Traditional Metallic Materials Research Articles

A Rupture Limit Equation for Pre-Loaded Laminated Composite Plates

Fiber-reinforced polymer composites offer inherent advantages over traditional metallic materials in a number of different ways; however, these materials are also highly susceptible to impact damage. In this paper, we explore the response of FRP (fiber reinforced polymer) composites under impact conditions that could result in their rupture or catastrophic failure. The work performed was aimed at developing a general, data-driven equation for initially-stressed, flat, composite plates that would differentiate between impact conditions that would result in only a hole or crack and those which would cause catastrophic plate failure or rupture. If this equation were to be subsequently shown to also model the rupture/non-rupture behavior of, for example, composite overwrapped pressure vessels, then it could also be used to appropriately tailor the design parameters and/or operating conditions of such pressurized tanks.

Numerical evaluation of the performances of a multilayered

The improvements made in the field of the research of composite materials led to the wide usage of composite materials, which, nowadays, tend to replace traditional metallic materials in engineering applications. In this paper, the performances of a landing gear, subjected to dynamic loadings and made of a multilayered honeycomb composite material are evaluated in comparison with traditional metallic materials using numerical simulation. The obtained values of mechanical stress for the hybrid landing gear design are lower compared to those for a landing gear made entirely of aluminium. The use of the multilayered honeycomb composite material decreases the values of the stresses, for the given load case. Also, reduction of the mass of the landing gear improves flight dinamics and increases manoeuvrability.

Evolution of high temperature yield strength of AlCoCrFeNiTi high entropy alloys

Comparing with the properties of traditional metallic materials, high-entropy alloy has usually exhibited higher yield strength and hardness. Scientists and engineers are very keen to explore the possibilities to use high-entropy alloy in harsh environments with high temperature and pressure. So far, there have been very few reported studies on the yield strength of high-entropy alloys at elevated temperatures. In this study, AlCoCrFeNiTi high-entropy alloy was chosen to investigate its stress-strain relations under high temperature. Three different conditions of AlCoCrFeNiTi were studied (namely, as-cast, homogenized and hot deformed). The high temperature compression tests were conducted by using a Gleeble 3500 machine. AlCoCrFeNiTi material showed a high yield strength (159MPa) under 1100 ˚C with a strain rate of 1s-1. However, no visible cracks were observed on the surface of specimen after 46.6% of height reduction, which indicated that AlCoCrFeNiTi material possesses high yield strength and good formability.

Axial crushing of metal-composite hybrid tubes: experimental analysis

In the automotive sector, special attention is paid to the study of the behavior of the structural components that make the car bodies. The continuous demands on the weight saving imply the car bodies to be assembled with components made in different materials and using different manufacturing processes. Considering the making of the sacrificial structures aimed to the energy absorption, composite materials are increasingly used to replace conventional metal materials. However, the use of composites is accompanied with a change in the type of deformation obtained during the impact phenomenon. Usually, with the conventional metal materials, the crushing behavior is a progressive buckling whereas the composite materials are characterized by a brittle fracture. The combination of the traditional metal materials with the composite ones can represent a good solution to obtain high levels of performance.In this context, the structural performance of metal-composite hybrid tubes subjected to quasi-static axial crushing is experimentally evaluated in this work. The specimens, with circular cross section, were obtained with tubes made in a fully thermoplastic composite internally reinforced with aluminum tubes. The composite material used were made in polypropylene both for the matrix and for the reinforcing fibers. This material has a good axial absorption capacity but irregular behavior during crushing. The addition of a conventional material as reinforcement allowed to increase the absorption capacity by ensuring a more progressive and controlled crush. The analysis was carried out by evaluating, for various geometric configurations, different parameters (mean load, average stress, specific energy, efficiency). The results, discussed in the work, showed how the energy absorption performance of a hybrid structure are higher than the sum of the performance of the single materials.

Fatigue crack initiation of magnesium alloys under elastic stress amplitudes: A review

The most advantageous property of magnesium (Mg) alloys is their density, which is lower compared with traditional metallic materials. Mg alloys, considered the lightest metallic structural material among others, have great potential for applications as secondary load components in the transportation and aerospace industries. The fatigue evaluation of Mg alloys under elastic stress amplitudes is very important in ensuring their service safety and reliability. Given their hexagonal close packed structure, the fatigue crack initiation of Mg and its alloys is closely related to the deformation mechanisms of twinning and basal slips. However, for Mg alloys with shrinkage porosities and inclusions, fatigue cracks will preferentially initiate at these defects, remarkably reducing the fatigue lifetime. In this paper, some fundamental aspects about the fatigue crack initiation mechanisms of Mg alloys are reviewed, including the 3 followings: 1) Fatigue crack initiation of as-cast Mg alloys, 2) influence of microstructure on fatigue crack initiation of wrought Mg alloys, and 3) the effect of heat treatment on fatigue initiation mechanisms. Moreover, some unresolved issues and future target on the fatigue crack initiation mechanism of Mg alloys are also described.

