Mechanical and Tibological Properties of SLM AlSi10Mg Alloy Subjected to ECAP

In this study, selectively laser melted AlSi10Mg alloy was subjected to ECAP processing for the first time. Mechanical properties of the ECAP processed samples were compared based on hardness measurement, compression and wear tests. The results showed exceptional synergy of high yield strength ~382 MPa and strain to failure of ~48% of the SLM ECAP processed sample. This sample also offered approximately ~71% higher wear resistance, than an unprocessed one. The proposed novel route expands the opportunities of both technologies to produce materials with exceptional properties.

A proposed method of sample preparation and homogenization of hemp for the molecular analysis of cannabinoids

The use of Cannabis sativa, or Hemp, in commercial, recreational, and pharmacological applications is on the rise in the United States and worldwide. Many of these applications have guidelines associated with them dependent on the concentration of cannabinoid molecules that keep the products classified as hemp versus marijuana or that allow the producer to comment on the purity and potency of their product. Herein, we propose a method for homogenization of hemp that results in small particle sizes, uniform samples, and does not alter the cannabinoid concentrations during processing, allowing for optimal and reproducible potency testing. Using a novel “active grinding media” we homogenized commercially available hemp to analyze approximately 100 mg samples of homogenate via sieve analysis and high-performance liquid chromatography to assess the resulting size and potency of the sample when using this methodology. When processing hemp samples with our proposed methodology, we have demonstrated the ability to produce 60.2% of all particles < 1.25 mm with increased cannabinoid recovery compared to homogenates with larger average particle sizes. Maintaining sample temperatures below 35 °C during processing, we showed that our method does not thermally induce decarboxylation reactions that would result in major cannabinoid profile changes. We have developed a method for hemp processing via homogenization that does not alter the cannabinoid profile during processing, while consistently producing small particle sizes in a uniformly processed sample. This method allows for optimal and reproducible hemp processing when evaluating hemp and hemp-based products being brought to commercial markets.

O-150 Predicting the sperm retrieval of microsurgical testicular sperm extraction (mTESE) in infertile men with azoospermia on the day of TESE-ICSI

Study question Is the sperm retrieval rate of a small, pre-processed sample (PPS) of each TESE-biopsy representative for the sperm outcome on the day of ICSI? Summary answer The analysis of a PPS reliably reflects the probability of finding comparable numbers of sperm at time of TESE-ICSI. What is known already Azoospermia is defined as a condition where no spermatozoa are found in the ejaculate and is diagnosed in up to 15% among infertile men and in 11% of all patients attending our centre. The combination of testicular sperm extraction (TESE) and intracytoplasmic sperm injection (ICSI) has become the standard treatment of azoospermic patients. However, no validated standard procedure has been identified to predict the exact sperm outcome of the cryopreserved TESE samples prior to TESE-ICSI so far. For optimal management of TESE-biopsies and the respective ICSI treatment, we developed a stepwise approach for the analysis of tissue samples. Study design, size, duration We retrospectively analysed the outcome of 872 microsurgically retrieved testicular biopsies of 198 patients of legal age who had a TESE-ICSI at our department between 2009 and 2019. From all 872 mTESE biopsies the number of sperm extracted from a small, pre-processed sample (PPS) before freezing procedure were known. The PPS was then compared to the number of sperm retrieved from the corresponding thawed specimen on the day of TESE-ICSI. Participants/materials, setting, methods During micro-TESE eight samples per testis are retrieved, then 1/10 of each biopsy is removed, digested with collagenase and screened for spermatozoa (pre-processed sample, PPS). If less than 100 spermatozoa are detected the absolute sperm number is recorded, otherwise the result is displayed as the maximum value of 100 sperm. On the day of ICSI, one or more TESE biopsies are thawed and processed for TESE-ICSI; the absolute sperm number is counted again. Main results and the role of chance Comparing the sperm yield of 872 TESE samples at time of ICSI to its respective PPS showed a similar sperm outcome with a minor deviation of ± 5 spermatozoa in 73.6% of all biopsies. However, 12.9% of the specimen had less and 13.4% had more spermatozoa. A negative sperm retrieval in the initial PPS was confirmed in 93.1% (268/288). PPS with 1-4 spermatozoa had a 27.2% (43/158) risk of complete absence of sperm on the day of ICSI, yet sperm detection (≥1 sperm) was positive in 72.8% (115/158) of the biopsies. With initially ≥5 spermatozoa present in the PPS, only 0.9% (4/426) of the biopsies had no sperm on the day of ICSI, vice versa 99.1% (422/426) were spermatozoa positive. A significant (p = 0.01) and strong (rs = 0.926) correlation of the sperm retrieval rates of the PPS and the ICSI sample was found meaning that the PPS reflects very well the sperm retrieval rate of the cryopreserved mTESE biopsy thawed at time of TESE-ICSI. However, if ≤ 4 sperm are found in the PPS, there is a relevant risk for a negative sperm retrieval on the day of ICSI and the couple should be carefully advised before start of treatment. Limitations, reasons for caution This analysis focussed on sperm prediction in cases of severe male factor infertility and therefore the sperm yield on the day of ICSI was chosen as primary outcome. The reproductive competence of the retrieved sperm in terms of pregnancy and birth rates should be subject to further investigation. Wider implications of the findings Treatment options for azoospermic patients are mostly related to the ability to find sperm on the day of ICSI. However, validated standards for sperm processing are missing. Therefore, a PPS seems to be a good option for prediction of sperm retrieval and improves counselling of the patients prior to TESE-ICSI. Trial registration number not applicable

