scholarly journals Design Optimization of Flexure Springs for Free-Piston Stirling Engines and Experimental Evaluations with Fatigue Testing

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 5156
Author(s):  
Chang-Whan Lee ◽  
Dong-Jun Kim ◽  
Sung-Kwon Kim ◽  
Kyuho Sim
Keyword(s):  
Fatigue Testing ◽  
Design Method ◽  
Heat Engine ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Geometric Constraints ◽  
Outer Diameter ◽  
Optimized Design ◽  
Free Piston ◽  
Regenerative Heat

The free-piston Stirling engine is a closed-cycle regenerative heat engine that converts heat energy into mechanical work, and requires a spring element for vibratory operations of the displacer and power pistons. In this study, the geometry of the flexural spring design was optimized through structural finite element analyses and fatigue test evaluations. First, we constructed a target design space considering the required natural frequency of the displacer spring assembly under the geometric constraints of total mass and module height. The design of experiments was employed to construct simulation cases for design factors such as the outer diameter, thickness, and number of spirals in the spring sheet. As a result, the optimized design values were obtained to satisfy the design requirements. We also fabricated a test spring specimen and conducted fatigue tests using a linear actuator system developed to have the same motion as the engine. The test results indicated that the optimized spiral spring had no fracture under operating conditions with the design piston amplitude, revealing the effectiveness of the design method.

Fatigue Testing of Polymeric Hollow Fibre Heat Transfer Surfaces by Pulsating Pressure Loads

2016 ◽  
Vol 821 ◽  
pp. 3-9 ◽  
Author(s):  
Tereza Brožová ◽  
Tomáš Luks ◽  
Ilya Astrouski ◽  
Miroslav Raudenský
Keyword(s):  
Heat Transfer ◽  
Fatigue Testing ◽  
Fatigue Loading ◽  
Hollow Fibre ◽  
Fatigue Tests ◽  
Outer Diameter ◽  
Hollow Fibres ◽  
Different Temperatures ◽  
Hot Bath ◽  
Number Of Cycles

This article deals with fatigue tests of polymeric hollow fibre heat transfer surfaces. The hollow fibres have an outer diameter between 0.5-0.8 mm and wall thickness 10 % of the outer diameter. These plastic heat transfer surfaces have some limitations but also many benefits. One of the limitations is the durability of plastic under fatigue loading. The heat transfer surfaces were subjected to pulsating pressure loads under different conditions (level of pressure, ambient temperature, number of cycles). Firstly, only an internal hydraulic pulsating load was applied and the behaviour of the hollow fibres was observed, focusing especially on the presence of leaks, ruptures, etc.Then, other conditions of operations were added. The heat transfer surfaces were immersed in a hot bath and loaded by internal pulsating pressure and high temperature simultaneously. Testing under different temperatures is important because the temperature significantly affects the material properties. The presence of leaks, ruptures and other possible damage was monitored as with previous tests.

A Study of Heat Driven Pressure Oscillations in a Gas

1970 ◽  
Vol 92 (3) ◽  
pp. 536-540 ◽  
Author(s):  
K. T. Feldman ◽  
R. L. Carter
Keyword(s):  
Mechanical Energy ◽  
Heat Engine ◽  
Experimental Studies ◽  
Operating Conditions ◽  
Energy Output ◽  
Driving Mechanism ◽  
Physical Explanation ◽  
Pressure Oscillations ◽  
Regenerative Heat ◽  
Steady Heat

Large amplitude acoustical pressure oscillations can be generated in a gas by a steady heat addition. The thermoacoustical oscillation known as the Sondhauss oscillation occurs in a pipe having only one closed end. Experiments were performed to determine thermoacoustic oscillator characteristics for different system geometries and for different operating conditions. Based on these experimental studies, a physical explanation of the mechanism causing Sondhauss thermoacoustical oscillations is presented. The driving mechanism consists of two separate components, that of driving by simple thermal expansion, and that of expansion by the mixing of hot and cold gas in the pipe. The initiation of the oscillations is discussed. Thermoacoustic oscillation phenomena are shown to be analogous to the interaction occurring in a regenerative heat engine, where a steady heat input causes an oscillating mechanical energy output. A comparison of experiment and generalized theory is presented.

