Mechanical Properties Of Parts Research Articles

Influence of Mold Temperature on Mold Filling Behavior and Part Properties in Micro Injection Molding

Abstract A variety of polymer parts used in microsystems technology is manufactured by injection molding processes. Particularly the high cooling velocity negatively affects the process and the resulting part properties. The scope of this paper is to investigate the influence of the mold temperature during the injection phase on the melt flow and the mold filling as well as on the resulting part properties. The results indicate that an increasing mold temperature supports the filling behavior, although the injection pressure has more impact. An increasing mold temperature also influences the part properties. It was found that a higher mold temperature leads to a more homogeneous and spherulitic structure as well as to an increasing degree of crystallinity. As a consequence the mechanical part properties are affected, too.

Experimental Analysis of Hardness Distribution of the Transition Region in Tailored Tempering Stamping of Ultra-High Strength Steel

With hot forming parts of ultra-high strength steel (UHSS) widely used, requirements on matching the mechanical properties of parts with the performance on active service are attracting attention. Research shows that the preheat temperature of the molds set to 400°C or above can effectively reduce the hardness of the sheet and get a better region. The width of the air gap between tools is important influencing factor. Too large air gap will increase the difficulty of controlling the region of variable intensity and the position of ultimate strength.

ВЛИЯНИЕ ТЕРМИЧЕСКОЙ ОБРАБОТКИНА ИЗМЕНЕНИЕ МЕХАНИЧЕСКИХ СВОЙСТВ МЕТАЛЛОКЕРАМИЧЕСКОЙ КОМПОЗИЦИИ НА ОСНОВЕ ЖЕЛЕЗА

In this paper, the authors study the influence of the drawback temperature of metal-ceramics composites on their mechanical properties, if composites are produced using the iron-graphite powder method. The authors have studied the microstructure of the materials and the influence that the thermal treatment produces on their strength, plastic properties and toughness. The authors have also identified specific thermal treatment parameters aimed at the improvement of mechanical properties of parts of machines and mechanisms made of the above composites. The analysis of the authors’ findings is applied to find the ways of improving the mechanical properties of machine parts produced using powder metallurgy methods. The analysis of the microstructure confirms the presence of changes in the mechanical properties of materials, namely, their plastic properties and toughness. The combination of the most efficient sintering regime (using double pre-pressing) and subsequent thermal treatment in the form of hardening and tempering can improve the mechanical properties of machine parts. The authors performed experiments to identify the best sintering conditions and improve the mechanical properties of the Fe-C composition, including its tensile and flexural strength, as well as compressive and impact strength using the above process parameters and other data obtained from the reference literature. The authors have discovered that if the sintering speed and the shrinkage ratio are maximal and vary insignificantly at the temperature near the Ac3 value and slightly above it, the mechanical properties after sintering, for example, at 870 °C and 1100°C will differ slightly.

Tribological performance of DLC coatings deposited by ion beam deposition under dry friction and oil lubricated conditions

Understanding the reaction between lubricant additives and diamond-like carbon coatings is imperative for the improvement of the friction and wear properties of mechanical parts with diamond-like carbon coatings. Diamond-like carbon coatings were deposited with ion beam deposition and the influence of lubricant additives on the friction coefficients and wear rates of diamond-like carbon coatings under the lubricated conditions was studied. It was revealed that the wear rates of diamond-like carbon coatings under unlubricated conditions are 1.5 × 10−14 m3/(Nm) while they are decreased to 3 × 10−17 m3/(Nm) to 1.7 × 10−16 m3/(Nm) when lubricated by PAO-4 base oil with three additives. The addition of molybdenum dithiocarbamate in PAO-4 base oil decreases the friction coefficients of diamond-like carbon coatings to 0.07, but increases the wear rate of diamond-like carbon coatings. The addition of zinc dialkyl dithiophosphate to PAO-4 can slightly decrease the friction coefficient of diamond-like carbon coatings and improve the wear resistance of diamond-like carbon coatings. The addition of amine sulfuric-phosphate diester in PAO-4 can greatly decrease the wear rate of diamond-like carbon coatings to 3 × 10−17 m3/(Nm) but has a negligible effect on the friction coefficients of diamond-like carbon coatings.

Austenite Grain Growth Behavior of AISI 4140 Alloy Steel

AISI 4140 alloy steel is widely applied in the manufacture of various parts such as gears, rams, and spindles due to its good performance of strength, toughness, and wear resistance. The former researches most focused on its deformation and recrystallization behaviors under high temperature. However, the evolution laws of austenite grain growth were rarely studied. This behavior also plays an important role in the mechanical properties of parts made of this steel. In this study, samples are heated to a certain temperature of 1073 K, 1173 K, 1273 K, and 1373 K at a heating rate of 5 K per second and hold for different times of 0 s, 120 s, 240 s, 360 s, and 480 s before being quenched with water. The experimental results suggest that the austenite grains enlarge with increasing temperature and holding time. A mathematical model and an application developed in Matlab environment are established on the basis of previous works and experimental results to predict austenite grains size in hot deformation processes. The predicted results are in good agreement with experimental results which indicates that the model and the application are reliable.

