scholarly journals Fractographic Study of the Mechanism of Destruction of the Nitrocarburized Layer

2020 ◽  
pp. 26-31
Author(s):  
Yulia Bakhracheva ◽  
Keyword(s):  
Ductile Fracture ◽  
Hardened Layer ◽  
Isothermal Process ◽  
Fractographic Study ◽  
Steel Core ◽  
Number Of Cycles ◽  
Ductile Component ◽  
The Impact ◽  
Nitrocarburized Layer ◽  
Impact Ductility

In this paper we investigate the nature of the impact fracture of steels 20 and 20Cr specimens in the nitrocarburized layer and in the core. The object of the study were the samples after thermocycling and isothermal nitrocarburizing. As the results showed, the greatest increase in impact ductility is achieved in five cycles of nitrocarburizing. It is shown that the destruction of the hardened layer and the steel core after the isothermal process is quasirectangular in nature. The presence of the diffusion layer treated by modes of thermocycling nitrocarburizing, areas of ductile fracture and quasi-cleavage in the fracture indicates greater intensity of the process of destruction in comparison with the isothermal process, in which areas of intergranular fracture are present and ductile fracture elements are not present in the fracture. Thus, the fractographic study revealed some features of the mechanism of steel destruction after chemical-thermal nitrocarburizing in comparison with the isothermal process. During thermal cycling of steels, a large amount of the ductile component is observed in the fracture. As the results showed, the greatest increase in impact ductility is achieved in five cycles. In steel 20Cr, the impact ductility increases by 2 times, and in steel 20 by 2.6 times. Increasing the number of cycles to 9 leads to a significant reduction in impact ductility. So in steel 20Cr after chemical-thermal nitrocarburizing, the impact ductility values become less than after classical processing. A further increase in the number of cycles leads to an even greater decrease in the impact ductility values.

Assessment of the mechanical properties of different textile materials used for outer shell of bulletproof vest: woven fabrics for military applications

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
A.I.H. Fayed ◽  
Y.A. Abo El Amaim ◽  
Ossama Ramy ◽  
Doaa H. Elgohary
Keyword(s):  
Mechanical Properties ◽  
Woven Fabrics ◽  
Outer Shell ◽  
Common Mechanism ◽  
Content Type ◽  
Textile Materials ◽  
Steel Core ◽  
Materials Used ◽  
Bulletproof Vest ◽  
The Impact

Purpose This paper aims to investigate the performance of four different textile materials used as an outer shell of the bulletproof vest. Design/methodology/approach In this paper, four different textile materials were used, polyurethane treatment was applied as a surface coating for the woven samples. Mechanical properties were conducted for all samples; scanning electron microscope and X-ray energy disperse spectroscopy were executed to show the surface morphology of samples and the chemical composition of the coating material. Findings One-way ANOVA was used to statistically analyse the results, which proved that all variables were highly significantly affected by using different textile materials, despite the stiffness variable being not significantly affected by textile materials. An overall evaluation was done using radar chart, demonstrated that Cordura material accomplished the best functional performance, using two types of calibres 7.62 × 54 mild steel core and 7.62 × 54 armour piercing incendiary; the common mechanism was localized burn because of the incendiary effect of the projectile in addition to tearing mechanism starting from inside because of penetration effect of the steel core. Originality/value This work was addressed to analyse the impact of using four different materials on its performance as the outer shell of bulletproof vest to achieve the desired degree of protection.

Fracture in Taylor Rod Impact Test Specimens

2010 ◽  
Author(s):  
Sachin S. Gautam ◽  
Ravindra K. Saxena ◽  
P. M. Dixit
Keyword(s):  
Ductile Fracture ◽  
Damage Mechanics ◽  
Continuum Damage Mechanics ◽  
Outer Edge ◽  
Impact Surface ◽  
Mechanics Model ◽  
Contact Impact ◽  
Impact Problems ◽  
The Impact ◽  
Aisi1045 Steel

