Static Bending Tests Research Articles

Aspects Regarding Welding of DD13 Steel by Applying the FSW Process and some Processes Derived from it

Due to its characteristics, DD13 steel is recommended for various applications in the automotive field (including in the manufacture of components for car bodies). The paper presents solutions proposed by ISIM Timisoara for welding of DD13 steel, as alternative solutions to conventional welding processes. One solution that has proven to be viable for joining DD13 steel is the friction stir welding process (FSW). In terms of the quality of the welded joints obtained by applying the classic FSW welding process, these welds were excellent. In an attempt to obtain other benefits, mainly related to the efficiency of the welding process, ISIM Timisoara has developed research programs for the study and application of other methods based on the FSW process principle, namely: - hybrid friction stir welding ultrasonic assisted FSW-US; - friction stir welding in inert gas environment FSW – IG. The important effects due to the application of these methods are: improving (as appropriate) the degree of plasticization of the materials to be joined and increasing the degree of mixing of the materials as result of ultrasonic assistance of the FSW welding process; improvement of the welding process by reducing the pressing forces of the tool during welding, with an effect on increasing the service life of welding tool; respectively improving the aspect of the weld and some mechanical characteristics of the welded joints (at tensile tests, respectively static bending test). The obtained results showed that the two methods derived from the classical FSW welding process, can be used in industrial applications, with important benefits.

Effect of fatigue on tropical wood species

Abstract The aim of present study was to create a theoretical model that allowed, with security and reliability, to obtain values of strength and stiffness to which the structural element will be submitted throughout its useful life. The effect was studied for strength and stiffness properties, and the modulus of elasticity (EM) and bending strength (fM) on static bending test were evaluated according to the increasing number of cycles of the fatigue test for the five classes of hardwoods, recommended by NBR 7190 Standard Code. A reduction in strength and stiffness properties was observed with increasing loading Ncycles applied at two frequency levels. From the multivariate regression models and the respective determination coefficients, a generic model was obtained for the set involving the five wood species, emphasizing the insertion of the apparent density as an independent variable, which allowed a greater generalization of the use of the adjustments in the estimation of the EM and fM properties, presenting significant determination coefficients, ranging between 67.89% and 70.58%.

Friction Stir Welding in Inert Gas Environment (FSW-IG) of AZ31B Magnesium Alloy

Friction stir welding is an area of interest within ISIM Timisoara, several research projects that have addressed this issue being carried out. At ISIM the research started with the approach of FSW welding of some aluminum alloys (as similar and dissimilar materials) and later extended to other types of non-ferrous metallic materials (magnesium, titanium, copper alloys) and different types of steels respectively. New methods / possibilities of application of the FSW welding process were also researched. The paper presents results obtained by ISIM Timisoara within an ongoing national research project regarding the friction stir welding in inert gas environment (FSW-IG) of the AZ31B magnesium alloy. The experimental research aimed to perform a comparative analysis between the FSW-IG welding and the classic FSW welding for AZ31B magnesium alloy, in the same working conditions in terms of welding equipment, welding tools and technological process parameters. The obtained results show that the application of FSW-IG welding compared to the classic FSW welding brings benefits in terms of weld surface appearance, mechanical strength, elongation at break and behavior to the static bending tests.

Use of Carbon and Basalt Fibers with Adhesives to Improve Physical and Mechanical Properties of Plywood

Currently, wood is presented as an alternative to traditional building materials and to mitigate climate change. Chile is one of the eight largest wood producers in the world; therefore, wood-based products are an easily accessible resource. The aim of this research is to reinforce at laboratory scale plywood panels with basalt and carbon engineer fibers using epoxy resin and polyvinyl acetate as an adhesive system to improve their physical and mechanical properties. Three-point static bending and Janka hardness tests were carried out. The results showed a better performance in the reinforced boards, which showed an increase in Modulus of Elasticity (MOE) and Modulus of Rupture (MOR) properties in the parallel direction of about 48.2% and 52.8%, respectively. Additionally, for the perpendicular direction, there was an increase of 52.0% and 102.9%, respectively. On the other hand, the Fiber Reinforced Polymer (FRP) plywood panels showed an increase of at least 37% on the Janka hardness property, obtaining higher results with the polyvinyl acetate (PVA) adhesive. Finally, FRP–plywood, PVA–BF and PVA–CF may be a new option for composite wood materials, with their ductile behavior and superior mechanical properties, especially in the perpendicular direction, where the increases were greater than those shown in unreinforced plywood.

