High Strength Steel

Controlling the amount of distortion and tensile residual stresses plays an important role during welding of high strength steels. The amount of distortion and residual stresses in high strength steel welds may be reduced and compressive residual stresses can be induced by lowering the transformation temperature with the use of low-transformation-temperature (LTT) welding electrodes. In this study, high strength Domex 500 plates (500 mm × 300 mm × 7 mm) were welded with conventional high strength electrodes and LTT filler electrodes with a diameter of 2.5 mm. The objective of the study is to compare the mechanical and microstructural properties of high strength steel joints (i.e., Domex 500) produced using both conventional electrodes and newly-developed prototype LTT electrodes.

Resistance spot welding (RSW) is considered as predominant welding technique that is used in the manufacturing of modern automobile structure. The automobile structure is made of high strength steel which is preferred by the car industry companies due to its high strength-weight ratio. This work presents an optimization method for RSW of high-strength low-alloy steel DOCOL 500 LA. Tensile test and microstructure analysis for base material (BM) were carried out to get the mechanical properties of BM and to specify the rolling direction. Taguchi method, high efficiency technique, was applied using Minitab19 software to achieve the optimization process. Tensile shear test was carried out to evaluate the strength of welding nugget, absorbed energy and failure mode. The results showed that the optimum parameters were 8,800 A for the current, 30 cycles for the welding time and 2,230 N for the electrode force and two types of failure modes could be observed which were interfacial and full pullout mode.

High strength low alloy steel (HSLA DOCOL 500 LA) is utilized in the automotive structure because of its superior qualities such as good fatigue resistance, a high strength-to-weight ratio, assisting in reducing the weight of the vehicle, increasing fuel efficiency and lower CO2 emissions. Resistance Spot Welding (RSW) is the most welding technique that is used to join automobile parts together. This study investigated the RSW process for high-strength steel. By utilizing the Taguchi approach, the optimization process for double spot nuggets with the principal welding parameters of welding current, welding time, and electrode force was carried out. The values of optimum parameters were 8800Amp for welding current, welding time of 30 cycles and 2560 N for electrode force. Mechanical and microstructure tests were carried out to study the failure modes while the fatigue test was achieved to obtain the fatigue endurance limit and it was at a maximum load 1500 N and during the fatigue test two types of failure happened: full pull-out failure and cracks around the nugget zone.

In a steel structure, choosing the connections type are one of the most important parameters in design consideration. How a connection type affects the vibration of steel beams has been investigated in this paper. The most effective connection type in reducing beam vibration has been highlighted. The study was conducted using different finite element models to simulate each connection type. Firstly, the model was validated by comparing its results with the results obtained by the analytical approach. In the numerical model, a linear frequency analysis was performed to determine beam natural frequency, then it has been compared with the corresponding value obtained by the Euler-Bernoulli approximations for simply supported beams. After that, two analysis procedures have been executed, steady-state analysis and transient analysis. In the steady-state analysis, a harmonic load with different frequencies was applied to the beam mid-span, while an impulsive load has been applied in the transient analysis. The results indicate that the deflection could be reduced by 72%, furthermore steady vibration of the beam can be reduced by 81% with using one of the moment connections instead of the traditional shear connection.

Seismic codes use the behaviour factor to consider the ductility and the structure's non-linearity to improve the system's overall performance. Generally, Steel moment-resisting frames are characterized by a relatively high period showing high deformability and, foreseen that with stringent damageability criteria, the adopted behaviour factor might not optimally be utilized for achieving better performance of the frames. The design is generally governed by stiffness, leaving behind a complex structural system where the capacity design rules are disturbed and therefore necessitates to relax the drift limits for such frames. Given this and with extensive parametric analysis, the current paper aims to examine the behaviour factor of steel Moment Resisting Frames (MRFs). The parametric analysis has been conducted on rigid steel MRFs of 9, 7, and 5 storeys with bay 4 different bay widths of 9.15 m, 7.63 m, 6.54 m, and 5.08 m. Perimeter frame configuration has been designed using 4 different behaviour factors (q = 6.5, 4, 3, and 2) for a total number of 144 cases. Static nonlinear analysis has been conducted, and consequently, the behaviour factors have been examined. It has been observed that compatibility is required while choosing the drift limit for an assumed ductility class of the code.

Elastic bonding is a relatively new fastening technique that complements traditional fastening methods. It joins two materials with a layer of permanently elastic adhesive and offers high peel strength, impact resistance, and flexibility. The most convenient way to describe the mechanical properties of adhesive bonds is in terms of the generalized elasticity factor or stiffness. To calculate the spring constant for an adhesive-bonded joint, multiply the stiffness value a dimensionless quantity by the known joint dimensions.

Hydrogen embrittlement leads to mechanical degradation of metals. Hence, hydrogen sorption/desorption properties of metals need to be characterized. An electrochemical procedure based on cyclic voltammetry (CV) and potentiostatic polarization is elaborated on plain-carbon steel. The procedure consists of first two consecutive CV cycles (pretreatment and reference CV), followed by cathodic H-charging, and subsequent CV scans to study and quantify the H-sorption/desorption. Best practice in this procedure is to perform all steps consecutively without interruption or sample manipulations between steps to avoid spontaneous H-loss. The H-related interaction with the steel is clearly identified in the CV and can be differentiated from the electrolyte contribution coming from thiourea. The study confirms the role of thiourea as H-recombination poison in alkaline solution, and also demonstrates that it contributes to the CV response. Additionally, various charging times are investigated to study the time to H-saturation, and also the scan rate during the CV procedure is varied to study time-related phenomena. Dedicated discharging experiments were included in the study to complement the CV data, giving additional insights in the H-steel interaction. Moreover, hydrogen related findings are successfully verified by using a complimentary method, i.e. hot extraction. The better understanding of the peaks in the CV and the continuous procedure result in a reliable methodology to characterize the H-sorption/desorption in steel.

