Mild Steel Sheet Research Articles

Effect of operating parameters on plate bending by laser line heating

Laser line heating is a plate bending technique. It is produced due to the heating effect of a laser beam when irradiated over a suitable heating path. In this work, the effect on angular deformation under different operating parameters, such as energy (in terms of laser power), scanning speed and number of passes along with the thickness of the substrate material, was studied under straight line scanning schemes. In this experiment, CO2 laser has been used and the substrate material used is the mild steel sheet. The effect of each operating parameter was taken into account to find the optimum process parameter. The design of experiment has been applied with the help of Taguchi method, and the results were obtained and analysed with the help of analysis of variance and Taguchi analysis (signal-to-noise ratio), for the determination of the optimized values of the operating parameters with their effect towards angular deformation in the process. A regression analysis also has also been performed to obtain a suitable co-relationship between bending angle and other operating parameters.

Joining Aluminium Alloy and Mild Steel Sheets by Roller Clinching

Roller clinching is a mechanical joining method, which combines conventional clinching with rotational tool movement. For that purpose, punches and dies are mounted on contrariwise rotating rolls, while the sheets are continuously fed forward. The rotation affects the joint formation and therefore the mechanical joint properties. In this paper, the ratio between the rolling radii of punch and die is varied. Shear tests are conducted for the material combination steel and aluminium with different sheet thicknesses. Because of the asymmetry of the resulting clinchpoints, the joint strengths are examined in different load directions. The joint formation is analysed using cross sections and the effects of different punch geometries are discussed. Finite element simulations are used to gain deeper process insight.

Fracture Prediction for Ultralow Carbon Steel Sheet Subjected to Draw-Bending Using Forming Limit Stress Criterion

A fracture criterion for sheet metals subjected to draw-bending is investigated using the concept of forming limit stress criterion. The test material used is a 1.0-mm-thick ultralow carbon steel sheet. Draw-bending experiment of a wide specimen is performed for a die profile radius of 4mm. A specimen undergoes bending-unbending under tension when passing over the die profile radius. The drawing speed was set to 5mm/s. The magnitude of true stress when a specimen fractured has been precisely determined from the measured data of a drawing force and the cross sectional area of the draw-bent specimen after fracture. Moreover, multiaxial tube expansion tests of the test material are performed to measure the forming limit stress of the test material under plane strain tension. It is found that the is larger than by approximately 10 %. Therefore, it is concluded that the forming limit stress criterion is effective as a fracture criterion for a mild steel sheet subjected to draw-bending.

An investigation on co-axial water-jet assisted fiber laser cutting of metal sheets

Water assisted laser cutting has received significant attention in recent times with assurance of many advantages than conventional gas assisted laser cutting. A comparative study between co-axial water-jet and gas-jet assisted laser cutting of thin sheets of mild steel (MS) and titanium (Ti) by fiber laser is presented. Fiber laser (1.07µm wavelength) was utilised because of its low absorption in water. The cut quality was evaluated in terms of average kerf, projected dross height, heat affected zone (HAZ) and cut surface roughness. It was observed that a broad range process parameter could produce consistent cut quality in MS. However, oxygen assisted cutting could produce better quality only with optimised parameters at high laser power and high cutting speed. In Ti cutting the water-jet assisted laser cutting performed better over the entire range of process parameters compared with gas assisted cutting. The specific energy, defined as the amount of laser energy required to remove unit volume of material was found more in case of water-jet assisted laser cutting process. It is mainly due to various losses associated with water assisted laser processing such as absorption of laser energy in water and scattering at the interaction zone.

