Maximum Value Of Residual Stress Research Articles

Semi-destructive methods for evaluating the micro-scale residual stresses of carbon fiber reinforced polymers

Micro-scale residual stress in carbon fiber reinforced polymers have a significant impact on their mechanical performance. The residual stresses in the carbon fibers were released by micro-slotting and micro-ring-core methods using focused ion beam (FIB). The released deformation fields were captured by cross-gratings and mapped by geometric phase analysis (GPA) and digital image correlation (DIC) methods. The in-plane residual stresses in the carbon fibers were experimentally determined to be −40.5 MPa using elastic constitutive relations, which is consistent with the composites cylinder model. The axial compressive residual stresses in the fibers were found to be greater than −100 MPa. Moreover, the maximum value of residual stress in the polymer matrix was observed at the interface, potentially serving as a crack initiation site.

Finite element based 3-D modelling of residual stress in high vacuum actively brazed diamond/Ni-Cr filler/C45 steel joint

In active brazing of diamonds, high brazing temperature and difference in the thermo-mechanical properties of the diamond grain, filler alloy, and substrate lead to the development of unfavorable residual stresses in the bonding region. This residual stress can potentially cause initiation of cracks within the interfacial reaction layer formed between diamond and filler-alloy, weakening the joint. Since the diamond particles used in diamond grinding tools are micro-sized and complex in shape, it is experimentally difficult to measure residual stress at the grit-filler interface. In the present investigation, a coupled thermo-mechanical three-dimensional finite element model has been developed to predict, map, and analyse the formation of residual stresses in diamond-bond-substrate systems. The presented model uniquely differs from those in literature, which are mostly 2-D type and did not consider the presence of interfacial reaction layer between diamond and filler. A Ni-Cr-Fe-B active brazing alloy has been selected as the filler and C45 steel as the substrate in the current simulation. Chromium carbide has been considered to be the interfacial compound. The numerical simulation suggests that the maximum value of residual stresses, predominantly tensile in nature, gets shifted from the diamond to the intermetallic zone at the bond level when the interfacial reaction compound is introduced between the diamond and filler. It also establishes that orientations of diamond during its placement on substrate for brazing have significant influence on the magnitude of induced residual stress. Approximately 40 % reduction has been observed in case of hexagon-base brazed diamonds when compared to that (1620 MPa) developed on square-base brazed diamonds. Raman spectral analysis of brazed specimen was conducted to experimentally validate the numerical simulation results. Residual stress was estimated from the peak shift of D-band in the spectra. The numerically computed residual stresses were found to deviate within the range of 3–15 % of the experimentally determined values.

Numerical simulation of thermal distribution and residual stress characteristic for laser wobble joining of CFRTP and Ti-6Al-4V alloy

The joining of light alloy and carbon fiber reinforced thermoplastics composite (CFRTP) is recently considered to be an effective way to meet the lightweight requirements of components manufacturing in the aviation field. Furthermore, laser joining technology presents an innovative method for joining CFRTP and light alloy with the advantage of high precision, high efficiency and non-contact. In this paper, a thermo-mechanically coupled model for laser wobble joining of CFRTP and Ti-6Al-4V alloy has been established with the combined heat source, which has not been comprehensively studied in the published research. The typical features of the temperature field and the distribution characteristic of the residual stress are analyzed thoroughly under various parameters, whereas the optimized process parameters are attained in terms of the size of the resin melting zone (RMZ) at the interface as well as the maximum value of residual stress. In addition, a validation experiment was implemented to substantiate the established model. The results indicate that the size of RMZ at the interface enlarges appreciably with higher laser power and lower scanning speed. The distinct residual stress concentration around the weld and the asymmetric residual stress concentration inside the CFRTP can be principally interpreted with the comprehensive effect of non-uniform heat input and fixture constraints during the laser joining process. Moreover, according to the size of RMZ as well as the maximum value of residual stress, the optimum parameters are eventually determined as scanning speed of 0.015 m/s and laser power of 2000 W. The simulated result presents substantial consistency with the verification experimental result, therefore corroborating the validity and accuracy of the established model.