Use of the FMVSS-214 static bending test to evaluate an automobile side door impact beam made of glass fiber-reinforced plastic

A side door impact beam absorbs energy and plays an important role in preventing intrusion of another vehicle into the occupant area. Impact beams are being actively researched to reduce vehicle weight while still meeting the strength requirements of environmental regulations and to improve fuel efficiency and enhance safety. No study has subjected a lightweight glass fiber-reinforced plastic (GFRP) impact beam to the Body in White (BIW) Federal Motor Vehicle Safety Standard (FMVSS)-214 quasi-static test. We compared three beams that differed in shape and stacking pattern. We performed three-point bending analyses, bending tests (including after bracket tightening), and static bending tests of door assemblies. The best GFRP beam (B) and a steel model were compared in terms of BIW static bending performance. The front-door GFRP beam exhibited an average reaction force 135% of that mandated by the FMVSS-214S test specification, an intermediate average reaction force 158% of that required, and a final force 154% of that required. In terms of bending performance, the initial average reaction force was 9.5% higher than that of the steel impact beam, and the rear door force was 6.6% lower. The reaction force of the GFRP beam decreased rapidly as breakage occurred after bending through 110.0–120.0 mm; however, the average reaction force was similar to that of the steel beam. Thus, the GFRP impact beam met the legal requirements but weighed 30% less than the steel beam.

Impact of Pretreatment Decay on the Mechanical Properties of Wood Railroad Ties

Wood is the traditional material choice for railroad ties and one that is well-suited for the future. Wood railroad ties are preservative treated to ensure adequate service life. Borate treatment in combination with creosote or copper naphthenate (i.e., dual treatment) is a widely accepted practice. However, the timing of the borate treatment varies in different manufacturing processes and some ties are first treated only after the lengthy air-drying process. Before treatment, the wood is vulnerable to decay but there are limited data on the impact of pretreatment decay of wood railroad ties. This paper presents experimental testing to quantify the impact of pretreatment decay on the mechanical properties of wood railroad ties. Initial static bending and compression tests were performed on small clear samples subjected to different treatment schemes. Later testing included static bending, spike pull-out, and compression tests of full-size railroad ties. Several species were studied, including sweetgum and red oak, which are commonly used as railroad ties, and yellow poplar and southern yellow pine, which are not. Pretreatment decay resulted in as much as a 19% decrease in the average spike pull-out resistance and a 27% decrease in modulus of rupture in full-size ties. Degradation in mechanical properties from pretreatment decay was in some cases greater than the initial differences between species. The results of this study will enable more informed decisions to be made on the manufacture and use of wood materials in rail infrastructure and potentially enable the use of nontraditional abundant species.

A Proposed Method to Evaluate the Effect of Changing the Kerfing Parameters upon the Static Bending Behavior of Flexible Plywood Panels Cut by Laser

The purpose of this paper is to propose a method for testing the effect of varying the kerfing parameters, on the flexibilization of plywood panels for indoor applications. The evaluation was made by comparisons of the change in the MOE, MOR, and maximum deflection, between flexibilized and non-flexibilized specimens subjected to static bending tests based on EN 310. In order to prevent the problem of sliding from the supports occurring for the flexibilized specimens, the standard specimens were modified by adding a frame and subjecting to bending just their central rail. Framed specimens of poplar plywood, of 8 mm thick, were laser cut with a rigid central rail, taken as reference and with the flexible kerfed rail. These had lengths of the flexible area of 50, 70, 90, and 110 mm and with two dimensions of the kerfing pitch, 6 and 10 mm. Very good correlations were found for MOE, MOR, and maximum deflection with the length of the kerfed area, for both values of the kerf pitch, which proves the sensitivity of the proposed method to the changes in the input parameters. The method could further serve to mathematically model the flexibility of a kerfed plywood panel by selecting the appropriate input data.

