A parametric modeling method for the pose-dependent dynamics of bi-rotary milling head

2016 ◽  
Vol 232 (5) ◽  
pp. 797-815 ◽  
Author(s):  
Chao Du ◽  
Jun Zhang ◽  
Dun Lu ◽  
Huijie Zhang ◽  
Wanhua Zhao
Keyword(s):  
Dynamic Equation ◽  
Joint Stiffness ◽  
Rigid Bodies ◽  
Parametric Modeling ◽  
Impact Testing ◽  
Design Stage ◽  
Surface Machining ◽  
Rigid Body Dynamic ◽  
Five Axis ◽  
The Impact

Bi-rotary milling head is one of the core components of five-axis machining center, and its dynamic characteristics directly affect the machining stability and accuracy. During the sculptured surface machining, the bi-rotary milling head exhibits varying dynamics in various machining postures. To facilitate rapid evaluation of the dynamic behavior of the bi-rotary milling head within the whole workspace, this article presents a method for parametrically establishing dynamic equation at different postures. The rotating and swing shafts are treated as rigid bodies. The varying stiffness of the flexible joints (such as bearings and hirth coupling) affected by gravity and cutting force at different swing angles is analyzed and then a multi-rigid-body dynamic model of the bi-rotary milling head considering the pose-varying joint stiffness is established. The Lagrangian method is employed to deduce the parametric dynamic equation with posture parameters. The static stiffness, natural frequencies and frequency response functions at different postures are simulated using the parametric equation and verified by the impact testing experiments. The theoretical and experimental results show that the dynamics of the bi-rotary milling head vary with the machining postures, and the proposed method can be used for efficient and accurate evaluation of the pose-dependent dynamics at the design stage.

Effect of tilting angle on the dynamics of tilting table driven by worm and worm wheel

2014 ◽  
Vol 229 (10) ◽  
pp. 1782-1791 ◽  
Author(s):  
Wenming Wei ◽  
Jun Zhang ◽  
Dun Lu ◽  
Wanhua Zhao
Keyword(s):  
Natural Frequency ◽  
Transmission System ◽  
Impact Testing ◽  
Torsional Stiffness ◽  
Axial Stiffness ◽  
Parameter Method ◽  
Worm Wheel ◽  
Five Axis ◽  
The Impact ◽  
Tilting Table

The dynamics of tilting table behaves differently during five-axis machining due to the constant changes of the position of its center of mass which leads to different forces acting on parts of the transmission system. In this research, the lumped parameter method is used to model the dynamics of tilting table driven by worm and worm wheel in the tilting direction, where the varying stiffness of the transmission system at different tilting angles is considered. The impact testing experiments of tilting table system with tilting angles from 0° to 90° are also performed to verify the analytical model. The results from sensitivity analysis show that the three stiffnesses have a great effect on the variation of system natural frequency in the tilting direction, including the equivalent tangential meshing stiffness of worm and worm wheel, the torsional stiffness of worm wheel shaft, and the axial stiffness of worm supporting bearings. Moreover, the variations of system natural frequency with the three stiffnesses at different tilting angles are further investigated.

scholarly journals Investigation of the Effect of Slag Trap Design on Slag Delay Efficiency in the SolidWorks Flow Simulation Parametric Modeling Environment

2020 ◽  
pp. 108-117
Author(s):  
Serhii Kononchuk ◽  
◽  
Oleksandr Skrypnyk ◽  
Volodymyr Sviatskyi ◽  
Viktor Pukalov ◽  
...  
Keyword(s):  
Flow Rate ◽  
Field Experiments ◽  
Parametric Modeling ◽  
Design Stage ◽  
High Tech ◽  
Production Environment ◽  
Original Design ◽  
Trap Design ◽  
The Cost ◽  
The Impact

