong correlation between traffic volume and maintenance intensity. Moderately higher travel speeds were measured on the treated versus untreated sections. When the cost of treatment and maintenance was compared with historical costs, the dust control scenario was more expensive. However, when log hauling cost savings from increased travel speeds were introduced, the dust control was approximately cost neutral in low traffic scenarios and moderately better for high traffic. If non-quantifiable benefits, such as increased safety, were to be considered, application of dust control treatment is recommended.

The Role of Material Location on the First Mode of Metal Transfer and Weld Formation in Dissimilar Friction Stir Welded Thin Sheets

Dissimilar materials of 5052-O and 6061-T6 aluminum alloys are friction stir welded by arranging the material location and under various welding conditions. The metal flow phenomenon in friction stir welding comprises two modes of metal transfer. The first mode of metal transfer takes place layer by layer and it is caused by the shearing action of the tool shoulder, while the second mode is caused by the extrusion of the plasticized metal around the pin. The aim of the present study is to understand the metal flow by interchanging the base materials arrangement, namely advancing side and retreating side and its effect on mechanical properties. An image processing technique is used to determine the quantitative amount of the first mode. Effect of first mode of metal transfer on ultimate tensile strength and yield strength have been analyzed. This analysis shows that the first mode of metal transfer increases with increasing travel speed and reveals a substantial relationship between the mechanical properties and the first mode of metal transfer. Material mixing of the joints has been evaluated by using optical microstructure, scanning electron microscopy and energy-dispersive spectroscopy. Results of this analysis show that better material mixing and consequently improved mechanical properties are achieved when 5052 is placed on the advancing side.

Interfacial microstructures and mechanical properties of dissimilar titanium alloy and steel friction stir butt-welds

Dissimilar welding of titanium to steel has received significant attention because of its potential application in power generation and chemical industries. However, it is considered to be very challenging to use fusion-welding processes to join Ti to steel due to their dramatically different thermo-physical properties and chemical compositions. In this work, linear friction stir butt-welding was successfully used to join 2 mm thick sheets of titanium alloy, Ti6Al4 V to medium carbon steel, 30CrMnSiNi2A. Defect-free butt-welded joints were produced using travel speeds from 47.5–75 mm/min with a constant tool rotation speed of 750 RPM. With increasing travel speed, the thickness of the interfacial reaction layer gradually decreases. FeTi intermetallic compound was detected at the interface by micro-XRD testing. An optimal interfacial reaction layer approximately 1 μm thick was formed in the weld made at a travel speed of 75 mm/min. A reaction layer ranging from ∼5 to 60 μm thick was found at the interface with a travel speed of 47.5 mm/min. Such thick reaction layer is in contrast with the thinner layer formed in friction stir lap welds, which is believed to be related to the relatively higher welding temperature of friction stir butt welds. Welds formed at travel speeds ranging from 47.5–75 mm/min exhibit higher tensile strengths than the steel base material and were found to fracture from thermo-mechanically affected zone to heat affected zone on steel side or at the interfacial reaction layer on Ti-side.

Effect of wire and arc additive manufacturing (WAAM) process parameters on bead geometry and microstructure

This paper discusses the effects of process parameters in TIG based WAAM for specimens created using Hastelloy X alloy (Haynes International) welding wire and 304 stainless-steel plate as the substrate. The Taguchi method and ANOVA were used to determine the effects of travel speed, wire feed rate, current, and argon flow rate on the responses including bead shape and size, bead roughness, oxidation levels, melt through depth, and the microstructure. Travel speed and current were found to have the largest effect on the responses. Increasing travel speed or decreasing current caused a decrease in melt through depth and an increase in roughness. Printing strategies were tested using specimens of multiple layers and no significant difference was found between printing layers in the same direction and printing layers in alternating directions. No observable interface between the layers was present suggesting a complete fusion between layers with no oxidation. Three distinct zones were identified within the three- and eight-layer samples. The zones were characterized by the size and distribution of the molybdenum carbide formations within the matrix grain formations.

Seasonal Movement Patterns of Striped Bass (Morone saxatilis) in Their Nonnative Range

Movement dynamics of nonnative species can change in new environments and differ from native populations. It has been more than 100 years since striped bass (Morone saxatilis) were introduced to the Sacramento-San Joaquin River system in California from the US east coast. Acoustic telemetry from 2011 to 2015 was used to examine striped bass seasonal residence patterns in their nonnative range across three regions—bay, delta and rivers, and the effect of fish length and release river (Sacramento River [SR] vs. Feather River [FR]) on movement. In spring, SR striped bass (n = 52) increased travel speed by 39% and river residence by 63% relative to other seasons, which is consistent with spawning migrations. In summer, SR striped bass spent the most time in the bay (mean = 28.2 ± 30.9 days) relative to other seasons and across regions. In winter, 87% of striped bass were detected in the delta over 42% in the bay and 25% in the river. Release river also affected movement behaviors—FR striped bass (n = 11) spent more time in the river in all seasons compared to SR bass. Striped bass with sufficient tag life (n = 17) traveled farther distances in 365 days (mean = 1248 ± 405 km, range: 641–2212 km) with increasing fish length. Seasonal patterns observed appeared to follow seasonal prey sources throughout the San Francisco Estuary. Individual behaviors, however, were highly variable, and this flexibility may be an important trait that has allowed striped bass to persist in their nonnative range.

Metallurgical and mechanical properties of underwater friction stir welds of Al7075 aluminum alloy

Travel speeds between 25–300 mm/min and tool rotational speeds of 800 and 1250 rpm were employed for this study. The microstructure, mechanical properties and fracture surfaces of the joints were studied. Underwater environment and an increase in travel speed significantly increase the precipitates’ volume fraction, reduce the average grain and precipitate sizes of the weld nugget zones. A critical travel speed of 150 mm/min is attained in underwater welds beyond which the average grain sizes remain relatively the same. Average grain and precipitate sizes have linear relationships with the tool rotational and travel speed ratio. Optimum weld strengths of 396 and 360 MPa were obtained in the underwater and air-cooled welds at tool rotational and travel speeds of 800 rpm and 50 mm/min respectively.

Microstructure and Tensile Properties of Friction Stir Processed Mg⁻Sn⁻Zn Alloy.

In this study, as-cast Mg–6Sn–2Zn (wt.%) alloy was subjected to friction stir processing (FSP) and the microstructure and tensile properties of FSP Mg–6Sn–2Zn samples were investigated. It was found that, in the stir zone (SZ) of FSP Mg–6Sn–2Zn samples, α-Mg grains were significantly refined via dynamic recrystallization (DRX) and the Mg2Sn phase was broken and partially dissolved. The microstructure in SZ was nonuniform and DRXed grains in the SZ-up regions were coarser than those in the SZ-down regions. Coarse broken Mg2Sn particles were observed in the SZ-up regions, while only fine Mg2Sn particles were observed in the SZ-down regions. Strong {0001} basal texture developed in the SZ regions of Mg–6Sn–2Zn samples after FSP. The increase of travel speed had little effect on the texture of different SZ regions. The ductility of FSP Mg–6Sn–2Zn samples was obviously improved, while the improvement in strength was negligible when compared to the as-cast sample. The tensile properties of FSP Mg–6Sn–2Zn samples were influenced by grain refinement, texture modification, and the breaking up and dissolution of the Mg2Sn phase.