Fatigue Strength of Metal / FRP Adhesive Joints Under Low Temperature

1995 ◽  
Author(s):  
Toshio Hattori ◽  
Masaaki Iwasa
Keyword(s):  
Fatigue Strength ◽  
Low Temperature ◽  
Residual Stresses ◽  
Adhesive Joint ◽  
Evaluation Method ◽  
Stress Singularity ◽  
Adhesive Joints ◽  
Strength Evaluation ◽  
Thermal Residual Stresses ◽  
Super Conducting

Abstract Fiber reinforced plastics (FRP) have the excellent thermal isolation characteristics, and are used for for cryogenic structures such as super conducting magnets. Generally these FRP materials are connected with metal structures using adhesive joint, as these FRP materials loose strength by the existence of bolt holes. In this metal/FRP adhesive joints high thermal residual stresses occur under cryogenic temperatures as the thermal expansion coefficients of both materials differ large. So, improvement of strength evaluation method of these bi-material adhesive joints under low temperature become indispensable to develop high-reliability super conducting magnet systems such as form Magnetic Levitation Liner Motor Car. In this paper we present a new fatigue strength evaluation method under high thermal residual stresses using following two stress singularity parameters K and λ at bonding edges. τ ( r ) = K / rλ Heat τ(r) is stress (MPa), r is the distance (mm) from the singular point (bonding edge), K is the intensity of stress singularity and λ is the order of stress singularity. And this evaluation method is applied to Stainless-steel/Al2O3 FRP adhesive joint models.

Evaluation Method for Fatigue Strength of FRP/Metal Adhesive Joints Considering Mean Stress

2003 ◽  
Vol 125 (4) ◽  
pp. 402-405 ◽  
Author(s):  
Masaaki Iwasa ◽  
Toshio Hattori
Keyword(s):  
Fatigue Strength ◽  
Low Temperature ◽  
Evaluation Method ◽  
Stress Singularity ◽  
Propagation Rate ◽  
Lap Joints ◽  
Adhesive Joints ◽  
Mean Stress ◽  
Lap Joint ◽  
The Relationship

The fatigue strength of two types of FRP/metal adhesive joints at low temperature, a double lap joint and an embedded joint, was evaluated analytically and experimentally. First, the stress singularity parameters of the delamination edges under mechanical and thermal loadings were analyzed by FEM for various delamination lengths. The delamination propagation rate of the double lap joint under mechanical cyclic loadings at room temperature was measured. Using the relationship between the measured propagation rates and the analyzed ranges of stress singularity intensity, we estimated the fatigue strength of the embedded joint, which coincided well with the measured one. Second, we developed an evaluation method that separates the effects of temperature on fatigue strength into two effects: thermal residual stress and low temperature. Third, the fatigue strengths of the double lap joints were measured for various mean stresses. Fatigue limit of adhesive joints was experimentally measured and compared with analytical intensity of stress singularity. A method for evaluating the fatigue strength of adhesive joints by taking mean stress into account was developed.

scholarly journals Evaluation Method for Residual Stresses Induced by Surface Treatments of Crankshafts and Effect of These Stresses on Fatigue Strength

2020 ◽  
Vol 55 (1) ◽  
pp. 3-10
Author(s):  
Mariko Matsuda ◽  
Hitomi Adachi ◽  
Tomonori Ikegami ◽  
Tatsuhiko Kabutomori ◽  
Toshihiko Sasaki
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Evaluation Method ◽  
Surface Treatments

Fatigue strength evaluation of welded joints containing high tensile residual stresses

1986 ◽  
Vol 8 (3) ◽  
pp. 147-150 ◽  
Author(s):  
A OHTA ◽  
Y MAEDA ◽  
T MAWARI ◽  
S NISHIJIMA ◽  
H NAKAMURA
Keyword(s):  
Fatigue Strength ◽  
Residual Stresses ◽  
Welded Joints ◽  
Strength Evaluation

Improved Mathematical Models of Thermal Residual Stresses in Functionally Graded Adhesively Bonded Joints: A Critical Review

2019 ◽  
Vol 7 (4) ◽  
pp. 367-416 ◽  
Author(s):  
M. Kemal Apalak ◽  
M. Didem Demirbas
Keyword(s):  
Residual Stresses ◽  
Mathematical Models ◽  
Adhesive Layer ◽  
Adhesive Joints ◽  
Functionally Graded ◽  
Stress And Strain ◽  
Stress Distributions ◽  
Adhesively Bonded ◽  
Thermal Residual Stresses ◽  
Derivatives Of

Functionally graded material (FGM) concept has been applied successfully in order to improve/design heat transfer, electric and electronic conductivity, static and dynamic strengths of adhesive joints by reliving stress distributions in both adhesive and adherend materials. This new approach relies on tailoring material composition of adhesive and adherends along one or more coordinate directions. Thermal residual stresses in adhesive joints are a vital issue in terms of the joint strength. FGM concept also allows to relieve/control thermal residual stresses encountered in adhesive joints due to mismatches between coefficients of thermal expansion of adhesive and adherend materials. Mathematical models and solutions on the thermal residual stress analysis have been continuously improved. This paper reviews the current status of mathematical models, and offers an improved mathematical model and numerical solution method by considering two-dimensional thermal stress and deformation states of adhesively bonded bi-directional functionally graded clamped plates subjected to an in-plane heat flux along one of the ceramic edges. This mathematical model assumes the material properties of the functionally graded plates to vary with a power law along two in-plane directions and not through the plate thickness direction, in particular, considers the spatial derivatives of thermal and mechanical properties of the material, and enables the investigation of the effects of the bi-directional composition variations and spatial derivative terms on the displacement, strain and stress distributions. The heat conduction and Navier equations describing the twodimensional thermo-elastic problem are discretized using finite-difference method, and the set of linear equations are solved using the pseudo singular value method. The functionally graded plates relieve both stress and strain distributions and levels in the adhesive layer and in the plates even though the adhesive layer is still ungraded. The spatial derivatives of mechanical and thermal properties of the local material become more effective on the strain and stress distributions of the plates and adhesive layer. The model, disregarding these derivative terms, exhibits sensitivity to small changes in the compositional gradients (n, m) by adjusting the variations of ceramic volume fraction along the x - and y-directions, respectively, and instability in the calculation of stress and strain distributions and levels. However, the improved model with material derivatives, which considers the effects of these derivative terms, predicts stress and strain distributions and levels complying with changes in the compositional gradient exponents.

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