Improved Rotary Contact Method for 5-Axis Sculptured Surfaces Machining

2013 ◽  
Vol 135 (5) ◽  
Author(s):  
Wengang Fan ◽  
Peiqing Ye ◽  
Chenxi Fang ◽  
Shaohua Shi
Keyword(s):  
Surface Quality ◽  
Contact Point ◽  
Test Surface ◽  
Contact Method ◽  
Sculptured Surfaces ◽  
Tool Positioning ◽  
Contact Points ◽  
Positioning Strategy ◽  
Cutting Surface ◽  
Cutting Experiment

The 5-axis tool positioning strategy named rotary contact method (RCM) for sculptured surfaces machining has been developed in our previous paper (Fan et al., 2012, “Rotary Contact Method for 5-Axis Tool Positioning,” Trans. ASME J. Manuf. Sci. Eng., 134(2), p. 021004). The RCM finds the optimal tool positions by rotating the tool backward based on the offset surface, and can generate big machined strip width. However, the RCM can only guarantee a contact point because of the design surface's geometric asymmetry in most cases, which leads to the poor surface quality. To resolve this problem, the improved rotary contact method (IRCM) is developed in this paper. The parametric equation of the circular curve of the toroidal cutter defined by the backward and the sideward tilt angle of the tool is strictly deduced. According to the nested optimization of the two tool's angles, there are two contact points found between the tool's cutting surface and the design surface around the feed direction without gouging. Tool positions investigation, machining simulation and cutting experiment are all performed based on a test surface. The results verify the correctness and effectiveness of the IRCM and show that the IRCM can apparently improve the surface quality compared to the RCM.

Numerical Simulation of Convective Heat Transfer in Structured Packed Beds of Particles With Different Particle Contact Treatment Methods

2012 ◽  
Author(s):  
S. S. Bu ◽  
J. Yang ◽  
S. Y. Li ◽  
Q. W. Wang
Keyword(s):  
Heat Transfer ◽  
Contact Point ◽  
Point Contact ◽  
Treatment Method ◽  
Contact Method ◽  
Packed Beds ◽  
Treatment Methods ◽  
Contact Points ◽  
Flow And Heat Transfer ◽  
Sphere Contact

The treatment of sphere contact is a crucial issue on the numerical analysis of the flow and heat transfer in packed beds of particles. In this work, the effects of three different methods including introducing a gap, area contacting and cylindrically bridging on the flow and heat transfer performances of structured packed beds of particles are investigated with CFD methods. The simulation results have shown that the influence of different treatment methods on the contact point on flow and heat transfer gets greater as the porosity decreases and the Reynolds number increases. There are no large differences among these three methods on the pressure drop and heat transfer under laminar flow regime. Compared with the experimental results, cylindrically bridging method is proved to be reasonable to simplify the sphere–sphere contact points. Therefore, cylindrically bridging treatment method is encouraged to be used instead of point contact method between particles with CFD analysis in structured packed beds of particles.

scholarly journals Slipping–rolling transitions of a body with two contact points

2021 ◽  
Author(s):  
Mate Antali ◽  
Gabor Stepan
Keyword(s):  
Rigid Body ◽  
Contact Point ◽  
Static Friction ◽  
Rigid Body Dynamics ◽  
Contact Forces ◽  
Friction Forces ◽  
Contact Points ◽  
Body Dynamics ◽  
Coulomb Model ◽  
Rigid Surfaces

AbstractIn this paper, the general kinematics and dynamics of a rigid body is analysed, which is in contact with two rigid surfaces in the presence of dry friction. Due to the rolling or slipping state at each contact point, four kinematic scenarios occur. In the two-point rolling case, the contact forces are undetermined; consequently, the condition of the static friction forces cannot be checked from the Coulomb model to decide whether two-point rolling is possible. However, this issue can be resolved within the scope of rigid body dynamics by analysing the nonsmooth vector field of the system at the possible transitions between slipping and rolling. Based on the concept of limit directions of codimension-2 discontinuities, a method is presented to determine the conditions when the two-point rolling is realizable without slipping.

