Subjects -> ENGINEERING (Total: 2844 journals)
    - CHEMICAL ENGINEERING (247 journals)
    - CIVIL ENGINEERING (248 journals)
    - ELECTRICAL ENGINEERING (176 journals)
    - ENGINEERING (1448 journals)
    - HYDRAULIC ENGINEERING (62 journals)
    - INDUSTRIAL ENGINEERING (97 journals)
    - MECHANICAL ENGINEERING (115 journals)

MECHANICAL ENGINEERING (115 journals)                     

Showing 1 - 115 of 115 Journals sorted alphabetically
Acta Mechanica     Hybrid Journal   (Followers: 25)
Acta Mechanica et Automatica     Open Access   (Followers: 1)
Acta Mechanica Solida Sinica     Full-text available via subscription   (Followers: 9)
Acta Universitatis Sapientiae Electrical and Mechanical Engineering     Open Access  
Advanced Energy Materials     Hybrid Journal   (Followers: 29)
Advances in Mechanical Engineering     Open Access   (Followers: 136)
Advances in Tribology     Open Access   (Followers: 15)
American Journal of Mechanical Engineering     Open Access   (Followers: 58)
Archive of Mechanical Engineering     Open Access   (Followers: 72)
Archives of Civil and Mechanical Engineering     Full-text available via subscription   (Followers: 4)
Australian Journal of Mechanical Engineering     Hybrid Journal   (Followers: 6)
Bulletin of NTU - Dynamics and strength of machines     Open Access   (Followers: 2)
Bulletin of the Polish Academy of Sciences : Technical Sciences     Open Access   (Followers: 1)
Case Studies in Mechanical Systems and Signal Processing     Open Access  
Chinese Journal of Mechanical Engineering     Open Access   (Followers: 3)
Curved and Layered Structures     Open Access   (Followers: 3)
Emission Control Science and Technology     Hybrid Journal   (Followers: 2)
European Mechanical Science     Open Access  
Facta Universitatis, Series : Mechanical Engineering     Open Access   (Followers: 6)
Friction     Open Access   (Followers: 6)
Frontiers in Mechanical Engineering     Open Access   (Followers: 6)
Frontiers of Mechanical Engineering     Hybrid Journal   (Followers: 7)
High Speed Machining     Open Access   (Followers: 5)
Human Factors and Mechanical Engineering for Defense and Safety     Hybrid Journal   (Followers: 1)
Ingeniería Mecánica     Open Access   (Followers: 4)
Ingenieria Mecánica. Tecnologia y Desarrollo     Open Access   (Followers: 3)
International Journal of Applied Mechanics and Engineering     Open Access   (Followers: 8)
International Journal of Civil, Mechanical and Energy Science     Open Access   (Followers: 3)
International Journal of Dynamics and Control     Hybrid Journal   (Followers: 7)
International Journal of Engineering Materials and Manufacture     Open Access   (Followers: 1)
International Journal of Manufacturing, Materials, and Mechanical Engineering     Full-text available via subscription   (Followers: 17)
International Journal of Material and Mechanical Engineering     Open Access   (Followers: 29)
International Journal of Mechanical and Materials Engineering     Open Access   (Followers: 11)
International Journal of Mechanical Engineering Education     Full-text available via subscription   (Followers: 13)
International Journal of Mechanical Sciences     Hybrid Journal   (Followers: 14)
International Journal of Mechatronics and Automation     Hybrid Journal   (Followers: 6)
International Journal of Metrology and Quality Engineering     Full-text available via subscription   (Followers: 4)
International Journal of Microwave Engineering and Technology     Full-text available via subscription   (Followers: 2)
International Journal of Powertrains     Hybrid Journal   (Followers: 2)
Iranian Journal of Science and Technology, Transactions of Mechanical Engineering     Hybrid Journal  
JMST Advances     Hybrid Journal  
Journal of Aircraft     Hybrid Journal   (Followers: 328)
Journal of Applied Mechanical Engineering     Open Access   (Followers: 10)
Journal of Applied Mechanical Engineering and Green Technology     Open Access   (Followers: 1)
Journal of Biomechanical Engineering     Full-text available via subscription   (Followers: 12)
Journal of Computational and Applied Research in Mechanical Engineering     Open Access  
Journal of Energy, Mechanical, Material and Manufacturing Engineering     Open Access   (Followers: 1)
Journal of Mechanical Design     Full-text available via subscription   (Followers: 81)
Journal of Mechanical Design and Testing     Open Access   (Followers: 1)
