Base Metal Thickness Research Articles

A shell theory approach for the analysis of metal-FRP hybrid toroidal pressure vessels

This study focuses on the analysis of metal-FRP hybrid toroidal pressure vessels (TPV) using shell theory. The analytical approaches for the design of metal-FRP TPVs considering bending effects are currently not available. Invariably the designs are done based on the most simplified approach like linear membrane theory. In this work, a potential energy functional for the metal-FRP TPV considering the membrane and bending deformations is developed using Love's shell theory. The classical laminate theory is employed to determine the stresses/strains throughout the thickness of the FRP laminate. The Rayleigh-Ritz method is adopted to solve the proposed potential energy functional. A finite element analysis (FEA) is conducted using ABAQUS to validate the proposed analytical solution. In addition, a parametric analysis is carried out to understand the influence of various parameters viz. thickness of base metal, thickness of FRP, and ratio between radii of toroid and cross-section on bending deformations in the hybrid TPV. The results from the proposed solution are in good agreement with that from FEA. Therefore, the proposed solution can be used in the analysis and design of the metal-FRP TPV irrespective of any variations in the geometric parameters. It is found that the inclusion of bending deformations can improve the accuracy of solution and the bending deformations in the base metal decreases or become negligibly small with the increase in R/r ratio and thickness of FRP. The orientation of fibers can change the direction of failure in the base metal. The important design parameters that influence the yield pressure are thickness of base metal and FRP, orientation of fibers and R/r ratio.

Corrugated Structural Metal Decking System under Tensile Strength Test

Corrugated metal decking has been widely used in the construction industry for many years due to its benefits towards the sustainability, improve time performance of the projects and environmental aspects. This article includes the investigation of tensile strength and identify the failure behaviour of different corrugated surface profile of the metal decking that innovated for structural slab. Novelty of this research is the discovery of the tensile performance of a cold rolled corrugated metal decking profiles at various points of interest for a composite flooring system. Tensile strength specimen preparation complies with the ASTM E8 Standard. A total of 60 specimens with different thicknesses and different parts of metal deck have been tested by the universal testing machine (UTM). The findings on how Base Metal Thickness (BMT) affects the tensile strength and the unique roll formed of the corrugated metal decking system, with 0.75BMT & 1.00BMT, are discussed and analysed in this article. Results showed that the average tensile strength value for 0.75BMT and 1.00BMT from part A was 592.47MPa and 554.41MPa, respectively, and the metal decking is up to the designed strength and the unique roll forming embossment provides better bonding quality between concrete and steel to be used in the industry.

Flexural performance of concrete composite metal decking with different base-metal-thickness new smart system

Industrial Revolution 4.0 has led to the age of automation and industrialized building systems. Composite slabs gain its popularity in the modern construction industry due to its speed of construction and cost saving features with lightweight structure. However, from time to time the manufacturer will introduce new corrugated roll forming cold formed steel metal decking systems, which cause the end user to ponder if the product is up to desired performances. The aim of this research is to study the structural performance of SMARTDEK composite slab composed of 0.75 mm and 1.0 mm thickness compared to the conventional reinforced concrete slab under flexural strength, deflection, and failure mode. Concrete slab with thickness of 130 mm was constructed to uncover the ultimate load capacity of the slabs. The novelty of this research is the discovery of longitudinal shear resistance constant through derived equations and the new SMARTDEK profiled composite slab performs better than the conventional slab. Four-point flexural tests were conducted according to ASTM C293 standards to determine the performance of the slabs, and three linear variable displacement transducers (LVDTs) were used to determine the deflection of the slabs. Load-Deflection graphs were plotted for the specimens to determine the yielding point and ultimate point of the slabs. The composite slab with 1.0 mm Base-Metal-Thickness (BMT) had the highest ultimate strength at 75 kN, followed by the composite slab with 0.75 mm BMT at 65 kN, and finally the conventional slab at 39 kN. The failure mode of the conventional slab was pure flexural; while the composite slab first failed in flexural, followed by longitudinal slip failure due to flexural and flexural-shear cracks, which disabled the composite action between the concrete slab and metal decking. The finding showed that the increasing thickness of the metal decking improves the slab strength which results in higher ultimate strength and reduces the overall deflection of the slab. Moreover, the breakthrough of this research is that increasing the overall thickness of the slabs increases the performance in loading’s capacity which could result in higher ultimate strength.