Welding-induced Residual Stresses in U-Ribs of a Steel Bridge Deck

To calculate the welding-induced residual stresses in U-ribs of the steel deck plate and conduct quantitative analysis of influential factors, the U-ribs of steel deck plate of Xinghai Bay Bridge was taken as the research object. In the ABAQUS finite element software, the local models of U-ribs of steel deck plate were established. Nodal body force loads, i.e., heat generation rate, of the double ellipsoidal heat source models were applied via the compiled subsidiary Dflux program. The welding process of the v-groove welds was simulated, to obtain the residual stresses distribution in the top plate and U-rib plates. The influence of thickness of top plate and angle of welding groove on the residual stresses in the U-ribs were studied. The results show that the welding-induced residual stresses calculated by the numerical method proposed in this paper agree well with the experimental data. The maximum residual stresses in the top plates and the U-rib plates all occur near the welds, which exceeds the yielding limitation of the material. As the thickness of top plate increases, the maximum values of residual stresses in the top plates and U-ribs increase. However, with the increase of groove angle, the maximum values of residual stresses in the top plates and U-rib plates decrease.

Experimental and Numerical Investigation of Residual Stress in Coatings on Steel

Abstract In the present work, an alumina–titania (13 %) coating has been deposited by the air plasma spray process on a mild steel substrate by preheating the substrate to different temperatures. Coating thickness was measured by a scanning electron microscope, the hardness of coatings was measured, and morphology was also checked. The crack compliance technique has been used to determine the residual stress, as it is a very simple method, and also, it is compatible with conventional machining equipment and wire electric discharge machining equipment. Specimens were cut by the diamond cutter up to certain depth in microns, and the strain relieved was recorded. For finding out the residual stress, these recorded values of strain have been used by doing a finite element analysis (FEA) using the ANSYS 15.0 (Ansys, Inc., Canonsburg, PA) software. For validation of the model, uniaxial tension was applied on a sample by using the INSTRON universal testing machine (Instron Inc., Norwood, MA), and strain values at both the coating side and the substrate side were recorded and matched with the model under the same value of the load. After verifying the model, an equation has been developed using the Minitab software (Minitab Inc, Bengaluru, India), and the strains previously recorded were used as an input to the equation obtained, and the value of residual stress was calculated. The maximum value of residual stress was found at the coating–substrate interface, and the values of residual stress for sample preheated at 250°C, 200°C, and 150°C were found to be compressive, with the magnitude of −176.28 MPa, −243.54 MPa, and −255.42 MPa, respectively.

Определение остаточного напряженного состояния патрубков высокого давления при алмазном выглаживании

The paper presents the results of a study that examines modelling of the polishing and hardening treatment of axisymmetric cylindrical parts such as high-pressure fittings with metal seals on the pipe and the rod. A finite element model of the diamond smoothing process was developed, which allowed one to determine the stress state in the deformation zone depending on the feed rate, tool deflection angle, pressing force, and depth of penetration into the material of the part. The analysis of the modelling results helped to identify a range of optimal modes for diamond smoothing. By using finite element modelling in ANSYS Workbench Mechanical it was possible to test those smoothing modes that were difficult to test experimentally. The study identified the most significant factors that influenced the formation of the maximum values of residual stresses in the surface layer of gate assemblies of high-pressure valves. The maximum values of compressive residual stresses, the value of which did not exceed the yield strength of the material were determined.

Estimation of wire strength based on residual stresses induced during wire electric discharge machining

Frequent breakages of wire electrode during wire electric discharge machining (WEDM) adversely affect the productivity and surface quality of the finished products. Uncontrolled thermal loads and large thermal stresses generated during the discharge phenomenon reduce the strength of the wire which eventually leads to wire rupture. Thermal residual stresses retained in the wire can cause the formation of microcracks, voids and pits which increases the probability of wire rupture. Thus, it is essential to predict and prevent the wire breakage phenomenon for better machining productivity. This paper presents an approach to estimate the wire safety index based on thermal residual stresses that generate on the wire electrode by using a finite element method based model. A three-dimensional nonlinear transient thermo-mechanical model for a molybdenum wire used during WEDM has been developed to compute the temperature and the induced stresses. The influence of the wire velocity has been incorporated. The computational ability of the developed model has been verified by conducting systematic experiments. The experimental values of the residual stresses were obtained by using X-ray diffraction (XRD) technique. The stresses produced on the wire were observed to reach values beyond the yield stress (600 MPa) of the molybdenum wire at certain process conditions, which causes the reduction in strength of the wire. The wire safety index was evaluated by calculating a ratio (X) between the maximum value of residual stress induced and the yield stress of the wire. Formation of microcracks on the wire surface was considered as an indicator of wire breakage to estimate the threshold value of wire strength beyond which the wire is considered to be unsafe for machining.

