scholarly journals Development of a Fatigue Model for Low Alloy Steels Using a Cycle-Dependent Cohesive Zone Law

2014 ◽  
Vol 6 ◽  
pp. 124037 ◽  
Author(s):  
Kyungmok Kim ◽  
Jaewook Lee ◽  
Joo-Ho Choi
Keyword(s):  
Fracture Energy ◽  
Cohesive Zone ◽  
Fatigue Behavior ◽  
Three Dimensional ◽  
Reduction Rate ◽  
Low Alloy Steels ◽  
Fatigue Model ◽  
Stress Ratios ◽  
Number Of Cycles ◽  
Cycle Dependent

A fatigue model for SAE 4130 steels is developed using a cycle-dependent cohesive zone law. Reduction of fracture energy and degradation of stiffness are considered to describe failure resistance after certain number of cycles. The reduction rate of fracture energy is determined with experimental stress ( S)- number of cycles to failure ( N) scatter found in the literature. Three-dimensional finite element models containing a cohesive zone are generated with commercial software (ABAQUS). Calculated fatigue lives at different stress ratios are in good agreement with experimental ones. In addition, fatigue behavior of hardened SAE 4130 steels is predicted with that of normalized material.

A Probabilistic Fatigue Model for Quasi-Brittle Materials

2014 ◽  
Vol 875-877 ◽  
pp. 1239-1242 ◽  
Author(s):  
Rena C. Yu ◽  
Luis Saucedo ◽  
Gonzalo Ruiz
Keyword(s):  
Stress Ratio ◽  
Brittle Materials ◽  
Initial Distribution ◽  
Fatigue Tests ◽  
Cumulative Distribution ◽  
Fatigue Model ◽  
Stress Ratios ◽  
Number Of Cycles ◽  
Cycles To Failure ◽  
Measured Strength

We aim to develop a new fatigue model valid for quasi-brittle materials like concrete, which properties have considerably larger standard deviation than metals. Having this in mind, we fit the measured strength data with a three-parameter Weibull cumulative distribution function and in turn take it as the initial distribution for an asymptotic fatigue model in concrete. We also take into account the observed influence of frequency and stress ratio on the fatigue life in concrete, both plain and reinforced with fibers. The developed model is validated against fatigue tests in compression on cubic specimens for different stress ratios and loading frequencies. The secondary strain rate is also found to be correlational with the number of cycles to failure.

scholarly journals Experimental Study of the Influence of the Surface Preparation on the Fatigue Behavior of Polyamide Single Lap Joints

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1008
Author(s):  
Francesco Musiari ◽  
Fabrizio Moroni
Keyword(s):  
Experimental Study ◽  
Fatigue Behavior ◽  
Atmospheric Pressure Plasma ◽  
Surface Preparation ◽  
Lap Joints ◽  
Polymeric Surfaces ◽  
Adhesively Bonded Joints ◽  
Single Lap Joints ◽  
Number Of Cycles ◽  
Structural Adhesive

The low quality of adhesion performance on polymeric surfaces has forced the development of specific pretreatments able to toughen the interface between substrate and adhesive. Among these methods, atmospheric pressure plasma treatment (APPT) appears particularly suitable for its environmental compatibility and its effectiveness in altering the chemical state of the surface. In this work, an experimental study on adhesively bonded joints realized using polyamide as substrates and polyurethane as the structural adhesive was carried out with the intent to characterize their fatigue behavior, which represents a key issue of such joints during their working life. The single lap joint (SLJ) geometry was chosen and several surface pretreatments were compared with each other: degreasing, abrasion (alone and followed by APPT) and finally APPT. The results show that the abrasion combined with APPT presents the most promising behavior, which appears consistent with the higher percentage of life spent for crack propagation found by means of DIC on this class of joints with respect to the others. APPT alone confers a good fatigue resistance with respect to the simple abrasion, especially at a low number of cycles to failure.

scholarly journals Digital-Based Healthy Bra Top Design That Promotes the Physical Activity of New Senior Women by Applying an Optimal Pressure