АНАЛІЗ ТЕРМОРОЗМІРОСТАБІЛЬНОЇ НЕСУЧОЇ КОНСТРУКЦІЇ ПРИЛАДУ КОРИСНОГО НАВАНТАЖЕННЯ КОСМІЧНОГО АПАРАТА

The basic provisions of the engineering procedure for development of shell cylindrical structures made of composite materials are presented in this paper. Development of shell cylindrical structures made of composite materials occupies a prominent place in development of structures made of composite materials. Such structures are commonly used as bearing members of optical-electronic equipment and must ensure a high quality of its operation.This procedure was developed for physical-mechanical characteristics prediction of composite structures. This work is topical because composite material has well-marked anisotropy of its characteristics and procedure of development of structure made of traditional metal materials cannot be used in this situation.The main feature of this work is application of analytical method of designing dimensionally stable structure. This method is the basis for the design engineering procedure for shell cylindrical structures made of composite materials. Applicability of the procedure was confirmed by structural analyses of the structure with the use of finite element method and dimension-stability tests of cylindrical test samples (with different layup schedules). Dimension-stability test of the developed drawtube structure was performed. Main operations of dimension-stability test of the structure are presented in the paper too.Such procedure allows optimizing of physical-mechanical properties of composite structures and shows the ways to reduce weight and overall dimensions of the structure.Key phases of the procedure are listed in this paper. Presented formulae allow to calculate approximately a cylindrical structure thermal strain and check structure strength. The developed procedure may be helpful during development of similar shell cylindrical structures made of composite materials.

Experimental study of wear for implant materials under dry sliding conditions

PurposeArtificial biomaterials are implanted to the human body to support the structure depending upon the extent of deformity or damage. This paper aims to formulate an experimental approach to assess the suitability of materials that can be used in the manufacture of human implants.Design/methodology/approachFive different pin materials such as SS304, Alumina, HDPE, UHMWPE and Brass have been chosen to be suitable for implants. The tribological properties of the aforementioned materials have been tested on a simple pin-on-disc apparatus. EN31 was chosen as the disc material because its hardness value is much higher than that of the pin materials used. The test materials were constructed in the form of spherical end pins to have point contacts and to reduce the depth of wear.FindingsIt has been observed that the polymeric (HDPE and UHMWPE) and ceramic materials (Alumina) are much better than the traditional metallic materials. The wear rate is very low for these materials owing to their self-lubricating properties.Practical implicationsThe experimental studies will help predict the performance and life of implant materials in the human body.Originality/valueIn most cases, SS316L that possesses nickel compositions is used as the disc material; SS316L is toxic to the human body. In the present study, a high carbon alloy steel with high degrees of hardness EN31 is used as a disc counter-face material.

Understanding the mechanical characteristics of nanotwinned diamond by atomistic simulations

As is known to all, diamond is the hardest natural substance. The synthesis of harder materials than the natural diamond is very favorable but challenging. It has been found that the introduction of nanotwinned (NT) structure into diamond could be an effective approach to improve the hardness of diamond. Nevertheless, the fundamental understanding of the strengthening characteristics by NT structure is still ambiguous. In this work, we unveil the effect of NT structure on the deformation mechanism and mechanical properties of diamond at the atomic scale by virtue of atomistic simulations. Interestingly, the hardness measured by nanoindentation shows a positive correlation to the twin spacing instead of the inverse Hall-Petch effect extensively discovered in many traditional metal materials. However, it is not the smallest twin spacing achieving the highest tensile strength, indicating the existence of twin-spacing-induced inverse Hall-Petch effect in NT diamond during tensile deformation. The specific deformation mechanisms are investigated which are capable of providing an explicit explanation for the observed mechanical characteristics.

Fiber-optic anemometer based on single-walled carbon nanotube coated tilted fiber Bragg grating.

