Internal Versus External Cracking—Their Impact on the Fatigue Life of Modern Smoothbore Autofrettaged Tank Gun Barrels

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
M. Perl ◽  
T. Saley
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Crack Depth ◽  
Fatigue Crack Initiation ◽  
Element Model ◽  
Initial Crack ◽  
Factors Affecting ◽  
External Crack ◽  
Crack Initiation Life ◽  
Major Factors

Abstract An extensive analysis of the fatigue life of a typical modern autofrettaged smoothbore tank barrel, cracked either internally or externally, in terms of the initial crack depth and shape, type and level of autofrettage, was conducted. Five overstraining cases were considered: no-autofrettage, 70% and 100% hydraulic autofrettage, and 70% and 100% swage autofrettage. KINmax, the maximum combined stress intensity factor (SIF) KINmax = (KIP + KIA) max, due to both internal pressure and autofrettage, as a function of crack depth for a large number of internal and external crack configurations was determined by the finite element method (FEM). A novel realistic experimentally based autofrettage model, incorporating the Bauschinger effect, was integrated into the finite element model, replicating both the hydraulic and swage autofrettage residual stress fields (RSFs) accurately. Fatigue lives were evaluated by integrating Paris' Law using the above values of KINmax. The following conclusions can be drawn from the results: hydraulic and swage autofrettage have a dramatic beneficial effect in extending the fatigue life of an overstrained barrel 4–11 times as compared to an identical nonautofrettaged tube. The fatigue life of overstrained barrels is controlled by internal cracking, for barrels overstrained by up to ε = 100% hydraulic autofrettage, by up to ε = 70% in the case of swage autofrettage, and by external cracking for ε = 100% swage autofrettaged. Eliminating or carefully designing stress concentrators on the tube's external face and keeping away from corrosive agents thus, extending the fatigue-crack initiation life of an external crack, enables the increase of the level of swage autofrettage to up to ε = 100%. Swage autofrettage is much more superior to hydraulic autofrettage. The fatigue life of a 70% swaged autofrettaged barrel is 1.5 times higher than that of a 100% hydraulically autofrettaged tube. If full swage autofrettage is permissible, the fatigue life of such a barrel is twofold that of a fully hydraulically autofrettaged tube. Unlike the commonly accepted concept, the level of hydraulic autofrettage should not be limited to 70%, and full hydraulic autofrettage should be used. Similarly, in the case of swage autofrettage, if the detrimental effect of external cracking is removed by proper design and maintenance of the tube's outer surface, the level of autofrettage can be increased to up to ε = 100%, thus, gaining an increase of 33% in the fatigue life as compared to overstraining the barrel to only ε = 70%. Initial crack depth and shape are major factors affecting the fatigue life of the barrel. The deeper the initial crack depth, a0, and the slenderer its shape, a/c→ 0, the shorter the fatigue life of the barrel.

Finite Element Modeling of Simultaneous Ultrasonic Bumping With Au Balls

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Wan Ho Song ◽  
Ali Karimi ◽  
Yan Huang ◽  
Michael Mayer ◽  
Norman Zhou ◽  
...  
Keyword(s):  
Finite Element ◽  
Lateral Displacement ◽  
Data Distribution ◽  
Element Model ◽  
Factors Affecting ◽  
Bump Height ◽  
Ultrasonic Bonding ◽  
Main Factors ◽  
Major Factors ◽  
Microelectronic Components

Bumping of microcircuits and substrates establishes interconnect points required for subsequent bonding of microelectronic components, allowing for power and data distribution. Simultaneous ultrasonic bonding of individual Au balls promises to accelerate bumping processes and is studied using a finite element model. The model covers the static forces at the end of a successful bonding operation and analyzes the interfacial stresses between bumps and substrate. The modeling shows the vertical forces acting on the bumps when a lateral displacement of the bonding tool is applied. When designing a practical bonding application, the control of such vertical forces is recommended. A sensitivity analysis is conducted to study the effect of the main factors on the model responses. This analysis reveals that variations in bump height and bonding tool elastic modulus are the major factors affecting the forces on the bumps.

