Mechanical Tests Research Articles

Selecting the suitable thermoplastic elastomer as the main component in the feedstock for metal material extrusion of aluminium

Metal material extrusion (MMEX) involves the systematic deposition of material layer by layer, followed by debinding and sintering to produce fully dense metallic parts. The feedstocks, initially comprising metal powder and a binder system, are pivotal in determining processability and final properties. This study utilized polylactic acid (PLA) as the backbone and a thermoplastic elastomer (TPE) as the primary, solvent-debindable component in the binder system, with a 50 and 55 vol% aluminium (Al) powder content. PLA was selected due to its lower degradation temperature and to try to increase the sustainability of the MMEX process. An initial experimentation with various TPEs, employing thermal analysis (TGA and DSC), rheological behavior assessment, mechanical property testing, contact angle measurement, and solvent debinding processes, aimed to identify the most suitable TPE for this study. The results demonstrated that a very low interfacial tension between PLA and TPE is not desirable, as it may result in the removal of some powder particles during the solvent-debinding process. The TPE type with lower viscosity, optimum interfacial tension with PLA, low residue after degradation, adequate rigidity, and flexibility is proper for use as the soluble part of the binder system. After selecting of the appropriate TPE, the printability at a nozzle temperature of 270 °C was undertaken. The solvent debinding process for printed samples was conducted at room temperature. The results indicated that 90 wt% of the TPE was removed successfully from the samples printed with 30 vol% PLA in binder formulation without any defects during solvent debinding.

Conventional Manufacturing by Pouring Versus Additive Manufacturing Technology of β-Tricalcium Phosphate Bone Substitute Implants.

The aim of the study was to compare conventional sintering with additive manufacturing techniques for β-TCP bioceramics, focusing on mechanical properties and biocompatibility. A "critical" bone defect requires surgical intervention beyond simple stabilization. Autologous bone grafting is the gold standard treatment for such defects, but it has its limitations. Alloplastic bone grafting with synthetic materials is becoming increasingly popular. The use of bone graft substitutes has increased significantly, and current research has focused on optimizing these substitutes, whereas this study compares two existing manufacturing techniques and the resulting β-TCP implants. The 3D printed β-TCP hybrid structure implant was fabricated from two components, a column structure and a freeze foam, which were sintered together. The conventionally fabricated ceramics were fabricated by casting. Both scaffolds were characterized for porosity, mechanical properties, and biocompatibility. The hybrid structure had an overall porosity of 74.4 ± 0.5%. The microporous β-TCP implants had a porosity of 43.5 ± 2.4%, while the macroporous β-TCP implants had a porosity of 61.81%. Mechanical testing revealed that the hybrid structure had a compressive strength of 10.4 ± 6 MPa, which was significantly lower than the microporous β-TCP implants with 32.9 ± 8.7 MPa. Biocompatibility evaluations showed a steady increase in cell proliferation over time for all the β-TCP implants, with minimal cytotoxicity. This study provides a valuable insight into the potential of additive manufacturing for β-TCP bioceramics in the treatment of bone defects.

Effect of Phosphate-Bridged Monomer on Thermal Oxidative Behavior of Phthalonitrile Thermosets.

Phthalonitrile thermosets are known for their excellent mechanical, physico-chemical, and fire-retardant properties, making them attractive for aerospace and mechanical engineering applications. When producing and applying phthalonitrile-based structural parts, it is essential to consider aspects such as processability and the long-term stability of the material's properties at high temperatures. In our previous studies, we demonstrated that resins containing phosphate-bridged bisphthalonitrile monomers are easily processable due to their low melting temperature and wide processing window. In this study, we investigated the impact of bis(3-(3,4-dicyanophenoxy)phenyl)phenyl phosphate (PPhPN) monomer content on physico-chemical and mechanical properties, thermal stability, and thermal oxidative stability. This research highlights the importance of conducting long-term thermal oxidative aging studies in addition to thermogravimetric analysis to properly assess the stability of thermosets. The findings indicate that adding less than 15% of PPhPN results in the formation of a crystalline phase, which impairs the resin's processability. Conversely, a high PPhPN content reduces the material's thermal oxidative stability. Therefore, based on mechanical and physico-chemical tests after thermal oxidative aging, it can be concluded that a 10-15% concentration of the phosphate-containing monomer enables easy processability of the phthalonitrile resin and provides excellent long-term thermal oxidative stability at temperatures up to 300 °C, while maintaining a flexural strength exceeding 120 MPa and an elasticity modulus of 4.3 GPa.