Experimental Characterization of Heat Transfer Coefficients During Hot Forming Die Quenching of Boron Steel

The heat transfer coefficient (HTC) between the sheet metal and the cold tool is required to predict the final microstructure and mechanical properties of parts manufactured via hot forming die quenching. Temperature data obtained from hot stamping experiments conducted on boron steel blanks were processed using an inverse heat conduction algorithm to calculate heat fluxes and temperatures at the blank/die interface. The effect of the thermocouple response time on the calculated heat flux was compensated by minimizing the heat imbalance between the blank and the die. Peak HTCs obtained at the end of the stamping phase match steady-state model predictions. At higher blank temperatures, the time-dependent deformation of contact asperities is associated with a transient regime in which calculated HTCs are a function of the initial stamping temperature.

Research on the Tribological Properties of Ni-W Alloy Electric Brush Plating Coatings at Elevated Temperatures

In order to improve the anti-wear and anti-corrosion properties of mechanical parts used in high temperature friction conditions, the Ni-W alloy brush plating coatings were prepared and their tribological properties at elevated environment temperatures were investigated. The results show that the friction coefficients of Ni-W/GCr15 tribo-couples are in the range of 0.168～1.048, which take on the decreasing trend as the increase of environment temperatures. The wear losses of the coatings increase at elevated temperatures, and the critical temperature in which the coatings produce serious wear from slight wear is 250°C. The wear mechanism of the coatings are micro-cutting at room temperature, then it changes into adhesive wear accompanied by a certain of delamination when temperature is high than 250°C. When temperature is higher than 400°C, the main wear mechanism of the coatings is adhesive wear and delamination.

Laser intensity effect on mechanical properties of wood–plastic composite parts fabricated by selective laser sintering

In this article, the relationship between the mechanical properties of wood–plastic composite (WPC) parts fabricated by selective laser sintering (SLS) and the laser intensity is determined. Green parts were formed from WPC by SLS process, the SLS green parts had sufficient strengths for features to be built with relatively high dimensional accuracy. In order to improve the mechanical properties of the parts to better level, the post-processing – infiltration with wax – is used. Experiments for studying mechanical properties of WPC parts with laser intensity growing are carried on, the result is as following: because interfacial adhesion of copolyester and densification are improved with laser intensity growing, impact strength increased gradually either in green part style or in wax-infiltrated part style, tensile strength and bending strength of wax-infiltrated parts increased gradually. The tensile strength improved 191% and the bending strength improved 17%, with the increase in laser intensity from 226 Watt/mm2 to 311 Watt/mm2; the impact strength of green parts improved 543% and the impact strength of wax-infiltrated parts improved 147%, respectively, by increasing the laser intensity from 226 Watt/mm2 to 340 Watt/mm2. But when the laser intensity is greater than 311 Watt/mm2, the tensile strength and bending strength decreased for further increasing of the laser intensity, leading to higher temperature, making the melt viscosity of the copolyester drop.

Fabricate Mould Insert with Conformal Cooling Channel Using Selective Laser Melting

Selective Laser Melting (SLM) technology can be used to fabricate plastic mould with complex conformal cooling channels directly and rapidly. In this paper, 316L stainless steel powders were used to produced a mould with an emphasis on attaining excellent mechanical properties.The precision, density and mechanical properties of parts were studied. Simulation and experimental results showed: the mould manufactured by SLM reveals good accuracy and performance, and the cooling efficiency of conformal cooling channels in mould has been greatly improved and the uniformity of cooling has been also upgraded.

Investigation of Dimensional Accuracy/Mechanical Properties of Part Produced by Selective Laser Sintering

Selective laser sintering (SLS) process has the potential to become one of the most useful additive manufacturing techniques in coming few years, because it has potential to easily produced complex shapes. Use of this process becomes more extensive, with the main advantages being a wide range of build materials available. So SLS can accommodate multiple applications throughout the manufacture process. It comes early with three main applications: conceptual models, functional prototypes, and pattern masters. Since then they have been added with an extra module, which incorporates rapid tooling. Only disadvantage of SLS process that it is both time consuming and expensive when a new material comes into use. In this paper we will investigate the effect of part placement (X and Y direction) in the build on the dimensional accuracy and mechanical properties of part produced by this SLS process.

