Crystal-plasticity modelling of machining

A machining process is one of the most common techniques used to remove material in order to create a final product. Most studies on mechanisms of cutting are performed under the assumption that the studied material is isotropic, homogeneous and continuous. One important feature of material- its anisotropyis linked to its crystallographic nature, which is usually ignored in machining studies. A crystallographic orientation of a workpiece material exerts a great influence on the chip-formation mechanism. Thus, there is a need for developing fundamental understanding of material’s behaviour and material removal processes. While the effect of crystallographic orientation on cutting-force variation is extensively reported in the literature, the development of the single crystal machining models is somewhat limited. [Continues.

Variation of cutting forces in machining of f.c.c. single crystals

In this study, micro-machining of f.c.c. single-crystal materials was investigated based on a hybrid modelling approach combining smoothed particle hydrodynamics and continuum finite element analysis. The numerical modelling was implemented in the commercial software ABAQUS/Explicit by employing a user-defined subroutine VUMAT for a crystal plasticity formulation to gain insight into the underlying mechanisms that drive a plastic response of materials in high deformation processes. The numerical studies demonstrate that cutting force variations in different cutting directions are similar for different f.c.c. crystals even though the magnitudes of the cutting forces are different

Modelling of vibration assisted machining f.c.c single crystal

In this paper, a developed three-dimensional model combining finite-element and smoothed-particle hydrodynamics approaches is presented. It incorporates a crystal-plasticity theory for vibration-assisted machining into ABAQUS/Explicit software by using a user-defined subroutine VUMAT. The paper presents quantitative comparison of cutting-force variation for VAM and conventional machining with identical cutting parameters for anisotropic workpieces. The obtained simulation results demonstrated that the (101) crystal orientation with a cutting direction at 30° had the highest reduction in a cutting force for three levels of vibration amplitude (10, 20 and 30 μm) and three levels of frequency (15, 20 and 25 kHz)

3D‑printed biomimetic bone implant polymeric composite scaffolds

© The Author(s) 2023. This article is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.This research introduced a new poly-ether-ether-ketone calcium hydroxyapatite (PEEK-cHAp) composite for a convenient, fast, and inexpensive femur bone-implant scaffold with different lattice structures to mimic natural bone structure. Fused deposition modelling (FDM) was used to print a hybrid PEEK-based filament-bearing bioactive material suited for developing cHAp. Using FDM, the same bone scaffold PEEK will be fabricated, depending on the shape of the bone fracture. The scaffolds were examined for in vitro bioactivity by immersing them in a simulated bodily fluid (SBF) solution. Furthermore, in vitro cytotoxicity tests validated the suitability of the composite materials employed to create minimal toxicity of the scaffolds. After spreading PEEK nanoparticles in the grains, the suggested spherical nanoparticle cell expanded over time. The motif affected the microstructure of PEEK-cHAp in terms of grain size and 3D shape. The results established the proposed optimum design and suitable material for prospective bone implants, as required for biomimetic artificial bone regeneration and healing.Peer reviewe

Incidence and Risk Factors of Neural Tube Defects in Kashan, Central Iran

How to Cite This Article: Talebian A, Soltani B, Sehat M, Zahedi A, Noorian A, Talebian M. Incidence and Risk Factors of Neural Tube Defects in Kashan, Central Iran. Iran J Child Neurol. Summer 2015;9(3):50-56.AbstractObjectiveNeural tube defects (NTDs) are the most common congenital defects of centralnervous system due to neural tube closure deficit during the third and fourthweeks of gestational age. Our study was performed to detect the incidence andrisk factors of NTDs in Kashan, center of Iran.Material & MethodsThis case-control study was done on all pregnancies with NTD affectedneonates (n=91) and 209 pregnancies with normal neonates from February2007 to December 2012 in three hospitals in Kashan, center of Iran. Annual andthe mean incidence of NTDs were calculated. Risk factors including neonatalgender, maternal age, gravidity, maternal abortion history, maternal gestationaldiabetes (GDM), folic acid use, familial marriage, maternal body mass index(BMI), birth season and family history of NTDs were evaluated by interviewwith mothers. Univariate and multivariate logistic regression were used toanalyze the risk factors.ResultsThe mean incidence of NTDs was 2.33 per 1000 births. The multivariate analysisindicated that maternal history of abortion (OR: 4.9, CI: 1.9-12.8), and maternal obesity (OR: 5.4, CI: 1.3-21.8) were significantly associated with NTDs.ConclusionMaternal history of abortion and BMI were the major risk factors of NTDs

Critical assessment of the bonded single lap joint exposed to cyclic tensile loading

open access articleSingle shear or single lap joints are the most prevalent type of adhesive joints used in advanced engineering applications, where they are exposed to fatigue loadings in their services. Although their mechanical performances under static loading have been investigated extensively, the studies related to the fatigue performances were limited. For that purpose, single lap joint's (SLJ's) reaction to fatigue tensile loading was studied by varying the adherend thickness (3 mm to 6 mm) and fatigue load (3250 N to 1500 N). ABAQUS/Standard was used to create its advanced FE model. To represent the progressive damage in the adhesive layer, the fatigue damage model via the Paris Law, which links the rate of the crack expansion to the strain energy release rate (SERR), was integrated into the cohesive zone model having a bi-linear traction–separation characteristics. The model was written in a UMAT subroutine. The developed model was vali-dated using experimental data from the literature. The crack initiation cycle (Ni), the failure cycle (Nf), the fatigue load limit, the strain energy release rate, the crack propagation rate, and varia-tion of stress components with their dependency to design parameters were investigated in depth. It was found that the service life of the SLJs with thicker adherends was more responsive to the amount of stress applied. When exposed to lesser loads, the SLJs' life span changed more noticeably