High velocity contact-impact problems are of great interest in industries related to aerospace, mechanical and civil engineering. Ductile fracture often occurs in such applications. Taylor rod impact tests are used as experimental and numerical tests for determining the mechanical behaviour of materials subjected to high strain rates. At sufficiently high velocities, a significant plastic deformation leading to fracture is observed. In this paper, ductile fracture in Taylor rod made of AISI1045 steel is simulated using a continuum damage mechanics model. Simulations are performed for the velocity of 250 and 300 m/s. It is observed that, at lower velocities, tensile cracks are observed at the outer edge of the impact surface. On the other hand, at higher velocities, the fracture is observed at the central axis (confined fracture) as well as at the outer edge leading to fragmentation. Both the results are consistent with the experimental results available in the literature.

scholarly journals Selected Properties of the Surface Layer of C45 Steel Parts Subjected to Laser Cutting and Ball Burnishing

Materials ◽  
2020 ◽  
Vol 13 (15) ◽  
pp. 3429 ◽  
Author(s):  
Agnieszka Skoczylas ◽  
Kazimierz Zaleski
Keyword(s):  
Surface Layer ◽  
Residual Stresses ◽  
Laser Cutting ◽  
Experimental Studies ◽  
Hardened Layer ◽  
Ball Burnishing ◽  
Absolute Value ◽  
The Impact ◽  
Compressive Residual Stresses

In this article, we report the results of experimental studies on the impact of ball burnishing parameters on the roughness, microstructure and microhardness of the surface layer of laser-cut C45 steel parts. We also analysed the distribution of residual stresses generated in the surface layer of these parts. Laser-cut parts often require finishing to improve the quality of their surface. The tests performed in this study were aimed at assessing whether ball burnishing could be used as a finishing operation for parts of this type. Ball burnishing tests were performed on an FV-580a vertical machining centre using a mechanically controlled burnishing tool. The following parameters were varied during the ball burnishing tests: burnishing force Fn, path interval fw and the diameter of the burnishing ball dn. Ball burnishing of laser-cut C45 steel parts reduced the surface roughness parameters Sa and Sz by up to 60% in relation to the values obtained after laser cutting. Finish machining also led to the reorganization of the geometric structure of the surface, resulting in an increase in the absolute value of skewness Ssk. This was accompanied by an increment in microhardness (maximum microhardness increment was ΔHV = 95 HV0.05, and the thickness of the hardened layer was gh = 40 µm) and formation of compressive residual stresses in the surface layer.

A prospective randomized phase II trial evaluating maintenance GM-CSF in an intermittent chemotherapy (chemo) regimen for metastatic castration-resistant prostate cancer (mCRPC): A DoD prostate cancer clinical trials consortium trial.

2012 ◽  
Vol 30 (5_suppl) ◽  
pp. 35-35
Author(s):  
Eric Jay Small ◽  
Vivian K. Weinberg ◽  
Charles J. Ryan ◽  
Celestia S. Higano ◽  
Amy Mimi Lin ◽  
...  
Keyword(s):  
Prostate Cancer ◽  
Optimal Number ◽  
Castration Resistant Prostate Cancer ◽  
Time To Progression ◽  
Gm Csf ◽  
Castration Resistant ◽  
Randomized Phase Ii ◽  
Intermittent Chemotherapy ◽  
Number Of Cycles ◽  
The Impact