2021 ◽  
Vol 18 (9) ◽  
pp. 4651
Author(s):  
Kuengmi Choi ◽  
Jungil Jun ◽  
Youngshil Ryoo ◽  
Sunmi Park
Keyword(s):  
Physical Activity ◽  
Three Dimensional ◽  
Reduction Rate ◽  
The Body ◽  
Adult Women ◽  
Design Development ◽  
Design Elements ◽  
Body Form ◽  
Senior Women ◽  
Clothing Pressure

A bra use can reduce physiological and physical functions because of clothing pressure, which can be a problem for new senior women starting to lose physical function. The present study presents a bra top design development method for promoting new senior women’s physical activity by identifying problems related to bras’ effects on women’s health and minimizing clothing pressure. The analysis utilized the 3D scan data of 42 adult women (age range: 50s) from the 5th Size Korea Project. Bra top design elements were extracted based on new senior consumers’ needs. We developed an average wireframe reflecting the new senior’s physical characteristics, and a standard body form was developed through surface modeling. To produce a consumer-oriented bra with a body shaping effect and reduced clothing pressure that would not affect physical activities, a three-dimensional pattern was developed applying an optimal reduction rate of 80%. To verify the bra’s adequacy for the body form of new senior women, two market-available bras were selected and fit-compared to the developed product. The developed bra received higher expert appearance evaluation and 3D virtual clothing evaluation scores. This study is significant because by using virtual fitting technology, it provides foundational data to quantify the quality of fashion products.

scholarly journals Application of a Proposed Multi-Positional Circumferential Arm Liposuction Method and Quantification of its Clinical Efficacy Evaluation

2021 ◽  
Author(s):  
Yunpeng Gu ◽  
Ning Kang ◽  
Qianwen Lv ◽  
Yue Qi ◽  
Zhenjun Liu ◽  
...  
Keyword(s):  
Clinical Efficacy ◽  
Quantitative Research ◽  
Three Dimensional ◽  
Reduction Rate ◽  
Full Description ◽  
Type I ◽  
Efficacy Evaluation ◽  
Level Of Evidence ◽  
Simple Measurement ◽  
Based Medicine

Abstract Background Upper arm liposuction mainly focuses on the posterolateral region, which may lead to a lack of harmony between the aspirated and unaspirated areas. In addition, the treatment effect of arm liposuction is often evaluated only by preoperative and postoperative photograph comparison and simple measurement; quantitative research on this topic is still lacking. Methods The multi-positional circumferential arm liposuction (MCAL) technique was proposed and applied to a total of 34 females in our hospital from 2017 to 2019. Three-dimensional data of 12 patients before the operation and after 2–3 months were collected and processed by 3D imaging, and the volume reduction rate was evaluated quantitatively. Results The MCAL method was successfully applied in the clinic, and its surgical effect was quantitatively studied. The mean follow-up time of 12 patients was (75.2 ±13.1) days, and the postoperative volume was significantly reduced. The postoperative volume of patients with type I, type II and type III decreased by (10.79 ±2.55)%, (17.25 ±3.02)% and (22.76 ±3.51)%, respectively. Conclusion Our new MCAL technique was successful, maximizing the esthetic results in upper limb contour refinements in the superficial fascial layer. The clinical efficacy of this proposed MCAL method was evaluated by CT and 3D digital technology, which provided further accuracy in demonstrating its effect on the shape of the arm. Level of evidence IV This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors https://www.springer.com.

scholarly journals Experimental and Numerical Crack Initiation Analysis of the Compressor Blades Working in Resonance Conditions

2011 ◽  
Vol 2011 (3) ◽  
pp. 134-153
Author(s):  
Lucjan Witek
Keyword(s):  
Finite Element ◽  
Crack Initiation ◽  
Transverse Vibration ◽  
Numerical Models ◽  
Fatigue Behavior ◽  
Time History ◽  
Fatigue Properties ◽  
Compressor Blades ◽  
Blade Vibration ◽  
Number Of Cycles