The most common technology for the manufacture of metal parts and work pieces is casting. High-tech branches of mechanical engineering require the production of high-quality castings of complex configuration from modern alloys with a given chemical composition and mechanical properties. The analysis of the causes of slag inclusions and ways to prevent them showed that in addition to technological means related to quality preparation of metal before pouring, a significant role is played by quiet continuous pouring of metal and properly designed foundry system, including slag trap. However, the use of the most common foundry systems (braking, throttle, with centrifugal slag traps, rain, siphon) to increase the efficiency of slag retention is associated with increased metal consumption, and as a consequence, leads to an increase in the cost of casting. Conducting experimental research by varying the design of the slag trap leads to an increase in the number of field experiments, given their complexity, limited by great difficulties. On the other hand, computer flow modeling allows to study the influence of slag trap design on the flow rate of the melt at the design stage and significantly reduce the cost of introduction of new castings. In order to reliably capture slag and reduce the speed of movement of the melt in the foundries, which provides a smooth filling of the form with an alloy, but without additional costs of metal, the original design of the ribbed slag catcher is proposed. The results of parametric modeling of the melt flow in the channel of the ribbed slag trap showed a decrease in the flow rate along the cross-sectional height of the slag trap compared to traditional by 0.028 m / s or 14.5%. This allowed to reduce the length of the slag trap to the first feeder. The expected metal savings are 0.26%. The form made using a 3D model of the slag trap showed satisfactory molding ability. But the obtained research results are of a recommendatory nature and require practical verification in the production environment. In addition, by varying parameters such as the height of the ribs, the distance between them, the angle of inclination, we can obtain similar results for different castings of different alloys. Given all this, there is a need for further study of the impact of the design of the slag trap on the efficiency of slag retention.

Pose-Dependent Dynamic Modeling and Analysis of Bi-Rotary Milling Head

2016 ◽  
Author(s):  
Chao Du ◽  
Dun Lu ◽  
Jun Zhang ◽  
Huijie Zhang ◽  
Wanhua Zhao
Keyword(s):  
Structural Parameters ◽  
Design Stage ◽  
Physical Parameters ◽  
Modeling And Analysis ◽  
Rigid Body Dynamic ◽  
Machining Center ◽  
Core Components ◽  
Stability And Accuracy ◽  
Five Axis ◽  
Body Dynamic

Bi-rotary milling head is one of the core components of five-axis machining center and its dynamic characteristics directly affect the machining stability and accuracy. During the five-axis machining, the milling head would change the posture continuously. To facilitate rapid evaluation and optimization of the dynamic behavior of the bi-rotary milling head within the whole workspace, a multi-rigid-body dynamic model considering the flexible joint is established. The varying stiffness of the flexible joints affected by gravity and cutting force at different swing angles is analyzed. A parametric dynamic equation with posture parameters and physical parameters is finally deduced. The sensitive structural parameters on natural frequency and its fluctuation within the workspace are obtained by the sensitivity analysis. The theoretical and experimental results show that the dynamics of the bi-rotary milling head behave pose-dependent and the varying dynamics can be positive controlled by modifying sensitive structural parameters at the design stage.

scholarly journals A Rational Numerical Method for Simulation of Drop-Impact Dynamics of Oleo-Pneumatic Landing Gear

2021 ◽  
Vol 11 (9) ◽  
pp. 4136
Author(s):  
Rosario Pecora
Keyword(s):  
Numerical Method ◽  
Initial Conditions ◽  
Impact Load ◽  
Numerical Models ◽  
Landing Gear ◽  
Design Stage ◽  
Impact Dynamics ◽  
State Variables ◽  
Adopted Model ◽  
The Impact

Oleo-pneumatic landing gear is a complex mechanical system conceived to efficiently absorb and dissipate an aircraft’s kinetic energy at touchdown, thus reducing the impact load and acceleration transmitted to the airframe. Due to its significant influence on ground loads, this system is generally designed in parallel with the main structural components of the aircraft, such as the fuselage and wings. Robust numerical models for simulating landing gear impact dynamics are essential from the preliminary design stage in order to properly assess aircraft configuration and structural arrangements. Finite element (FE) analysis is a viable solution for supporting the design. However, regarding the oleo-pneumatic struts, FE-based simulation may become unpractical, since detailed models are required to obtain reliable results. Moreover, FE models could not be very versatile for accommodating the many design updates that usually occur at the beginning of the landing gear project or during the layout optimization process. In this work, a numerical method for simulating oleo-pneumatic landing gear drop dynamics is presented. To effectively support both the preliminary and advanced design of landing gear units, the proposed simulation approach rationally balances the level of sophistication of the adopted model with the need for accurate results. Although based on a formulation assuming only four state variables for the description of landing gear dynamics, the approach successfully accounts for all the relevant forces that arise during the drop and their influence on landing gear motion. A set of intercommunicating routines was implemented in MATLAB® environment to integrate the dynamic impact equations, starting from user-defined initial conditions and general parameters related to the geometric and structural configuration of the landing gear. The tool was then used to simulate a drop test of a reference landing gear, and the obtained results were successfully validated against available experimental data.