Journal of Mechanical Engineering     Open Access   (Followers: 71)
Journal of Mechanical Engineering and Automation     Open Access   (Followers: 11)
Journal of Mechanical Engineering Research     Open Access   (Followers: 13)
Journal of Mechanical Engineering Science and Technology     Open Access   (Followers: 1)
Journal of Mechanical Science and Technology     Hybrid Journal   (Followers: 7)
Journal of Mechanics     Hybrid Journal   (Followers: 21)
Journal of Mechatronics, Electrical Power, and Vehicular Technology     Open Access   (Followers: 6)
Journal of Microelectromechanical Systems     Hybrid Journal   (Followers: 39)
Journal of Non-Equilibrium Thermodynamics     Hybrid Journal   (Followers: 7)
Journal of Renewable Energy and Mechanics     Open Access   (Followers: 1)
Journal of Statistical Mechanics: Theory and Experiment     Full-text available via subscription   (Followers: 4)
Journal of Strain Analysis for Engineering Design     Hybrid Journal   (Followers: 7)
Journal of the Brazilian Society of Mechanical Sciences     Open Access   (Followers: 2)
Journal of the Brazilian Society of Mechanical Sciences and Engineering     Hybrid Journal   (Followers: 3)
Journal of the Mechanical Behavior of Biomedical Materials     Hybrid Journal   (Followers: 13)
Journal of Theoretical and Applied Mechanics     Open Access   (Followers: 27)
Jurnal Crankshaft     Open Access   (Followers: 2)
Jurnal Energi Dan Manufaktur     Open Access  
Jurnal Taman Vokasi     Open Access  
Jurnal Teknik Mesin     Open Access  
Latin American Journal of Solids and Structures     Open Access   (Followers: 5)
Lubricants     Open Access   (Followers: 2)
Main Group Metal Chemistry     Open Access   (Followers: 2)
Material Design & Processing Communications     Hybrid Journal  
Mechanical Engineering and Design     Open Access   (Followers: 77)
Mechanical Engineering Research     Open Access   (Followers: 19)
Mechanical Sciences     Open Access   (Followers: 11)
Mechanical Systems and Signal Processing     Hybrid Journal   (Followers: 7)
Media Mesin : Majalah Teknik Mesin     Open Access   (Followers: 2)
Mekanika : Majalah Ilmiah Mekanika     Open Access   (Followers: 1)
Modern Mechanical Engineering     Open Access   (Followers: 60)
MTZextra     Full-text available via subscription  
Open Mechanical Engineering Journal     Open Access   (Followers: 2)
Periodica Polytechnica Mechanical Engineering     Open Access  
Proceedings of the Institution of Mechanical Engineers Part A: Journal of Power and Energy     Hybrid Journal   (Followers: 8)
Proceedings of the Institution of Mechanical Engineers Part B: Journal of Engineering Manufacture     Hybrid Journal   (Followers: 16)
Proceedings of the Institution of Mechanical Engineers Part C: Journal of Mechanical Engineering Science     Hybrid Journal   (Followers: 26)
Proceedings of the Institution of Mechanical Engineers Part D: Journal of Automobile Engineering     Hybrid Journal   (Followers: 16)
Proceedings of the Institution of Mechanical Engineers Part E: Journal of Process Mechanical Engineering     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Mechanical Engineers Part F: Journal of Rail and Rapid Transit     Hybrid Journal   (Followers: 15)
Proceedings of the Institution of Mechanical Engineers Part G: Journal of Aerospace Engineering     Hybrid Journal   (Followers: 44)
Proceedings of the Institution of Mechanical Engineers Part H: Journal of Engineering in Medicine     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Mechanical Engineers Part I: Journal of Systems and Control Engineering     Hybrid Journal   (Followers: 15)
Proceedings of the Institution of Mechanical Engineers Part J: Journal of Engineering Tribology     Hybrid Journal   (Followers: 37)
Proceedings of the Institution of Mechanical Engineers Part K: Journal of Multi-body Dynamics     Hybrid Journal   (Followers: 4)
Proceedings of the Institution of Mechanical Engineers Part L: Journal of Materials: Design and Applications     Hybrid Journal   (Followers: 12)
Proceedings of the Institution of Mechanical Engineers Part M: Journal of Engineering for the Maritime Environment     Hybrid Journal   (Followers: 6)
Proceedings of the Institution of Mechanical Engineers Part N: Journal of Nanoengineering and Nanosystems     Hybrid Journal   (Followers: 3)
