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Article
Publication date: 23 November 2021

Xiuqian Wu, Dehong Ye, Hanmin Zhang, Li Song and Liping Guo

This paper aims to investigate the root causes of and implement the improvements for the inter layer dielectric (ILD) crack for LQFP C90FG (CMOS90 Floating Gate) wafer…

Abstract

Purpose

This paper aims to investigate the root causes of and implement the improvements for the inter layer dielectric (ILD) crack for LQFP C90FG (CMOS90 Floating Gate) wafer technology devices in copper wire bonding process.

Design/methodology/approach

Failure analysis was conducted including cratering, scanning electron microscopy inspection and focus ion beam cross-section analysis, which showed ILD crack. Root cause investigation of ILD crack rate sudden jumping was carried out with cause-and-effect analysis, which revealed the root cause is shallower lead frame down-set. ILD crack mechanism deep-dive on ILD crack due to shallower lead frame down-set, which revealed the mechanism is lead frame flag floating on heat insert. Further investigation and energy dispersive X-ray analysis found the Cu particles on heat insert is another factor that can result in lead frame flag floating.

Findings

Lead frame flag floating on heat insert caused by shallower lead frame down-set or foreign matter on heat insert is a critical factor of ILD crack that has never been revealed before. Weak wafer structure strength caused by thinner wafer passivation1 thickness and sharp corner at Metal Trench (compared with the benchmarking fab) are other factors that can impact ILD crack.

Originality/value

For ILD crack improvement in copper wire bonding, besides the obvious factors such as wafer structure and wire bonding parameters, also should take other factors into consideration including lead frame flag floating on heat insert and heat insert maintenance.

Details

Microelectronics International, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 1356-5362

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Article
Publication date: 28 December 2020

Nanshan Wang, Heng Liu, Qidan Wang, Shemiao Qi and Yi Liu

This study aims to obtain the dynamic behaviours of cracked rod-fastening rotor bearing system (RFBS), and experimental investigation was carried out to examine the…

Abstract

Purpose

This study aims to obtain the dynamic behaviours of cracked rod-fastening rotor bearing system (RFBS), and experimental investigation was carried out to examine the dynamic characteristics of this kind of assembled rotor bearing system with a transverse crack passing through the critical speed.

Design/methodology/approach

An experimental test rig of cracked RFBS was established for examining the vibration behaviours between intact and cracked system. The crack on the surface of a fastening rod was simulated by wire-electrode cutting processing method. The comprehensive analysis method of vibration was used to obtain the dynamic characteristics such as vibration amplitude, acceleration and whirling orbits before and after the critical speed as well as the instantaneous response in the process of speed up.

Findings

Some experimental vibration datum is obtained for cracked RFBS. The appearance of a crack will introduce the initial bending and make the vibration amplitude, acceleration and instant response in the process of speed up increase greatly as well as the change of whirling orbits.

Originality/value

The actual vibration characteristics for this complex assembled rotor system with a transverse crack are given passing through the critical speed. It can provide some useful help for monitoring the vibration behaviours of this kind of assembled rotor system as well as the detection of the crack fault.

Peer review

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-07-2020-0260/

Details

Industrial Lubrication and Tribology, vol. 73 no. 3
Type: Research Article
ISSN: 0036-8792

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Article
Publication date: 30 April 2020

Xingyang Chen, Linlin Ma, Haoping Xie, Fengting Zhao, Yufeng Ye and Lin Zhang

The purpose of this paper is to present a crack initiation mechanism of the external hydrogen effect on type 304 stainless steel, as well as on fatigue crack propagation…

Abstract

Purpose

The purpose of this paper is to present a crack initiation mechanism of the external hydrogen effect on type 304 stainless steel, as well as on fatigue crack propagation in the presence of hydrogen gas.

Design/methodology/approach

The effects of external hydrogen on hydrogen-assisted crack initiation in type 304 stainless steel were discussed by performing fatigue crack growth rate and fatigue life tests in 5 MPa argon and hydrogen.

Findings

Hydrogen can reduce the incubation period of fatigue crack initiation of smooth fatigue specimens and greatly promote the fatigue crack growth rate during the subsequent fatigue cycle. During the fatigue cycle, hydrogen invades into matrix through the intrusion and extrusion and segregates at the boundaries of α′ martensite and austenite. As the fatigue cycle increased, hydrogen-induced cracks would initiate along the slip bands. The crack initiation progress would greatly accelerate in the presence of hydrogen.

Originality/value

To the best of the authors’ knowledge, this paper is an original work carried out by the authors on the hydrogen environment embrittlement of type 304 stainless steel. The effects of external hydrogen and argon were compared to provide understanding on the hydrogen-assisted crack initiation behaviors during cycle loading.