scholarly journals Review on Urban Heat Island in China: Methods, Its Impact on Buildings Energy Demand and Mitigation Strategies

2021 ◽  
Vol 13 (2) ◽  
pp. 762
Author(s):  
Liu Tian ◽  
Yongcai Li ◽  
Jun Lu ◽  
Jue Wang
Keyword(s):  
Energy Consumption ◽  
Urban Heat Island ◽  
Building Energy ◽  
Design Stage ◽  
Heat Island ◽  
Building Energy Consumption ◽  
Rapid Urbanization ◽  
Substantial Impact ◽  
Urban Heat ◽  
The Impact

High population density, dense high-rise buildings, and impervious pavements increase the vulnerability of cities, which aggravate the urban climate environment characterized by the urban heat island (UHI) effect. Cities in China provide unique information on the UHI phenomenon because they have experienced rapid urbanization and dramatic economic development, which have had a great influence on the climate in recent decades. This paper provides a review of recent research on the methods and impacts of UHI on building energy consumption, and the practical techniques that can be used to mitigate the adverse effects of UHI in China. The impact of UHI on building energy consumption depends largely on the local microclimate, the urban area features where the building is located, and the type and characteristics of the building. In the urban areas dominated by air conditioning, UHI could result in an approximately 10–16% increase in cooling energy consumption. Besides, the potential negative effects of UHI can be prevented from China in many ways, such as urban greening, cool material, water bodies, urban ventilation, etc. These strategies could have a substantial impact on the overall urban thermal environment if they can be used in the project design stage of urban planning and implemented on a large scale. Therefore, this study is useful to deepen the understanding of the physical mechanisms of UHI and provide practical approaches to fight the UHI for the urban planners, public health officials, and city decision-makers in China.

Alfa fibers for Cereplast bio-composites reinforcement: Effects of chemical and biological treatments on the mechanical properties

2021 ◽  
pp. 096739112110060
Author(s):  
Mouna Werchefani ◽  
Catherine Lacoste ◽  
Hafedh Belguith ◽  
Chedly Bradai
Keyword(s):  
Charpy Impact ◽  
Impact Testing ◽  
Hot Water ◽  
Cellulose Content ◽  
Twin Screw ◽  
Electron Microscopy Analysis ◽  
Alfa Fibers ◽  
Charpy Impact Testing ◽  
Water Treatments ◽  
The Impact

The present work is a comparative study of the impact of Alfa fiber modifications on the Cereplast composites mechanical behavior. Various treatments have been employed, including mechanical, soda, saltwater-retting, hot-water treatments and enzymatic treatment using xylanase. Chemical and morphological analyses were carried out in order to determine the changes of the biochemical composition and the dimensions of fibers. Cereplast composites reinforced with Alfa fibers were fabricated using a twin-screw extrusion followed by an injection molding technique with a fiber load of 20 wt. %. Resulting materials were assessed by means of tensile, flexural and Charpy impact testing. Scanning Electron Microscopy analysis was carried out to investigate the interfacial properties of the composites. The results have shown a significant enhancement of mechanical strengths and rigidities for the xylanase-treated fiber composites, owing to the increase of cellulose content, the enhancement of defibrillation level and the improvement of matrix-fiber adhesion. The data proved that the technology of enzymes can be used as a powerful and eco-friendly approach to modify fiber surfaces and to increase their potential of reinforcement.

scholarly journals ‘I’m fine!’: Assertions of lack of support need among patients with chronic obstructive pulmonary disease: A mixed-methods study

2021 ◽  
pp. 174239532110003
Author(s):  
A Carole Gardener ◽  
Caroline Moore ◽  
Morag Farquhar ◽  
Gail Ewing ◽  
Efthalia Massou ◽  
...  
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Pulmonary Disease ◽  
Mixed Method ◽  
Self Report ◽  
Design Stage ◽  
Chronic Obstructive ◽  
Support Needs ◽  
Obstructive Pulmonary Disease ◽  
Stage 1 ◽  
The Impact