Does ESG decoupling reduce customer stability? Evidence from China

ABSTRACT This paper examines the influence of corporate environmental, social, and governance (ESG) decoupling on customer stability. Using a sample of Chinese listed firms, we discover a significantly negative nexus between corporate ESG decoupling and customer stability. Mechanism tests reveal that ESG decoupling reduces customer stability by damaging corporate reputation and increasing information asymmetry. Cross-sectional analyses demonstrate that ESG decoupling’s adverse influence on customer stability is more prominent in state-owned companies, non-high-tech firms, and firms with fiercer industry competition. Our results show that customers, as corporate primary stakeholders, punish suppliers’ ESG decoupling behaviour. This paper enriches the emerging literature on the consequences of ESG decoupling. Meanwhile, our findings offer implications for firms to maintain supply chain security and stability.

Accounting for friction in the mechanical testing of athletics tracks

This investigation deals with the problem of identifying the mechanical behaviour of rubbers from compression tests, performed on specimens having unfavorable geometry. A typical situation is that of flat specimens obtained from high-friction sports surfaces. To this purpose, experimental tests were conducted, aimed at measuring friction under various conditions and evaluating its effect on the compressive behavior of different rubber samples. The experimental results have been interpreted in view of an existing analytical model proposed by Gent and coworkers. The method was shown to be valid within a relatively broad range of conditions (in terms of materials, lubrication and aspect ratio). Its application allowed the creation of virtual “frictionless” curves, by rescaling experimental data for the stiffening factor predicted by Gent model. These curves represent more closely the intrinsic material behaviour, removing the large frictional contribution present in the experimental tests, and can be used as a more reliable input for numerical simulations.

High-temperature aging and long-term mechanical properties of polyphenylene sulfide composites for marine use

ABSTRACT Advanced polymeric composites and manufacturing techniques promote developments of marine structures significantly (e.g., spare parts supply chain of shipbuilding and maintenance). In this paper, the GNP/CF-PPS (graphene nanoplatelets short carbon fibre polyphenylene sulfide composite) samples are prepared by mechanically mixing CF-PPS plastic pellets and GNP particles. The mixed compound is 3D-printed by material extrusion additive manufacturing, and the bending mechanics test is carried out to explore how nanoreinforcement affects the ability of printed composites to perform under high temperature conditions. The results show that CF-PPS and GNP/CF-PPS samples have the highest flexural strength at room temperature. As the temperature rises to 260°C, the stiffness increases by 4.8% and 6.7% respectively, while the deflection decreases by 30.4% and 25.6% respectively. The characterisation results of scanning electron microscopy (SEM) show that the cross-sectional pores of CF-PPS samples after adding GNP are relatively reduced, indicating the improvement in the structural stability.

Parallel-beams magnetic actuator for in-situ transmission electron microscope observation of mechanical testing

Abstract Understanding the microscopic mechanisms behind mechanical fractures is essential for enhancing material properties and increasing reliability through fatigue suppression. Conventional mechanical testing methods, such as indentation tests that press a sharp needle into a specimen or tensile tests using hydraulic pumps, are unable to capture nanoscale deformations under applied forces. As a result, the microscopic mechanisms that influence mechanical properties are often inferred indirectly, and material design largely depends on the engineer’s intuition and occasional serendipity. To overcome these challenges, in-situ observation techniques utilizing transmission electron microscopes (TEMs) have been developed to enable the observation of sample deformations at the nanoscale. However, despite their high resolution, conventional TEMs are limited by a small available space -often just a few millimeters- that restricts the application of sufficient force to fracture specimens. Traditional actuation methods, such as thermal expansion, electrostatic force, and piezoelectric actuators, fail to generate significant forces within such confined spaces. In response to these limitations, our research involved the development of a micromachine with multiple parallel beams. This device leverages the Laplace force generated by an electric current passing through the beams and the magnetic field of the TEM. We demonstrated the capability to produce significant force using the magnetic field from the microscope’s magnetic lens. The actuator developed in our study successfully generated forces exceeding 50 µN, marking a significant advancement in the in-situ observation capabilities for mechanical testing.

