On the use of temperature dependences of the coercive force for an analysis of structural and phase changes that occur upon tempering of alloy carbon steels

The effect of alloying elements Mn, Cr, and Si on the magnetic hysteresis properties of cementite and model steels with a carbon concentration of 0.6 wt % has been studied. It has been shown that alloying with carbide-forming elements (Mn, Cr) reduces the coercive force and the Curie temperature of cementite. Measurements of the temperature dependences of the coercive force of the model steels with carbon content of 0.6 wt % alloyed with manganese, chromium, or silicon have been performed in the temperature range of ?196 to +300°C. It has been established that the local maximum of the coercive force of these steels in this temperature range coincides with the Curie point of the precipitates of the carbide phases. Based on an analysis of the temperature dependences of the coercive force, the content of the alloying element in the precipitates of cementite of steels tempered at different temperatures has been estimated. It has been shown that the character of the dependence of the coercive force of alloy steels on the temperature of tempering in the temperature range of 250–700°C is mainly determined by the coercivity and by the kinetics of the formation of cementite precipitates.     

Development of a virtual machining system, part 3: cutting process simulation in transient cuts

In Parts 1 and 2 of this three-part paper, a mechanistic cutting force model was developed and machined surface errors for steady cuts under fixed cutting conditions were predicted. The virtual machining system aims to simulate and analyze the machining and the machined states in a general flat end-milling process. This frequently involves transient as well as steady cuts. Therefore, a method for simulating the cutting process of transient cuts needs to be developed to realize the virtual machining system concept. For this purpose, this paper presents a moving edge-node (ME) Z-map model for the cutting configuration calculation. The simulation results of four representative transient cuts in two-dimensional pocket milling and an application of off-line feed-rate scheduling are also given.

In transient cuts, the cutting configurations that are used to predict the cutting force vary during the machining operation. The cutting force model (Part 1) and surface error prediction method (Part 2) were developed for steady cuts; these are extended to transient situations using the ME Z-map model to calculate the varying cutting configurations efficiently. The cutting force and surface errors are then predicted. To validate the feasibility of the proposed scheme, the measured and predicted cutting forces for transient test cuts were compared. The predicted surface error maps for transient cuts were constructed using a computer simulation. Also, off-line feed-rate scheduling is shown to be more accurately performed by applying the instantaneous cutting coefficients that were defined in Part I.     

The Effect of Different Plasticizers on Lactose Crystallization During Spray Drying

Lactose crystallization may occur during spray drying, depending on the operating conditions for drying, and this work reviews previous and new evidence for the effects of different additives or plasticizers on retarding or accelerating the rate of crystallization. The effects of different operating conditions during spray drying are also considered in the experimental work reviewed and performed here, which was mainly carried out with Buchi B-290 laboratory-scale spray dryers (Buchi, Flawil, Switzerland), although some work on pilot-scale equipment is also discussed. The additives used and reviewed in this article include milk proteins, such as casein and whey protein isolate, polyethylene glycol, and ascorbic acid. The key physical properties, such as glass transition temperature and drying characteristics of the material, are discussed, allowing degrees of amorphicity in spray-dried lactose to be controlled over a wide range, from close to 0% to nearly 100%.     

Monovalent cation perm-selective membranes (MCPMs):New developments and perspectives

As one of the most typical and promising membrane processes, electrodialysis (ED) technique plays a more and more significant role in industrial separation. Especially, the separation of monovalent cations and multivalent cations is currently a hot topic, which is not only desirable for many industries but also challenging for academic explorations. The main aim of the present contribution is to view the advances of a wide variety of monovalent cation perm-selective membranes (MCPMs) and their preparation technologies including (1) covalent crosslinking,(2) surface modification, (3) polymer blending, (4) electrospinning, (5) nanofiltration alike membrane, and (6) organic–inorganic hybrid. The relevant advantages and disadvantageswith respect to some specific cases have been discussed and compared in detail. Furthermore, we elaborately discuss the opportunities and challenges of MCPMs, the fabricating strategies to take and the future perspectives.     

