Flexural Yield Strength Research Articles

Microstructure and Mechanical Properties of Multilayered Ti-Based Bulk Metallic Glass Composites Containing Various Thicknesses of Ti-Rich Laminates.

In order to optimize the balance between strength and toughness, a series of multilayered Ti-based bulk metallic glass composites (BMGCs) with varying thicknesses of Ti-rich layers were successfully fabricated. The findings reveal that with an increase in the thickness of the Ti-rich layers, both the flexural yield strength and ultimate strength decreased from 2066 MPa and 2717 MPa to 668 MPa and 1163 MPa, respectively. Conversely, there was a noticeable increase in flexural strain. The fracture toughness of these multilayered Ti-based BMGCs decreased as the thickness of the Ti-rich layers increased; nevertheless, it stabilized at approximately 80 MPa·m1/2 when the thickness reached 100 μm. It was observed that a shift in the dominant deformation mode may be accountable for this phenomenon. These noteworthy characteristics suggest that adjusting the thickness of Ti-rich layers in multilayered BMGCs can effectively optimize mechanical performance, shedding light on the manufacturing of novel BMGCs with high performance.

Functionalization of calcium-deficient nanohydroxyapatite improves the mechanical properties of 3D printed biopolymer nanocomposites

Agglomerations of nanoparticles in a polymer matrix can drastically reduce the mechanical properties of a polymer nanocomposite, especially its strength. The grafting of nanoparticle surfaces with suitable functional groups can provide improved dispersion and stronger interfacial bonding, improving the fracture resistance of the nanocomposite. In this study, calcium-deficient nanohydroxyapatite (nHA) particles were functionalized with an amino acid-based urethane methacrylate (lysine urethane methacrylate, LUM) and subsequently reacted with hydroxyethyl methacrylate. We mixed these functionalized nHA particles with resin, composed of methacrylated acrylated epoxidized soybean oil, methacrylated isosorbide, and triethylene glycol dimethacrylate, and 3D-printed nanocomposites using masked stereolithography. We hypothesized that the functionalized nanoparticles would enhance the mechanical performance of the 3D-printed nanocomposites due to the greater dispersion and stronger interface. Flexural, tensile, compression and Mode-I fracture toughness test specimens were fabricated using a mSLA printer and tested following ASTM standards. The LUM functionalization of nHA improved the dispersion and increased the viscosity of the uncured nanocomposite ink. The flexural fracture strength, yield strength, and mode-I fracture toughness values were increased by 10 %, 30 %, and 11 %, respectively. The LUM improved the strength and fracture toughness by providing a stronger, more stable interface, resisting debonding between the matrix and particles, allowing for greater plastic deformation.

Optimizing the selection of natural fibre reinforcement and polymer matrix for plastic composite using LS-SVM technique

The manufacturing sector is paying close attention to plastic matrix composites (PMCs) reinforced with natural fibres for improving their products. Due to the fact that PMC reinforced with naturally occurring fibres is more affordable and has superior mechanical qualities. Based on the application material requirements, An important step in the production of PMC is choosing the right natural fibres for reinforcing and determining how much of each. This investigation aimed that Artificial Intelligence (AI) or soft computing based approaches are used to determine the right amount of natural fibres in PMCs to make the manufacturing process simpler. However, techniques in the literature are not concentrated on finding suitable material. Hence in this investigation, a local search with support vector machine (LS-SVM) optimization technique is proposed for the optimal selection of appropriate proportions of suitable fibres. Modelling of the Proposed LS-SVM Optimization was demonstrated. In this proposed technique around four kinds of polymers/plastics and 14 natural fibres are considered, which are optimized in various proportions. The optimization performance is evaluated based on the tensile strength, flexural yield strength and flexural yield modulus. The proposed LS-SVM Optimization was evacuated by developing solutions for medical applications (Case 1), Transportation applications (Case 2) and other notable applications (Case 3) in terms of tensile and flexural properties of the material. The maximum flexure stress in case 1, case 2, and case 3 is observed as 53 MPa, 45 MPa and 26 MPa respectively. Similarly, the maximum flexure stress in case 1, case 2, and case 3 is observed as 53 MPa, 45 MPa and 26 MPa respectively. Hence the proposed method recommended for choosing optimal decision on the choice of fiber and their quantity in the composite matrix.