Damage Mechanics-Finite Element Method for Vibrational Fatigue Life Prediction of Engineering Structures with Damping

2014 ◽  
Vol 472 ◽  
pp. 17-21 ◽  
Author(s):  
Lin Lin Sun ◽  
Wei Ping Hu ◽  
Miao Zhang ◽  
Qing Chun Meng
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Fatigue Life ◽  
Life Prediction ◽  
Damage Mechanics ◽  
Fatigue Crack Initiation ◽  
Engineering Structures ◽  
Engineering Structure ◽  
Crack Initiation Life ◽  
Element Method

This paper provides a new method which is damage mechanics to predict the fatigue life of engineering structure with damping under resonant loading. The material parameters are obtained by the results of the fatigue test of standard specimens. And based on the further development of APDL language, damage mechanics-finite element method for vibration life prediction under resonant loading is used in ANSYS. Finally, the vibrational fatigue crack initiation life of an aluminum alloy beam with damping carrying load of various frequencies is calculated. Whats more, this research provides a feasible way to predict the fatigue live of an engineering structure by means of damage mechanics.

Stress Strain Analysis of Steel Specimens Not Wholly Quenched

2011 ◽  
Vol 261-263 ◽  
pp. 702-706
Author(s):  
Rui Jie Wang ◽  
He Ming Cheng ◽  
Bao Dong Shao ◽  
Jian Yun Li
Keyword(s):  
Finite Element ◽  
Fatigue Crack Initiation ◽  
Strain Analysis ◽  
Element Model ◽  
Cyclic Strength ◽  
Work Piece ◽  
Stress Strain ◽  
Element Analysis ◽  
Quenched Steel ◽  
Crack Initiation Life

A finite element model of not wholly quenched steel fatigue specimen is established. Hardness value of some distance to work piece surface are assumed different and cyclic strength coefficients of different zones are different, both is assumed to be proportional to hardness value. Elasto-plastic finite element analysis was carried out for this model. According to the stress-strain distribution on transverse section, the effect of not wholly quenched on fatigue crack initiation life is analyzed.

The Influence of Fatigue Life for Shoulder Fillet Parameter in Stepped Shaft under Torsion Load

2013 ◽  
Vol 404 ◽  
pp. 228-231 ◽  
Author(s):  
Yong Zhuang Yuan
Keyword(s):  
Fatigue Life ◽  
Fatigue Crack Initiation ◽  
Local Stress ◽  
Element Model ◽  
Stress Strain ◽  
Stepped Shaft ◽  
Transition Radius ◽  
Crack Initiation Life ◽  
Set Up ◽  
Strain Method

The principle of fatigue life computation was presented on the basis of local stress-strain method. It was set up that the finite element model of stepped shaft with different radii of round corner and radius ratios. The local stress and strain were computed at shaft shoulder fillet under torsion load. The fatigue crack initiation life was determined by means of local stress-strain method under symmetric cyclic torsion load. The result showed that the fatigue life increased with the values of fillet increase and decreased with the values of radius ratio increase, and the smaller of the transition radius was, the shorter of the life would be.

The structural optimization of roadheader conical picks based on fatigue life

2018 ◽  
Vol 09 (02) ◽  
pp. 1850013 ◽  
Author(s):  
Zhenguo Lu ◽  
Lirong Wan ◽  
Qingliang Zeng ◽  
Xin Zhang ◽  
Kuidong Gao
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Static Analysis ◽  
Element Model ◽  
Cutting Resistance ◽  
Strength Failure ◽  
New Type ◽  
Conical Picks ◽  
Fatigue Life Analysis ◽  
The Finite Element Model

Conical picks are the key cutting components used on roadheaders, and they are replaced frequently because of the bad working conditions. Picks did not meet the fatigue life when they were damaged by abrasion, so the pick fatigue life and strength are excessive. In the paper, in order to reduce the abrasion and save the materials, structure optimization was carried out. For static analysis and fatigue life prediction, the simulation program was proposed based on mathematical models to obtain the cutting resistance. Furthermore, the finite element models for static analysis and fatigue life analysis were proposed. The results indicated that fatigue life damage and strength failure of the cutting pick would never happen. Subsequently, the initial optimization model and the finite element model of picks were developed. According to the optimized results, a new type of pick was developed based on the working and installing conditions of the traditional pick. Finally, the previous analysis methods used for traditional methods were carried out again for the new type picks. The results show that new type of pick can satisfy the strength and fatigue life requirements.