Chemical treatment, fibre length, and fibre loading affecting the mechanical and morphological characteristics of flax fibre/polylactic acid (PLA) green composites developed by injection moulding

AbstractThis paper presents the parametric investigation and optimization of various chemical treatment parameters that affect the mechanical performance of the green composite. The injection moulding method was used to produce the green composites using flax fibre (FF) and polylactic acid (PLA). The chemical parameters chosen to investigate their effects are chemical type (sodium hydroxide, sodium carbonate, and potassium hydroxide), chemical concentrations (1 %, 2 %, and 3 % (w/v)), and duration for fibre treatment (2 h, 4 h, and 6 h). The mechanical performance of the green composites was assessed by evaluating the various properties namely strength, modulus, and elongation under tensile, share, flexural, and compression loading conditions. The morphological study was also performed to examine the failure behavior of the composite after mechanical testing. The effect of fibre length (2 mm, 3 mm, 4 mm, 5 mm, and 6 mm) and fibre loading (10 wt.%, 20 wt.%, and 30 wt.%) on the performance of the flax fibre (FF)/polylactic acid (PLA) composite was also investigated. The fibre dispersion, fibre orientation, and fibre length retention were investigated to assess the characteristics of fibre during injection moulding of the developed flax fibre (FF)/polylactic acid (PLA) composite.

Recovery of the Infraorbital Nerve Following Open Reduction and Fixation Surgery of Zygomaticomaxillary Complex Fractures-A Prospective Cohort Study Based on Quantitative Sensory Testing.

This study aimed to assess the sensory function of the infraorbital nerve in patients with fractures of the zygomatic complex who underwent open reduction and internal fixation at different time points using quantitative sensory testing, which was established by the German Neuropathic Pain Research Network, comprising a 7-item mechanical and thermal sensory test. A total of 21 patients (age range 17-46y, 14 males) with unilateral zygomatic complex fractures were included. Quantitative sensory testing was conducted before the operation and at 1 week, 3 months, and 6 months operatively, with cold detection threshold, warmth detection threshold, cold pain threshold, heat pain threshold, mechanical detection threshold, mechanical pain threshold, pressure pain threshold, and vibration detection threshold being measured in bilateral infraorbital regions. Notable changes in sensitivity were observed in all values except for the mechanical pain threshold. In the majority of patients with zygomaticomaxillary complex fractures, infraorbital hypoesthesia was significantly improved within 3 months postoperatively, and almost complete recovery could be achieved by 6 months postoperatively.

FLAx‐REinforced Aluminum (FLARE): A Bio‐Based Fiber Metal Laminate Alternative Combining Impact Resistance and Vibration Damping

Fiber metal laminates (FMLs) have mainly been used in aerospace applications with synthetic fibers. To improve their environmental credentials and address issues regarding the end‐of‐life of these materials, a shift to FMLs based on natural fibers can be a promising course of action. However, regarding them as conventional FMLs overlook some of the unique benefits of natural fibers. Therefore, this study pioneers the examination of FLAx‐REinforced aluminum (FLARE) for its combined impact resistance and vibration damping. Dynamic mechanical analysis and vibration beam tests demonstrate that the metallic layer predominantly influences the damping behavior of FLARE. The loss factor notably decreases with aluminum addition (by 80% compared to the flax composite), approximated via an inverse mixture rule. Low‐velocity impact tests highlight the role of aluminum layers in energy absorption and the composite strength as a critical factor in impact resistance. FLARE exhibits 25% less specific energy absorption compared to its glass fiber counterpart. A quasi‐static analytical model suggests the potential of FLARE for practical applications. With its balance of properties and considering its potential advantages at end‐of‐life, allowing recycling of aluminum, and its expected lower carbon footprint, FLARE renders potential beyond the aerospace sector, e.g., in other forms of transportation.