Measurement and Analysis of the Differential Hardening of Ultralow Carbon Steel Sheets

Multiaxial tube expansion tests were performed to precisely measure the work hardening behavior of mild steel sheets with different r-values for a range of strain from initial yield to fracture. The testing machine is capable of applying an arbitrary linear stress path to a tubular specimen using an electrical, closed-loop servo-control system for the axial force and internal pressure applied to the tubular specimen. Tubular specimens with an inner diameter of 44.6 mm were fabricated from the as-received sheet sample by roller bending and laser welding. Nine linear stress paths, σx(rolling direction) :σy (transverse direction) =1:0, 4:1, 2:1, 4:3, 1:1, 3:4, 1:2, 1:4, and 0:1, in the first quadrant of the principal stress space were applied to the tubular specimens to measure the contours of plastic work and the directions of the plastic strain rates. It was found that the shapes of the measured work contours changed with increasing plastic work, or equivalently with increasing the reference plastic strain ; the test materials exhibited differential hardening (DH). The general trend of the DH appeared to be affected by the average r-value, or equivalently by the texture, of the materials.

Revisiting the wrinkling limits in flexible roll forming

This article presents a new understanding on the deformation mechanics of flexible roll forming and is focused on the occurrence of flange wrinkling. The presentation draws from the experimental and numerical simulation of flexible roll forming to the determination of the wrinkling limits by means of a new theoretical and experimental methodology based on the utilization of rectangular test specimens loaded in axial compression. This research work is performed in mild steel sheets and the results show that the combined evolution of the effective strain with stress triaxiality obtained from finite element modelling of flexible roll forming and from the rectangular test specimens loaded in axial compression can be successfully utilized to predict the occurrence of flange wrinkling in variable cross-sectional profiles produced by flexible roll forming. The proposed methodology can, therefore, be considered an alternative to existing approaches based on simplified analytical and numerical procedures.

Linseed oil-filled microcapsules containing drier and corrosion inhibitor – Their effects on self-healing capability of paints

Abstract Core–shell microcapsules of urea-resorcinol-formaldehyde shell and linseed oil (LO) core material as paint additives for self-healing coatings were prepared. The capsules contained LO either with or without Co-octoate as drier material and/or octadecylamine (ODA) as corrosion inhibitor. The microcapsules embedded in a commercial paint were applied on sandblasted mild steel sheets. After scratching the coated surface, the inhibition efficiency of core–shell microcapsule-containing coat, dipped into corrosive media, was followed visually and evaluated numerically by electrochemical impedance spectroscopy (EIS). In separate experiments, to optimize for the self-healing process, the composition of the core material, the effect of the drier and/or the inhibitor ODA on drying process of LO films were monitored by infrared spectroscopy. Pure LO needed 6–7 days to dry completely. The drying period could be shortened (to 5 h) via application of a dryer, but the addition of the corrosion inhibitor alone increased significantly the time needed for solifidication. To minimize the drying period we have found the proper combination of the ODA and the dryer of the LO. The EIS measurements, in accordance with the drying tests, resulted in the next order of self-healing ability: LO (+ODA) (+Co-octoate) (+ODA+Co-octoate) .

Study of Earing Defect during Deep Drawing Process with Finite Element Simulation

Deep drawing is one of widely used sheet metal working process in industries to produce cup shaped components at a very high rate. In deep drawing process, a sheet metal blank form cylindrical components by process in which central portion of sheet is pressed into die opening to draw the metal into desired shape without folding the corners. Earing is one of the major defects observed during deep drawing process due to anisotropic nature of sheet metal. Earing is defined as formation of waviness on uppermost portion of deep drawn cup. Knowledge about ear formation in deep drawing process allows a prior modification of process which can result in defect free final product with financial saving and time. The initial blank shape used in present study is circular in nature.The objective of present study aims to produce parts which are earing defect free. Earing can be reduced by modifying the initial blank shape such as use of non circular blank as in present study. Efforts have been made to study the earing problem in deep drawing of cylindrical cups by finite element modeling software HYPERWORK-12 and Incremental RADIOSS as solver. The blank material selected for study is EN10130FeP06 mild steel sheet of 1mm thickness as it has wide application in fabricating automobile parts. Mechanical parameters of mild steel are incorporated in finite element simulation of deep drawing process. Significant earing was observed at rolling and transverse direction on deformed cup form circular blank. Modification of initial blank is done to reduce the earing defect. The results show significant reduction of % earing height and drawing load as well as improvement in maximum thickness variations.

