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Purpose The current investigation aims at observing the influence of the cooling channel on the thermal and residual stress behavior of the selective laser melting (SLM)316L uni-layer thermo-mechanical model. Design/methodology/approach On a thermo-mechanical model with a cooling channel, the effect of scanning direction, parallel and perpendicular and scan spacing was simulated. The effect of underlying solid and powder bases was evaluated on residual stress profile and thermal variables at various locations. Findings The high heat dissipation of solid base due to high cooling rates and steep thermal gradients can reciprocate with smaller melt pool temperature and melt pool size. Given the same scan spacing, residual stresses were found lower when laser scanning was perpendicular to the cooling channel. Moreover, large scan spacing was found to increase residual stresses. Originality/value Cooling channels are increasingly being used in additive manufacturing; however, their effect on the residual stress behavior of the SLM component is not extensively studied. This research can serve as a foundation for further inquiries into the impact of base material design such as cooling channels on manufactured components using SLM.

High temperature gradients and resulting large residual stresses are among the most challenging areas of selective laser melting. In order to control these issues, proper understanding of the influence of process parameters on thermal as well as residual stress profile during selective laser melting is of paramount importance. Despite the large number of parametric investigations regarding stress profiles, a lot is yet to be understood especially for 316L stainless steel. Therefore, a 3D FEM model is established in this work to investigate the parametric influence on thermal and residual stress profile in a realistic multi-track multi-layer SLM process. Influences of process parameters on thermal and stress profile were investigated through the experimentally validated FEM model. It was observed that an increase in laser power or a decrease in the scanning speed results in an increased maximum melt pool temperature. Whereas, increasing laser power or scanning speed both increases cooling rates and residual stresses. An increased maximum melt pool temperature and decreased residual stress was observed by increasing the hatch spacing. Residual stress profile was observed to be symmetrical along the scanning direction and non-uniform along the direction perpendicular to the scanning direction. A relatively small residual stress at the top surface and maximum residual stress inside the component around the interface region of powder bed and baseplate was observed.

Rapid melting and solidification of powder particles through a high-power laser is the characteristic feature of selective laser melting (SLM), which controls the material and physical properties of fabricated components. Considering the multi-track multi-layer nature of an actual SLM process, an investigation of thermal behavior and melt pool morphology in multi-track multi-layer SLM of the 316L steel is presented in this paper. The SLM process of a four-layer component with multiple tracks was modeled. Element birth and death technique was used to simulate the layer built-up process. The established FEM model was used to investigate the variations in thermal variables and melt pool morphology with increasing number of layers. Moreover, the influence of various processing parameters in a multi-track multi-layer SLM was also studied. The results show that maximum melt pool temperature, melt pool width, and melt pool depth increase with increasing number of layers, whereas heating rates and cooling rates decrease with increasing number of layers. Compared with the previous layer, melt pool lifetime was observed to have a decreasing trend for layer 2 and increasing trend for layers 3 and 4. An increase in melt pool depth and decrease in melt pool width was observed by increasing hatch spacing. Furthermore, it was found that increasing laser power and scanning speeds both increase the heating and cooling rates.

Purpose This paper aims to investigate the influence of different post-annealing cooling conditions, i.e. furnace cooling (heat treatment (HT) 1 – slow cooling) and air cooling (HT 2 – fast cooling), on the microstructure and mechanical properties of selective laser melting (SLM) built austenitic 316L stainless steel (SS). Design/methodology/approach Three sets of 316L SS samples were fabricated using a machine standard scanning strategy. Each set consists of three tensile samples and a cubic sample for microstructural investigations. Two sets were subsequently subjected to annealing HT with different cooling conditions, i.e. HT 1 and HT 2, whereas one set was used in the as-built (AB) condition. The standard metallographic techniques of X-ray diffraction, scanning electron microscopy and electron back-scattered diffraction were used to investigate the microstructural variations induced by different cooling conditions. The resultant changes in mechanical properties were also investigated. Findings The phase change of SLM fabricated 316L was observed to be independent of the investigated cooling conditions and all samples consist of austenite phase only. Both HT 1 and HT 2 lead to dissolved characteristic melt pools of SLM. Noticeable increase in grain size of HT 1 and HT 2 samples was also observed. Compared with AB samples, the grain size of HT 1 and HT 2 was increased by 12.5% and 50%, respectively. A decreased hardness and strength, along with an increased ductility was also observed for HT 2 samples compared with HT 1 and AB samples. Originality/value From previous studies, it has been noticed that most investigations on HT of SLM fabricated 316L were mainly focused on the HT temperature or holding time. However, the post-HT cooling rate is also an equally important factor in deciding the microstructure and mechanical properties of heat-treated components. Therefore, this paper investigates the influence of different post-annealing cooling conditions on microstructure and mechanical properties of SLM fabricated 316L components. This study provides a foundation for considering the post-HT cooling rate as an influential parameter that controls the properties of heat-treated SLM components.

