Towards a Synthesis Method of Kresling Tower Used as a Compliant Building Block

In this paper, the use of the Kresling tower origami as a building block for compliant mechanism design is considered. Two contributions are introduced to develop a synthesis method of such a building block. First, models to link the origami pattern geometry to the Kresling tower kinematics are derived. The position of stable configurations, the lead angle of its helical motion are expressed as functions of the pattern parameters. Experimental validation of the models is performed. Second, a modification of pattern by local adjustment of fold geometry is introduced. This aims at modifying the origami stiffness without affecting the kinematics. The use of modified fold geometries is experimentally investigated. The capacity to strongly modify the stiffness level is observed, which is encouraging to go towards a synthesis method with decoupling of kinematics and stiffness selection.

Cutting force prediction considering force-deflection coupling in five-axis milling with fillet-end cutter

With the increasing demand for higher quality and performance of equipment and assembly in aerospace, shipbuilding, medical and other fields, the machining accuracy of parts is facing higher requirements. It is particularly important to predict the cutting force accurately, which is the main physical quantity in the machining process and basis of process inspection and quality control. In this paper, the cutting force model in five-axis milling with fillet-end cutter is proposed, which reveals the law of force-deflection coupling. Firstly, the initial cutter deflection model induced by the ideal cutting force ignoring the effect of deflection is built based on analysis of the geometric characteristics of fillet-end cutter. Then the undeformed chip thickness model is educed considering the cutter posture and cutter deflection. Further, the iterative method is utilized to resolve the coupling relationship between cutter deflection and cutting force. Finally, the cutting force model under force-deflection coupling is established for achieving more accurate prediction. To verify the effectiveness of the proposed cutting force model, the milling experiment is carried out on a five-axis milling center. The measured cutting force values are utilized to inspect the accuracy of prediction models considering and not considering force-deflection coupling respectively. The results show that the proposed method could improve the prediction accuracy of cutting force, which show the effectiveness of taking force-deflection coupling law into consideration clearly. The influence of cutter posture on cutting force is analyzed using the proposed cutting force model. The cutting force decreases with the increasing of lead angle or tilt angle, and the influence of tilt angle is greater than that of lead angle under experimental conditions of five-axis milling using the set process parameters.

The effect of body acceleration on the dispersion of solute in a non-Newtonian blood flow through an artery

Purpose The purpose of this study is to solve convective diffusion equation analytically by considering appropriate boundary conditions and using the Taylor-Aris method to determine the solute concentration, the effective and relative axial diffusivities. Design/methodology/approach >An analysis has been conducted on how body acceleration affects the dispersion of a solute in blood flow, which is known as a Bingham fluid, within an artery. To solve the system of differential equations analytically while validating the target boundary conditions, the blood velocity is obtained. Findings The blood velocity is impacted by the presence of body acceleration, as well as the yield stress associated with Casson fluid and as such, the process of dispersing the solute is distracted. It graphically illustrates how the blood velocity and the process of solute dispersion are affected by various factors, including the amplitude and lead angle of body acceleration, the yield stress, the gradient of pressure and the Peclet number. Originality/value It is witnessed that the blood velocity, the solute concentration and also the effective and relative axial diffusivities experience a drop when either of the amplitude, lead angle or the yield stress rises.

Relationship between Upstream Swimming Behaviors of Juvenile Grass Carp and Characteristic Hydraulic Conditions of a Vertical Slot Fishway

The successful fish upstream movement through a dam/gate is closely associated with the hydraulic conditions of a fishway. To improve the passage efficiency, this study investigated the upstream swimming behaviors of juvenile grass carp, a representative fish of four major Chinese carps, under characteristic hydraulic conditions of a designed vertical slot fishway model. The impacts of different discharges and baffle lead angles on the successful movement of test fish were analyzed, and the selection of the movement trajectory was studied through overlay of their upstream swimming trajectories on the water flow field resulting from numerical modeling. We found that under the same discharge, the percentage of successful test fish movement with a lead angle of 45° was higher than 60° and 30°. Within a fixed lead angle, the higher the discharge, the lower the percentage of successful movement. During upstream movement, the test fish had a preferred water velocity of 0.01–0.45 m/s in the pool, and avoided areas where the turbulence kinetic energy (TKE) was greater than 0.012 m2/s2. These results provide a basis for the hydraulic design of vertical slot fishways and a reference for studying swimming behaviors of other fish species.

