Smart Stress-Memory Patch for Fatigue Damage of Structure

Abstract

A new fatigue sensor called ''smart stress-memory patch'', which can estimate the cyclic number, the stress amplitude and the maximum stress from the measurement of crack length and acoustic emission (AE), is proposed to evaluate the fatigue damage of such infrastructure as bridges and ships. The fatigue crack growth behavior of thin electrodeposited (ED) Cu specimen for this sensor is investigated. The modified stress intensity factor is proposed to introduce the master curve of fatigue crack growth, because the fatigue crack growth behavior of this patch is affected by the maximum stress and stress ratio. AE signals are also measured to estimate the AE onset stress and examine Kaiser effect of ED Cu specimen. It is expected that the cyclic number, the stress amplitude and the maximum stress in fatigue loading can be estimated by this patch.

Scattering in Fatigue Crack Growth of Thin Pure Copper Sheet for Smart Stress Memory Patch

“…In the previous study, 3) the fatigue crack growth of thin Cu specimen was investigated. Although the fatigue crack growth behavior was affected by the maximum stress and stress ratio, the logarithmic relationship between the fatigue crack growth rate and the stress intensity factor range was almost linear.…”

Evaluation of Fatigue Properties of Steel Bar by Smart Stress-memory Patch

“…(1) and (2). The relationship between normalized crack length and calculated dimensionless stress intensity factor under each stress is shown in Fig.…”

“…A sensor called "smart stress-memory patch" that can measure the maximum stress, the stress amplitude and the cyclic number simultaneously was proposed in the previous paper. 1,2) Using this patch the maximum stress can be obtained by Kaiser effect of Acoustic Emission (AE) method, and the cyclic number and the stress amplitude can be estimated by crack length of the sensor. Since this patch needs neither the power supply nor wiring, it is possible to measure the fatigue loading for a long period.…”

Strain-Controlled Fatigue Behavior in Thin Pure Copper Sheet for Smart Stress-Memory Patch

“…Stress amplitude can be estimated from crack length detected from two sensors with different characteristics, as the details were described in the previous paper. 7) Therefore, it was shown that fatigue cycles on structures can be estimated using smart patch.…”

“…12) The fatigue crack growth behavior in the sensor under stress-controlled fatigue test has been investigated to estimate stress amplitude and fatigue cycles. 7,8) However, when the patch is attached to structure, the sensor is subjected to straincontrolled loading under the change in strain of the structure. Therefore, it is necessary to evaluate fatigue behavior in the sensor under strain-controlled conditions for application of smart patch to structure.…”