A theoretical solution for metal-FRP hybrid toroidal pressure vessel based on membrane approach

Metal-FRP (fiber reinforced polymer) hybrid circular toroidal pressure vessel (TPV) can withstand higher internal fluid pressure compared to a metal TPV of the same thickness. The design of hybrid metal-FRP TPV needs prediction of the stresses and strains induced in the base metal and FRP layers. Existing predictive models for metal TPV based on linear membrane theory are inadequate in obtaining non-singular displacements at the apex in the meridian of the TPV. Further, they are not applicable for metal-FRP TPV. Therefore, a theoretical solution based on a modified linear membrane approach is proposed for a metal-FRP hybrid circular TPV subjected to an internal pressure. The proposed solution is validated through numerical simulations based on three-dimensional finite element analysis (FEA). Subsequently, a parametric study is conducted to understand the effect of the CFRP’s modulus and number of layers, thickness of base metal and R/r ratio (radius of the toroid to its cross-section) on the behavior of the aluminium-CFRP hybrid TPV. The comparison of results in an illustrative case and parametric studies show that the predictions from the proposed model are in good agreement with FEA results.

Microstructure and Mechanical Properties Analysis of Mild Steel with Different Groove Shape Welded Using GMAW

This paper will discuss the effect of welding variables on the transverse tensile strength and hardness of mild steel welding made by GMAW. The welding variables included are base metal thickness, welding voltage, wire feed speed (WFS), and base metal groove shape. The results show that higher welding transverse tensile strength has obtained higher FZ hardness, while they both increased with decreased welding heat input. E.g., the highest tensile strength (238 MPa) has shown 2162 HV at 768 J/mm heat input, while the lowest tensile strength (120 MPa) of welding made at 2376 J/mm has shown 2108 HV. The FZ of welding made at V groove-shaped base metal has higher hardness and transverse tensile strength, as shown 2159.5 HV and 215 MPa in order when compared to 177 MPa and 2147 HV for X groove-shaped. The hardness at V groove-shaped FZ had an average of 2159.5 HV, while the hardness at X groove-shaped had an average of 2147 HV at 10 mm base metal thickness. The increased hardness of V groove-shaped FZ could be related to the increased stresses at V groove-shaped due to interpass heat input. The intricate physical shape of FZ and HAZ for X groove configuration possibly contributes to the lower transverse tensile strength of welding. A favorably increased hardness and transverse tensile strength are associated with softer and finer ferritic and perlitic grains in FZ and less dendritic perlite structure in HAZ. The Widmanstatten ferrite has contributed to decreased tensile strength.

Interface strength investigations of 304 stainless steel/T2 red copper T-type brazed joint based on cohesive zone model

Gas wave refrigerators are a type of refrigeration equipment with broad application prospects. The oscillating tube, its core component, was manufactured by brazing to improve production efficiency. To study the brazing interface strength, a small 304 stainless steel/T2 red copper T-type brazed joint specimen was designed. The tensile process of the brazed joint was simulated using ABAQUS software based on the bilinear cohesive zone model (CZM), and the results were compared with the experimental tensile results. Damage critical stress and critical fracture energy of = 40MPa and = 35 mJ mm−2, respectively, were obtained. A VUMAT subroutine was used to obtain the fatigue life of the specimen, and the errors with the experiment were 1.8% and 5.6%, respectively. It was proved that the CZM can simulate the tensile and fatigue loading processes of T-type brazed joints. The microstructure of the fatigue fracture of the specimen was analyzed using scanning electron microscopy. In addition, the effects of cyclic displacement and base metal thickness on the interface fatigue damage process were simulated and analyzed. The results showed that with an increase in cyclic displacement, the crack initiation life decreased and the crack growth rate increased; the interface damage, the crack length, and the fatigue load increased with the increase in base metal thickness.

