Design and Testing of an Enhanced Shape Memory Actuator Elastically Compensated by a Bi-Stable Rocker-Arm

2011 ◽  
Author(s):  
Giovanni Scire` Mammano ◽  
Eugenio Dragoni
Keyword(s):  
Fatigue Life ◽  
Shape Memory ◽  
Experimental Testing ◽  
Test Results ◽  
Output Force ◽  
Theoretical Predictions ◽  
Constant Output ◽  
Sma Actuator ◽  
Design And Testing ◽  
Good Agreement

This paper presents the design, the prototype construction and the experimental testing of a shape memory actuator implementing the concept of elastic compensation put forward in a previous publication by the authors. A two-SMA actuator, compensated by a spring-assisted bistable rocker-arm, is designed theoretically to provide nearly-constant output forces, then it is built and characterized under laboratory conditions. The test results are in good agreement with the theoretical predictions and show that, for given output force, the compensated actuator produces net strokes from 2.5 to 22 times greater than an identical uncompensated actuator. The stroke improvement increases dramatically with the generated output force. Weaknesses of the compensated design are the heavier average stress sustained by the SMA springs, which could impair the fatigue life, and a higher response time.

Design and testing of an enhanced shape memory actuator elastically compensated by a bistable rocker arm

2012 ◽  
Vol 24 (6) ◽  
pp. 704-716 ◽  
Author(s):  
Giovanni Scirè Mammano ◽  
Eugenio Dragoni
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Experimental Testing ◽  
Test Results ◽  
Shape Memory Alloy Actuator ◽  
Output Force ◽  
Theoretical Predictions ◽  
Constant Output ◽  
Design And Testing

This article presents the design, the prototype construction, and the experimental testing of a shape memory actuator implementing the concept of elastic compensation put forward in a previous publication by the authors. A two-shape memory alloy actuator, compensated by a spring-assisted bistable rocker arm, is designed theoretically to provide nearly constant output forces and then it is built and characterized experimentally under laboratory conditions. The test results closely agree with the theoretical predictions and show that for given output force, the compensated actuator produces net strokes from 2.5 to 22 times greater than a twin uncompensated actuator. The stroke improvement increases dramatically with the generated output force. Weaknesses of the compensated design are the heavier average stress sustained by the shape memory alloy springs, which could impair the fatigue life, and a higher response time.

Study on the stiffness degradation in concrete continuous beam with externally prestressed CFRP tendons under fatigue loading

2021 ◽  
pp. 136943322199249
Author(s):  
Xing Li ◽  
Jiwen Zhang ◽  
Jun Cheng
Keyword(s):  
Fatigue Life ◽  
Fatigue Loading ◽  
Load Level ◽  
Fiber Reinforced Polymer ◽  
Stiffness Degradation ◽  
Test Results ◽  
Reinforced Polymer ◽  
Continuous Beams ◽  
Practical Engineering ◽  
Good Agreement

This paper presents fatigue behaviors and the stiffness degradation law of concrete continuous beams with external prestressed carbon fiber-reinforced polymer (CFRP) tendons. Three specimens were tested under fatigue loading, and the influence of different load levels on the stiffness degradation and fatigue life were studied, and it was found that the stiffness degradation of three test specimens exhibited a three-stage change rule, namely rapid decrease, stable degradation, and sharp decline, but there are obvious differences in the rate and amplitude of stiffness degradation. The load level has a significant influence on the fatigue life of the test specimens. An analytical model with load level considered was proposed to calculate the residual stiffness and predict the stiffness degradation, which is in good agreement with the test results. The model of stiffness degradation presents a possible solution for practical engineering applications of concrete continuous beams with externally prestressed CFRP tendons subjected to different fatigue loadings.

The RMS Characteristics of Acceleration and Force Signals Depending on Tool Wear in Stable Cutting

1999 ◽  
Author(s):  
Richard Y. Chiou ◽  
Y. K. Kwon ◽  
Steven Y. Liang
Keyword(s):  
Tool Wear ◽  
Random Vibration ◽  
Cutting Tool ◽  
Flank Wear ◽  
Mean Square ◽  
Test Results ◽  
Tool Holder ◽  
Theoretical Predictions ◽  
Acceleration Signals ◽  
Good Agreement

Abstract An analysis of the RMS (Root Mean Square) characteristics of fluctuating force and acceleration signals for a cutting tool engaged in a turning operation in the presence of wear flat on the tool flank is presented in this research. The RMS of acceleration and force signals obtained from experiments in stable cutting is compared with theoretical machining models due to the tool wear effect. The RMS is a measure of the energy, at the tool tip-workpiece interface along the flank, to the random vibration of the cantilever portion of the tool holder. Increasing flank wear results in an increasing stability and decreasing RMS in the thrust direction, dependent upon flank wear-land width. The RMS force and acceleration signals in machining is calculated by frequency band RMS method at the first natural frequency of the cantilever portion of the tool holder in the frequency domain. By reference to experimental evidence, the theoretical predictions show generally good agreement with test results.