In the two last decades, the automotive industry has an increasing demand to lower car weight, while increasing the strength and stiffness level of the applied steel used in the car body. This industrial requirement is met by the development of new classes of high strength steels. However, these high strength steels are susceptible to hydrogen embrittlement, because their manufacturing processes can induce zones of high deformation (strain) and hydrogen absorption. Typically, the absorbed hydrogen is not homogeneously distributed in the deformed steel matrix; on the contrary, its distribution is influenced by the local strain as well as by microstructural features. Hence, the impact of manufacturing processes on local hydrogen uptake in steel needs to be investigated.

Hydrogen embrittlement leads to mechanical degradation of metals. Hence, hydrogen sorption/desorption properties of metals need to be characterized. An electrochemical procedure based on cyclic voltammetry (CV) and potentiostatic polarization is elaborated on plain-carbon steel. The procedure consists of first two consecutive CV cycles (pretreatment and reference CV), followed by cathodic H-charging, and subsequent CV scans to study and quantify the H-sorption/desorption. Best practice in this procedure is to perform all steps consecutively without interruption or sample manipulations between steps to avoid spontaneous H-loss. The H-related interaction with the steel is clearly identified in the CV and can be differentiated from the electrolyte contribution coming from thiourea. The study confirms the role of thiourea as H-recombination poison in alkaline solution, and also demonstrates that it contributes to the CV response. Additionally, various charging times are investigated to study the time to H-saturation, and also the scan rate during the CV procedure is varied to study time-related phenomena. Dedicated discharging experiments were included in the study to complement the CV data, giving additional insights in the H-steel interaction. Moreover, hydrogen related findings are successfully verified by using a complimentary method, i.e. hot extraction. The better understanding of the peaks in the CV and the continuous procedure result in a reliable methodology to characterize the H-sorption/desorption in steel.

Steel manufacturing processes can induce high deformation (strain) in the microstructure of high strength steels, making them more susceptible to hydrogen embrittlement. It is crucial to investigate the impact of the manufacturing process on the local hydrogen uptake in steel. The microcapillary cell electrochemical method is capable of evaluating the hydrogen uptake in steel as a function of the deformation which is induced by various mechanical methods, i.e cold rolling, bending and punching. A clear relation between the deformation degree and the local hydrogen content is established for a dual phase (DP600) steel. Going towards microscale investigations of punched samples, the analysis of the deformed zones nearby the punched edge by a combination of optical microscopy, scanning electron microscopy and micro hardness measurement provide additional information on the microstructural characteristics of these highly deformed zones. Furthermore, the magnitude of the deformation nearby the punched edge is quantitatively determined by means of electron backscatter diffraction technique. A shear affected zone is identified at the edge of the punched hole, where excessive deformation and a higher dislocation density are present. The dedicated local electrochemical measurements confirm the presence of a high amount of local hydrogen in this shear affected zone, which is likely detrimental for hydrogen embrittlement.

Nowadays, the steel industry is able to produce structural members made of high strength steel grades up to S690/S700. However, the use of such members in constructions is still rather limited mainly because it is relatively difficulty for a designer to easily identify the projects where there is an economical interest of using high strength steel for such members. In the framework of a RFCS European project entitled "ATTEL -Performance-based approaches for high strength tubular columns and connections under earthquake and fire loadings", a study has been performed at the University of Liège to identify the structural typologies, with account of their specific loading conditions, where the use of tubular column made of high strength steel is economically interesting.

A total of 148 web crippling tests were conducted using high-strength, low-ductility Structural Grade 80 ofASTM A653 steel (former ASTM A446 Grade E steel) and tests results were evaluated along with additional 114 web crippling tests which were reported in 1986 as part of a project on Design of Automotive Structural Components Using High-Strength Sheet Steels. Four loading conditions, namely End-One-Flange (EOF), Interior-One-Flange (IOF), End-Two-Flange (ETF), and Interior-Two-Flange (ITF) conditions, were considered in the web crippling tests. Test results indicate that the tested ultimate loads for the four loading conditions were higher than the predicted loads using the AISI Specifications for the yield strength of the steels exceeding 80 ksi (551.6 MPa). The ratio of the tested ultimate load to the calculated load tends to increase with increase in the yield strength of the steels beyond SO ksi. New modified kC, and kC, factors were developed based on the 262 web crippling tests which included the following parameters: the yield strength F y ranged from 58.2 ksi (401.3 MPa)to 165.1 ksi (1138.4 MPa), hit ratio from 25.99 to 208.19, Rltratio from 1.496 to 5.696, NIt ratio from 22.70 to 88.24, Nih ratio from 0.17 to 2.02, thickness of steel sheets from 0.017" to 0.088" (0.43 to 2.24 mm), and the angle between plane of web and plane of bearing surface from 59.5 to 90 degr»..e. Reasonable agreement was found between the tested ultimate loads and the predicted loads using the new modified kC, and kC, factors.

Hot dip galvanizing is a very popular and well known process in corrosion protection of steel. However, very occasionally, cracks appear on structures when they leave the zinc bath. The responsible crack phenomenon appears to be liquid metal embrittlement. This phenomenon is already known for a long time, but it is still not yet fully understood. The lack of fundamental theoretical knowledge and the absence of accurate models to predict liquid metal embrittlement oblige engineers to set up extensive test programs to determine an area of process parameters in which safe design is guaranteed. A qualitative understanding of the various influencing parameters during galvanizing is necessary to explain the occurrence of liquid metal embrittlement. This knowledge is also helpful to design an experimental test set up and procedure for evaluating the influence of one parameter where the effect of other parameters should remain constant. This master thesis deals with the occurrence of liquid metal embrittlement when galvanizing welded high strength steels. This paper gives an overview of the most important process parameters and gives a short description of possible future experimental work.