Characteristics estimation of natural fibre reinforced plastic composites using deep multi-layer perceptron (MLP) technique

Polymer Matrix Composite (PMC/Plastic Composite) often referred to as Plastic Composite with Natural fibre reinforcement has a huge interest in industries to manufacture components for various applications including medical, transportation, sports equipment etc. In the universe, different types of natural fibres are available which can be used for the reinforcement in PMC/Plastic Composite. So, the selection of appropriate fibre for the PMC/Plastic Composite/Plastic composite is a challenging task, but it can be done using an effective metaheuristic or optimization techniques. But in this type of optimal reinforcement fibre or matrix material selection, the optimization is formulated based on any one of the parameters of the composition. Hence to analyse the various parameter of any PMC/Plastic Composite/Plastic Composite without real manufacturing, a machine learning technique is recommended. The conventional simple or single-layer machine learning techniques were not sufficient to emulate the exact real-time performance of the PMC/Plastic Composite. Thus, a deep multi-layer perceptron (Deep MLP) algorithm is proposed to analyse the various parameter of PMC/Plastic Composite with natural fibre reinforcement. In the proposed technique the MLP is modified by including around 50 hidden layers to enhance its performance. In every hidden layer, the basis function is evaluated and subsequently, the sigmodal function-based activation is calculated. The proposed Deep MLP is utilized to evaluate the various parameters of PMC/Plastic Composite Tensile Strength, Tensile Modulus, Flexural Yield Strength, Flexural Yield Modulus, Young's Modulus, Elastic Modulus and Density. Then the obtained parameter is compared with the actual value and the performance of the proposed Deep MLP is evaluated based on the accuracy, precision, and recall. The proposed Deep MLP attained 87.2%, 87.18%, and 87.22% of accuracy, precision, and recall. Ultimately the proposed system proves that the proposed Deep MLP can perform better for the prediction of various parameters of PMC/Plastic Composite with natural fibre reinforcement.

Evaluation of the flexural strength of metal frameworks fabricated by sintering-based computer-aided manufacturing methods

Statement of problemSintering-based computer-aided metal manufacturing strategies have been proposed as an alternative to hard metal milling. While these fabrication methods have been evaluated in terms of marginal and internal discrepancies and bond strength to porcelain, limited information on metal frameworks is available regarding their flexural yield strength. PurposeThe purpose of this in vitro study was to evaluate the flexural yield strength of 3-unit cobalt-chromium (Co-Cr) metal frameworks fabricated by hard metal milling (HMM), presintered soft metal milling (PSMM), and direct metal laser melting (DMLM) with 25-μm and 50-μm layer thicknesses. Material and methodsThree-unit master metal die models were prepared. A total of 40 metal frameworks (n=10) were fabricated by using HMM (group HM), PSMM (group PSM), and DMLM with 25-μm (group LM25) and 50-μm layer thicknesses (group LM50). Metal frameworks were cemented to the master die and then subjected to a 3-point bend test. The flexural yield force was used to calculate the flexural yield strength. The data were statistically analyzed (α=.05). One metal framework from each group was evaluated with scanning electron microscopy for microstructural analysis. ResultsThe group LM50 exhibited the lowest significant (P<.001) flexural yield strength values. The group HM exhibited higher flexural yield strength values than the other groups. No significant difference was found between the groups LM25 and PSM (P=.954) or between the groups PSM and HM (P=.111). ConclusionsThe fabrication method significantly affected the flexural yield strength of metal frameworks. Metal frameworks fabricated by DMLM with a 50-μm layer thickness exhibited considerably lower flexural yield strength values.

Development and Experimental Validation of Dissipative Embedded Column Base Connections for Enhanced Seismic Performance of Steel Moment-Resisting Frames

This paper proposes a novel embedded column base (ECB) connection that defies the current paradigm in capacity-designed steel moment-resisting frames (MRFs) where column bases have been traditionally considered as nondissipative. In the proposed concept, a dissipative zone is introduced as part of the embedded portion of the steel column. This zone features a reduced cross section and is decoupled from the concrete footing with a debonding material layer. The surrounding concrete effectively restrains the embedded section against nonlinear geometric instabilities, thereby retaining simplicity in the design process. Large-scale experiments suggest that, contrary to its conventional counterpart, the proposed dissipative ECB connection exhibits a stable hysteretic response until large lateral drift demands (i.e., 7% rad). It is also demonstrated that the dissipative ECB connection is resilient to local buckling-induced axial shortening, such that it lowers the repairability needs of slender wide-flange steel columns after earthquakes. Column twisting is also minimized throughout the loading history. The results indicate that both the elastic stiffness and flexural yield strength of the proposed ECB connection can be analytically derived for potential use in engineering design. It is found that a simple nondegrading bilinear model suffices to describe the hysteretic response of the proposed ECBs for performance-based assessment of steel MRFs.

