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The chapter provides an introduction to mechanical engineering, covering fundamental concepts of mechanical properties of materials and their use in the design and manufacturing. It first explains the notion of mechanical properties of materials and then elaborates on the proper definition of most relevant properties as well as materials testing to...
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... quantity dh tw /dx is the angle of twist per unit length, where h tw is expressed in radians. The corresponding shear stress ( Fig. 7a) is determined from Hooke's law as A simple analysis of Eq. (12) reveals that the shear stress varies linearly with the radial distance q from the axial of the beam. This variation is shown in Fig. 7b. As can be seen, the maximum shear stress, denoted by s max , occurs at the surface of the beam. Note that the above derivations assume ...
Context 2
... quantity dh tw /dx is the angle of twist per unit length, where h tw is expressed in radians. The corresponding shear stress ( Fig. 7a) is determined from Hooke's law as A simple analysis of Eq. (12) reveals that the shear stress varies linearly with the radial distance q from the axial of the beam. This variation is shown in Fig. 7b. As can be seen, the maximum shear stress, denoted by s max , occurs at the surface of the beam. Note that the above derivations assume neither a constant internal torque nor a constant cross section along the length of the beam, i.e., valid for a general case. Two important conclusions follow from this ...
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... However, the starch films with 5% MCC exhibited brittle behavior, with less than 5% elongation at break. A material with low elongation at break, such as less than 5%, is typically considered brittle [39]. This suggests that the higher concentration of MCC makes the films more rigid and less able to undergo plastic deformation before fracture. ...
This study aimed to develop biocomposite films based on cassava starch and microcrystalline cellulose (MCC) derived from cassava pulp for potential medical packaging applications. MCC was extracted from cassava pulp, and its structure and chemical composition, crystallinity, and thermal properties were characterized. The MCC showed a yield of 14.92% and crystallinity of 46.91%. Different MCC contents (1%, 3%, and 5% w/w of starch) were incorporated into cassava starch films. The effects of MCC contents on film properties, including morphology, thickness, mechanical strength, chemical interactions, moisture content, surface wettability, and water activity index, were studied. The effects of UV-C sterilization on the disinfection of starch/MCC on film properties were determined. Results showed that all starch/MCC films exhibited good transparency and thickness ranging from 127 to 144 µm. As MCC content increased from 1 to 5%, Young’s modulus and tensile strength of the films improved significantly from 112.12 to 488.89 MPa and 3.21 to 11.18 MPa, respectively, while elongation at break decreased from 44.74 to 4.15%. Incorporating MCC also reduced film surface wettability, with the water contact angle increasing from 69.17° to 102.82°. The starch/3%MCC holds promise as a biocomposite film for medical packaging applications, offering advantages in terms of good transparency, mechanical properties, and surface hydrophobicity. Furthermore, the absence of microbial growth in the sterilized gauze pad with sealing in the sterilized starch/3%MCC film confirms that the UV-C sterilization, 30 min for each side at 254 nm effectively eliminated any microorganisms present on the starch/3%MCC film without damaging the film properties. This finding highlights a reliable approach to ensuring the sterility of starch/MCC films for medical packaging applications.
... For materials intended for structural and load bearing application, mechanical testing which enables the determination of mechanical strength, toughness, ductility, and other deformability parameters, are crucial to safeguard against premature and costly failures in service (Komvopoulous, 2017;Sehhat et al., 2022). Quality control and research and development units of many manufacturing companies can hardly certify structural products for commercialization without records of their mechanical properties (Astakhov, 2018;Baharuddin and Yani, 2018). Hence there is a growing need for mechanical testing facilities, especially with specifications that permit ease of operation, precision, and accuracy of results. ...
The design and performance evaluation of a 30 kN mechanical testing machine with capacities for room temperature and hot tensile and compression testing was performed. The design philosophy, material selection, and construction strategy were based on the functions and properties of the materials and control systems, local availability, cost considerations, and ease of assembly and decoupling of the parts. Simulation studies were conducted to optimize the design, loading capacity, and specimen dimensions and configurations. The loading mechanism was by a hydraulic system and a loading frame was constructed to house the hydraulic loading, specimen holding, and heating band systems. Testing to ascertain the performance of the machine using aluminum 6063 alloy samples was preceded by load cell and extensometer calibration of the machine. From the performance evaluation, the UTS and percent elongation values for room temperature (25 °C) tensile test (446–454 MPa and 28.3–28.7%) hot tensile tests at 250 °C (232–233 MPa and 36.3–36.7%), room temperature compression test (439–518 MPa and 32.7–33%), and hot compression test at 250 °C (226–233 MPa and 34–35%), were found to be largely reproducible and values were within the range reported in literature for Aluminum 6063 alloy. The softening mechanisms dominant at elevated temperatures ensured that the strain hardening effect was minimal, which is the reason for the superior percent elongation but lower UTS values for tensile and compression tests performed at 250 °C.