Fatigue behaviour is most commonly evaluated in uni-axial cyclic stress tests using standardised dog-bone samples. When components are sharply bent into shape and subjected to cyclic loading, the fatigue damage will accumulate at the inside of the bend. This paper reports on an experimental investigation about the feasibility of infrared thermographic techniques to monitor fatigue damage initiation and accumulation. By monitoring spectral components of the thermal response, the fatigue limit, the onset of crack initiation and the ratio of initiation to propagation lifetime can all be determined. Also the effect of surface treatments on initiation properties is investigated. Most results are consistent with expected behaviour based on a previous study, indicating that thermographic techniques have a greater sensitivity and can be used to reduce the number of samples and time required for fatigue characterisation.

A large number of reinforced concrete (RC) frame structures built in earthquake-prone areas such as Haiti are vulnerable to strong ground motions. Structures in developing countries need low-cost seismic retrofit solutions to reduce their vulnerability. This paper investigates the feasibility of using masonry infill walls to reduce deformations and damage caused by strong ground motions in brittle and weak RC frames designed only for gravity loads. A numerical experiment was conducted in which several idealized prototypes representing RC frame structures of school buildings damaged during the Port-au-Prince earthquake (Haiti, 2010) were strengthened by adding elements representing masonry infill walls arranged in different configurations. Each configuration was characterized by the ratio R m of the area of walls in the direction of the ground motion (in plan) installed in each story to the total floor area. The numerical representations of these idealized RC frame structures with different values of R m were (hypothetically) subjected to three major earthquakes with peak ground accelerations of approximately 0.5g. The results of the non-linear dynamic response analyses were summarized in tentative relationships between R m and four parameters commonly used to characterize the seismic response of structures: interstory drift, Park and Ang indexes of damage, and total amount of energy dissipated by the main frame. It was found that R m =4% is a reasonable minimum design value for seismic retrofitting purposes in cases in which available resources are not sufficient to afford conventional retrofit measures.

The welding property of TiB 2 /ZL101 composite was investigated using electron beam (EB) welding experimental system with a function generator. The fine defect-free welding seam was obtained under proper processing parameters and scanning rate. The reinforcement particles TiB 2 distributed homogeneously in welding seam without any segregation. The tensile results show that fracture occurs at the base metal and elastic modulus increases compared with base metal. Wear resistance of welding seam is improved greatly compared with base metal. The results show that the TiB 2 /ZL101 composite can be successfully welded by EB technology.

Martensite formed in TRIP steels causes large work hardening. The expectation that this is due to the back stresses induced into the ferrite by the hard martensite was examined by the Bauschinger effect after room temperature tensile straining of a TRIP steel into which the martensite had been introduced by prior straining at -50°C. Bending tests were employed to detect the Bauschinger effect. The tests showed that the compressive flow stress became much smaller than the tensile flow stress and confirmed the expectation.

The findings of a literature review of topics related to the anchorage of headed reinforcement are presented. The topics are grouped in three broad categories: conventional anchorage of reinforcement, anchorage of headed reinforcement, and a review of strut-and-tie modeling. The review of conventional anchorage focuses on the mechanics of bond and code provisions for development length. A review of hooked bar anchorage is also included. The review of headed reinforcement includes historical background, a survey of commercially available products, a summary of the published research on headed reinforcement and related topics such as deeply embedded anchor bolts and the bearing capacity of rigid plates, and a review of pertinent code provisions. The review of strut-and-tie modeling (STM) includes an historical background, an overview of the STM design process, a review of code provisions, and a summary of selected research. 17. Key Words concrete reinforcement, headed reinforcement, s...

Abstract. An increasing market need for high strength low alloy (HSLA) strip steels for oil and gas API (American Petroleum Institute) pipelines of superior grades has placed an even increasing pressure upon the steel works for high quality steel strip. In order to achieve this goal as ...

This paper describes the computations of micro-strains at inner corner of cold formed rectangular hollow sections (CFRHS) made up of structural steels using finite element analysis. In order to obtain the micro-strains, distortion test is simulated by modeling two-dimensional structural steel tubes in ANSYS software. Two dimensional linear static analyses are performed by defining elastic properties of steel. These simulations were performed for tubes with outer radius to thickness (r o /t) ratios of 3. In real distortion tests, the direction of force at outer corner of the tube may vary in terms of angle. Therefore, this fact is taken into account while performing simulations. One more aspect is taken into consideration which is related to strain gauge placement during distortion testing. This problem is analyzed by modeling three-dimensional structural tubes and performing linear static analyses to investigate the variations in strains at inner bent section of the tube with different strain gauge locations.

With five Arvedi ESP lines, Rizhao Steel in China is now focusing on the highly attractive local and export markets for high-quality, thin-gauge strip products. The first lines began operations in 2015. High-strength but lightweight car bodies, ultra-thin structures paired with the highest tensile strength -and all at the lowest production costs. Innovative processes are required in order to fulfil the demands of the car and metals industries. With precise thermo-mechanical rolling and rigorous temperature guidance in the narrowest possible operations windows Arvedi ESP opens the door to producing demanding steel grades in the shortest implementation times and at reduced alloying costs. Low operation costs are also provided by efficient induction heating and the resulting energy savings. This paper presents the ESP plant setup of Rizhao Steel as well as the training and support program. Additionally the potentials of AHSS production with ESP will be described by referencing the results of the first ESP plant in operation since 2009 at Arvedi Steel, Italy, and the ESP plants of Rizhao steel.

