scholarly journals An Educational Platform in Structural Mechanics

2013 ◽  
Vol 9 (S8) ◽  
pp. 10 ◽  
Author(s):  
Tiago A. N. Silva ◽  
Maria A. R. Loja
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Stress Level ◽  
Optimization Technique ◽  
Structural Mechanics ◽  
Functionally Graded ◽  
Thermal Residual Stress ◽  
Design Parameters ◽  
Mechanical Resistance ◽  
Thermal Residual Stresses

Thermal residual stresses often arise due to a manufacturing process, involving localised thermal induction, or to the existence of structural components with different thermal expansion coefficients. The existence of thermal residual stresses within a structural member is usually undesired, as it decreases the mechanical resistance of structures. Hence, it is desirable to obtain both a minimum level of residual stresses and smoother stresses transitions in the materials interfaces. Regarding the mitigation of thermal residual stress concentration, the use of materials which properties can vary along the component directions has great interest. This work addresses the use of dual-phase functionally graded materials, which microstructure varies gradually from a material to another according to a given gradation function. On the order hand, it is also addressed the use of a population based optimization algorithm in order to attain the referred minimum stress level. Summarizing, the current work presents an educational platform directed to structural mechanics students, which aims to give the tools to understand both the influence of design parameters in the thermal residual stress level and distribution along the material and the advantages of using a structural optimization technique in order to minimize the drawback thermal residual stresses effects.

Effect of Thermal Residual Stresses on Polymer/Metal Interfacial Adhesion

1999 ◽  
Author(s):  
Qizhou Yao ◽  
Jianmin Qu
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Coefficient Of Thermal Expansion ◽  
Interfacial Crack ◽  
Thermal Residual Stress ◽  
Element Analysis ◽  
Thermal Residual Stresses ◽  
Interfacial Cracks ◽  
Cte Mismatch ◽  
Elastic Mismatch

Abstract In this study, the apparent fracture toughness of the interfaces of several epoxy-based polymeric adhesives and metal (aluminum) substrate is experimentally measured. Double layer specimens with initial interfacial cracks are made for four-point bending tests. Thermal residual stresses exist on the interface due to the coefficient of thermal expansion (CTE) mismatch between the underfill and aluminum. Silica fillers are used to modify the CTE of the epoxy-based adhesives so that various levels of interface thermal residual stresses are achieved. Finite element analysis is also performed to quantify the effects of CTE mismatch as well as the elastic mismatch across the interface. It is found that the apparent interfacial toughness is significantly affected by the thermal residual stress, while the effect of elastic mismatch is negligible. In general thermal residual stress undermines the resistance to an interfacial crack. In some cases the residual stress is sufficient to result in adhesive and/or cohesive failure.

Effect of Thermal Residual Stress on the Mechanical Properties of NiAl-Based Composites

1998 ◽  
Vol 552 ◽  
Author(s):  
Hahn Choo ◽  
Mark Bourke ◽  
Philip Nash
Keyword(s):  
Residual Stress ◽  
Yield Strength ◽  
Residual Stresses ◽  
Room Temperature ◽  
Hybrid Composites ◽  
Thermal Residual Stress ◽  
Volume Percent ◽  
Linear Superposition ◽  
Thermal Residual Stresses ◽  
Good Agreement

ABSTRACTNiAl-based hybrid composites containing 5, 15 and 30 volume percent of A12O3 fibers in addition to AIN dispersion particles were fabricated via a powder metallurgy route. The strengthening mechanisms associated with the short A12O3 fiber in NiAl-(A1N)dispersion,-(A12O3)fiber, composite were studied with an emphasis on the effect of thermal residual stress on the compressive strength at room temperature and 1300K. At 300K, the yield strength of the composites was predicted using a linear superposition of the monolithic yield strength, direct fiber strengthening and tensile matrix residual stresses. The prediction shows good agreement with the measured data. The majority of the room temperature strengthening is attributable to the residual stress. At 1300K, the strengthening was achieved only by the load sharing of the fibers and there is no direct influence from the process-induced thermal residual stresses since they were completely relaxed at this temperature.