Proceedings of the Institution of Mechanical Engineers Part O: Journal of Risk and Reliability     Hybrid Journal   (Followers: 7)
Proceedings of the Institution of Mechanical Engineers Part P: Journal of Sports Engineering and Technology     Hybrid Journal   (Followers: 4)
Quantitative InfraRed Thermography Journal     Hybrid Journal   (Followers: 1)
Recent Patents on Mechanical Engineering     Hybrid Journal  
Rekayasa Mesin     Open Access  
Research Papers Faculty of Materials Science and Technology Slovak University of Technology     Open Access   (Followers: 3)
Science China Physics, Mechanics & Astronomy     Hybrid Journal   (Followers: 4)
Scientific Bulletin of Valahia University - Materials and Mechanics     Open Access  
Simetris : Jurnal Teknik Mesin, Elektro dan Ilmu Komputer     Open Access  
Strojarstvo     Full-text available via subscription  
Strojn?cky casopis ? Journal of Mechanical Engineering     Open Access   (Followers: 1)
Technical Reports Mechanical Engineering     Open Access   (Followers: 6)
Trends in Mechanical Engineering & Technology     Full-text available via subscription   (Followers: 3)
Tribologia : Finnish Journal of Tribology     Open Access   (Followers: 2)
Universal Journal of Mechanical Engineering     Open Access   (Followers: 20)
Vestnik of Don State Technical University     Open Access  
Двигуни внутрішнього згоряння     Open Access   (Followers: 1)
Проблемы машиностроения - Mechanical Problems     Open Access   (Followers: 1)


Similar Journals
Journal Cover
Frontiers of Mechanical Engineering
Journal Prestige (SJR): 0.415
Citation Impact (citeScore): 2
Number of Followers: 7  
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 2095-0233 - ISSN (Online) 2095-0241
Published by Springer-Verlag Homepage  [2626 journals]
  • Establishing distinctive theories and methods of design science rooted in
           Chinese traditional culture
    • Abstract: Abstract The human social development saw the formation of five unique civilizations, with the latter forming their own distinctive cultures. China’s traditional culture is its most fundamental ideological weapon for solving problems. The Chinese are good at comprehensive thinking, dialectical thinking, and systematic analysis. These ideological weapons can solve the problems of formal science and technology and create scientific and technological achievements on par with global advanced scale. Ancient China is filled with original scientific and technological achievements, which strongly prove ancient China’s possession of its own science and technology different from that of Western Renaissance. Therefore, a comprehensive understanding of science, technology, experience, and intuition is necessary. The long-held superstition regarding the West, the lack of confidence, self-denial, blind imitation of ideas, and shackles must be thrown away. Only then can we take the road toward an authentic Chinese creative design as we learn from others.
      PubDate: 2020-07-22
  • Level set band method: A combination of density-based and level set
           methods for the topology optimization of continuums
    • Abstract: Abstract The level set method (LSM), which is transplanted from the computer graphics field, has been successfully introduced into the structural topology optimization field for about two decades, but it still has not been widely applied to practical engineering problems as density-based methods do. One of the reasons is that it acts as a boundary evolution algorithm, which is not as flexible as density-based methods at controlling topology changes. In this study, a level set band method is proposed to overcome this drawback in handling topology changes in the level set framework. This scheme is proposed to improve the continuity of objective and constraint functions by incorporating one parameter, namely, level set band, to seamlessly combine LSM and density-based method to utilize their advantages. The proposed method demonstrates a flexible topology change by applying a certain size of the level set band and can converge to a clear boundary representation methodology. The method is easy to implement for improving existing LSMs and does not require the introduction of penalization or filtering factors that are prone to numerical issues. Several 2D and 3D numerical examples of compliance minimization problems are studied to illustrate the effects of the proposed method.