Assessing the properties of Poly(dicyclopentadiene) reinforced with discontinuous carbon fibers

Ring-opening metathesis polymers (ROMPs) have remarkable toughness usually failing in a ductile rather than brittle manner. Despite these advantages, these resins have rarely been evaluated in composite materials. We investigated composites of milled carbon fiber and poly(dicyclopentadiene) (pDCPD), a common and inexpensive ROMP polymer. We observed that 10 wt% fibers gave significant increases in tensile modulus (137%), compressive modulus (34%), and fracture toughness (54%) with significant decreases in tensile (42%) and flexural yield strength (46%). Compressive yield strength, ultimate tensile strength, and flexural modulus remained about the same as the unfilled resin. The increases in modulus were well fit by the rule of mixtures for randomly distributed fibers even though microcomputed tomography data showed local regions of anisotropy due to stress applied during sample fabrication. Decreases in tensile and flexural yield were possibly due to weak interfacial strength arising from a lack of surface treatment on the carbon fiber.

The influence of the addition position of cellulose nanofibers on the crystalline and mechanical properties of carbon fiber-reinforced polypropylene composites

ABSTRACT The introduction of nanofillers into conventional microsized fiber-reinforced plastic composites has great potential to improve the fracture toughness and crystalline properties of composites, especially for semicrystalline thermoplastic polymers. Although the selective reinforcement is possible by nanofiller addition, the influence of the addition position of nanofillers on the mechanical properties and crystalline properties still has not been revealed. In this work, the cellulose nanofibers (CNFs) as the secondary filler were added (i) into a polypropylene (PP) matrix by a melt-mixing process and (ii) onto a carbon fiber (CF) surface by a dip-coating process in a CF-reinforced PP composite. By focusing on the transcrystals surrounding CFs, which enable improvement of the interfacial strength, the crystalline properties and mechanical properties were investigated through polarized optical microscopy, differential scanning calorimetry, X-ray diffraction, and 3-point bending tests in this study. We revealed that (i) CNF addition into the PP matrix disturbed the transcrystallization surrounding CFs and that the mechanical properties slightly decreased. Conversely, (ii) CNF addition onto the CF surface promoted transcrystallization surrounding the CF, and the flexural yield strength and modulus significantly improved by a maximum of 30% and 63%, respectively.

Effects of particle size of hydroxyapatite on mechanical property and cytocompatibility of hydroxyapatite/poly(amino acid) composites

AbstractIn this work, three different particle sizes of hydroxyapatites (HA) were synthesized, and these three types of HA were combined with poly(amino acid) (PAA) to form composites (PAA/HA) by phase separation technique. XRD, FT‐IR, SEM, EDS, and XPS analyses were utilized to characterize the structure and morphology of the synthesized three HA particles and composites. Results revealed that HAs with three different particle sizes (short rod (HA1), long rod in nanoscale (HA2), and long rod in micron level (HA3)) were successfully prepared and there was an interface interaction between PAA and HA in composites. Mechanical tests showed that the difference of HA in size played an important role in mechanical performance of the composites. Furthermore, the long rod nano‐HA showed the highest enhancement in flexural yield strength at 81.3% for PAA/HA2 compared with pure PAA. After 28 days of immersion in PBS, PAA, and its composites showed good stability, and the mechanical performance of all composites were remained unchanged. The cell culture results showed all composites were cytocompatible, cells attached on the materials well with excellent morphology. Thus, it could be concluded that particle size influenced mechanical properties of PAA/HA composites, without impacting their cytocompatibility and degradation behavior.

