REPAIRS MECHANICS

Repairs Mechanics



Executive Summary

This paper discusses a special repair case and new results by using two repair criteria: the slope continuity criterion and fracture mechanics criterion proposed by Wang et al. and Liu , respectively. Crack contact analyses and fracture mechanics in the crack tip field are considered in the finite element analyses. The results from both criteria will be compared and discussed in the report.

Table of Content

EXECUTIVE SUMMARYII

REPAIRS MECHANICS1

Introduction1

Hypothesis2

Data Set3

Population and Sample3

Analysis of given data set4

Cross tabs12

Regression14

Correlation16

ANOVA18

Hypotheses Testing18

Hypotheses Testing19

Discussion20

Conclusion22

REFERENCES23

BIBLIOGRAPHY24

Table 0125

Table 0226

Table 0326

Table 0427

Table 0527

Graph 0128

Graph 0229

Graph 0330

Graph 0430

Graph 0531

Table 0632

Graph 0633

Table 0733

Table 0834

Table 0934

Table 1035

Table 1136

Table 1236

Repairs Mechanics

Introduction

Bonded repair technique uses metallic or composite patches bonded on a crack to repair damaged structures . By the change of loading path, the crack opening displacement can be reduced and fatigue crack propagation is retarded. In other words, the stress intensity factor at the crack tip is reduced so that the fatigue life of cracked component is increased.

Data Collection Method

In the analysis data collection method is the open ended questionnaire that had been distributed on internet and later it will be analyse through SPSS and Spread sheets.

Discussion

In contrast to traditional bonded repair technique, piezoelectric actuators can actively reduce strain concentrations from transverse cracks, near holes and notches, and other forms of damage or engineered strain concentrations . This idea can be called as “active repair” in comparison with traditional bonded repair or passive repair. Recently, Wang et al. used analytical Euler beam model to study the active repair for a cracked beam by a piezoelectric patch (actuator) , and . The repair criterion for the cracked beam model in is the cancellation of the slope discontinuity of the deflection caused by the existence of an edge crack. Their results from analytical solutions provided valuable design guides for the piezoelectric actuator in active repair.

However, the theories of fracture mechanics and crack tip field were not considered in , and . More realistic finite element analyses of active repair were studied by Liu to estimate complicated crack tip situations and repair performances . The linear elastic fracture mechanics and strain energy density theory were adopted in . Some results in are quite different from those in due to the crack contact conditions when the cracked structure is repaired by a piezoelectric actuator.

Liu used two-dimensional plane strain finite element analyses to study the active repair for cracked structure by using the multi-layered piezoelectric actuator. The reductions of stress intensity factors and strain energy density factors at the crack tip were obtained. Also, the repair voltages of the piezoelectric actuator for various conditions were obtained for estimating the repair performance. From the results of numerical fracture mechanics, it shows the crack contact conditions must be considered in the analysis. The better design choices for the multi-layered piezoelectric actuator found in are as follows: increasing the layer number, increasing the length, and reducing the thickness. However, too long length has no advantage for the active ...