Realistic Fatigue Testing and Its Significance in Vehicle Component Design

1968 ◽  
Vol 183 (1) ◽  
pp. 814-829 ◽  
Author(s):  
R. T. Booth
Keyword(s):  
Fatigue Testing ◽  
Fatigue Tests ◽  
Operating Conditions ◽  
Motor Vehicles ◽  
Variable Load ◽  
Research Association ◽  
Constant Amplitude ◽  
Full Size ◽  
Component Design ◽  
Vehicle Component

Current methods of design and development of motor vehicles tend to be limited by lack of knowledge both of the intensity of loading likely to be encountered in service and the endurance of components subjected to these loads. Conventional constant-amplitude fatigue tests are a vast simplification of the random fluctuations of stress usually found under operating conditions and predictions of service endurance based on the results of these tests will be of uncertain value until the relation between conventional tests and reality has been established. At the Motor Industry Research Association investigations are now being made into the effects of variable load patterns on fatigue life, and the characteristics of service stresses are being determined. Because of the cost and complexity of testing full-size components, a ten-station electromagnetic fatigue machine has been developed for work on small laboratory specimens. Much of the basic information is being obtained with these specimens, and it is hoped that confirmatory tests will be carried out later on full-size components. On the ten-station machine fatigue tests have been carried out with service load patterns recorded on magnetic tape, and the results have been compared with constant-amplitude, stationary-random, and block-programme load histories. It is hoped that fatigue-test results obtained with this machine will assist in the development of realistic test procedures, and contribute to the knowledge of cumulative damage, thus shedding light on the problems of vehicle-component design.

scholarly journals Fatigue Testing of Wearable Sensing Technologies: Issues and Opportunities

Materials ◽  
2021 ◽  
Vol 14 (15) ◽  
pp. 4070
Author(s):  
Andrea Karen Persons ◽  
John E. Ball ◽  
Charles Freeman ◽  
David M. Macias ◽  
Chartrisa LaShan Simpson ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Prediction Models ◽  
Fatigue Testing ◽  
Low Cycle Fatigue ◽  
Wearable Sensors ◽  
Fatigue Tests ◽  
Proof Of Concept ◽  
Cycle Fatigue ◽  
Wearable Sensing ◽  
Failure Data

Standards for the fatigue testing of wearable sensing technologies are lacking. The majority of published fatigue tests for wearable sensors are performed on proof-of-concept stretch sensors fabricated from a variety of materials. Due to their flexibility and stretchability, polymers are often used in the fabrication of wearable sensors. Other materials, including textiles, carbon nanotubes, graphene, and conductive metals or inks, may be used in conjunction with polymers to fabricate wearable sensors. Depending on the combination of the materials used, the fatigue behaviors of wearable sensors can vary. Additionally, fatigue testing methodologies for the sensors also vary, with most tests focusing only on the low-cycle fatigue (LCF) regime, and few sensors are cycled until failure or runout are achieved. Fatigue life predictions of wearable sensors are also lacking. These issues make direct comparisons of wearable sensors difficult. To facilitate direct comparisons of wearable sensors and to move proof-of-concept sensors from “bench to bedside,” fatigue testing standards should be established. Further, both high-cycle fatigue (HCF) and failure data are needed to determine the appropriateness in the use, modification, development, and validation of fatigue life prediction models and to further the understanding of how cracks initiate and propagate in wearable sensing technologies.

Experimental Study on Quadruped Wheel Robot for Wheat Precision Seeding

2016 ◽  
Vol 693 ◽  
pp. 1651-1657 ◽  
Author(s):  
Hai Bo Lin ◽  
Chui Jie Yi ◽  
Zun Min Liu
Keyword(s):  
Experimental Study ◽  
Field Test ◽  
Design Method ◽  
Operating Conditions ◽  
High Yield ◽  
Orthogonal Rotation ◽  
Agricultural Machine ◽  
Main Factors ◽  
Multiple Effort

The wheat precision seeding technology provided an advanced agricultural protection for the high yield of wheat. But the lack of an effective agricultural machine made this technology difficult to apply widely. In this paper a quadruped wheel robot to achieve the wheat precision seeding technology was designed. And experimental study was taken under different operating conditions. Because of multiple effort factors, a quadratic orthogonal rotation combination design method was applied in the experiments, and identifying the main factors by analysis. Then the field test was carried out according to the main factors. The experiment results showed that the qualified rates of seeding exceed 93% in different sowing speed. That reached the agronomic requirements of wheat precision seeding.

Optimization Research on Dynamic Balance of Spatial Engine under Limiting Shaking Moment

2009 ◽  
Vol 626-627 ◽  
pp. 693-698
Author(s):  
Yong Yong Zhu ◽  
S.Y. Gao
Keyword(s):  
Mathematical Model ◽  
Objective Function ◽  
Kinetic Analysis ◽  
Optimization Design ◽  
Design Method ◽  
Dynamic Balance ◽  
Optimized Design ◽  
Design Variables ◽  
The Mathematical Model ◽  
Shaking Moment

Dynamic balance of the spatial engine is researched. By considering the special wobble-plate engine as the model of spatial RRSSC linkages, design variables on the engine structure are confirmed based on the configuration characters and kinetic analysis of wobble-plate engine. In order to control the vibration of the engine frame and to decrease noise caused by the spatial engine, objective function is choosed as the dimensionless combinations of the various shaking forces and moments, the restriction condition of which presents limiting the percent of shaking moment. Then the optimization design is investigated by the mathematical model for dynamic balance. By use of the optimization design method to a type of wobble-plate engine, the optimization process as an example is demonstrated, it shows that the optimized design method benefits to control vibration and noise on the engines and improve the performance practically and theoretically.