Effect of GTAW on the Tensile Strength and Hardness of Mild Steel

Gas tungsten metal arc welding (GTAW) is used to study the effect of the base metal thickness, welding current and welding speed on the tensile strength and hardness of mild steel welding. The analysis found that base metal thickness had the highest effect and highest means of tensile strength and hardness of the welding. Taguchi’s design (TD) suggested using higher base metal thickness, lower welding current and higher welding speed when welding mild steel in order to obtain maximum tensile strength and hardness. The welding that has higher tensile strength showed higher hardness. However, the hardness increased proportionally with the increased internal stresses of the welding. The welding showed wider heat affected zone (HAZ) with the increase in internal stresses of the welding.

Effect of GTAW on the Mechanical Properties of Mild Steel

Tungsten metal arc welding (GTAW) is a highly popular welding technique in manufacturing. The welding factors such as welding current, voltage, speed, and gas flow rate play a significant role in determining the welding quality. This study discusses the effect of GTAW factors on the mechanical properties of commercial steel welding. Base metal thickness, welding speed, and current are the factors to be optimised for maximum tensile strength and hardness by Taguchi design (TD). The analysis showed that higher tensile strength welding has higher hardness. The increased tensile strength is obtained at increased base metal thickness, higher welding speed and lower welding current. In addition, higher tensile strength has been shown to obtain higher hardness—the higher hardness demonstrated at welding exposed to increased heat input that caused higher internal stresses. The higher base metal thickness obtained higher tensile strength due to the increased welding sample cross-section area and due to the phenomenon of the heat sink that minimised the effect of heat input and, thus, internal stresses. The welding made at 10 mm base metal thickness affected the results the most and obtained higher means, followed by samples fabricated at 150 A, while welding speed variation did not have much difference on the results. To obtain higher tensile strength, it is recommended to go for more increased base metal thickness, lower welding current, and faster welding speed when welding mild steel by GTAW.

A global thermo-mechanical model to mitigate welding residual stress and deformation in production of an aluminum bio-inspired AUV with a curved outside corner joint

Welding mechanics of large-scale complex-shaped structures is generally either disregarded or implicitly presumed due to high complexity and time consumption — even in the case of numerical analysis, typically it is limited to local thermo-mechanical models of straight butt or tee welded joints. Nevertheless, not only is this study aimed at presenting a time-saving global thermo-mechanical model of a curved outside corner joint but also at exploiting combined effects of welding parameters to mitigate deformation and residual stress. The global thermo-mechanical model is thereby constructed by combination of shell and solid finite elements providing Thermal-Elastic-Plastic (TEP) analysis for an aluminum Autonomous Underwater Vehicle (AUV) of which novel hull shape inspired by catfish morphology results in a longitudinal curved outside corner welded joint. A suitable polynomial mathematical function enabled the welding heat source to move steadily along the curved path of the joint. Saving up computational time 3.5 times greater than conventional full 3D method, the global shell/3D TEP FEM is validated well against experimental temperature, distortion and residual stress distributions when locating the boundary between shell and solid elements with the size of solid zone up to the 3 times thickness of base metal based on accuracy of molten metal penetration, deformation and residual stress prediction. A stark difference of about 120% in maximum amount of longitudinal residual stress is observed between global and local models. Finally, optimal outcomes are employed in production of the AUV so that 33% reduction in welding speed mitigated residual stress by 22% whereas welding length and sequence were more effective on distortion.