Strength prediction in single beads of large area additive manufactured short‐fiber polymers

AbstractThe use of fiber reinforcement in large area additive manufactured components is of industrial interest due to the ability to enhance the structural properties of final processed parts. This work presents a methodology to predict the tensile, compressive, and flexural yield strength of single beads of a large‐scale, 3D printed, short‐fiber reinforced material. The methodology is built on the strength theory of Van Hattum and Bernardo, which combines the Tsai‐Wu failure criteria with Advani and Tucker's orientation averaging technique, allowing fiber orientation flow model results to serve as direct input into strength predictions. Visual advantages of the methodology such as the ability to plot spatially varying strength constants and failure plots are demonstrated. In addition, an analysis of the methodology's sensitivity to various parameters is conducted.

EVALUATION METHOD FOR ALLOWABLE SHORT-TERM FLEXURAL STRENGTH AND YIELD STRENGTH OF CONCRETE-FILLED STEEL TUBULAR BEAM-COLUMNS

According to the Recommendations for Design and Construction of Concrete Filled Steel Tubular Structures from Architectural Institute of Japan, the allowable short-term flexural strength (ASFS) can be used as the yield strength for the restoring force characteristics model of concrete-filled steel tube (CFST) members. Therefore, it is necessary to examine whether the ASFS can be appropriate as an alternative for the yield strength. Furthermore, as the ASFS is typically calculated using the superposition method, the value of the deformation at the superposed strength cannot be evaluated. To address these issues, in this study, numerical analysis was conducted on the moment-curvature relation of CFST column sections using the finite fiber method. The characteristics of the point of ASFS and evaluation method for flexural yield strength in a broad sense were examined using the slope factor and strength satisfaction factor methods. The corresponding slope factor is larger than the value (1/3) that is generally used for the yield strength definition. Therefore, using the ASFS is as the yield strength of the CFST section is reasonable. Additionally, the formula for the curvature at the ASFS was also proposed.

Environmental Hazards of Giant Reed (Arundo donax L.) in the Macaronesia Region and Its Characterisation as a Potential Source for the Production of Natural Fibre Composites.

This paper summarises the results obtained from the characterisation of giant reed (Arundo donax L.) plant and fibres. The research is part of a project developed in the Macaronesia region, of which the aim is to demonstrate the feasibility of using biomass from invasive plant species in the composites sector as a way of financing control campaigns and habitats conservation labours. An experimental procedure for the extraction of fibre bundles from this plant was developed, and the material obtained was characterised in terms of chemical composition, thermogravimetry and infrared spectra to evaluate its potential application in the production of polymeric composite materials as a strategy for the valorisation of residual biomass from this invasive species in Macaronesia. Thermoplastic matrix composites with fibre content up to 40 wt.% were produced and their mechanical properties under tensile, flexural and impact loading were determined. No references on the preparation of composite materials with polyolefin matrices and giant reed fibres have been found. Results obtained from mechanical tests show a good performance of the manufactured composites, with a significant increase in both flexural and tensile stiffness; the flexural modulus is almost tripled for PE-based composites and rises to 88% with respect to PP matrix. The ultimate flexural strength and the tensile and flexural yield strength are kept at acceptable values compared to neat polymer materials, although ultimate tensile strength and impact resistance are significantly affected when natural fibres are added.

Impact of hydration on the mechanical properties and damage mechanisms of natural silk fibre reinforced composites

Silk fibres exhibit good biodegradability, biocompatibility and balanced strength and toughness, which are useful for toughness/impact-critical composites in the biomedical field. However, the impact of hydration has not been studied for silk fibre-reinforced polymers (SFRPs). In this work, SFRPs fabricated vacuum-assisted resin infusion (VARI) were treated under three hydration conditions. A hydration condition of 40 °C at 89% relative humidity (RH) was sufficient to induce a reduction in the tensile and flexural modulus and yield strength of SFRPs. Acoustic emission (AE) analysis showed that interface failure played a key role in the damage modes of SFRPs. Although mild hydration treatment appeared not to affect SFRPs, high hydration led to more susceptible interfacial failure. This work is intended to reveal the structural mechanisms of SRPPs under hydration, and to provide a useful reference for potential biomedical applications.