Mechanical, durability and microstructural properties of waste-based concrete reinforced with sugarcane fiber

Extensive research has focused on producing sustainable concrete by exploring waste and recycled materials as alternatives to virgin substances. However, waste-based concretes often exhibit inferior durability and mechanical performance compared to traditional concrete. Incorporating reinforcement agents can enhance their performance. This study investigates the use of sugarcane fiber as a reinforcement in waste-based concretes containing fly ash (FA), ground granulated blast furnace slag (GGBS), and recycled concrete fine and coarse aggregates (RFA and RCA). Five dosages of sugarcane fibers (0 %, 1 %, 2 %, 3 %, and 4 % by fine aggregates mass) were examined. Mechanical and durability tests, including compressive strength, flexural strength, water absorption, and chloride ion penetration, were conducted. Scanning electron microscopy and micro-porosity analysis were employed for further assessment. Results show that adding sugarcane fiber enhances the waste-based concrete properties, with 3 % being the optimal dosage. This dosage improves compressive strength by 16 %, flexural strength by 35 %, flexural load bearing capacity by 34 %, energy absorption by 107 %, and toughness index by 6 %, while reducing water absorption by 4 % and chloride ion penetration by 23 %. Further increases in fiber dosage decrease concrete properties. The enhanced behavior is attributed to reduced porosity, refined pore structure, and reduced microcrack propagation. This study underscores the potential of incorporating sugarcane fiber along with waste materials to develop eco-friendly composites, aiming to mitigate carbon dioxide emissions and address environmental concerns.

Experimental Assessment of Hemp Shiv and Green Adhesives to Produce a Biocomposite Material.

This study investigated the utilization of innovative green composites made from hemp shiv, a waste by-product of hemp cultivation, with the aim of promoting sustainability within the construction industry. The manufacturing method involved the application of pressure in a mold to create the samples. These materials were produced using an environmentally friendly binder consisting of colophony, arabic gum, and corn starch. Moreover, white glue and bioepoxy were also used to compare with the green resins. Three different binder compositions were used for the specimens. The samples underwent mechanical testing through tensile and bending assessments, and their performance was compared to that of non-green binders to validate the effectiveness of the manufacturing processes. The study revealed that decreasing the moisture content during the curing process was crucial for improving the mechanical properties. The best results were achieved when using arabic gum as a binder, yielding a tensile strength of 2.16 MPa and a bending strength of 5.25 MPa, with a composition of 62.5% hemp shiv and a manufacturing process involving a pressure of 5 MPa.

The use of fully threaded headless cannulated screws for femoral neck fracture fixation in small-breed dogs show promise in cadaveric study.

To biomechanically evaluate the stability of internal fixation methods for femoral neck fractures in small-breed dogs. Furthermore, the possibility of replacing the headed screw with fully threaded headless cannulated screws in the fixation method was assessed. The study was conducted from December 12, 2023, to February 7, 2024. A total of 18 femurs from 9 canine cadavers were used in this study. After a simple neck fracture was created, in group A (n = 6), the fracture was stabilized with three 1.1-mm parallel Kirschner wires (K-wires). In group B (n = 6), a 3.0-mm partially threaded cannulated screw and an antirotation pin were used. In group C (n = 6), a 2.5-mm fully threaded headless cannulated screw and an antirotation pin were used. A mechanical test was conducted to apply a single axial compressive load to the femoral head. 9 adult small-breed dogs weighing 3.6 to 8.3 kg (mean ± SD; 5.9 ± 1.6). The mean maximum failure load was highest in group C (495 ± 81 N), followed by group B (454 ± 50.4 N), and then group A (222 ± 21.6 N). Significant differences in maximum failure load were observed between groups A and B as well as groups A and C but not between groups B and C. The use of fully threaded headless cannulated screws presents a promising method for internal fixation of canine femoral neck fractures. To demonstrate the potential stability and reliability of fully threaded headless cannulated screws.

Regional cultural inclusiveness and firm performance in China

As society continues to develop, a growing body of research is focusing on how informal institutions, such as culture, influence corporate behavior and economic outcomes. The aim of this study is to explore the impact of cultural inclusiveness, as a non-formal institution, on firm performance. Using Chinese A-share listed firms as our sample, we employ econometric methods to analyze the relationship between cultural inclusiveness and firm performance. Our findings reveal that cultural inclusiveness enhances firm performance, particularly evident in regions with higher levels of cultural inclusiveness, where firms tend to exhibit higher return on equity. To address concerns of endogeneity, instrumental variable regression using regional topographical changes is employed. Mechanism testing indicates that cultural inclusiveness primarily improves firm performance by reducing financial constraints and optimizing employee structure. Additionally, the study finds that cultural inclusiveness has a more pronounced impact on firms with higher corporate social responsibility (CSR) performance as well as those with greater investment in research and development (R&D). This study provides a comprehensive empirical explanation of how cultural inclusiveness influences the sustainable operation of businesses.