Effect of assembly margin on laser weld formation for niobium tungsten alloy

Based on the optimization experiment of laser welding process of niobium-tungsten alloy, the effects of assembly gap value and misalignment value on laser weld formation, microstructure and mechanical properties of Nb521 niobium-tungsten alloy were investigated by using variable gap method, equal gap method and equal misalignment value method. The results show that Nb521 niobium-tungsten alloy has good laser weldability. The maximum gap value margin of 1.0mm and 1.5mm thickness of base metal are about 22% and 10.6% of the base metal thickness, respectively. And the maximum misalignment value margin is about 30% and 33% of the base metal thickness, respectively. The welded joints are characterized by fine columnar crystal structure from the fusion zone to the center of the weld, and are little affected by assembly gap value and misalignment value. When the assembly gap value or misalignment value is not greater than the maximum margin, the welded joints are fractured in the base metal zone, which is far away from the weld. Therefore, the welded joints of Nb521 niobium-tungsten alloy by laser welding have excellent tensile mechanical properties at room temperature.

Effect of laser beam wobbling on the overlap joint strength of hot-press-forming steel over 2.0 GPa tensile strength

High-strength hot-press-forming (HPF) steel is extensively utilized in the automotive industry to lower the weights of car bodies. Resistance spot welding is commonly used when assembling car bodies; however, laser overlap welding is gradually replacing resistance spot welding owing to its high productivity and quality. The joint strength of laser overlap-welded HPF steel with a tensile strength of 2.0 GPa was investigated in the present study. Laser wobble welding was employed to increase the interface-bead width and the resultant joint strength. In laser overlap welding without wobbling, all the specimens were fractured at the interface during the tensile-shear test where the maximum load was 8.2 kN. An increase in the wobbling width not only induced an increase in the interface-bead width but also splitting of the weld bead. The interface-bead width (6.7 mm) was much higher than the base metal thickness (1.2 mm), with a wobble width of 1.6 mm. The wide interface-bead width resulted in a fracture load of 10.7 kN, and the fracture location moved from the interface to the upper plate. Laser wobble welding was confirmed to be an effective approach for increasing the joint strength in laser overlap welding.

Review and Feasibility Study on Micro Friction Stir Welding of Al/Fe Butt Joints

In the automobile industry, there is an increasing demand for Al/Fe dissimilar metal joining. Friction stir welding (FSW) is an efficient solid-state welding method to achieve high-quality Al/Fe dissimilar metal welding. Here, we reviewed the previous studies on butt FSW of thin Al/Fe sheets and conducted feasibility tests to investigate the applicability of micro FSW with a base material thickness of 1 mm or less. Most of the past literature, except for one study that adopted 1.12 mm-thick specimens, has worked with a base metal thickness of 1.5 mm or more. Selecting appropriate parameters can lead to a weld strength that is more than 90% of the base metal strength. Through feasibility tests on 2 mm-thick specimens, we could derive the welding conditions to obtain sound welds and the required joint strength. An adequate range (0.5-0.75 mm/rev) of advance per revolution was recommended to ensure the weld strength. A feasibility test on 1 mm-thick specimens revealed the possibility of melting of Al base metal during FSW of 1 mm-thin sheets; moreover, a low tool rotation speed was found to be crucial in ensuring the weld joint strength. The maximum weld strength for 1 mm-thick specimens was 200 MPa, which is 117% of the required weld strength. Key words: Dissimilar metal welding, Aluminum alloy, Steel, Micro friction stir welding, Joint strength

Static and fatigue performance of overlap welded thin plates

Thin-plate overlap welding is an important connection method for the automobile chassis structure. The fatigue performance of the chassis structural components depends mostly on the welded joints. A detailed understanding of its performance plays an important guiding role in the design of the chassis structure. This study was aimed at investigating the performance of thin-plate overlap welded structures using the static tensile test and fatigue test. The general rule of the influence of base metal thickness on the static strength and fatigue performance of welded joints was also summarized. The failure mode of the welded joint and the crack propagation mechanism were discussed in terms of fracture morphology. The findings might lay a foundation for the anti-fatigue design and lightweight design of the chassis welded structures.