scholarly journals Advanced Modeling and Simulation of Rockfall Attenuator Barriers Via Partitioned DEM-FEM Coupling

2021 ◽  
Vol 7 ◽  
Author(s):  
Klaus Bernd Sautter ◽  
Helene Hofmann ◽  
Corinna Wendeler ◽  
Peter Wilson ◽  
Philipp Bucher ◽  
...  
Keyword(s):  
Modeling And Simulation ◽  
Experimental Testing ◽  
Experimental Tests ◽  
Simulation Method ◽  
Design Decision ◽  
Test Results ◽  
The Finite Element Method ◽  
Shape Sphere ◽  
Good Agreement ◽  
Element Method

Attenuator barriers, in contrast to conventional safety nets, tend to smoothly guide impacting rocks instead of absorbing large amounts of strain energy arresting them. It has been shown that the rock’s rotation plays an important role in the bearing capacity of these systems. Although experimental tests have to be conducted to gain a detailed insight into the behavior of both the structures and the rock itself, these tests are usually costly, time-consuming, and offer limited generalizability to other structure/environment combinations. Thus, in order to support the engineer’s design decision, reinforce test results and confidently predict barrier performance beyond experimental configurations this work describes an appropriate numerical modeling and simulation method of this coupled problem. For this purpose, the Discrete Element Method (DEM) and the Finite Element Method (FEM) are coupled in an open-source multi-physics code. In order to flexibly model rocks of any shape, sphere clusters are used which employ simple and efficient contact algorithms despite arbitrarily complicated shapes. A general summary of the FEM formulation is presented as well as detailed derivations of finite elements particularly pertinent to rockfall simulations. The presented modeling and coupling method is validated against experimental testing conducted by the company Geobrugg. Good agreement is achieved between the simulated and experimental results, demonstrating the successful practical application of the proposed method.

Slip modulus in bolted timber joints

1992 ◽  
Vol 19 (6) ◽  
pp. 960-964 ◽  
Author(s):  
D. B. Van Dyer
Keyword(s):  
Test Results ◽  
Lateral Loads ◽  
Initial Load ◽  
Theoretical Predictions ◽  
Mechanically Fastened ◽  
Timber Joints ◽  
Interlayer Slip ◽  
Laterally Loaded ◽  
Wood Columns ◽  
Good Agreement

This paper is concerned with the initial load–slip behaviour of laterally loaded bolted timber joints and deals specifically with verifying a theory for determining the values of slip modulus in mechanically fastened timber joints. Such a theory is essential in dealing with the phenomenon of interlayer slip, which occurs in built-up timber columns with nonrigid joints. The concept of a beam on an elastic foundation is used to evaluate the slip modulus. The theoretical predictions are compared with the test results of 75 timber joints. Good agreement is observed between the experiment and the theory. Key words: timber joints, bolts, nails, wood, interlayer slip, slip modulus, built-up wood columns, shear, lateral loads.

Impact of Length Mismatch on the Fatigue Life of Parallel Shape Memory Alloy Wires

2013 ◽  
Author(s):  
Christopher B. Churchill ◽  
Anthony Bedegi ◽  
Xiujie Gao
Keyword(s):  
Fatigue Life ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Electric Motor ◽  
Measurable Effect ◽  
Mechanical Interaction ◽  
Potential Cost ◽  
In Series ◽  
Thermal Lag ◽  
Sma Actuator

Shape memory alloy (SMA) actuator wires promise substantial size, weight, and potential cost advantages over their solenoid and electric motor counterparts. Designing actuators which fully realize these advantages is hampered by a limited understanding of how interactions between wires and their environment affect cyclic lifetime. For example, many devices use two SMA wires mechanically in parallel but electrically in series. This has practical advantages in simplified electrical routing and thermal lag. However, it complicates modeling in that wires interact both electrically and mechanically. Here we study the effect of a mismatch in length between two SMA wires in parallel. We perform a series of fatigue experiments to show that mismatch of up to 0.75%, at the chosen set of conditions, has no measurable effect on cycle life. We also perform a series of simulations to show how the mechanical interaction between the two parallel wires tends to suppress, rather than amplify, any impact of length mismatch.

An R-Curve Approach for Fracture of Ultra High Performance Cementitious Composites

2007 ◽  
Vol 348-349 ◽  
pp. 825-828
Author(s):  
Xiang Guo Wu ◽  
Sang Mook Han ◽  
Sung Wook Kim ◽  
Su Tae Kang
Keyword(s):  
Stress Intensity Factor ◽  
High Performance ◽  
Steel Fiber ◽  
Unit Area ◽  
Cementitious Composites ◽  
Test Results ◽  
Linear Distribution ◽  
Three Point Bending ◽  
Theoretical Predictions ◽  
Good Agreement

An R-curve formula for ultra high performance cementitious composites is derived in this paper. The fracture mechanics based on R-curve is used to predict the load-deflection relation of ultra high performance cementitious composites. The reductions of stress intensity factor and CTOD by steel fiber reinforcement are assumed as conforming linear distribution along crack propagation. The effective numbers of steel fiber on unit area based uniform distribution is used here. Results of the theoretical predictions show a good agreement with test results of three point bending beam of UHPCC. The modified R-curve formula for UHPCC can be a reference for future study of fracture performances of UHPCC.