Experimental and Numerical Crack Initiation Analysis of the Compressor Blades Working in Resonance ConditionsThis paper presents the results of a complex experimental and numerical crack initiation analysis of the helicopter turbo-engine compressor blades subjected to vibrations. A nonlinear finite element method was utilized to determine the stress state of the blade during the first mode of transverse vibration. In this analysis, the numerical models without defects as well as those with V-notches were defined. The quality of the numerical solution was checked by the convergence analysis. The obtained results were next used as an input data into crack initiation (ε-N) analyses performed for the load time history equivalent to one cycle of the transverse vibration. In the fatigue analysis, the different methods such as: Neuber elastic-plastic strain correction, linear damage summation and Palmgreen-Miner rule were utilized. As a result of ε-N analysis, the number of load cycles to the first fatigue crack appearing in the compressor blades was obtained. Moreover, the influence of the blade vibration amplitude on the number of cycles to the crack initiation was analyzed. Values of the fatigue properties of the blade material were calculated using the Baumel-Seeger and Muralidharan methods. The influence of both the notch radius and values of the UTS of the blade material on the fatigue behavior of the structure was also considered. In the last part of the work, the finite element results were compared with the results of experimental vibration HCF tests performed for the compressor blades.

Effect of Plasma Nitriding on Ultra-High Cycle Fatigue Behaviors of Ti-6Al-4V

2011 ◽  
Vol 295-297 ◽  
pp. 2386-2389 ◽  
Author(s):  
Ren Hui Tian ◽  
Qiao Lin Ouyang ◽  
Qing Yuan Wang
Keyword(s):  
High Cycle Fatigue ◽  
Plasma Nitriding ◽  
Fatigue Behavior ◽  
Fatigue Crack Initiation ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Ultrasonic Fatigue ◽  
Ultra High Cycle Fatigue ◽  
Stress Ratios

In order to investigate the effect of plasma nitriding treatment on fatigue behavior of titanium alloys, very high cycle fatigue tests were carried out for Ti-6Al-4V alloy using an ultrasonic fatigue machine under load control conditions for stress ratios of R=-1 at frequency of ƒ=20KHz. Experiment results showed that plasma nitriding treatment played the principal role in the internal fatigue crack initiation. More importantly, plasma nitriding treatment had a detrimental effect on fatigue properties of the investigated Ti-6Al-4V alloy, and the fatigue strength of material after plasma nitriding treatment appeared to be significantly reduced about 17% over the untreated material.

scholarly journals Bond Fatigue of TRC with Epoxy Impregnated Carbon Textiles

2019 ◽  
Vol 9 (10) ◽  
pp. 1980 ◽  
Author(s):  
Juliane Wagner ◽  
Manfred Curbach
Keyword(s):  
Cyclic Loading ◽  
Residual Strength ◽  
Negative Impact ◽  
Fatigue Behavior ◽  
Tensile Load ◽  
Textile Reinforced Concrete ◽  
Anchorage Length ◽  
Static Tests ◽  
Number Of Cycles ◽  
Bearing Behavior

For the economical construction of fatigue loaded structures with textile reinforced concrete (TRC), it is necessary to investigate the fatigue behavior of the materials. Since next to the tensile load-bearing behavior, the bond behavior of a material is crucial as well, the present paper deals with the bond fatigue of TRC with epoxy-impregnated carbon textiles. First, static tests are carried out to determine the sufficient anchorage length of the investigated material combination. Afterwards, the influence of cyclic loading on the necessary anchorage length, deformation, stiffness, and residual strength is investigated. The results of the cyclic tests are summarized in stress-number of cycles to failure (S-N) diagrams. In the end, it can be said that the cyclic loading has no negative impact on the necessary anchorage length. If specimens withstand the cyclic loading, there is no difference between their residual strength and the reference strength. The failure of specimens occurs only at high load levels, provided that the anchorage length is sufficient.

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