Joint Quality Study of Self-piercing Riveted Aluminum and Steel Joints Depending on the Thickness and Strength of Base Metal

Joint Quality Study of Self-piercing Riveted Aluminum and Steel Joints Depending on the Thickness and Strength of Base Metal

Experimental study on peeling performance of T-type brazing joints

As a promising heat transfer component of high temperature gas cooled reactor (HTGR), the performance of the plate-fin heat exchanger determines the energy efficiency and life of the HTGR. Although the plate-fin structure has lots of advantages such as high efficiency, compact structure, low manufacturing cost, its performance is greatly affected by the vacuum brazing technology and harsh conditions, e.g. high temperature and high pressure. In the practical application, “peeling” failures may occur in the brazing joint between the fin and the parting sheet. It becomes necessary to characterize the strength of the joints. However, the standard specimen cannot accurately describe the real stress distribution. In the present study, a T-type specimen is designed for the peel test of brazing joints. To reflect the influence of brazing seams and thickness of the base metal, five specimens are designed and tested under 25 °C, 450 °C, 550 °C and 650 °C with five different applied loads, respectively. Based on the bilinear hardening model, the peeling performance of all T-type joints are obtained according to the tested peeling force-displacement curves. Then the influences of base metal thickness, brazing seam, loading rate and test temperature on the peeling performance are analyzed. The results show that the maximum peel force, the average peeling force and the fracture energy all decrease as the results of increased base metal thickness. With the increase of the filler thickness, the average peeling force and the fracture energy of the brazing joints both decrease. The joints with 0.95 mm base metal thickness and two layers of brazing filler metal are recommended for the peeling test of the T-type specimen. The loading rate of the peel test has no significant effect on the average peeling force and the fracture energy.

Experimental Study on Peeling Properties of T Type Brazing Joint

As the key component of the high temperature gas cooled reactor (HTGR), the performance of the plate fin heat exchanger determines the working efficiency and life of the HTGR. Although the plate-fin structure has lots of advantages such as high efficiency, compact structure, low manufacturing cost, its application will be affected by the vacuum brazing technology and harsh conditions, like high temperature and high pressure. In the practical application of plate-fin heat exchanger, the process of "splitting" between the fin and the diaphragm is very similar to that of the adhesive joint and the delamination of the composite. In the present study, a T-type specimen was designed for the the peel testing of brazed joints. Five kinds of specimens were designed based on the difference between the weld gap and the thickness of the sample base material. The tests were carried out under 450°C and 650°C at five kinds of loading rates, respectively. The peel force-displacement curves of standard samples were obtained . The maximum peel strength and average peel strength were calculated. In addition, the influence of base metal thickness, brazing gap, loading rate and test temperature on the maximum peel strength were analyzed by controlling variable method. Keywords: brazing joint; T-type peel test

Corrosion behavior of CLAM steel weld bead in flowing Pb-Bi at 550 °C

China Low Activation Martensitic (CLAM) steel was one of the Reduced-Activation Ferritic/Martensitic (RAFM) steels which were widely considered as the candidate structural metal for the new generation nuclear facilities. Flowing Pb-Bi corrosion tests of CLAM steel weld bead with Tungsten Inert Gas (TIG) welding were conducted in oxygen-saturated liquid Pb-Bi eutectic alloy at 550 °C for 500 h, 1000 h and 1500 h to study the effect of different flow velocities (1.70 m/s, 2.31 m/s and 2.98 m/s) and corrosion time on corrosion behavior. The results indicate that the double-layer oxide films consist of Fe3O4 outer layer and (Fe,Cr)3O4 inner layer on the surface of all samples. With the increase of relative flow velocity, the dissolution and migration of elements are faster, which leads the degree of corrosion to become more severe. In the corrosion process of CLAM steel weld bead in flowing liquid Pb-Bi, the oxidation-corrosion and erosion have happened. Meanwhile, the degree of erosion on the surface of weld bead samples was more serious than that of the base metal samples. The experiment has obtained the function between corrosion time and oxide layer thickness of CLAM base metal and weld bead in Pb-Bi with 2.98 m/s.