The Impact of Cashew Nut (Anacardium occidentale) Testa Tannin Feeding Ratio on the Chemical and Mechanical Characteristics of Leather Tanned from Cowhide, Goatskin and Sheepskin

In recent years, there has been a growing interest in exploring natural alternatives to synthetic tannins, driven by concerns over sustainability and environmental impact. Natural tannins offer several advantages, including biodegradability, renewability, and lower environmental impact compared to synthetic chemicals. Among the natural tannins under investigation, cashew nut testa tannin has emerged as a promising candidate due to its abundance, renewability, and potential benefits in leather tanning applications. This research investigated the impact of varying feeding ratios of cashew nut testa tannin on the chemical and mechanical characteristics of leather tanned from cowhide, goatskin, and sheepskin. The objective was to determine how different concentrations of cashew nut testa tannin influence the quality and performance of the leather. Leather samples were prepared using different feeding ratios of cashew nut testa tannin and subjected to a series of chemical and mechanical tests. The results indicated that the absorption of tannin and the resultant chemical stability varied with the type of hide or skin, with each exhibiting unique optimal ratios for tannin uptake. Higher tannin ratios generally improved the tensile and tear strength of the leather across all types, with significant enhancements noted in goatskin and sheepskin. However, an increase in tannin ratio reduced the flexibility of cowhide, while goatskin and sheepskin maintained adequate flexibility. The study demonstrates that cashew nut testa tannin is an effective and sustainable tanning agent, capable of producing quality leather. The findings suggest that the leather industry can utilize cashew nut testa tannin to enhance leather properties, with potential customization of tannin feeding ratios to meet specific performance requirements. Further research is recommended to explore long-term durability and economic viability on a commercial scale. This study contributes to the development of eco-friendly tanning practices and provides insights into optimizing the use of cashew nut testa tannin for various types of leather.

Under the Goal of Sustainable Development, Do Regions with Higher Energy Intensity Generate More Green Innovation? Evidence from Chinese Cities

Sustainable development is a global focal point. This study aims to analyze the relationship between energy intensity and green innovation using panel data from 285 Chinese cities spanning from 2003 to 2019. The novel element of this research is the first-time exploration of green innovation through the lens of local industry attributes. It explains the impact of energy intensity on the development of green innovation. By employing a two-way fixed-effect model, the regression analysis reveals that higher energy intensity in cities negatively influences green innovation. Robustness and mechanism tests indicate that in regions with higher energy intensity, governments issue more policies to encourage enterprises and research institutions to pursue green innovation. However, these regions have developed significant path dependence, and local enterprises are reluctant to increase green investment even when facing stringent regulations. Heterogeneity analysis proves that cities with higher levels of digitalization, R&D investment, urbanization, and per capita GDP exhibit an increase in green innovation. The research and findings of this study are of significant importance for policy and strategy formulation, allowing governments and enterprises to develop targeted economic strategies to improve energy efficiency and promote green innovation, thereby achieving sustainable development goals. Potential limitations include data quality, and some key information is difficult to obtain from public sources due to confidentiality, which may result in limitations and biases in the results.

Joint Quality Assessment of Ultrasonic Metal Welded Parts by Fracture Surface Evaluation

In ultrasonic metal welding, low specific resistances and large joining surface cross-sections require the use of mechanical testing to quantify the joint quality. In this study, different quality features of ultrasonically welded joints made of pure copper sheet are investigated during the successive phases of joint formation. Two test series with different workpiece geometries are examined. It is shown that mechanical quality features such as shear and peel forces behave differently over the formation of the joint and are not transferable. As an alternative to these, laser scanning microscopy is used to record images of the fracture surface that describe the growth of the joint area during formation. The study finds that shear tensile force growth and joint area growth are non-linear and comparable, with optimized welds achieving joint areas of 30 mm2 out of 64 mm2 and 6 mm2 out of 16 mm2. Although overall quality increases with increasing welding time, the material strength in the joint zone decreases. Depending on the original rolling condition, between 43% and 59% of the original material strength can be identified as the joint strength. The automatic analysis of fracture images is a suitable alternative to mechanical testing for similar joints.