Objectives To understand how people with Chronic Obstructive Pulmonary Disease (COPD) disavow their support needs and the impact on care. Methods Two stage mixed-method design. Stage 1 involved sub-analyses of data from a mixed-method population-based longitudinal study exploring the needs of patients with advanced COPD. Using adapted criteria from mental health research, we identified 21 patients who disavowed their needs from the 235 patient cohort. Qualitative interview transcripts and self-report measures were analysed to compare these patients with the remaining cohort. In stage 2 focus groups (n = 2) with primary healthcare practitioners (n = 9) explored the implications of Stage 1 findings. Results Patients who disavowed their support needs described non-compliance with symptom management and avoidance of future care planning (qualitative data). Analysis of self-report measures of mental and physical health found this group reported fewer needs than the remaining sample yet wanted more GP contact. The link between risk factors and healthcare professional involvement present in the rest of the sample was missing for these patients. Focus group data suggested practitioners found these patients challenging. Discussion This study identified patients with COPD who disavow their support needs, but who also desire more GP contact. GPs report finding these patients challenging to engage.

Research on Five-Axis Dual-NURBS Adaptive Interpolation Algorithm for Flank Milling

2010 ◽  
Vol 443 ◽  
pp. 330-335 ◽  
Author(s):  
Yu Han Wang ◽  
Jing Chun Feng ◽  
Sun Chao ◽  
Ming Chen
Keyword(s):  
Tool Path ◽  
Flank Milling ◽  
Interpolation Algorithm ◽  
Machining Time ◽  
Surface Machining ◽  
Tool Axis ◽  
Scanning Area ◽  
Nurbs Interpolation ◽  
Milling Method ◽  
Five Axis

In order to exploit the advantages of five-axis flank milling method for space free surface machining to the full, a definition of non-equidistant dual-NURBS tool path is presented first. On this basis, the constraint of velocity of points on the tool axis and the constraint of scanning area of the tool axis are deduced. Considering both of these constraints, an adaptive feed five-axis dual-NURBS interpolation algorithm is proposed. The simulation results show that the feedrate with the proposed algorithm satisfies both of the constraints and the machining time is reduced by 38.3% in comparison with the constant feed interpolator algorithm.

scholarly journals Effects of temperature and impactor nose diameter on the impact behavior of PA6 and PP thermoplastic composites

2018 ◽  
Vol 51 (1) ◽  
pp. 64-74 ◽  
Author(s):  
Akar Dogan ◽  
Yusuf Arman
Keyword(s):  
Load Capacity ◽  
Testing Machine ◽  
Polyamide 6 ◽  
Impact Testing ◽  
Impact Behavior ◽  
Thermoplastic Composites ◽  
Test Machine ◽  
Effects Of Temperature ◽  
Impact Energies ◽  
The Impact

In this study, the effects of temperature and impactor nose diameter on the impact behavior of woven glass-reinforced polyamide 6 (PA6) and polypropylene (PP) thermoplastic composites were investigated experimentally. Impact energies are chosen as 10, 30, 50, 70, 90, 110, 130, and 170 J. The thickness of composite materials is 4 mm. Impact tests were performed using a drop weight impact testing machine, CEAST-Fractovis Plus, and the load capacity of test machine is 22 kN. Hemispherical impactor nose diameter of 12, 7, and 20 mm were used as an impactor. The tests are conducted at room temperature (20°C and 75°C). As a result, the PP composites of the same thickness absorbed more energy than PA6 composites. The amount of absorbed energy of PP and PA6 composites decreased with temperature.

On the impact testing of cyclotrimethylene trinitramine crystals with different internal qualities

2008 ◽  
Vol 103 (9) ◽  
pp. 093517 ◽  
Author(s):  
R. H. B. Bouma ◽  
A. G. Boluijt ◽  
H. J. Verbeek ◽  
A. E. D. M. van der Heijden
Keyword(s):  
Impact Testing ◽  
Cyclotrimethylene Trinitramine ◽  
The Impact
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