Residual Stresses and Surface Roughness Analysis of Truncated Cones of Steel Sheet Made by Single Point Incremental Forming

The dimensional accuracy and mechanical properties of metal components formed by the Single Point Incremental Forming (SPIF) process are greatly affected by the prevailing state of residual stress. An X-ray diffraction method has been applied to achieve an understanding of the residual stress formation caused by the SPIF process of deep drawing a quality steel sheet drawpiece. The test object for an analysis of residual stress distribution was a conical truncated drawpiece with a slope angle of 71° and base diameter of the cone of 65 mm. The forming process has been carried out on a 3-axis HAAS TM1P milling machine. Uniaxial tensile tests have been carried out in the universal tensile testing machine to characterize the material tested. It was found that the inner surface of the drawpiece revealed small linear grooves as a result of the interaction of the tool tip with the workpiece. By contrast, the outer surface was free of grooves which are a source of premature cracking. The stress profile exhibits a nonlinear distribution due to different strengthening of the material along the generating line of the truncated conical drawpiece. The SPIF parts experienced a maximum residual stress value of about 84.5 MPa.

Effects of media parameters on enhance ability of hardness and residual stress of Ti6Al4V by fine shot peening

Most orthopedic devices are made from Ti6Al4V, but there is significant research showing that bending force can cause the failure of implants. Fine shot peening is a surface modification that can increase bending strength from the increasing of hardness and residual compressive stress, however, many kinds and sizes of media are used in this process. Therefore, this research focused on investigating the effect of media size of silica and SUS304 as these media are biocompatible. The bigger size of SUS304 media could generate -721 MPa of residual compressive stress and 440 HV of hardness that was higher than smaller media, which was -630 MPa and 420 HV. The effect of bigger media was also deeper than the smaller media because of the high impact energy, resulting in a change of grain shape and orientation. On the other hand, the higher hardness media namely silica was able to generate higher maximum value of residual stress and hardness than those of SUS304, which was -729 MPa and 470 HV respectively, and could be described by energy transfer. The result of change in hardness was discussed by the reduction of domain size under FWHM analysis and plastic deformation. Moreover, the contamination from each media by EDS could affect surface hardness as the medium is harder than based material.

Residual Stresses in Elastoplastic Bending of Round Bar

Elastoplastic deformation on the presses and high-temperature heating of the steel sheet cause the large residual stresses in the sheet’s and bar’s wall. The technological operations of the obtaining of metal products, their shape and linear dimensions strongly affect on the distribution within the metal and the maximum values of residual stresses. The uneven cooling of various parts of the sheet and bar, obtained by bending, stamping and forging, also leads to the large residual stresses inside the metal. The greatest residual stresses occur in the weld area, where there is a strong heterogeneity of mechanical and physical properties of the metal due to uneven heating and cooling. Below the new analytical method for calculating of the residual stresses of a round steel bar in the elastoplastic bending is obtained. This method takes into account the diameter of the bar, as well as the modulus of elasticity, the yield strength and the hardening modulus of steel’s bar.

Analysis of residual stress in circular cross-section wires after drawing process

Residual stresses arising in the drawing process have a significant impact on the quality of the cold-drawn wire. Knowledge of residual stresses and their distribution makes it possible to predict the behavior of metal products under operating loads and to prevent their possible destruction. In this regard, it is necessary to adjust the main parameters of the drawing process, including the geometry of the die channel. The work is devoted to the study of residual stresses arising from inhomogeneity of plastic deformation depending on the reduction value and the die angle. Computer simulation of wire drawing process by finite element method is performed. The distributions of residual stress tensor components along the wire radius are calculated for different values of reduction and die angle. The analysis of the obtained relations is carried out. The influence of the die angle on the distribution of residual stresses is most noticeable at small reductions. After the maximum values of residual stresses are reached at the reduction values of 35-40%, they noticeable decrease occurs.