In this work, a novel and simple optical fiber hot-wire anemometer based on single-walled carbon nanotubes (SWCNTs) coated tilted fiber Bragg grating (TFBG) is proposed and demonstrated. For the hot-wire wind speed sensor design, TFBG is an ideal in-fiber sensing structure due to its unique features. It is utilized as both light coupling and temperature sensing element without using any geometry-modified or uncommon fiber, which simplifies the sensor structure. To further enhance the thermal conversion capability, SWCNTs are coated on the surface of the TFBG instead of traditional metallic materials, which have excellent thermal characteristics. When a laser light is pumped into the sensor, the pump light propagating in the core will be easily coupled into cladding of the fiber via the TFBG and strongly absorbed by the SWCNTs thin film. This absorption acts like a hot-wire raising the local temperature of the fiber, which is accurately detected by the TFBG resonance shift. In the experiments, the sensor's performances were investigated and controlled by adjusting the inherent angle of the TFBG, the thickness of SWCNTs film, and the input power of the pump laser. It was demonstrated that the developed anemometer exhibited significant light absorption efficiency up to 93%, and the maximum temperature of the local area on the fiber was heated up to 146.1°C under the relatively low pump power of 97.76 mW. The sensitivity of -0.3667 nm/(m/s) at wind speed of 1.0 m/s was measured with the selected 12° TFBG and 1.6 μm film.

A Novel Low-Power-Consumption All-Fiber-Optic Anemometer with Simple System Design.

A compact and low-power consuming fiber-optic anemometer based on single-walled carbon nanotubes (SWCNTs) coated tilted fiber Bragg grating (TFBG) is presented. TFBG as a near infrared in-fiber sensing element is able to excite a number of cladding modes and radiation modes in the fiber and effectively couple light in the core to interact with the fiber surrounding mediums. It is an ideal in-fiber device used in a fiber hot-wire anemometer (HWA) as both coupling and sensing elements to simplify the sensing head structure. The fabricated TFBG was immobilized with an SWCNT film on the fiber surface. SWCNTs, a kind of innovative nanomaterial, were utilized as light-heat conversion medium instead of traditional metallic materials, due to its excellent infrared light absorption ability and competitive thermal conductivity. When the SWCNT film strongly absorbs the light in the fiber, the sensor head can be heated and form a “hot wire”. As the sensor is put into wind field, the wind will take away the heat on the sensor resulting in a temperature variation that is then accurately measured by the TFBG. Benefited from the high coupling and absorption efficiency, the heating and sensing light source was shared with only one broadband light source (BBS) without any extra pumping laser complicating the system. This not only significantly reduces power consumption, but also simplifies the whole sensing system with lower cost. In experiments, the key parameters of the sensor, such as the film thickness and the inherent angle of the TFBG, were fully investigated. It was demonstrated that, under a very low BBS input power of 9.87 mW, a 0.100 nm wavelength response can still be detected as the wind speed changed from 0 to 2 m/s. In addition, the sensitivity was found to be −0.0346 nm/(m/s) under the wind speed of 1 m/s. The proposed simple and low-power-consumption wind speed sensing system exhibits promising potential for future long-term remote monitoring and on-chip sensing in practical applications.

Hydrogen effects on Ni-Ti fatigue performance by self -heating method

Ni-Ti superelastic alloys are extensively used in manufacturing biomedical devices because of their high mechanical performance, good fatigue durability and biocompatibility compared to traditional metallic materials. During clinical use, most of these devices are intended to work under cyclic or repetitive loadings and may be in contact with corrosive environments leading to unexpected failures. It is however recognized that the fatigue–environment interaction, especially fatigue–hydrogen absorption, can be the main cause of these failures. The aim of this work is to investigate the fatigue behavior of superelastic Ni-Ti intended for manufacturing medical devices at high number of cycles (HCF) with a particular emphasis to the effect of hydrogen on fatigue properties. Fatigue tests were analyzed using self-heating measurements based on observing thermal effects during cyclic loadings. The results obtained with self-heating approach showed a trend of a decrease in the fatigue life of Ni-Ti alloys after hydrogen absorption and the fatigue limit extrapolated will be compared with the results obtained with the classical S-N curves method.

Pseudo-creep in Shape Memory Alloy Wires and Sheets

Interruption of loading during reorientation and isothermal pseudoelasticity in shape memory alloys with a strain arrest (i.e., holding strain constant) results in a time-dependent evolution in stress or with a stress arrest (i.e., holding stress constant) results in a time-dependent evolution in strain. This phenomenon, which we term as pseudo-creep, is similar to what was reported in the literature three decades ago for some traditional metallic materials undergoing plastic deformation. In a previous communication, we reported strain arrest of isothermal pseudoelastic loading, isothermal pseudoelastic unloading, and reorientation in NiTi wires as well as a rate-independent phase diagram. In this paper, we provide experimental results of the pseudo-creep phenomenon during stress arrest of isothermal pseudoelasticity and reorientation in NiTi wires as well as strain arrest of isothermal pseudoelasticity and reorientation in NiTi sheets. Stress arrest in NiTi wires accompanied by strain accumulation or recovery is studied using the technique of multi-video extensometry. The experimental results were used to estimate the amount of mechanical energy needed to evolve the wire from one microstructural state to another during isothermal pseudoelastic deformation and the difference in energies between the initial and the final rest state between which the aforementioned evolution has occurred.