Application of smooth-particle hydrodynamics in metal machining

The finite element (FE) method has been extensively used to model complex cutting processes. However, due to large strains in a process zone, leading to increased element distortions, such simulations are confronted with numerical difficulties. Smooth-particle hydrodynamics (SPH) is a mesh-free computational method, which has been used to simulate multi-body problems. In this paper we present a 3D hybrid modelling approach for orthogonal micro-machining of a copper single crystal with the use of SPH and continuum FE. The model is implemented in a commercial FE software ABAQUS/Explicit. The study is used to gain insight into the effects of crystallographic anisotropy on the machining response of f.c.c. cubic metals

Microstructural Evaluation of Aluminium Alloy A365 T6 in Machining Operation

The optimum cutting parameters such as cutting depth, feed rate, cutting speed and magnitude of the cutting force for A356 T6 was determined concerning the microstructural detail of the material. Novel test analyses were carried out, which include mechanical evaluation of the materials for density, glass transition temperature, tensile and compression stress, frequency analysis and optimisation as well as the functional analytic behaviour of the samples. The further analytical structure of the particle was performed, evaluating the surface luminance structure and the profile structure. The cross-sectional filter profile of the sample was extracted, and analyses of Firestone curve for the Gaussian filter checking the roughness and waviness profile of the structure on aluminium alloy A356T6 is proposed. A load cell dynamometer was used to measure different parameters with the combination of a conditioning signal system, a data acquisition system and a computer with visualised software. This allowed recording the variations of the main cutting force throughout the mechanised pieces under different cutting parameters. A carbide inserted tool with triangular geometry was used. The result shows that the lowest optimum cutting force is 71.123 N at 75 m/min cutting speed, 0.08 mm/rev feed rate and a 1.0 mm depth of cut. The maximum optimum cutting force for good surface finishing is 274.87 N which must be at a cutting speed of 40 m/min, 0.325 mm/rev feed rate and the same 1.0 mm depth of cut

A randomized clinical trial on the effect of honey in the acute gastroenteritis

Acute gastroenteritis is one of the hygienic challenges of the 21st century and one of the 6 major causes of death in children and adults in developed and developing countries. With respect to prevalence of this illness in Iran, the purpose of this study is to investigate the effectiveness of honey in treating diarrhea in Kashan, Iran. In this randomized clinical trial study, the participants were chosen from the children who were admitted to pediatric clinics. 150 children who met the criteria were divided into 3 groups. After a systematic treatment process and writing down the details, the first group received honey added to ORS (dissolved in ORS), the second group received honey separate from ORS and the control group received ORS with no honey. All the patients were under the close watch of the researchers until complete recovery. Then the data were analyzed with statistical tests and SPSS18 software. In general, among the 150 children who were studied there were 80 boys with the average age of 33.19 months and 70 girls with the average age of 29.84 months. The average diarrhea period from the beginning of treatment until complete recovery was 4.68 days for the first group, 3.725 for the second group and 5.60 for the control group. Thus there was a significant difference between the groups that received honey and the control group (p=0.001). The average number of bowel movements from the beginning of treatment until complete recovery was 4.22 for the first group, 3.50 for the second group and 4.90 for the control group. There was a significant difference in this respect (p<0.001). Generally, with regard to the findings of this study prescription of honey for diarrhea can reduce the number of bowel movements and diarrhea period. Similar studies could be done about other diseases to further investigate the effectiveness of honey in treating other health problems, not necessarily as a substitute treatment, but a supplementary treatment

Association between Rotavirus Infection and Irritable Bowel Syndrome: A Case-control Study in Kerman - Iran

Background: Irritable bowel syndrome is a functional gastrointestinal disease of unknown etiology. Researchers have recently drawn attention to the possible role of viruses in the development of IBS and provided evidence in this regard. In this study, it was decided to investigate the possible role of rotavirus infection in the onset of IBS.Methods: Stool and serum samples were collected from 40 patients with IBS and 40 healthy individuals. To evaluate the previous exposure to rotavirus we checked the presence and concentration of anti-rotavirus IgG by ELISA. ELISA test was performed on the serum samples. Real-time PCR test was also used to measure the viral load in the stool. Finally, the data were analyzed by SPSS-22 software.Results: No significant relationship was found between anti-rotavirus IgG presence and Level in the serum of case and healthy individuals (p-value > 0.05) . Moreover, there was no significant difference between the viral genome load in the stool samples of the two groups (p-value > 0.05).Conclusion: According to the results, it seems unlikely that a link exists between rotavirus infection and the onset of irritable bowel syndrome, but the possible role of other gastrointestinal viruses, including coronavirus, remains