Stress and Fatigue Life Modeling of Cannon Breech Closures Including Effects of Material Strength and Residual Stress

2000 ◽  
Vol 123 (1) ◽  
pp. 150-154
Author(s):  
John H. Underwood ◽  
Michael J. Glennon
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Fatigue Life ◽  
Yield Strength ◽  
Residual Stresses ◽  
Solid Mechanics ◽  
Element Model ◽  
Pressure Vessels ◽  
Material Strength ◽  
Element Analysis

Laboratory fatigue life results are summarized from several test series of high-strength steel cannon breech closure assemblies pressurized by rapid application of hydraulic oil. The tests were performed to determine safe fatigue lives of high-pressure components at the breech end of the cannon and breech assembly. Careful reanalysis of the fatigue life tests provides data for stress and fatigue life models for breech components, over the following ranges of key parameters: 380–745 MPa cyclic internal pressure; 100–160 mm bore diameter cannon pressure vessels; 1040–1170 MPa yield strength A723 steel; no residual stress, shot peen residual stress, overload residual stress. Modeling of applied and residual stresses at the location of the fatigue failure site is performed by elastic-plastic finite element analysis using ABAQUS and by solid mechanics analysis. Shot peen and overload residual stresses are modeled by superposing typical or calculated residual stress distributions on the applied stresses. Overload residual stresses are obtained directly from the finite element model of the breech, with the breech overload applied to the model in the same way as with actual components. Modeling of the fatigue life of the components is based on the fatigue intensity factor concept of Underwood and Parker, a fracture mechanics description of life that accounts for residual stresses, material yield strength and initial defect size. The fatigue life model describes six test conditions in a stress versus life plot with an R2 correlation of 0.94, and shows significantly lower correlation when known variations in yield strength, stress concentration factor, or residual stress are not included in the model input, thus demonstrating the model sensitivity to these variables.

Fatigue Behavior of Circumferentially Notched Round Bars of Austenitic Stainless Steel Under Torsional and Axial Loads

2010 ◽  
Author(s):  
Masao Itatani ◽  
Keisuke Tanaka ◽  
Isao Ohkawa ◽  
Takehisa Yamada ◽  
Toshiyuki Saito
Keyword(s):  
Fatigue Life ◽  
Stress Concentration ◽  
Crack Initiation ◽  
Crack Propagation ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Static Tension ◽  
Cyclic Torsion ◽  
Cyclic Tension ◽  
Crack Initiation Life

Fatigue tests of smooth and notched round bars of austenitic stainless steels SUS316NG and SUS316L were conducted under cyclic tension and cyclic torsion with and without static tension. Fatigue strength under fully reversed (R=−1) cyclic tension once increased with increasing stress concentration factor up to Kt=1.5, but it decreased from Kt=1.5 to 2.5. Fatigue life increased with increasing stress concentration under pure cyclic torsion, while it decreased with increasing stress concentration under cyclic torsion with static tension. From the measurement of fatigue crack initiation and propagation lives using electric potential drop method, it was found that the crack initiation life decreased with increasing stress concentration and the crack propagation life increased with increasing stress concentration under pure cyclic torsion. Under cyclic torsion with static tension, the crack initiation life also decreased with increasing stress concentration but the crack propagation life decreased or not changed with increasing stress concentration then the total fatigue life of sharper notched specimen decreased. It was also found that the fatigue life of smooth specimen under cyclic torsion with static tension was longer than that under pure cyclic torsion. This behavior could be explained based on the cyclic strain hardening under non-proportional loading and the difference in crack path with and without static tension.

scholarly journals Factors Affecting the Severity of Placental Abruption in Pregnant Vehicle Drivers: Analysis with a Novel Finite Element Model