Increased Runx2 expression associated with enhanced Wnt signaling in PDLLA internal fixation for fracture treatment.

Poly-D-L lactide (PDLLA) biodegradable implants to heal fractures are widely applied in orthopedic surgeries. However, whether the process of fracture healing is regulated differently when PDLLA is used compared with traditional metal materials remains unclear. Runt-related transcription factor 2 (Runx2) and canonical Wnt signaling are essential and may interact reciprocally in the regulation of osteogenesis during bone repair. In the present study, a rat femoral open osteotomy model was used to compare the curative efficacy of a PDLLA rod and Kirschner wire under intramedullary fixation for fracture treatment. The dynamic expression of Runx2 and key components of the canonical Wnt signaling in callus tissue during fracture healing was also investigated. The results of the current study indicate that at weeks 4 and 6 following fixation, the callus bone structural parameters of microCT were significantly improved by PDLLA rod compared to that of Kirschner wire. In addition, at weeks 4 and 6 after fixation, the protein and mRNA expression of Runx2 and the positive regulators of canonical Wnt signaling, such as Wnts and β-catenin, were significantly increased. However, the protein and mRNA expression levels of the negative regulators of canonical Wnt signaling, such as glycogen synthase kinase-3β, were significantly decreased in callus tissue when treated with PDLLA rod compared with Kirschner wire. Collectively, these data indicate that compared to the traditional metal material, using PDLLA internal fixation for fracture treatment may further improve bone formation, which is associated with the increased expression of Runx2 and the enhancement of canonical Wnt signaling.

Sound insulation analysis and optimization of anti-symmetrical carbon fiber reinforced polymer composite materials

Due to the advantages of high strength and low density, carbon fiber reinforced polymer (CFRP) composite material has become more and more attractive given the increasing demand of lightweight design requirement in the automobile industry. However, as density reduces, the sound insulation ability of CFRP panels is usually inferior compared with traditional metal materials such as steel and aluminum, which may lead to deteriorated noise insulation performance inside the vehicle cabin when the CFRP material is used as body panels. For the sake of investigating the sound insulation ability of CFRP, two optimization methods are proposed, and the optimal ply angles that lead to the largest sound transmission loss in two different frequency ranges are obtained accordingly. On the basis of optimization, the sound insulation capability of CFRP and two metal materials are thoroughly compared. It is found that, when optimally designed, the CFRP panel can achieve a transmission loss level comparable to its metal counterparts at low frequencies (e.g., <300Hz) with substantially less weight.

The Preparation and Experimental Research for Inner Cladding Casting of Al-Al

With the rapid development of science and technology, the unceasing enhancement of component integration degree, and the increasingly demanding of parts using conditions, the part that the traditional metal materials and alloy materials preparation is hard to meet the requirements of the use of some special conditions, so the new composite materials have been paid attention to by the countries all over the world. An casting method for Inner Cladding Casting was introduced. By the use of this method, the Al-Al inner cladding casting which has the transition layer in the middle was prepared, it was indicated that the casting method for inner cladding casting has the feasibility. Through the soaking experiments of three group samples which were Arc Spraying Al layer、substrate of Al and Inner Cladding Casting of Al-Al, we find out that by 140h soaking experiments for inner cladding casting of Al-Al the porosity change was little and it had shown very good corrosion resistant effect.