scholarly journals Cavitation between cylinder-liner and piston-ring in a new designed optical IC engine

2021 ◽  
pp. 146808742110080
Author(s):  
Jamshid Malekmohammadi Nouri ◽  
Ioannis Vasilakos ◽  
Youyou Yan
Keyword(s):  
High Speed ◽  
Contact Point ◽  
Cylinder Liner ◽  
Optical Methods ◽  
Engine Management System ◽  
Great Success ◽  
Ic Engine ◽  
Contact Points ◽  
Lubricant Flow ◽  
Cavitation Intensity

A new engine block with optical access has been designed and manufactured capable of running up to 3000 r/min with the same specification as the unmodified engine. The optical window allowed access to the full length of the liner over a width of 25 mm to investigate the lubricant flow and cavitation at contact point between the rings and cylinder-liner. In addition, it allowed good access into the combustion chamber to allow charged flow, spray and combustion visualisation and measurements using different optical methods. New custom engine management system with build in LabView allowed for the precise full control of the engine. The design of the new optical engine was a great success in producing high quality images of lubricant flow, cavitation formation and development at contact point at different engine speeds ranging from 208 to 3000 r/min and lubricant temperatures (30°C–70°C) using a high-speed camera. The results under motorised operation confirmed that there was no cavitation at contact points during the intake/exhaust strokes due to low in-cylinder presure, while during compression/expansion strokes, with high in-cylinder pressure, considerable cavities were observed, in particular, during the compression stroke. Lubricant temperatures had the effect of promoting cavities both in their intensity and covered ring area up to 50°C as expected. Beyond that, although the cavitation intensity increases further with temperature, its area reduces due to possible collapse of the cavitating bubbles at higher temperature. The change of engine speed from 208 to 800 r/min increased cavitating area considerably by 52% of the ring area and was further increased by 19% at 1000 r/min. After that, the results showed very small increase in cavitation area (1.3% at 2000 r/min) with similar intensity and distribution across the ring.

scholarly journals The macroscopic shape of assemblies formed from microparticles based on host–guest interaction dependent on the guest content

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Takahiro Itami ◽  
Akihito Hashidzume ◽  
Yuri Kamon ◽  
Hiroyasu Yamaguchi ◽  
Akira Harada
Keyword(s):  
Molecular Recognition ◽  
Smart Materials ◽  
Self Assembly ◽  
Early Stage ◽  
Contact Point ◽  
Sodium Acrylate ◽  
Contact Points ◽  
Assembly Behavior ◽  
Small Clusters ◽  
Macroscopic Shape

AbstractBiological macroscopic assemblies have inspired researchers to utilize molecular recognition to develop smart materials in these decades. Recently, macroscopic self-assemblies based on molecular recognition have been realized using millimeter-scale hydrogel pieces possessing molecular recognition moieties. During the study on macroscopic self-assembly based on molecular recognition, we noticed that the shape of assemblies might be dependent on the host–guest pair. In this study, we were thus motivated to study the macroscopic shape of assemblies formed through host–guest interaction. We modified crosslinked poly(sodium acrylate) microparticles, i.e., superabsorbent polymer (SAP) microparticles, with β-cyclodextrin (βCD) and adamantyl (Ad) residues (βCD(x)-SAP and Ad(y)-SAP microparticles, respectively, where x and y denote the mol% contents of βCD and Ad residues). Then, we studied the self-assembly behavior of βCD(x)-SAP and Ad(y)-SAP microparticles through the complexation of βCD with Ad residues. There was a threshold of the βCD content in βCD(x)-SAP microparticles for assembly formation between x = 22.3 and 26.7. On the other hand, the shape of assemblies was dependent on the Ad content, y; More elongated assemblies were formed at a higher y. This may be because, at a higher y, small clusters formed in an early stage can stick together even upon collisions at a single contact point to form elongated aggregates, whereas, at a smaller y, small clusters stick together only upon collisions at multiple contact points to give rather circular assemblies. On the basis of these observations, the shape of assembly formed from microparticles can be controlled by varying y.

