Hybrid excavator control strategy based on rules optimizes the specific fuel consumption only to determine
engine operating point in the perspective of qualitative analysis, it is not sufficient to ...reduce the excavator fuel
consumption because of ignoring the affect of engine power output. In this paper, an instantaneous minimum fuel
consumption control strategy for hybrid power-train is proposed, strategy determines the ideal operating point taking both
the main influence factors of fuel consumption into consideration, the ultra-capacitor energy variation which is caused by
the motor power output is converted to the equivalent fuel consumption and included in the current power-train fuel
consumption. The output torque combination of the engine and motor which minimize the current fuel consumption is
adopted. The bench test results validate that the engine is 12% fuel saving on average after optimizing, and at the same
time the ultra-capacitor energy is effectively maintained.
Titanium (Ti) alloys, which are highly promising as structural materials in critical industrial applications, generally require high strength and ductility, particularly high fracture toughness. ...However, the conventional approach of enhancing strength through mechanical processing to induce dislocations often leads to a compromised ductility known as the strength-ductility trade-off. Here, we develop a new strategy of the nanocrystallized kinks to overcome this issue in Ti-11V metastable β-Ti alloys via combining industrially used cold forging (CF) and cold rolling (CR) processes. Deformation kinks are firstly activated by CF, and subsequently they are fragmented into nanograins during CR, architecting nanocrystallized kinks in the coarse-grained matrix. This unique microstructure effectively balances the strength-ductility conflict, endowing this Ti-V binary alloy with high yield strength ∼1200 MPa, appreciable ductility ∼17 % and high fracture toughness ∼ 52.0 MPa·m½, which is superior to numerous multielement engineering Ti alloys. This design strategy of nanocrystallized kinks can be extended to other engineering materials, e.g., Mg and Zr alloys, for advanced performance at large industrial scales.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The traction operation of a shipboard helicopter on the deck is a complex force-coupling process involving multiple moving entities. To more efficiently simulate the traction process, this study ...introduces a dynamic model based on the independent modeling of moving subjects (IMMS) method. Initially, the forces on the tire and the articulation part are analyzed, followed by the separate establishment of dynamic models for the helicopter and tractor using the Lagrange equation. Considering the articulated states among the ship, helicopter, and tractor, and according to the active–passive relationships of each entity, a unified solution method is introduced to solve the motion equations sequentially. The model's reliability and real-time performance are subsequently assessed and validated, effectively simulating the helicopter's traction operation procedure. The results reveal that the IMMS dynamic model exhibits high reliability and requires, on average, only 0.5% of the CPU time compared to the conventional dynamic model. The IMMS approach will be useful in advancing research into the modeling of shipboard helicopter traction processes.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Enhancing the mechanical properties and thermal stability of phthalonitrile polymers by hybrid modification holds significant importance in broadening their thermal-structural applications within ...high-temperature environments. Herein, fumed silica nanoparticles were considered as modifiers for a class of phenolic-type phthalonitrile resin, i.e., PN75, and their effects on mechanical properties and thermal stability were explored. First, contact angle tests (CA) were employed to show that the PN75 melt had good wettability on hydrophilic fumed silica (FS) and poor wettability on hydrophobic fumed silica (RFS). FS had a relatively satisfactory dispersion within PN75, which was indicated by scanning electron microscope (SEM), followed by FS/PN75 nanocomposites were prepared by melt blending under vacuum, with maximum FS addition 3 wt% of PN75. Second, the flexural strength and modulus of nanocomposites were increased by 23.5% and 11.9%. Finally, thermal stability of the FS/PN75 was promoted from 21.6% to 25.6% in char residue at 800 °C in the air atmosphere by the thermogravimetric analysis (TGA), which was contributed by the high heat-resistance and the shielding effect of FS. This work would inspire in-depth studies on modification and design of phthalonitrile-based hybrid composites for extreme thermal environment.