Zr61Ti2Cu25Al12 bulk metallic glass under three-point bending: Characteristic of large-deflection deformation

With three-point bending (3 PB) approach, nonlinear large-deflection deformation in bending was investigated for Zr61Ti2Cu25Al12 (ZT1) metallic glass (MG) beams with varying thickness from 1 mm to 100 μm. It was shown that higher flexibility is achievable by increasing the span-to-thickness ratio, which is desired for flexible members subjected to large-deflection performance. Moreover, yielding event of the MG beams in large-deflection situation can be captured via a conversion of load-deflection response into the non-dimensional form. Meanwhile, intrinsic sources responsible for the buckling events can be justified in terms of theoretical analytical solutions in mechanics. With monotonic bending and nonlinear bending theory, flexural yield strength of ZT1 MG with a thickness of 100 μm was determined to be 2050 MPa. Its bending proof strength at 0.005% permanent strain (σp,0.005%) was determined to be 1900 MPa, indicating that the beam-thickness effect on σp,0.005% is absent at least when the thickness was reduced from 1 mm down to 100 μm. As noticed, the response at σp,0.005% physically correlates with the propagation stress of embryonic shear bands, instead of the nucleation stress. In comparison with the current candidate materials in compliant mechanisms, ZT1 MG exhibits significant advantages in the components that the large-deflection elastic bending and high elastic-strain energy storage are desired.

Mechanical Testing of Recycled HDPE Extruded Hollow Section

High density polyethylene (HDPE) is a thermoplastic polymer which is classified as one of the highly consumed types of plastics. One major advantage of thermoplastic materials is their ability of recycling and reprocessing which will bring considerable economicand environmental benefits. The present paper, therefore, endeavours to explore the practical possibility of using recycled HDPE hollow section as a replacement of virgin HDPE made by the extrusion process. The main focus of the study was to evaluate the mechanical performance of the recycled HDPE and compare the results with virgin or non-recycled HDPE. The modulus of elasticity, tensile yield and ultimate strength, compressive yield and ultimate strength, flexural yield and ultimate strength and the coefficient of thermal expansion were the main parameters to be checked against the respective mechanical properties. Thus, pursuant to the rsults, it was found out that the modulus of elasticity and the tensile yield strength are lower in recycled HDPE compared to the non-recycled HDPE. However, there is no significant difference between the recycled and non-recycled HDPE for the tensile ultimate strength, compressive yield strength and compressive ultimate strength. The flexural yield strength and flexural ultimate strength properties of the recycled HDPE proved to be superior to those of the non-recycled HDPE. The coefficient of linear thermal expansion of the recycled HDPE sample was 130 μm/(m.°C) and that for the non-recycled HDPE was 142 μm/(m.°C).

Towards selective laser sintering of objects with customized mechanical properties based on ANFIS predictions

Recently, the adaptive network-based fuzzy inference system (ANFIS) has been used extensively in modeling of manufacturing processes to save both optimization time and manufacturing costs. ANFIS is a powerful iterative tool for optimizing non-linear and multivariable manufacturing operations. In the present study, ANFIS is used to predict the optimum manufacturing parameters in selective laser sintering (SLS) of cement-filled polyamide 12 (PA12) composite. For this purpose, a set of cement-filled PA12 test specimens is manufactured by SLS technique with 8 different values of laser power (4.5–8 Watt) and 8 different weight fractions of white cement (5 %–40 %). Mechanical characterization of cement-filled PA12 is carried out to evaluate the ultimate tensile strength (UTS), compressive strength, and flexural properties. The experimental data are then divided into two groups; one group for training the ANFIS model and the other group for checking the validity of the identified model. The built ANFIS model was validated experimentally and comparison with experimental results revealed mean relative errors of 2.92 %, 3.84 %, 4.75 %, and 3.31 % in the predictions of UTS, compressive strength, flexural modulus, and flexural yield strength, respectively.

Experimental and theoretical study of seismic and progressive collapse resilient composite frames

A steel-concrete composite frame is typically used for building construction. Earthquake action and progressive collapse event caused by accidental local failures are the primary threats affecting the safety of steel-concrete composite frames. Currently, multi-hazard resistance and building resilience have garnered much research attention from the international civil engineering community. Based on the previously proposed first-generation seismic and progressive collapse resistant composite frame (SPCRCF), an improved second-generation seismic and progressive collapse resilient steel-concrete composite frame (SPCRCF-2) is proposed. The performance of SPCRCF-2 is compared with that of SPCRCF as well as a conventional steel-concrete composite frame (CSCCF) through seismic and progressive collapse experiments. Compared with CSCCF and SPCRCF, SPCRCF-2 is proven to be able to localize the damage to the replaceable energy-dissipating (ED) components under both seismic and progressive collapse conditions, whilst maintaining the other key components (beams and columns) damage-free. This special feature facilitates rapid repair of the structure thereby achieving multi-hazard resilience. Finally, theoretical models are proposed to calculate the initial stiffness and flexural yield strength of the beam-column joint connection in SPCRCF-2. The models are further validated by the experimental results.