Large-scale construction 3D printing (C3DP), which is also known as green building construction is an innovative method that can save time, materials, and labor costs. The suitable printing materials should have the properties of good fluidity, excellent early strength, appropriate setting time, suitable viscosity, and cost-effectiveness. Among the main concerns of the construction 3D printing, the clogging of the material induced by premature setting and poor fluidity of the concrete is a significant one. It hinders the pumping capacity of concrete materials from the mixer to the extruder and reduces the overall efficiency of the C3DP process. The existing literature has proposed a variety of materials for C3DP, but there is still no standard information on the material selection. Therefore, it is necessary to solve the problem of material clogging while obtaining the above-mentioned characteristics suitable for printing materials. In the present study, the suitable printing properties for C3DP material were obtained to solve the clogging problem. The composition based on industrial solid waste was used to prepare this material. The use of this material in C3DP was proved to be cost-effective. Suitable setting time (33 min), good fluidity (181 mm), and excellent compressive strength (10.4 MPa and 78.2 MPa for 2 h and 28 days, respectively) were realized. These suitable properties were obtained by adding the phase change material (PCM) at different temperatures. In addition, due to the phase change characteristics, PCM has been proven to effectively solve the clogging problem of material. Furthermore, optimized material was used to print 3D structures with different shapes. We believe that this work can provide innovative ideas for the promotion of green building construction and the production of high-value products.

In past few decades, a lot of research has been done in the field of machining to improve the quality of machined surface. Out of these machining operations, drilling is widely used in the areas of marine and aerospace for assembly requirements. Titanium alloy Ti-6Al-4V, owing to its vast applications, is regarded as an important material for these industries. Ti-6Al-4V is categorized as difficult to machine material. Based on above stated facts, an experimental study was conducted on the dry drilling of Ti-6Al-4V. The objective of this study was to establish the correlations between drilling parameters such as feed rate and spindle speed, and quality of machined surface which is evaluated in terms of drill hole diameter deviation, exit burr height and surface roughness.

The present study aims to investigate the tool wear mechanism of TiAlN-/NbN-coated tungsten carbide insert during end milling of hard Ti alloy under cryogenic treatment at 24 h and 48 h. The output responses are examined by looking at the flank wear, tool wear mechanism, elemental composition analysis, cutting force and vibration acceleration signal. A 12–23% and 4–11% reduction in the flank wear was noted at 48-h and 24-h cryogenically treated inserts (CTI) when compared with untreated insert. The reduction in the cutting force and vibration was also observed in the CTI when compared with untreated insert. The results showed better machinability and enhanced tool life for CTI, which is better than untreated insert under the same set of working conditions.

Mayonnaise is a popular condiment containing 65–75% oil by weight. The aim of the study was to develop a low fat (75% fat-replaced) mayonnaise using chemically modified octenyl-succinic anhydride (OSA) corn and OSA-sorghum starches. Secondly, the functional properties of native and modified corn and sorghum starches were also compared. The setback viscosity of OSA-sorghum starch was found to be the least while the textural changes in OSA-sorghum on cold storage were found to be negligible. Overall acceptability of low fat mayonnaise (LFM) was scored higher than full-fat mayonnaise (FFM). But the textural attributes of LFM made from OSA-sorghum were found to be quite similar to FFM.

Brain computer interface (BCI) systems have ushered a new era of neural engineering research. At the core of BCIi research is development of data acquisition, filtration and classification techniques that can accurately decode the brain activity that occurs while performing a motor task. In this study, we investigate the classification accuracy of lda, QDA, Naive Bayes, quadratic SVM and RBF SVM classifiers for classifying the flexion/extension of forearm and wrist. Moreover, hjorth parameters and PSD are employed as feature extraction techniques to derive four different feature vectors that are later used to train our classifiers. At the culmination of this study, it is shown that QDA classifier trained with PSD feature vector has the highest classification accuracy at 77.37% followed by q-SVM trained with activity feature vector at 73.97%. Apart from enhancing accuracy of classifying the four fundamental upper limb movements, this study will eventually contribute towards developing better controllers for neuro-prosthetic devices. The study has been performed experimentally with Emotiv headsets equipped with 14 electrodes to acquire EEG data from two human test subjects in synchronous mode. Classification and data analysis has been performed offline however in future the study will be extended to an online BCI system.

The purpose of this research is to find out the impact of dividend payments on the earnings of companies listed on Pakistan Stock Exchange. The sample includes firm listed on the Karachi Stock Exchange 100 index for a time period of 2005-2015. The model was applied where they refuted the conventional theory that said dividend payments do not affect future earnings of the company, on the aggregate U.S. Market (S&P 500). Our variables include size, return of asset, payout ratio, leverage taken by the company, earnings over price, past earnings growth, exchange rate and annual growth. This study holds importance in respect to finding out whether our results will vary after applying the model studied in the developed economy or it holds same results in the developing economies. One important insight that we aim to find out is whether companies, in order to maximize shareholder’s wealth, should pay dividend or retain it back for further reinvestments.

The purpose of the study is to evaluate the service Quality parameters of online banking that determine customer's usage behavior, hence the association among Perceived Risk, Privacy & Security and Perceived Trust on customers' attitude was studied that further influences customers' intention towards usage of online banking in Pakistan. A cross sectional study was conducted, where the questionnaires were distributed among 250 users of online banking of public and private banks. Respondents were selected using random sampling technique, who was students and employees of different universities and organizations. The study suggested that service Quality plays a vital role in determining users' actual usage behavior. It was further suggested that longitudinal study should be conducted in order to view the change in their behavior with the raise in experience and ease of use. Moreover individuals' personalities should be taken as a moderating variable to evaluate the impact of personality on technology acceptance.