scholarly journals Fourier Transform (FT) Analysis of the Stress as a Tool to Follow the Fatigue Behavior of Metals

2021 ◽  
Vol 11 (8) ◽  
pp. 3549
Author(s):  
Valerian Hirschberg ◽  
Denis Rodrigue
Keyword(s):  
Fourier Transform ◽  
Time Evolution ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Life Time ◽  
Internal Crack ◽  
Higher Harmonics ◽  
Mechanical Fatigue ◽  
Force Signal ◽  
Crack Friction

This work investigates the possibility of applying Fourier Transform (FT) analysis of the force signal to follow fatigue behavior of metals under oscillatory displacement-controlled tests in uniaxial tension/tension. As a first step, three different materials were selected (cold rolled steel, aluminium and brass). The FT analysis revealed a low level of nonlinearities in the force response, which was possible to measure and quantify as higher harmonics of the imposed sinusoidal deformation. Due to geometric reasons, the odd higher harmonics represent the symmetric nonlinearity while even ones are related to asymmetry, so both odd and even harmonics need to be analyzed separately. The time evolution of the higher harmonics showed that the odd higher harmonics continuously increase during the test. Criteria to better predict the mechanical fatigue and failure (life time) are then proposed based on the integral and derivative based on the time evolution the odd higher harmonics. In contrast, for tests in the high cycle fatigue regime, the even higher harmonics are mainly noise at the beginning of the test (undamaged state), but start to rise after the occurrence of a crack due to internal crack friction. Based on the analysis performed, FT analysis of the force during mechanical fatigue testing of metals is a sensitive tool used to predict failure and to improve our understanding of the dynamics involved in mechanical fatigue.

Defects and Failure Modes in PZT Films for a MEMS Microengine

2000 ◽  
Vol 657 ◽  
Author(s):  
D.F. Bahr ◽  
B.T. Crozier ◽  
C.D. Richards ◽  
R.F. Richards
Keyword(s):  
Fatigue Damage ◽  
Thermal Stresses ◽  
Failure Modes ◽  
Fatigue Testing ◽  
Failure Strain ◽  
Fatigue Behavior ◽  
Mechanical Strain ◽  
Solution Deposition ◽  
Mechanical Fatigue ◽  
Pzt Films

ABSTRACTPiezoelectric films for a MEMS microengine have been deposited using solution deposition routines onto platinized silicon wafers. These films are used as membranes above a bulk micromachined cavity. A dynamic bulge tester and interferometer were used to characterize the deformation of the films when pressurized. The mechanical strain at failure, as well as the fatigue behavior, have been characterized. Membranes between 300 and 500 nm thick have been shown to sustain mechanical fatigue damage over approximately 10 million cycles at strains of 30% of the monotonic failure strain. Defects in the films due to growth and thermal stresses during processing, and their role in membrane failure, are identified. Crack growth is demonstrated in these films by compliance measurements during fatigue testing, and interfacial failure is identified between the PZT and Pt layers.

Analysis of Mechanical Fatigue Behavior for MEMS Structures

2014 ◽  
Vol 511-512 ◽  
pp. 565-568
Author(s):  
Qin Wen Huang ◽  
Xiang Guang Li ◽  
Yun Hui Wang
Keyword(s):  
Rf Mems ◽  
Fatigue Testing ◽  
Electrostatic Force ◽  
Fatigue Behavior ◽  
Excitation Frequency ◽  
Material Degradation ◽  
Mems Switch ◽  
Mechanical Fatigue ◽  
Number Of Cycles ◽  
Alternating Voltage

Fatigue of MEMS structures may occur after cyclic vibration loading, which can lead to the material degradation. A test bench was built for mechanical fatigue testing, especially for the structures that actuated by electrostatic force. A RF MEMS switch which was made of gold was tested; the material mechanical characteristic was monitored during the tests by means of the value of pull-in voltage, which is related to the change of the Youngs modulus. The fatigue stress was produced by an alternating voltage, and the amplitude of which is from 15V to 65V. The excitation frequency and the actuation time were used as a counter for the number of cycles. The results show that there is no detectable mechanical fatigue after actuation up to one billion cycles.