scholarly journals Experimental Design and Validation of an Accelerated Random Vibration Fatigue Testing Methodology

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Yu Jiang ◽  
Gun Jin Yun ◽  
Li Zhao ◽  
Junyong Tao
Keyword(s):  
Fatigue Life ◽  
Stress Responses ◽  
Life Prediction ◽  
Random Vibration ◽  
Fatigue Testing ◽  
Fatigue Tests ◽  
Fatigue Life Prediction ◽  
Power Spectral ◽  
Vibration Fatigue ◽  
Non Gaussian

Novel accelerated random vibration fatigue test methodology and strategy are proposed, which can generate a design of the experimental test plan significantly reducing the test time and the sample size. Based on theoretical analysis and fatigue damage model, several groups of random vibration fatigue tests were designed and conducted with the aim of investigating effects of both Gaussian and non-Gaussian random excitation on the vibration fatigue. First, stress responses at a weak point of a notched specimen structure were measured under different base random excitations. According to the measured stress responses, the structural fatigue lives corresponding to the different vibrational excitations were predicted by using the WAFO simulation technique. Second, a couple of destructive vibration fatigue tests were carried out to validate the accuracy of the WAFO fatigue life prediction method. After applying the proposed experimental and numerical simulation methods, various factors that affect the vibration fatigue life of structures were systematically studied, including root mean squares of acceleration, power spectral density, power spectral bandwidth, and kurtosis. The feasibility of WAFO for non-Gaussian vibration fatigue life prediction and the use of non-Gaussian vibration excitation for accelerated fatigue testing were experimentally verified.

Gigacycle Fatigue of Welded Joints of Structural Materials (A Review)

2016 ◽  
Vol 17 ◽  
pp. 14-30 ◽  
Author(s):  
Okechukwu P. Nwachukwu ◽  
Alexander V. Gridasov ◽  
Ekaterina A. Gridasova
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Testing Machine ◽  
Structural Materials ◽  
Fatigue Tests ◽  
Material Defects ◽  
Graphite Cast Iron ◽  
Ultrasonic Fatigue ◽  
Materials Used ◽  
Fatigue Failures

This review looks into the state of gigacycle fatigue behavior of some structural materials used in engineering works. Particular attention is given to the use of ultrasonic fatigue testing machine (USF-2000) due to its important role in conducting gigacycle fatigue tests. Gigacycle fatigue behavior of most materials used for very long life engineering applications is reviewed.Gigacycle fatigue behavior of magnesium alloys, aluminum alloys, titanium alloys, spheroid graphite cast iron, steels and nickel alloys are reviewed together with the examination of the most common material defects that initiate gigacycle fatigue failures in these materials. In addition, the stage-by-stage fatigue crack developments in the gigacycle regime are reviewed. This review is concluded by suggesting the directions for future works in gigacycle fatigue.

ADVANCED TYPES OF CHECKERWORK OF REGENERATIVE HEAT EXCHANGERS FOR GLASS FURNACES

2021 ◽  
pp. 3-10
Author(s):  
O. Koshelnik ◽  
S. Hoisan
Keyword(s):  
Phase Transition ◽  
Heat Exchangers ◽  
Heat Storage ◽  
Point Of View ◽  
Operating Conditions ◽  
Flue Gases ◽  
Regenerative Heat ◽  
Exchange Processes ◽  
Glass Furnaces ◽  
Refractory Bricks

One of the ways to increase glass furnaces energy efficiency is to apply heat exchangers for flue gases thermal potential utilization. Flue gases losses is up to 25-40 % of the total amount of heat supplied in the furnace. These losses are influences by such factors as fuel type, furnace and burners design and manufactured product type. Regenerative heat exchangers with various types of heat storage packing is more efficient for high-power furnaces. Such types of regenerator checkerwork as Cowper checkerwork, two types of Siemens checkerwork, Lichte checkerwork and combined checkerwork have already been sufficiently researched, successfully applied and widely used for glass furnaces of various designs. All of its are made of standard refractory bricks. Basket checkerwork and cruciform checkerwork that are made of fused-cast molded refractory materials have been widely used recently as well. Further improvement of regenerative heat exchangers thermal efficiency only by replacing the checkerwork does not seem possible unless their size being increased. But this enlarging is not always realizable during the modernization of existing furnaces. From this point of view heat storage elements with a phase transition, where metal salts and their mixtures are used as a fusible agent look promising for glass furnaces. These elements can accumulate additional amount of heat due to phase transition, which allows to increase significantly heat exchanger thermal rating without its size and operating conditions changing. However, it is necessary to carry out additional studies of this type of checkerwork dealing with analysis of complex unsteady heat exchange processes in regenerators and selection of appropriate materials that satisfy the operating conditions of regenerative heat exchangers so that the checkerwork can be widely used for glass furnaces.

Sign in / Sign up

Export Citation Format

Share Document