Failure mode and fatigue behavior of weld-bonded lap-shear specimens of magnesium and steel sheets

Failure modes and fatigue behaviors of ultrasonic spot welds in lap-shear specimens of magnesium AZ31B-H24 and hot-dipped-galvanized mild steel sheets with and without adhesive were investigated. The spot welded specimens failed from the kinked crack growth mode. The adhesive-bonded specimens failed from the cohesive failure through the adhesive and the kinked crack growth through the magnesium sheet. The weld-bonded specimens failed from the cohesive failure through the adhesive, the interfacial failure through the spot weld, and the kinked crack growth through the magnesium sheet. The estimated fatigue lives for the adhesive-bonded and weld-bonded specimens failed from the kinked crack growth mode are lower than the experimental results.

An Enclosed variable focusing lens for remote welding

In this study, a variable focusing lens with a driving mechanism was developed. The surface curvature of the lens is formed via the interaction of elastic film tension and liquid pressure generated by compression of a bellows, which enables the focal length to be changed. This paper discusses the optical characteristics of the lens system. The focal length range is 250 - 750 mm with beam diameters of 0.3 mm - 0.9 mm, respectively, when a YAG laser is irradiated. In the study, the lens system was applied to laser beam welding of mild-steel sheet with a thickness of 0.5 mm for 3,000 shots of laser irradiation at a peak power of 4.7 kW and a duration of 10 ms.

Fatigue behaviour of clinched joints in a steel sheet

AbstractClinch joining has been used in sheet metal work owing to its simplicity and because it facilitates the joining dissimilar metal sheets. In this study, monotonic and fatigue tests were conducted using coach‐peel and cross‐tension type specimens to evaluate the fatigue strength of clinch joints in a cold‐rolled mild steel sheet. The monotonic experimental results reveal that the coach‐peel specimen exhibits the lowest monotonic strength among the three specimen configurations. The coach‐peel and cross‐tension specimen geometries exhibit very low fatigue ratios, compared with the tensile‐shear specimen. The maximum von Mises and principal stresses at the fatigue endurance limit are much higher than the engineering tensile strengths of the steel sheet used to determine the three specimen geometries. Compared with the effective stress and maximum principal stress, the Smith–Watson–Topper fatigue parameter can be used for an appropriate prediction of the current experimental fatigue life. With regard to the coach‐peel specimen geometry, all samples exhibit pull‐out failure mode in the fatigue testing range. However, for the cross‐tension specimen geometry, mixed (pull‐out and interface) and interface failure modes occurred, depending on the number of cycles to failure.

Effect of tool eccentricity on the joint strength in mechanical clinching process

The effect of tool eccentricity on the joint strength in clinching process was investigated. The objective is to understand the mechanical behaviour of the clinched joint where proper control on the alignment setting of tools can be considered. In this research, a clinching process to form a round joint was carried out by offsetting the centre line between the upper punch and lower die. The experimental results were compared between offset and without offset conditions. Coated mild steel sheets were used for the evaluation. It is found that the strength values by offset clinching exhibit variation in sinusoidal relationship with respect to the in-plane offset direction.

Retraction Note to: Corrosion protection of steel sheets by chitosan from shrimp shells at acid pH

The corrosion behavior of mild steel (MS) sheets in 0.5 M H2SO4 in the presence of chitosan extracted from shrimp shells (CSS) has been studied using electrochemical techniques. The optimum concentration (10 µM) of this carbohydrate polymer inhibited MS corrosion up to 85 % in the solution of the acid electrolyte. Results reveal that CSS reduced the dissolution of MS linearly with its concentration, and this reduction could be attributed to the interfacial formation of CSS film at the MS-electrolyte boundary. CSS is a mixed-type inhibitor and the shapes of Nyquist capacitive and inductive loops obtained from the impedance results could be associated with double layer reactions and relaxation of corrosive ions adsorption in the presence of CSS, respectively, at the MS/solution interface. Surface analytical studies with atomic force microscope, scanning electron microscope and Fourier transform infra-red also confirm the adsorption of CSS on MS.