... Figure 16 shows the fractured surfaces of PLA and nanocomposite parts printed with 0°rasters. The smooth fractured surfaces are inherent characteristics of a brittle failure, which is consistent with low ε of below 5% observed for these samples [120]. However, it was also shown that the smooth fractured surfaces of PLA became rougher with increasing ZnO concentrations, due to more fillers obstructing the crack propagation [121]. ...
Poly(lactic acid)-zinc oxide (PLA-ZnO) nanocomposites for fused filament fabrication have potential applications in the biomedical field as they combine the bio-compatibility of PLA with the antibacterial properties of ZnO. This work investigates the effects of masterbatch mixing strategy, ZnO concentration and ZnO surface treatment (silanisation) on the printability and the mechanical performance of the nanocomposites as a pre-requirement to the wider uptake of these materials. The results showed that the printability decreased as the filler loading increased. However, the surface treatment of the ZnO powder enhanced the matrix-filler interfacial interactions and reduced the thermal degradation of PLA. This ameliorated the printability and the tensile properties of the nanocomposites filled with up to 5 wt.% of ZnO. Moreover, despite the additional thermal treatment, melt-mixing prevented the degradative effect induced by the solvent used for solvent mixing. Future work will focus on assessing the antibacterial properties of the nanocomposite FFF parts.
... Also, the elongation at break (E) values are 1.33%, 5.33%, and 2.67% for NaAlg1-Gl0.5, NaAlg1-GNp3-Gl0.5, and NaAlg1-GNp5-Gl0.5 membranes, respectively. Generally, materials with an elongation at a break of less than 5% are considered brittle (brittle), and the toughness of brittle (brittle) materials is lower than ductile materials [66]. The reduction in elongation at break can be attributed to the adhesion of the filler to the polymer matrix, which causes the polymer chain to harden, and thus to resist tensile when strain is applied [67]. ...
The development of edible films has gained popularity to extend the shelf life and reduce the use of traditional packaging materials. With the potential of extending the shelf life of food, new environmentally friendly edible films containing graphene nanoplatelet (GNp), sodium alginate (NaAlg), and glycerin (Gl) were prepared. A mathematical model was developed for determining water vapor permeability (WVP) by response surface methodology (RSM) based on a Box–Behnken Design (BBD). Also, the impact of the models was tested using the analysis of variance (ANOVA). Sodium alginate-GNp and glycerin-GNp interactions significantly affected the WVP. The values of WVP for optimum conditions (NaAlg = 1.175 g, GNp = 1.496 (%), and Gl = 0.548 g) were determined by the design model and found 0.0157.
... Although ILSS composites do not degrade under quenching, the fact that the ductility of the cycloaliphatic amine-cured epoxy resin is reduced should be a concern for engineers to apply to constructions with dynamic loads or walls that are directly exposed to weather changes [60]. The oxidation layer on the epoxy resin's surface can potentially reduce the strain-at-break by two types of surface behavior: voiding and cracking [61]. ...
Thermosetting epoxy resin polymer with cycloaliphatic amines curing agent has been widely used for a composite matrix with carbon fiber reinforcement. The utilization was increased due to the superior performance of this epoxy resin compared to other polymers. However, a changing operational environment has potentially reduced composite performance, which most likely begins with matrix degradation. This research applies thermal treatment by the quenching process sequence to the epoxy resin matrix and its reinforced carbon fiber composite (CFRP). The composite is made by epoxy resin diglycidyl ether bisphenol-A, curing with cycloaliphatic amine as matrix and strengthening carbon fiber mat/woven. Three times quenching treatment was performed by heating the specimen around the glass transition temperature and then dipped immediately in fresh water. After quenching treatment, the epoxy resin shows a reduction in tensile strength and elongation. Under infrared observation, epoxy resin does not significantly show changes in functional groups. Investigation under X-ray refraction also indicates no difference in a crystalline structure; this epoxy resin stays in an amorphous form before and after quenching. In contrast to the matrix, the quenching treatment of the CFRP composite above the epoxy resin s glass transition temperature revealed an increase in the interlaminar shear strength (ILSS). The matrix ductility reduction after quenching should be carefully considered for application in the form of epoxy resin sheets or CFRP composite construction materials.
... In the present world of Material Engineering, where new and lighter materials are being developed to replace heavy materials, the characterisation of the material becomes important to determine its properties for effective usage [1]. In a situation where the usage subjects the material to mechanical forces, the need to determine its mechanical properties becomes imperative [2]. The mechanical properties of a material refer to the material's ability to resist mechanical forces and loads. ...