Bulk and surface mechanical properties of clay modified HDPE used in liner applications

High‐density polyethylene (HDPE)/clay nanocomposites were prepared by melt blending process. The HDPE was mixed with different organoclays and polyethylene‐grafted‐maleic anhydride was used as a compatibiliser. A masterbatch procedure was used to obtain final organoclays concentrations of 1, 2.5 and 5 wt%. The effects of various types of nanoclays and their concentrations on morphological, thermal and mechanical properties of nanocomposites were investigated. Surface mechanical properties such as instrumented nanohardness, modulus of elasticity and creep were also measured using a nanoindentation technique. Young's, storage and loss moduli, were found to be higher than that of the neat polymer at low loading (2.5 wt%) for clay Cloisite 15A and at higher loading (5 wt%) for clay Nanomer 1.44P. The ultimate strength and the toughness decreased slightly compared to pure HDPE. The differential scanning calorimetry analysis revealed that the peak temperature of the nanocomposites increased with increased clay content while the crystallinity decreased. Also, dynamic mechanical analysis revealed the storage and loss moduli are enhanced by addition of nanoclay. Both mechanical and thermal properties of HDPE/Nanomer 1.44P nanocomposite showed interesting trends. All properties first dropped when 1 wt% of the clay was added. Thereafter, a gradual increase or decrease then followed as the loading of Nanomer was increased. These trends were observed for all mechanical properties. The results obtained from nanoindentation tests for surface mechanical properties also showed similar trend to that of bulk measurements. Based on these measurements a nanoclay additive for a liner grade HDPE was selected. © 2011 Canadian Society for Chemical Engineering     

Compatibilization and Properties of EVA Copolymers Containing Surface‐Functionalized Cellulose Microfibers

Cellulose microfibers were modified with two different bi‐functional monomers. Composites of EVA copolymer with modified and unmodified cellulose were prepared by melt mixing. The samples were analyzed by SEM, XRD, FT‐IR, DSC, TGA, DMTA and tensile mechanical tests. SEM showed that the presence of reactive groups on cellulose surface enhanced the compatibility, improving the fiber/matrix interfacial adhesion. FT‐IR disclosed the occurrence of chemical reactions between the functionalized cellulose and polymer chains. The incorporation of fibers affected the crystallization behaviour and crystallinity of the polymer matrix. Composites with GMA modified cellulose displayed better compatibility, higher thermal and mechanical properties.

     

Fabrication of a functionally graded and magnetically responsive shape memory polymer using a 3D printing technique and its characterization

In this study, a three‐dimensional printing technique is applied for the fabrication of novel functionally graded magnetic shape memory polymers (SMPs) to create high‐resolution multimaterial shape memory architectures. This approach is applied to a copolymer network of photocurable methacrylate using high projection stereolithography. Carbonyl iron particles (CIPs) were physically embedded in a polymer matrix to add magnetic functions to the SMPs. The glass transition characteristics and shape memory effect were also investigated by varying the composition of the SMP. The microstructured, lightweight SMPs showed interesting shape memory behaviors, as observed in hot environment. The almost perfect strain recovery rate of poly(ethylene glycol) dimethacrylate was measured (99.95% using a tension set bar). The results of dynamic mechanical analysis and thermogravimetric analysis reveal an increment in the thermal conductivity after embedding the CIPs. Further, the results of dynamic mechanical analysis, differential scanning calorimetry, and scanning electron microscopy reveal close interaction between the particles and matrix. X‐ray diffraction was used to characterize the iron particles and polymer structure. These results, along with the electrical and magnetic tests, strongly support the remote controllability of the material properties of the present functionally graded magnetic SMPs for a broad range of temperature and/or magnetically responsive material applications by using eddy current heating and/or magnetorheological polymeric effects. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45997.     

Sintering study of injection molded W-8%Ni-2%Cu compacts from mixed powders by thermoanalytical techniques

Heavy alloy parts from W-8%Ni-2%Cu powder mix were fabricated by MIM using a feedstock with 50 vol.% binder. The binder was removed by solvent de-binding followed by thermal de-binding. Sintering of the heavy alloy brown parts was investigated by employing various thermoanalytical techniques such as DIL, TGA and DTA up to 1460 °C. During sintering, the evolved gases were analyzed in a mass spectrometer which was coupled to the dilatometer. Thermal analysis helps to understand the sintering process regarding phase transformation, melting of alloy matrix and chemical reactions. From these thermoanalytical measurements, a kinetic analysis was made. High sintered density (> 99%) and fine-grained homogeneous microstructures were achieved by rate controlled sintering as confirmed by metallographic analysis.     

An air crash due to fatigue failure of a ball bearing

The failure analysis of an air crash conclusively shows that the cage of the central main bearing of the compressor region failed due to fatigue. The broken piece of the cage got struck between the bearing balls and the races and impaired the function of the bearing resulting in the crash.