Influence of dynamic geometric parameters on multi-axis machining processes

By means of experimental, geometric and simulation models, roughness values of third and fourth order deviations are determined. The simulation environment is developed from the integration and simulated verification (ISV) in software NX 11 and the geometric approximations are validated through the analysis confocal microscopy.An experiment design is carried out to determine the influence of the dynamic geometric factors: transverse feed (Ae), lead angle and tilt angle, with a flat end milling tool with 1 mm diameter. In the experiment a 3k factorial model is presented to specify the factor with the greatest influence on the roughness. As a result, an optimum (minimum) roughness value is obtained. The lead angle has a moderate influence. Fourth order deviations are associated with the feed per tooth, with a constant angular speed of 5,000 rpm

Analysis and Control of an In-Pipe Wheeled Robot With Spiral Moving Capability

This article presents analysis and control of a wheeled robot that can move spirally inside the pipeline. The wheeled robot considered is composed of two mechanical bodies, a pair of differential-drive wheels, a lifting motor, and a steering wheel. The mechatronic design allows the robot to easily press against the inner wall and spiral along pipelines of arbitrary inclination angles. Kinematic analysis shows how the lead angle of the differential-drive wheels and the steering angle should be coordinated so as to achieve stable spiraling. The steady-state force analysis further gives an analytic expression for the threshold torque needed for supporting the robot at different inclination angles. To ensure successful operation of the robot, four control systems that respectively regulate the spiraling speed, the lifting torque, the steering angle, and the lead angle are devised. Particularly for the lead angle control, it is theoretically proved that the feedback measurement can be obtained by performing algebraic operation on signals from a multi-axis gyro. A prototype robot is constructed and is controlled based on the analysis results. Experiments are conducted to verify the robot’s performance on moving spirally in pipelines of different inclination angles.

Optimization Method of Rotational Axis Motion in 5-Axis Controlled Machining to Keep Command Tool Feed Rate

In recent machining processes, 5-axis controlled machine tool is widely used for machining complicated workpiece shape with curved surface. In such process, to achieve high productivity, planning method of cutting conditions to satisfy both following the commanded tool feed rate in machining process and realization of good surface roughness are required. In conventional study, it is known that lead angle of tool posture against local machined surface influence the surface roughness. Then, common commercial CAM systems have already functioned to avoid interference and control the lead angle in each cutter location. However, in the generated cutter locations by the conventional algorithms, when the tool posture changes rapidly, there is a problem that actual feed rate does not reach the command value and machining time becomes longer than expected. In this paper, we propose the new tool posture correction algorithm. In the proposed method, first, the rotational axis that causes the feed speed rate decline is specified by preliminary experiments. And, the jerk value that is the threshold for the feed speed decline is investigated. After that, for the NC program, the command value of the target axis is modified within a range where interference of cutting tool does not occur, thereby preventing a decline in the actual feed rate. This paper describes an outline of the proposed modification method and the effect of the modification of the target axis positions on the lead angle and the actual feed rate.

Evaluation of Surface Roughness in Five-Axis Ball-End Milling

Unlike three-axis machining, five-axis machining allows the end tool or workpiece to be oriented at any angle relative to the machine axis OZ. It can be achieved by changing the values of the tool tilt angle and lead angle relative to the surface normal in the contact zone of the tool surface and the workpiece, taking into account the direction of the table feed. The article presents experimental results of analyzing the influences of tool orientation on transverse roughness during ball end milling using 2-flute and 4-flute 8 mm diameter mills. The analysis the arithmetic mean deviation of the assessed profile at various values of tool tilt angle and lead angle showed that the position of the tool point with a zero cutting speed significantly affects the surface quality. The results of the evaluation of the tool orientation influence on the surface roughness enable the selection of optimal tool orientation angles when developing control programs for end milling of free-form surfaces on five-axis CNC milling machines.