臺灣博碩士論文加值系統

本論文中,首先提出一套鑽雙孔應變規量測法,以量測薄板之平面非均勻性雙軸向殘留應力場之殘留主應力值及其方向,同時,量測點附近,殘留主應力方向之應力變化也可依求得之應力梯度預測.將商用三瓣玫瑰花型應變規貼於待測位置後,以一特殊製作之刀具於應變規中心先鑽一小孔,後再予以擴孔,並分別量測兩次鑽孔之釋放應變.薄板上之非均勻性殘留應力即依兩次鑽孔所得之釋放應變求得.文內公式已含入應變規之面積效應,並探討釋放應變係隨應變規長度,寬度,及卜桑比之變化情形.同時,也討論測得平均縱向釋放應變之絕對值隨(規圓半徑/鑽孔半徑)及卜桑比之變化關係.並採用對焊之薄板試件,將文中所提量測方法之實驗結果與 Kabiri 法(採用兩種不同之五瓣玫瑰花型應變規)比較,以驗證其正 確性.經與 Kabiri 法驗證,其相對差異量皆小於 9.4%,故本文所提出之鑽雙孔應變規量測法適於量測薄板之平面非均勻性之雙軸向殘留應力.接著,發展出令一套修正式鑽雙孔應變規量測法以評估振動式應力消除法之效益.試件上任一量測點振動前後之殘留主應力值皆由同一片三瓣玫瑰花型應變規量得之釋放應變依此修正式鑽雙孔應變規量測法求出,經比較振動前後之殘留主應力值即可求取振動式應力消除法之效益.採對焊之薄板試件,將修正式鑽雙孔應變規量測法之量測結果與傳統鑽孔應變規量測法相較,以驗證其正確性.此兩種方法所得結果之相對差異量皆小於 2.9%,故本論文所提之修正式鑽雙孔應變規量測法可有效量測薄板加工件振動前後之殘留應力及評估振動式應力消除處理後之效益.同時,實驗試件經振動式應力消除處理後,各量測點之最大主應力值有效地減少 5.8% 至 27%,而最小主應力值也分別減少 9.6% 至 31%,因而證實了振動式應力消除法之有效性.

In this dissertation, a double-hole-drilling strain gage method is developedto determine the magnitudes and directions of the principal residual stresses,and the stress gradients in the directions of the principal residual stresses of the in-plane non-uniform biaxial residual-stresses field in thin plates.Thevariations of the residual stresses in the directions of the principal residu-al stresses at the region close to the measured point can be predicted simul- taneously with the calculated stress gradients. In this developed method, a commercial three-element strain gage rosette is selected and cemented on the speciified position. Three relieved strains for drilling a monor central hole are measured, and the other three relieved strains are measured after enlar- ging the minor hole with a specially ground tool to prevent eccentricity. The gage area effects are included in the derived equations, and the coefficients of the relieved strain for various gage length, gage width, and Poisson''s ra- tio are discussed. Moreover, the absolute magnitudes of the measured average longitudinal relieved strains for various R/a (gage circle radius/hole radius)and Poisson''s ratio are also explored in the study. Thin butt-welded specimenswere prepared to validate the accuracy of the developed method in comparison with Kabiri''s method by two different gage layouts of rosette. The experimen- tal results show that the relative differences between this method and the Ka-biri''s method are all within 9.4%. Thus, this developed double-hole-drilling strain gage method shows good accuracy in the determination of the in-plane non-uniform residual stresses in thin plates. Then, a modified double-hole- drilling strain gage method is developed to evaluate the effectiveness of the application of vibratory stress relief. The principal residual stresses at anyspecified point before and after the treatment of VSR are measured by this mo-dified method with same cemented commercially available three-element strain gage rosette. By comparing the magnitudes of the measured results before and after VSR, the effectiveness of the treatment of VSR can be determined.Thin butt-welded specimens were prepared to verify the accuracy of this modified double-hole-drilling strain gage method in comparison with conventional hole- drilling strain gage method. The experimental results show the relative dif- ferences between these methods are all within 2.9%. Accordingly,this modified double-hole-drilling strain gage method shows good accuracy in the determina- tion of residual stresses before and after VSR at the same point and the eva- luation of the effectiveness of VSR. Meanwhile, the treatment of VSR carried out in this investigation is demonstrated to be effective, for the maximum principal residual stresses at the measured points are effevtively reduced by about 5.8% to 27% after the application of VSR, and the minimum principal re- sidual stresses at the measured points are effectively reduced by about 9.6% to 31%.

COVER
ABSTRACT
ACKNOWLEDGEMENT
TABLE OF CONTENTS
LIST OF TABLES
List OF FIGURES
NOMENCLATURE
CHAPTER 1 : INTRODUCTION
1.1 Introduction
1.2 Overview of the Residual Stress
1.3 Introduction of the Hole-driling Strain Gage Method
1.4 Review of the Application of Vibratory Stress Relief
1.5 Summary of the Subsequent Chapters
CHAPTER 2 : SOME BACKGROUNDS OF THE RELIEVED STRESSES AND STRAINS
2.1 Introduction
2.2 Influence of Variouw Parameters on the Relieved Stresses
2.3 Characteristics of the Relieved Strains
CHAPTER 3 : THEOREICAL ANALYSIS
3.1 Theory of Measurement of In-plane Non-uniform Residual Stresses
3.2 Theory of Evaluation of the Effectiveness of VSR
CHAPTER 4 : EXPERIMENTAL SETUP AND PROCEDURES AND SPECIMENS PREPARATION
4.1 Equipment and Procedures for the Hole-driling Strain Gage Method
4.2 Vibratory Stress Relief System
4.3 Preparation of the Experimental Specimens
CHAPTER 5 : VERIFICATION PROCEDURES AND EXPERIMENTAL WORKS
5.1 Introduction
5.2 Verification Process of the Double-hole-drilling Strain Gage Method for Measuring the Non-uniform Residual Stresses
5.3 Verification Process of the Modified Double-hole drilling Strain Gage Method for Evaluation the Effctiveness of VSR
CHAPTER 6 : PRESSENTATION OF RESULTS AND DISCUSSION
6.1 Results and Discussion of the Double-hole driling Strain Gage Methid for Measuring the Non-uniform Residual Stresses
6.2 Results and Discussion of the Modified Double-hole-driling Strain Gage Method for Evaluating the Effectiveness of VSR
CHAPTER 7 : CONCLUSIONS AND RECOMMENDATIONS
7.1 Conclusions
7.2 Recommendations
REFERENCES