Some Physical and Mechanical Properties of <i>Corymbia</i> Hybrid Wood

Corymbia hybrid is a fast growing inter-specific hybrid of tree species. Physical and mechanical properties of Corymbia hybrid were evaluated in present study. Results show that mean density of Corymbia is 0.71 g/cm 3 and it increases from pith to periphery. Mean radial and tangential shrinkage are 7.74% and 9.64% respectively. MoR and MoE in static bending test were found to be 895 kg/cm 2 and 80 x 103 kg/cm 2 . Maximum crushing strength in compression parallel to grain was 565 kg/cm 2 . Compressive stress at elastic limit in compression parallel to grain was 139.08 kg/cm 2 . Maximum shear stresses in radial and tangential directions were 127.11 and 132.22 kg/cm 2 . Screw holding capacity in transverse and longitudinal directions was 333.33 and 171.67 kg respectively. Nail holding capacity in transverse and longitudinal directions was 88.3 and 85 kg respectively. Hardness in radial and tangential directions was found to be 747.5 and 758 kg. The properties of Corymbia hybrid wood are comparable with structural timbers which indicate the suitability of the timber for load bearing columns, flooring and other similar purposes.

Preliminary Study on Mechanical Aspects of 3D-Printed PLA-TPU Composites.

Additive technologies using Fused Deposition Modeling (FDM) technology are currently a promising tool for the production of polymeric multicomposites. This paper presents the results of a static 3-point bending test carried out on 3D printed samples of the PLA-TPU composite. The article also discusses initial vibrodiagnostic research and Finite Element Method (FEM) analysis of the 3D-printed composite bushings. The data obtained from FEM analysis served as input data for motion simulation analysis, where the influence of the stiffness of the suspension on the trajectory has been verified.

Application of the Sinter-HIP Method to Manufacture Cr-Mo-W-V-Co High-Speed Steel via Powder Metallurgy.

1.2C–4Cr–4Mo–10W–3.5V–10Co–Fe high-speed steel (JIS SKH57; ISO HS10-4-3-10) is often manufactured via casting and forging. By applying powder metallurgy, the properties of the abovementioned material can be improved. In this study, the effects of sintering conditions on the formation of precipitates and pores are evaluated. Additionally, strength with and without hydrostatic pressure during sintering is evaluated via static bending and impact tests. Sintering via hot isostatic pressing (HIP) at 1463 K can effectively eliminate pores and prevent the coarsening of precipitates. Toughness and strength improved by 50% by applying HIP.

The Use of Artificial Neural Networks for Determining Values of Selected Strength Parameters of Miscanthus × Giganteus

The aim of this paper is to develop neural models enabling the determination of biomechanical parameters for giant miscanthus stems. The static three-point bending test is used to determine the bending strength parameters of the miscanthus stem. In this study, we assume the modulus of elasticity bending and maximum stress in bending as the dependent variables. As independent variables (inputs of the neural network) we assume water content, internode number, maximum bending force value and dimensions characterizing the cross-section of miscanthus stem: maximum and minimum stem diameter and stem wall thickness. The four developed neural models, enabling the determination of the value of the modulus of elasticity in bending and the maximum stress in bending, demonstrate sufficient and even very high accuracy. The neural networks have an average relative error of 2.18%, 2.21%, 3.24% and 0.18% for all data subsets, respectively. The results of the sensitivity analysis confirmed that all input variables are important for the accuracy of the developed neural models—correct semantic models.

Feasibility analysis of magnesium phosphate cement as a repair material for base slab of China railway track system II ballastless track

This study proposed using magnesium phosphate cement (MPC) to repair the base slab of the Chinese ballastless railway track. Laminated members were subjected to static and fatigue bending tests. Results showed that the damage to the laminated members was caused first by bending and then by horizontal shear at the interface between the old and new materials. Fatigue test results showed that the stress level on the base slab was below the endurance limit and thus should not cause failure. Microscopic tests also revealed that the bond between Portland cement and MPC played a crucial role in the repair process.