A fracture criterion for sheet metals subjected to draw-bending is investigated using the concept of the forming limit stress criterion. An experimental apparatus that is capable of draw-bending sheet specimens with forming speeds (approximately 100 -1 mm s  ) comparable to those of real press forming machines is designed and built. The test materials are an ultralow-carbon steel sheet and a 590MPa high-strength steel sheet. Specimens undergo bending-unbending under tension when passing over a die profile. The magnitudes of true stress DB  at which the stretch-drawn specimens fractured are precisely determined from the measured data of the drawing force and the crosssectional area of the specimen after fracture. Moreover, multiaxial tube expansion tests are performed to measure the forming limit stresses PT  of the test materials under plane-strain tension. It is found that DB  is larger than PT  by 6-18%. Therefore, it is concluded that the forming limit stress criterion is effective for the fracture prediction in draw-bending.

Microstructural refinement to further improve the strength and stability of high-strength high-conductivity Cu-Cr-Nb alloys was attained by mechanical milling (MM). Mechanically milled Cu-4Cr-2Nb and Cu-8Cr-2Nb exhibited an increase in hot-pressed Vickers hardness of 122 and 96 pct, respectively. Mechanical milling produced a corresponding decrease in electrical conductivity of ϳ33 pct for both alloys. The increase in hardness was more due to Cu grain-size refinement than to second-phase particle-size refinement. The drop in conductivity was due to second-phase particle-size refinement, which both increased particle/matrix interfacial area and solute solubility. Mechanically processed Cu-4Cr-2Nb displayed an enhanced thermal stability. Hot-pressed 4-hour milled Cu-4Cr-2Nb experienced a 30 pct increase in conductivity with only a 22 pct drop in hardness when annealed at 1273 K for 50 hours. Such changes were largely due to an increase in dispersed-particle size (i.e., a decrease in solute and interfacial electron scattering) and Cu grain size (reduced Hall-Petch effect), respectively. The optimum hardness and conductivity combination was found in 4-hour milled and hot-pressed Cu-4Cr-2Nb material. stability, thermal conductivity of the material is an important factor. For higher conductivity, a smaller amount of stable and TERNARY Cu-Cr-Nb alloys, particularly with a compostrong Cr 2 Nb particles is favorable, thus making an alloy with sition of 8 at. pct Cr and 4 at. pct Nb, have demonstrated high 4 at. pct Nb and 2 at. pct Cr (Cu-4Nb-2Cr) a better choice. strength and high conductivity coupled with good thermal However, the lower Cr 2 Nb content has an inevitable adverse stability. 2] This behavior is due to the insoluble and strong effect on strengthening. To maximize the strengthening of this Cr 2 Nb intermetallic phase (with a 2:1 Cr/Nb ratio) in a copper alloy, i.e., to take advantage of the substantial Hall-Petch matrix. The Cr 2 Nb phase is distributed as large primary precipieffect derived from the pinning capability of Cr 2 Nb particles, tates, formed congruently from the melt, and fine secondary mechanical milling (MM) was selected as a convenient proc-Cr 2 Nb particles, precipitated from solid solution. Previous essing approach. In addition to general size refinement, it studies of extruded Cu-8Cr-4Nb exposed to temperatures of was also expected that MM can bring primary and secondary up to 1323 K for up to 100 h indicated a drop in strength of particle sizes closer together to further enhance thermal stabilonly 25 to 30 pct. Such behavior was mainly a manifestation ity. Thus, the impetus of the present study is to apply MM in of Cu grains stabilized by Cr 2 Nb dispersoids characterized by order to refine the initial microstructure to a level that ultia sluggish coarsening behavior. 5, It was found that the mately improves the strength of Cu-4Cr-2Nb relative to asprimary particles, usually situated at grain boundaries and extruded Cu-8Cr-4Nb. The objective of this work is to study triple points, provide a direct grain boundary pinning effect the effects of MM on the microstructure in order to understand and, hence, an indirect grain boundary strengthening (Hallalloy strength behavior and strengthening mechanisms, stabil-Petch) effect. The secondary Cr 2 Nb particles provide Orowan ity, and thermal conductivity of Cu-4Nb-2Cr alloys. strengthening. For extruded material, it was established that grain boundary strengthening accounts for about two-thirds of the overall strength of material, with Orowan effects essentially II. EXPERIMENTAL contributing the remainder. This thermal stability, along with A. Starting Material strengthening effects and, more importantly, strength retention, was the driving force to improve these alloys. They are strong Argon-atomized Cu-4Cr-2Nb prealloyed powders (Ͻ106 candidates for uses ranging from welding electrode and highm) were supplied by Special Metals, Inc. to NASA Lewis voltage switch applications to more advanced active-cooling Research Center. Melting procedures were based on the methapplications such as first wall, divertor interactive components ods developed at NASA Lewis (Cleveland, Ohio) for similar and magnetic confinement in fusion reactors, combustion Cu-Cr-Nb alloys. 2] The chemical composition of the powchamber liners for next-generation reusable launch vehicle ders was 3.27 wt pct (4.0 at. pct) Cr and 2.92 wt pct (2.0 at. engines, and rocket nozzle liners. pct) Nb-for Cu-4Cr-2Nb. The oxygen level was at 450 ppm. For all of these applications, in addition to strength and B.

This study aims at evaluating the influence of fatigue strain range on hydrogen embrittlement of resulfurized high strength steel on low-cycle fatigue tests. Previously, samples were charged with hydrogen (H) under different conditions. The presence of H causes softening effects on the cyclic behavior and a reduction in fatigue life of samples in comparison with uncharged samples. The explanation of this behavior is based on quantitative analyses of fracture surfaces as well as the microstructure by optical microscopy and scanning electron microscopy (SEM). Moreover, enthalpy changes, associated with the main H trapping sites, were determined by differential scanning calorimetry (DSC).This study has enhanced the understanding of the variables that most influence the fatigue behavior of this type of steel charged with hydrogen.