      PubDate: 2020-06-21
  • Evaluation of measurement uncertainty of the high-speed variable-slit
           system based on the Monte Carlo method
    • Abstract: Abstract This paper presents a dynamic and static error transfer model and uncertainty evaluation method for a high-speed variable-slit system based on a two-dimensional orthogonal double-layer air-floating guide rail structure. The motion accuracy of the scanning blade is affected by both the moving component it is attached to and the moving component of the following blade during high-speed motion. First, an error transfer model of the high-speed variable-slit system is established, and the influence coefficients are calculated for each source of error associated with the accuracy of the blade motion. Then, the maximum range of each error source is determined by simulation and experiment. Finally, the uncertainty of the blade displacement measurement is evaluated using the Monte Carlo method. The proposed model can evaluate the performance of the complex mechanical system and be used to guide the design.
      PubDate: 2020-06-04
  • Compressive behavior and energy absorption of polymeric lattice structures
           made by additive manufacturing
    • Abstract: Abstract Lattice structures have numerous outstanding characteristics, such as light weight, high strength, excellent shock resistance, and highly efficient heat dissipation. In this work, by combining experimental and numerical methods, we investigate the compressive behavior and energy absorption of lattices made through the stereolithography apparatus process. Four types of lattice structures are considered: (i) Uniform body-centered-cubic (U-BCC); (ii) graded body-centered-cubic (G-BCC); (iii) uniform body-centered-cubic with z-axis reinforcement (U-BCCz); and (iv) graded body-centered-cubic with z-axis reinforcement (G-BCCz). We conduct compressive tests on these four lattices and numerically simulate the compression process through the finite element method. Analysis results show that BCCz has higher modulus and strength than BCC. In addition, uniform lattices show better energy absorption capabilities at small compression distances, while graded lattices absorb more energy at large compression distances. The good correlation between the simulation results and the experimental phenomena demonstrates the validity and accuracy of the present investigation method.
      PubDate: 2020-06-01
  • Laser sintering of Cu nanoparticles on PET polymer substrate for printed
           electronics at different wavelengths and process conditions
    • Abstract: Abstract This study explores the feasibility of different laser systems to sinter screen-printed lines from nonconductive copper nanoparticles (Cu NPs) on polyethylene terephthalate polymer film. These materials are commonly used in manufacturing functional printed electronics for large-area applications. Here, optical and thermal characterization of the materials is conducted to identify suitable laser sources and process conditions. Direct diode (808 nm), Nd:YAG (1064 nm and second harmonic of 532 nm), and ytterbium fiber (1070 nm) lasers are explored. Optimal parameters for sintering the Cu NPs are identified for each laser system, which targets low resistivity and high processing speed. Finally, the quality of the sintered tracks is quantified, and the laser sintering mechanisms observed under different wavelengths are analyzed. Practical considerations are discussed to improve the laser sintering process of Cu NPs.
      PubDate: 2020-06-01
  • Untethered quadrupedal hopping and bounding on a trampoline
    • Abstract: Abstract For quadruped robots with springy legs, a successful jump usually requires both suitable elastic parts and well-designed control algorithms. However, these two problems are mutually restricted and hard to solve at the same time. In this study, we attempt to solve the problem of controller design with the help of a robot without any elastic mounted parts, in which the untethered robot is made to jump on a trampoline. The differences between jumping on hard surfaces with springy legs and jumping on springy surfaces with rigid legs are briefly discussed. An intuitive control law is proposed to balance foot contact forces; in this manner, excessive pitch oscillation during hopping or bounding can be avoided. Hopping height is controlled by tuning the time delay of the leg stretch. Together with other motion generators based on kinematic law, the robot can perform translational and rotational movements while hopping or bounding on the trampoline. Experiments are conducted to validate the effectiveness of the proposed control framework.
