Investigation on Inelastic Strain Energy of IGBT Solder Layers During Aging by the Clech Algorithm

2020 ◽  
Author(s):  
Xinlong Wu ◽  
Xin Yang ◽  
Xingyu Dai ◽  
Jun Wang
Keyword(s):  
Strain Energy ◽  
Inelastic Strain

Analysis of Energy Balance When Using Cohesive Zone Models to Simulate Fracture Processes

2002 ◽  
Vol 124 (4) ◽  
pp. 440-450 ◽  
Author(s):  
C. Shet ◽  
N. Chandra
Keyword(s):  
Cohesive Energy ◽  
Cohesive Zone ◽  
Strain Energy ◽  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Elastic Strain Energy ◽  
Inelastic Strain ◽  
External Work ◽  
Cohesive Zone Models

Cohesive Zone Models (CZMs) are being increasingly used to simulate fracture and fragmentation processes in metallic, polymeric, and ceramic materials and their composites. Instead of an infinitely sharp crack envisaged in fracture mechanics, CZM presupposes the presence of a fracture process zone where the energy is transferred from external work both in the forward and the wake regions of the propagating crack. In this paper, we examine how the external work flows as recoverable elastic strain energy, inelastic strain energy, and cohesive energy, the latter encompassing the work of fracture and other energy consuming mechanisms within the fracture process zone. It is clearly shown that the plastic energy in the material surrounding the crack is not accounted in the cohesive energy. Thus cohesive zone energy encompasses all the inelastic energy e.g., energy required for grainbridging, cavitation, internal sliding, surface energy but excludes any form of inelastic strain energy in the bounding material.

Thermal Fatigue Prediction for Leadless Solder Joint of TFBGA

2006 ◽  
Author(s):  
Chia-Lung Chang ◽  
Tzu-Jen Lin ◽  
Chih-Hao Lai
Keyword(s):  
Energy Density ◽  
Solder Joint ◽  
Creep Strain ◽  
Thermal Fatigue ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Creep Property ◽  
Inelastic Strain ◽  
Temperature Cycling ◽  
Element Analysis

Nonlinear finite element analysis was performed to predict the thermal fatigue for leadless solder joint of TFBGA Package under accelerated TCT (Temperature Cycling Test). The solder joint was subjected to the inelastic strain that was generated during TCT due to the thermal expansion mismatch between the package and PCB. The solder was modeled with elastic-plastic-creep property to simulate the inelastic deformation under TCT. The creep strain rate of solder was described by double power law. The furthest solder away from the package center induced the highest strain during TCT was considered as the critical solder ball to be most likely damaged. The effects of solder meshing on the damage parameters of inelastic strain range, accumulated creep strain and creep strain energy density were compared to assure the accuracy of the simulation. The life prediction equation based on the accumulated creep strain and creep strain energy density proposed by Syed was used to predict the thermal fatigue life in this study. The agreement between the prediction life and experimental mean life is within 25 per cent. The effect of die thickness and material properties of substrate on the life of solder was also discussed.

scholarly journals Insight into the microphysics of antigorite deformation from spherical nanoindentation

2020 ◽  
Vol 378 (2165) ◽  
pp. 20190197 ◽  
Author(s):  
Lars N. Hansen ◽  
Emmanuel C. David ◽  
Nicolas Brantut ◽  
David Wallis
Keyword(s):  
Mechanical Behaviour ◽  
Basal Plane ◽  
Strain Energy ◽  
High Pressures ◽  
Inelastic Strain ◽  
Indentation Load ◽  
Strain Recovery ◽  
Shear Cracks ◽  
Elastic Loading ◽  
Lattice Misorientation

The mechanical behaviour of antigorite strongly influences the strength and deformation of the subduction interface. Although there is microstructural evidence elucidating the nature of brittle deformation at low pressures, there is often conflicting evidence regarding the potential for plastic deformation in the ductile regime at higher pressures. Here, we present a series of spherical nanoindentation experiments on aggregates of natural antigorite. These experiments effectively investigate the single-crystal mechanical behaviour because the volume of deformed material is significantly smaller than the grain size. Individual indents reveal elastic loading followed by yield and strain hardening. The magnitude of the yield stress is a function of crystal orientation, with lower values associated with indents parallel to the basal plane. Unloading paths reveal more strain recovery than expected for purely elastic unloading. The magnitude of inelastic strain recovery is highest for indents parallel to the basal plane. We also imposed indents with cyclical loading paths, and observed strain energy dissipation during unloading–loading cycles conducted up to a fixed maximum indentation load and depth. The magnitude of this dissipated strain energy was highest for indents parallel to the basal plane. Subsequent scanning electron microscopy revealed surface impressions accommodated by shear cracks and a general lack of dislocation-induced lattice misorientation. Based on these observations, we suggest that antigorite deformation at high pressures is dominated by sliding on shear cracks. We develop a microphysical model that is able to quantitatively explain Young’s modulus and dissipated strain energy data during cyclic loading experiments, based on either frictional or cohesive sliding of an array of cracks contained in the basal plane. This article is part of a discussion meeting issue ‘Serpentinite in the earth system’

Fatigue Life Law Based on Inelastic Strain Energy Density of Solder Alloys and its Simple Prediction Method

2020 ◽  
Author(s):  
Tomoya Fumikura ◽  
Mitsuaki Kato ◽  
Takahiro Omori
Keyword(s):  
Fatigue Life ◽  
Energy Density ◽  
Fatigue Test ◽  
Strain Energy Density ◽  
Strain Energy ◽  
Prediction Method ◽  
Strain Range ◽  
Inelastic Strain ◽  
Stress Strain ◽  
Wide Range