The search for engineering materials for light weight applications, material conservation, and cost effectiveness necessitated the development of new materials. However, the properties of these materials need to be investigated to ascertain its suitability in its application. Hence, the engineering students need to understand the behaviour of these materials and the methods of investigation. This paper presents the development of a piece of simple laboratory equipment for determining the flexural strength of light materials for student practicals. The development process involves the design and construction of the equipment for carrying out 3-point test on a given specimen. The equipment has various components, such as the pivots, force gauge, gauge holder, rack and pinion gear, hand lever and the frame. The graphics design and simulation were done with solidworks software, version 10. The materials used for the production of these components were selected in line with material selection guidelines and also according to the mathematical designed parameters. The selected materials were locally sourced for cost effectiveness. The construction processes involve basic engineering process like cutting, filling, drilling, welding and surface finishing, at the total cost of 125 USD. After construction, the equipment was used to perform a 3-point test on three different materials (Perspex, Plywood and Particle Board), and flexural strengths of 86.3MPa, 26.62MPa and 21.96MPa respectively were obtained. The equipment is recommended for testing a low ductile material requiring a maximum flexural force of 500N and maximum deflection of 0.1m. Hence, it can be used in high colleges for the study of strength of materials.
... In the present world of Material Engineering, where new and lighter materials are being developed to replace heavy materials, the characterisation of the material becomes important to determine its properties for effective usage [1]. In a situation where the usage subjects the material to mechanical forces, the need to determine its mechanical properties becomes imperative [2]. The mechanical properties of a material refer to the material's ability to resist mechanical forces and loads. ...
... The effects of the strain rate and temperature on material dynamic fracture and corresponding fracture strain models have been focused on in recent years through SHPB tests. It has been acknowledged that material fracture strain decreases with either increasing the strain rate or decreasing the temperature [82]. An increase in the strain rate promotes the ductile to brittle transition of ductile materials. ...
The research and application of high speed metal cutting (HSMC) is aimed at achieving higher productivity and improved surface quality. This paper reviews the advancements in HSMC with a focus on the material removal mechanism and machined surface integrity without considering the effect of cutting dynamics on the machining process. In addition, the variation of cutting force and cutting temperature as well as the tool wear behavior during HSMC are summarized. Through comparing with conventional machining (or called as normal speed machining), the advantages of HSMC are elaborated from the aspects of high material removal rate, good finished surface quality (except surface residual stress), low cutting force, and low cutting temperature. Meanwhile, the shortcomings of HSMC are presented from the aspects of high tool wear rate and tensile residual stress on finished surface. The variation of material dynamic properties at high cutting speeds is the underlying mechanism responsible for the transition of chip morphology and material removal mechanism. Less surface defects and lower surface roughness can be obtained at a specific range of high cutting speeds, which depends on the workpiece material and cutting conditions. The thorough review on pros and cons of HSMC can help to effectively utilize its advantages and circumvent its shortcomings. Furthermore, the challenges for advancing and future research directions of HSMC are highlighted. Particularly, to reveal the relationships among inherent attributes of workpiece materials, processing parameters during HSMC, and evolution of machined surface properties will be a potential breakthrough direction. Although the influence of cutting speed on the material removal mechanism and surface integrity has been studied extensively, it still requires more detailed investigations in the future with continuous increase in cutting speed and emergence of new engineering materials in industries.
... In the Device, the triangular connector and triangle connector seat are made of AlMgSi1F28, the pin is made of 42CrMo4, the bearing inner ring is made of 42Cr, and the bearing outer ring is made of 45# steel. The metallic materials were analysed by a linear constitutive model, using the mechanical parameters in Table 1 below [13]. In addition, the rubber bushing is made of natural rubber, which is an incompressible, isotropic, super-elastic polymer with nonlinear stiffness features. ...
... Structures in engineering applications, including those made of titanium alloys, are generally operated under complex loading conditions. An accurate prediction of potential failure for structures requires abundant knowledge about materials fracture behavior and associated fracture mechanism under various loading conditions [4][5][6]. ...
The material fracture behavior and associated mechanism is known to be affected by the stress state and strain rate. Using a recently developed rectangular hat-shaped specimen, the fracture behavior of Ti6Al4V was investigated with a stress triaxiality varying from -0.31 to 0.50 at strain rates ranging from quasi-static to 10^4 /s. The fracture mechanisms of Ti6Al4V under these conditions were studied at micro-scale through observations of cross-sectional microstructure and quantitative analysis of fracture surface morphology. It was found that λ, a parameter defining the percentage of equiaxed dimples on the fracture surface, shows a close correlation with the observed fracture mechanism. Therefore, a λ based criterion based has been introduced in this work to quantitatively describe the transition of fracture mechanisms. It was observed that the embrittlement of Ti6Al4V was promoted by a higher strain rate or a larger positive stress triaxiality, as expected. However, the stress triaxiality appeared to play a more dominant role. At sufficiently high negative or positive stress triaxiality values, the effect of strain rate on fracture mechanism became negligible.