      PubDate: 2020-06-01
  • Dynamic characteristics of a shrouded blade with impact and friction
    • Abstract: Abstract A simplified computational model of a twisted shrouded blade with impact and friction is established. In this model, the shrouded blade is simulated by a flexible Timoshenko beam with a tip-mass, and the effects of centrifugal stiffening, spin softening, and Coriolis force are considered. Impact force is simulated using a linear spring model, and friction force is generated by a tangential spring model under sticking state and a Coulomb friction model under sliding state. The proposed model is validated by a finite element model. Then, the effects of initial gap and normal preload, coefficient of friction, and contact stiffness ratio (the ratio of tangential contact stiffness to normal contact stiffness) on system vibration responses are analyzed. Results show that resonant peaks become inconspicuous and impact plays a dominant role when initial gaps are large between adjacent shrouds. By contrast, in small initial gaps or initial normal preloads condition, resonant speed increases sharply, and the optimal initial normal preloads that can minimize resonant amplitude becomes apparent. Coefficient of friction affects the optimal initial normal preload, but it does not affect vibration responses when the contact between shrouds is under full stick. System resonant amplitude decreases with the increase of contact stiffness ratio, but the optimal initial normal preload is unaffected.
      PubDate: 2020-06-01
  • Evaluation of power regeneration in primary suspension for a railway
    • Abstract: Abstract To improve the fuel economy of rail vehicles, this study presents the feasibility of using power regenerating dampers (PRDs) in the primary suspension systems of railway vehicles and evaluates the potential and recoverable power that can be obtained. PRDs are configured as hydraulic electromagnetic-based railway primary vertical dampers and evaluated in parallel and series modes (with and without a viscous damper). Hydraulic configuration converts the linear behavior of the track into a unidirectional rotation of the generator, and the electromagnetic configuration provides a controllable damping force to the primary suspension system. In several case studies, generic railway vehicle primary suspension systems that are configured to include a PRD in the two configuration modes are modeled using computer simulations. The simulations are performed on measured tracks with typical irregularities for a generic UK passenger route. The performance of the modified vehicle is evaluated with respect to key performance indicators, including regenerated power, ride comfort, and running safety. Results indicate that PRDs can simultaneously replace conventional primary vertical dampers, regenerate power, and exhibit desirable dynamic performance. A peak power efficiency of 79.87% is theoretically obtained in series mode on a top-quality German Intercity Express track (Track 270) at a vehicle speed of 160 mile/h (∼257 km/h).
      PubDate: 2020-06-01
  • Influence of direct electric current on wetting behavior during brazing
    • Abstract: Abstract The wetting behavior of liquid metals is of great importance for many processes. For brazing, however, a targeted modification beyond the adjustment of conventional process parameters or the actual set-up was not possible in the past. Therefore, the effect of direct electric current along the surface of a steel substrate on the wetting behavior and the formation of the spreading pattern of an industrial nickel-based filler metal was investigated at a temperature above T = 1000 °C in a vacuum brazing furnace. By applying direct current up to I = 60 A the wetted surface area could be increased and the spreading of the molten filler metal could be controlled in dependence of the polarity of the electric current. The electric component of the Lorentz force is supposed to be feasible reasons for the observed dependence of the electrical polarity on the filler metal spreading direction. To evaluate the influence of the electric current on the phase formation subsequent selective electron microscope analyses of the spreading pattern were carried out.