This paper analyzes the influence of fatigue loading on the residual stress profile in high strength steel wires. To this end, different sinusoidal loads with diverse values of maximum loading level and number of cycles were simulated on wires in which several residual stress profiles had been previously introduced, some of them with a tensile state and others with a compressive state. An analysis was made of the evolution with time of such residual stress laws by comparing them at key instants of loading, that is, at initial instant, at maximum load, at minimum load and at final instant. Numerical results show only a minor influence of fatigue loading on the residual stress profile.

This paper presents the commercial production of a high strength low alloy steel with 8 different thicknesses through continuous casting route. All the plates exhibit tempered martensite structure after heat treatment. Mechanical properties of different thickness plates are obtained from tensile testing. Charpy impact properties of the steel plates are evaluated at room temperature and at -40°C. From the tensile and impact tests, it is noticed that the continuous cast steel displays a good combination of strength and impact toughness. Ballistic performance of the steel is carried out by impacting against 7.62-mm-high hardness armour piercing (AP) steel projectiles and 125 mm FSAPDS ammunition. A comparison of microstructure, mechanical and ballistic propertiesof the continuous cast steel and conventional ingot cast steel has been carried out. It is observed that the continuous cast steel displays marginal improvement in ballistic performance in comparison to the ingot cast steel.The ballistic behaviour of the continuous cast steel is also compared with that of the rolled homogeneous armour steel.

This research reports a numerical study on the flexural strength of single-lipped Zed-Purlin sections under two equal moments applied at the ends of the specimen. The effects of attaching corrugated steel sheeting to the tension flange of Z-purlins on the structural behavior are investigated. The studied parameters of the specimens are: types of corrugated steel sheeting, depth-to-thickness ratio, and the span of the purlins. Linear and non-linear analyses using finite element software are conducted. Results show that a tension flange braced by corrugated steel sheeting can increase the section capacity of Z-purlins and change the failure mode. The results of the ultimate moment obtained from finite element analysis have been compared to both the nominal flexural strength according to the Egyptian code (ECP) and the North American Specifications (AISI). The results of purlins with sheeting determined by ECP are conservative due to ignoring the effect of corrugated steel sheeting on capacity, while the results from AISI are in good agreement with finite element analysis as they take into account the effect of sheeting.

Abstrak-Tujuan dari tulisan ini adalah mengulas baja tahan balistik dari prespektif ilmu metalurgi modern yang juga terdapat dalam kitab suci Al-Quran. Baja adalah salah satu material logam yang banyak diaplikasikan sebagai material tahan balistik. Karateristik balistik adalah kemampuan menahan tumbukan dari proyektil yang melaju pada kecepatan sangat tinggi. Plat baja telah banyak dikembangkan sebagai material tahan balistik dan menjadi pilihan utama sebagai bahan kontruksi kendaraan tempur (armored fighting vehicle :AFV). Dengan pemaduan dan perlakuan panas pada baja dapat meningkatkan kekerasan, kekuatan, ketahanan impak dan ketahanan balistik. Pemaduan dengan unsur nikel (Ni), kromium (Cr), molibdium (Mo), danMangan (Mn) pada saat peleburan dapat meningkatkan kekerasan. Proses perlakuan panas dengan celup dapat memaksimalkan kekerasan dan proses temper dapat meningkatkan ketangguhan. Penambahan unsur "tembaga (Cu)" dengan cara memanaskan baja dibuat dinding yang tak seorang pun mampu mendaki dan melubanginya seperti yang terdapat dalam Al-Quran Surat Al-Kahfayat 95-97.

Hydrogen embrittlement is believed to be one of the main reasons for cracking of steel structures under stress and stress corrosion cracking process. To control and prevent the cracking of steel it is necessary to understand the chemical and physical properties of hydrogen inside iron. Usually, pre-stressed steels are high strength steels that include a ferritic core made of α-iron (bodycentered-cubic lattice, bcc). Previous works have focused on the effect of internal and external stresses/strains on the interstitial H and bcc-Fe interaction. Using ab-initio Molecular Dynamics and by taking statistical averages diffusion coefficients for hydrogen diffusion paths have been obtained. Depending on temperature, the diffusion path visits preferentially tetrahedral or octahedral sites. Simulations where a number of hydrogens occasionally meet in one unit cell have been performed to elucidate the effect of interactions between hydrogens, and diffusion coefficients have been calculated from Einstein´s equation. Under these conditions, the Fe-Fe interaction has been found to be weaker than in the absence of hydrogen. Debye temperature for Iron decreases monotonically with and increasing concentration of interstitial hydrogen, showing that iron-iron interatomic potential is weaker in the presence of a large number of diffusing hydrogen atoms. In this work, we have focused on the structural consequences for the iron lattice upon absorption of interstitial H in octahedral sites. Using ab-initio Density Functional Theory we have computed the kinetic barriers for a phase transition bcc > fcc > hcp along a Bain's pathway. All the barriers are lowered by the presence of hydrogen; the initial part (bcc>fcc) being almost barrierless. This kind of phase transformation carries out atomic rearrangements and changes in the unit cell volume that should affect the mechanical properties of iron, as revealed by calculations for the elastic constants of the material.

Hydrogen embrittlement is believed to be one of the main reasons for cracking of structures under stress. High strength steels in these structures often include a ferritic core made of alpha-iron (body centered cubic lattice). We compute the interaction of atomic hydrogen with iron using first principles. The interstitial hydrogen can be placed in two high symmetry positions: octahedral and tetrahedral sites. Our calculations provide diffusion barriers between these sites. These barriers have been analyzed to understand the propagation of hydrogen through the iron lattice. We analyze how these barriers can be modified by the hydrogen concentration.