Study on the effect of the welding environment on the dynamic recrystallization phenomenon and residual stresses during the friction stir welding process of aluminum alloy

Various methods have been proposed to modify the friction stir welding. Friction stir vibration welding and underwater friction stir welding are two variants of this technique. In friction stir vibration welding, the adjoining workpieces are vibrated normal to the joint line while friction stir welding is carried out, while in underwater friction stir welding the friction stir welding process is performed underwater. The effects of these modified versions of friction stir welding on the microstructure and mechanical characteristics of AA6061-T6 aluminum alloy welded joints are analyzed and compared with the joints fabricated by conventional friction stir welding. The results indicate that grain size decreases from about 57 μm for friction stir welding to around 34 μm for friction stir vibration welding and about 23 μm for underwater friction stir welding. The results also confirm the evolution of Mg2Si precipitates during all processes. Friction stir vibration welding and underwater friction stir welding processes can effectively decrease the size and interparticle distance of precipitates. The strength and ductility of underwater friction stir welding and friction stir vibration welding processed samples are higher than those of the friction stir welding processed sample, and the highest strength and ductility are obtained for underwater friction stir welding processed samples. The underwater friction stir welding and friction stir vibration welding processed samples exhibit about 25% and 10% higher tensile strength compared to the friction stir welding processed sample, respectively. The results also indicate that higher compressive residual stresses are developed as underwater friction stir welding and friction stir vibration welding are applied.

An Experimental Study on the Effect of Reverse Two-Step Sintering on Aluminium-Silicon Carbide Metal Matrix Composite

Aluminum (Al) - Silicon Carbide (SiC) metal matrix composite is one of the widely used composites in today’s manufacturing industry. Al-SiC composites are produced through several methods such as casting and powder metallurgy, but its production through Reverse Two-Step Sintering (R-TSS) process in powder metallurgy has not been addressed so far. The present work focuses on manufacturing Al-SiC metal matrix composite through reverse two-step sintering process in powder metallurgy. The reinforcement element SiC is embedded with metal matrix element Al in different proportions. Then the consolidated mixture is compacted using the die and punch setup followed by a two-step sintering process suggested by Wong; thereby, the final compact is produced. Further, the processed sample is analyzed for density and hardness tests.

The influence of new severe plastic deformation on microstructure, mechanical and corrosion properties of Mg-0.8Mn-0.5Ca alloy

In this research, the effect of accumulative extrusion bonding (AEB) on the microstructure and mechanical properties of Mg-0.8Mn-0.5Ca biocompatible alloy was investigated. The goal of this research was to develop the mechanical and corrosion properties of Mg-0.8Mn-0.5Ca alloy after ABE process as a novel severe plastic deformation process. The simulation of AEB process showed that the average effective strain per pass for channels with the internal angle of 120? is about 1.93. The average grain size was dramatically decreased from about 448.3 ?m for the homogenized alloy to 1.55 ?m for the 3-pass processed sample. Microstructural observations suggested a combination of continuous, discontinuous and twinning-induced dynamic recrystallization as the major mechanisms of grain refinement. Tensile and compressive strengths were improved from 150 and 205 MPa to 330 and 301 MPa after three passes of AEB, respectively indicating 2 and 1.5 times improvements, respectively. Tensile elongation decreased from 26 % for the homogenized sample to 7.5 % for the 3-pass processed sample due to the severe work-hardening, non-uniform strains and inhomogeneous microstructure produced by ABE process. Corrosion resistance in SBF solution was improved from 1.1 to 14.159 K? Cm2 after three passes of ABE due to the presence of hydroxyapatite formed on the surface of the AEBed samples.