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•Hydrophilic fumed silica exhibited well wettability with phenolic-type phthalonitrile resin.•Vacuum melt blending was proven as an efficient process achieving well dispersion of fumed silica nanoparticles.•Addition of fumed silica into phthalonitrile polymers improved the flexural strength and the char residue.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High performance composites not only pursue high strength, light weight, but also need to have multifunctional characteristics. To further improve curing efficiency and mechanical properties of ...phthalonitrile resin (PN75) and give full play to its excellent thermal and dielectric properties, mica as reinforcement was introduced into PN75 to form particle-filled resin (Mica/PN75) and CFRP (Mica/PN75/CF) composites. The introduction of mica reduced the curing temperature of PN75 and improved the curing efficiency. The thermal stability of resin and composites was further improved. The bending strength of the two groups of mica reinforced resin increased by 44.87% and 55.97%, and the dielectric constant decreased from 3.3 to 2.7 and 2.5, respectively. The bending strength of the composites was increased by up to 19.9%, and the glass transition temperature of composites was increased by up to 26 °C after reinforcement. The multidirectional reinforcement of PN75 by mica was studied and analyzed in this work.
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•Mica was used for the first time to particle reinforce phthalonitrile resin.•Powder blending was used to complete the mixing of inorganic particlesand phthalonitrilephtha resins.•The structure of reinforced resin is more stable, the bending toughness and dielectric property are greatly improved.•The reinforced composites have better thermal stability and improved toughness.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This paper develops a novel way to control nonstrict-feedback nonlinear systems by using only one approximator, namely a neural network (NN) or a fuzzy logic system (FLS), in the first step of ...backstepping, such that the computational simplicity is ensured. The bounded property of basis functions solves the “algebraic loop” problem. The double-channel event-triggered control (ETC) is completed both in sensor-to-controller (SC) and controller-to-actuator (CA) channels, where the separate triggering conditions are fabricated. To solve the “jumps of virtual control laws (JVCL)” problem bedeviling the backstepping combined with ETC, this paper opens an avenue while guaranteeing the closed-loop stability with the aid of undetermined virtual control laws.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
A long-standing conflict concerning metastable β-titanium (Ti) alloys is that high strength can be achieved through precipitation strengthening of α-phase while plasticity is largely compromised and ...even lost completely. Such strength-plasticity trade-off severely limits their structural applications. Here, an attempt to address the issue has been made in Ti–6Cr–5Mo–5V–4Al (Ti6554) high-strength metastable β-Ti alloy. Heterogeneous β-structure is architected by partial static recrystallization (SRX) through properly manipulating solution treatment in the hot-rolled bars. The resulting microstructure is composed of the recrystallized ‘new’ equiaxed β-grains (βe) and the remnant elongated β-fibers (βf). This β-morphology dramatically affects the subsequent αs-precipitation behavior during the aging process. αs-precipitation is rather uniform throughout βf-grains because the pre-existing dislocations left by hot rolling provide copious nucleation sites. However, αGB-films are preferentially formed along βe-grain boundaries, which leads to a boundary-affect zone (BAZ) and thereby renders αs-precipitation in a size gradient from β-grain boundaries to grain interiors. As a result, an ultra-high strength of ∼1700 MPa is achieved whilst the ductility can be up to be 5% in the β-hetero aged samples, which is superior to the β-homo aged siblings that have the same strength level but fully succumb to macroscopic brittleness. The enhanced plasticity in the β-hetero aged samples originates from much better deformation compatibility conferred by the aged βf-grains. However, the soft feature of BAZ around βe-grain boundaries in the β-homo aged samples causes strain localization, which eventually induces intergranular brittle fracture. These findings provide an effective strategy for enhancing plasticity of high-strength metastable β-Ti alloys by structural design, where homogeneous αs-precipitates can be easily constructed by combining conventional thermomechanical processing and heat treatment.