Wheel-Rail Multi-Point Contact Method for Railway Turnouts

2011 ◽  
Vol 97-98 ◽  
pp. 378-381
Author(s):  
Zhi Wei Chen ◽  
Linan Li ◽  
Shi Gang Sun ◽  
Jun Long Zhou
Keyword(s):  
Calculation Method ◽  
Normal Force ◽  
Contact Point ◽  
Point Contact ◽  
Contact Model ◽  
Contact Method ◽  
Elastic Contact ◽  
Simulation Calculation ◽  
Acute Change

A calculation method of wheel-rail multi-point contact based on the elastic contact model is introduced. Moreover, the simulation calculation of vehicles passing through branch lines of No.18 turnouts is carried out. The result showed that the acute change of wheel-rail normal force caused by the transfers of wheel-rail contact point between two rails can be avoid by wheel-rail multi-point contact method, and the transfers of wheel-rail normal force between two rails is smoother. The validity of wheel-rail multi-point contact method is verified.

Spatial Kinematic Analysis of Threaded Fastener Assembly

2005 ◽  
Vol 128 (1) ◽  
pp. 116-127 ◽  
Author(s):  
Stephen Wiedmann ◽  
Bob Sturges
Keyword(s):  
Design Space ◽  
Compliant Mechanisms ◽  
Contact Point ◽  
Three Dimensional ◽  
Vertical Movement ◽  
Initial Contact ◽  
Geometric Problem ◽  
Intelligent Sensor ◽  
Contact State ◽  
Contact Points

Compliant mechanisms for rigid part mating exist for prismatic geometries. A few instances are known of mechanisms to assemble screw threads. A comprehensive solution to this essentially geometric problem comprises at least three parts: parametric equations for nut and bolt contact in the critical starting phase of assembly, the possible space of motions between these parts during this phase, and the design space of compliant devices which accomplish the desired motions in the presence of friction and positional uncertainty. This work concentrates on the second part in which the threaded pair is modeled numerically, and contact tests are automated through software. Tessellated solid models were used during three-dimensional collision analysis to enumerate the approximate location of the initial contact point. The advent of a second contact point presented a more constrained contact state. Thus, the bolt is rotated about a vector defined by the initial two contact points until a third contact location was found. By analyzing the depth of intersection of the bolt into the nut as well as the vertical movement of the origin of the bolt reference frame, we determined that there are three types of contacts states present: unstable two-point, quasi-stable two-point, stable three point. The space of possible motions is bounded by these end conditions which will differ in detail depending upon the starting orientations. We investigated all potential orientations which obtain from a discretization of the roll, pitch, and yaw uncertainties, each of which has its own set of contact points. From this exhaustive examination, a full contact state history was determined, which lays the foundation for the design space of either compliant mechanisms or intelligent sensor-rich controls.

Multi-Agent Form Closure Capture of a Generic 2D Polygonal Object Based on Projective Path Planning

2006 ◽  
Author(s):  
Pankaj Sharma ◽  
Anupam Saxena ◽  
Ashish Dutta
Keyword(s):  
Path Planning ◽  
Contact Point ◽  
Point Contact ◽  
Object Boundary ◽  
Actual Object ◽  
Contact Points ◽  
Correct Orientation ◽  
Novel Approach ◽  
Form Closure ◽  
Multi Agent

The study of multi-agent capture and manipulation of an object has been an area of active interest for many researchers. This paper presents a novel approach using Genetic Algorithm to determine the optimal contact points and the total number of agents (mobile robots) required to capture a stationary generic 2D polygonal object. After the goal points are determined the agents then reach their respective goals using a decentralized projective path planning algorithm. Form closure of the object is obtained using the concept of accessibility angle. The object boundary is first expanded and the robots reach the expanded object goal points and then converge on the actual object. This ensures that the agents reach the actual goal points at the same time and have the correct orientation. Frictionless point contact between the object and robots is assumed. The shape of the robot is considered a circle such that it can only apply force in outward radial direction from its center and along the normal to the object boundary at the contact point. Simulations results are presented that prove the effectiveness of the proposed method.