Fatigue of Unidirectional Cord-Rubber Composites

1999 ◽  
Vol 27 (1) ◽  
pp. 48-57 ◽  
Author(s):  
Y. Liu ◽  
Z. Wan ◽  
Z. Tian ◽  
X. Du ◽  
J. Jiang ◽  
...  
Keyword(s):  
Damage Accumulation ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Constant Load ◽  
Testing System ◽  
Rubber Composites ◽  
Cycle Frequency ◽  
Periodic Loading ◽  
Fatigue Damage Accumulation ◽  
Rubber Composite

Abstract A fatigue testing system is established with which the real-time recording of stress, strain, temperature, and hysteresis loss of rubbers or cord-rubber composite specimens subjected to periodic loading or extension can be successfully carried out. Several problems are connected with the experimental study of the fatigue of rubber composites. In constant extension cycling, the specimen becomes relaxed because of the viscoelasticity of rubber composites, and the imposed tension-tension deformation becomes complex. In this method, the specimen is unlikely to fail unless the imposed extensions are very large. Constant load cycling can avoid the shortcomings of constant extension cycling. The specially designed clamps ensure that the specimen does not slip when the load retains a constant value. The Deformation and fatigue damage accumulation processes of rubber composites under periodic loading are also examined. Obviously, the effect of cycle frequency on the fatigue life of rubber composites can not be ignored because of the viscoelasticity of constituent materials. The increase of specimen surface temperature is relatively small in the case of 1 Hz, but the temperature can easily reach 100°C at the 8 Hz frequency. A method for evaluating the fatigue behavior of tires is proposed.

Low Cycle Tension-Tension Fatigue Properties of 316L Stainless Steel Thin Sheets

2011 ◽  
Vol 138-139 ◽  
pp. 832-835
Author(s):  
Yong Jie Liu ◽  
Qing Yuan Wang ◽  
Ren Hui Tian ◽  
Xiao Zhao
Keyword(s):  
Stainless Steel ◽  
Room Temperature ◽  
316L Stainless Steel ◽  
Fatigue Testing ◽  
Fatigue Properties ◽  
Loading Frequency ◽  
Thin Sheets ◽  
Effect Factor ◽  
Mechanical Fatigue ◽  
Tensile Fatigue

In this paper, tensile fatigue properties of 316L stainless steel thin sheets with a thickness of 0.1 mm are studied. The tests are implemented by using micro mechanical fatigue testing sysytem (MMT-250N) at room temperature under tension-tension cyclic loading. The S-N curve of the thin sheets descends continuously at low cycle region. Cyclic σ-N curve and ε-N curve are obtained according to the classical macroscopical fatigue theory. The results agree well with the experimental fatigue data, showing that the traditional fatigue research methods are also suitable for description of MEMS fatigue in a certain extent. The effect factor of frequency was considered in this study and the results show that the fatiuge life and the fatigue strength are increased as loading frequency increasing.

Partial Devitrification of Sintered Silicon Nitride During Static Fatigue Testing

1992 ◽  
Vol 287 ◽  
Author(s):  
W. Braue ◽  
G. D. Quinn
Keyword(s):  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Slow Crack Growth ◽  
Stress Rupture ◽  
Secondary Phase ◽  
Boundary Phase ◽  
Static Fatigue ◽  
Phase Assemblage ◽  
Transmission Electron ◽  
Stress States

ABSTRACTThe static fatigue behavior of sintered Y2O3/A12O3-fluxed Si3N4 in air is controlled by slow crack growth or creep fracture. Partial devitrification of the amorphous grain boundary phase at 1000°C and 1100°C improves the static fatigue resistance with specimens surviving up to 1500 hrs. during stress rupture experiments. In this study the early stages of partial devitrification during static fatigue testing at 1000°C are investigated by conventional and analytical transmission electron microscopy with emphasis on nucleation and growth of δ-Y2Si2O7 and X1-Y2SiO5 and possible constraints from different stress states. The results show that the stress state does not affect the nature of the secondary phase assemblage. However, the amount of crystallization is higher within the tensile region of the flexural specimens than in areas which experienced compressive stresses.

Thermo-mechanical fatigue testing of superalloys using miniature specimens

2008 ◽  
Vol 30 (2) ◽  
pp. 397-403 ◽  
Author(s):  
S PAHLAVANYALI ◽  
A RAYMENT ◽  
B ROEBUCK ◽  
G DREW ◽  
C RAE
Keyword(s):  
Fatigue Testing ◽  
Mechanical Fatigue ◽  
Miniature Specimens

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.

Sign in / Sign up

Export Citation Format

Share Document