•Strength-ductility trade-off is evaded by a new structural design in Ti6554 alloy.•Enhanced ductility of ∼5% together with high strength of ∼1700 MPa is achieved.•Heterogeneous β-structure is architected by partial static recrystallization.•α-precipitation is rather uniform whilst αGB-film is effectively suppressed.•The improved ductility is conferred by superior deformation compatibility.
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A low-frequency piezoelectric motor based on inertia drive is presented in this paper, which is composed of a stator section and a rotor section. The stator employs an asymmetric structure, which ...causes torsional vibration when it is driven by single-phase sine wave power. In this paper, we study the working mechanism and characteristics of the low-frequency piezoelectric motor through theoretical modeling and experimental testing.
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•The driving unit of the piezoelectric motor employs an asymmetric structure, which can cause torsional vibration.•The piezoelectric motor can resonate at 50 Hz, so it does not require special power supply and has low working noise.•The inertia drive piezoelectric motor has obvious advantages like simple structure, easy miniaturization and low cost.
The inertia drive piezoelectric motor generally employs an asymmetric waveform driving signal, and the power supply for generating such type of driving signal is complicated and costly. In order to simplify the driving power of the inertia drive piezoelectric motor, a low-frequency piezoelectric motor driven by a 50 Hz sine wave is proposed in this paper. We first analyze the working principle: the pressure between the rotor and the stator changes asymmetrically in one working cycle, driving the rotor’s one-way rotation. Then we establish the dynamic model of the system and study the influence of the pre-stress between the stator and the rotor on the output performance of the low-frequency piezoelectric motor. Finally, the prototype is made and tested for performance. Experiments show that the low-frequency piezoelectric motor resonates at a driving frequency of 50 Hz, where the amplitudes of the stator in the vertical direction and the rotational direction are 21 μm and 136 μm respectively. When the pre-stress between the stator and the rotor is 5 N, the motor speed reaches a maximum value of 4.3 r/min; when the pre-stress is 11 N, the torque of the motor reaches a maximum value of 0.29 Nm.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
High temperature titanium alloys are being urgently developed owing to the requirements of advanced aerospace industry. Performance of the alloys in service under high-temperature environments always ...attracts great attention. In this study, variations of microstructure and mechanical property in TC25 (Ti-6.5Al-2Mo-1Zr-1Sn-1 W-0.2Si) dual-phase high temperature titanium alloy subjected to thermal exposure have been systematically investigated by coupling microstructural characterization, compositional analyses and mechanical measurement. It is found that strength is significantly enhanced while ductility is sharply degraded when the alloy is thermally exposed at 550 °C for a long duration of 100 h. Microstructural observations manifest that ternary α-needles (αt) are drastically precipitated from β-ligaments inside transformed β-matrix (βtrans) whilst α2 (Ti3Al)-phase is produced from primary α-phase (αp) through ordered transformation. The precipitation of αt-needles is promoted by β-phase metastability resulting from insufficient element partitioning in the initial microstructure. The β-phase stability also renders αt-precipitation encounter size effect of β-ligaments, where the precipitation is suppressed when β-ligaments are thin in size. Both precipitation of αt-needles and α2-phase triggers precipitation-hardening effect, which results in strain localization and thereby regresses alloy ductility. However, further analysis indicates that compared with α2-phase, αt-precipitation plays more adverse role in embrittlement in the current alloy. This is different from thermal-exposed behavior of most of high temperature titanium alloys reported in literatures. These findings enrich our fundamental understanding on thermal stability of high temperature titanium alloys, and provide plausible implication to improve high temperature performance via controlling phase precipitation.
•Thermal stability of TC25 high-temperature titanium alloy was investigated.•αt-needles and α2-particles are respectively precipitated from β-matrix and αp-phase.•Both αt and α2-precipitation results in strain localization and alloy embrittlement.•αt-precipitation plays more adverse role in alloy embrittlement than α2-phase.
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