Influence of Preheating and Postweld Heat Treatment on the Structure and Strength of the Wire Frame Welded Joint Made of Spring Steel C62D

This article investigates the automatic welding of Ø4.5 mm high carbon steel wire frame. Using spring steel wire frame in car seat fabrication reduces its weight and helps to maintain rigidity. The thermal effect during the welding process can unacceptably deteriorate the mechanical properties of the material. It is proposed to use preheating and heat treatment to obtain a joint with required mechanical properties. To reduce of effect on entire product rigidity the thermal treatment was carried out locally in the zone of joining. Heating was carried out using a gas flame. Metallographic and microhardness measurements were used for the structural study. Mechanical properties were evaluated by static tension and free bending test. The recording of thermal cycles during the welding and heat treatment was carried out using chromel-alumel and tungsten-rhenium thermocouples.

A new methodology to predict moisture effects on mechanical behaviors of GFRP-BALSA sandwich by acoustic emission and infrared thermography

This work focuses on moisture effects on mechanical properties of GFRP-balsa sandwich structure experimentally and numerically. Firstly, relationships between Moisture Content (MC) and Acoustic Emission (AE) wave velocity have been demonstrated by Hsu-Nielsen tests during the water immersion tests. And then, a new methodology was proposed to predict the elastic modulus of skin of wet sandwich structure based on the relationship between MC, AE wave velocity and skin elastic modulus. Static 4-point bending tests were monitored by InfraRed Thermography (IRT) to verify the good consistency between bending stiffness reduction and elastic modulus prediction of wet sandwich by the new proposed method. Furthermore, Progressive Damage Analysis (PDA) model has been developed by introducing the modified elastic modulus, strength, as well as fracture energy of the wet skin, to quickly predict the bending stiffness, fracture load, displacement and damage evolution process of wet GFRP-balsa sandwich. Finally, it demonstrates that the damage localization by PDA model has a good concordance with the observations by IRT technique.

Large‐area, high‐temperature stainless steel foil substrate for manufacturing low‐cost and flexible CMOS polysilicon TFTs

AbstractA large‐area stainless steel foil substrate which is compatible with high‐temperature (>800°C) processing was developed to support a hybrid printed and conventional process technology to fabricate polysilicon thin‐film transistors (TFTs). The purpose was to build a platform that could lead to low‐cost, roll‐to‐roll manufacturing of polysilicon TFTs. To fabricate a self‐aligned top‐gate TFT structure, a screen‐printed dopant process, which requires high‐temperature activation, was developed to substitute capital‐intensive ion implantation. For the pilot line process, a 300‐mm2 and 100‐μm‐thick stainless steel substrate made of an alloy with a low thermal expansion coefficient (CTE) was chosen. Then, the foil finishing process was optimized to achieve flatness and minimize surface roughness. A barrier and dielectric encapsulation were developed to prevent trace metal diffusion from the substrate into the active layers. The polysilicon TFTs were then evaluated with static and dynamic bending tests.

A new method for estimating the bending stiffness curve of non-uniform Euler-Bernoulli beams using static deflection data

The static Euler-Bernoulli beam is a simplified model from linear elasticity theory for small deformations, with which the stresses and deflections of slender beams can be determined very well. The simplicity of Euler-Bernoulli beam theory makes it still an important tool in the sciences, particularly in construction and mechanical engineering. The behavior and the deflection of a static Euler-Bernoulli beam is completely given by the bending stiffness curve. The bending stiffness curve of a real beam structure can be determined using measured data from a bending test. However, the determination of the bending stiffness curve for non-uniform beams leads to a so-called inverse problem, which is ill-posed. In this work, a robust and computationally effective method for determining the bending stiffness curve of a non-uniform Euler-Bernoulli beam based on measured data from a static bending test and the calculus of variations is presented. With the calculus of variations, the complex optimization problem of the inverse problem is transformed into a boundary value problem, which is then solved by collocation with lower computational costs. In addition, the new method does not require the second derivative of the beam deflection and the problem of determining the bending stiffness at the boundaries does not arise, as with the traditional method. The new method to determine the bending stiffness curve of non-uniform beams is demonstrated in several test examples.