A theoretical model for the tread slip and the effective rolling radius of the tyres in free rolling

2017 ◽  
Vol 231 (11) ◽  
pp. 1461-1470 ◽  
Author(s):  
Yintao Wei ◽  
Christian Oertel ◽  
Xuebing Li ◽  
Liangyao Yu
Keyword(s):  
Lateral Displacement ◽  
Rotational Velocity ◽  
Rolling Friction ◽  
Test Results ◽  
Inflation Pressure ◽  
Displacement Gradient ◽  
Theoretical Predictions ◽  
Circumferential Displacement ◽  
Increasing Load ◽  
Good Agreement

A rigid–elastic coupling theory for the rolling kinematics of tyres, by which the tread slip, the effective rolling radius and the ply steering of the tyres can be analysed, was formulated. The theory demonstrates that, during free-rolling motion, the coupling between the rotational velocity Ω along the wheel axis and the circumferential displacement gradient generates the longitudinal tread slip, and the coupling between the rotational velocity Ω along the wheel axis and the lateral displacement gradient generates the lateral tread slip and the ply steering. Revisiting the tread slip phenomenon using the newly proposed method numerically proves the kinematic mechanism of the rolling friction. It can be found that the effective rolling radius Re increases with increasing inflation pressure and decreases with increasing load; the sensitivity of Re to the inflation pressure is greater than the sensitivity of Re to the load. The good agreement between the theoretical predictions and the test results for the effective rolling radius of the radial tyres of a car is found. The coupling of the displacement gradient and the rigid rolling kinematics causes non-symmetry of the lateral tread slip which, in turn, leads to the ply steering and the residual aligning moment; these depend on the belt and tread design. The proposed theory and approach provide a quick and powerful tool for analysing the tread slip, the effective rolling radius and the ply steering of the tyres under free rolling.

Set Point Force Control of Shape Memory Alloy Actuator Using Fuzzy Controller

2013 ◽  
Vol 433-435 ◽  
pp. 166-173
Author(s):  
Fei Gao ◽  
Hua Deng
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Control Strategy ◽  
Force Control ◽  
Fuzzy Controller ◽  
Point Force ◽  
Control Voltage ◽  
Set Point ◽  
Output Force ◽  
Sma Actuator

Shape memory alloy (SMA) has a property that when the temperature of SMA is stabilized, the fraction of Martensite phase keeps the same, and output force of SMA actuator also keeps constant. Based on that, a control strategy for set point force control of SMA actuators is proposed that during the process of driving, to stabilize output forces of SMA actuator, some voltages called balance voltages which can stabilize the temperature of SMA at the point will be input to SMA actuator. Besides, in order to shorten force rising times, before output force reaches the desired force, the max control voltage will be input to SMA actuator. Those balance voltages are related to output forces, therefore, its impossible to get all balance voltages. In this thesis, some balance voltages at different output forces are acquired by experiments. Based on this data, a series of fuzzy rules are used to fit the curve of all balance voltages. Since the balance voltages line is not accurate, balance voltages are needed to be slightly adjusted near the fitting curve according to force errors. Based on the control strategy, a fuzzy controller, with two input variables-desired force and force error and one output-control voltage, is designed. Finally, for testing the performance of the proposed controller, an experimental prototype is implemented. Experiment results show that the proposed controller is successfully applied to SMA actuator, and have a better control performance than conventional PI controller.

Design and Testing of Gears With Non-Standard Profile

2007 ◽  
Author(s):  
P. Zak ◽  
V. Dynybyl
Keyword(s):  
Experimental Testing ◽  
Test Results ◽  
Standard Geometry ◽  
Real Geometry ◽  
Testing Stand ◽  
Digital Documentation ◽  
Tooth Flank ◽  
Standard Profile ◽  
Flank Surface ◽  
Design And Testing

This paper introduces a sophisticated methodology that guides the design of the non-standard geometry of cylindrical gearwheels, methodology for the evaluation of operation life depending on flank damage (pitting) in shortened lifetime tests of gearwheels and also number of other research results. The methodology for the design of gearwheels modifications is solved by using FEM system and takes into account real geometry of the whole gearbox and its component. Processed samples designs are tested in experimental testing stand and compared with samples which are designed using DIN 3990 standard Method B. The test results serves for verification of created designs. The back-to-back test-rig allowing smooth control of virtual power up to 785 kW (1053 HP) is also described. The methodology for evaluation of pitting area is solved by using digital documentation and automatic evaluation of damaged tooth flank surface.

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