Details

Anti-Corrosion Methods and Materials, vol. 67 no. 3
Type: Research Article
ISSN: 0003-5599

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Article
Publication date: 23 November 2021

Nan Gao, Shiyu Wang and Muhammad Asad Ur Rehman Bajwa

Gear transmissions are widely utilized in practice. This paper aims to uncouple the crack feature from the cracked time-varying mesh stiffness (TVMS) and investigate the…

Abstract

Purpose

Gear transmissions are widely utilized in practice. This paper aims to uncouple the crack feature from the cracked time-varying mesh stiffness (TVMS) and investigate the effects of the crack on the nonlinear dynamics of a spur gear pair.

Design/methodology/approach

An approximate method to simulate the cracked TVMS is proposed by using an amplitude modulation function. The ratio of mesh stiffness loss is introduced to estimate the TVMS with different crack depths and angles. The dynamic responses are obtained by solving a torsional model which takes the non-loaded static transmission error, the backlash and the cracked TVMS into account. By using the bifurcation diagram, the largest Lyapunov exponent (LLE) and dynamic mesh force, the influences of crack on nonlinear behaviors are examined. The dynamic characteristics are identified from the phase diagram, Poincaré map, dynamic mesh force, time series and FFT spectra.

Findings

The comparison between the healthy and cracked gear pairs indicates that the crack affects the system motions, such as the obvious changes of impact force and unpredictable instability. Besides, the additive and difference combination frequencies can be found in periodic-1 and -2 motions, but they are covered in periodic-3 and chaotic motions. Deeper crack is an important determinant of the nonlinear behaviors at a higher speed.

Originality/value

The research provides an interesting perspective on cracked TVMS and reveals the connection between crack and nonlinear behaviors of the gear pairs.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 16 November 2021

Junguo Wang, Zhaoyuan Yao, M.F. Hassan and Yongxiang Zhao

The paper is devoted to presenting a systematic investigation on the mechanical model and nonlinear dynamic characteristics of spur gear system with and without input shaft crack.

Abstract

Purpose

The paper is devoted to presenting a systematic investigation on the mechanical model and nonlinear dynamic characteristics of spur gear system with and without input shaft crack.

Design/methodology/approach

Considering the backlash, load-distribution, time-varying meshing stiffness and sliding friction, the modelling of a 5DOF gear system is proposed. Likewise, stiffness and damping models under elastohydrodynamic lubrication are developed, and sliding friction between gear pair is also outlined. In particular, a cracked input shaft which affects the support stiffness is presented, and breathing crack in keyway is adopted. On this basis, the dynamic responses of a gear system with and without input shaft crack are examined using numerical method, and some classical response diagrams are given, illustrating the effect of the important parameters on the gear system.

Findings

Dynamic simulation demonstrates that there exist periodic, quasi-periodic and chaotic motions in the gear system, and rational speed of the gear pair has noteworthy effects on vibration characteristic. Besides, comparison between healthy and cracked condition of input shaft indicates that occurring of crack convert periodic motion to quasi-periodic or chaotic motion.

Originality/value

The results give an understanding of the operating conditions under which undesirable dynamic behavior occurs, and provide some useful information to design and diagnose such gear system with crack fault.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 1 February 1990

E.M. Remzi and W.S. Blackburn

Theoretical investigations have been performed on slowly propagating cracks in T‐junctions and cross bars using computer procedures developed to analyse the amount and…

Abstract

Theoretical investigations have been performed on slowly propagating cracks in T‐junctions and cross bars using computer procedures developed to analyse the amount and direction of crack growth using automatic mesh modification and the finite element stress analysis program, BERSAFE. The procedures may be used in a linear or non‐linear material. The crack growth for the linear elastic case is calculated to be in the direction of the maximum energy release rate. For the non‐linear case, the direction is taken to be that of Jwi. These procedures have been applied to fatigue crack growth calculations in this paper.

Details

Engineering Computations, vol. 7 no. 2
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 5 March 2010

Keiji Houjou, Kotoji Ando and Koji Takahashi

Zirconia ceramics exhibit high strength and fracture toughness. The purpose of this paper is to research a possibility of crack healing in zirconia ceramics.

Abstract

Purpose

Zirconia ceramics exhibit high strength and fracture toughness. The purpose of this paper is to research a possibility of crack healing in zirconia ceramics.

Design/methodology/approach

ZrO2/SiC composite ceramics are sintered and subjected to three‐point bending. A surface crack of 100 μm in diameter is formed on each specimen. The cracks are healed and the specimens are tested under bending.

Findings

The paper finds that ZrO2/SiC composite ceramic material had a high crack‐healing ability at a considerably low temperature. For example, a crack of 100 μm in diameter is healed even at 600°C.

Research limitations/implications

The paper provides a low temperature healing and a new mechanism of crack healing.

Originality/value

The paper shows the healing temperature and the minimum time required to heal showed a good proportional relation on the Arrhenius plot at temperatures of 600‐800°C. Moreover, the crack healing is caused by SiO2 cristobalite produced during the healing.