35 Background: The optimal number of cycles of docetaxel for patients (pts) with mCRPC is not known, and in practice, treatment breaks are common. The current study was designed to test the safety and efficacy of utilizing 6 cycles of standard docetaxel with chemo free intervals in patients who achieve and maintain a response to docetaxel. Methods: Pts with mCRPC, no prior chemo, and KPS > 60% were eligible. Pts were treated with “induction” docetaxel 75 mg/m2 q 3 weeks, and prednisone 5 mg po bid. PSAWG1 criteria were used to define response and progression. After 6 cycles, responding pts stopped chemo and were randomized to observation (Obs) or to GM-CSF, 250 mcg/m2 daily for 14 days out of every 28-day cycle. Pts were followed with monthly PSA and imaging every 2 cycles until progression, at which point docetaxel was reinitiated for another 6 cycles, followed by the same “off chemo” regimen. The primary endpoint was the time to progression while on chemo (time to chemo resistance). Results: 114 pts have been enrolled: 3 are undergoing induction, and 111 are therefore evaluable. Of these pts, 82 completed induction, (10 did not due to PD, 9 due to adverse events (AE), 10 due to pt or MD choice). Of 111 evaluable pts, 48 (43%) had a response to chemo and were eligible for randomization. 22 were randomized to Obs and 26 to GM-CSF. Of 48 randomized pts, 25 restarted chemo, all for PSA PD. (23 pts did not re-start chemo because of AE, other therapy being started, or pt choice; 1 pt is still on GM-CSF.) 6/25 (24%) pts experienced a response to the 2nd series of chemo, and 1/6 (17%) to the 3rd. The time to chemo re-initiation (n=25) was 3.1 mos in Obs pts and 4.2 mos in GM-CSF pts. Conclusions: 43% of patients met criteria for undergoing intermittent chemo. The response proportion to the 1st, 2nd, and 3rd series of docetaxel was 43%, 24% and 17%, respectively. GM-CSF may modestly delay the time to chemo re-initiation, but the sample size is small and insufficient to assess the impact of GM-CSF on time to chemo resistance.

Prevalence of atypical urine cytology in patients treated with gemcitabine-cisplatin (GC) for urothelial carcinoma (UC).

2015 ◽  
Vol 33 (7_suppl) ◽  
pp. 363-363
Author(s):  
Kimberly R. Kruczek ◽  
Lu Wang ◽  
Guliz Barkan ◽  
Elizabeth Henry
Keyword(s):  
General Population ◽  
Median Number ◽  
Urine Cytology ◽  
Intravesical Therapy ◽  
Urothelial Cells ◽  
Single Institution ◽  
Previously Treated ◽  
Number Of Cycles ◽  
The Impact ◽  
Post Therapy

363 Background: The prevalence of atypical urothelial cells (AUC) in the general population is estimated to range between 2-23% with known variability between individual pathologists’ use of this diagnosis. At our institution, the AUC rate for all urinary tract cytology (UTC) is 6.1%. Increased rates of urothelial atypia have been described in pts receiving certain systemic and intravesical therapies for UC. This may confound the use of UTC for post-therapy surveillance. Our objective is to describe the prevalence of urothelial atypia in pts treated with GC, as it is currently unknown. Methods: Patients who received at least one cycle of GC for UC at a single institution from 1/1/2007-9/30/2014 were identified. Demographics, clinical characteristics, treatment setting, number of cycles, and specimen type were recorded. Urine cytology reports were reviewed and tabulated. Results: Seventy-four pts treated with GC were identified. Median age at treatment was 65 (range 42-80); 58 (78%) were male. Median number of cycles was 4 (range 1-9). Treatment settings were: 15 (20%) neoadjuvant, 38 (51%) adjuvant, and 21 (28%) metastatic. Ten (14%) pts were previously treated with intravesical therapy (9 BCG, 1 mitomycin). Thirty-six (49%) pts had urine cytology available. Twenty-seven (75%) pts had at least 1 urine cytology within 12 months post-chemotherapy, with 44 total specimens. Nine (25%) pts had cytology performed >1-year post treatment. Cytology specimens within 12 months post-chemotherapy were reviewed. Two out of 44 specimens had AUC (5%), with all other cases negative. The pts with AUC were male, received adjuvant therapy, had prior radical cystectomy with orthotopic neobladder reconstruction, and had no intravesical therapy. Conclusions: The prevalence of AUC in pts treated with GC was similar to the general population. Chemotherapy with GC does not appear to morphologically affect urothelial cells. If atypical UTC is seen in this population, the cause should be investigated, as GC does not appear to influence urothelial changes. Additional study is needed to characterize the impact of systemic therapy on urothelial atypia and to guide the use of urine cytology for post-therapy surveillance.