In this study, numerical models were developed to predict the behavior of steel extended end-plate moment connections subjected to static and blast-like loading. Two types of extended end-plate connections were considered, stiffened, and unstiffened, with pretensioned bolts. The models were verified by comparing the results with published experimental data. The models were used to compute the moment-rotation curves for the connection under static loading, and then under different blast durations. The pressure impulse diagram and the energy dissipation for the connection under dynamic loading were determined. The failure modes were examined, and the numerical results were compared with the simplified models presented in codes and standards. Improvement in the performance of the connection by adding one or two stiffeners was demonstrated. For the configuration studied, introducing a stiffener increased plastic dissipation energy for blast loading by 45% compared to the unstiffened connection, whereas under static loading, the plastic energy dissipation for stiffened connection, SC2, was higher than the unstiffened connection by 30%. A conservative estimate for the dynamic increase factor (DIF) was found to be 1.2 for steel yield stress and 1.05 for bolt failure.

In low speed collisions, insurance cost is a factor which is taken into account as a design criterion to reduce structure damage and fixing cost. In this study, it is focused on the applied permanent damages of vehicle frontal door caused by pole impacts. In the side impact, the side door beam is responsible to absorb the most possible kinetic energy. Two significant parameters including material and geometry of a side door beam are discussed here to reduce permanent damage of the door. To study the effect of material as the first phase, six different sheets of material have been concerned to investigate the rigidity of the structure. For the second phase, geometry modification of the side door beam has been performed via creating new CAD-reinforcing ribs. Consequently, the strength in elasto-plastic mode, maximum deflection and plastic strain of the equipped system representing the permanent damage is obtained in order to achieve lower losses.

This paper presents the commercial production of a high strength low alloy steel with 8 different thicknesses through continuous casting route. All the plates exhibit tempered martensite structure after heat treatment. Mechanical properties of different thickness plates are obtained from tensile testing. Charpy impact properties of the steel plates are evaluated at room temperature and at-40°C. From the tensile and impact tests, it is noticed that the continuous cast steel displays a good combination of strength and impact toughness. Ballistic performance of the steel is carried out by impacting against 7.62-mm-high hardness armour piercing (AP) steel projectiles and 125 mm FSAPDS ammunition. A comparison of microstructure, mechanical and ballistic propertiesof the continuous cast steel and conventional ingot cast steel has been carried out. It is observed that the continuous cast steel displays marginal improvement in ballistic performance in comparison to the ingot cast steel.The ballistic behaviour of the continuous cast steel is also compared with that of the rolled homogeneous armour steel.

This thesis is a study into the response and seismic safety of three-dimensional multi-storey concrete structures under concurrent orthogonal seismic excitations. It employs the nonlinear time-history method as its analysis tools. Time-history analyses rely heavily on their utilised earthquake records. Accordingly, this study examines the different approaches of selecting earthquake suites and develops a methodology of selecting representative earthquake scenarios. This methodology is credibly implemented in selecting a far- and a near field suites representative of the New Zealand seismic hazard. The study investigates the response of 6-, 9- and 12-storey concrete structures of different n-X-bays × m-Y-bays. Bidirectional responses of these considered structures are examined and consequently the current combination rules are scrutinised. Consequently this study strongly recommends the use of the 40-percent combination rule in lieu of the widely used 30-percent rule; and the use of ...

Anisotropic behaviors of high strength steel grade SPFH590 and HPFC780 used extensively in automotive industry are explored. V-bending tests were carried out on various bending direction. It was found that the investigated material showed little differences in the resistance to deformation and resistance to thinning from all directions. Thereafter, negligible effect of the bending direction on the degree of springback was detected. Large bend radius caused high level of springback. However, the increasing rate of springback is decreased with larger radius.

Charpy impact testing of a high strength low-alloyed (HSLA) steel has been performed by simultaneously recording two independent signals. The magnetic emission (ME) and potential drop (PD) techniques were used to determine critical crack initiation properties on standard V-notched and pre-cracked three-point bending specimens at room temperature. Both signals (ME and PD) were recorded and compared, with the purpose of more precise identification of critical fracture mechanics parameters determining the onset of ductile crack growth. Standard Charpy specimens made of HSLA steel, oriented perpendicular to rolling direction were tested by a modified instrumentation of the Charpy machine, which included the original magnetic emission, and the potential drop techniques. The strain gauges and emission probes, located on the hammer tup, measured the force, thus both the magnetic and electric potential drop signals were monitored and recorded as a function of time. The obtained results indi...

This study investigates the seismic performance of two groups of existing reinforced concrete (RC) buildings: those designed and constructed according to older standards (pre-code RC buildings) and those designed and constructed in accordance with current seismic code requirements (moderate-code RC buildings). Recognizing the potential seismic vulnerability of these structures, this research aims to develop fragility curves to probabilistically assess their seismic performance. Nonlinear time history analysis (NTHA) and incremental dynamic analysis (IDA) are employed, considering inter-story drift ratios (%ISDR) as key engineering demand parameters. These parameters are employed to link structural response to ground motion intensities (PGA) across various hazard levels, including Service Level Earthquake (SLE), Design Basic Earthquake (DBE), and Maximum Considered Earthquake (MCE). Eleven sets of ground motions, selected from the PEER database and matched to the Yangon target response spectrum, are used to simulate seismic loading. A representative 12-story RC frame with two plan aspect ratios is analyzed, considering material and geometric non-linearities. Five performance limit states (Fully operational, Immediate Occupancy, Damage Control, Life Safety, and Collapse Prevention) are defined based on FEMA 356. The developed fragility curves provide valuable insights into the seismic vulnerability of existing RC structures, informing the development of effective seismic risk-mitigating strategies and enhancing the resilience of urban areas.