Formability behavior of friction stir processed dual phase steel

This study investigated the formability behavior of dual-phase (DP) steel subjected to friction stir process (FSP), using a miniaturized Erichsen test. The friction stir process yielded a refined microstructure, which consisted of lath martensite and fine ferrite, as a result of dynamic recrystallization (DRX) and phase transformation. Both yield and tensile strength were significantly increased via the grain refinement and increasing martensite fraction. Biaxial formability behavior of the friction stir processed sample exhibited a decline as the Erichsen index (EI) decreased from 2.7 mm to 2.2 mm. However, the required punch load (FEI) increased compatibly with the strength value after FSP. The grain refinement caused by FSP led to an improvement in the orange peel effect, defined as a negative effect of increased surface roughness after metal forming. The value of mean roughness in the free dome surface of the FSPed sample decreased from 4.90 μm to 2.62 μm. It can be concluded that the roughening with the orange peel effect on free surfaces of stretched metal can be eliminated by the friction stir process.

DWT Based Energy Detection Spectrum Sensing Method for Cognitive Radio System

In this paper a new blind energy detection spectrum-sensing method based on Discreet Wavelet Transform (DWT) is proposed. The method utilizes the DWT sub-band to collects the received energy. The proposed method recognizes the Primary User (PU) signal from noise only signal using the differences in the collected energy in first and last sub-bands of one level DWT. The simulation results show that the proposed method achieves improved detection probability especially at low Signal to Noise Ratio (SNR) compared to Conventional Energy Detector (CED). The results also show that the proposed method has shorter sensing time and less Energy Consumption (EC) compared to CED due to using small number of processed sample. Therefore, this method is suitable for Cognitive Radio (CR) applications where only limited energy like device battery is available.

Effect of Multiple Passes on Microstructural and Mechanical Properties of Surface Composite Al 2024/SiC Produced by Friction Stir Processing

The application range in defense, aerospace and automotive sectors have enabled aluminium metal matrix composites to emerge in different technological fields due to enhanced micro structural and mechanical characteristics. In the present study, friction stir processing is used to fabricate Al2024/SiC composite with one, two and three passes of the cylindrical tool. Optical microscopy and scanning electronic microscope (SEM) were used to validate the processed sample and to justify the morphological aspects. Energy dispersive spectroscopy (EDS) analysis has also performed to confirm the presence of SiC particles in the composite. It also includes the analysis of mechanical properties such as tensile strength, Rockwell hardness test and nanoindentation to characterize the prepared samples. Improvement in tensile strength with a maximum of 443 MPa, the hardness of 121 HRB and nanoindentation of the specimen was depicted through the mechanical tests.

A Proposed Method of Sample Preparation and Homogenization of Hemp for the Molecular Analysis of Cannabinoids

BackgroundThe use of Cannabis sativa, or hemp, in commercial, recreational, and pharmacological applications is on the rise in the United States and worldwide. Many of these applications have guidelines associated with them dependent on the concentration of cannabinoid molecules that keep the products classified as hemp versus marijuana or that allow the producer to comment on the purity and potency of their product. Herein, we propose a method for homogenization of hemp that results in small particle sizes, uniform samples, and does not alter the cannabinoid concentrations during processing, allowing for optimal and reproducible potency testing. MethodsUsing a novel “active grinding media” we homogenized commercially available hemp to analyze approximately 100mg samples of homogenate via sieve analysis and high-performance liquid chromatography to assess the resulting size and potency of the sample when using this methodology. ResultsWhen processing hemp samples with our proposed methodology, we have demonstrated the ability to produce 60.2% of all particles <1.25 mm with increased cannabinoid recovery compared to homogenates with larger average particle sizes. Maintaining sample temperatures below 35° C during processing, we showed that our method does not thermally induce decarboxylation reactions that would result in major cannabinoid profile changes.ConclusionWe have developed a method for hemp processing via homogenization that does not alter the cannabinoid profile during processing, while consistently producing small particle sizes in a uniformly processed sample. This method allows for optimal and reproducible hemp processing when evaluating hemp and hemp-based products being brought to commercial markets.