DEFLECTION CONTROL IN RCC BEAMS BY USING MILD STEEL STRIPS (AN EXPERIMENTAL INVESTIGATION)

It is well recognised that in modern practice, structural failures are all too common in terms of Serviceability and are relatively rare in terms of Safety. Adoption of limit state of design and higher grades of concrete and steel in modern RCC structures has led to overall thinner member sections and high stress levels at service loads. These in turn have resulted in larger deflections, crackwidths, vibrations etc. In particular, it is the Serviceability Limit state of ‘Durability’ that calls for particular attention, because ‘Deflection’ is a very important criteria need to be taken into account. Due to architectural constrain generally depth of beams are restricted, that leads to more deflection in a beam . An attempt has been made through this project to check the feasibility and efficiency of Mild Steel sheets used as a composite material with traditional RCC beams to modify its serviceability criteria. MS Sheets are used due to their economy, durability and are also easily available in large variety of cross-sections (gauges). MS sheets also have the property of being cast to any shape without much need of significant formwork. The composite construction has an edge over the conventional reinforced concrete material because of its ease of construction, thinner sections as compared to RCC, efficient bonding with concrete due to its large surface area & high tensile strength (per unit weight) which makes it a favourable material for prefabrication also. The ill effect of corrosion is reduced here as the MS Strips are embedded into the concrete material, thus less prone to exposure and also has no aesthetic issues. Extra care can be taken by providing coating also. The main aim of this project is to increase the stiffness of beam in order to control the deflection. Mild steel sheets and strips of varying thickness (gauges) were embedded into traditional RCC beam vertically along side faces in longitudinal direction. This increases both moment of inertia as well as modulus of elasticity of beam, thus increasing its stiffness and controlling deflection. The test results are compared and it has been observed that deflection is controlled by about 30% and strength is increased by about 25% in MS-strip composite beams as compared to control beam.

Stress intensity factor solutions for adhesive-bonded lap-shear specimens of magnesium and steel sheets with and without kinked cracks for fatigue life estimations

In this paper, stress intensity factor solutions for adhesive-bonded lap-shear specimens of magnesium alloy AZ31 and hot-dip-galvanized (HDG) mild steel sheets with and without kinked cracks are investigated for fatigue life estimations. First, the kinked fatigue crack failure mode of the adhesive-bonded lap-shear specimens is briefly reviewed. Then, the analytical global J integral and effective stress intensity factor solutions for main cracks in lap-shear specimens of three dissimilar sheets under plane strain conditions are developed based on the beam bending theory. The global effective stress intensity factor solutions for the main cracks in the lap-shear specimens from the corresponding finite element analyses are then presented and validated by the analytical solutions. Next, the local stress intensity factor solutions for kinked cracks with the experimentally observed kink angle as functions of the kink length from the corresponding finite element analyses are presented and the computational solutions are also compared with the analytical solutions at small kink lengths. The results indicate that the computational local stress intensity factor solutions for kinked cracks approach to the analytical solutions as the kink length decreases to a small value and the kinked crack is under dominant mode I loading conditions. The computational results also indicate that the local stress intensity factor solutions at a small kink length of microstructural significance may be used as the stress intensity factor solutions for zero or near zero kink length for fatigue life estimations when the computational results are not available. The computational local stress intensity factor solutions are then adopted to estimate the fatigue lives of the lap-shear specimens based on a kinked crack growth model and available material constants for the Paris law. The fatigue life estimations are lower than the experimental results. However, the general trend of fatigue life estimations agrees with that of the experimental results.

Effect of material flow on joint strength in activation spot joining of Al alloy and steel sheets

A new joining method for dissimilar metal sheets was developed where a rotated consumable rod of Al alloy is pressed onto an Al alloy sheet at the part overlapped with a mild steel sheet. The metal flow in the joining region is increased by the through-hole in the Al sheet and consumable Al rod. The rod creates the joint interface and pads out of the thinly joined parts through pressing. This produces a higher joint strength than that of conventional friction stir spot welding. Measurements of the joint interface showed the presence of a 5-10 nm thick amorphous layer consisting of Al and Mg oxides.