Investigation on the effects of the processing parameters and the number of passes on the flexural properties of polymer nanocomposite fabricated through FSP method

Flexural properties calculation helps in designing structural elements like beam, cantilever and shafts. Moreover, the flexural properties are of vital importance in engineering and industrial applications such as joints replacements. The purpose of this investigation is to study for the first time, how the friction stir processing (FSP) parameters affects the flexural properties of UHMW-PE composites reinforced with nano particles. The tool rotational speed (ψ), tool feed rate (ƒ), volume percentage (ν) of nano powder and tool shoulder temperature (τ) are selected as the process parameters. The ultimate flexural strength (UFS) and flexural yield strength (FYS) are calculated from the flexural test stress-strain diagrams. The analysis of variance is conducted which reveals that the selected parameters are significant for both UFS and FYS. Macroscopic and microscopic study shows that the FSP parameters affects the mixing of the strengthening particles and hence the flexural properties of the composite. The combinations of low level of ν with medium level values of other parameters results in the highest flexural properties. Moreover, the combinations of higher levels of τ and ψ results in material degradation. At the end, optimum conditions for the highest flexural properties are sorted out and the effect of increasing the number of passes has been investigated which significantly improve the flexural properties of the composite material.

Thermal behaviour of TIG arc surfacing affecting mechanical properties of AISI 4340 steel substrate under static and dynamic loading

Surface modification of medium carbon AISI 4340 structural steel using TIG arcing process under various heat input (Ω) of varying arcing current (I) and arc travel speed (S) has been studied. Weld isotherm and thermal cycle of the fused zone has been analytically established and validated with experimentally measured results. TIG arcing process has been found to change the microstructural characteristics of the fusion modified matrix by transformation of fine niddle shape martensite, which has significantly enhanced its hardness from 256 ± 10 HV to 745 ± 8 HV and thus its mechanical properties. Formation of residual stresses in the surface modified the substrate is examined by hole drill method up to a depth of 1.3 mm. A residual stress of tensile nature is found to exist up to an appreciable depth from the top modified of the substrate, which has adversely affected its static and dynamic properties by enhancement of resolved stress in the matrix during the bend test. Surface modification improves flexural properties of the substrate with a maximum improvement of flexural yield strength at a relatively slow arc travel speed of 6 cm/min, while the Ω lies in the range of 0.6–1.21 kJ/mm. A favourable to improvement in static and dynamic properties of the substrate were found at relatively higher Ω of TIG arcing at slower S. It has primarily happened due to development of relatively slower cooling rate in the matrix introducing comparatively ductile lath martensite in it.

Coupled axial tension-flexure behavior of slender reinforced concrete walls

Reinforced concrete (RC) walls in high-rise buildings, in particular wall piers that form part of a coupled or core wall system, may experience coupled axial tension-flexure loading when subjected to lateral demands. The seismic behavior of RC walls with various axial tensile forces was investigated by quasi-static tests on four RC slender walls subjected to the combined tension and flexure loading. The failure modes, strength and deformation capacity, effective flexural stiffness, and design equations are presented. The failure modes included flexural-sliding failure and flexural failure. The effective flexural stiffness and lateral strength of the walls significantly decreased as the axial tensile forces were increased. The ACI 318-14 and ASCE/SEI 41-13 code provisions overestimated the effective flexural stiffness of RC walls subjected to axial tension. Although equations proposed by Paulay & Priestley and Adebar et al. consider the influence of axial forces, they were not able to accurately predict the effective flexural stiffness of the RC wall specimens subjected to tensile forces. Both sectional analysis using XTRACT and JGJ 3-2010 (China) code equations provided accurate estimation of the flexural yield strength of walls. Finally, both a refined model and simplified equation were proposed to estimate the axial elongation for RC slender walls subjected to axial tensile force and cyclic lateral loading.