      PubDate: 2020-05-12
  • Machinability of damage-tolerant titanium alloy in orthogonal turn-milling
    • Abstract: Abstract The damage-tolerant titanium alloy TC21 is used extensively in important parts of advanced aircraft because of its high strength and durability. However, cutting TC21 entails problems, such as high cutting temperature, high tool tip stress, rapid tool wear, and difficulty guaranteeing processing quality. Orthogonal turn-milling can be used to solve these problems. In this study, the machinability of TC21 in orthogonal turn-milling is investigated experimentally to optimize the cutting parameters of orthogonal turn-milling and improve the machining efficiency, tool life, and machining quality of TC21. The mechanism of the effect of turn-milling parameters on tool life is discussed, the relationship between each parameter and tool life is analyzed, and the failure process of a TiAlN-coated tool in turn-milling is explored. Experiments are conducted on the integrity of the machined surface (surface roughness, metallographic structure, and work hardening) by turn-milling, and how the parameters influence such integrity is analyzed. Then, reasonable cutting parameters for TC21 in orthogonal turn-milling are recommended. This study provides strong guidance for exploring the machinability of difficult-to-cut-materials in orthogonal turn-milling and improves the applicability of orthogonal turn-milling for such materials.
      PubDate: 2020-05-12
  • Design and locomotion analysis of two kinds of rolling expandable mobile
           linkages with a single degree of freedom
    • Abstract: Abstract This study presents two kinds of rolling robots that are able to roll by deforming their outer shapes with a single degree of freedom. Each robot is an essential multi-loop planar expandable linkage constructed by a concave outer loop and several inner parallelogram loops. In this study, the mechanical design of the robots is introduced. Dynamic rolling process is further analyzed on the basis of zero moment point method, and a morphing strategy is proposed to guarantee a stable dynamic rolling process. A novel passive rolling locomotion is also developed, which enables the robots to roll and stand on a slope. To verify the design, two prototypes are manufactured, wherein the dynamic and passive rolling locomotion are carried out.
      PubDate: 2020-05-02
  • Dynamic modeling and coupling characteristics of rotating inclined beams
           with twisted-shape sections
    • Abstract: Abstract In the existing literature, most studies investigated the free vibrations of a rotating pre-twisted cantilever beam; however, few considered the effect of the elasticsupport boundary and the quantification of modal coupling degree among different vibration directions. In addition, Coriolis, spin softening, and centrifugal stiffening effects are not fully included in the derived equations of motion of a rotating beam in most literature, especially the centrifugal stiffening effect in torsional direction. Considering these deficiencies, this study established a coupled flapwise–chordwise–axial–torsional dynamic model of a rotating double-tapered, pre-twisted, and inclined Timoshenko beam with elastic supports based on the semi-analytic method. Then, the proposed model was verified with experiments and ANSYS models using Beam188 and Shell181 elements. Finally, the effects of setting and pretwisted angles on the degree of coupling among flapwise, chordwise, and torsional directions were quantified via modal strain energy ratios. Results showed that 1) the appearance of torsional vibration originates from the combined effect of flapwise–torsional and chordwise–torsional couplings dependent on the Coriolis effect, and that 2) the flapwise–chordwise coupling caused by the pure pre-twisted angle is stronger than that caused by the pure setting angle.
      PubDate: 2020-04-29
  • Relative vibration identification of cutter and workpiece based on
           improved bidimensional empirical mode decomposition
    • Abstract: Abstract In the process of cutting, the relative vibration between the cutter and the workpiece has an important effect on the surface topography. In this study, the bidimensional empirical mode decomposition (BEMD) method is used to identify such effect. According to Riesz transform theory, a type of isotropic monogenic signal is proposed. The boundary data is extended on the basis of a similarity principle that deals with serious boundary effect problem. The decomposition examples show that the improved BEMD can effectively solve the problem of boundary effect and decompose the original machined surface topography at multiple scales. The characteristic surface topography representing the relative vibration between the cutter and the workpiece through feature identification is selected. In addition, the spatial spectrum analysis of the extracted profile is carried out. The decimal part of the frequency ratio that has an important effect on the shape of the contour can be accurately identified through contour extraction and spatial spectrum analysis. The decomposition results of simulation and experimental surface morphology demonstrate the validity of the improved BEMD algorithm in realizing the relative vibration identification between the cutter and the work-piece.