Details

International Journal of Structural Integrity, vol. 1 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 31 December 2019

Shuji Tomaru and Akiyuki Takahashi

Since the most of structures and structural components suffers from cyclic loadings, the study on the fatigue failure due to the crack growth has a great importance. The…

Abstract

Purpose

Since the most of structures and structural components suffers from cyclic loadings, the study on the fatigue failure due to the crack growth has a great importance. The purpose of this paper is to present a three-dimensional fatigue crack growth simulation of embedded cracks using s-version finite element method (SFEM). Using the numerical results, the validity of the fitness-for-service (FFS) code evaluation method is verified.

Design/methodology/approach

In this paper, three-dimensional fatigue crack propagation analysis of embedded cracks is performed using the SFEM. SFEM is a numerical analysis method in which the shape of the structure is represented by a global mesh, and cracks are modeled by local meshes independently. The independent global and local meshes are superimposed to obtain the displacement solution of the problem simultaneously.

Findings

The fatigue crack growth of arbitrary shape of cracks is slow compared to that of the simplified circular crack and the crack approximated based on the FFS code of the Japan Society of Mechanical Engineers (JSME). The results tell us that the FFS code of JSME can provide a conservative evaluation of the fatigue crack growth and the residual life time.

Originality/value

This paper presents a three-dimensional fatigue crack growth simulation of embedded cracks using SFEM. Using this method, it is possible to apply mixed mode loads to complex shaped cracks that are closer to realistic conditions.

Details

International Journal of Structural Integrity, vol. 11 no. 4
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 10 August 2015

Jirí Behal, Petr Homola and Roman Ružek

The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN…

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Abstract

Purpose

The prediction of fatigue crack growth behaviour is an important part of damage tolerance analyses. Recently, the author’s work has focused on evaluating the FASTRAN retardation model. This model is implemented in the AFGROW code, which allows different retardation models to be compared. The primary advantage of the model is that all input parameters, including those for an initial plane-strain state and its transition to a plane-stress-state, are objectively measured using standard middle-crack-tension M(T) specimens. The purpose of this paper is to evaluate the ability of the FASTRAN model to predict correct retardation effects due to high loading peaks that occur during variable amplitude loading in sequences representative of an aircraft service.

Design/methodology/approach

This paper addresses pre-setting of the fracture toughness K R (based on J-integral J Q according to ASTM1820) in the FASTRAN retardation model. A set of experiments were performed using specimens made from a 7475-T7351 aluminium alloy plate. Loading sequences with peaks ordered in ascending-descending blocks were used. The effect of truncating and clipping selected load levels on crack propagation behaviour was evaluated using both experimental data and numerical analyses. The findings were supported by the results of a fractographic analysis.

Findings

Fatigue crack propagation data defined using M(T) specimens made from Al 7475-T7351 alloy indicate the difficulty of evaluating the following two events simultaneously: fatigue crack increments after application of loads with maximum amplitudes that exceeded J Q and subcritical crack increments caused by loads at high stress intensity factors. An effect of overloading peaks with a maximum that exceeds J Q should be assessed using a special analysis beyond the scope of the FASTRAN retardation model.

Originality/value

Measurements of fatigue crack growth on specimens made from 7475 T7351 aluminium alloy were carried out. The results indicated that simultaneously evaluating fatigue crack increments after application of the load amplitude above J Q and subcritical increments caused by the loads at high stress intensity factors is difficult. Experiments demonstrated that if the fatigue crack reaches a specific length, the maximal amplitude load induces considerable crack growth retardation.

Details

International Journal of Structural Integrity, vol. 6 no. 4
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 8 February 2019

Hamid Hamli Benzahar

The purpose of this paper is to evaluate theoretically and numerically the stress and stress intensity factor (SIF) at the time of propagation of the crack in bi-material…

Abstract

Purpose

The purpose of this paper is to evaluate theoretically and numerically the stress and stress intensity factor (SIF) at the time of propagation of the crack in bi-material. The problem is formulated using two thin materials which are bound by a cracked adhesive at the tip and having a micro-crack in one of these two materials.

Design/methodology/approach

The plane stresses and the SIF will be determined as a function of two parameters (Poisson’s ratio and Shear modulus). The numerical analysis is carried out on a flat element, having a main crack in one of these ends, and a micro-crack varies in the vicinity of this main crack. The problem is analyzed by the finite element method and processed by computational software (ABAQUS).

Findings

The numerical and theoretical analysis allowed the author to determine and compare the values of plane stresses and SIF in each area of the material.

Originality/value

The theoretical analysis of SIF is based mainly on a mathematical calculation of equations of plane stresses; these equations are determined by development of complex analytical functions of bi-materials given by other researchers. Using the numerical method, several models are modeled by changing the micro-crack position relative to the main crack to determine the plane stresses and SIF for each position.

Details

International Journal of Structural Integrity, vol. 10 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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