Development of a Simulation-Based Process Chain – Strategy for Different Levels of Detail for the Preprocessing Definitions

Additive manufacturing processes fulfill the ac- tual market demands with regard to a high individuality and complexity of products. Hence, these processes are used nowadays in different branches (e. g. aerospace, automotive, medical industry). Further-more, a high pro- cess stability and reproducibility is requested by the user for an eco-nomic application of this technology. Up to now, these targets are reached by numer-ous test rigs on the manufacturing system which causes high resource consumption. For increasing the efficiency of metal-based additive man- ufacturing (AM), the em-ployees of the iwb application center Augsburg in corporation with the CADFEM GmbH and four further partners develops a simulation-based process chain (founded by the Bavarian Research Founda- tion). Before the production process is started, an analysis of the structural part behavior as well as a process optimi- zation should be per-formed using the finite element analysis (FEA). Due to the complexity of the thermal-ly activated process, it is necessary to select the appropriate FE-modeling strategy for enhancing the target figures calculation efficiency and accuracy. Hence, in this work a strategy will be presented, which can map different levels of detail for the preprocess-ing definitions. These local and global descriptions can be realized by using suitable con- tact definitions (contact elements) to link different ele- ment meshes. Additionally, the user can select different layers of the part geometry, which should be analyzed in detail within the simulation. Also layer-specific distortions and residual stresses can be calculated while saving calcu- lation time. Furthermore, with this approach the process history and therefore the whole part geometry can be considered in the structural cal-culations. A validation of the transient temperature field and the mechanical part properties is presented by the comparison with measured values.

Studying the influence of initial powder characteristics on the properties of final parts manufactured by the selective laser melting technology

Selective laser melting (SLM) is an additive manufacturing process that enables direct manufacturing of 3D complex shape parts and internal architecture from powder materials. The SLM technology is characterised by high temperature gradients and solidification rates that have a significant effect on the microstructures and properties of final parts. The present paper aims at understanding the influence of the initial properties of various martensitic stainless steel powders on the final microstructures and mechanical properties of parts manufactured using the same optimised SLM process parameter settings. The results obtained show that for applied optimum process parameters, the thermal effects are the same for all martensitic powders used. Besides, the final microstructures and properties are different. The results clearly show the effect of the initial complex chemical composition of the martensitic precipitation hardening powder on the microstructures of final parts, and consequently, on their properties.

DLM 공정시 공정변수에 따른 내부공극률과 표면조도 변화

Direct laser melting(DLM) is promising as a joining method for producing parts for automobiles, aerospace, marine and medical applications. An advantageous characteristic of DLM is that it affects the parent metal very little. The mechanical properties of parts made by DLM are strongly affected by the porosity and surface roughness of the laser melted beads. This is a systematic study of the effects of the porosity and surface roughness of laser melted beads using various processing parameters, such as laser power, scan rate and overlapping ratio of the fill spacing. The specimens were fabricated with 316L and 304L austenitic stainless steel powder. Dense parts with low porosity were obtained at low laser scan speed, as it increased the aspect ratio of the parental material and the depth of penetration. The variations of surface roughness were examined at various processing parameters such as overlapping ratio and laser power.

Post Treatment Process and Selective Laser Sintering Mechanism of Polymer-Coated Mo Powder

A novel preparing method of polymer-coated molybdenum powder was presented. A type of multi-component polymer-coated molybdenum powder was chosen for selective laser sintering. The effect of the process parameters on the part's characteristics is investigated. Based on our study for dynamic laser sintering process of polymer-coated molybdenum powder, its laser sintering mechanism was reported as follows: at the early stage of laser sintering, the viscous flow is the major mechanism; during the laser sintering, the melting/solidification is the major mechanism. Furthermore, a model corresponding to the mechanism was discussed schematically, which could be used to explain the material migrating mode during laser sintering process. The laser sintering experiments of polymer-coated Mo powder was conducted in the self-developed laser sintering machine, and optimized parameters have been acquired. At last, the post treatment process of laser sintered parts has been developed and refractory metal parts of Mo/Cu composites are gained. The post treatment process includes debinding, high temperature sintering and melting infiltration, which is sintering framework-Mo by high temperature combining with Cu impregnation method. It is found that the mechanical properties of parts have been greatly improved after the post treatment process.

Improving part quality and process efficiency in layered manufacturing by adaptive slicing

The characteristic of layered manufacturing is the incremental build-up which inevitably leads to the staircase effect. One method to reduce this effect is to optimise part orientation and to apply adaptive slicing procedures. Although layer thickness will be decreased in some regions, process efficiency can be kept to a reasonable level. This paper presents different approaches of adaptive slicing for laser-based applications in consideration of limited range of thickness variation to ensure the mechanical part properties. In contradiction to previous work, the number of applied layer thicknesses is limited due to the associated process parameters. In order to optimise the slicing process and to obtain the best results, this paper presents a practicable approach based on existing work to simulate adaptive slicing. To underline the potential of non-uniform slicing, illustrative examples will show possible improvements in the case of replacing the uniform slicing procedure.