Damage Evolution of the Interphase on C/SiC Composites with CZM Method

2012 ◽  
Vol 166-169 ◽  
pp. 2847-2850
Author(s):  
Yan Jun Chang ◽  
Zhuo Li ◽  
Ke Shi Zhang
Keyword(s):  
Residual Stress ◽  
Damage Evolution ◽  
Fem Analysis ◽  
Matrix Crack ◽  
Thermal Residual Stress ◽  
Analysis Model ◽  
Initial Matrix ◽  
Thermal Residual Stresses ◽  
Initiation And Propagation ◽  
Sic Composites

Considering thermal residual stress and initial matrix crack, the cylinder FEM analysis model for C/SiC tow was established. The cohesive element and damage criterions were introduced to simulation the initiation and propagation of interphase crack processes of C/SiC composites. The thermal residual stresses release with the initial matrix crack and the cracking on interphase. The interphase crack length was dominated by the performance of interphase. Analysis demonstrated that the CZM model can simulate well the thermal residual stress and the delamination of the interphase.

Optimization of the sintering temperature, cooling time and grain size parameters to reduce residual stresses of copper-aluminum functionally graded material using response surface methodology

2021 ◽  
pp. 030932472110687
Author(s):  
Ahmad Gheysarian ◽  
Mohammad Honarpisheh
Keyword(s):  
Residual Stress ◽  
Grain Size ◽  
Residual Stresses ◽  
Functionally Graded Materials ◽  
Sintering Temperature ◽  
Flexible Structures ◽  
Functionally Graded ◽  
Cooling Time ◽  
Property A ◽  
Graded Materials

One of the urgent needs for the medical, aerospace and military industries is to combine materials with heat-resistant as well as flexible structures. To create such a property, a ceramic must be placed next to metal. FGM materials have such a property in terms of thickness. Functionally graded materials (FGM) are examples of materials with different properties in the thickness direction. In the functionally graded materials, different properties can be created, by changing the percent weight of materials in each layer. It is very important to study the number of residual stresses in these materials due to the fact that several materials with different properties are combined with each other. The purpose of this study is to investigate the effect of production parameters on the number of residual stresses in the aluminum-copper FGM part and also to optimize the production process of these materials. The results indicate that the number of residual stresses decreases with increasing the sintering temperature, cooling time of the sample as well as uniformity along the thickness. In the experiments, the maximum residual stress was 171 MPa, which was obtained for a grain size of 100 microns, sintering temperature of 600°C and cooling time of 24 h and the minimum value of pressure residual stress was 120 MPa, which was obtained for grain size of 20 microns, sintering temperature of 900°C and cooling time of 48 h. Also, finite element modeling of the process was performed and shown a good agreement with experimental results.

The Research on Thermal Residual Stress of SiCp/Al Composites

2014 ◽  
Vol 852 ◽  
pp. 127-131
Author(s):  
Jin Zou ◽  
Jian Yun Zhang ◽  
De Ping Lu ◽  
Qi Jie Zhai
Keyword(s):  
Residual Stress ◽  
Thermal Residual Stress ◽  
X Ray Diffraction ◽  
Cooling Process ◽  
Time Curve ◽  
Cooling Rates ◽  
Thermal Residual Stresses ◽  
Dimension Stability ◽  
The Difference ◽  
Particle Shapes

SiCp/Al composites would produce a large thermal residual stresses field during cooling process. The thermal residual stress has a greater impact to the composites dimension stability and the accuracy of application. In this paper, the thermal residual stress in SiCp/A356 composites was measured by X-ray diffraction and simulated by finite element method (FEM), the influence of particle shapes and cooling rates are considered, the stress field contour nephogram and stress-time curve during cooling was simulated. The studies present residual stress formed during cooling process because of the difference of thermal expansion coefficient (CTE) between SiC particle and aluminum alloy, the maximum stress distributes near the interface of matrix/SiCp mainly. The stress-time curves are inconsistent under different cooling rates, the higher cooling rate, the more dramatic variety in stress.

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