Effect of the metal base structure on the impact ductility of malleable and high-tensile cast irons

1988 ◽  
Vol 30 (4) ◽  
pp. 276-277
Author(s):  
V. I. Ovchinnikov ◽  
N. A. Umerenkova ◽  
V. A. Sharkov
Keyword(s):  
Cast Irons ◽  
Metal Base ◽  
The Impact ◽  
Impact Ductility ◽  
Base Structure

Diamond Tools Matrix Composites of Co Replaced by Fe with Doping Rare Earth

2012 ◽  
Vol 424-425 ◽  
pp. 848-851 ◽  
Author(s):  
Qing Hua Zou
Keyword(s):  
Rare Earth ◽  
Bending Strength ◽  
Service Performance ◽  
Rare Earth Doping ◽  
Matrix Composites ◽  
Metal Powders ◽  
Diamond Tools ◽  
Process Route ◽  
The Impact ◽  
Impact Ductility

The experiment on adding rare earth elements doped in diamond matrix composites is made. Based on the doping of rare earth in metal powders including tungsten carbide, iron and nickel, Co is entirely replaced by Fe with rare earth in diamond matrix composites, and the process route of rare earth doping is indicated. The related performance of is measured, and the results obtained show that the bending strength, the hardness and the impact ductility of Fe matrix composites with rare earth are improved. The practical service performance of Fe matrix composites with rare earth has reached up to the practical service performance of Co matrix, and bearing good practical service performance, low price, have made corresponding diamond tools.

scholarly journals Impact of Peracetic Acid on the Dynamic Cyclic Fatigue of Heat-Treated Nickel-Titanium Rotary Endodontic Instrument

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Suhad Jabbar Hamed Al-Nasrawi ◽  
Zuha Ayad Jaber ◽  
Nibrass Talib Al-Quraine ◽  
Abtesam Imhemed Aljdaimi ◽  
Sattar Jabbar Abdul-Zahra Al-Hmedat ◽  
...  
Keyword(s):  
Fatigue Resistance ◽  
Peracetic Acid ◽  
Cyclic Fatigue ◽  
Nickel Titanium ◽  
Control Group ◽  
Heat Treated ◽  
Respective Control Group ◽  
Before And After ◽  
Number Of Cycles ◽  
The Impact

Peracetic acid (PAA) is widely used as a sterilizing/disinfecting agent, and, in endodontics, it has been introduced as a promising irrigant in root canal treatment. It has been used at different concentrations to achieve various functions. However, endodontic instruments in contact with PAA of a certain concentration may affect their fatigue resistance. Therefore, the aim of this study was to investigate the impact of PAA on the cyclic fatigue resistance of three commercial heat-treated nickel-titanium (NiTi) rotary files. Three types of heat-treated NiTi rotary files were selected: One Curve (OC), ProTaper Gold (PTG), and Wave One Gold (WOG). Each type was divided into three subgroups (n = 6 for each file type): (1) untreated instruments; (2) files immersed in 0.002% PAA; and (3) files immersed in 0.35% PAA. The performance of each file type was tested in a simulated canal. The number of cycles to fracture (NCF) was determined to assess cyclic fatigue resistance of the files. Independent sample t-test was applied to compare each treated file within a subgroup with its respective control group, and one-way ANOVA was used for comparison among the main groups. All types of tested files revealed a significant decline in the cyclic fatigue resistance after exposure to 0.002% PAA except the PTG ( P = 0.209 ). After exposure of the files to a higher concentration (0.35% PAA), a dramatic reduction was demonstrated by all the groups. Before and after exposure of the files to PAA, PTG displayed the highest cyclic fatigue resistance, followed by the WOG, while the OC showed the lowest resistance. Exposure of heated-treated NiTi files to PAA in a relatively high or low concentration adversely affects the cyclic fatigue resistance. The PTG files demonstrated the best performance among the tested types and can be disinfected with 0.002% PAA for clinical purpose.

scholarly journals Truck-Platooning Impacts on Flexible Pavements: Experimental and Mechanistic Approaches

2021 ◽  
Author(s):  
Aravind Ramakrishnan ◽  
◽  
Ashraf Alrajhi ◽  
Egemen Okte ◽  
Hasan Ozer ◽  
...  
Keyword(s):  
Permanent Deformation ◽  
Rest Period ◽  
Gaussian Mixture ◽  
Experimental Program ◽  
Fe Model ◽  
Equivalent Number ◽  
Number Of Cycles ◽  
Pavement Damage ◽  
Shift Model ◽  
The Impact