Reduction Possibilities of Electrical Losses in Plastic Working Equipments

Plastic working technologies are frequently applied nowadays, as parts can be produced with larger productivity and smaller material loss compared to other technologies, at the same time the mechanical properties of parts are more favorable. Usually large tensile, pressure, bending or torsional forces, torques are required during plastic working. While pneumatic, hydraulic or electric energy is required to generate these. Used energy is determined by the losses of the energy required for working and that of energy conversion. The losses of working equipment are determined by mechanical losses and the losses of the energy converters applied, as well as by the manufacturing algorithm operating the working equipment. The advantage of electric driven working equipment over pneumatic and hydraulic driven ones is the better efficiency of energy converters, as well as the lower price of electric power. The disadvantage of electric converters is the large dimensions compared to hydraulic or pneumatic systems. Due to the development of electric servo drives the pneumatic and hydraulic drives are to be changed to electric drives in working equipment improving their control and accuracy features besides efficiency. In this paper the loss decreasing possibility of the working equipment with electric servo is investigated.

Characterization of the mechanical properties of samples fabricated by an experimental SGM device

PurposeThe purpose of this paper is to study the effect of different parameters (layer thickness, jetted binder volume per layer and type of binder and temperature) on the mechanical properties of parts made with an experimental 3D printing (3DP) process. This 3DP device built for this project is based on the spiral growth manufacturing (SGM) device previously introduced by Hauseret al.at The University of Liverpool. It differs from the common 3DP in that it generates the different parts using only one rotating piston instead of two non‐rotating ones.Design/methodology/approachSeveral parts are produced using this device according to an experimental design, repeating each run three times. The experimental machine is able to make every part needed without major issues, demonstrating that it is possible to build a functional device using common and standard components.FindingsExperimental analysis of the printed parts shows that the layer thickness has the highest effect on apparent density, hardness and fracture strength of the parts made.Originality/valueEmpirical information is provided about mechanical behavior (e.g. apparent density, hardness and fracture strength) of parts made under different processing factors (e.g. binder type, layer thickness, quantity of binder and chamber temperature) using a SGM‐based 3DP experimental device.

Tensile Properties of Processed FDM Polycarbonate Material

Knowledge of the mechanical properties of parts processed by Fused Deposition Modelling (FDM) rapid prototyping process is essential for engineering applications of such parts as the mechanical strength of parts depends heavily on the FDM process parameters selected during part fabrication. Little knowledge is available for the Polycarbonate (PC) material used in the FDM systems. This paper presents results of the experimental work on the effect of the FDM process parameters such as air gap, raster width, and raster angle on the tensile properties of PC. Results show that FDM made parts have tensile strength in the range of 70 to 75 % of the moulded and extruded PC parts. The results will be valuable for different functional applications of FDM produced parts and assemblies.

Improvement of Mechanical Properties of Injection Molded Wood/Polypropylene Composites Parts with Ultrasonic Oscillation Assistant

Due to the water absorption of wood fillers and poor adhesion between wood fillers and polymer matrix, the loosen material structure always appears in wood/polymer composites after injection molding process, which results in reduced composites mechanical properties. In this study, two kinds of wood particles with different sizes and properties were compounded with Polypropylene (PP) in highly filled level (by 50% and 60% weight concentration). The experimental tensile test samples were prepared by one double-gate injection mould integrated an ultrasonic generator unit. The experiments were carried out for studying how the ultrasonic output power and the oscillation inducing time affect the injection molded wood/PP composites mechanical properties. 3 output power levels (400W, 600W and 800W) and 2 inducing mode were set (Mode1. the oscillation is induced from injecting moment to ejection moment; Mode2. the oscillation is induced from injecting moment to packing procedure finishing). The results show that the E module, tensile strength and density of the test parts are obviously changed with various ultrasonic output power and inducing time. Comparing the mechanical properties of parts with and without ultrasonic assistant indicates that the ultrasonic oscillation is a practical method to improve mechanical properties of injection molded wood/PP composites parts.

Mechanical properties of parts produced by using polymer jetting technology

A study investigating the effects of orientation of parts produced in a layer based process with photopolymer materials is presented. Tensile and hardness testing methods have been used. The test results show that the part producing orientation has an effect on the mechanical properties of the produced parts. The analysis has shown that this is due to the heterogeneity absorption of light energy by the photopolymer material during the jetting process.