Surface layer characteristics of CNT/Al–Mg–Si alloy composites treated by stress peening

To determine the effect of carbon nanotubes (CNTs) on the characteristics of CNT/Al composites treated by stress peening, a 1.5wt% CNT/Al–Mg–Si alloy composite and an Al–Mg–Si alloy were fabricated via flake powder metallurgy process. The evolution of residual stress fields, surface topography, and microhardness of peened layers were explored before and after the peening treatments. The differences in microstructure, including domain size, microstrain, and dislocation density, were determined via Rietveld refinement. After stress peening, the maximum residual stress values of CNT/Al–Mg–Si composite and Al–Mg–Si alloy were improved by 101MPa, 83MPa, respectively, compared with traditional shot peening. Meanwhile, the magnitude of the residual stress of CNT/Al–Mg–Si composite was generally higher than that of Al–Mg–Si alloy. Results also reveal that pre-stress and CNTs addition could improve the compressive residual stress fields treated by stress peening. Nevertheless, in the peened layers, the domain sizes were further refined (12%) and the microstrain was increased by applying prestress and CNTs. The difference in microhardness of peened layers was consistent with the change law of surface layer characteristics.

Influence of heat input and radius to pipe thickness ratio on the residual stresses in circumferential arc welded pipes of API X46 steels

The present work aims to study residual stresses caused by circumferentially welding of two similar API X46 steel pipes by means of finite element modeling. Considering the metallurgical phase transformations and through thermal-mechanical uncoupled analysis, the 3D modeling was carried out by SYSWELD software. Materialistic thermal and mechanical properties of all phases were defined in terms of temperature as well as phase transformation properties. Residual stress was measured through hole-drilling method. The obtained results were used to verify the finite element model. By means of full factorial experiment designing method, effects of heat input and radius to pipe thickness ratio on maximum values of hoop and axial residual stresses were investigated. The effect of each factor was studied in 3 levels and by 9 experiments. Results of statistical analysis revealed that increase in heat input and radius-thickness ratio would lead to higher values of maximum hoop and axial residual stresses. However, interactions of high level of heat input and a low level of radius-thickness ratio increased inter-pass temperature and consequently caused a sudden raise in maximum values of residual stresses.

Liquid phase sintering-based diffusion bonding of Ti(C,N)-based cermet and steel

Sound joint of Ti(C,N)-based cermets and steel is achieved by liquid phase sintering of cermet green compact and steel, in which external pressure and interlayer metals are not required. The bonding process, joint microstructure, and properties are investigated. Liquid phase sintering occurs and typical core/rim structure forms in the cermet during diffusion bonding at 1593 K. Full densification of the cermet can be achieved after bonding for 2 h, the relative density, porosity, and grain size do not vary remarkably with the dwelling time during bonding. Bonding zones are composed of an austenite phase-based layer in the cermet side and a martensite phase-based layer in the steel side. There exists a Ni-enriched layer in the vicinity of cermet/bonding zone interface, which forms due to the outward diffusion of N and inward diffusion of Ti on the surface of cermet. The bonding zone thickness follows a parabolic relationship with the dwelling time. The microhardness of the bonding zones increases from the Ni-enriched layer, austenite layer to the martensite zone. The maximum value of residual stress locates in the bonding zone adjacent to the cermet, and the maximum residual stress value decreases with the dwelling time from the simulation results. Due to the existence of the Ni-enriched ductile bonding layer, a reliable joint can be achieved.

Experimental and Numerical Analysis of Residual Stress in Cast Aluminum Alloy after FSP Process

The effect of FSP modification of cast aluminum alloy AlSi9Mg on residual stress are presented. The numerical results are compared with the residual stresses experimentally measured by the trepanation method. Experimental results show that the residual tensile stresses are higher on the advancing side than on the retreating side. The simulation successfully captures the asymmetric behavior of the residual stress profile, and the predicted maximum residual stress values show relatively good agreement with the experimental values. The simulated profile, however, is more narrow than the experimental profile, yielding a smaller region of residual tensile stresses around the process zone than experimentally observed

Effect of Double Shot Peening on Room-Temperature Notched Fatigue Property of TC4 Titanium Alloy