Healthcare ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 27
Author(s):  
Katsunori Tanaka ◽  
Yasuki Motozawa ◽  
Kentaro Takahashi ◽  
Tetsuo Maki ◽  
Masahito Hitosugi
Keyword(s):  
Finite Element ◽  
Pregnant Woman ◽  
Finite Element Model ◽  
Placental Abruption ◽  
Motor Vehicle ◽  
Human Subjects ◽  
Element Model ◽  
Collision Velocity ◽  
Vehicle Collisions ◽  
Factors Affecting

We clarified factors affecting the severity of placental abruption in motor vehicle collisions by quantitively analyzing the area of placental abruption in a numerical simulation of an unrestrained pregnant vehicle driver at collision velocities of 3 and 6 m/s. For the simulation, we constructed a novel finite element model of a small 30-week pregnant woman, which was validated anthropometrically using computed tomography data and biomechanically using previous examinations of post-mortem human subjects. In the simulation, stress in the elements of the utero–placental interface was computed, and those elements exceeding a failure criterion were considered to be abrupted. It was found that a doubling of the collision velocity increased the area of placental abruption 10-fold, and the abruption area was approximately 20% for a collision velocity of 6 m/s, which is lower than the speed limit for general roads. This result implies that even low-speed vehicle collisions have negative maternal and fetal outcomes owing to placental abruption without a seatbelt restraint. Additionally, contact to the abdomen, 30 mm below the umbilicus, led to a larger placental abruption area than contact at the umbilicus level when the placenta was located at the uterus fundus. The results support that a reduction in the collision speed and seatbelt restraint at a suitable position are important to decrease the placental abruption area and therefore protect a pregnant woman and her fetus in a motor vehicle collision.

Numerical Analysis of API 5L X42 and X52 Vintage Pipes with Cracks in Corrosion Defects Using Extended Finite Element Method

2021 ◽  
Author(s):  
Xinfang Zhang ◽  
Meng Lin ◽  
Allan Okodi ◽  
Leichuan Tan ◽  
Juliana Leung ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Extended Finite Element Method ◽  
Pipe Wall ◽  
Crack Depth ◽  
Initial Crack ◽  
Extended Finite Element ◽  
Failure Pressure ◽  
Corrosion Defects ◽  
Element Method

Abstract Cracks and corrosion in pipelines can occur simultaneously, representing a hybrid defect known as cracks in corrosion (CIC), which is often difficult to model using the available assessment codes or methods. As a result, detailed modeling of CIC has not been studied extensively. In this study, the extended finite element method (XFEM) has been applied to predict the failure pressures of CIC defects in API 5L Grade X42 and X52 pipes. The pipes were only subjected to internal pressure and the XFEM models were validated using full-scale burst tests available in the literature. Several CIC models with constant total defect depths (55%, and 60% of wall thickness) were constructed to investigate the effect of the initial crack depth on the failure pressure. The failure criterion was defined when wall penetration occurred due to crack growth, i.e., the instance the crack reached the innermost element of the pipe wall mesh. It was observed that for shorter cracks, the failure pressure decreased with the increase of the initial crack depth. The results indicated that the CIC defect could be treated as crack-only defects when the initial crack depth exceeded 50% of the total defect depth. However, for longer cracks, the initial crack depth was found to have a negligible effect on the failure pressure, implying that the CIC defect could be treated as either a crack or a corrosion utilizing the available assessment methods.

Numerical Study of Welding Sequence on the Residual Stress Field in a Thick-Walled Tee Joint

2011 ◽  
Vol 219-220 ◽  
pp. 1211-1214
Author(s):  
Wei Jiang
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Numerical Study ◽  
Three Dimensional ◽  
Element Model ◽  
Residual Stress Field ◽  
Factors Affecting ◽  
Welding Sequence ◽  
Welding Sequences ◽  
Three Dimensional Finite Element

Finite element simulation is an efficient method for studying factors affecting weld-induced residual stress distributions. In this paper, a validated three-dimensional finite element model consisting of sequentially coupled thermal and structural analyses was developed. Three possible symmetrical welding sequences, i.e. one-welder, two-welder and four-welder sequence, which were perceived to generate the least distortion in actual welding circumstances, were proposed and their influences on the residual stress fields in a thick-walled tee joint were investigated. Appropriate conclusions and recommendations regarding welding sequences are presented.

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