Ballistic behavior of steel sheet subjected to impact and perforation

The paper is reporting some comparisons between experimental and numerical results in terms of failure mode, failure time and ballistic properties of mild steel sheet. Several projectile shapes have been considered to take into account the stress triaxiality effect on the failure mode during impact, penetration and perforation. The initial and residual velocities as well as the failure time have been measured during the tests to estimate more physical quantities. It has to be noticed that the failure time was defined using a High Speed Camera (HSC). Thanks to it, the impact forces (average and maximum level), were analyzed using numerical simulations together with an analytical description coupled to experimental observations. The key point of the model is the consideration of a shape function to define the pulse loading during perforation.

THEORETICAL FLEXURAL BEHAVIOR OF SANDWICH PANEL USING COMPOSITE MATERIALS

Sandwich panels made of thin polymer composite materials have been developed and characterized as an alternative material to the mild steel sheet sheets conventionally used as face sheet materials [outer cover] for refrigerator, washing machine, and in automotive appliances like automobile, boat etc. In this paper sandwich panel made of Glass Chopped Strand Mat (GCSM) face sheets with polyester foam Coremat XM, polyester foam Coremat Xi and jute are fabricated. Flexural behavior of sandwich panel is studied. Theoretical results of sandwich panel is compared with 0.8 mm M.S. specimen conventionally used for manufacturing the body of automobile, cover of many machines and appliances. The load versus deflection relation of sandwich panel is almost linear. The strength and deflection are calculated theoretically by the equations derived from theory of bending. From the results It is found that sandwich composite have quite superior properties, which can be used for various engineering applications.

Influence of the plastic anisotropy modelling in the reverse deep drawing process simulation

This study deals with the description of the anisotropic behaviour of the mild steel sheet used in the reverse deep drawing process of a cylindrical cup, which was proposed as benchmark at the Numisheet’99 conference. The effect of the yield criterion on the numerical results is analysed using three yield functions, von Mises, Hill’48 and Barlat Yld’91, combined with the Swift hardening law. The anisotropy parameters of the Hill’48 model are identified using either the yield stresses or r-values, obtained from the uniaxial tensile test at three different directions. On the other hand, the anisotropy parameters of the Yld’91 are determined taking into account both the yield stresses and r-values, minimizing an objective function. The comparison between experimental and numerical results is presented, being the punch force evolution and the thickness distribution along the cup wall the principal variables under study. In both forming stages, the predicted punch force evolution is close to the experimental one, whatever the yield criterion adopted. Nevertheless, the cup wall thickness distribution is strongly influenced by the yield criteria, being clearly overestimated by the von Mises yield criterion. On the other hand, the Yld’91 yield criterion provides a thickness distribution closer to the experimental one, for both forming stages. The strain paths during both forming stages ranges from uniaxial compression, when the material flows between the die and blank-holder, to plane strain in the cup wall, whereas the important strain path changes occurs in the die radius.

Experimental and numerical investigation on laser beam forming of steel sheets

Laser beam forming process being a non-contact process requires no hard tooling systems and presses. Hence, it is considered suitable for low-volume and high-variety production of sheet metal parts for different industrial applications. This paper reports on the experimental and finite element-based numerical investigation of the laser beam forming process. The experimental setup for the investigation includes an Nd: YAG laser with a maximum power of 4.4 kW and adjustable beam diameter. The L-27 Taguchi Orthogonal Array Design of Experiment was employed in this study in order to identify the variables that mostly influence the outcome of the experiment. The optimised process parameter window employed for the laser beam forming process was further classified into the minimum, medium and maximum parameter window settings. The finite element analysis was performed using the commercial package ANSYS to validate the experimental results. This investigation was able to validate the response related to deformation and identify the effect of the laser power on the bending angle for the mild steel sheets used in this study. The finite element models were parametrically developed using the ANSYS Parametric Design Language, the scripting language provided in ANSYS version 14.0. The maximum variation in the bending angle between the experiment and the finite element simulation was 9%, recorded at the maximum parameter setting during the laser beam forming process. The results showed that there was a strong correlation between the numerical and the experimental results.