Single shot peening (SSP) with cast-iron shot and double shot peening (DSP) with cast-iron shot and ceramic shot were applied to investigate the relationship between surface integrity status and the fatigue property of titanium alloy TC4 on the notched specimens (stress concentration coefficient Kt=1.7). Surface roughness, residual stress profile and fatigue curve of the notched specimens were tested using scanning profilometer, XRD residual stress tester and rotating-bending fatigue testing machine, respectively. The results showed that surface roughness decreased 18.3% from Ra 1.09 μm post SSP to Ra 0.89 μm after DSP. Moreover, the position of the maximum value of residual stress migrated out close to the surface and the value of surface residual stress raised 12.6% to-800MPa from SSP. Additionally, the fatigue limit of the notched specimens pose SSP increased 64.7% to 467MPa from 283 MPa of AM, furthermore, edged up by 8% from 432MPa on unpeened smooth samples. It may be concluded that the double shot peening on titanium alloy has, therefore, eliminated the weakness of fatigue property caused by stress concentration.

Using a Coupled Thermal/Material Flow Model to Predict Residual Stress in Friction Stir Processed AlMg9Si

A coupled thermal/material flow model of friction stir processing is developed for friction stir processing of an as-cast AlSi9Mg aluminum alloy. By capturing material flow during processing, an asymmetric temperature distribution is generated with higher processing temperatures on the advancing side than on the retreating side. The temperature distribution from the coupled model is then incorporated into a thermomechanical model to predict the residual stress state after processing. These numerical results are compared with the residual stresses experimentally measured by the trepanation method. Experimental results show that the tensile residual stresses are higher on the advancing side than on the retreating side. The simulation successfully captures the asymmetric behavior of the residual stress profile, and the predicted maximum residual stress values show relatively good agreement with the experimental values. The simulated profile, however, is narrower than the experimental profile, yielding a smaller region of tensile residual stresses around the process zone than experimentally observed.

Laser Shock Processing of Titanium Alloy Blade and FEM Simulation

The aim of this article is to analyze the residual stresses field in a TC4 titanium alloy blade by laser shock processing (LSP).LSP is a new surface processing technology, it uses the laser shock wave to act on the surface of the target and form residual compressive stresses field. The ABAQUS software is applied to simulate the LSP of TC4 titanium alloy blade, and the distributions of the residual stresses field are analysed.After single LSP,the maximum value of residual stress on the surface is 309 MPa.The residual stresses on the surface increase first and then decrease.The residual stresses at the depth continue decreasing with the increase of the depth.After multiple LSP,the maximum value of residual stress on the surface is increased and plastically affected depth is increased.

3D residual stress modelling of welded high strength steel plate-to-plate joints

A numerical investigation on the residual stress distributions near the weld toe of plate-to-plate Y-joints fabricated by using high strength steel (HSS) plate is carried out in this study. A full 3D sequentially coupled thermal–mechanical modelling procedure is employed for residual stress analysis for the HSS plate-to-plate joints. Two specimens respectively fabricated by welding at ambient temperature and at a preheating temperature of 100°C are investigated. The 3D numerical models reveal that while high tensile transverse residual stress, which is perpendicular to the weld, is generated near the weld toe of the joint middle section, proper preheating could significantly reduce the magnitude of the residual stress. In addition, it is found that the welding direction between successive weld pass could also affect the maximum residual stress value near the chord weld toe.

Measurement and Simulation of Residual Stresses of Electron Beam Welding Joint of Pure Aluminum

The effects of electron beam welding on the residual stresses of welded joints of pure aluminum plate 99.60 are studied by through-hole-drilling and blind-hole-drilling method. Meanwhile, based on the thermal elastic-plastic theory, and making use of ANSYS finite element procedure, a three - dimensional finite element model using mobile heat source of temperature and stresses field of electron beam welding in pure aluminum is established. The welding process is simulated by means of the ANSYS software. The results show that the main residual stress is the longitudinal residual stress, the value of the longitudinal residual stress is much larger than the transverse residual stress. But the residual stress in the thickness is rather small. And in the weld center, the maximum value of residual stresses is lower than its yield strength. The simulation results about the welded residual stresses are almost identical with the experimental results by measuring. So the research result is important to science research and engineering application.