      PubDate: 2020-04-28
  • Two-sided ultrasonic surface rolling process of aeroengine blades based on
           on-machine noncontact measurement
    • Abstract: Abstract As crucial parts of an aeroengine, blades are vulnerable to damage from long-term operation in harsh environments. The ultrasonic surface rolling process (USRP) is a novel surface treatment technique that can highly improve the mechanical behavior of blades. During secondary machining, the nominal blade model cannot be used for secondary machining path generation due to the deviation between the actual and nominal blades. The clamping error of the blade also affects the precision of secondary machining. This study presents a two-sided USRP (TS-USRP) machining for aeroengine blades on the basis of on-machine noncontact measurement. First, a TS-USRP machining system for blade is developed. Second, a 3D scanning system is used to obtain the point cloud of the blade, and a series of point cloud processing steps is performed. A local point cloud automatic extraction algorithm is introduced to extract the point cloud of the strengthened region of the blade. Then, the tool path is designed on the basis of the extracted point cloud. Finally, an experiment is conducted on an actual blade, with results showing that the proposed method is effective and efficient.
      PubDate: 2020-03-31
  • An isogeometric numerical study of partially and fully implicit schemes
           for transient adjoint shape sensitivity analysis
    • Abstract: Abstract In structural design optimization involving transient responses, time integration scheme plays a crucial role in sensitivity analysis because it affects the accuracy and stability of transient analysis. In this work, the influence of time integration scheme is studied numerically for the adjoint shape sensitivity analysis of two benchmark transient heat conduction problems within the framework of isogeometric analysis. It is found that (i) the explicit approach (β = 0) and semi-implicit approach with β < 0.5 impose a strict stability condition of the transient analysis; (ii) the implicit approach (β = 1) and semi-implicit approach with β > 0.5 are generally preferred for their unconditional stability; and (iii) Crank-Nicolson type approach (β= 0.5) may induce a large error for large time-step sizes due to the oscillatory solutions. The numerical results also show that the time-step size does not have to be chosen to satisfy the critical conditions for all of the eigen-frequencies. It is recommended to use β ≈ 0.75 for unconditional stability, such that the oscillation condition is much less critical than the Crank-Nicolson scheme, and the accuracy is higher than a fully implicit approach.
      PubDate: 2020-03-23
  • Experimental study on high-efficiency polishing for potassium dihydrogen
           phosphate (KDP) crystal by using two-phase air—water fluid
    • Abstract: Abstract A high-efficiency polishing approach using two-phase air—water fluid (TAWF) is proposed to avoid surface contamination and solve the inefficiency of previous water-dissolution polishing techniques for potassium dihydrogen phosphate (KDP) crystal. In the proposed method, controllable deliquescence is implemented without any chemical impurity. The product of deliquescence is then removed by a polishing pad to achieve surface planarization. The mechanism underlying TAWF polishing is analyzed, a special device is built to polish the KDP crystal, and the effect of relative humidity (RH) on polishing performance is studied. The relationship between key parameters of polishing and surface planarization is also investigated. Results show that the polishing performance is improved with increasing RH. However, precisely controlling the RH is extremely difficult during TAWF polishing. Controllable deliquescence can easily be disrupted once the RH fluctuates, which therefore needs to be restricted to a low level to avoid its influence on deliquescence rate. The material removal of TAWF polishing is mainly attributed to the synergistic effect of deliquescence and the polishing pad. Excessive polishing pressure and revolution rate remarkably reduce the life of the polishing pad and the surface quality of the KDP crystal. TAWF polishing using IC-1000 and TEC-168S increase the machining efficiency by 150%, and a smooth surface with a root mean square surface roughness of 5.5 nm is obtained.
      PubDate: 2020-03-14
  • Dynamic modulation performance of ferroelectric liquid crystal
           polarization rotators and Mueller matrix polarimeter optimization
    • Abstract: Abstract A ferroelectric liquid crystal polarization rotator (FLCPR) has been widely used in polarization measurement due to its fast and stable modulation characteristics. The accurate characterization of the modulation performance of FLCPR directly affects the measurement accuracy of the instrument based on liquid crystal modulation. In this study, FLCPR is accurately characterized using a self-developed high-speed Stokes polarimeter. Strong linear and weak circular birefringence are observed during modulation processes, and all the optical parameters of FLCPR are dependent on driving voltage. A dual FLCPR-based Mueller matrix polarimeter is designed on the basis of the Stokes polarimeter. The designed polarimeter combines the advantages of the high modulation frequency of FLCPR and the ultrahigh temporal resolution of the fast polarization measurement system in the Stokes polarimeter. The optimal configuration of the designed polarizer is predicted in accordance with singular value decomposition. A simulated thickness measurement of a 24 nm standard SiO2 thin film is performed using the optimal configuration. Results show that the relative error in thickness measurement caused by using the unsatisfactory modulation characteristics of FLCPR reaches up to −4.34%. This finding demonstrates the importance of the accurate characterization of FLCPR in developing a Mueller matrix polarizer.