Design and Empirical Analysis of Selected Machine Elements from Composite Materials is Better to Use

Weight reducing weights, improving mechanical properties and maintaining strength of mechanical components are critical task in all manufacturing industries. However, this compressive advantage was achieved by the proper design, manufacturing and material selection of composite materials. Thus, the objective of this paper was to design and analyse a composite tailstock dead centre support to improve the traditional metallic material tailstock dead centre supports. Since, this replacement of composite materials for traditional metallic materials have many advantages because of higher specific stiffness, wear resistance, light weight, and strength of composite materials. In this empirical study was included and addressed with the replacement of conventional steel tailstock dead centre support from composite materials. Since the HS Glass/Epoxy is used as composite material and the weight minimization improving design parameters were done in the study. However the design optimization analysis indicates that, there was significant improvement is observed in the performance of tailstock dead centre support (in terms of weight, strength, thermal resistance). The study also attempt analyses has the deflection, the effects of stresses, wear-resistance, thermal effect natural frequencies under subjected loads using mathematical analysis were done. In the conclusion, the study investigates that light weight, safe and economical tailstock supports are made from HS carbon/Epoxy material using filament winding process. As well supplementary evaluation carried out for both steel and composite materials and weight of the tailstock dead centre support is optimized and stress intensity factor found for both Steel and composite tailstock dead centre support will consider.

Design of the crashworthy structure of an urban aircraft

With the development of general aviation, the urban aircraft is around the corner. The urban aircraft with composite is considered as an ultralight vehicle and the crashworthiness is of vital importance for such an ultralight aircraft. Composites are being widely and increasingly used in the aerospace industry because of their advantages that include the high specific strength and stiffness over traditional metallic materials. Besides, composites have the potential for absorbing the energy in a crash event. The crashworthiness of the cockpit section is analyzed in this paper and some modifications in the subfloor have been made to improve the survivability of the pilot. Advances in commercial softwares have enabled engineers to simulate crash events. The three-dimensional structure model is established by use of CATIA software and the crash process is simulated by MSC/DYTRAN. By comparing the crashworthiness of composite structures, reliable basis is provided for the design of a safe and sound structure.

Thermoplastic forming of bulk metallic glasses

The viscosities of metallic glasses gradually drop with temperature rising in their supercooled liquid region (SLR) which enables them to be thermoplastically formed and totally overturns the processing method of traditional metallic materials: their forming can be realized under temperature and stress far below those of traditional metallic materials. Based on this property, metallic glasses are considered as the ideal miniature fabrication materials due to their unique amorphous structures and no crystalline defects such as dislocation and grain boundary.The thermoplastic micro forming of metallic glasses in their SLR is studied in the present paper. A universal equation which describes the filling kinetics of viscous metallic glasses in the non-circular channel is proposed with the help of fluidic mechanics, and the results may be theoretically useful for the micro application of metallic glasses.In addition, some applications in the micro thermoplastic forming of metallic glasses are introduced. A metallic glass mold insert for hot embossing of polymers is fabricated by the micro thermoplastic forming of metallic glass, and it is found to have many advantages in mechanical property, fabrication efficiency, surface quality, etc. compared with the traditional material and method. A similar approach is used to fabricate gratings, which may provide a new material and technology to produce gratings. The superhydrophobic metallic glass surface with excellent abrasion and corrosion resistance is also fabricated by constructing micro-nano hierarchical structures on metallic glass surface. The bulk metallic glass micro fuel cell is also finished and found to have good performance.

Research on Lightweight Design of Automobile Lower Arm Based on Carbon Fiber Materials

Based on the principle of lightweight design, a method of using carbon fiber reinforced composite instead of traditional metal materials to design automobile carrier can be proposed. The method uses the equal stiffness design principle of the composite material parts to lay out the design of the carbon fiber parts, including the application of the laying angle and the thickness of the laying layer in design. Through the analysis of the actual working conditions of the lower arm, the stress and boundary conditions are obtained. After the design of the stiffness, the geometrical topology of the lower arm is further optimized. Finally, the lower arm of the carbon fiber not only met the performance requirements, but also to a certain extent, achieved the purpose of lightweight.

Fracture behaviors under pure shear loading in bulk metallic glasses.

Pure shear fracture test, as a special mechanical means, had been carried out extensively to obtain the critical information for traditional metallic crystalline materials and rocks, such as the intrinsic deformation behavior and fracture mechanism. However, for bulk metallic glasses (BMGs), the pure shear fracture behaviors have not been investigated systematically due to the lack of a suitable test method. Here, we specially introduce a unique antisymmetrical four-point bend shear test method to realize a uniform pure shear stress field and study the pure shear fracture behaviors of two kinds of BMGs, Zr-based and La-based BMGs. All kinds of fracture behaviors, the pure shear fracture strength, fracture angle and fracture surface morphology, are systematically analyzed and compared with those of the conventional compressive and tensile fracture. Our results indicate that both the Zr-based and La-based BMGs follow the same fracture mechanism under pure shear loading, which is significantly different from the situation of some previous research results. Our results might offer new enlightenment on the intrinsic deformation and fracture mechanism of BMGs and other amorphous materials.