Concrete-filled steel tubes (CFSTs) and reinforced concrete-filled steel tubes (RCFSTs) are increasingly used in transportation structures as piers, piles, caissons or other foundation components. While the axial and flexural properties of CFTs have been well researched, research on their shear resistance is lacking. Currently accepted methods for calculating the shear capacity of CFSTs and RCFTs are adapted from shear strength equations used for structural steel or reinforced concrete components. Though, it is expected that CFSTs would retain the full shear capacity of the steel without local buckling of the section. In addition, because circular CFSTs provide optimum confinement to the concrete core, it is also expected that the full shear strength of plain or longitudinally reinforced concrete can also be developed. Since no equation currently accounts for both, it is probable that they significantly underestimate the effectiveness of the composite section, potentially increasing undesirable conservatism and cost. However, without experimental data to validate the design expressions, it is not possible to modify them. The research program described herein experimentally investigated the shear resistance and deformation of CFST and RCFST members with an eye towards developing an improved and more accurate shear strength expression. The experimental study included 22 large-scale CFTs subjected to four-point bending. The study parameters included: (1) the aspect ratio (a/D where a is the clear span from the point of loading to the point of support and D is the tube diameter), (2) concrete strength, (3) D/t (where t is the thickness of the steel tube), (4) interface condition (greased or contaminated with soil), (5) infill type (concrete or gravel), (6) internal reinforcement ratio, and (6) length of the tube beyond the support (tail length). The results indicate that the shear strength of CFSTs and RCFSTs is on average 2 times the current WSDOT expression. This new design expression for shear resistance has been proposed for implementation in the WSDOT Bridge Design Manual (BDM).

Findings from a study on the effect of hook bend angle, concrete clear cover, and orientation of confining reinforcement on hook anchorage strength are presented. The range of test parameters was much broader than in previous studies. Bar stress at anchorage failure ranged from 33,000 to 137,400 psi (228 to 947 MPa) and concrete compressive strengths ranged from 4300 to 16,500 psi (30 to 114 MPa). Anchorage strength of hooked bars was insensitive to bend angle (90 or 180 degrees) and side cover (between 2.5 and 3.5 in. [65 and 90 mm]). Confining reinforcement was found to increase anchorage strength for 180-degree hooked bars regardless of orientation (parallel or perpendicular to the embedment length). For 90-degree hooked bars, reinforcement oriented parallel to the embedment length had a greater effect on anchorage strength than reinforcement oriented perpendicular to the embedment length.

Key factors affecting the anchorage strength of hooked bars are investigated and design guidelines for the development length of hooked bars that apply to both conventional and highstrength steel and concrete are presented. In this study, 337 beam-column joint specimens were tested. Parameters included number of hooks (2, 3, or 4), concrete compressive strength (4,300 to 16,510 psi [30 to 114 MPa]), bar stress at failure (22,800 to 141,600 psi [157 to 976 MPa]), bar diameter (No. 5, 8, and 11 [No. 19, 25, and 36]), concrete side cover (1.5 to 4 in. [38 to 102 mm]), quantity of confining reinforcement in the joint region, hooked bar spacing (3 to 11 bar diameters measured center-to-center), hook bend angle (90° or 180°), placement of the hook (inside or outside the column core, and inside or outside of the column compressive region), and embedment length. Using a subset of 214 simulated exterior beam-column joints, expressions are developed to characterize the anchorage capacity of hooked bars as a function of embedment length, concrete compressive strength, bar diameter, and amount and orientation of confining reinforcement. The results of this study show that front failure plays an important role in the behavior of hooked bars, which contrasts with the findings of previous studies. The provisions in the 2014 ACI Building Code become less conservative as the concrete compressive strength and bar diameter increase. The contribution of concrete compressive strength to the anchorage capacity of hooked bars can be represented by the concrete compressive strength to the 0.29 power, in contrast to the 0.5 power currently used in the ACI 318-14 Code. Confining reinforcement, expressed as the area of confining reinforcement per confined hooked bar, provides in an incremental rather than percentage increase in the anchorage capacity of hooked bars. Confining reinforcement parallel to the straight portion of the hooked bars contributes to the anchorage capacity of both 90° and 180° iii hooked bars. The contribution of confining reinforcement oriented perpendicular to the straight portion of the hooked bar differs from that of confining reinforcement parallel to the straight portion of the hooked bar and may be similar to the contribution of confining reinforcement to the development and splice strength of straight bars. Hooked bars with 90° and 180° bend angles produce similar anchorage capacities and can be used interchangeably. Increasing concrete side cover from 2.5 to 3.5 in. (64 to 89 mm) does not increase the anchorage capacity of hooked bars. These observations are incorporated into a new design equation that allows for the conservative design of hooked bars at concrete strengths up to 16,000 psi and steel stresses up to 120 ksi, well above current Code limits.

was prepared as a doctoral dissertation by Erick Antonio Burgos Ganuza under the direction of Professor Andrés Lepage (Chair). Primary financial support for the experimental program was provided by Commercial Metals Company and MMFX Technologies Corporation. Additional support was provided by the Ministry of Education of the Government of El Salvador through a FANTEL "Talento Salvadoreño" scholarship and by the Universidad Centroamericana "José Simeón Cañas". Appreciation is due to a number of dedicated students and technicians who were involved in the construction of specimens and test programs. Upon completion of his Ph.D. in January of 2019, Dr. Burgos joined the San Francisco office of Rutherford+Chekene as a Senior Design Engineer. Later, he returned to El Salvador in August of 2020 and joined the Department of Structural Mechanics of the Universidad Centroamericana "José Simeón Cañas" as an Associate Professor.