Unraveling Paradoxical Theories for Rigid Body Collisions

1991 ◽  
Vol 58 (4) ◽  
pp. 1049-1055 ◽  
Author(s):  
W. J. Stronge
Keyword(s):  
Frictional Force ◽  
Contact Point ◽  
Tangential Velocity ◽  
Velocity Slip ◽  
Rigid Bodies ◽  
Contact Points ◽  
Before And After ◽  
Limited Applicability ◽  
Work Done ◽  
Impulsive Reaction

A collision between two rigid bodies has a normal impulsive reaction at the contact point (CP). If the bodies are slightly rough and the contact points have a relative tangential velocity (slip), there is also a frictional force that opposes slip. Small initial slip can halt before contact terminates; when slip halts the frictional force changes and the collision process is separated into periods before and after halting. An energetically consistent theory for collisions with slip that halts is based on the work done by normal (nonfrictional) forces during restitution and compression phases. This theory clearly separates dissipation due to frictional forces from that due to internal irreversible deformation. With this theory, both normal and tangential components of the impulsive reaction always dissipate energy during collisions. In contrast, Newton’s impact law results in calculations of paradoxical increases in energy for collisions where slip reverses. This law relates normal components of relative velocity for the CP at separation and incidence by a constant (the coefficient of restitution e). Newton’s impact law is a kinematic definition for e that generally depends on the slip process and friction; consequently it has limited applicability.

scholarly journals SARPPIC: Exploiting COVID-19 Contact Tracing Recommendation through Social Awareness

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Nana Yaw Asabere ◽  
Amevi Acakpovi ◽  
Emmanuel Kwaku Ofori ◽  
Wisdom Torgby ◽  
Marcellinus Kuuboore ◽  
...  
Keyword(s):  
Contact Point ◽  
Healthcare Facility ◽  
Contact Tracing ◽  
Contact Points ◽  
Trace Back ◽  
Effective Contact ◽  
Hygiene Measures ◽  
Real World Datasets ◽  
Recommender Algorithm ◽  
Prevention Methods

Globally, the current coronavirus disease 2019 (COVID-19) pandemic is resulting in high fatality rates. Consequently, the prevention of further transmission is very vital. Until vaccines are widely available, the only available infection prevention methods include the following: contact tracing, case isolation and quarantine, social (physical) distancing, and hygiene measures (washing of hands with soap and water and using alcohol-based hand sanitizers). Contact tracing, which is key in preventing the spread of COVID-19, refers to the process of finding unreported people who maybe infected by using a verified case to trace back possible infections of contacts. Consequently, the wide and fast spread of COVID-19 requires computational approaches which utilize innovative algorithms that build a memory of proximity contacts of cases that are positive. In this paper, a recommender algorithm called socially aware recommendation of people probably infected with COVID-19 (SARPPIC) is proposed. SARPPIC initially utilizes betweenness centrality in a social network to measure the number of target contact points (nodes/users) who have come into contact with an infected contact point (COVID-19 patient). Then, using contact durations and contact frequencies, tie strengths of the same contact points above are also computed. Finally, the above algorithmic computations are hybridized through profile integration to generate results for effective contact tracing recommendations of possible COVID-19-infected patients who will require testing in a healthcare facility. Benchmarking experimental results in the paper demonstrate that, using two interconnected relevant real-world datasets, SARPPIC outperforms other relevant methods in terms of suitable evaluation metrics such as precision, recall, and F-measure.

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