Effect of Weld Cooling Rates on Mechanical and Metallurgical Properties of Submerged Arc Welded Pressure Vessel Steel

Submerged arc welding of SA 516 grade 60 pressure vessel grade steel was conducted with different heat plate thicknesses and the influence of cooling rate on microstructure, Vickers hardness, and impact toughness of heat affected zone (HAZ) of weldment was systematically investigated. Weld cooling rates vary with change in heat input or variation in plate thickness of base metal. Results showed that thin plates accumulate the heat, which cause grain coarsening and loss of acicular ferrite (AF) microstructure, which is further responsible for lower impact strength of welded joint. It is deemed that faster cooling rates due to heat sink in thickness direction with thick plates cause high percentage of AF with finer grain and enhanced hardness values. Improved impact strength with thick plates with same heat input signifies that supplying heat more than required to thin plates may cause microstructural deterioration and responsible for impact strength loss of weldments. Test demonstrates that the cooling rate should be above 15 °C/s to keep impact strength loss within considerable limits.

PROCEDURE FOR DETERMINING PROCESS CHARACTERISTICS OF FRICTION STIR WELDING

Purpose . The study is aimed at improving the procedure for determining the optimum radius of the shoulder of a special tool for friction stir welding (FSW) of aluminum alloys and its change depending on the variations of base metal thickness. Methodology. The friction stir welding process was carried out on specially designed equipment. The material for the studies were 1.85 mm thick plates made of aluminum alloy AMg3 with a chemical content of alloying elements within the range of the brand composition. The temperature in the welding zone and the pressure from the tool on the edges of the welded joint were determined using a specially designed research stand. The pressing force of the tool to the base metal during welding was measured with a dynamometer type DC-0.1 with the indicator head. Findings . During the research, the degree of metal heating and the quality of the welded joint formation were determined at various ratios of the rotation frequency of the working tool and the normal pressure to the joining edges. The research allowed determining the influence of FSW process parameters on the temperature of metal heating in the action zone of the working tool shoulder. Originality . The experimental studies allowed to determine the effect of the working tool rotation speed and the magnitude of its pressure on the welded metal during welding on the temperature in the weld zone. Increasing the tool rotation frequency allows to reduce pressure of the working tool during welding, which results in more efficient and high-quality welding process. It has been established that it is possible to obtain better welded joints at a temperature of about 0.7 Tm and to determine the optimal temperature range in the welding zone. Practical value . The study resulted in determination of the conditions for achieving the permanent softening effect during friction stir welding and the optimum temperatures in the welding zone for the tested alloy. The main technological parameters of the working tool are calculated and their influence on the generation of thermal energy in the welding zone is determined. The thermal analysis of the welding process resulted in development of the procedure for determining the technological parameters of the working tool and its rotation frequency depending on the weld metal thickness.

Fire resistance of a prefabricated bushfire bunker using aerated concrete panels

Prefabricated lightweight aerated concrete (PLAC) panels provide low thermal conductivity, potentially high stiffness-to-weight ratios, cost-effective material and structural systems and rapid modular construction. These panels can be utilised as floor slabs or external walls for various applications in building construction. The fire performance of the PLAC panel is examined in this work for a particular case, namely a prefabricated emergency bushfire shelter, which is one of the key applications of PLAC panels. Since, bushfires have unique heating curves, standardised tests are not useful and the system needs to be tested in a manner such that the heat flux of an actual bush fire can be reproduced. In this study, the fire performance enhancement of dual-skin bushfire bunkers, which are comprised of lightweight concrete and base metal thickness (BMT) steel, are examined experimentally and validated numerically. The Speedpanel PLAC modular panel explored in this work is a lightweight wall system primarily used for acoustic and thermal insulation purposes. Burning experimental studies of a single panel and dual-skin bunkers are carried out on a full scale. The experimental results are compared with fire safety codes for building materials to identify the key areas for improvements. A fire dynamic numerical model has been developed in this work using the Fire Dynamics Simulator (FDS) to simulate the burning process of PLAC structures. Numerical results of heat production are presented in comparison with experimental observations for validating the computational model. The proposed numerical model is used to predict the fire performance of a dual-skin bushfire bunker, demonstrating the need to have at least two PLAC layers to ensure fire safety compliance.