This paper presents the results of an experimental study on the anchorage strength of conventional and high-strength steel hooked bars. Three hundred and thirty-seven exterior beam-column joint specimens were tested with compressive strengths ranging from 4300 to 16,500 psi (30 to 114 MPa). Parameters investigated included the number of hooked bars per specimen, bar diameter, side cover, amount of confining reinforcement, hooked bar spacing, hook bend angle, hook placement, and embedment length. Bar stresses at failure ranged from 22,800 to 144,100 psi (157 and 994 MPa). The majority of the hooked bars failed by a combination of front and side failure, with front failure being the dominant failure mode. Test results show that development lengths of hooked bars calculated based on ACI 318-14 are very conservative for No. 5 (No. 16) bars and become progressively less conservative with increasing bar size and concrete compressive strength.

To improve the mechanical properties of high strength steels the application of innovative methods is often necessary. One of such technology used in the field of heat treatment (HT) is the quenching and partitioning process. By this method higher content of stabile retained austenite (RA) can be achieved, which increase material ductility while its strength remains only slightly reduced. The experiment compares the mechanical properties of the 42SiCr steel heat treated conventionally or by the QP process. Parameters were designed for both HT modes to achieve approximately the same tensile strength and then the elongations and RA contents were compared. As part of the experiment the metallographic analysis, the X-ray diffraction analysis, hardness measurement and tensile test were performed. The results showed improvement of mechanical properties of the samples treated by QP process. The conventionally treated material (with RA content of 8 %) showed the elongation of 10% at the tensile strength of 1980 MPa while the specimen processed by QP reached elongation of 14% at a tensile strength of 2000 MPa and RA content was also higher (11%). On the basis of this knowledge the future research will be focused on the optimization of QP process parameters.

In this paper, the detailed procedure for defining the optimal technology for welding the structures made of the high strength steel S690QL is presented. That steel belongs into a group of steels with exceptional mechanical properties. The most prominent properties are the high tensile strength and impact toughness, at room and at elevated temperatures, as well. However, this steel has a negative characteristic -proneness to appearance of cold cracks. That impedes welding and makes as an imperative to study different aspects of this steel's properties as well as those of eventual filler metal. Selection and defining of the optimal welding technology of this high strength steel is done for the purpose of preserving the favorable mechanical properties once the welded joint is realized; properties of the welded metal and the melting zone, as well as in the heat affected zone, which is the most critical zone of the welded joint.

Under the concept of "Industry 4.0", production processes will be pushed to be increasingly interconnected, information based on a real time basis and, necessarily, much more efficient. In this context, capacity optimization goes beyond the traditional aim of capacity maximization, contributing also for organization's profitability and value. Indeed, lean management and continuous improvement approaches suggest capacity optimization instead of maximization. The study of capacity optimization and costing models is an important research topic that deserves contributions from both the practical and theoretical perspectives. This paper presents and discusses a mathematical model for capacity management based on different costing models (ABC and TDABC). A generic model has been developed and it was used to analyze idle capacity and to design strategies towards the maximization of organization's value. The trade-off capacity maximization vs operational efficiency is highlighted and it is shown that capacity optimization might hide operational inefficiency.

The determination of quality parameters of resistance spot weld in real time is of great importance in today's industry. Acoustic waves can solve this problem in the sense of measuring certain features directly related to the weld quality -degree of heating of the weld zone, moment of beginning of melting and some others. The ultrasonic transducer incorporated into an electrode sends short acoustic pulses into the weld area and receives the signals reflected from different interfaces in heat affected zone during welding process. The specific image and signal processing algorithms applied to the received signals enable us to localize weak reflections from internal interfaces, recognize their nature and use this information to characterize the weld quality. Introduction: The inspection of resistance spot weld quality in real time is quite a challenging and at the same time promising field of NDT. It enables one to monitor the dynamics of the spot weld properties right at the moment of the weld manufacturing. It is extremely important on the industrial floor as it gives the operator information about the quality of the product and thus enables him to correct the mistake before it is too late. Quality inspection of "hot" welds is relatively new field of NDT studies which is potentially capable of providing 100% quality output of the production line. It becomes especially important as long as implementation of the in-line quality inspection techniques will help save a lot of time by elimination or, at least, reduction of costs of after-production inspection and fixing bad parts. Our approach to the above mentioned problem is using the acoustic waves which pass through the spot weld structure during welding. On their way through the setup the waves are modified by the media and thus carry some information about the processes taking place inside the system. The setup consists of a set of one or two ultrasonic transducers incorporated into the electrodes of the spot welder. The ultrasonic transducers are driven by pulser-receiver; the last is controlled by the computer. The schematic view of the setup is presented in Figure .

Real-time spot weld characterization using ultrasound is a reality in today's automotive industry. The main goal of such testing systems is to reduce operational time and provide reliable means of quality inspection. Currently, several R&D groups are working to develop real-time ultrasonic system for spot weld quality monitoring, because potentially it allows one to eliminate expensive destructive tests, reduce the amount of off-line ultrasonic inspections and ensure the inspection quality. The purpose of this paper is to analyze preliminary results of a single in-line ultrasonic station, installed at a real body-in-white plant condition, and perform a comparison of these results with the conventional quality assurance methods currently used at the plant, such as ultrasonic inspections (manual equipment strategically placed in the welding line), destructive (tensile tests) and metallographic tests. The results obtained from this comparison can show us if it is possible to apply this new technique in a real production environment, with the same reliability that we are used to experience in our current inspection structure. It is believed that the obtained results will provide more flexibility for the plants to work with available ultrasonic inspection equipment, will increase the reliability and the control in the most critical regions of the bodies and will also decrease the inspection time during production.