Flexural behaviour of geopolymer concrete beams reinforced with BFRP and GFRP polymer composites

The paper presents the experimental investigations on the flexural behaviour of geopolymer concrete beams reinforced with Basalt Fibre Reinforced Polymer (BFRP)/Glass Fibre Reinforced Polymer (GFRP) rebars and the effect of inclusion of the new adhesively bonded BFRP/GFRP stirrups. M30 grade geopolymer and conventional concrete beams with the dimension of 100 × 160 × 1700 mm were cast to investigae the flexural behaviour of BFRP/GFRP and steel bars. This study also examined the mode of failure, deflection behaviour, curvature moment capacity, crack width, pattern, propagation, strains and average crack width of the BFRP/GFRP bars with stirrups in the geopolymer concretes using a four-point static bending test. The results were compared to that of conventional steel-reinforced concrete, and it was found that the Basalt and Glass reinforced polymer beams demonstrated premature failure and sudden shear failure. Further, the FRP bars exhibited higher mid-span deflection, crack width and crack propagation than steel bars. Crack spacing of the FRP bars decreased with an increase in the number of cracks. The correlation between the load and the deflection behaviour of the beams was determined using statistical analysis of multi variables regression.

Particle image velocimetry and digital image correlation for determining the elasticity modulus in wood

Several non-destructive testing techniques have been improved and tested in recent years. The non-destructive testing techniques using particle image velocimetry (PIV) and digital image correlation (DIC) differ from conventional testing techniques, as they allow making measurements indirectly. In this study, the elastic modulus in wood beams of Eucalyptus grandis and Pinus oocarpa were determined using PIV and DIC. The application of PIV and DIC techniques occurred during the static bending tests, when the displacements were also measured by the conventional method. The applied load values allowed calculating the elasticity modulus. In all regions of analysis, the mean values of the elasticity modulus found by the DIC, PIV and conventional method are statistically equivalent. It is concluded that the PIV and DIC testing techniques can be used to determine mechanical properties of wood.

Mechanical behavior of tropical Glued Laminated Timber beams with fingers joints

This paper presents an experimental investigation on Glued Laminated Timber (GLT) beams made with two tropical woods species, for structural purposes. Two tropical wood species with different density and under-exploited were chosen. These are Dacryodes buettneri (Ozigo) and Pterocarpus osun (Padouk), Ozigo species was taken as a reference species. A Phenol Resorcinol Formaldehyde (PRF) adhesive resistant to harsh tropical environments was used for bonding. The static bending tests were conducted on beams compound of two and three lamellas with fingers joints. The aims of these tests were to determine the key mechanical parameters such as Module of Rupture (MOR) and the Module of Elasticity (MOE). Influence of the finger’s joints on the bending strength of the GLT beams is also investigated in this work. The results show that the position of lamella and finger joint has an impact on the loss of bending strength of the specimens tested, but they have no influence on their stiffness properties.

Shear strengthening of high strength lightweight SCC beams internally reinforced with GFRP bars and external CFRP strips

Last few years have seen a substantial growth in the development and application of lightweight concrete (LWC) due to its enhanced mechanical properties and economic benefits in comparison to conventional normal weight concrete (NWC). The use of LWC in infrastructure has been popularised, especially in long-span bridges and high-rise bridges due to its lower density, which significantly reduces the dead load on the structure. Carbon fibre reinforced polymers (CFRP) and glass fibre reinforced polymers (GFRP) have rapidly gained acceptance in the infrastructure industry for their desirable characteristics over traditional steel. Extensive experimental research has been carried out over to years to investigate the shear performance of externally strengthened NWC beams with CFRP (carbon fibre reinforced polymer) strips. However, very limited research has been conducted on the shear performance of GFRP reinforced LWC beams externally strengthened with CFRP strips. Therefore, the main objective of this experimental study is to investigate the shear performance of high strength lightweight self-compacting concrete (HLWSCC) beams reinforced with internal GFRP bars and strengthened with external CFRP strips. HLWSCC is the latest development in concrete technology that combines the benefit of LWC and self-compacting concrete (SCC). One control specimen and two shear deficient HLSCC beams were strengthened with CFRP strips in the shear span. The test variable studied was the strip orientation (u-wrap and 45°) and all beams subjected to static four-point bending test. Load-deflection response and failure modes were observed and recorded for all the tested specimen. CFRP strips has considerably increase the load carrying capacity of HLWSCC strengthened beam specimen. The percentage increase in nominal shear strength ranged from 58.7% to 73.4% over unstrengthened control specimen.