Abstract In recent years, a fatigue life law based on inelastic strain energy density as proposed by Morrow has been applied to solder materials. In this study, the effectiveness of the fatigue life law based on inelastic strain energy density was compared with the conventional law based on inelastic strain range. First, the fatigue properties of Sn-Ag-Cu solder alloy were investigated by a torsional fatigue test with strain control. It was found that the stress–strain hysteresis loop arising from inelastic deformation occurred even under a low strain load with a fatigue life of about 1 million cycles. Therefore, as an extension of the low-cycle fatigue test, evaluation was performed using inelastic strain range and inelastic strain energy density. Experimental results show that when fatigue life was evaluated using inelastic strain energy density, a single power law was found over a wide range from the low-cycle region to the high-cycle region, and the validity of the fatigue life law based on inelastic strain energy density was confirmed. Next, a simple prediction method for the fatigue life law based on inelastic strain energy density was examined, taking the physical background into account. Two material constants of the fatigue life law based on the inelastic strain energy density were estimated from the stress–strain curve for a monotonic load and shown to be close to the actual fatigue test results.

INELASTIC STRAIN CONCENTRATION IN DIRECTIONALLY SOLIDIFIED MATERIALS

1995 ◽  
Vol 19 (3) ◽  
pp. 331-346 ◽  
Author(s):  
R.S. Alwar ◽  
Suresh Babu
Keyword(s):  
Strain Energy Density ◽  
Strain Energy ◽  
Life Prediction ◽  
Low Cycle Fatigue ◽  
Engine Performance ◽  
Inelastic Strain ◽  
Equivalent Strain ◽  
Cycle Fatigue ◽  
Directionally Solidified ◽  
Neuber's Rule

The application of Directionally Solidified (DS) materials in the construction of hot section parts (blades, vanes) of a gas turbine results in improvement in the engine performance and durability. Inelastic strain, an important parameter in low cycle fatigue (LCF) life prediction methodology, may be evaluated using simplified methods like Neuber’s rule and Equivalent Strain Energy Density Hypothesis. The objectives of the present investigation are to examine the validity of these methods in case of DS materials and to demonstrate using numerical methods that the low cycle fatigue life of DS materials is superior to isotropic materials.

Fatigue Life Predictions for Thermally Loaded Solder Joints Using a Volume-Weighted Averaging Technique

1997 ◽  
Vol 119 (4) ◽  
pp. 228-235 ◽  
Author(s):  
H. U. Akay ◽  
N. H. Paydar ◽  
A. Bilgic
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Strain Energy ◽  
Solder Joints ◽  
Strain Range ◽  
Inelastic Strain ◽  
Weighted Averaging ◽  
Stress And Strain ◽  
Element Analysis ◽  
Averaging Technique

Fatigue lives of thermally loaded solder joints are predicted using the finite element method. An appropriate constitutive relation to model the time-dependent inelastic deformation of the near-eutectic solder is implemented into a commercial finite element code, and the stress-strain responses of different electronic assemblies under the applied temperature cycles are calculated. The finite element analysis results are coupled with a newly developed approach for fatigue life predictions by using a volume-weighted averaging technique instead of an approach based on the maximum stress and strain locations in the solder joint. Volume-weighted average stress and strain results of three electronic assemblies are related to the corresponding experimental fatigue data through least-squares curve-fitting analyses for determination of the empirical coefficients of two fatigue life prediction criteria. The coefficients thus determined predict the mean cycles-to-failure value of the solder joints. Among the two prediction criteria, the strain range criterion uses the inelastic shear strain range and the total strain energy criterion uses the total inelastic strain energy calculated over a stabilized loading cycle. The obtained coefficients of the two fatigue criteria are applied to the finite element analysis results of two additional cases obtained from the literature. Good predictions are achieved using the total strain energy criterion, however, the strain range criterion underestimated the fatigue life. It is concluded that the strain information alone is not sufficient to model the fatigue behavior but a combination of stress and strain information is required, as in the case of total inelastic strain energy. The superiority of the volume-weighted averaging technique over the maximum stress and strain location approach is discussed.

Criteria for Fatigue Failure of Materials: Application in Fatigue Assessment of Structures

2018 ◽  
Vol 26 ◽  
pp. 1-8
Author(s):  
Sergei Petinov ◽  
Ruslan Guchinsky
Keyword(s):  
Fatigue Failure ◽  
Strain Energy ◽  
Hot Spot ◽  
Inelastic Strain ◽  
Fatigue Properties ◽  
Hot Spot Stress ◽  
Fatigue Assessment ◽  
Notch Stress ◽  
Assessment Procedures ◽  
Nominal Stress Approach

Presently in rules for fatigue assessment of structures subjected to intensive alternating service loading the Stress-Life (S-N) criteria are recommended in versions of the Nominal stress approach, Hot-spot stress and Notch-stress approach based on using the stress range a representative of the current damage. The criteria and approaches provide assessment of fatigue properties of structures accompanied with a series of approximations and uncertainties. A physically and mechanically more correct procedures might be provided by the Strain-life and Inelastic strain energy criteria for fatigue failure and approaches, although specific with intrinsic sources of approximations. The nature of approximations in the approaches is briefly commented and feasible means of improvement the fatigue assessment procedures and applications are presented.

Sign in / Sign up

Export Citation Format

Share Document