Truck platoons are expected to improve safety and reduce fuel consumption. However, their use is projected to accelerate pavement damage due to channelized-load application (lack of wander) and potentially reduced duration between truck-loading applications (reduced rest period). The effect of wander on pavement damage is well documented, while relatively few studies are available on the effect of rest period on pavement permanent deformation. Therefore, the main objective of this study was to quantify the impact of rest period theoretically, using a numerical method, and experimentally, using laboratory testing. A 3-D finite-element (FE) pavement model was developed and run to quantify the effect of rest period. Strain recovery and accumulation were predicted by fitting Gaussian mixture models to the strain values computed from the FE model. The effect of rest period was found to be insignificant for truck spacing greater than 10 ft. An experimental program was conducted, and several asphalt concrete (AC) mixes were considered at various stress levels, temperatures, and rest periods. Test results showed that AC deformation increased with rest period, irrespective of AC-mix type, stress level, and/or temperature. This observation was attributed to a well-documented hardening–relaxation mechanism, which occurs during AC plastic deformation. Hence, experimental and FE-model results are conflicting due to modeling AC as a viscoelastic and the difference in the loading mechanism. A shift model was developed by extending the time–temperature superposition concept to incorporate rest period, using the experimental data. The shift factors were used to compute the equivalent number of cycles for various platoon scenarios (truck spacings or rest period). The shift model was implemented in AASHTOware pavement mechanic–empirical design (PMED) guidelines for the calculation of rutting using equivalent number of cycles.

scholarly journals Impact of a Hybrid Assisted Wheelchair Propulsion System on Motion Kinematics during Climbing up a Slope

2020 ◽  
Vol 10 (3) ◽  
pp. 1025 ◽  
Author(s):  
Bartosz Wieczorek ◽  
Łukasz Warguła ◽  
Dominik Rybarczyk
Keyword(s):  
Electric Propulsion ◽  
Propulsion System ◽  
Operating Conditions ◽  
Amplification Coefficient ◽  
Wheelchair Propulsion ◽  
Depth Analysis ◽  
Manual Propulsion ◽  
Number Of Cycles ◽  
The Hill ◽  
The Impact

Overcoming terrain obstacles presents a major problem for people with disabilities or with limited mobility who are dependent on wheelchairs. An engineering solution designed to facilitate the use of wheelchairs are assisted-propulsion systems. The objective of the research described in this article is to analyze the impact of the hybrid manual–electric wheelchair propulsion system on the kinematics of the anthropotechnical system when climbing hills. The tests were carried out on a wheelchair ramp with an incline of 4°, using a prototype wheelchair with a hybrid manual–electric propulsion system in accordance with the patent application P.427855. The test subjects were three people whose task was to propel the wheelchair in two assistance modes supporting manual propulsion. The first mode is hill-climbing assistance, while the second one is assistance with propulsion torque in the propulsive phase. During the tests, several kinematic parameters of the wheelchair were monitored. An in-depth analysis was performed for the amplitude of speed during a hill climb and the number of propulsive cycles performed on a hill. The tests performed showed that when propelling the wheelchair only using the hand rims, the subject needed an average of 13 ± 1 pushes on the uphill slope, and their speed amplitude was 1.8 km/h with an average speed of 1.73 km/h. The climbing assistance mode reduced the speed amplitude to 0.76 km/h. The torque-assisted mode in the propulsive phase reduced the number of cycles required to climb the hill from 13 to 6, while in the climbing assistance mode the number of cycles required to climb the hill was reduced from 12 to 10 cycles. The tests were carried out at various values of assistance and assistance amplification coefficient, and the most optimally selected parameters of this coefficient are presented in the results. The tests proved that electric propulsion assistance has a beneficial and significant impact on the kinematics of manual wheelchair propulsion when compared to a classic manual propulsion system when overcoming hills. In addition, assistance and assistance amplification coefficient were proved to be correlated with operating conditions and the user’s individual characteristics.

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