      PubDate: 2020-03-11
  • Digital high-efficiency print forming method and device for multi-material
           casting molds
    • Abstract: Abstract Sand mold 3D printing technology based on the principle of droplet ejection has undergone rapid development in recent years and has elicited increasing attention from engineers and technicians. However, current sand mold 3D printing technology exhibits several problems, such as single-material printing molds, low manufacturing efficiency, and necessary post-process drying and heating for the manufacture of sand molds. This study proposes a novel high-efficiency print forming method and device for multi-material casting molds. The proposed method is specifically related to the integrated forming of two-way coating and printing and the short-flow manufacture of roller compaction and layered heating. These processes can realize the high-efficiency print forming of high-performance sand molds. Experimental results demonstrate that the efficiency of sand mold fabrication can be increased by 200% using the proposed two-way coating and printing method. The integrated forming method for layered heating and roller compaction presented in this study effectively shortens the manufacturing process for 3D-printed sand molds, increases sand mold strength by 63.8%, and reduces resin usage by approximately 30%. The manufacture of multi-material casting molds is demonstrated on typical wheeled cast-iron parts. This research provides theoretical guidance for the engineering application of sand mold 3D printing.
      PubDate: 2020-03-11
  • Sagittal SLIP-anchored task space control for a monopode robot traversing
           irregular terrain
    • Abstract: Abstract As a well-explored template that captures the essential dynamical behaviors of legged locomotion on sagittal plane, the spring-loaded inverted pendulum (SLIP) model has been extensively employed in both biomechanical study and robotics research. Aiming at fully leveraging the merits of the SLIP model to generate the adaptive trajectories of the center of mass (CoM) with maneuverability, this study presents a novel two-layered sagittal SLIP-anchored (SSA) task space control for a monopode robot to deal with terrain irregularity. This work begins with an analytical investigation of sagittal SLIP dynamics by deriving an approximate solution with satisfactory apex prediction accuracy, and a two-layered SSA task space controller is subsequently developed for the monopode robot. The higher layer employs an analytical approximate representation of the sagittal SLIP model to form a deadbeat controller, which generates an adaptive reference trajectory for the CoM. The lower layer enforces the monopode robot to reproduce a generated CoM movement by using a task space controller to transfer the reference CoM commands into joint torques of the multi-degree of freedom monopode robot. Consequently, an adaptive hopping behavior is exhibited by the robot when traversing irregular terrain. Simulation results have demonstrated the effectiveness of the proposed method.
      PubDate: 2020-03-07
  • A carbon efficiency upgrading method for mechanical machining based on
           scheduling optimization strategy
    • Abstract: Abstract Low-carbon manufacturing (LCM) is increasingly being regarded as a new sustainable manufacturing model of carbon emission reduction in the manufacturing industry. In this paper, a two-stage low-carbon scheduling optimization method of job shop is presented as part of the efforts to implement LCM, which also aims to reduce the processing cost and improve the efficiency of a mechanical machining process. In the first stage, a task assignment optimization model is proposed to optimize carbon emissions without jeopardizing the processing efficiency and the profit of a machining process. Non-dominated sorting genetic algorithm II and technique for order preference by similarity to an ideal solution are then adopted to assign the most suitable batch task of different parts to each machine. In the second stage, a processing route optimization model is established to plan the processing sequence of different parts for each machine. Finally, niche genetic algorithm is utilized to minimize the makespan. A case study on the fabrication of four typical parts of a machine tool is demonstrated to validate the proposed method.
      PubDate: 2020-03-07
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