Effect of glass and nylon fibers on drying shrinkage of alkali activated blast furnace slag mortars

The environmental consequences of Portland cement (PC) manufacturing have prompted the exploration of alternative binders, such as the alkali activation of blast furnace slag (BFS), which is generated as a byproduct during the extraction of iron. While alkali-activated blast furnace slag (AAS) binders have some benefits over regular PC binders, they also suffer from disadvantages such as significant drying shrinkage. The study investigated the impact of Na dosage and curing conditions on alkali-activated blast furnace slag mortar (AASM). The consistency of the specimens was tested for fresh, hardened properties, and was conducted. The optimum Na dosage and curing conditions were selected. In the second stage, 0.1% and 0.2% glass and nylon fibers were added to the selected optimum mortar. Consistency, fresh, mechanical, and durability properties tests were conducted on the fiber mortars. The results showed that increasing the Na content increased the compressive and flexural strengths of AASM specimens. Thermal curing provided high compressive and flexural strengths, whereas fiber addition reduced water absorption and drying shrinkage. The drying shrinkage value was reduced by 26.82 % for AASM specimens with 0.2 % nylon fibers by volume compared to AASM without fibers.

An enhanced and rapid method for von Willebrand factor multimer analysis for mechanical circulatory device testing.

Von Willebrand factor (VWF) is a critical glycoprotein in hemostasis and is an important factor in diagnosing bleeding disorders. Albeit the analysis of VWF is often compromised by inconsistent methodologies and challenges quantifying multimeric size. Current VWF multimer analysis methods are costly, time-consuming, and often inconsistent; thus, demanding skilled professionals. This study aimed to streamline and optimize the VWF multimer analysis technique, making it more efficient and reproducible, particularly for identifying or predicting mechanical circulatory support (MCS) induced bleeding disorders. Blood samples from healthy volunteers were exposed to high shear forces via a Medtronic HeartWare ventricular assist device. VWF multimers were analyzed using vertical-gel agarose electrophoresis and Western blotting. Differences in VWF distribution were determined using densitometry, and two methods of densitometric analysis were compared: proprietary software against open-source software. Using the developed method: (i) protocol duration was accelerated from three days (in classical methods) to ~ eight hours; (ii) the resolution of the high molecular weight (HMW) VWF multimers were substantially improved; and (iii) densitometric analysis tools were validated. Additionally, the densitometry analysis using two software types showed a strong correlation between results, with the proprietary software reporting slightly higher HMW VWF percentages. This methodology is recommended for affordable, accurate, and reproducible VWF multimer evaluations during MCS use and testing. Further research comparing this method with semi-automated methods would provide additional insight and improve inter-laboratory comparisons.

Estimation of mode I fracture toughness of rocks exposed to different environmental conditions using simple and linear multiple regression

AbstractMode I fracture toughness (Kıc) is a critical parameter in rock mechanics that is essential for understanding how rocks behave under tensile loading and crucial for applications ranging from safety assessments to structural design in geotechnical engineering. This study comprehensively investigates the influence of various environmental conditions (dry, saturated, frozen, thermal shock and thermal aging) on the physico-mechanical properties and Kıc of rocks. The primary novelty of this study lies in its comprehensive modeling approach under diverse environmental conditions, providing a nuanced understanding of factors influencing rock fracture toughness. By extending analysis to less-studied conditions such as freezing and thermal shock cycles, the study enhances the predictive capacity of fracture toughness models in practical geotechnical applications. Physico-mechanical properties, including uniaxial compressive strength, point load strength, Brazilian tensile strength (BT), Schmidt hardness, and ultrasonic wave velocity were evaluated across different environmental scenarios. Simple and linear multiple regression models were developed using these properties to predict Kıc. Notably, BT emerged as a significant predictor in the simple regression analyzes. Ten linear multiple regression models were formulated using SPSS 20, combining mechanical tests (UCS, BT, PL) with non-destructive testing methods (Vp, Vs, SH), demonstrating robust predictive capabilities with R2 values exceeding 0.95. Performance metrics (mean absolute error, mean absolute percentage error, root mean square error) were used to verify the accuracy of the model.